AERIAL COMMUNICATIONS INC
8-K, 1998-09-17
RADIOTELEPHONE COMMUNICATIONS
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                                   FORM 8-K


                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549


                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934


 Date of Report (Date of earliest event reported):     September 8, 1998
                                                  -----------------------------


                           AERIAL COMMUNICATIONS, INC.
              ----------------------------------------------------
             (Exact name of registrant as specified in its charter)


        Delaware                    0-28262                 39-1706857
- ----------------------------      ------------          ------------------
(State or other jurisdiction      (Commission            (IRS Employer
     of incorporation)             File Number)         Identification No.)



8410 West Bryn Mawr Avenue, Chicago, Illinois               60631
- ---------------------------------------------             ----------
  (Address of principal executive offices)                (Zip Code)


Registrant's telephone number, including area code: (773) 399-4200


                                 Not Applicable
          ------------------------------------------------------------
          (Former name or former address, if changed since last report)



<PAGE>



Item 5.           Other Events.
                  ------------

                  Pursuant  to a  Purchase  Agreement  dated  June 1,  1998 (the
"Purchase Agreement") by and among Aerial Communications,  Inc. (the "Company"),
Aerial Operating Co., Inc., a wholly-owned  subsidiary of the Company  (formerly
known as APT Operating Company, Inc.) ("AOC"), Telephone and Data Systems, Inc.,
the parent  corporation  of the  Company  ("TDS"),  and Sonera  Ltd.,  a limited
liability  company organized under the laws of Finland (formerly known as Sonera
Corporation)  ("Sonera"),  on  September  8,  1998,  Sonera  purchased  from AOC
2,410,482  shares  of  common  stock  of AOC  (the  "Purchased  Shares")  for an
aggregate purchase price of $200 million, representing a 19.423% equity interest
in AOC. Sonera will have the right under certain  circumstances to exchange each
Purchased Share for 6.72919 Common Shares of Aerial  ("Aerial  Common  Shares"),
subject to adjustment.  Upon the exchange of all of the Purchased Shares at such
exchange rate,  Sonera would own  approximately  an 18.5% equity interest in the
Company,  reflecting a purchase  price  equivalent to  approximately  $12.33 per
Aerial  Common  Share.  The number of Purchased  Shares is subject to adjustment
depending on the future performance of the market price of Aerial Common Shares.
Depending on the stock price, the price paid will range from a low of $12.33 per
equivalent  Aerial share to a high of $16.68 per equivalent Aerial Common Share,
which would represent approximately a 14.3% equity interest in the Company.

                  In connection with the closing of the Purchase Agreement,  the
parties entered into the following  agreements:  (i) an Investment  Agreement by
and between TDS, Aerial, AOC and Sonera, (ii) a Registration Rights Agreement by
and between  Aerial and Sonera,  (iii) a Joint Venture  Agreement by and between
Aerial,  AOC and Sonera  Corporation U.S., and (iv) a Supplemental  Agreement by
and between  Aerial,  AOC and Sonera.  Copies of such  agreements  are  attached
hereto as exhibits and incorporated herein by reference.

                  In addition,  pursuant to the terms of the Purchase Agreement,
at the closing,  (i) a Revolving  Credit  Agreement dated August 1, 1995 between
TDS and Aerial,  pursuant to which  Aerial was  indebted to TDS in the amount of
$665 million, plus accrued interest, was terminated,  and a new Revolving Credit
Agreement between TDS and AOC was substituted, pursuant to which AOC is indebted
to TDS in the same amount,  (ii) Aerial executed a Guaranty of AOC's obligations
to TDS under the new Revolving  Credit  Agreement,  and (iii) the Tax Allocation
Agreement  dated January 1, 1996 between TDS and Aerial was amended and restated
in order to  include  AOC as a party.  Copies of such  agreements  are  attached
hereto as exhibits and incorporated herein by reference.

                  There were no prior material relationships between the Company
or any of the Company's  affiliates,  any director or officer of the Company, or
any  associate of any such director or officer,  on the one hand,  and Sonera on
the other hand.

                  Additional   information   concerning   this   transaction  is
contained in the Purchase  Agreement  which was filed with the Commission by the
Company on Form 8-K on June 16, 1998, and is incorporated herein by reference.

                                      - 1 -

<PAGE>



                                   SIGNATURES


         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the  registrant  has duly  caused  this report to be signed on its behalf by the
undersigned, thereto duly authorized.


                               AERIAL COMMUNICATIONS, INC.
                               (Registrant)


Date:  September 17, 1998     By:   /s/ J. Clarke Smith
                                    --------------------------------------
                                    J. Clarke Smith
                                    Vice President - Finance and Administration,
                                    Chief Financial Officer and Treasurer

















































            SIGNATURE PAGE TO AERIAL FORM 8-K DATED SEPTEMBER 8, 1998



                                      - 2 -

<PAGE>



                                  EXHIBIT INDEX


         Exhibit Number                              Description of Exhibit
         --------------                              ----------------------

             99.1                                    Aerial news  release  dated
                                                     September 8, 1998

             99.2                                    The  Investment   Agreement
                                                     between  Telephone and Data
                                                     Systems,    Inc.,    Aerial
                                                     Communications,       Inc.,
                                                     Aerial  Operating Co., Inc.
                                                     (formerly   APT   Operating
                                                     Company,  Inc.) and  Sonera
                                                     Ltd.    (formerly    Sonera
                                                     Corporation),         dated
                                                     September 8, 1998.

             99.3                                    The   Registration   Rights
                                                     Agreement   between  Aerial
                                                     Communications,   Inc.  and
                                                     Sonera    Ltd.    (formerly
                                                     Sonera Corporation),  dated
                                                     September 8, 1998.

             99.4                                    The Joint Venture Agreement
                                                     between              Aerial
                                                     Communications,       Inc.,
                                                     Aerial  Operating Co., Inc.
                                                     (formerly   APT   Operating
                                                     Company,  Inc.) and  Sonera
                                                     Corporation   U.S.,   dated
                                                     September 8, 1998.

             99.5                                    The Supplemental  Agreement
                                                     between              Aerial
                                                     Communications,       Inc.,
                                                     Aerial  Operating Co., Inc.
                                                     (formerly   APT   Operating
                                                     Company,  Inc.) and  Sonera
                                                     Ltd.    (formerly    Sonera
                                                     Corporation),         dated
                                                     September 8, 1998.

             99.6                                    The     Tax      Allocation
                                                     Agreement between Telephone
                                                     and  Data  Systems,   Inc.,
                                                     Aerial Communications, Inc.
                                                     and Aerial  Operating  Co.,
                                                     Inc.      (formerly     APT
                                                     Operating  Company,  Inc.),
                                                     dated September 8, 1998.

             99.7                                    The    Guaranty     between
                                                     Telephone and Data Systems,
                                                     Inc.       and       Aerial
                                                     Communications, Inc., dated
                                                     August 31, 1998.

             99.8                                    The    Revolving     Credit
                                                     Agreement between Telephone
                                                     and Data Systems,  Inc. and
                                                     Aerial  Operating Co., Inc.
                                                     (formerly   APT   Operating
                                                     Company,    Inc.),    dated
                                                     August 31, 1998.


                                      - 3 -

<PAGE>



             99.9                                    The   Purchase    Agreement
                                                     between  Telephone and Data
                                                     Systems,    Inc.,    Aerial
                                                     Communications,       Inc.,
                                                     Aerial  Operating Co., Inc.
                                                     (formerly   APT   Operating
                                                     Company,  Inc.) and  Sonera
                                                     Ltd.    (formerly    Sonera
                                                     Corporation), dated June 1,
                                                     1998,       is       hereby
                                                     incorporated  by  reference
                                                     to  Exhibit   99.2  to  the
                                                     Company's  Form  8-K  dated
                                                     June 1, 1998.

























                                      - 4 -

<PAGE>



                                                                    EXHIBIT 99.1
NEWS RELEASE
                                                                        Contact:
                                                                 J. Clarke Smith
                                                                  (773) 399 4200
                                                     Aerial Communications, Inc.

                                                               Kaj-Erik Relander
                                                                  +358 2040 5365
                                                              Sonera Corporation

FOR RELEASE: IMMEDIATE

            SONERA LTD., COMPLETES $200 MILLION INVESTMENT IN AERIAL
                              COMMUNICATIONS, INC.

September 8, 1998 Chicago, Illinois - Aerial Communications, Inc. [NASDAQ:AERL],
announced  that Sonera Ltd.  (formerly  Telecom  Finland  Ltd),  one of Europe's
leading wireless telecommunications  operators, today completed its $200-million
investment in Aerial Operating Company, Inc. (AOC) a wholly-owned  subsidiary of
Aerial through which Aerial conducts its PCS business.  Aerial is a leading U.S.
provider of personal  communications  services (PCS).  The transaction  recently
received regulatory approval.

This investment  represents an approximate  19.4% equity ownership in AOC. After
five years,  Sonera's AOC stake  becomes  incrementally  exchangeable  for up to
approximately  18.5% of the  equity of Aerial or in certain  circumstances,  for
cash or equity in Aerial's parent, Telephone and Data Systems, Inc.

Sonera paid the  equivalent  of $12.33 per Aerial  share for the AOC stock.  The
equivalent  price per share and the equity  ownership  percentage are subject to
adjustment  based on Aerial's  20-day average share price during the three years
beginning upon today's  closing.  Depending on the Aerial share price, the price
paid for the AOC stock will range  from a low of $12.33  per  equivalent  Aerial
share for an approximate equivalent 18.5% equity ownership,  to a high of $16.68
per  equivalent   Aerial  share  for  an  approximate  14.3%  equivalent  equity
ownership.

As part of the agreement,  the two companies also formed a strategic partnership
to work  together  in areas  such as new  product  development,  and to  jointly
explore new business opportunities in the U.S. PCS market.


Don Warkentin,  Aerial's President and Chief Executive  Officer,  said "This new
partnership  will benefit  Aerial in several ways,  including the ability to tap
into Sonera's considerable experience and expertise to enhance the business and,
in turn,  improve  shareholder  value.  For example,  Sonera personnel will join
Aerial's staff in key strategic positions, especially in the area of new product
development. Two Sonera executives also will join the Aerial Board of Directors.

With this  transaction,  Aerial also has  secured  the final piece of  financing
originally planned by the Company,  Warkentin said. Aerial will use the proceeds
to fund working capital and to pay down existing debt.


                                       -1-

<PAGE>



Kaj-Erik Relander,  Executive Vice President of Sonera,  said that his company's
investment  in Aerial  fulfills  an  important  part of its global  strategy  to
continue to expand beyond Finland's traditional borders.

Sonera's   growing   international   operations   include   seven   wholly-owned
subsidiaries as well as strategic  investments in more than 20 companies  around
the world. In addition, Sonera has a record of successful experience in wireless
joint ventures in markets like Turkey, Russia and the Middle East.

Sonera is Finland's leading  telecommunications  company, based in Helsinki. The
company has numerous  subsidiaries and affiliate  companies in several different
countries. It is currently state-owned, but the Finnish government has announced
plans for a partial  privatization of the company.  Sonera offers a full line of
telecommunications  services and products, and had sales of U.S. $1.4 billion in
1997.

Aerial, headquartered in Chicago, holds licenses to provide PCS service in areas
covering 27.6 million of the U.S. population. Aerial's markets include Columbus,
Ohio;  Houston,  Minneapolis,  Kansas  City,  Pittsburgh  and  Tampa/Orlando/St.
Petersburg. Aerial is a majority-owned subsidiary of Telephone and Data Systems,
Inc., a $1.5 billion telecommunications company based in Chicago.


Except  for  historical  and  factual   information   contained  herein,   other
information   set  forth  in  this  news  release   represents   forward-looking
statements,  including  all  statements  about  the  Company's  plans,  beliefs,
estimates and expectations.  These statements are based on current estimates and
projections,  which  involve  certain risks and  uncertainties  that could cause
actual  results  to  differ   materially  from  those  in  the   forward-looking
statements.  Important factors that may affect these forward-looking  statements
include, but are not limited to: changes in Delaware law; potential  litigation;
and changes in market conditions. Investors are encouraged to consider these and
other risks and  uncertainties  which are  discussed in  documents  filed by the
Company with the Securities and Exchange Commission.

                                      ####

Aerial is a service mark of Aerial Communications, Inc.












                                       -2-

<PAGE>



                                                                    EXHIBIT 99.2

                                                                  EXECUTION COPY

                              INVESTMENT AGREEMENT


                                      AMONG


                        TELEPHONE AND DATA SYSTEMS, INC.
                             a Delaware corporation,


                          AERIAL COMMUNICATIONS, INC.,
                             a Delaware corporation,


                           AERIAL OPERATING CO., INC.,
                             a Delaware corporation,

                                       AND


                                  SONERA LTD.,
                       a Finnish Limited Liability Company


                          dated as of September 8, 1998




                 
<PAGE>



                                TABLE OF CONTENTS
                                -----------------
                                
                                                                           Page
                                                                           ----

INVESTMENT AGREEMENT......................................................... 1

ARTICLE 1.................................................................... 3
         DEFINITIONS......................................................... 3

ARTICLE 2................................................................... 18
         RELATED EVENTS..................................................... 18
                  2.1      Transactions..................................... 18
                  2.2      Aerial Board of Directors........................ 19
                  2.3      Identity of Directors............................ 20

ARTICLE 3................................................................... 20
         REPRESENTATIONS AND WARRANTIES..................................... 20
                  3.1      Representations and Warranties of TDS............ 21
                  3.2      Representations and Warranties of Aerial......... 25
                  3.3      Representations and Warranties of Sonera......... 28

ARTICLE 4................................................................... 30
         RIGHTS TO PURCHASE ADDITIONAL AOC SHARES........................... 30
                  4.1      Subscription Rights.............................. 30
                  4.2      Three-Year Option................................ 33
                  4.3      Seven-Year Option................................ 35
                  4.4      Effect of Aerial Merger or Distribution.......... 37
                  4.5      AOC Option....................................... 39
                  4.6      Limitations...................................... 41
                  4.7      Termination of Options........................... 41

ARTICLE 5................................................................... 42
         TRANSFER OF AOC SHARES............................................. 42
                  5.1      Restriction on Transfer.......................... 42
                  5.2      Right of First Negotiation....................... 43
                  5.3      Assignment of Rights............................. 46
                  5.4      Issuance of Derivative........................... 47
                  5.5      Transfers Prior to Fifth Anniversary............. 49

ARTICLE 6................................................................... 50
         RESTRICTION ON LIENS............................................... 50

                                      - i -

<PAGE>



ARTICLE 7................................................................... 51
         EQUITY EXCHANGE ELECTION........................................... 51
                  7.1      Exchange of AOC Shares for Aerial Shares......... 51
                  7.2      Exchange Rate.................................... 52
                  7.3      Adjustment of Exchange Rate...................... 52
                  7.4      Surrender of AOC Certificates.................... 61
                  7.5      Issuance of Aerial Certificates.................. 62
                  7.6      Dividends........................................ 63
                  7.7      Redemption of AOC Shares......................... 63
                  7.8      Application...................................... 63
                  7.9      Notice of Adjustment............................. 64
                  7.10     Ownership of Surrendered AOC Shares.............. 65
                  7.11     Termination...................................... 65

ARTICLE 8................................................................... 65
         EQUITY PURCHASE ELECTION........................................... 65

ARTICLE 9................................................................... 67
         RIGHTS TO PURCHASE
                  AERIAL SHARES............................................. 67
                  9.1      Right to Purchase................................ 68
                  9.2      Exercise of Purchase Right....................... 70
                  9.3      Failure to Subscribe............................. 70
                  9.4      Termination of Rights............................ 71
                  9.5      No Other Purchases............................... 71

ARTICLE 10.................................................................. 71
         TRANSFERS OF CONTROL............................................... 71
                  10.1     Restriction on Transfers of Control of Aerial.... 71
                  10.2     Interpretation................................... 74
                  10.3     Spin-off......................................... 75
                  10.4     Termination...................................... 76
                  10.5     Drag-Along Right................................. 76
                  10.6     Tag-Along Right.................................. 77
                  10.7     Effect of Transfer of Control of Sonera.......... 79

ARTICLE 11.................................................................. 80
         CERTAIN COVENANTS OF TDS, AERIAL AND AOC........................... 80

                  11.1     General.......................................... 81
                  11.2     Auditors......................................... 81
                  11.3     Financial and Other Information.................. 81
                  11.4     No Adverse Actions.  ............................ 83

                                     - ii -

<PAGE>



                  11.5     Performance of Intercompany Agreements and 
                           Policies......................................... 83
                  11.6     Reservation of Aerial Shares..................... 85
                  11.7     Intra-Corporate Transactions..................... 86
                  11.8     Performance of Registration Rights Agreement and 
                           Waiver........................................... 87
                  11.9     Operation in Ordinary Course..................... 88

ARTICLE 12.................................................................. 89
         MISCELLANEOUS...................................................... 89
                  12.1   Expenses........................................... 89
                  12.2   Equitable Remedies................................. 89
                  12.3   Notices............................................ 89
                  12.4   Entire Agreement................................... 92
                  12.5   Remedies Cumulative................................ 92
                  12.6   Governing Law...................................... 92
                  12.7   Counterparts.  .................................... 93
                  12.8   Waivers............................................ 93
                  12.9   Successors and Assigns............................. 93
                  12.10  Further Assurances................................. 93
                  12.11  Information for Governmental Filings............... 94
                  12.12  Disclosures........................................ 94
                  12.13  Termination........................................ 95
                  12.14  Disputes........................................... 96
                  12.15  No Claim of Immunity............................... 99
                  12.16  Remedies........................................... 99
                  12.17  Severability....................................... 99













                                     - iii -

<PAGE>



                              INVESTMENT AGREEMENT


                  This  INVESTMENT  AGREEMENT  is made as of  September 8, 1998,
(the  "Agreement")  by and among  TELEPHONE AND DATA  SYSTEMS,  INC., a Delaware
corporation  ("TDS"),  AERIAL  COMMUNICATIONS,   INC.,  a  Delaware  corporation
("Aerial"),  AERIAL  OPERATING CO., INC., a Delaware  corporation  ("AOC"),  and
SONERA  LTD.,  a  limited  liability  company  organized  under  the laws of the
Republic of Finland and formerly known as Sonera Corporation ("Sonera").

                                R E C I T A L S :

                  WHEREAS,  TDS is the owner of more than 80% of the outstanding
capital stock of Aerial;

                  WHEREAS,  Aerial  is  the  owner  of  more  than  80%  of  the
outstanding capital stock of AOC;

                  WHEREAS, Telephone and Data Systems, Inc., an Iowa corporation
and  TDS's  immediate  predecessor  ("TDS  Iowa"),  and one of its  wholly-owned
Subsidiaries,  filed with the Securities and Exchange  Commission a Registration
Statement  on Form S-4, and  Amendments  No. 1 and 2 thereto,  which  included a
Proxy Statement and Prospectus (the "TDS Proxy Statement"),  copies of which, as
amended and supplemented, were furnished to Sonera;




<PAGE>



                  WHEREAS,  the  shareholders  of TDS Iowa approved the proposal
(the "Tracking Stock Proposal") described in the TDS Proxy Statement dated March
24, 1998, as amended by a Proxy Statement Supplement dated April 20, 1998;

                  WHEREAS,  effective May 22, 1998, TDS Iowa was merged with and
into TDS;

                  WHEREAS,  immediately  prior  to the  effective  time  of such
merger,  the  Certificate of  Incorporation  of TDS was amended and restated to,
among other things,  authorize a new class of common stock of TDS ("Aerial Group
Shares")  intended  to  separately   reflect  TDS's  interest  in  the  personal
communications  service business of Aerial and its  Subsidiaries,  including all
assets and liabilities allocated thereto (the "Aerial Group");

                  WHEREAS,  (i) TDS Iowa offered to issue Aerial Group Shares in
exchange for all  outstanding  Aerial Common Shares pursuant to a merger between
Aerial and a  wholly-owned  subsidiary  of TDS,  and (ii) TDS  intends to make a
distribution  of Aerial  Group  Shares,  in the form of a stock  dividend,  with
respect to each outstanding Common and Series A Common Share of TDS;

                  WHEREAS, Sonera has purchased an aggregate of 2,410,482 shares
of AOC's common stock, par value $0.001 per share (the "Purchased Shares"),  for
an aggregate purchase price of $200,000,000 (the "Purchase Price"); and


                                      - 2 -

<PAGE>



                  WHEREAS,  in  connection  with  Sonera  becoming  a  long-term
investor in AOC and/or Aerial Common Shares or Aerial Group Shares,  the parties
desire to regulate certain aspects of their relationship;

                  NOW,  THEREFORE,  in  consideration of the premises and of the
mutual  covenants,  conditions and promises  hereinafter set forth,  the parties
hereby agree as follows:

                                    ARTICLE 1
                                   DEFINITIONS

                  Unless the context otherwise requires, the terms defined below
shall have the meanings specified for all purposes of this Agreement, applicable
to both the  singular  and  plural  forms of any of the  terms so  defined.  For
purposes of this Agreement:

                  "Aerial"  shall  have the  meaning  set forth in the  preamble
hereof.

                  "Aerial  Adjustment Event" shall have the meaning set forth in
Section 4.3(d) hereof.

                  "Aerial  Average"  shall mean (i) for any period of  reference
prior to the earlier to occur of (A) the Aerial Merger, or (B) the Distribution,
the  average  of the daily  means of the high and low sales  prices  for  Aerial
Common Shares, as reported in the applicable composite transactions

                                      - 3 -

<PAGE>



section or national market issues section of The Wall Street  Journal,  and (ii)
for any period of reference thereafter, the Aerial Group Average.

                  "Aerial  Common  Shares"  shall  mean the  class of  shares of
Aerial  designated as Common Shares in its Certificate of  Incorporation,  as in
effect on the date of this Agreement.


                  "Aerial  Common Stock" shall mean (i) Aerial Common Shares and
the  class of  shares of  Aerial  designated  as  Series A Common  Shares in its
Certificate of  Incorporation,  as in effect on the date of this  Agreement,  or
(ii) in the event the Aerial Merger occurs, Aerial Group Shares.

                  "Aerial  Group"  shall  have  the  meaning  set  forth  in the
preamble  hereof and, for purposes of the  definition  of the term  "Competitor"
herein,  shall  also  include  each  alliance  that  owns or  operates  a system
providing B-PCS services in which alliance Aerial or a Subsidiary of Aerial owns
a 20% or greater interest.

                  "Aerial Group Allocation  Procedures" shall mean the manner in
which  Aerial  allocated  among AOC and other  members of the  Aerial  Group all
credits,  fees,  charges and expenses related to, arising under or in connection
with the Intercompany Agreements immediately prior to the date hereof.


                                      - 4 -

<PAGE>



                  "Aerial  Group   Average"   shall  mean,  for  any  period  of
reference,  the average of the daily means of the high and low sales  prices for
Aerial  Group  Shares,  as reported  in the  applicable  composite  transactions
section or national market issues section of The Wall Street Journal.

                  "Aerial  Group Shares" shall have the meaning set forth in the
preamble hereof.

                  "Aerial  Merger" shall mean the  acquisition  by TDS of all of
the Aerial  Common Shares that it does not own,  pursuant to (i) a  transaction,
including the Aerial Merger (as that term is defined in the TDS Proxy Statement)
in which Aerial Group Shares are issued and immediately after which Aerial Group
Shares are listed on a national  securities exchange or authorized for quotation
on the NASDAQ,  or (ii) any other  transaction  upon the  consummation  of which
Aerial  becomes  a  wholly-owned  subsidiary  of TDS  and  TDS  has  issued  and
outstanding  Aerial  Group  Shares  that are  listed  on a  national  securities
exchange or authorized for quotation on the NASDAQ.

                  "Aerial  Negotiation  Notice" shall have the meaning set forth
in Section 10.1(b) hereof.

                  "Aerial  Negotiation  Period" shall have the meaning set forth
in Section 10.1(c) hereof.


                                      - 5 -

<PAGE>



                  "Aerial  Shares"  shall  mean (i) with  respect to any time of
reference  prior to the  earlier to occur of (A) the Aerial  Merger,  or (B) the
Distribution,  Aerial  Common  Shares,  and  (ii)  with  respect  to any time of
reference thereafter, Aerial Group Shares.

                  "Aerial  Transfer  Notice" shall have the meaning set forth in
Section 10.1(b) hereof.

                  "Affiliate" shall mean, with respect to any party hereto,  any
corporation or other  business  entity which,  directly or  indirectly,  through
stock ownership or through any other arrangement,  controls, is controlled by or
is under common  control with,  such party.  The term  "control"  shall mean the
possession, direct or indirect, of the power to direct or cause the direction of
the  management  or policies of such  person,  whether by reason of ownership of
voting stock or other equity interests, by contract or otherwise.

                  "Aggregate  Converted  Percentage"  shall mean the  percentage
obtained by dividing (i) the sum of (A) the number of AOC Shares owned by Sonera
and all of its  Permitted  Affiliate  Transferees,  excluding  any AOC Shares in
respect of which any Sonera  Holder has issued a  Derivative,  (B) the  quotient
obtained by dividing the number of Aerial  Common Shares owned by Sonera and all
of its Permitted Affiliate Transferees by the Exchange Rate Applicable to Aerial
Common  Shares,  and (C) the quotient  obtained by dividing the number of Aerial
Group Shares owned by Sonera and all of its Permitted  Affiliate  Transferees by
the Exchange Rate Applicable to Aerial Group Shares, by (ii) the total number of
AOC Shares outstanding.


                                      - 6 -

<PAGE>



                  "Agreement"  shall have the meaning set forth in the  preamble
hereof.

                  "Anniversary"  shall mean the date  occurring  12 months after
the date of this Agreement and the date occurring each 12 months thereafter.

                  "AOC" shall have the meaning set forth in the preamble hereof.

                  "AOC  Option"  shall  have the  meaning  set forth in  Section
4.5(a) hereof.

                  "AOC  Option  Shares"  shall  have the  meaning  set  forth in
Section 4.5(a) hereof.

                  "AOC Shares" shall mean the class of shares of AOC  designated
as Common Stock in its Certificate of Incorporation, as in effect on the date of
this Agreement.

                  "Authorization"    shall   mean   any   franchise,    license,
authorization,  consent, permit, waiver, approval, qualification or registration
of, with or from the FCC, any state public utility or public service commission,
or  any  other  governmental   authority,   agency  or  instrumentality   having
jurisdiction over the relevant party and matter.

                  "B-PCS services" shall mean broadband personal  communications
services provided in the United States on the following frequency blocks:


                                      - 7 -

<PAGE>



                  Block A 1850-1865 MHZ  paired  with  1930-1945  MHZ  
                  Block B 1870-1885 MHZ paired with  1950-1965 MHZ 
                  Block C 1895-1910 MHZ paired with  1975-1990  MHZ 
                  Block D 1865-1870 MHZ paired with 1945-1950 MHZ 
                  Block E 1885-1890 MHZ paired with  1965-1970 MHZ
                  Block F 1890-1895 MHZ paired with 1970-1975 MHZ

The term "B-PCS services" does not include  narrowband  personal  communications
services,  paging or other Wireless Services not constituting broadband personal
communications services.

                  "Business  Day"  shall  mean any day  other  than a  Saturday,
Sunday,  legal holiday in Chicago,  Illinois,  or other day on which  commercial
banks in Chicago are authorized by law or governmental decree to close.

                  "Cellular  Service" shall mean any service governed by Section
22.99 of the rules of the FCC.

                  "Code"  shall  mean the  Internal  Revenue  Code of  1986,  as
amended.

                  "Competitor"   shall  mean  any  Person   that,   directly  or
indirectly,  operates  or  manages,  or owns a 20% or  greater  interest  in,  a
business engaged in the provision of Wireless  Services if the population within
the geographic areas served by the systems providing Wireless Services owned

                                      - 8 -

<PAGE>



or  operated  by such  Person  (including  its  Affiliates)  that  overlap  with
geographic  areas served by the systems owned or operated by the Aerial Group or
the USCC Group,  as the case may be, is equal to or greater than 2% of the total
population  within the geographic areas of all systems owned and operated by the
Aerial  Group or the USCC Group,  as  applicable;  provided,  however,  that the
geographic areas served by the systems owned or operated by the USCC Group shall
not be considered in determining  whether a Person is a "Competitor" at any time
that USCC ceases to be an Affiliate of Aerial.

                  "Derivative"  shall  have the  meaning  set  forth in  Section
5.4(a) hereof.

                  "Derivative Take-Out Consideration" shall have the meaning set
forth in Section 5.4(c) hereof.

                  "Derivative  Take-Out  Election"  shall have the  meaning  set
forth in Section 5.4(b) hereof.

                  "Disclosures"  shall  have the  meaning  set forth in  Section
12.12(a) hereof.

                  "Disposition  Transaction" shall have the meaning set forth in
Section 10.1(a) hereof.

                  "Distribution"  shall mean the  distribution  by TDS of Aerial
Group Shares, in the form of a stock dividend,  with respect to each outstanding
Common and Series A Common Share of TDS.

                                      - 9 -

<PAGE>



                  "$" shall mean the basic unit of the  lawful  currency  of the
United States of America.

                  "Equity Exchange Election" shall have the meaning set forth in
Section 7.1 hereof.

                  "Equity Purchase Election" shall have the meaning set forth in
Article 8 hereof.

                  "ERISA"  shall have the  meaning  set forth in Section  3.1(i)
hereof.

                  "Event  Notice"  shall have the  meaning  set forth in Section
10.7(a) hereof.

                  "Exchange  Agreement" shall mean the Exchange  Agreement dated
as of April 15, 1996,  between TDS and Aerial (f/k/a American  Portable Telecom,
Inc.).

                  "Exchange  Date"  shall have the  meaning set forth in Section
7.4 hereof.

                  "Exchange  Rate" shall mean,  (i) with  respect to any time of
reference  prior to the  earlier to occur of (A) the Aerial  Merger,  or (B) the
Distribution, the Exchange Rate Applicable to the Aerial Common Shares, and (ii)
with respect to any time of reference  thereafter,  the Exchange Rate Applicable
to Aerial Group Shares.

                  "Exchange Rate  Applicable to Aerial Common Shares" shall have
the meaning set forth in Section 7.2 hereof.

                                     - 10 -

<PAGE>



                  "Exchange  Rate  Applicable to Aerial Group Shares" shall have
the meaning set forth in Section 7.3(b)(iii) hereof.

                  "FCC" shall mean the Federal Communications Commission.

                  "Intercompany  Agreements"  shall  mean  the  Cash  Management
Agreement,  the Employee Benefit Plans Agreement,  the Exchange  Agreement,  the
Insurance Cost Sharing  Agreement,  the  Intercompany  Agreement,  the Revolving
Credit Agreement and the Tax Allocation Agreement between TDS and Aerial, copies
of which  agreements (as amended  through the date hereof)  previously have been
furnished to Sonera, as the same may be amended from time to time.

                  "Intercompany  Policy" shall mean each policy  implemented  by
TDS and Aerial upon the  consummation  of the Aerial Merger to replace a related
Intercompany Agreement,  copies of which policies previously have been furnished
to Sonera and Sonera.

                  "Joint Venture  Agreement" shall have the meaning set forth in
Section 2.1(b) hereof.

                  "Liens" shall have the meaning set forth in Article 6 hereof.

                  "Material  Adverse  Effect" on a Person  shall mean a material
adverse effect on the financial condition, operations or business of such Person
and its  Subsidiaries,  taken as a whole,  or on the  ability of such  Person to
enter into and consummate the transactions contemplated by and

                                     - 11 -

<PAGE>



lawfully to perform its  obligations  under this  Agreement,  the Joint  Venture
Agreement  and the  Registration  Rights  Agreement  in  accordance  with  their
respective terms.

                  "Minimum  Number of AOC  Shares"  shall have the  meaning  set
forth in Article 8 hereof.

                  "Minimum  Option  Prices"  shall have the meaning set forth in
Section 4.3(d) hereof.

                  "NASDAQ"   shall  mean  National   Association  of  Securities
Dealers, Inc., Automated Quotation System.

                  "New  Issue  Closing"  shall  have the  meaning  set  forth in
Section 9.2 hereof.

                  "New Issue Sale  Notice"  shall have the  meaning set forth in
Section 9.1 hereof.

                  "New Issue  Securities"  shall have the  meaning  set forth in
Section 9.1 hereof.

                  "Number of Aerial Group  Shares" shall mean the sum of (i) the
number of Aerial Group Shares held by  shareholders  of TDS, (ii) the "Number of
Aerial Group Shares Issuable with Respect to Retained Interest" (as that term is
defined in the Restated  Certificate) in the Aerial Group, and (iii) the "Number
of Aerial Group Shares Issuable with Respect to Inter-Group Interest" (as that

                                     - 12 -

<PAGE>



term is defined in the  Restated  Certificate)  in the Aerial Group by all other
"Tracking Groups" (as that term is defined in the Restated Certificate), if any.

                  "Option  Closing"  shall have the meaning set forth in Section
4.2(c) hereof.

                  "Permitted  Affiliate  Transferee" shall mean (i) Sonera,  and
(ii) any direct or indirect Subsidiary of Sonera.

                  "Person"  shall  mean  any  general  or  limited  partnership,
corporation,  limited liability company,  joint venture,  trust, business trust,
cooperative,  association,  individual  or other entity,  and heirs,  executors,
administrators, legal representatives, successors and assigns of such person.

                  "Purchase  Agreement" shall mean that certain  agreement dated
June 1, 1998,  pursuant to which AOC agreed to sell to Sonera, and Sonera agreed
to purchase from AOC, the Purchased Shares.

                  "Purchase  Consideration"  shall have the meaning set forth in
Article 8 hereof.

                  "Purchase  Price"  shall  have the  meaning  set  forth in the
preamble hereof.

                  "Purchased  Shares"  shall have the  meaning  set forth in the
preamble hereof.


                                     - 13 -

<PAGE>



                  "Registration  Rights  Agreement"  shall have the  meaning set
forth in Section 2.1(c) hereof.

                  "Restated  Certificate" shall mean the Restated Certificate of
Incorporation  of TDS, which is the surviving entity of the merger with TDS Iowa
described in the TDS Proxy Statement.

                  "Seven-Year  Option"  shall  have  the  meaning  set  forth in
Section 4.3(a) hereof.

                  "Seven-Year Option Shares" shall have the meaning set forth in
Section 4.3(a) hereof.

                  "SMR Service" shall mean any service  governed by Section 90.7
of the rules of the FCC.

                  "Sonera"  shall  have the  meaning  set forth in the  preamble
hereof.

                  "Sonera Holder" shall mean Sonera and each Permitted Affiliate
Transferee of Sonera that acquires AOC Shares.

                  "Sonera  Negotiation  Notice" shall have the meaning set forth
in Section 5.2(a) hereof.

                  "Sonera  Negotiation  Period" shall have the meaning set forth
in Section 5.2(b) hereof.


                                     - 14 -

<PAGE>



                  "Sonera  Transaction  Notice" shall have the meaning set forth
in Section 10.7(a) hereof.

                  "Sonera  Transfer  Notice" shall have the meaning set forth in
Section 5.2(a) hereof.

                  "Subsidiary"  of a Person shall mean a corporation as to which
a majority of the voting power is owned or  controlled  by such  Person,  either
directly  or  indirectly;  but any  such  corporation  shall be  deemed  to be a
Subsidiary of such Person only as long as such ownership or control exists.

                  "Taxes"  shall  mean  all  taxes,  charges,  levies  or  other
assessments  of any kind,  including  income,  gross  receipts,  sales,  use, ad
valorem, franchise, profits, license, withholding,  payroll, employment, excise,
severance,  stamp,  occupation,  premium,  property or windfall  profits  taxes,
customs duties or similar fees,  assessments or charges of any kind  whatsoever,
together with any interest and penalties, additions to tax or additional amounts
imposed by any taxing  authority,  domestic or foreign and any expenses incurred
in connection with the determination,  settlement or litigation of any liability
for any of the foregoing.

                  "Tax Return" shall mean a report,  return or other information
required to be supplied to a taxing authority with respect to Taxes.

                  "TDS" shall have the meaning set forth in the preamble hereof.


                                     - 15 -

<PAGE>



                  "TDS  Adjustment  Event"  shall have the  meaning set forth in
Section 4.4(c) hereof.

                  "TDS Average"  shall mean,  for any period of  reference,  the
average  closing price for TDS Shares,  as reported in the applicable  composite
transactions  section or  national  market  issues  section  of The Wall  Street
Journal.

                  "TDS  Change in Control"  shall be deemed to have  occurred at
such time as (i) any Person  (including  one or more  Affiliates of such Person)
has become the beneficial  owner of 50% or more of the combined voting power (on
matters other than the election of  directors) of all of TDS's then  outstanding
equity  securities,  or (ii) there is consummated any consolidation or merger of
TDS (A) in which TDS is not the surviving corporation,  or (B) pursuant to which
the common stock of TDS is converted into cash, securities or other property, in
each case other than a  consolidation  or merger of TDS in which (1) the holders
of the Series A Common Shares of TDS immediately prior to such  consolidation or
merger have,  directly or indirectly,  30% or more of the combined  voting power
(on  matters  other  than  the  election  of  directors)  of the  common  equity
securities of the surviving corporation  immediately after such consolidation or
merger,  and (2) such voting power is greater than the combined voting power (on
matters other than the election of directors) of the common equity securities of
the surviving corporation immediately after such consolidation or merger held by
any other Person (including one or more Affiliates of such other Person).

                  "TDS Iowa" shall have the  meaning  set forth in the  preamble
hereof.

                                     - 16 -

<PAGE>



                  "TDS  Parties"  shall  have the  meaning  set forth in Section
12.14(b) hereof.

                  "TDS  Shares"  shall  mean  (i)  with  respect  to any time of
reference  prior to the  earlier  to occur of (A) the Aerial  Merger, or (B) the
Distribution,  Common  Shares of TDS,  par value $.01 per  share,  and (ii) with
respect to any time of reference  thereafter,  Aerial Group Shares,  provided in
any case that such  shares  are  traded on a  national  securities  exchange  or
authorized for quotation on the NASDAQ.

                  "Third Party  Transferee"  shall have the meaning set forth in
Section 5.1(b) hereof.

                  "Three-Year  Option"  shall  have  the  meaning  set  forth in
Section 4.2(a) hereof.

                  "Three-Year Option Shares" shall have the meaning set forth in
Section 4.2(a) hereof.

                  "Tracking  Stock Proposal" shall have the meaning set forth in
the preamble hereof.

                  "Transfer"  shall have the meaning set forth in Section 5.1(b)
hereof.

                  "USCC"  shall  mean  United  States  Cellular  Corporation,  a
Delaware corporation and an Affiliate of Aerial.

                  "USCC Group" shall mean USCC and its Subsidiaries.

                                     - 17 -

<PAGE>



                  "U.S.  GAAP" shall mean the United States  Generally  Accepted
Accounting Principles.

                  "Wireless  Services"  shall  mean  B-PCS  services,   Cellular
Service or SMR Service.

                  When a reference is made in this Agreement to a Section,  such
reference shall be to a Section of this Agreement  unless  otherwise  indicated.
Whenever  the  words  "include,"  "includes"  or  "including"  are  used in this
Agreement,   they  shall  be  deemed  to  be  followed  by  the  words  "without
limitation."  The use of a gender  herein shall be deemed to include the neuter,
masculine and feminine genders whenever  necessary or appropriate.  Whenever the
word "herein" or "hereof" is used in this Agreement, it shall be deemed to refer
to this  Agreement  and not to a  particular  Section of this  Agreement  unless
expressly stated otherwise.

                                    ARTICLE 2
                                 RELATED EVENTS

                  2.1      Transactions.  Simultaneously with the execution of 
this Agreement:

                  (a)      AOC is selling the Purchased Shares to Sonera upon 
the terms set forth in the Purchase Agreement;


                                     - 18 -

<PAGE>



                  (b) Aerial and Sonera  Corporation  U.S. are  entering  into a
Joint  Venture  Agreement  in the form of EXHIBIT 1.2  attached to the  Purchase
Agreement (the "Joint Venture Agreement"); and

                  (c) Aerial and Sonera are entering into a Registration  Rights
Agreement  in the form of EXHIBIT 1.3 attached to the  Purchase  Agreement  (the
"Registration Rights Agreement").

                  2.2  Aerial  Board  of  Directors.   Simultaneously  with  the
execution of this Agreement,  TDS and Aerial shall (a) amend Aerial's By-laws to
increase to at least 12 the number of Aerial  directors,  (b) add two  directors
designated by Sonera to the Aerial Board of Directors,  and (c) designate one of
such new  directors a member of the Audit  Committee  of Aerial.  TDS and Aerial
agree that  Sonera's  designees  shall be nominated for election to the Board of
Directors of Aerial by the holders of Aerial Common  Shares,  at the time and in
the manner proper for such nomination,  and TDS agrees to execute a proxy giving
Sonera the power to vote in the  election  of  directors  that  number of Aerial
Common  Shares owned by TDS which,  when added to the Aerial Common Shares owned
by Sonera and its  Affiliates,  will be sufficient to elect such nominees to the
Board of  Directors of Aerial.  Sonera  shall retain the right to designate  two
directors  pursuant to this Section 2.2 so long as (i) the  Aggregate  Converted
Percentage is at least 7.9%, or (ii) if the  Aggregate  Converted  Percentage is
less than 7.9%, so long as Sonera and its Permitted  Affiliate  Transferees have
not  transferred  to any third party any of the  Purchased  Shares or any of the
Aerial  Shares  for  which any such  Purchased  Shares  may have been  exchanged
pursuant  to  Article  7 or 8  hereof.  In the  event  the  Aggregate  Converted
Percentage is less than 7.9% but at least 5.3% and clause (ii) of

                                     - 19 -

<PAGE>



the  immediately  preceding  sentence is  inapplicable,  Sonera shall retain the
right to  designate  one  director to the Board of  Directors  of Aerial,  which
director may or may not, at the discretion of the Aerial Board of Directors,  be
appointed to the Audit Committee of Aerial. In the event the Aggregate Converted
Percentage is less than 5.3% and clause (ii) of the second preceding sentence is
inapplicable, the right of Sonera under this Section 2.2 shall terminate.

                  2.3  Identity  of  Directors.  Sonera  agrees that it will not
designate as its  representative  to Aerial's  Board of Directors any individual
who  is an  officer,  director  or  representative  of  any  Person  that  is in
competition  with Aerial or any of its  Affiliates  in the provision of Wireless
Services to any  significant  extent.  Aerial  agrees that, as long as Sonera is
entitled  to  designate  at  least  one  representative  to  Aerial's  Board  of
Directors,  Aerial  will not  nominate to its Board of  Directors,  and will not
appoint  to the  Board  of  Directors  of AOC,  any  individual  (other  than an
individual whose principal occupation,  at the time of such nomination,  is that
of employee or officer of Aerial or one of its Affiliates, or who is a Person in
control  of Aerial or one of its  Affiliates  or is an  incumbent  on the Aerial
Board of Directors) who is an officer,  director or representative of any Person
that is in competition  with Sonera or any of its Affiliates to any  significant
extent. For purposes of the immediately  preceding sentence,  the term "control"
shall have the  meaning  set forth in the last  sentence  of the  definition  of
"Affiliate" in Article 1 hereof.

                                    ARTICLE 3
                         REPRESENTATIONS AND WARRANTIES


                                     - 20 -
<PAGE>



                  3.1  Representations and Warranties of TDS. TDS represents and
warrants to Sonera,  which  representations  and  warranties  shall  survive the
execution  and  delivery  of  this  Agreement  and  the   consummation   of  the
transactions contemplated hereby, as follows:

                  (a) Due  Organization.  TDS is a corporation duly incorporated
and  validly  existing  under  the laws of the  State of  Delaware.  TDS is duly
qualified to do business and is in good standing in all jurisdictions  where the
conduct  of  its  business  or  the  ownership  of  its  properties  makes  such
qualification necessary, except where the failure to so qualify would not have a
Material Adverse Effect on TDS.

                  (b) Power and Authority; No Violation.  TDS has full power and
authority to execute,  deliver and perform its obligations  under this Agreement
and to consummate the transactions  contemplated  hereby. This Agreement and any
transactions  contemplated  hereby have been duly and validly  authorized by all
necessary  action  on the part of TDS and this  Agreement  constitutes  a legal,
valid and binding  obligation of TDS  enforceable in accordance  with its terms,
except  as  such  enforceability  may  be  limited  by  bankruptcy,  insolvency,
reorganization,  moratorium  or other  similar  laws  affecting  or  relating to
enforcement of creditors' rights generally.  Neither the execution,  delivery or
performance of this Agreement,  nor the  consummation by TDS of the transactions
contemplated hereby will, with or without the giving of notice or the passage of
time, or both, (i) conflict with, violate,  result in a default,  breach or loss
of  rights  (or  give  rise  to  any  right  of  termination,   cancellation  or
acceleration)  under, or result in the creation of any Lien, pursuant to (A) any
provision of the Restated  Certificate or By-laws of TDS, (B) any material note,
bond,

                                     - 21 -

<PAGE>



indenture,  mortgage,  deed  of  trust,  contract,  agreement,  lease  or  other
instrument  or  obligation to which TDS is a party or by which TDS or any of its
property  may be  bound,  or (C) any  law,  order,  judgment,  ordinance,  rule,
regulation or decree to which TDS or any of its property is bound,  or (ii) give
rise to any right of first refusal,  subscription  or similar right with respect
to  any  interest  in,  or  any  properties  or  assets  of,  TDS  or any of its
Subsidiaries.

                  (c)  Legal   Matters.   There  is  no  claim,   legal  action,
counterclaim,  suit,  arbitration,  governmental  investigation  or other legal,
administrative or tax proceeding, nor any order, decree or judgment, in progress
or pending,  or to the knowledge of TDS  threatened,  against or relating to the
right of TDS to execute and deliver this  Agreement  or perform its  obligations
hereunder,  or which could  reasonably  be  expected to have a Material  Adverse
Effect on TDS, nor does TDS know of any basis for the same. There is outstanding
no order, writ, injunction, judgment or decree of any court, governmental agency
or  arbitration  tribunal  which,  individually  or  in  the  aggregate,   could
reasonably  be expected  to have a Material  Adverse  Effect on TDS,  other than
orders or decrees involving the wireless telephone industry in general.

                  (d) Truth and Correctness.  No  representation  or warranty by
TDS in this  Agreement  contains  or will  contain  any  untrue  statement  of a
material fact or omits or will omit to state a material  fact  necessary to make
the statements  contained herein, in light of the circumstances under which such
statements are made, not misleading.


                                     - 22 -

<PAGE>



                  (e)  Compliance  with  Laws.  Except as set  forth on  Exhibit
3.1(e) annexed  hereto,  each of TDS and its  Subsidiaries is in compliance with
all applicable laws,  regulations,  administrative  orders and authorizations of
the United States and States in which they transact their respective  businesses
(including all applicable  rules,  regulations  and  authorizations  of FCC, any
state public  utilities or public  service  commission,  or any other federal or
state governmental agency or instrumentality  exercising jurisdiction over TDS),
and of each municipality,  county or subdivision of any thereof, to which any of
their  respective  businesses  or  any of  their  respective  properties  may be
subject,  the non-compliance  with which would have a Material Adverse Effect on
TDS.

                  (f)  Authorization.  Each of TDS and its  Subsidiaries has (i)
all requisite  Authorizations of the FCC (including all PCS  Authorizations) and
of all state public  utility or public  service  commissions  and (ii) all other
material  Authorizations of governmental  agencies exercising  jurisdiction over
TDS or such Subsidiary,  respectively,  required to carry on its business as now
conducted or as contemplated to be conducted, except for any Authorizations, the
failure of which to obtain would not have a Material Adverse Effect on TDS.

                  (g) Taxes.  TDS and its  Subsidiaries  have  timely  filed all
federal,  state,  county,  local and foreign Tax Returns required to be filed by
them,  and have paid all  Taxes  which  have  become  due  pursuant  thereto  or
otherwise,  other than Taxes the liability for which is being  contested in good
faith  and  appropriate  reserves  for which  have been made in TDS's  financial
statements.  Except to the  extent set forth on  EXHIBIT  4.1(j)  annexed to the
Purchase Agreement or

                                     - 23 -

<PAGE>



appropriately  reserved  for  in  TDS's  financial  statements,   there  are  no
additional assessments or adjustments of Taxes pending or threatened against TDS
or its Subsidiaries for any period.

                  (h) No Material Adverse Change. Since December 31, 1997, there
has not been any event or condition which has caused, or is reasonably likely to
cause,  a Material  Adverse  Effect on TDS, other than as a result of conditions
affecting the U.S. telecommunications industry generally.

                  (i) Employee  Benefit Plans.  All employee benefit or employee
welfare plans  maintained by TDS or any of its  Subsidiaries  and subject to the
Employee Retirement Income Security Act of 1974, as amended ("ERISA"), comply in
all material  respects with the requirements of ERISA, and no such plan which is
subject  to  Part  3 of  Subtitle  B  of  Title  1 of  ERISA  has  incurred  any
"Accumulated  Funding  Deficiency" within the meaning of Section 302 of ERISA or
Section  412 of the  Code,  and  neither  TDS  nor any of its  Subsidiaries  has
incurred any liability on account of such an  "Accumulated  Funding  Deficiency"
with respect to any such employee benefit plan subject to ERISA. No liability to
the  Pension  Benefit  Guaranty  Corporation  established  under  ERISA has been
incurred  with respect to any such plan subject to ERISA and neither TDS nor any
of its  Subsidiaries  has incurred any  liability for any Tax implied by Section
4975 of the Code. As of the most recent  valuation date of any such plan,  there
are no "unfunded benefit  liabilities" within the meaning of Section 4001(a)(18)
of ERISA;  and no "prohibited  transaction"  has occurred  within the meaning of
Section  4975 of the Code or Section 406 of ERISA that would  subject TDS or any
of its Subsidiaries to Tax or penalty.

                                     - 24 -

<PAGE>



                  (j) Compliance with other Instruments.  Neither TDS nor any of
its  Subsidiaries is in violation of any term of (i) any agreement or instrument
related to  indebtedness  for borrowed money or any other material  agreement to
which  it is a party  or by which it is  bound,  or (ii) any  applicable  order,
judgment  or decree of any court,  arbitrator  or  governmental  authority,  the
consequences of which violation, whether individually or in the aggregate, would
result in a Material  Adverse  Effect on TDS.  TDS is not a party to or bound by
any agreement,  instrument or constituent  document  compliance with which could
reasonably be expected to result in a Material Adverse Effect on TDS.

                  (k)  Organization  of  Subsidiaries.  Each  Subsidiary  of TDS
listed on EXHIBIT  3.1(k)  annexed hereto is a corporation or other legal entity
duly  organized and in good standing under the laws of the  jurisdiction  of its
organization  and is duly qualified and has the full power and authority in each
applicable  jurisdiction  to own its  properties  and conduct its  business  and
operations  as  currently  conducted,  except to the extent  that any failure to
qualify would not have a Material Adverse Effect on TDS.

                  (l) Investment  Company Act. TDS is not and will not become as
a result of the  Closing,  an  "investment  company"  within the  meaning of the
Investment Company Act of 1940, as amended.

                  3.2      Representations and Warranties of Aerial.  Aerial and
AOC each represents and warrants to Sonera, which representations and warranties
shall survive the execution and

                                     - 25 -

<PAGE>



delivery of this Agreement and the consummation of the transactions contemplated
hereby, as follows:

                  (a) Due Organization.  Aerial is a corporation duly organized,
validly  existing and in good standing  under the laws of the State of Delaware.
Each of Aerial and its  Subsidiaries  is duly qualified to do business and is in
good  standing in all  jurisdictions  where the  conduct of its  business or the
ownership of its properties makes such qualification necessary, except where the
failure to so qualify would not have a Material Adverse Effect on Aerial.

                  (b) Power and Authority;  No Violation.  Aerial has full power
and  authority  to  execute,  deliver and  perform  its  obligations  under this
Agreement and to consummate the transactions contemplated hereby. This Agreement
and any transactions  contemplated  hereby have been duly and validly authorized
by all necessary  action on the part of Aerial and this Agreement  constitutes a
legal, valid and binding obligation of Aerial enforceable in accordance with its
terms, except as such  enforceability may be limited by bankruptcy,  insolvency,
reorganization,  moratorium  or other  similar  laws  affecting  or  relating to
enforcement of creditors' rights generally.  Neither the execution,  delivery or
performance  of  this  Agreement,   nor  the   consummation  by  Aerial  of  the
transactions  contemplated  hereby will, with or without the giving of notice or
the passage of time, or both, (i) conflict with, violate, result in a default or
breach or loss of rights (or give rise to any right of termination, cancellation
or acceleration)  under, or result in the creation of any Lien,  pursuant to (A)
any provision of the Certificate of Incorporation or By-laws of Aerial,  (B) any
material note, bond, indenture,  mortgage,  deed of trust, contract,  agreement,
lease or other

                                     - 26 -

<PAGE>



instrument or obligation to which Aerial is a party or by which Aerial or any of
its  property  may be  bound  or  affected,  or (C) any  law,  order,  judgment,
ordinance, rule, regulation or decree to which Aerial is a party or by which any
of its  property  is bound,  or (ii)  give  rise to any right of first  refusal,
subscription or similar right with respect to any interest in, or any properties
or assets of, Aerial or any of its Subsidiaries.

                  (c)  Legal   Matters.   There  is  no  claim,   legal  action,
counterclaim,  suit,  arbitration,  governmental  investigation  or other legal,
administrative or tax proceeding,  or any order, decree or judgment, in progress
or pending, or to the knowledge of Aerial threatened, against or relating to the
right of Aerial to execute and deliver this Agreement or perform its obligations
hereunder,  or which could  reasonably  be  expected to have a Material  Adverse
Effect on  Aerial,  nor does  Aerial  know of any  basis for the same.  There is
outstanding  no order,  writ,  injunction,  judgment  or  decree  of any  court,
governmental  agency  or  arbitration  tribunal  which,  individually  or in the
aggregate,  could  reasonably be expected to have a Material  Adverse  Effect on
Aerial,  other than orders or decrees involving the wireless  telephone industry
in general.

                  (d)  Capitalization of Aerial. The authorized capital stock of
Aerial consists of 100,000,000 Common Shares, $1.00 par value; 60,000,000 Series
A Common Shares,  $1.00 par value;  60,000,000 Series B Common Shares, $1.00 par
value; and 10,000,000  shares of Preferred Stock,  $1.00 par value,  issuable in
series.  At July 31, 1998,  there were  outstanding  31,733,362  Common  Shares,
40,000,000  Series A Common  Shares,  and no Series B Common Shares or shares of
Preferred Stock. At that date, TDS was the owner of 19,086,000 Common Shares and
40,000,000

                                     - 27 -

<PAGE>



Series  A  Common  Shares.  The  Series A Common  Shares  are  convertible  on a
share-for-share basis into Aerial Common Shares.

                  (e) Aerial Assets.  Except to the extent set forth on SCHEDULE
3.2(e)  attached  hereto,  all of the material  assets  reflected on the balance
sheets  contained  in the  Operating  Financial  Statements  attached as EXHIBIT
4.1(g) to the  Purchase  Agreement  and used or useful  in  connection  with the
business of operating Aerial services are owned by AOC or its subsidiaries.

                  3.3   Representations   and   Warranties  of  Sonera.   Sonera
represents and warrants to TDS and Aerial, which  representations and warranties
shall survive the execution and delivery of this Agreement and the  consummation
of the transactions contemplated hereby, as follows:

                  (a) Due  Organization.  Sonera is a limited  liability company
duly  organized,  validly  existing and in good  standing  under the laws of the
Republic  of Finland.  Sonera is duly  qualified  to do business  and is in good
standing in all jurisdictions where the conduct of its business or the ownership
of its properties makes such qualification  necessary,  except where the failure
to so qualify would not have a Material Adverse Effect on Sonera.

                  (b) Power and Authority;  No Violation.  Sonera has full power
and  authority  to  execute,  deliver and  perform  its  obligations  under this
Agreement and to consummate the transactions contemplated hereby. This Agreement
and any transactions  contemplated  hereby have been duly and validly authorized
by all necessary action on the part of Sonera and this Agreement

                                     - 28 -

<PAGE>



constitutes  a legal,  valid and binding  obligation of Sonera,  enforceable  in
accordance  with its  terms,  except as such  enforceability  may be  limited by
bankruptcy,  insolvency,  reorganization,   moratorium  or  other  similar  laws
affecting or relating to enforcement of creditors' rights generally. Neither the
execution,  delivery or performance of this Agreement,  nor the  consummation by
Sonera of the transactions  contemplated hereby will, with or without the giving
of notice or the passage of time, or both, conflict with,  violate,  result in a
default or breach or loss of rights  (or give rise to any right of  termination,
cancellation  or  acceleration)  under,  or result in the  creation of any Lien,
pursuant to (A) any provision of the Certificate of  Incorporation or By-laws of
Sonera;  (B) any  material  note,  bond,  indenture,  mortgage,  deed of  trust,
contract,  agreement, lease or other instrument or obligation to which Sonera is
a party or by which Sonera or any of its property may be bound.

                  (c)  Legal   Matters.   There  is  no  claim,   legal  action,
counterclaim,  suit,  arbitration,  governmental  investigation  or other legal,
administrative or tax proceeding, nor any order, decree or judgment, in progress
or pending,  or to the  knowledge of Sonera  threatened,  against or relating to
Sonera's right to execute and deliver this Agreement or perform its  obligations
hereunder,  or which could  reasonably  be  expected to have a Material  Adverse
Effect on  Sonera,  nor does  Sonera  know of any  basis for the same.  There is
outstanding  no order,  writ,  injunction,  judgment  or  decree  of any  court,
governmental  agency  or  arbitration  tribunal  which,  individually  or in the
aggregate,  could  reasonably be expected to have a Material  Adverse  Effect on
Sonera or impair in any material respect the performance of Sonera's obligations
hereunder or the consummation of the  transactions  contemplated  hereby,  other
than orders or decrees involving the wireless telephone industry in general.

                                     - 29 -

<PAGE>



                                    ARTICLE 4
                    RIGHTS TO PURCHASE ADDITIONAL AOC SHARES

                  4.1 Subscription Rights. (a) If, at any time after the date of
this  Agreement,  AOC proposes to issue (or sell from  treasury) AOC Shares,  or
securities  convertible  into or  exchangeable  for AOC Shares,  including  debt
securities  convertible into equity securities of AOC but excluding  non-voting,
non-convertible  preferred stock and debt securities  containing  nominal equity
features,  and excluding AOC Shares  issuable upon conversion of debt securities
into equity  securities  of AOC,  each of Aerial and Sonera shall have the right
(which  right  may be  exercised  in full or in  part) to  subscribe  for and to
purchase that  proportion of each such issuance (or sale from treasury) equal to
the  proportion  of AOC Shares that  Aerial or Sonera,  as the case may be, owns
immediately  before such  issuance  (or sale from  treasury).  The  subscription
rights  granted by the preceding  sentence  shall be  exercisable  by Aerial and
Sonera by  delivering a written  election to subscribe to a specified  number or
amount (in  conformity  with the  preceding  sentence) of the  securities  to be
issued, within such reasonable period of time as may be established by the Board
of Directors of AOC after the giving of written notice of the proposed  issuance
to Aerial and Sonera.  The purchase and sale, if any, of such securities,  shall
take  place at the  offices of AOC on the  twentieth  Business  Day after  AOC's
receipt of the subscription election described in the preceding sentence of this
Section 4.1(a),  or at such other place or on such other date as Aerial,  Sonera
and AOC may agree in writing.  At such closing,  AOC shall deliver  certificates
representing the securities to be purchased, against the payment of the purchase
price  therefor by wire transfer of  immediately  available  funds to an account
designated by AOC at least five Business Days prior to the date of such closing.

                                     - 30 -

<PAGE>



                  (b) As promptly as  practicable  after any sale after the date
of this Agreement (i) by Aerial, of any equity  securities of Aerial,  including
Aerial  Common  Stock,  preferred  stock,  warrants,  options or other rights to
acquire equity  securities and equity  securities  issued upon the conversion of
convertible  debt  securities,  but excluding debt securities  convertible  into
equity securities or debt securities containing nominal equity features, or (ii)
by TDS, after the earlier to occur of the Aerial Merger or the Distribution,  of
any equity  securities of the Aerial Group,  the proceeds of which are allocated
to the Aerial  Group,  including  preferred  stock,  warrants,  options or other
rights to acquire such equity  securities and equity  securities issued upon the
conversion  of  convertible  debt  securities,  but  excluding  debt  securities
convertible into equity securities or debt securities  containing nominal equity
features,  Aerial or TDS, as the case may be,  shall  transfer all cash or other
property  received  in  connection  with such sale to AOC  (indirectly,  through
Aerial,  if TDS is the  transferor)  in exchange for that number of newly issued
AOC Shares equal to the quotient  obtained by dividing the aggregate amount paid
by the purchaser of securities  (without regard to any commissions,  concessions
or discounts paid or allowed or expenses incurred by Aerial or TDS in connection
with such sale) by the product  obtained by  multiplying  the Aerial Average for
the 20 trading  days  ending on the last  trading day prior to the date on which
such securities were sold by the Exchange Rate; provided,  however,  that all of
the proceeds  from the sale of such equity  securities  from April 1 to December
31, 1998,  and during each calendar year  thereafter,  pursuant to stock option,
employee stock purchase, 401(k) or other employee benefit programs maintained by
Aerial or TDS, as the case may be, shall be  accumulated  by Aerial and shall be
transferred to AOC in exchange for AOC Shares as soon as  practicable  after the
end of each such calendar year (and in any event within 90 days  thereafter)  in
accordance with the foregoing provisions of this Section 4.1(b).

                                     - 31 -

<PAGE>



                  (c) In  connection  with any such  issuance  of AOC  Shares to
Aerial  pursuant  to  Section  4.1(b)  hereof,  Sonera  shall  have the right to
subscribe  for and to purchase  all or any portion of that number of  additional
AOC Shares  obtained by subtracting  (i) the total number of AOC Shares owned by
all Sonera  Holders  immediately  prior to such  issuance  from (ii) the product
obtained by multiplying (A) the Sonera Holders' aggregate  percentage  ownership
of AOC Shares immediately prior to such issuance by (B) the quotient obtained by
dividing (I) the sum of the total number of AOC Shares owned  immediately  prior
to such  issuance by all  shareholders  other than the Sonera  Holders,  and the
number of AOC Shares to be issued to Aerial  pursuant to Section  4.1(b) hereof,
by (II) the  aggregate  percentage  ownership of AOC Shares of all  shareholders
other than the Sonera Holders immediately prior to such issuance.  The per share
purchase  price for each AOC Share so  purchased by Sonera shall be equal to the
quotient obtained by dividing the aggregate value of all cash and property to be
transferred  to AOC by Aerial  in  exchange  for the AOC  Shares to be issued to
Aerial by the number of AOC Shares to be issued to Aerial.

                  (d) No less than 30  Business  Days prior to the  transfer  of
cash or property to AOC pursuant to Section 4.1(b)  hereof,  Aerial shall give a
written  notice to Sonera of such transfer  setting forth the date such transfer
will occur,  the aggregate  value of all cash and property to be  transferred by
Aerial to AOC and the  number of AOC  Shares to be issued to  Aerial.  If Sonera
elects to exercise its  subscription  right set forth in Section  4.1(c) hereof,
then  Sonera  shall  give a written  notice to  Aerial  advising  Aerial of such
election  within ten Business  Days after the date upon which Aerial gave notice
to Sonera pursuant to the immediately preceding sentence.  The purchase and sale
of such AOC Shares  pursuant to Section  4.1(b)  hereof  shall take place at the
offices of AOC on the date

                                     - 32 -

<PAGE>



set  forth in the  notice  from  Aerial to Sonera  given  pursuant  to the first
sentence of this Section 4.1(d), or at such other place or on such other date as
Aerial and Sonera  may agree in  writing.  At such  closing,  AOC shall  deliver
certificates  representing  the number of AOC Shares to be purchased  (i) in the
case of Aerial,  against transfer to AOC of the cash or property as set forth in
Section 4.1(b) hereof and (ii) in the case of Sonera (to Sonera or any Permitted
Affiliate  Transferee  designated  by Sonera),  against  payment of the purchase
price  therefor by wire transfer of  immediately  available  funds to an account
designated by AOC at least five Business Days prior to such closing.

                  4.2  Three-Year  Option.  (a) In addition to the  subscription
rights  referred to in Section 4.1 hereof,  Sonera shall have the right (but not
the  obligation),  for a period  commencing on the date hereof and ending on the
third Anniversary (the "Three-Year  Option") to purchase from AOC, and AOC shall
issue,  sell and deliver to Sonera,  89,518  additional  AOC Shares (the "Three-
Year Option Shares").

                  (b) The purchase price for the Three-Year  Option Shares shall
be an amount  equal to the  product of (i) the  product of (A) the number of AOC
Shares with  respect to which such option is  exercised,  multiplied  by (B) the
Exchange Rate,  multiplied by (ii) the greater of (A) 145% of the Aerial Average
for the 20  consecutive  trading day period ending on the last trading day prior
to the date on which AOC receives Sonera's notice exercising such option, or (B)
$12.33. The Three-Year Option shall be exercisable,  in whole or in part, at any
time prior to the third such Anniversary, by delivering a written notice of such
exercise to AOC stating the number of AOC Shares to be

                                     - 33 -

<PAGE>



purchased,  which notice shall  constitute a binding  commitment  on the part of
Sonera to purchase  such number of  Three-Year  Option Shares upon the terms set
forth herein.

                  (c) The purchase and sale of the Three-Year  Option Shares (an
"Option  Closing"),  if any,  shall  take  place  at the  offices  of AOC on the
twentieth  Business Day after AOC's  receipt of the notice  described in Section
4.2(b)  hereof,  or at such other  place or on such other date as AOC and Sonera
may agree in writing. At the Option Closing, AOC shall deliver to Sonera (or any
Permitted Affiliate Transferee  designated by Sonera) certificates  representing
the number of AOC Shares to be purchased,  against payment of the purchase price
therefor  by  wire  transfer  of  immediately  available  funds  to  an  account
designated  by AOC at least five  Business Days prior to the date of such Option
Closing.

                  (d) The  number  of AOC  Shares  with  respect  to  which  the
Three-Year Option may be exercised shall be increased to the extent necessary to
preserve  the right of Sonera to  increase  the  number of AOC  Shares  owned by
Sonera and its Permitted  Affiliate  Transferees to 20% of the total outstanding
AOC Shares by exercising  the  Three-Year  Option in full if: (i) additional AOC
Shares have been issued to any Person other than Sonera and Sonera has exercised
in full the  subscription  rights provided for in Section 4.1 of this Agreement;
or (ii) any of the Purchased Shares are canceled  pursuant to Section 2.3 of the
Purchase  Agreement and, if additional AOC Shares have previously been issued to
Aerial,  Sonera has exercised in full the  subscription  rights  provided for in
Section 4.1 of this Agreement.


                                     - 34 -

<PAGE>



                  4.3  Seven-Year  Option.  (a) In addition to the  subscription
rights  referred to in Section 4.1 hereof,  and the  Three-Year  Option,  Sonera
shall  have  the  right  (but  not  the  obligation),  for a  period  commencing
immediately after the third Anniversary and ending on the tenth Anniversary (the
"Seven-Year  Option") to  purchase  from AOC,  and AOC shall  issue,  sell,  and
deliver  to  Sonera,  that  number of  additional  AOC  Shares  equal to (i) the
quotient  obtained by dividing the aggregate  number of  outstanding  AOC Shares
owned by Persons other than Sonera and its Permitted  Affiliate  Transferees  by
 .8,  minus  (ii) the  total  number  of  outstanding  AOC  Shares,  in each case
determined  immediately  prior to the  exercise of such option (the  "Seven-Year
Option Shares").

                  (b) The purchase price for the Seven-Year  Option Shares shall
be (i) for any  Seven-Year  Option Shares  acquired after the third and prior to
the seventh  Anniversary,  an amount  equal to the product of (A) the product of
(I) the number of AOC Shares  with  respect to which such  option is  exercised,
multiplied by (II) the Exchange Rate,  multiplied by (B) the greater of (I) 130%
of the Aerial  Average for the 20  consecutive  trading day period ending on the
last  trading  day  prior to the  date on which  AOC  receives  Sonera's  notice
exercising  such option,  or (II)  $20.00,  and (ii) for any  Seven-Year  Option
Shares acquired after the seventh and prior to the tenth Anniversary,  an amount
equal to the  product of (A) the  product  of (I) the number of AOC Shares  with
respect to which such option is exercised, multiplied by (II) the Exchange Rate,
multiplied  by (B) the  greater  of (I) 130% of the  Aerial  Average  for the 20
consecutive  trading day period ending on the last trading day prior to the date
on which AOC receives  Sonera's notice  exercising such option,  or (II) $30.00.
The  Seven-Year  Option shall be  exercisable,  in whole or in part, at any time
after the third

                                     - 35 -

<PAGE>



and prior to the  tenth  Anniversary,  by  delivering  a written  notice of such
exercise to AOC stating the number of AOC Shares to be  purchased,  which notice
shall  constitute a binding  commitment  on the part of Sonera to purchase  such
number of Seven-Year Option Shares upon the terms set forth herein.

                  (c) The purchase and sale of the Seven-Year  Option Shares, if
any,  shall  take  place  at an  Option  Closing  at the  offices  of AOC on the
twentieth  Business Day after AOC's  receipt of the notice  described in Section
4.3(b)  hereof,  or at such other  place or on such other date as AOC and Sonera
may agree in writing.  At such Option  Closing,  AOC shall deliver to Sonera (or
any  Permitted   Affiliate   Transferee   designated  by  Sonera)   certificates
representing  the number of AOC Shares to be  purchased,  against the payment of
the purchase price therefor by wire transfer of immediately  available  funds to
an account  designated  by AOC at least five  Business Days prior to the date of
such Option Closing.

                  (d) In the event  that,  at any time after the date hereof and
prior to the earlier to occur of the Aerial Merger and the Distribution,  Aerial
shall  effect any  transaction,  including  (i) the payment of a dividend on the
outstanding  Aerial Common Shares in the form of Aerial  Common  Shares,  (ii) a
subdivision of the outstanding Aerial Common Shares into a larger number of such
Aerial Common  Shares,  (iii) a  combination  of the  outstanding  Aerial Common
Shares  into a  smaller  number  of such  Aerial  Common  Shares,  or  (iv)  any
reorganization  or   reclassification  of  the  Aerial  Common  Shares,  or  any
consolidation  or  merger  with  another  corporation,  or  the  sale  of all or
substantially all of its assets to another  corporation,  in such a way that the
holders of the outstanding

                                     - 36 -

<PAGE>



Aerial  Common  Shares  shall be  entitled to receive  (either  directly or upon
subsequent  liquidation) stock,  securities or other property with respect to or
in exchange for such Aerial Common Shares (any such  transaction  or event being
referred to as an "Aerial Adjustment  Event"),  then the minimum purchase prices
for the Three-Year Option Shares referred to in Section 4.2(b)(ii)(B) hereof and
for the Seven-Year  Option Shares  referred to in Section  4.3(b)(i)(B)(II)  and
(b)(ii)(B)(II)  hereof (the "Minimum  Option  Prices") shall be  proportionately
adjusted to reflect such Aerial Adjustment Event.

                  4.4 Effect of Aerial Merger or Distribution.  (a) In the event
that the Aerial Merger shall occur at any time after the date of this  Agreement
and prior to the  Distribution,  the Minimum  Option Prices shall be adjusted by
dividing  such prices by a fraction,  the numerator of which shall be the Number
of Aerial Group Shares,  determined immediately after the Aerial Merger, and the
denominator  of which  shall be the  number of shares  of  Aerial  Common  Stock
outstanding immediately prior to the Aerial Merger.

                  (b) In the event that the Distribution shall occur at any time
after the date of this  Agreement  and prior to the date of the  Aerial  Merger,
then:

                      (i) the  Minimum  Option  Prices  shall  be  adjusted  by 
dividing such prices by a fraction, the numerator of which shall be the quotient
obtained  by  dividing  the Number of Aerial  Group  Shares by TDS's  percentage
ownership of Aerial Common Stock, in each case determined

                                     - 37 -

<PAGE>



immediately  after the  Distribution,  and the denominator of which shall be the
total number of shares of Aerial Common Stock  outstanding  immediately prior to
such Distribution; and

                           (ii)  in the  event  that  the  Aerial  Merger  shall
thereafter occur, the Minimum Option  Prices  shall be  adjusted by  dividing  
such prices by a fraction,  the numerator of which is the Number of Aerial Group
Shares, determined  immediately  after  the  Aerial Merger, and the denominator 
of which is the quotient obtained by dividing the Number of Aerial Group Shares 
by TDS's  percentage  ownership of   Aerial  Common  Stock,  determined  in each
case  immediately  before the Aerial Merger.

                  (c) In the event that,  at any time after the earlier to occur
of the Aerial  Merger and the  Distribution,  TDS shall effect any  transaction,
including (i) a combination  of the Aerial Group Shares into a smaller number of
such Aerial Group Shares,  (ii) a subdivision  of the Aerial Group Shares into a
larger  number of such  Aerial  Group  Shares,  or (iii) any  reorganization  or
reclassification of the Aerial Group Shares, or the sale of all or substantially
all of the assets of the Aerial Group to another corporation, in such a way that
the holders of Aerial Group Shares shall be entitled to receive (either directly
or upon subsequent liquidation) stock, securities or other property with respect
to or in exchange for such Aerial Group  Shares (any such  transaction  or event
being referred to as a "TDS Adjustment  Event"),  then the Minimum Option Prices
shall be proportionately adjusted to reflect such TDS Adjustment Event.


                                     - 38 -

<PAGE>



                  4.5 AOC  Option.  (a) If,  at any time  after the date of this
Agreement and prior to the tenth Anniversary, (i) Sonera shall have the right to
purchase any additional  Aerial Shares pursuant to Section 9.1 hereof,  and (ii)
the  Three-Year  Option or the Seven-Year  Option,  as the case may be, shall at
such time also be  exercisable,  then, in lieu of purchasing some or all of such
additional  Aerial Shares pursuant to Section 9.1 hereof,  Sonera shall have the
right to apply all or any portion of the purchase  price  otherwise  required to
purchase  Aerial  Shares  pursuant  to Section 9.1  hereof,  to the  purchase of
additional  AOC Shares (the "AOC  Option")  pursuant to this  Section  4.5.  The
number of additional AOC Shares ("AOC Option Shares")  issuable  pursuant to the
exercise of the AOC Option  shall be equal to that number (or any lesser  number
elected by Sonera) of AOC Shares that  Sonera  would at such time have the right
to purchase upon the exercise of the Three-Year Option or the Seven-Year Option,
as the case may be.

                  (b) The purchase  price for the AOC Option  Shares shall be an
amount  equal to the  product of (i) the product of (A) the number of AOC Shares
with respect to which such option is  exercised,  multiplied by (B) the Exchange
Rate,  multiplied by (ii)(A) the Aerial  Average  referred to in Section  9.1(a)
hereof, or (B) the Aerial Group Average referred to in Section 9.1(b) hereof, as
the case may be. Except as otherwise  provided in paragraph  (d) below,  the AOC
Option  shall  be  exercisable  no  later  than the  time  Sonera  delivers  the
applicable  written notice  referred to in Section 9.2 hereof.  The purchase and
sale of the AOC  Option  Shares,  if any,  shall  take  place  at the New  Issue
Closing.  At such  closing,  AOC shall  deliver  certificates  to Sonera (or any
Permitted Affiliate Transferee  designated by Sonera) representing the number of
AOC Shares to be purchased, against

                                     - 39 -

<PAGE>



the  payment of the  purchase  price  therefor by wire  transfer of  immediately
available  funds to an account  designated by Aerial at least five Business Days
prior to the date of such closing.

                  (c) In the  event  that  Sonera  elects  to  exercise  the AOC
Option, the number of Aerial Shares that Sonera shall have the right to purchase
pursuant to Section 9.1 hereof  shall be reduced by the number of Aerial  Shares
obtained by dividing  (i) the  aggregate  amount  payable by Sonera  pursuant to
Section  4.5(b) hereof,  by (ii) (A) the Aerial  Average  referred to in Section
9.1(a)  hereof,  or (B) the Aerial Group Average  referred to in Section  9.1(b)
hereof, as the case may be.


                  (d) In the event that Sonera shall have  purchased  any Aerial
Shares  pursuant to Section 9.1 of this Agreement at any time prior to the third
Anniversary then,  notwithstanding  Sections 4.5(b) and (c) above,  Sonera shall
have the  right,  at any time  prior to the third  Anniversary,  (i) to  require
Aerial (or TDS,  in the case of Aerial  Group  Shares) to redeem  some or all of
such Aerial Shares,  and (ii)  simultaneously to reinvest all (but not less than
all) of the proceeds of such redemption in AOC Shares;  provided,  however, that
the number of additional  AOC Shares  issuable  pursuant to this Section  4.5(d)
shall not exceed the number of AOC Shares  that  Sonera  would at such time have
the right to purchase upon the exercise of the Three-Year  Option. The per share
redemption price for any Aerial Shares to be redeemed by Aerial pursuant to this
Section  4.5(d)  shall be equal to the Aerial  Average  for the 20 trading  days
ending on the last  trading day prior to the date of  Sonera's  notice to Aerial
requiring such redemption. The per share purchase price for any AOC Shares to be
issued to Sonera pursuant to this Section 4.5(d) shall be an amount equal to the
product

                                     - 40 -

<PAGE>



of (A) the then  applicable  Exchange Rate  multiplied by (B) the Aerial Average
referred to in the preceding  sentence.  The redemption of any Aerial Shares and
the simultaneous  purchase and sale of the  corresponding AOC Shares pursuant to
this Section  4.5(d) shall take place at the offices of Aerial on the  twentieth
Business Day after Aerial's  receipt of Sonera's notice  exercising the right to
require such  redemption  and purchase,  or at such other place or on such other
date as Aerial and Sonera may agree in writing.  At such  closing,  Sonera shall
deliver  certificates  representing  the securities to be redeemed,  against the
payment of the  purchase  price  therefor,  and AOC shall  deliver  certificates
representing the securities to be purchased and sold to Sonera (or any Permitted
Affiliate Transferee designated by Sonera),  against the payment of the purchase
price therefor.

                  4.6  Limitations.  Notwithstanding  the provisions of Sections
4.1  through  4.5  hereof,  (a) the  rights to  purchase  additional  AOC Shares
provided  therein  shall not be available to Sonera to the extent that Sonera is
unable to  subscribe  for or own such  additional  AOC Shares as a result of its
inability to satisfy any  applicable  legal or regulatory  requirement  for such
subscription or ownership,  and (b) except as otherwise  permitted by Article 10
hereof,  in no event  shall  the  Sonera  Holders  have the right at any time to
purchase or own more than 20% of the aggregate number of outstanding AOC Shares.

                  4.7 Termination of Options.  The right to purchase  additional
AOC Shares pursuant to the Three-Year  Option, the Seven-Year Option, or the AOC
Option shall terminate in the event that any Sonera Holder (a) fails to exercise
any  subscription  right that it may have  pursuant to Section  4.1 hereof,  (b)
issues a Derivative pursuant to Section 5.4 or Section 5.5 hereof, or (c)

                                     - 41 -

<PAGE>



Transfers  any AOC Shares (or any of the Aerial Shares for which such AOC Shares
may be exchanged) to a Third Party Transferee.

                                    ARTICLE 5
                             TRANSFER OF AOC SHARES

                  5.1  Restriction  on Transfer.  (a) A Sonera Holder shall have
the  unrestricted  right to Transfer its AOC Shares to any  Permitted  Affiliate
Transferee; provided (i) the transferee of such AOC Shares agrees to be bound by
the terms and provisions of this Agreement applicable to the transferring Sonera
Holder, and (ii) all necessary approvals have been obtained from the FCC and any
other regulatory agency.

                  (b)  Except  as  otherwise  expressly  provided  for  in  this
Agreement,  no Sonera Holder shall sell,  assign or otherwise  dispose of any of
its AOC Shares,  directly or  indirectly,  by  operation  of law or otherwise (a
"Transfer"),  and no  attempted  Transfer  to any Person  other than a Permitted
Affiliate Transferee (a "Third Party Transferee") shall be valid unless (i) such
Transfer complies with the provisions of this Article 5 and Section 10.5 hereof,
(ii) the Third Party  Transferee  agrees to be bound by the terms and provisions
of this  Agreement  applicable  to the  transferring  Sonera  Holder  (including
Section 10.5 hereof),  and (iii) all necessary approvals have been obtained from
the FCC and any other regulatory agency.


                                     - 42 -

<PAGE>



                  (c) Prior to the fifth  Anniversary,  and except as  otherwise
provided in Section 5.5 hereof,  no Sonera Holder shall  Transfer any AOC Shares
to any Person  other than a  Permitted  Affiliate  Transferee  without the prior
written  consent of TDS and Aerial,  which consent may be withheld by either TDS
or Aerial in its sole discretion.

                  5.2   Right  of  First   Negotiation.   (a)  After  the  fifth
Anniversary,  a Sonera  Holder  desiring to  Transfer  any AOC Shares to a Third
Party Transferee without the prior written consent of TDS and Aerial shall first
give  written  notice to Aerial of its desire to effect such a  Transfer,  which
notice  shall set forth the number of AOC Shares  that the  transferring  Sonera
Holder  desires to Transfer  and refer to this  Section 5.2 (a "Sonera  Transfer
Notice").  Aerial shall have a period of ten  Business  Days from its receipt of
the Sonera Transfer Notice within which to give such transferring  Sonera Holder
a written  notice that Aerial desires to invoke the provisions of Section 5.2(b)
hereof,  (the  "Sonera  Negotiation  Notice").  If Aerial fails to timely give a
Sonera Negotiation Notice or comply with any of the provisions of Section 5.2(b)
hereof, then the transferring Sonera Holder may Transfer such AOC Shares to such
Third  Party  Transferee,   provided  such  Third  Party  Transferee  is  not  a
Competitor,  and may assign  certain of its rights under this  Agreement to such
Third Party Transferee in accordance with Section 5.3 hereof.

                  (b) If Aerial timely gives a Sonera  Negotiation Notice to the
transferring  Sonera Holder pursuant to Section 5.2(a) hereof, then Aerial shall
have the  exclusive  right to negotiate  with such  transferring  Sonera  Holder
regarding  the  possible  acquisition  by Aerial of such AOC Shares for a period
(the "Sonera  Negotiation  Period")  beginning on the date of the receipt by the
transferring

                                     - 43 -

<PAGE>



Sonera  Holder of the Sonera  Negotiation  Notice  and ending on the  earlier to
occur of (i) the date upon which the transferring Sonera Holder and Aerial reach
agreement on the terms of a Transfer of such AOC Shares to Aerial, (ii) the date
upon  which  the  transferring  Sonera  Holder  and  Aerial  agree  that no such
agreement can be reached,  or (iii) 60 days after the commencement of the Sonera
Negotiation  Period.  During the Sonera  Negotiation  Period,  the  transferring
Sonera Holder and Aerial shall negotiate in good faith to reach agreement on the
terms of a Transfer of such AOC Shares from the  transferring  Sonera  Holder to
Aerial.  If the  parties  reach such  agreement  during  the Sonera  Negotiation
Period,  then  the  parties  shall  promptly  prepare  and  file  all  necessary
applications with the FCC and any other applicable  regulatory  agencies and the
closing of the  Transfer of such AOC Shares shall occur within 30 days after the
receipt of all necessary FCC and other regulatory  approvals.  In the event that
the parties do not reach such agreement  during the Sonera  Negotiation  Period,
then Aerial shall give to the  transferring  Sonera  Holder a written  notice of
Aerial's final bid to acquire such AOC Shares (in whatever form Aerial  desires)
on or before the last day of the Sonera Negotiation Period,  which final bid the
transferring Sonera Holder shall have the right to accept (A) for a period of 30
days after its receipt thereof,  during which 30-day period such final bid shall
be irrevocable, and (B) for a period of an additional 60 days thereafter, during
which  additional  60-day  period such final bid shall be revocable by Aerial at
any  time  prior  to  Aerial's  receipt  of  the  transferring  Sonera  Holder's
acceptance of such final bid.

                  (c) In the event that the  transferring  Sonera Holder neither
reaches  agreement with Aerial to Transfer such AOC Shares to Aerial nor accepts
Aerial's  final bid pursuant to Section  5.2(b)  hereof,  then the  transferring
Sonera Holder shall be permitted to Transfer such AOC Shares

                                     - 44 -

<PAGE>



to a Third Party Transferee that is not a Competitor; provided, however, that in
no event  shall  the  transferring  Sonera  Holder  Transfer,  or enter  into an
agreement to Transfer,  such AOC Shares to a Third Party  Transferee  unless (i)
the  transferring  Sonera Holder has  negotiated in good faith during the Sonera
Negotiation Period to effect a Transfer of such AOC Shares to Aerial pursuant to
Section 5.2(b)  hereof,  and (ii) the  transferring  Sonera Holder enters into a
binding  agreement  within  180  days  after  the  termination  of  such  Sonera
Negotiation  Period to Transfer such AOC Shares to a Third Party Transferee at a
price higher than the price offered to the transferring  Sonera Holder by Aerial
in its final bid.

                  (d) For  purposes  of this  Section  5.2,  if the  price  in a
binding  agreement to consummate a Transfer,  or in Aerial's final bid, is to be
paid in  something  other  than  money  in a lump sum at the  closing,  then the
transferring  Sonera  Holder  and Aerial  shall use their best  efforts to reach
agreement as to an  equivalent in monetary  terms,  which shall  constitute  the
price for the purposes of Section  5.2(c)(ii).  If such an  agreement  cannot be
reached  within 15 days after the  transferring  Sonera Holder (in the case of a
final  bid) or  Aerial  (in the case of a  binding  agreement  to  consummate  a
Transfer) receives written notice of the price offered, such equivalent shall be
determined  by an  appraiser,  agreed upon within ten days after the end of such
15-day  period (and paid equally) by the  transferring  Sonera Holder and Aerial
or, if they cannot agree upon an  appraiser,  by three  appraisers,  one of whom
shall be  chosen  within  20 days  after  the end of such  15-day  period by the
transferring Sonera Holder (and paid by the transferring Sonera Holder),  one of
whom shall be chosen within the same period (and paid) by Aerial,  and the third
of whom shall be chosen by the first two so chosen within an additional ten days
and paid equally by the transferring Sonera Holder

                                     - 45 -

<PAGE>



and Aerial. The decision of the agreed-upon  appraiser or, as the case may be, a
majority of the three appraisers, shall be made within 45 days after he or they,
as the  case  may be,  are  chosen  and  shall be  final  and  binding  upon the
transferring  Sonera  Holder and Aerial.  All time periods  specified in Section
5.2(a)  through (c) shall be extended by the length of time  necessary  for such
appraiser(s)  to be  chosen  and for such  appraisal  to be made (if it  becomes
necessary).

                  5.3  Assignment  of Rights.  In the event that a Sonera Holder
has  obtained  the  consent of TDS and Aerial  under  Section  5.1(c)  hereof or
complied  with  Section  5.2  hereof  and  effects a  Transfer  of AOC Shares in
compliance  with Section  5.1(b)(or  pursuant to Section 10.7) hereof to a Third
Party Transferee:

                  (a) the  Three-Year  Option,  the Seven-Year  Option,  the AOC
Option,  the Equity  Purchase  Election,  the right to  purchase  Aerial  Shares
pursuant to Article 9 hereof,  Sonera's right of first negotiation under Section
10.1 hereof and the right to issue a  Derivative  pursuant to Section 5.4 hereof
shall terminate and shall not be assignable to any Third Party Transferee;

                  (b) the right of Sonera to designate  one or two  directors of
Aerial  pursuant  to  Section  2.2  hereof may be  assigned  to any Third  Party
Transferee who acquires at least 964,193 or 1,928,386 AOC Shares  (appropriately
adjusted to reflect any stock dividend, subdivision or combination affecting AOC
Shares), respectively;


                                     - 46 -

<PAGE>



                  (c) the Equity  Exchange  Election  provided  for in Article 7
hereof may be  assigned  to any Third  Party  Transferee  who  acquires at least
964,193  AOC  Shares  (appropriately  adjusted  to reflect  any stock  dividend,
subdivision or combination  affecting AOC Shares);  provided,  however,  that no
such Third Party  Transferee  shall  exercise  such  election  after the twelfth
Anniversary;

                  (d) Aerial agrees that it will enter into an agreement  with a
Third Party  Transferee who acquires at least 964,193 AOC Shares  (appropriately
adjusted to reflect any stock dividend, subdivision or combination affecting AOC
Shares)  to provide  such  transferee  with  registration  rights  substantially
identical to those provided to Sonera and its Affiliates  under the Registration
Rights Agreement; and

                  (e) all of the  AOC  Shares  transferred  to any  Third  Party
Transferee will remain subject to the provisions of Section 10.5 hereof.

         5.4 Issuance of Derivative. (a) At any time after the fifth Anniversary
and prior to the tenth  Anniversary,  each Sonera  Holder  shall have the right,
upon 90 days'  written  notice to  Aerial,  to issue a  security  which  becomes
exchangeable,  after the tenth Anniversary,  for AOC Shares owned by such Sonera
Holder (a  "Derivative"),  and to assign to the purchaser of such Derivative the
right to  exercise  the  Equity  Purchase  Election  at any time after the tenth
Anniversary.  Any Derivative  issued by a Sonera Holder pursuant to this Section
5.4(a) shall be issued  expressly  subject to the provisions of Sections  5.4(b)
and (c), 8(d) and 10.5 hereof.

                                     - 47 -

<PAGE>



                  (b) In the event  that a Sonera  Holder  issues a  Derivative,
(including a Derivative  issued  pursuant to Section  5.5(a) hereof) such Sonera
Holder's rights to exchange the AOC Shares with respect to which such Derivative
is issued for Aerial  Shares,  pursuant to the  provisions  of Article 7 of this
Agreement, shall terminate and, at any time after the tenth Anniversary,  Aerial
shall have the right,  upon written notice to Sonera,  to repurchase all but not
less than all of the AOC Shares  represented by such Derivative (the "Derivative
Take-Out Election").

                  (c)  In  the  event  Aerial  makes  the  Derivative   Take-Out
Election,  each AOC Share subject to such Derivative  shall be exchanged for, at
Aerial's option,  (i) that number of Aerial Shares equal to the product obtained
by multiplying  the number of AOC Shares to be so purchased by the Exchange Rate
provided for in Section 7.2 hereof, (ii) that number of TDS Shares determined by
dividing  the TDS Average for the 20 trading days ending on the last trading day
prior  to the  date  of  Aerial's  notice  exercising  the  Derivative  Take-Out
Election,  into the product  obtained by multiplying the number of Aerial Shares
referred to in clause (i) above by the Aerial  Average  during the 20-day period
referred to in this clause  (ii),  (iii) cash in an amount  equal to the product
obtained by  multiplying  the number of Aerial Shares  referred to in clause (i)
above by the Aerial Average during the 20-day period  referred to in clause (ii)
above, or (iv) any  combination of Aerial Shares,  TDS Shares or cash having the
same aggregate value (the "Derivative  Take-Out  Consideration"),  using the TDS
Average  referred to in clause (ii) above, and the Aerial Average referred to in
clause (iii) above,  to determine  the value of any TDS Shares or Aerial  Shares
delivered in such  exchange.  Aerial  agrees to deliver or cause the  Derivative
Take-Out Consideration to be delivered,  on or before the twentieth Business Day
after Aerial's exercise of the Derivative Take-Out Election, to or upon

                                     - 48 -

<PAGE>



the written  order of the Sonera  Holder that  issued the  Derivative,  with any
Aerial  Shares  or TDS  Shares to be so  delivered  to be issued in such name or
names as such Sonera Holder may direct.

                  (d) The right to issue a  Derivative  pursuant to this Section
5.4 shall terminate in the event that the Aggregate  Converted  Percentage falls
below 5.3%.

                  5.5  Transfers  Prior to Fifth  Anniversary.  (a) In the event
that (i) prior to the third  Anniversary,  Sonera Corporation U.S. has delivered
at least one Project Notice (including a Proposed Business Plan) to AOC pursuant
to Section 3.01(b) of the Joint Venture Agreement,  (ii) the Investment Election
Period  provided  for in Section  3.01(b)  of the Joint  Venture  Agreement  has
expired with respect to all such notices,  and (iii) AOC and Sonera  Corporation
U.S.  have not formed or agreed to form any LLC (as  defined in Section  2.02 of
the Joint Venture Agreement),  then,  notwithstanding Sections 5.1(c) and 5.4(a)
hereof,  (A) each  Sonera  Holder  shall have the right,  upon 90 days'  written
notice to Aerial,  to issue a  Derivative  (and to assign such  Sonera  Holder's
right to exercise the Equity  Purchase  Election  after the tenth  Anniversary),
provided that any Derivative  issued by a Sonera Holder pursuant to this Section
5.5(a) shall be expressly  subject to the provisions of Sections 5.4(b) and (c),
8(d) and 10.5 hereof,  and (B) the Sonera  Holders,  jointly and not  severally,
shall have the right,  exercisable at any time prior to the fifth Anniversary by
giving written notice to Aerial, to Transfer all of the AOC Shares owned by them
to any one (and  not  more  than  one)  Third  Party  Transferee,  other  than a
Competitor,  without the consent of TDS or Aerial;  provided,  however,  that no
such Transfer shall be made unless the transferring Sonera Holders first

                                     - 49 -

<PAGE>



deliver a  Transfer  Notice to Aerial  and  afford  Aerial  the  opportunity  to
negotiate an  acquisition  of all (and not less than all) such AOC Shares in the
manner provided in Section 5.2 hereof.

                  (b) In the  event  that  the  Sonera  Holders,  jointly,  have
complied  with  Section  5.2  hereof  and  effect a  Transfer  of AOC Shares (in
compliance with Section 5.1(b)) to a Third Party Transferee  pursuant to Section
5.5(a) hereof:

                           (i)      the transferring Sonera Holders shall have 
the right to assign all of their rights under this  Agreement to any Third Party
Transferee;

                           (ii)  Aerial  agrees  that  it  will  enter  into  an
agreement with a Third Party Transferee who acquires at least 964,193 AOC Shares
to provide such transferee with registration rights  substantially  identical to
those  provided  to Sonera  and its  Affiliates  under the  Registration  Rights
Agreement; and

                           (iii) all of the AOC Shares  transferred to any Third
Party Transferee will remain subject to the provisions of Section 10.5 hereof.

                                    ARTICLE 6
                              RESTRICTION ON LIENS


                                     - 50 -

<PAGE>



                  No Sonera Holder shall effect any pledge, mortgage, assignment
by way of security,  or other lien or encumbrance of any nature ("Lien"),  other
than such as may be  deemed  to arise  pursuant  to this  Agreement,  on or with
respect to any of the AOC Shares held by it;  provided,  however,  that any such
holder  shall be  permitted,  when  required  under  instruments  governing  its
indebtedness  for  borrowed  money,  to place Liens on AOC Shares owned by it to
secure  such  indebtedness  if such  Liens or any  rights of the  secured  party
thereunder  with  respect  to the AOC  Shares  are  subject  to the  rights  and
obligations  of the holder of such AOC Shares under this  Agreement  and neither
such secured  party nor any  Affiliate  thereof is a  Competitor;  and provided,
further,  that upon any  foreclosure  or enforcement of remedies by such secured
party upon the AOC Shares  subject to such Lien,  such  secured  party  shall be
deemed to be a Sonera Holder  entitled to exercise the rights provided to Sonera
Holders  under  Section  5.4 and  Articles  7 and 8 hereof or any  other  rights
provided  Sonera  Holders  (including  such secured  party) under this Agreement
shall terminate.

                                    ARTICLE 7
                            EQUITY EXCHANGE ELECTION

                  7.1 Exchange of AOC Shares for Aerial  Shares.  Aerial  agrees
that each  Sonera  Holder  shall  have the right,  at the option of such  Sonera
Holder, at any time after (a) the close of business on the tenth Anniversary, or
(b) any TDS  Change in Control  occurring  prior to the tenth  Anniversary,  and
except in either case as otherwise provided herein, to exchange one or more AOC

                                     - 51 -

<PAGE>



Shares for Aerial Shares (except as otherwise provided in Section 7.8 hereof) on
and  subject to the terms and  conditions  hereinafter  set forth  (the  "Equity
Exchange Election").

                  7.2 Exchange  Rate.  Subject to the  provisions for adjustment
set forth in this  Article 7, each AOC Share shall be  exchangeable  for 6.72919
fully  paid and  non-assessable  Aerial  Common  Shares,  calculated  as to each
exchange to the nearest whole share (such  exchange  rate, as adjusted from time
to time  pursuant  to  Section  7.3(a)  hereof,  being  hereinafter  called  the
"Exchange Rate Applicable to Aerial Common Shares").

                  7.3      Adjustment of Exchange Rate. (a) Prior to Aerial 
Merger or  Distribution.  Prior to the earlier to occur of the Aerial  Merger or
the Distribution,  the Exchange Rate Applicable to Aerial Common Shares shall be
adjusted from time to time as follows:

                           (i)      In the event that Aerial shall (A) pay a 
dividend on the  outstanding  Aerial  Common Shares in the form of Aerial Common
Shares, (B) subdivide the outstanding Aerial Common Shares into a greater number
of shares,  or (C) combine the  outstanding  Aerial Common Shares into a smaller
number of shares, the Exchange Rate Applicable to Aerial Common Shares in effect
immediately  prior thereto shall be adjusted so that the holder of any AOC Share
thereafter  surrendered  for exchange shall be entitled to receive the number of
Aerial  Common  Shares  which such holder  would have owned or been  entitled to
receive after the happening of any such event had such AOC Share been  exchanged
immediately  prior to the happening of such event.  Any  adjustment  pursuant to
this Section  7.3(a)(i) shall become effective  retroactively  immediately after
the record

                                     - 52 -

<PAGE>



date in the case of any dividend and shall become  effective  immediately  after
the effective date in the case of any subdivision or combination.

           (ii) In the event that Aerial shall issue to all holders of the outs-
tanding Aerial Common Shares any rights or warrants entitling them (for a period
expiring within 45 days after the record date specified below) to subscribe 
for or purchase Aerial Common Shares at a price per share  less than the  Aerial
Average for the 20  consecutive  trading day period  ending on the third trading
date prior to the record date for the determination of shareholders  entitled to
receive such rights or warrants,  the Exchange Rate  Applicable to Aerial Common
Shares shall be adjusted so that it shall equal the rate  determined as follows:
the Exchange Rate Applicable to Aerial Common Shares in effect immediately prior
to such record date shall be  multiplied  by a fraction,  the numerator of which
shall be (A) the sum of the number of shares of Aerial Common Stock  outstanding
on such record date plus the number of additional  Aerial Common Shares  offered
for subscription or purchase,  and the denominator of which shall be (B) the sum
of the number of shares of Aerial Common Stock  outstanding  on such record date
plus the quotient  obtained by dividing  the  aggregate  offering  price for the
total number of Aerial  Common  Shares so offered for  subscription  or purchase
(before  deduction of  commissions,  concessions or discounts paid or allowed or
expenses  incurred)  by such  Aerial  Average.  Such  adjustment  shall  be made
successively  whenever  any such rights or warrants  are issued and shall become
effective  retroactively  immediately  after such record  date.  In  determining
whether any rights or warrants  entitle the holders to subscribe for or purchase
Aerial Common Shares at less than the Aerial  Average,  and in  determining  the
aggregate  offering  price of Aerial  Common  Shares,  there shall be taken into
account any consideration received by Aerial for

                                     - 53 -

<PAGE>



such rights or warrants, the value of such consideration, if other than cash, to
be reasonably determined by its Board of Directors. In the event that all of the
Aerial Common Shares offered for subscription or purchase are not subscribed for
and  purchased  pursuant  to the  rights or  warrants  referred  to in the first
sentence of this Section  7.3(a)(ii),  the Exchange  Rate  Applicable  to Aerial
Common Shares shall be retroactively adjusted, as of the record date referred to
in the first sentence of this Section 7.3(a)(ii),  to reflect that fact, and any
exchanges  occurring  after  such  record  date and  prior  to such  retroactive
adjustment shall be adjusted accordingly.

 (iii) In the event that Aerial shall distribute to all holders of the outstand-
ing Aerial Common Shares any shares of its stock of any class (other than Aerial
Common Shares), any securities,  evidences of indebtedness or rights or warrants
of Aerial or any subsidiary  thereof (other than rights or warrants  referred to
in Section  7.3(a)(ii)  hereof),  or any other assets (other than cash dividends
payable out of earnings or surplus legally available  therefor under the laws of
the jurisdiction of  incorporation  of Aerial),  the Exchange Rate Applicable to
Aerial  Common  Shares  shall  be  adjusted  so that it  shall  equal  the  rate
determined as follows:  the Exchange Rate  Applicable to Aerial Common Shares in
effect   immediately   prior  to  the  record  date  for  the  determination  of
shareholders  entitled to receive such  distribution  shall be  multiplied  by a
fraction,  the  numerator  of  which  shall  be the  Aerial  Average  for the 20
consecutive  trading  day period  ending on the third  trading day prior to such
record date and the  denominator of which shall be such Aerial Average minus the
fair value (as reasonably  determined by the Board of Directors of Aerial, which
determination  shall be  conclusive) of such  distribution  with respect to each
Aerial Common Share

                                     - 54 -

<PAGE>



outstanding  immediately prior to such record date. Such adjustment shall become
effective immediately after such record date.

                           (iv)     In the event of any capital reorganization 
of  Aerial,  any  reclassification  of Aerial  Common  Shares  or any  merger or
consolidation of Aerial with or into any other corporation  (other than a merger
in which Aerial shall be the surviving corporation and which shall not result in
any  reclassification of the outstanding Aerial Common Shares),  provision shall
be made as part of the terms of such capital  reorganization,  reclassification,
merger or consolidation  whereby each AOC Share  outstanding  after such capital
reorganization,  reclassification, merger or consolidation shall be exchangeable
for the kind and amount of shares of stock or other  securities  or  property to
which  the  Aerial  Common  Shares   issuable  (at  the  time  of  such  capital
reorganization, reclassification, merger or consolidation) upon exchange of such
AOC  Share  would  have  been   entitled   upon  such  capital   reorganization,
reclassification,  merger  or  consolidation  and  shall  have  the  benefit  of
adjustments thereafter which shall be as nearly equivalent as practicable to the
adjustments  provided for in this Section  7.3(a).  Neither the  subdivision  or
combination  of the  outstanding  Aerial  Common Shares into a greater or lesser
number of Aerial  Common  Shares,  nor the change in the par value of the Aerial
Common  Shares,  or from par value to no par value,  or from no par value to par
value, shall be deemed to be a reclassification  of the Aerial Common Shares for
the  purposes  of this  Section  7.3(a)(iv).  The  provisions  of  this  Section
7.3(a)(iv)  shall  similarly  apply  to  successive   capital   reorganizations,
reclassifications, mergers or consolidations.


                                     - 55 -

<PAGE>



         (b) Effect of Aerial Merger or Distribution.  (i) In the event that the
Aerial Merger shall occur at any time after the date of this Agreement and prior
to the  Distribution,  then in  lieu of any  adjustment  otherwise  required  by
Section 7.3(a) hereof,  the Exchange Rate  Applicable to Aerial Common Shares in
effect  immediately  prior to the date of such  Merger  shall  be  adjusted  (to
determine the Exchange Rate  Applicable to Aerial Group Shares,  as  hereinafter
defined) by multiplying such exchange rate by a fraction, the numerator of which
shall be the Number of Aerial Group  Shares,  determined  immediately  after the
Aerial Merger,  and the denominator of which shall be the total number of shares
of Aerial Common Stock outstanding immediately prior to the Aerial Merger.

                           (ii)     In the event that the Distribution shall 
occur at any time  after  the date of this  Agreement  and  prior to the  Aerial
Merger,  then in lieu of any  adjustment  otherwise  required by Section  7.3(a)
hereof:

                           (A)      the  Exchange  Rate  Applicable  to  Aerial 
Common Shares in effect immediately prior to the date of such Distribution shall
be adjusted (to determine  the Exchange Rate  Applicable to Aerial Group Shares,
as  hereinafter  defined) by multiplying  such exchange rate by a fraction,  the
numerator  of which shall be the  quotient  obtained  by dividing  the Number of
Aerial Group Shares by TDS's  percentage  ownership of Aerial Common  Stock,  in
each case determined immediately after the Distribution,  and the denominator of
which shall be the total  number of shares of Aerial  Common  Stock  outstanding
immediately prior to such Distribution; and


                                     - 56 -

<PAGE>



                           (B)      in the event that the Aerial Merger shall 
thereafter  occur, the Exchange Rate applicable to Aerial Group Shares in effect
immediately  prior  to the  date of such  merger  shall  be  adjusted  so  that,
immediately after such merger, the quotient obtained by dividing (I) the product
of the  aggregate  number  of AOC  Shares  owned  by  Sonera  and its  Permitted
Affiliate Transferees  (determined  immediately after such merger) multiplied by
such exchange rate, as adjusted pursuant to this Section 7.3(b)(ii)(B),  by (II)
the sum of (1) the Number of Aerial Group Shares,  determined  immediately after
such merger, and (2) the product referred to in (I) above, shall be equal to the
quotient  obtained by dividing  (x) the product of the  aggregate  number of AOC
Shares owned by Sonera and its Permitted  Affiliate  Transferees,  multiplied by
the exchange Rate  Applicable to Aerial Group  Shares,  in each case  determined
immediately  before such merger,  by (y) the sum of (1) the quotient obtained by
dividing  the Number of Aerial  Group  Shares by TDS's  percentage  ownership of
Aerial Common Stock  (determined  immediately  before such merger),  and (2) the
product referred to in (x) above.

                           (iii)  The Exchange Rate Applicable to Aerial Common 
Shares, as adjusted pursuant to Section 7.3(b)(i) or (ii) hereof, as applicable,
and as further adjusted from time to time pursuant to Section 7.3(c) hereof,  is
hereinafter called the "Exchange Rate Applicable to Aerial Group Shares".

                           (iv) In the event that the Equity  Exchange  Election
is exercised at any time after the earlier of (A) the date of the Aerial Merger,
or (B) the date of the Distribution,  each  AOC  Share  shall  be exchanged  for
that number of fully paid and non-assessable Aerial Group Shares,

                                     - 57 -

<PAGE>



equal to the Exchange Rate  Applicable to Aerial Group Shares,  calculated as to
each exchange of shares to the nearest Aerial Group Share.

                  (c) After Aerial Merger or Distribution.  After the earlier to
occur of the Aerial Merger or the Distribution,  the Exchange Rate Applicable to
Aerial Group Shares shall be adjusted from time to time as follows:

                           (i)      In  the  event  that  TDS  shall  (A)  pay a
dividend with respect to Aerial Group Shares in the form of Aerial Group Shares,
(B)  subdivide the Aerial Group Shares into a greater  number of shares,  or (C)
combine the Aerial  Group Shares into a smaller  number of shares,  the Exchange
Rate Applicable to Aerial Group Shares in effect immediately prior thereto shall
be  adjusted  so that the  holder of any AOC Share  thereafter  surrendered  for
exchange  shall be entitled to receive the number of Aerial  Group  Shares which
such holder would have owned or been  entitled to receive after the happening of
any such  event  had such AOC  Share  been  exchanged  immediately  prior to the
happening of such event. Any adjustment pursuant to this Section 7.3(c)(i) shall
become effective retroactively  immediately after the record date in the case of
any dividend and shall become effective  immediately after the effective date in
the case of any subdivision or combination.

                           (ii) In the event that TDS shall issue to all holders
of the Aerial Group Shares any rights or warrants entitling  them (for a period 
expiring within 45 days after the record date specified below) to subscribe  
for or purchase Aerial Group Shares at a price per share less than the Aerial   
Average for the 20 consecutive trading day period ending on the third trading   
date prior to

                                     - 58 -

<PAGE>



the record date for the  determination of shareholders  entitled to receive such
rights or warrants, the Exchange Rate Applicable to Aerial Group Shares shall be
adjusted so that it shall equal the rate  determined  as follows:  the  Exchange
Rate  Applicable  to Aerial  Group  Shares in effect  immediately  prior to such
record date shall be multiplied  by a fraction,  the numerator of which shall be
(A) the sum of the Number of Aerial  Group  Shares on such  record date plus the
number of additional  Aerial Group Shares offered for  subscription  or purchase
(including any Aerial Group Shares issued to increase the "Retained Interest" or
any  "Inter-Group  Interest"  (as  those  terms  are  defined  in  the  Restated
Certificate)),  and the  denominator of which shall be (B) the sum of the Number
of  Aerial  Group  Shares on such  record  date plus the  quotient  obtained  by
dividing  the  aggregate  offering  price for the total  number of Aerial  Group
Shares  (including  any Aerial  Group Shares  issued to increase  the  "Retained
Interest"  or any  "Inter-Group  Interest"  (as those  terms are  defined in the
Restated Certificate)) so offered for subscription or purchase (before deduction
of commissions,  concessions or discounts paid or allowed or expenses  incurred)
by such Aerial Average.  Such adjustment shall be made successively whenever any
such  rights or warrants  are issued and shall  become  effective  retroactively
immediately  after  such  record  date.  In  determining  whether  any rights or
warrants entitle the holders to subscribe for or purchase Aerial Group Shares at
less than the Aerial Average, and in determining the aggregate offering price of
Aerial  Group  Shares,  there  shall be taken  into  account  any  consideration
received by TDS for such rights or warrants, the value of such consideration, if
other than cash, to be reasonably  determined by its Board of Directors.  In the
event that all of the Aerial Group Shares offered for  subscription  or purchase
(including any Aerial Group Shares issued to increase the "Retained Interest" or
any  "Inter-Group  Interest"  (as  those  terms  are  defined  in  the  Restated
Certificate)) are not subscribed for and purchased pursuant to the rights or

                                     - 59 -

<PAGE>



warrants  referred to in the first  sentence  of this  Section  7.3(c)(ii),  the
Exchange Rate Applicable to Aerial Group Shares shall be retroactively adjusted,
as of the  record  date  referred  to in the  first  sentence  of  this  Section
7.3(c)(ii),  to reflect that fact, and any exchanges occurring after such record
date and prior to such retroactive adjustment shall be adjusted accordingly.

                           (iii) In the event that TDS shall make a distribution
with  respect to the Number of Aerial Group Shares of any shares of its stock of
any class  (other  than Aerial  Group  Shares),  any  securities,  evidences  of
indebtedness or rights or warrants of TDS or any subsidiary  thereof (other than
rights or  warrants  referred  to in Section  7.3(c)(ii)  hereof),  or any other
assets  (other than cash  dividends  payable out of earnings or surplus  legally
available  therefor under the laws of the jurisdiction of incorporation of TDS),
the Exchange Rate Applicable to Aerial Group Shares shall be adjusted so that it
shall equal the rate  determined  as follows:  the Exchange  Rate  Applicable to
Aerial  Group  Shares in effect  immediately  prior to the  record  date for the
determination  of shareholders  entitled to receive such  distribution  shall be
multiplied by a fraction, the numerator of which shall be the Aerial Average for
the 20  consecutive  trading day period ending on the third trading day prior to
such record date and the denominator of which shall be such Aerial Average minus
the fair value (as reasonably determined by the Board of Directors of TDS, which
determination  shall be  conclusive) of such  distribution  with respect to each
Aerial Group Share  (including any "Aerial Group Shares Issuable with Respect to
Retained Interest" and "Aerial Group Shares Issuable with Respect to Inter-Group
Interest",  as those  terms  are  defined  in the  Restated  Certificate).  Such
adjustment shall become effective immediately after such record date.


                                     - 60 -

<PAGE>



                           (iv) In the event of any  capital  reorganization  of
TDS, any  reclassification of Aerial Group Shares or any merger or consolidation
of TDS with or into any  other  corporation  (other  than a merger  in which TDS
shall  be  the  surviving   corporation  and  which  shall  not  result  in  any
reclassification  of the  outstanding  Aerial Group Shares),  provision shall be
made as part of the  terms  of such  capital  reorganization,  reclassification,
merger or consolidation  whereby each AOC Share  outstanding  after such capital
reorganization,  reclassification, merger or consolidation shall be exchangeable
for the kind and amount of shares of stock or other  securities  or  property to
which  the  Aerial  Group   Shares   issuable  (at  the  time  of  such  capital
reorganization, reclassification, merger or consolidation) upon exchange of such
AOC  Share  would  have  been   entitled   upon  such  capital   reorganization,
reclassification,  merger  or  consolidation  and  shall  have  the  benefit  of
adjustments thereafter which shall be as nearly equivalent as practicable to the
adjustments  provided for in Section 7.3(c) hereof.  Neither the  subdivision or
combination  of the  outstanding  Aerial  Group  Shares into a greater or lesser
number of Aerial  Group  Shares,  nor the  change in the par value of the Aerial
Group  Shares,  or from par value to no par  value,  or from no par value to par
value, shall be deemed to be a  reclassification  of the Aerial Group Shares for
the  purposes  of this  Section  7.3(c)(iv).  The  provisions  of  this  Section
7.3(c)(iv)  shall  similarly  apply  to  successive   capital   reorganizations,
reclassifications, mergers or consolidations.

                  7.4 Surrender of AOC Certificates. Each exchange of AOC Shares
for Aerial Shares shall be effected by  surrendering  to Aerial  during  regular
business  hours  at its  principal  executive  office  one or more  certificates
representing  AOC  Shares,  accompanied  by a  written  notice  executed  by the
surrendering holder specifying the number of AOC Shares represented by each

                                     - 61 -

<PAGE>



certificate to be exchanged and the name and address of the Person in whose name
each  certificate  for Aerial  Shares is to be issued  and,  if so  required  by
Aerial,  accompanied  by an  instrument  of transfer,  in form  satisfactory  to
Aerial,  duly executed by such holder or his duly authorized  representative and
payment of any applicable  transfer taxes.  Subject to the provisions of Section
7.8 hereof, each such exchange shall be deemed to have been effected on the date
(the "Exchange  Date") on which the  requirements of the  immediately  preceding
sentence  shall  have  been  satisfied,  and  the  person  in  whose  name  each
certificate for Aerial Shares shall be issuable on such exchange shall be deemed
to have become on the Exchange Date the holder of record of the Aerial Shares to
be represented thereby.

                  7.5   Issuance   of  Aerial   Certificates.   As  promptly  as
practicable  and in no event more than 30 days after the surrender for exchange,
as provided in Section 7.4 hereof,  of any certificate  representing AOC Shares,
Aerial (or TDS, if  applicable)  shall  deliver at such  office,  to or upon the
written order of the holder  thereof,  a  certificate  or  certificates  for the
number of full Aerial Shares issuable upon such exchange.  No fractional  Aerial
Share,  or scrip  representing a fractional  Aerial Share,  shall be issued upon
such exchange, but in lieu thereof,  Aerial (or TDS, if applicable) shall pay in
cash the fair  value  thereof  as of the  Exchange  Date,  based upon the Aerial
Average (or the Aerial Group  Average,  if  applicable)  for the 20  consecutive
trading day period ending on the third  trading day prior to the Exchange  Date.
If more than one  certificate  representing  AOC Shares shall be surrendered for
exchange,  the number of full Aerial  Shares  which shall be issuable  upon such
exchange shall be determined on the basis of the aggregate  number of AOC Shares
being exchanged. In case any certificate for AOC Shares shall be surrendered for
exchange

                                     - 62 -

<PAGE>



of only a part of the  shares  represented  thereby,  AOC shall  deliver at such
office,  to or upon the written order of the holder  thereof,  a certificate  or
certificates for the number of AOC Shares not being  exchanged.  No charge shall
be made upon the exchange of AOC Shares for Aerial  Shares.  Neither  Aerial nor
TDS  shall be  required  to pay any tax  which  may be  payable  because  of the
delivery of any  certificate in a name other than that of the registered  holder
of the AOC  Shares  being  exchanged,  and none of  Aerial,  TDS or AOC shall be
required to deliver any such certificate unless and until the amount of such tax
and the payment thereof shall have been  established to the  satisfaction of the
issuer of such certificate.

                  7.6  Dividends.  No  payment  or  adjustment  shall be made on
account of any cash  dividends  paid or payable on Aerial  Shares,  except  cash
dividends  which  shall be payable  to holders of Aerial  Shares of record on or
after the applicable Exchange Date.

                  7.7 Redemption of AOC Shares. In the case of AOC Shares called
for  redemption  in  accordance  with AOC's  Certificate  of  Incorporation,  as
amended,  the right to exchange  such shares as provided in this Article 7 shall
terminate  at the close of  business  on the date fixed for  redemption  of such
shares (defined as the "Redemption Date" in such Certificate of  Incorporation),
unless payment of the redemption  price of such shares shall not be duly paid in
accordance with such Certificate of Incorporation.

                  7.8      Application.  (a)        In any case in which Section
7.3(a)  or  7.3(c)   provides   that  an  adjustment   shall  become   effective
retroactively immediately after a record date for an event,

                                     - 63 -

<PAGE>



Aerial or TDS, as the case may be, may defer until the  occurrence of such event
(i) delivering to the holder of any AOC Share  exchanged  after such record date
and before the occurrence of such event the additional Aerial Shares deliverable
upon such exchange by reason of the  adjustment  required by such event over and
above the Aerial Shares issuable upon such exchange before giving effect to such
adjustment,  and (ii)  paying to such  holder  any amount in cash in lieu of any
fraction pursuant to Section 7.5 hereof.

                  (b) No adjustment in the Exchange Rate shall be made by reason
of any conversion of Series A Common Shares of Aerial into Aerial Common Shares.

                  (c) Each  adjustment in the Exchange Rate shall be made to the
fifth decimal place and all  calculations  under this Article 7 shall be made as
to each exchange to the nearest whole share.

                  7.9 Notice of Adjustment.  Whenever the Exchange Rate shall be
adjusted as provided in Section 7.3 hereof by at least  one-tenth  (1/10th) of a
share,  Aerial  or TDS,  as the case may be,  shall  promptly  prepare  a notice
setting forth the Exchange Rate after such adjustment,  a brief statement of the
facts requiring such adjustment and the effective date of such  adjustment,  and
shall  cause  the same to be mailed  promptly  to the  holders  of record of AOC
Shares (other than Aerial) at their addresses as shown on the books of AOC.


                                     - 64 -

<PAGE>



                  7.10 Ownership of Surrendered AOC Shares. All AOC Shares which
shall have been  surrendered  for  exchange as provided in this  Article 7 shall
thereafter  be deemed for all purposes to be owned by Aerial or TDS, as the case
may be.

                  7.11 Termination. The Equity Exchange Election shall terminate
(a) with respect to any AOC Shares  transferred to a Third Party Transferee that
acquires  less than  964,193 AOC Shares  (appropriately  adjusted to reflect any
stock  dividend  subdivision  or  combination  affecting AOC Shares),  upon such
Transfer,  (b) with  respect  to any AOC  Shares  transferred  to a Third  Party
Transferee that acquires at least 964,193 AOC Shares (appropriately  adjusted to
reflect any stock dividend  subdivision  or  combination  affecting AOC Shares),
upon the twelfth Anniversary, and (c) with respect to all other AOC Shares, upon
the twentieth Anniversary.

                                    ARTICLE 8
                            EQUITY PURCHASE ELECTION

                  (a) At any time  (i)  after  the  ninth  Anniversary,  or (ii)
during the 40 Business  Days after its receipt of notice from TDS that (A) a TDS
Change in Control has  occurred,  (B) the  shareholders  of TDS have  approved a
going  private  transaction,  as a result of which  TDS will no longer  have any
equity securities  trading on a national  securities  exchange or authorized for
quotation  on the  NASDAQ,  or (C)  Aerial  has  authorized  the  sale of all or
substantially all of the assets of AOC and its  Subsidiaries,  Sonera shall have
the right, upon 30 days' written notice to

                                     - 65 -

<PAGE>



Aerial,  to  require  Aerial  to  purchase  all but not less than all of the AOC
Shares owned by all of the Sonera Holders (the "Equity Purchase Election").

                  (b) In the event  Sonera makes the Equity  Purchase  Election,
each AOC Share shall be exchanged  for, at Aerial's  option,  (i) that number of
Aerial  Shares equal to the product  obtained by  multiplying  the number of AOC
Shares to be so purchased by the Exchange  Rate,  (ii) that number of TDS Shares
determined  by dividing  the TDS  Average for the 20 trading  days ending on the
last  trading  day prior to its  receipt of  Sonera's  notice  making the Equity
Purchase Election, into the product obtained by multiplying the number of Aerial
Shares  referred to in clause (i) above by the Aerial  Average during the 20-day
period  referred to in this clause  (ii),  (iii) cash in an amount  equal to the
product  obtained  by  multiplying  the number of Aerial  Shares  referred to in
clause (i) above by the Aerial Average  during the 20-day period  referred to in
clause (ii) above, or (iv) any combination of Aerial Shares,  TDS Shares or cash
having the same aggregate  value (the "Purchase  Consideration"),  using the TDS
Average  referred to in clause (ii) above, and the Aerial Average (or the Aerial
Group Average,  if applicable)  referred to in clause (iii) above,  to determine
the value of any TDS Shares or Aerial Shares  delivered in connection  with such
exchange.  On or before the fortieth  Business Day after its receipt of Sonera's
notice making the Equity  Purchase  Election,  Aerial agrees to deliver or cause
the  Purchase  Consideration  to be  delivered  to or upon the written  order of
Sonera,  with any Aerial Shares or TDS Shares to be so delivered to be issued in
such  name  or  names  as  Sonera  may  direct.  Notwithstanding  the  foregoing
provisions of this  paragraph  (b),  Aerial's  right to deliver TDS Shares other
than Aerial  Group  Shares in lieu of Aerial  Shares  shall  terminate  upon the
earlier to occur of the Aerial Merger or the Distribution.

                                     - 66 -

<PAGE>



                  (c) At any time during the 30 calendar days  following each of
the fifth, sixth, seventh and eighth Anniversaries, Sonera shall have the right,
upon written notice to Aerial, to make the Equity Purchase Election with respect
to one-fifth of the aggregate number of Purchased Shares (the "Minimum Number of
AOC Shares").  Such right shall be cumulative,  provided that such right may not
be  exercised at any time to require  Aerial to purchase  fewer than the Minimum
Number of AOC Shares.

                  (d)  Notwithstanding  any  provision of this  Agreement to the
contrary,  if (i)  Sonera and its  Permitted  Affiliate  Transferees  own in the
aggregate less than 5% of the  outstanding  AOC Shares at any time, and (ii) any
Sonera Holder has (A) failed to exercise in full any subscription  right that it
may have  pursuant to Section 4.1 hereof,  (B) issued a  Derivative  pursuant to
Section  5.4 or 5.5  hereof,  or (C)  Transferred  any AOC Shares (or any of the
Aerial  Shares for which such AOC Shares may be  exchanged),  then Aerial  shall
have the right,  by giving written notice to Sonera,  to require Sonera and each
of its Permitted Affiliate  Transferees to exercise the Equity Purchase Election
and they shall promptly exercise,  and in the absence thereof shall be deemed to
have exercised, the Equity Purchase Election on the thirtieth day after the date
of Aerial's written notice to Sonera.


                                    ARTICLE 9
                               RIGHTS TO PURCHASE
                                  AERIAL SHARES

                                     - 67 -

<PAGE>



                  9.1 Right to Purchase.  (a) Aerial Common  Shares.  If, at any
time after the date of this Agreement and prior to the tenth Anniversary, Aerial
proposes  to issue  for cash (or sell  for cash  from  treasury)  Aerial  Common
Shares, or securities convertible into or exchangeable for Aerial Common Shares,
including  debt  securities  convertible  into equity  securities  of Aerial but
excluding  non-voting,  non-convertible  preferred  stock  and  debt  securities
containing nominal equity features,  and excluding Aerial Common Shares issuable
(i) in connection  with bona fide stock option or other employee  benefit plans,
(ii) upon  conversion of debt securities  into equity  securities of Aerial,  or
(iii) upon  conversion  of Series A Common  Shares of Aerial,  Aerial shall give
written notice (a "New Issue Sale Notice") to Sonera setting forth in reasonable
detail  (A) the  designation  or any of the terms and  provisions  of the equity
securities proposed to be issued (the "New Issue Securities"), (B) the price and
other  terms of the  proposed  sale of such  securities,  (C) the amount of such
securities  proposed  to be  issued,  and  (D)  such  other  information  as may
reasonably  be requested in order to evaluate the proposed  issuance;  provided,
however,  that if the New Issue  Securities to be sold are Aerial Common Shares,
then the price at which  Aerial  shall offer to sell such shares to Sonera shall
be equal to the Aerial  Average  for the five  trading  days  ending on the last
trading day prior to the date of the New Issue Sale  Notice.  Subject to (1) the
subscription  rights  granted  to TDS as a holder of  Series A Common  Shares of
Aerial  pursuant  to  Aerial's   Certificate  of  Incorporation,   and  (2)  the
subscription  rights granted to TDS under Article III of the Exchange Agreement,
Sonera  shall have the right to subscribe to purchase all or any portion of such
New Issue Securities issued.


                                     - 68 -

<PAGE>



                  (b)  Aerial  Group  Shares.  If, at any time after the date of
this Agreement and prior to the tenth Anniversary, TDS proposes (i) to issue for
cash (or sell for  cash  from  treasury)  Aerial  Group  Shares,  or  securities
convertible  into or  exchangeable  for  Aerial  Group  Shares,  including  debt
securities  convertible  into Aerial Group Shares but excluding shares issued or
sold out of the Retained  Interest or any  Inter-Group  Interest with respect to
the  Aerial  Group,  non-voting,   non-convertible   preferred  stock  and  debt
securities containing nominal equity features, and excluding Aerial Group Shares
issuable  (A) in  connection  with bona fide  stock  options  or other  employee
benefit plans, or (B) upon conversion of debt securities convertible into Aerial
Group Shares, or (ii) to increase the "Number of Shares Issuable with Respect to
Retained Interest" (as that term is defined in the Restated  Certificate) or the
"Number of Shares  Issuable with Respect to the  Inter-Group  Interest" (as that
term is defined in the Restated  Certificate),  in each case with respect to the
Aerial Group,  TDS shall give a New Issue Sale Notice to Sonera setting forth in
reasonable  detail (1) the  designation  and all of the terms and  provisions of
such New  Issue  Securities,  (2) the  price  and  other  terms of the  proposed
issuance or sale of such securities,  (3) the amount of such securities proposed
to be  issued or sold,  and (4) such  other  information  as may  reasonably  be
necessary in order to evaluate the proposed issuance;  provided,  however, that,
if such New Issue Securities to be sold are Aerial Group Shares,  then the price
at which TDS shall offer to sell such shares to Sonera shall be the Aerial Group
Average for the five  trading  days ending on the last  trading day prior to the
date of the New Issue Sale  Notice.  Sonera shall have the right to subscribe to
purchase 17.5% of such New Issue Securities.


                                     - 69 -

<PAGE>



                  (c)  Notwithstanding  the  provisions  of Sections  9.1(a) and
9.1(b) hereof, the right to purchase New Issue Securities provided therein shall
not be  available to Sonera to the extent that (i) the  exercise  thereof  would
increase the Aggregate Converted  Percentage above 35%, or (ii) Sonera is unable
to subscribe for or own the New Issue Securities as a result of its inability to
satisfy any applicable legal or regulatory  requirement for such subscription or
ownership.

                  9.2  Exercise of Purchase  Right.  Sonera  shall give  written
notice that it wishes to subscribe for New Issue Securities to Aerial or TDS, as
the case may be,  within ten  Business  Days after its  receipt of the New Issue
Sale Notice.  Payment for the New Issue Securities  subscribed for shall be made
on a date specified in the New Issue Sale Notice (a "New Issue Closing"),  which
shall be at least 30 Business Days after the date of such notice, at the offices
of Aerial or TDS,  as the case may be, or at such  other  place or on such other
date as Aerial or TDS, as the case may be, and Sonera may agree in  writing.  At
the New  Issue  Closing,  Aerial  or TDS,  as the  case  may be,  shall  deliver
certificates  to Sonera (or any  Permitted  Affiliate  Transferee  designated by
Sonera)  representing the New Issue Securities to be purchased,  against payment
of the purchase price therefor by wire transfer of immediately  available  funds
to an  account  designated  by Aerial or TDS,  as the case may be, at least five
Business Days prior to the date of such New Issue Closing.

                  9.3 Failure to Subscribe. If Sonera fails to subscribe for all
of the New Issue  Securities  pursuant to Section 9.2 hereof,  Aerial or TDS, as
the case may be, shall be free,  for a period  ending 210 days after the date of
such New  Issue  Sale  Notice,  to sell  all or any  portion  of such New  Issue
Securities  that Sonera has not elected to purchase at prices then  available in
the market

                                     - 70 -

<PAGE>



and  otherwise  on terms and  conditions  no more  favorable  to the  purchasers
thereof than those set forth in the New Issue Sale Notice.

                  9.4 Termination of Rights. The rights of all Sonera Holders to
purchase  additional  Aerial Shares pursuant to the provisions of this Article 9
shall  terminate in the event that any Sonera  Holder  disposes of any Purchased
Shares (or any of the  Aerial  Shares  for which  such  Purchased  Shares may be
exchanged),  or issues a  Derivative  pursuant  to Section  5.4 or  Section  5.5
hereof.

                  9.5 No Other  Purchases.  Except  as  otherwise  permitted  by
Sections  9.1  through  9.4  hereof,  Sonera  agrees  that,  prior to the  tenth
Anniversary,  it will  not,  and will  cause  each  other  Sonera  Party not to,
directly  or  indirectly,  acquire,  offer to  acquire or agree to  acquire,  by
purchase or  otherwise,  any Aerial  Shares,  or any other  securities of Aerial
having the right to vote in the  election  of  directors,  without  the  advance
written consent of TDS.



                                   ARTICLE 10
                              TRANSFERS OF CONTROL

                  10.1  Restriction on Transfers of Control of Aerial.  (a) Each
of TDS and Aerial agrees that it will not (i) enter into any agreement providing
for the sale, assignment or other

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disposition of its equity interest in Aerial or AOC, respectively, or (ii) cause
or  permit  Aerial or AOC to enter  into any  agreement  providing  for a merger
(other than the Aerial  Merger) or  consolidation  of Aerial or AOC with or into
any corporation, if in either case the result of such transaction would be that,
(A) TDS would own less that 33 1/3% of the  outstanding  Aerial Common Shares or
control  less than 50% of the combined  voting power (on matters  other than the
election of directors) of all of the then outstanding  Aerial Common Shares,  or
(B) Aerial  would own less than a majority  of the then  outstanding  AOC Shares
(any  such  sale,  assignment,   disposition,   merger  or  consolidation  being
hereinafter referred to as a "Disposition Transaction"), unless such transaction
is entered into in accordance with the provisions of this Article 10.

                  (b) If TDS or  Aerial  desires  to  enter  into a  Disposition
Transaction,  it shall  first  give  written  notice to Sonera of its  desire to
effect such a transaction,  which notice shall describe the transaction that TDS
or Aerial,  as the case may be, desires to effect and refer to this Section 10.1
(the "Aerial Transfer Notice").  Sonera shall have a period of ten days from its
receipt of the Aerial Transfer Notice within which to give TDS or Aerial, as the
case may be, a written  notice that Sonera  desires to invoke the  provisions of
Section  10.1(c) hereof (the "Aerial  Negotiation  Notice").  If Sonera fails to
timely give an Aerial Negotiation Notice or comply with any of the provisions of
Section 10.1(c) hereof,  then TDS or Aerial, as the case may be, may effect such
Disposition Transaction, subject to Section 10.6 hereof.

                  (c) If Sonera timely gives an Aerial Negotiation Notice to TDS
or Aerial,  as the case may be, pursuant to Section 10.1(b) hereof,  then Sonera
shall have the exclusive right to

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negotiate  with  TDS or  Aerial,  as the  case may be,  regarding  the  possible
Disposition Transaction for a period (the "Aerial Negotiation Period") beginning
on the date of the  receipt by TDS or Aerial,  as the case may be, of the Aerial
Negotiation Notice and ending on the earlier to occur of (i) the date upon which
TDS or Aerial,  as the case may be, and Sonera reach agreement on the terms of a
Disposition Transaction, (ii) the date upon which TDS or Aerial, as the case may
be, and Sonera  agree that no such  agreement  can be reached,  or (iii) 60 days
after the  commencement  of the  Aerial  Negotiation  Period.  During the Aerial
Negotiation  Period,  TDS or  Aerial,  as the  case  may be,  and  Sonera  shall
negotiate  in good  faith  to reach  agreement  on the  terms  of a  Disposition
Transaction,  and TDS or Aerial,  as the case may be, shall provide  Sonera with
such  information  in the  possession or control of TDS or Aerial  regarding the
Disposition  Transaction,  TDS, Aerial or AOC, as Sonera may reasonably request.
If the negotiating  parties reach such agreement  during the Aerial  Negotiation
Period,  then they shall  promptly  prepare and file all necessary  applications
with  the  FCC  and  any  other  regulatory  agencies  and  the  closing  of the
Disposition  Transaction  shall  occur  within 30 days after the  receipt of all
necessary FCC and other regulatory approvals.  In the event that the negotiating
parties do not reach such agreement during the Aerial Negotiation  Period,  then
Sonera  shall  give to TDS or  Aerial,  as the case may be, a written  notice of
Sonera's final proposal for a Disposition  Transaction  (in whatever form Sonera
desires) on or before the last day of the Aerial Negotiation Period, which final
proposal  TDS or Aerial,  as the case may be, shall have the right to accept (A)
for a period of 30 days after its receipt  thereof,  during which 30-day  period
such final proposal shall be irrevocable,  and (B) for a period of an additional
60 days thereafter,  during which  additional  60-day period such final proposal
shall be  revocable  by  Sonera  at any time  prior to  Sonera's  receipt  of an
acceptance of such final proposal by TDS or Aerial, as the case may be.

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                  (d) In the  event  that  TDS or  Aerial,  as the  case may be,
neither reaches agreement with Sonera for a Disposition  Transaction nor accepts
Sonera's final proposal pursuant to Section 10.1(c) hereof,  then TDS or Aerial,
as the case may be, shall be permitted to enter into a  Disposition  Transaction
with any third party;  provided,  however, that in no event shall TDS or Aerial,
as the case may be,  enter into an  agreement  for or complete  any  Disposition
Transaction unless (i) TDS or Aerial, as the case may be, has negotiated in good
faith during the Aerial Negotiation  Period to effect a Disposition  Transaction
with Sonera pursuant to Section 10.1(c) hereof,  (ii) TDS or Aerial, as the case
may be, enters into a binding agreement within 180 days after the termination of
such Aerial Negotiation Period for a Disposition  Transaction with a third party
at a price higher than the price  offered to TDS or Aerial,  as the case may be,
by Sonera in its final  proposal,  and (iii) TDS or Aerial,  as the case may be,
and such third party shall comply with the provisions of Section 10.6 hereof.

                  (e) In the  event  that TDS or  Aerial  enters  into a binding
agreement  with a third party to consummate a Disposition  Transaction  prior to
the tenth  Anniversary and Sonera has not exercised its tag-along right pursuant
to  Section  10.6  hereof,  each of TDS and  Aerial  agree  that  the  agreement
effecting  such  Disposition  Transaction  shall require the acquiring  party to
agree in  writing  to accept and be bound by all of the rights of Sonera and its
Affiliates under this Agreement and the Joint Venture Agreement.

                  10.2  Interpretation.  For purposes of Section 10.1 hereof, if
the price in a binding agreement to consummate a Disposition Transaction,  or in
Sonera's final proposal, is to be paid in

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something other than money in a lump sum at the closing,  then TDS or Aerial, as
the case may be, and Sonera shall use their best  efforts to reach  agreement as
to an equivalent in monetary  terms,  which shall  constitute  the price for the
purposes of Section 10.1(d) above. If such an agreement cannot be reached within
15 days after TDS or Aerial, as the case may be (in the case of a final bid), or
Sonera  (in  the  case  of a  binding  agreement  to  consummate  a  Disposition
Transaction) receives written notice of the price offered, such equivalent shall
be determined by an appraiser  agreed-upon within ten days after the end of such
15-day  period  (and paid  equally)  by TDS or  Aerial,  as the case may be, and
Sonera or, if they cannot agree upon an appraiser,  by three appraisers,  one of
whom shall be chosen  within 20 days after the end of such 15-day  period by TDS
or Aerial, as the case may be (and paid by TDS or Aerial),  one of whom shall be
chosen (and paid) by Sonera within the same period,  and the third of whom shall
be chosen by the first  two so  chosen  within an  additional  ten days and paid
equally by TDS or Aerial,  as the case may be, and Sonera.  The  decision of the
agreed-upon  appraiser  or,  as the  case  may  be,  a  majority  of  the  three
appraisers,  shall be made within 45 days after he or they,  as the case may be,
are chosen and shall be final and  binding  upon TDS or Aerial,  as the case may
be, and Sonera.  All time  periods  specified  in Section  10.1 hereof  shall be
extended by the length of time necessary for such  appraiser(s) to be chosen and
for such appraisal to be made (if it becomes necessary).

                  10.3 Spin-off.  The parties agree that (a) a  distribution  by
TDS of the equity of Aerial to the  shareholders of TDS in a spin-off or similar
transaction  in  which  the  holders  of  the  Series  A  Common  Shares  of TDS
immediately prior to such transaction are the owners, directly or indirectly, of
30% or more of the combined voting power (on matters other than the election of

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directors) of the common equity  securities  of Aerial  outstanding  immediately
after  such  transaction,  or  (b)  the  Distribution,  will  not  constitute  a
Disposition Transaction within the meaning of this Article 10.

                  10.4 Termination.  The right of first negotiation provided for
by Section 10.1 shall terminate in the event that (a) any Sonera Holder issues a
Derivative,  (b) the Aggregate  Converted  Percentage falls below 10%, or (c) as
provided in Section 5.3 hereof.

                  10.5 Drag-Along Right. (a) In the event that (i) Sonera or any
of its Permitted Affiliate  Transferees disposes of any Purchased Shares (or any
of the Aerial Shares for which such Purchased Shares may be exchanged) or issues
a Derivative, and (ii) at any time thereafter the Aggregate Converted Percentage
is less than 7.9%,  then either TDS or Aerial shall have the right, if it enters
into a binding  agreement to  consummate a Disposition  Transaction,  to require
Sonera, all of its Permitted Affiliate Transferees,  any Third Party Transferee,
and the holder of any  Derivative,  to sell all but not less than all of the AOC
Shares, and the Derivative,  as the case may be, such sale to occur concurrently
with the  consummation  of the  Disposition  Transaction,  at the same price per
share  (assuming  any such AOC Shares are  converted  to Aerial  Shares)  and on
substantially the same terms and conditions as are obtained by TDS or Aerial, as
the case may be, in such Disposition Transaction.

                  (b) In the event the right  provided in this  Section  10.5 is
exercised, each Sonera Holder, each Third Party Transferee, and each holder of a
Derivative shall take all reasonable steps

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<PAGE>



necessary  to enable such Person to comply with the  provisions  of this Section
10.5,  including  executing and performing a purchase and sale,  merger or other
agreement on substantially  the same terms as TDS or Aerial, as the case may be.
TDS and Aerial,  on the one hand, and Sonera,  on the other hand,  each agree to
make full disclosure to the other  concerning the details of any relationship or
dealings  it  may  have  with  the  other  party  to  the  proposed  Disposition
Transaction.  Each of TDS and Aerial,  as the case may be, agrees to keep Sonera
advised in writing of, and consult on a timely basis with Sonera concerning, any
proposed  Disposition  Transaction  with respect to which it has  exercised  the
right provided in this Section 10.5.

                  (c) The right provided by this Section 10.5 shall be exercised
by giving a written  notice of such exercise to each Sonera  Holder,  each Third
Party Transferee,  and each holder of a Derivative,  setting forth in reasonable
detail the identity of the parties to the proposed Disposition Transaction,  the
proposed  purchase  price,  the terms of payment and the other material terms of
the  proposed  Disposition  Transaction.  Each Sonera  Holder,  each Third Party
Transferee,  and each holder of a Derivative  shall  thereafter  be obligated to
sell to such  third  party all (but not less than all) of its AOC Shares and the
Derivative, as the case may be.

                  10.6  Tag-Along  Right.  (a)  Subject  to  the  provisions  of
paragraph  (d)  hereof,  neither  TDS nor  Aerial  shall  enter  into a  binding
agreement with a third party to consummate a Disposition Transaction unless each
Sonera  Holder is given the  opportunity  to sell to the third party all but not
less than all of such Sonera Holders' AOC Shares and Aerial Shares for which any
AOC  Shares  may  have  been  exchanged,  such  sale to be  concurrent  with the
consummation of the Disposition

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<PAGE>



Transaction,  at the same  price per share  (assuming  any such AOC  Shares  are
converted to Aerial Shares) and on  substantially  the same terms and conditions
as are  obtained  by TDS or  Aerial,  as the  case may be,  in such  Disposition
Transaction.

                  (b) In the event the right  provided in this  Section  10.6 is
exercised,  each Sonera Holder agrees to take all reasonable  steps necessary to
enable such holder to comply with the provisions of this Section 10.6, including
executing  and  performing  a purchase  and sale,  merger or other  agreement on
substantially  the same  terms  as TDS or  Aerial,  as the case may be.  TDS and
Aerial,  on the one hand, and Sonera, on the other hand, each agree to make full
disclosure to the other  concerning the details of any  relationship or dealings
it may have with the other party to the proposed Disposition  Transaction.  Each
of TDS and Aerial,  as the case may be, agrees to keep Sonera advised in writing
of,  and  consult  on a  timely  basis  with  Sonera  concerning,  any  proposed
Disposition  Transaction  with respect to which any Sonera  Holder has exercised
the right provided in this Section 10.6.

                  (c) The right provided by this Section 10.6 shall be exercised
by each  Sonera  Holder by giving a written  notice of such  exercise  to TDS or
Aerial,  as  applicable,  within 15 days after  receipt by such Sonera Holder of
written  notice  from  TDS or  Aerial,  as the  case  may be,  of such  proposed
Disposition Transaction,  which written notice from TDS or Aerial to such Sonera
Holder  shall  set forth in  reasonable  detail  the  identity  of the  proposed
transferee,  the proposed  purchase  price,  terms of payment and other material
terms of the proposed Disposition Transaction. Each Sonera Holder that exercises
such right shall thereafter be obligated to sell to such third party all (but

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not less than all) of its AOC  Shares  and any  Aerial  Shares for which any AOC
Shares may have been exchanged and TDS or Aerial,  as the case may be, shall not
consummate the proposed Disposition Transaction with the third party unless such
third party also acquires all of the AOC Shares, and any Aerial Shares for which
any AOC  Shares  have  been  exchanged,  that  are  held by each  Sonera  Holder
exercising such right.

                  (d) The  tag-along  right  provided by this Section 10.6 shall
terminate  in the event that (i) any Sonera  Holder  disposes  of any  Purchased
Shares (or any of the  Aerial  Shares  for which  such  Purchased  Shares may be
exchanged) or issues a Derivative and (ii) at any time  thereafter the Aggregate
Converted Percentage is less than 7.9%.

                  10.7 Effect of Transfer of Control of Sonera. (a) In the event
that  Sonera  enters  into,  or  the  shareholders  of  Sonera  authorize,   any
transaction  providing  for a  reorganization,  merger,  consolidation  or other
combination of Sonera with or into any other Person, or for the sale, assignment
or other disposition of all or substantially all of Sonera's assets to any other
Person,  Sonera  shall give  written  notice to TDS and Aerial of such  proposed
transaction,  which notice shall describe the  transaction in reasonable  detail
and identify the other party to it (the "Sonera  Transaction  Notice").  If such
Person, or any other Person directly or indirectly in control of such Person, is
a Competitor and TDS or Aerial determines in its reasonable  judgement that such
competition  is material,  TDS or Aerial  shall have the right to serve  written
notice (an "Event Notice") on Sonera within 30 days of its receipt of the Sonera
Transaction  Notice that it intends to invoke the provisions of Section  10.7(b)
hereof with respect to such proposed transaction. Both TDS

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and  Aerial  shall be  deemed  to have  consented  to any  proposed  transaction
described in a Sonera  Transaction Notice if (i) neither TDS nor Aerial gives an
Event Notice to Sonera within 30 days of its receipt of such Sonera  Transaction
Notice,  and (ii) such proposed  transaction is consummated  within 12 months of
the date of such Sonera  Transaction  Notice.  Sonera hereby agrees that it will
not enter into any transaction of the type  contemplated by this Section 10.7(a)
unless  the other  Person  party to such  transaction  agrees to be bound by the
provisions of this Section 10.7.

                  (b) If either TDS or Aerial  timely  gives an Event  Notice to
Sonera,  then  Sonera  shall use its  reasonable  best  efforts to  negotiate  a
Transfer  of all of the AOC  Shares  owned by Sonera  and each of its  Permitted
Affiliate Transferees to another Person reasonably acceptable to TDS and Aerial,
such sale to be  consummated  no later than six months  after the closing of the
transaction that was the subject of the Sonera Transaction  Notice. In the event
that no such  Transfer  shall occur prior to the end of such  six-month  period,
then Sonera and each of its Permitted Affiliate Transferees shall exercise,  and
in the absence  thereof shall be deemed to have  exercised,  the Equity Purchase
Election  upon the last day of such  six-month  period.  No  Transfer  by Sonera
pursuant to this Section 10.7 shall be subject to the right of first negotiation
provided for in Section 5.2 hereof and any such Transfer shall be subject to the
provisions of Section 5.3 hereof.

                                   ARTICLE 11
                    CERTAIN COVENANTS OF TDS, AERIAL AND AOC


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                  11.1  General.  From and after the  execution  and delivery of
this Agreement and until such time as the Aggregate  Converted  Percentage shall
be less than 7.9%,  TDS,  Aerial and AOC shall comply in all  material  respects
with the covenants set forth in this Article 11.

                  11.2 Auditors.  Each of TDS (so long as it is domiciled in the
United States), Aerial and AOC shall maintain a system of accounting established
and  administered  in accordance with U.S. GAAP and shall set aside on its books
all such proper  reserves as shall be required by U.S.  GAAP. AOC shall retain a
firm of independent  certified public accountants of recognized  standing (which
may be the auditors of Aerial) to audit and report on AOC's annual  consolidated
balance  sheets and  statements  of  operations,  shareholders'  equity and cash
flows.  All major  accounting  policies and  principles  shall be  determined in
accordance with U.S. GAAP.

                  11.3  Financial and Other  Information.  (a) Each of TDS (with
respect to the Aerial Group),  Aerial and AOC shall prepare annual  consolidated
balance  sheets and  statements  of  operations,  shareholders'  equity and cash
flows,  which shall be prepared in accordance  with U.S. GAAP, set forth in each
case in  comparative  form the figures for the previous  year, and be audited by
the  auditors  referred to in Section  11.2  hereof.  Aerial  shall also prepare
quarterly  unaudited  consolidated  balance sheets and statements of operations,
shareholders'  equity and cash flows for itself and its Subsidiaries,  certified
by its chief  financial  officer or chief  executive  officer  and  prepared  in
accordance  with U.S. GAAP,  setting forth in each case in comparative  form the
same figures for the  comparable  period of the previous  year and, in addition,
year-to-date figures. TDS,

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Aerial or AOC, as applicable,  shall furnish to Sonera the following information
within the times specified:

                  (i) as  soon as  practicable  after  the  end of  each  fiscal
         quarter,  and  in any  event  within  50  days  thereafter,  all of the
         financial  information  relating to Aerial, AOC or the Aerial Group, as
         applicable, referred to herein,

                  (ii) as soon as practicable after the end of each fiscal year,
         and in  any  event  within  100  days  thereafter,  all  of the  annual
         financial  information  relating to Aerial, AOC or the Aerial Group, as
         applicable, referred to herein, and

                  (iii) on a regular  and  timely  basis,  such  other  standard
         monthly  management,  operational and financial reports and information
         relating to Aerial,  AOC or the Aerial Group, as applicable,  as Sonera
         may reasonably request.

         (b)  Sonera  shall  have  the  right  to  carry  out an  audit  (by its
independent  auditor)  once each year to determine  compliance by Aerial and AOC
with the allocation of credits,  fees,  charges and expenses in accordance  with
the  terms  of  the  Intercompany   Agreements  or  Intercompany   Policies,  as
applicable, and the Aerial Group Allocation Procedures. Each such audit shall be
at Sonera's  sole cost and expense  unless it is  determined  that the aggregate
allocations of fees, charges and expenses (net of any credits) made with respect
to AOC exceeded the  aggregate of such  allocations  (net of any credits)  which
should have been made in accordance with the Intercompany Agreements or

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Intercompany Policies, as applicable, and the Aerial Group Allocation Procedures
by more  than  10%,  in which  event  the cost of such  audit  shall be borne by
Aerial.

                  11.4 No  Adverse  Actions.  TDS,  Aerial  and AOC agree  that,
except (a) with the prior written consent of Sonera,  (b) in connection with the
transactions  contemplated  by the TDS Proxy  Statement,  or (c) as  required or
permitted by the terms of their respective charters or by-laws,  this Agreement,
the  Joint  Venture  Agreement,   the  Registration  Rights  Agreement,  or  any
Intercompany  Agreement,  they will not take any action,  or cause or permit any
Subsidiary to take or omit to take any action,  which action or omission to take
action could  reasonably be expected to (i) have a material  adverse effect upon
the rights of Sonera (A) provided in this Agreement, the Joint Venture Agreement
or the  Registration  Rights  Agreement,  or (B)  provided  in such  charters or
by-laws, (ii) authorize or permit any Subsidiary of TDS other than Aerial or its
Subsidiaries  to acquire an FCC license to provide B-PCS  services or to acquire
control of any entity  that has such a  license,  except to the extent  that any
B-PCS  services to be so provided are  incidental  to the business of such other
TDS Subsidiary and not competitive  with any services  provided by Aerial or any
of its Subsidiaries,  or (iii) effect a fundamental  change in the nature of the
business  carried  on by  Aerial  and AOC from that of  constructing,  owning or
managing and operating a B-PCS services business and providing related services.

                  11.5 Performance of Intercompany  Agreements and Policies. (a)
TDS and Aerial agree that they will (i) duly and timely perform their respective
obligations  under each  Intercompany  Agreement  in  accordance  with its terms
(subject to any amendment, modification or waiver with

                                     - 83 -

<PAGE>



respect  thereto  in  accordance  with  the  terms  of such  agreement  and this
Agreement),  except in respects  that are not  material  and which would not, in
accordance  with the terms thereof,  give rise to the right to claim a breach or
default thereunder and (ii) not terminate,  (except in accordance with its terms
or Section  11.5(b)  hereof) amend or modify any  Intercompany  Agreement in any
manner materially adverse to Aerial or its Subsidiaries  without the approval of
a majority of the independent directors of Aerial. TDS agrees to and does hereby
consent  to the  execution  by  Aerial  and  AOC of  this  Agreement  and to the
performance by them of their  respective  obligations  hereunder,  including the
issuance of equity by Aerial or AOC in accordance  with the  provisions  hereof.
Aerial agrees that it will continue to allocate among AOC, its Subsidiaries, and
each limited liability  company formed pursuant to the Joint Venture  Agreement,
all  credits,  fees,  charges  and  expenses  related  to,  arising  under or in
connection with the Intercompany  Agreements in accordance with the Aerial Group
Allocation Procedures.

                  (b) Sonera  acknowledges that TDS and Aerial intend to replace
one or more  Intercompany  Agreements  with a related  Intercompany  Policy upon
consummation  of the Aerial Merger.  In the event that one or more  Intercompany
Agreements  are so replaced,  then the  provisions  of Section  11.5(a) shall be
deemed to apply to such  Intercompany  Policy,  rather than to the  Intercompany
Agreement so replaced,  as if such  Intercompany  Policy  constituted  a binding
contractual obligation between TDS and Aerial.

                  (c) TDS  agrees  to and does  hereby  waive its  rights  under
Section  3.01 of the Exchange  Agreement  to  subscribe to a proportion  of each
issuance of Aerial Common Shares or

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<PAGE>



other  voting  securities  of  Aerial,  or any  securities  convertible  into or
exchangeable for, or carrying a right to subscribe to or acquire,  Aerial Common
Shares or other  voting  securities  of Aerial,  to the extent,  and only to the
extent that such waiver is  necessary  to permit the  issuance of Aerial  Common
Shares to Sonera  Holders  pursuant to and in accordance  with the provisions of
Article 7 or Article 8 of this  Agreement.  TDS further  agrees that it will not
assign  (pursuant to Section 3.04 of the  Exchange  Agreement)  its rights under
Section 3.01 of the  Exchange  Agreement to any Person  without  requiring  such
Person to provide an identical waiver.

                  11.6  Reservation of Aerial Shares.  (a) At all times prior to
the  earlier to occur of the Aerial  Merger or the  Distribution,  Aerial  shall
reserve and keep available,  free of pre-emptive or other  subscription  rights,
out of its authorized but unissued Aerial Common Shares, or out of Aerial Common
Shares  held in its  treasury,  solely for the  purpose of  performance  of this
Agreement, such number of Aerial Common Shares as shall be deliverable by Aerial
from time to time hereunder.

                  (b) At all times  after  the  earlier  to occur of the  Aerial
Merger  or the  Distribution,  TDS shall  reserve  and keep  available,  free of
pre-emptive  or other  subscription  rights,  out of its authorized but unissued
Aerial Group Shares,  solely for the purpose of performance  of this  Agreement,
such number of Aerial Group Shares as shall be  deliverable  by TDS from time to
time hereunder.


                                     - 85 -

<PAGE>



                  (c) If and so long as the Aerial Shares shall be listed on any
national  securities  exchange,  Aerial or TDS,  as the case may be,  shall,  if
permitted by the rules of such exchange,  list and keep listed on such exchange,
upon official notice of issuance,  all Aerial Shares issuable hereunder upon the
exchange of AOC Shares.  All Aerial  Shares  which may be issued or  transferred
upon any exchange  hereunder shall,  upon issuance  thereof,  be validly issued,
fully paid and non-assessable.

                  11.7 Intra-Corporate Transactions. TDS agrees that it will not
take any action to cause  Aerial to fail to perform its  obligations  under this
Agreement or any Intercompany Agreement. TDS agrees that, in the event it causes
or permits  Aerial or AOC to enter into any  agreement  providing for a business
combination  transaction  other  than the  Aerial  Merger,  whether  by  merger,
consolidation,  transfer of equity,  assignment of assets or otherwise, with TDS
or any Affiliate of TDS, then (i) if such  transaction is consummated and Aerial
or AOC, as applicable,  continues to be operated as a separate corporate entity,
all of the contractual rights of Sonera and its Permitted Affiliate  Transferees
under  the  terms of this  Agreement  shall  survive  the  consummation  of such
transaction  and  shall  continue  in full  force and  effect,  and (ii) if such
transaction  is  consummated  and the business of Aerial is combined  with other
businesses  within the same corporate  entity other than Aerial or AOC, then (A)
all of the contractual rights of Sonera and its Permitted Affiliate  Transferees
under  the  terms of this  Agreement  shall  survive  the  consummation  of such
transaction  as  obligations  of the  surviving  entity,  and (B) Sonera will be
provided two seats on the Board of Directors of the surviving entity, so long as
it has an  interest  in the  combined  equity of such  entity,  on the six month
anniversary of the closing of such transaction and thereafter, of at least 5%

                                     - 86 -

<PAGE>



(determined  as if all securities  owned by Sonera and its  Affiliates  that are
convertible into or exchangeable for equity  securities of such surviving entity
had been so converted or exchanged,  regardless of whether such  securities  are
then convertible or exchangeable).

                  11.8 Performance of Registration  Rights Agreement and Waiver.
(a) As a condition  precedent to the consummation of the Aerial Merger,  TDS and
Aerial  agree that Aerial shall assign to TDS, and TDS shall assume from Aerial,
the Registration  Rights Agreement,  including all of the rights and obligations
of Aerial  thereunder,  and the  obligations of Aerial under Sections 5.3(d) and
5.5(b)(ii) hereof. Upon such assignment,  all references to "the Company" in the
Registration  Rights  Agreement and "Aerial" in the referenced  sections of this
Agreement  shall be  deemed  to  refer  to TDS  rather  than to  Aerial  and the
references to "common  stock" in the  definition of "Common  Stock" set forth in
Section 1.1 of the Registration Rights Agreement shall be deemed to refer to the
Aerial Group Shares of TDS rather than to the common stock of Aerial.

                  (b)  Prior  to  the  execution  of  this   Agreement  and  the
Registration Rights Agreement, TDS and Aerial entered into a Registration Rights
Agreement, dated as of April 15, 1996 (the "TDS Registration Rights Agreement"),
pursuant to which Aerial granted certain registration rights to TDS with respect
to the  securities  of  Aerial  held by TDS.  TDS and  Aerial  hereby  waive the
application  of Section  8(h) of the TDS  Registration  Rights  Agreement to any
"Piggyback  Registration"  (as defined in the Registration  Rights Agreement) by
Sonera pursuant to Section 3 of the Registration  Rights  Agreement,  subject to
the terms, conditions and restrictions set

                                     - 87 -

<PAGE>



forth in the Registration  Rights Agreement governing Sonera's right to exercise
a Piggyback Registration.

                  11.9  Operation  in  Ordinary  Course.  TDS,  Aerial  and  AOC
acknowledge  that Sonera has acquired the AOC Shares with the intention  that it
will become a security  holder of AOC with the rights  provided to Sonera by the
Purchase Agreement,  the Registration Rights Agreement and this Agreement.  TDS,
Aerial and AOC agree that  Aerial  will,  and will  cause its  Subsidiaries  to,
conduct their  respective  businesses in the ordinary normal course thereof.  In
furtherance and not in limitation of the preceding sentence,  Aerial agrees that
substantially  all of the  material  assets  reflected  from time to time on the
consolidated balance sheets of Aerial and its subsidiaries and used or useful in
connection  with  the  business  of  operating  Aerial  shall be owned by AOC or
subsidiaries  of AOC and Aerial will use its reasonable best efforts to transfer
to AOC or its  subsidiaries,  on or before  December 31, 1998,  any and all such
assets  that  are  not  owned  by AOC or its  subsidiaries  on the  date of this
Agreement.  TDS,  Aerial and AOC further  covenant  and agree that all  material
assets used or useful in connection  with the business of operating  Aerial that
are acquired in the future shall be acquired by AOC or its  subsidiaries  or, if
acquired by Aerial,  shall be  transferred to AOC or its  subsidiaries  promptly
after such  acquisition.  Aerial and AOC also covenant and agree that if, at any
time after the date of this Agreement, Aerial receives proceeds from any loan or
from the sale of any debt  instrument,  Aerial shall  promptly upon such receipt
advance the full amount of such  proceeds  to AOC or its  subsidiaries,  and AOC
shall borrow such proceeds,  or shall cause one or more of its  subsidiaries  to
borrow such proceeds, in any case at the same interest rate and on substantially
the same terms as those on which Aerial has incurred such debt.

                                     - 88 -

<PAGE>




                                   ARTICLE 12
                                  MISCELLANEOUS

                  12.1 Expenses. Each party shall bear its own expenses incident
to  the  negotiation,  preparation,   authorization  and  consummation  of  this
Agreement  and the  transactions  contemplated  hereby,  including  all fees and
expenses of its counsel and  accountants,  whether or not such  transactions are
consummated.

                  12.2  Equitable  Remedies.   The  parties  hereto  agree  that
irreparable  damage would occur in the event that any of the  provisions of this
Agreement  were not  performed  in  accordance  with the  specific  terms of the
provisions or were otherwise breached. It is accordingly agreed that the parties
shall be entitled to an injunction or  injunctions  to prevent  breaches of this
Agreement and to enforce  specifically  the terms and  provisions  hereof in any
court of the  United  States or any state  having  jurisdiction,  this  being in
addition  to any other  remedy to which they are  entitled  at law or in equity.
Each party  agrees  that it will not  assert,  as a defense  against a claim for
specific  performance  or other  equitable  remedy,  that the party seeking such
equitable remedy has an adequate remedy at law.

                  12.3  Notices.  All notices,  claims and other  communications
hereunder shall be in writing and shall be given by hand delivery, facsimile, or
overnight air courier guaranteeing next day delivery:

                                     - 89 -

<PAGE>



                  (a)      if to TDS, at:

                           Telephone and Data Systems, Inc.
                           30 North LaSalle Street
                           Suite 4000
                           Chicago, Illinois  60602
                           Attention:  Mr. LeRoy T. Carlson, Jr.
                           Phone:           (312) 630-1900
                           Fax:             (312) 630-9299

                  with a copy (which shall not constitute notice) to:

                           Aerial Communications, Inc.
                           8410 West Bryn Mawr Avenue
                           Suite 1100
                           Chicago, Illinois  60631
                           Attention:  Mr. Donald W. Warkentin
                           Phone:           (773) 399-4145
                           Fax:             (773) 399-7997

                  with a copy (which shall not constitute notice) to:

                           Sidley & Austin
                           One First National Plaza
                           42nd Floor - SW
                           Chicago, Illinois  60603
                           Attention:  Michael G. Hron, Esq.
                           Phone:           (312) 853-2030
                           Fax:             (312) 853-7036

                  (b)      if to Aerial or AOC, at:

                           Aerial Communications, Inc.
                           8410 West Bryn Mawr Avenue
                           Suite 1100
                           Chicago, Illinois  60631
                           Attention:  Mr. Donald W. Warkentin
                           Phone:           (773) 399-4145
                           Fax:             (773) 399-7997


                                     - 90 -

<PAGE>



                  with a copy (which shall not constitute notice) to:

                           Telephone and Data Systems, Inc.
                           30 North LaSalle Street
                           Suite 4000
                           Chicago, Illinois  60602
                           Attention:  Mr. LeRoy T. Carlson, Jr.
                           Phone:           (312) 630-1900
                           Fax:             (312) 630-9299

                  with a copy (which shall not constitute notice) to:

                           Sidley & Austin
                           One First National Plaza
                           42nd Floor - SW
                           Chicago, Illinois  60603
                           Attention:  Michael G. Hron, Esq.
                           Phone:           (312) 853-2030
                           Fax:             (312) 853-7036

                  (c)      if to Sonera, at:

                           Sonera Ltd.
                           P.O. Box 106
                           FIN-00051-TELE
                           Teollisuuskatu 15, HELSINKI
                           Attention:  Maire Laitinen, Esq.
                           Phone:           011-35-8-2040-3641
                           Fax:             011-35-8-2040-3414

                  with a copy (which shall not constitute notice) to:

                           Patton Boggs, L.L.P.
                           2550 M. Street, N.W.
                           Washington, D.C.  20037-1350
                           Attention:  Richard M. Stolbach, Esq.
                           Phone:           (202) 457-6324
                           Fax:             (202) 457-6315


or at such other address as any party may from time to time furnish to the other
parties by a notice  given in  accordance  with the  provisions  of this Section
12.3. All such notices and communications

                                     - 91 -

<PAGE>



shall be  deemed  to have  been duly  given at the time  delivered  by hand,  if
personally delivered;  when receipt confirmed, if sent by facsimile;  and on the
next Business Day after timely delivery to the courier,  if sent by an overnight
air courier service guaranteeing next day delivery.

                  12.4  Entire  Agreement.  This  Agreement,  the Joint  Venture
Agreement  and the  Registration  Rights  Agreement,  together with the EXHIBITS
annexed hereto and thereto,  contain the entire  understanding among the parties
hereto  concerning  the  subject  matter  hereof and this  Agreement  may not be
changed,  modified,  altered or  terminated  except by an  agreement  in writing
executed  by the  parties  hereto.  Any waiver by any party of any of its rights
under this Agreement or of any breach of this  Agreement  shall not constitute a
waiver of any other rights or of any other or future breach.

                  12.5 Remedies Cumulative. Except as otherwise provided herein,
each or any of the rights and remedies in this Agreement  provided,  and each or
any of the rights and remedies  allowed at law and in equity in like case, shall
be cumulative, and the exercise of one right or remedy shall not be exclusive of
the right to exercise or resort to any or any other rights or remedies  provided
in this Agreement or at law or in equity.

                  12.6  Governing  Law.  This  Agreement  shall be  construed in
accordance  with and subject to the laws and  decisions of the State of Delaware
applicable to contracts made and to be performed entirely therein.


                                     - 92 -

<PAGE>



                  12.7  Counterparts.  This Agreement may be executed in several
counterparts   hereof,   and  by  the  different   parties  hereto  on  separate
counterparts  hereof, each of which shall be an original;  but such counterparts
shall together constitute one and the same instrument.

                  12.8 Waivers.  No provision in this Agreement  shall be deemed
waived  except by an  instrument  in writing  signed by the party  waiving  such
provision.

                  12.9  Successors and Assigns.  This Agreement shall be binding
upon and inure to the  benefit of the  parties  hereto  and to their  respective
permitted successors and assigns;  provided,  however, that, except as otherwise
expressly set forth in this Agreement, neither the rights nor the obligations of
either party may be assigned or delegated  without the prior written  consent of
the other parties;  provided further, that the Aerial Merger shall not be deemed
to effect an assignment  within the meaning of this Section  12.9;  and provided
further,  that Sonera shall have the right to assign its rights and  obligations
under this  Agreement to any  wholly-owned  Subsidiary of Sonera,  provided that
Sonera shall irrevocably and  unconditionally  guarantee the performance by such
Subsidiary of all of the obligations of Sonera hereunder.

                  12.10 Further Assurances. Sonera shall, at the request of TDS,
Aerial or AOC,  and TDS,  Aerial and AOC shall,  at the request of Sonera,  from
time to time, execute and deliver such other assignments, transfers, conveyances
and other  instruments  and  documents  and do and  perform  such other acts and
things as may be  reasonably  necessary  or  desirable  for  effecting  complete
consummation of this Agreement and the transactions herein contemplated.

                                     - 93 -

<PAGE>



                  12.11 Information for Governmental  Filings.  Sonera agrees to
provide such  information  regarding itself and its Affiliates as may reasonably
be requested  by TDS,  Aerial or AOC,  for  inclusion in such  documents as TDS,
Aerial or AOC,  as the case may be,  may from time to time be  required  to file
with the Securities and Exchange  Commission,  the FCC, or other agencies of the
United States  government.  The information  provided by Sonera for inclusion in
such  documents  will not contain any material  misstatement  of fact or omit to
state  any  material  fact  necessary  to make the  statements,  in light of the
circumstances under which they are made, not misleading. All statements included
in the TDS Proxy Statement and such other documents  relating to Sonera shall be
subject  to the  approval  of  Sonera,  such  approval  not  to be  unreasonably
withheld.

                  12.12  Disclosures.  (a)  Confidentiality.  Sonera and each of
TDS,  Aerial and AOC  acknowledge and confirm in connection with the negotiation
of this  Agreement  and the  execution  hereof,  during the period from the date
hereof  through  the date that this  Agreement  remains in effect,  the  parties
hereto will have furnished to one another certain materials,  information,  data
and other  documentation  ("Disclosures")  concerning their business,  financial
condition and operations  which are  proprietary  and  confidential.  Each party
acknowledges  the party  making  such  Disclosures  considers  them  secret  and
confidential and asserts a proprietary interest therein. Accordingly, Sonera, on
the one hand, and each of TDS, Aerial and AOC, on the other hand,  covenants and
agrees that it shall  maintain all  Disclosures  made by another party in strict
confidence  and shall not use such  Disclosures  for its own benefit or disclose
them  to  third  parties,  except  to  its  agents,  representatives,   bankers,
investment   bankers,   counsel  and  employees   involved  in  evaluating   the
transactions  contemplated  by this Agreement and informed of the requirement of
confidentiality,

                                     - 94 -

<PAGE>



or as otherwise  required by law (including the  requirement of TDS or Aerial to
disclose such terms under the federal  securities laws or under the rules of any
securities  exchange on which its  securities  are  listed,  and  including  the
requirement  of Sonera or any of its Affiliates to disclose such terms under the
securities laws of Finland or other applicable jurisdiction).

                  (b) Public  Announcements.  No public announcement with regard
to the  transactions  contemplated  hereby or the material terms hereof shall be
issued by any party hereto without the mutual prior written consent of the other
parties,  except to the extent  that the  parties are unable to agree on a press
release  and legal  counsel  for one  party is of the  opinion  that such  press
release is required by law.

                  (c)  Non-Confidential  Information.  This Agreement  shall not
restrict any party hereto from using  information  already known to it, to which
it is entitled under existing agreements, or information generally in the public
domain or any information received from a third party with a right to possess or
make disclosure thereof.

                  12.13  Termination.  This  Agreement may be terminated and the
transactions contemplated hereby may be abandoned, without further obligation of
TDS, Aerial, AOC or Sonera at any time by mutual written consent duly authorized
by the boards of directors of TDS, Aerial, AOC and Sonera.


                                     - 95 -

<PAGE>



                  12.14  Disputes.  (a)  General.  The parties  agree to address
disagreements  and disputes  arising out of or related to this  Agreement or the
breach hereof through the procedures set forth in this Section 12.14.

                  (b) Negotiation  Procedure.  (i) TDS, Aerial and AOC (the "TDS
Parties"),  on the one hand, and Sonera,  on the other hand, shall designate one
or more  employees  or  representatives  who  will be the  initial  contact  for
resolving  disputes that may arise under this  Agreement  that do not involve an
amount in excess of $50,000.  The TDS Parties and Sonera  shall first raise such
disputes with a designated  employee or  representative  of the other party. The
designated  employees  shall work  together to resolve the  relevant  issue in a
manner that meets the interests of both the TDS Parties and Sonera, or until the
issue is referred to designated  officers of the parties as set forth in Section
12.14(b)(ii)  hereof.  Any disputes  that involve an amount in excess of $50,000
shall be  referred  to the  designated  officers  of the parties as set forth in
Section 12.14(b)(ii) hereof.

                  (ii) The TDS Parties and Sonera  shall also  designate  one or
more  officers who will review (A) disputes  that involve an amount in excess of
$50,000,  and (B) disputes that the  designated  employees are unable to resolve
pursuant  to  Section  12.14(b)(i)  hereof.  Any  matter  not  resolved  by such
designated employees within 30 days after the date on which a party hereto first
notifies a  designated  employee  of the other  party  shall be referred to such
designated officers for resolution.  The designated officers shall work together
to resolve the disputes so referred to them in a manner that meets the interests
of both the TDS Parties and Sonera,  either until such agreement is reached,  or
until an impasse is  declared  by either  the TDS  Parties or Sonera;  provided,
however,

                                     - 96 -

<PAGE>



that an impasse  shall not be declared by either the TDS Parties or Sonera prior
to the  fifteenth  day after  such  dispute  has  first  been  referred  to such
designated  officers.  Notice of  declaration  of any impasse  shall be given in
accordance with Section 12.3 hereof.

                  (iii) The employees and officers  initially  designated by the
TDS Parties and Sonera for purposes of this Section  12.14 are listed on EXHIBIT
12.14(b)(iii)  annexed  hereto.  Parties may change such  designation  by giving
notice of such change pursuant to Section 12.3 hereof.

                  (iv) Any resolution of a dispute by the  designated  employees
or representatives  pursuant to Section  12.14(b)(i) hereof or by the designated
officers pursuant to Section  12.14(b)(ii)  hereof shall be in writing signed by
such persons on behalf of the  parties.  Notwithstanding  any  provision of this
Section  12.14,  no  resolution  of  any  dispute  by any  designated  employee,
representative  or officer  shall  constitute  on  amendment  of this  Agreement
without the approval of the respective boards of directors of each party hereto.

                  (c)  Unresolved  Disputes.  The  parties  shall be entitled to
exercise or resort to any and all rights and remedies provided in this Agreement
or at law or in equity with  respect to any  controversy  or claim not  resolved
through the procedures set forth above.

                  (d)  Jurisdiction;  Consent to Service  of  Process.  (i) Each
party hereby irrevocably  consents and submits to the jurisdiction of the United
States District Court for the District of Delaware and any court of the State of
Delaware, in any action, suit or proceeding arising out of,

                                     - 97 -

<PAGE>



resulting from or relating to this  Agreement,  and agrees that any such action,
suit or  proceeding  shall  be  brought  only in such  courts  (and  waives  any
objection  based on forum non  conveniens  or any  objection to venue  therein);
provided,  however,  that such consent to jurisdiction is solely for the purpose
referred  to in this  Section  12.14(d)  and shall not be deemed to be a general
submission  to the  jurisdiction  of said courts or the State of Delaware  other
than for such purpose.

                  (ii) Sonera hereby irrevocably  appoints The Corporation Trust
Company,  at its office at 1209  Orange  Street,  Wilmington,  Delaware,  United
States of  America,  its lawful  agent and  attorney  to accept and  acknowledge
service of any process against it in any action,  suit or proceeding arising out
of, resulting from or relating to this Agreement, and upon whom such process may
be  served,  with the  same  effect  as if it were a  resident  of the  State of
Delaware,  and had been lawfully served with such process in such  jurisdiction,
and waives all claim of error by reason of such  service,  provided  that in the
case of any service upon such agent and attorney,  the Aerial Parties shall also
deliver a copy  thereof to Sonera at the address and in the manner  specified in
Section  12.3  hereof.  In the event  that such  agent and  attorney  resigns or
otherwise  becomes  incapable of acting as such, Sonera will appoint a successor
agent and  attorney in  Wilmington,  Delaware,  reasonably  satisfactory  to the
Aerial Parties,  with like powers,  or if Sonera fails to make such appointment,
Sonera hereby  authorizes  the Aerial  Parties to appoint such agent for Sonera.
Sonera  shall pay the annual fee due to The  Corporation  Trust  Company or such
successor agent for acting in such capacity;  provided,  however, that if Sonera
shall fail to make such payment, then the Aerial Parties shall have the right to
do so.


                                     - 98 -

<PAGE>



                  12.15 No Claim of Immunity.  Sonera agrees that, to the extent
that it or any of its property, its Affiliates, or property of its Affiliates is
or becomes  entitled at any time to any immunity,  on the grounds of sovereignty
or  otherwise,  based  upon  its  status  as an  agency  or  instrumentality  of
government,  from any  arbitration,  legal  action,  suit or  proceeding or from
setoff or counterclaim  relating to this Agreement from the  jurisdiction of any
arbitrator or competent court, from service of process, from attachment prior to
judgment,  from  attachment  in aid of execution of a judgment,  from  execution
pursuant to a judgement or arbitration award, or from any other legal process in
any jurisdiction,  it, for itself, its Affiliates,  its property and that of its
Affiliates,  expressly,  irrevocably and unconditionally  agrees not to plead or
claim,  any such immunity  with respect to such matters  arising with respect to
this  Agreement or the subject  matter hereof  (including any obligation for the
payment of money).

                  12.16 Remedies. In addition to any other remedies which may be
available to TDS or Aerial at law or in equity,  Sonera agrees that each of TDS,
Aerial and AOC shall have no obligation to honor Transfers of AOC Shares, Aerial
Common  Shares,  or  other  securities  of  Aerial,  to  Sonera  or  any  of its
Affiliates, which would cause Sonera or any of its Affiliates to own AOC Shares,
Aerial  Common  Shares  or other  securities  of  Aerial  in  violation  of this
Agreement,  any such Transfers shall be void and of no effect,  and Aerial shall
be entitled to instruct any transfer agent to refuse to honor such transfers.

                  12.17  Severability.  In  the  event  any  provision  of  this
Agreement  is found to be  invalid  or  unenforceable  in whole or in part,  the
remaining provisions of this Agreement nevertheless

                                     - 99 -

<PAGE>



shall be binding and the invalid or unenforceable provision shall be replaced by
a valid and enforceable  provision which comes closest to the intent or economic
effect of the provision to be replaced.
                                    * * * * *
























                                     - 100 -

<PAGE>



                  IN WITNESS WHEREOF, the parties hereto have duly executed this
Agreement as of the date first above written.

                                          TELEPHONE AND DATA SYSTEMS, INC.

                                              

                                          By:   /s/ LeRoy T. Carlson, Jr.
                                                --------------------------------
                                                LeRoy T. Carlson, Jr. 
                                                President

                                          AERIAL COMMUNICATIONS, INC.


                                          By:   /s/ Donald W. Warkentin  
                                                --------------------------------
                                                Donald W. Warkentin 
                                                President

                                          AERIAL OPERATING CO., INC.


                                          By:   /s/ Donald W. Warkentin  
                                                --------------------------------
                                                Donald W. Warkentin 
                                                President

                                          SONERA LTD.


                                          By:    /s/ Aulis Salin 
                                                 -------------------------------
                                          Name:  Aulis Salin
                                                 -------------------------------
                                          Title: President and CEO
                                                 -------------------------------

                     SIGNATURE PAGE TO INVESTMENT AGREEMENT,
                         DATED AS OF SEPTEMBER 8, 1998,
                     AMONG TELEPHONE AND DATA SYSTEMS, INC.,
                  AERIAL COMMUNICATIONS, INC., AERIAL OPERATING
                            CO., INC. AND SONERA LTD.



























                                     

<PAGE>



                                                                    EXHIBIT 99.3

                                                                  EXECUTION COPY







                          REGISTRATION RIGHTS AGREEMENT



                          dated as of September 8, 1998



                                     between



                           AERIAL COMMUNICATIONS, INC.


                                       and


                                   SONERA LTD.






<PAGE>



                                TABLE OF CONTENTS

                                                                           Page



Section 1.  Definitions and Usage............................................2
            ---------------------
            
Section 2.  Demand Registration..............................................8
            -------------------

Section 3.  Piggyback Registration..........................................12
            ---------------------- 

Section 4.  Registration Procedures.........................................13
            -----------------------

Section 5.  Holder's Obligations............................................18
            --------------------

Section 6.  Expenses of Registration........................................19
            ------------------------

Section 7.  Indemnification; Contribution...................................20
            -----------------------------

Section 8.  Holdback........................................................26
            -------- 

Section 9.  Amendment, Modification and Waivers; Further Assurances.........27
            -------------------------------------------------------

Section 10. Assignment and Assumption.......................................27
            ------------------------- 

Section 11. Miscellaneous...................................................29
            -------------

                                       -i-

<PAGE>



                          REGISTRATION RIGHTS AGREEMENT


                  REGISTRATION RIGHTS AGREEMENT (this "Agreement"),  dated as of
September 8, 1998, between AERIAL  COMMUNICATIONS,  INC., a Delaware corporation
(the "Company"),  and SONERA LTD., a limited  liability  company organized under
the laws of the  Republic of Finland and  formerly  known as Sonera  Corporation
(the "Holder").

                                    RECITALS
                                    --------

                  WHEREAS,  the parties  hereto  hereby  desire to set forth the
Holder's rights and the Company's  obligations to cause the  registration of the
Registrable Securities pursuant to the Securities Act;

                  NOW,  THEREFORE,  in  consideration  of the  investment by the
Holder in the AOC  Common  Stock  pursuant  to the  Purchase  Agreement  and the
Investment Agreement and for other good and valuable consideration,  the receipt
and  sufficiency of which are hereby  acknowledged,  the parties hereto agree as
follows:



<PAGE>




                  Section 1.  Definitions and Usage.  As used in this Agreement:

                  1.1.  Definitions.

                  Agent.  "Agent" means the principal placement agent on an 
agented placement of securities of the Company.

                  AOC Common Stock. "AOC Common Stock" shall mean (i) the common
stock,  par value $0.001 per share, of Aerial Operating Co., Inc.  ("AOC"),  and
(ii)  shares of capital  stock of AOC issued by AOC in respect of or in exchange
for  shares  of such  common  stock in  connection  with any stock  dividend  or
distribution, stock split-up, recapitalization, recombination or exchange by AOC
of shares of such common stock.

                  Commission.  "Commission" shall mean the Securities and 
Exchange Commission.

                  Common Stock.  "Common Stock" shall mean (i) the common stock,
par value $1.00 per share,  of the Company,  and (ii) shares of capital stock of
the Company  issued by the  Company in respect of or in  exchange  for shares of
such common stock in connection with any stock dividend or  distribution,  stock
split-up,  recapitalization,  recombination or exchange by the Company generally
of shares of such common stock.


                                       -2-

<PAGE>



                  Continuously Effective. "Continuously Effective", with respect
to a specified registration statement,  shall mean that it shall not cease to be
effective and available for Transfers of Registrable  Securities  thereunder for
longer  than  either  (i) any ten (10)  consecutive  business  days,  or (ii) an
aggregate  of fifteen  (15)  business  days during the period  specified  in the
relevant provision of this Agreement.

                  Demand Registration.  "Demand Registration" shall have the 
meaning set forth in Section 2.1(a).

                  Exchange Act.  "Exchange Act" shall mean the Securities 
Exchange Act of 1934.

                  Investment Agreement.  "Investment Agreement" means the 
Investment  Agreement,  dated as of September 8, 1998, by and among the Company,
AOC, Telephone and Data Systems, Inc. and the Holder.

                  Person.  "Person"  shall  mean  any  individual,  corporation,
partnership, joint venture, association,  joint-stock company, limited liability
company,  trust,  unincorporated  organization  or government or other agency or
political subdivision thereof.

                  Piggyback Registration.  "Piggyback Registration" shall have 
the meaning set forth in Section 3.1.


                                       -3-

<PAGE>



                  Purchase Agreement.  "Purchase Agreement" shall mean the 
Purchase  Agreement,  dated as of June 1, 1998,  by and among the Company,  AOC,
Telephone and Data Systems, Inc. and the Holder.

                  Purchased Shares.  "Purchased Shares" shall mean the 2,410,482
shares of AOC Common  Stock  initially  acquired  by the Holder  pursuant to the
Purchase Agreement.

                  Register,    Registered    and    Registration.    "Register",
"registered",  and  "registration"  shall  refer to a  registration  effected by
preparing and filing a registration  statement or similar document in compliance
with the  Securities  Act, and the  declaration or ordering by the Commission of
effectiveness of such registration statement or document.

                  Registrable  Securities.  "Registrable  Securities" shall mean
(i) the  Shares  owned by the  Holder on the date of  determination  or (ii) any
securities  of any Person  issued in exchange for or on  conversion of Shares in
any merger or  reorganization  of the Company owned by the Holder on the date of
determination  whether  pursuant to Section 11.8 of the Investment  Agreement or
otherwise;  provided, however, that Registrable Securities shall not include any
securities  which have  theretofore  been  registered  and sold  pursuant to the
Securities Act or which have been sold to the public pursuant to Rule 144 or any
similar rule promulgated by the Commission  pursuant to the Securities Act, and,
provided further, the Company shall have no obligation under Sections 2 and 3 to
register any  Registrable  Securities of the Holder if the Company shall deliver
to the Holder an opinion of counsel  reasonably  satisfactory to such Holder and
its counsel to the effect that the

                                       -4-

<PAGE>



proposed sale or disposition by the Holder of all of the Registrable  Securities
for which  registration  was requested does not require  registration  under the
Securities  Act,  and offers to remove  any and all  Transfer  restrictions  and
legends restricting  Transfer from the certificates  evidencing such Registrable
Securities.

                  Registration Expenses.  "Registration Expenses" shall have the
meaning set forth in Section 6.1.

                  Registration Rights Period. "Registration Rights Period" means
the period  commencing on the fifth  anniversary  hereof and  terminating on the
earliest to occur of (i) the twentieth anniversary hereof, (ii) if the Holder or
any Permitted Affiliate Transferee (as defined in the Investment  Agreement) has
Transferred any Purchased  Shares or any securities  acquired in exchange for or
on  conversion  of such  Purchased  Shares,  then the date, if any, on which the
Holder  and the  Permitted  Affiliate  Transferees,  in the  aggregate,  fail to
maintain  an  Aggregate  Converted  Percentage  (as  determined  pursuant to the
Investment Agreement) equal to at least 5.3%, or (iii) if neither the Holder nor
any Permitted Affiliate  Transferee has Transferred any Purchased Shares, or any
securities  acquired in exchange for or on conversion of such Purchased  Shares,
then  the  date,  if any,  on  which  the  Holder  and the  Permitted  Affiliate
Transferees,   in  the  aggregate,  fail  to  maintain  an  Aggregate  Converted
Percentage equal to at least 2.1%.


                  Securities Act. "Securities Act" shall mean the Securities Act
of 1933.

                                       -5-

<PAGE>



                  Selling Holder. "Selling Holder" shall mean, with respect to a
specified  registration of securities pursuant to this Agreement,  the Holder if
any of the Holder's Registrable Securities are included in such registration.

                  Shares. "Shares" shall mean any or all of the shares of Common
Stock held by the  Holder  that are  acquired  by the  Holder  from the  Company
pursuant to the Investment Agreement,  whether such acquisition by the Holder is
by the  purchase  of Common  Stock or by the  exchange  of AOC Common  Stock for
Common Stock.

                  Transfer.  "Transfer"  shall  mean  and  include  the  act  of
selling, giving, transferring, creating a trust (voting or otherwise), assigning
or otherwise  disposing of to an unaffiliated  third party (other than pledging,
hypothecating  or otherwise  transferring  as security) (and  correlative  words
shall have correlative  meanings);  provided however, that any transfer or other
disposition upon foreclosure or other exercise of remedies of a secured creditor
after an event of default  under or with respect to a pledge,  hypothecation  or
other transfer as security shall constitute a "Transfer".

                  Underwriters' Representative.  "Underwriters'  Representative"
shall  mean  the  managing   underwriter   or,  in  the  case  of  a  co-managed
underwriting,   the  managing   underwriter   designated  as  the  Underwriters'
Representative by the co-managers for the sale of securities of the Company.

                  Violation.  "Violation"  shall have the  meaning  set forth in
Section 7.1.

                                       -6-

<PAGE>



                  1.2. Usage.  (a) References to a Person are also references to
its assigns and  successors  in interest (by means of merger,  consolidation  or
sale of all or substantially all the assets of such Person or otherwise,  as the
case may be).

                  (b) References to Registrable Securities "owned" by the Holder
shall include Registrable Securities beneficially owned by such Person but which
are held of record in the name of a nominee, trustee, custodian, or other agent.

                  (c) References to a document are to it as amended,  waived and
otherwise  modified  from  time to time and  references  to a  statute  or other
governmental rule are to it as amended and otherwise  modified from time to time
(and  references  to any  provision  thereof  shall  include  references  to any
successor provision).

                  (d)  References to Sections are to sections  hereof unless the
context otherwise requires.

                  (e) The  definitions  set forth herein are equally  applicable
both to the  singular and plural forms and the  feminine,  masculine  and neuter
forms of the terms defined.

                  (f) The term "including" and correlative terms shall be deemed
to be followed by "without  limitation" whether or not followed by such words or
words of like import.


                                       -7-

<PAGE>



                  (g)  The  term  "hereof"  and  similar  terms  refer  to  this
Agreement as a whole.

                  (h) The "date of" any notice or request given pursuant to this
Agreement shall be determined in accordance with Section 11.2.


                  Section 2.  Demand Registration.

                  2.1. (a) If at any time during the Registration Rights Period,
the Holder shall make a written  request to the Company to register  Registrable
Securities  then held by the Holder,  the Company  shall cause there to be filed
with the Commission a registration  statement  meeting the  requirements  of the
Securities  Act (a "Demand  Registration")  and the Holder  shall be entitled to
have  included  therein  all  or  such  number  of  such  Holder's   Registrable
Securities, as the Holder shall specify in writing;  provided,  however, that no
request may be made  pursuant to this  Section 2.1 if within  twelve (12) months
prior to the date of such request a  registration  statement in connection  with
either  a  Demand  Registration  pursuant  to this  Section  2.1 or a  Piggyback
Registration  pursuant to Section 3.1 shall have been declared  effective by the
Commission.  Any request made pursuant to this Section 2.1 shall be addressed to
the attention of the  Secretary of the Company,  and shall specify the number of
Registrable  Securities to be  registered,  the intended  methods of disposition
thereof  and that the  request  is for a Demand  Registration  pursuant  to this
Section 2.1(a).


                                       -8-

<PAGE>



                  (b) The Company  shall be entitled to (i)  postpone the filing
of any Demand Registration statement otherwise required to be prepared and filed
pursuant  to this  Section  2.1,  and (ii)  after  effectiveness  of any  Demand
Registration  statement prepared and filed pursuant to this Section 2.1, suspend
the use of such Demand Registration  statement and require the Selling Holder to
suspend sales pursuant to the prospectus  contained therein, if, in either case,
the  Board  determines,   in  its  good  faith  reasonable  judgment  (with  the
concurrence of the managing underwriter, if any), that such registration and the
Transfer  of  Registrable  Securities   contemplated  thereby  would  materially
interfere with, or require premature disclosure of, any financing,  acquisition,
divestiture,  reorganization or other material transaction involving the Company
or any of its  majority-owned  subsidiaries  and the Company  promptly gives the
Holder  notice  of  such  determination;   provided,   however,  that  any  such
postponement and/or suspension pursuant to this Section 2.1(b) shall not, in the
aggregate,  exceed  180  days  with  respect  to  any  one  Demand  Registration
statement.

                  2.2. Following receipt of a request for a Demand Registration,
the Company shall:

                  (a)  File a  registration  statement  with the  Commission  as
promptly as practicable,  and shall use the Company's reasonable best efforts to
have the  registration  declared  effective  under the Securities Act as soon as
reasonably  practicable,  in each  instance  giving  due  regard  to the need to
prepare current financial  statements,  conduct due diligence and complete other
actions that are reasonably  necessary under applicable federal and state law to
effect a registered public offering.


                                       -9-

<PAGE>



                  (b) Subject to Section  2.1(b),  use the Company's  reasonable
best  efforts  to  keep  the  registration  statement  relating  to  the  Demand
Registration  Continuously  Effective  for up to 180 days or until such  earlier
date as of which all the Registrable  Securities  under the Demand  Registration
statement  shall  have  been  disposed  of  in  the  manner  described  in  such
registration  statement.  Notwithstanding  the foregoing,  if for any reason the
effectiveness  of  a  registration  statement  pursuant  to  this  Section  2 is
suspended,  the foregoing  period shall be extended by the  aggregate  number of
days of such suspension.

                  2.3. During the Registration  Rights Period, the Company shall
be obligated to effect no more than three (3) Demand Registrations. For purposes
of the  preceding  sentence,  registration  shall  not be  deemed  to have  been
effected (i) if after such  registration  statement has become  effective,  such
registration  or  the  related  offer,   sale  or  distribution  of  Registrable
Securities thereunder is interfered with by any stop order,  injunction or other
order or requirement of the Commission or other governmental agency or court for
any reason not  attributable to the Selling Holder and such  interference is not
thereafter  eliminated,  (ii) if,  during the period that a Demand  Registration
Statement is effective immediately following a postponement or suspension by the
Company  pursuant to Section 2.1(b),  the Selling Holder is unable to reasonably
complete the offering and sale of Registrable  Securities registered pursuant to
such  registration  statement due to adverse  market  conditions  and could have
reasonably  completed  such  offering  and  sale but for  such  postponement  or
suspension,  or (iii) if the conditions to closing specified in the underwriting
agreement,  if any,  entered into in connection with such  registration  are not
satisfied  or  waived,  other  than by reason  of a  failure  on the part of the
Selling Holder. If the Company shall have complied

                                      -10-

<PAGE>



with its  obligations  under this  Agreement,  a right to demand a  registration
pursuant  to this  Section 2 shall be deemed  to have  been  satisfied  upon the
earlier of (x) the date as of which all of the Registrable  Securities  included
therein shall have been disposed of pursuant to the Registration Statement,  and
(y) the date as of which such Demand  Registration  shall have been Continuously
Effective for a period of 180 days,  provided no stop order or similar order, or
proceedings for such an order, is thereafter entered or initiated.

                  2.4. A  registration  pursuant  to this  Section 2 shall be on
such appropriate registration form of the Commission as shall (i) be selected by
the Company and be reasonably  acceptable to the Selling Holder, and (ii) permit
the  disposition of the  Registrable  Securities in accordance with the intended
method or methods of  disposition  specified in the request  pursuant to Section
2.1(a).

                  2.5. If any  registration  pursuant to this Section 2 involves
an underwritten offering (whether on a "firm", "best efforts" or "all reasonable
efforts" basis or otherwise),  or an agented offering,  the Selling Holder shall
have the right to select the underwriter or underwriters and manager or managers
to administer  such  underwritten  offering or the placement agent or agents for
such agented offering;  provided, however, that each Person so selected shall be
reasonably acceptable to the Company.


                                      -11-

<PAGE>




                  Section 3.  Piggyback Registration.
                  3.1. If at any time during the Registration  Rights Period the
Company proposes to register (including for this purpose a registration effected
by the Company for  shareholders  of the Company  other than the Holder)  equity
securities  under the  Securities  Act in  connection  with the public  offering
solely for cash on Form S-1, S-2 or S-3 (or any replacement or successor forms),
the Company shall  promptly give the Holder of  Registrable  Securities  written
notice of such  registration  (a  "Piggyback  Registration").  Upon the  written
request of the Holder  given within 30 days  following  the date of such notice,
the Company  shall cause to be included in such  registration  statement and use
its  reasonable  best efforts to be registered  under the Securities Act all the
Registrable  Securities  that such Holder shall have requested to be registered;
provided,  however,  that  such  right  of  inclusion  shall  not  apply  to any
registration  statement  covering an underwritten  offering of convertible  debt
securities; provided further, that, if Telephone and Data Systems, Inc. ("TDS"),
the parent corporation of the Company, has assumed the rights and obligations of
the Company under this  Agreement and the  Registrable  Securities  consist of a
class of tracking stock of TDS, then such right of inclusion shall only apply to
a  registration  statement  covering an  underwritten  offering of such class of
tracking stock;  and provided  further,  that no request may be made pursuant to
this Section 3.1 if within  twelve (12) months prior to the date of such request
a  registration  statement  in  connection  with  either a  Demand  Registration
pursuant to Section 2.1 or a Piggyback Registration pursuant to this Section 3.1
shall have been declared effective by the Commission. The Company shall have the
absolute  right  to  withdraw  or  cease to  prepare  or file  any  registration
statement for any offering  referred to in this Section 3 without any obligation
or liability to the Holder.

                                      -12-

<PAGE>



                  3.2. If the Underwriters' Representative or Agent shall advise
the Company in writing (with a copy to the Selling Holder) that, in its opinion,
the  amount  of  Registrable   Securities  requested  to  be  included  in  such
registration  would  materially  adversely  affect  such  offering or the timing
thereof,  then the Company will include in such  registration,  to the extent of
the amount  which the Company is so advised can be sold  without  such  material
adverse effect: (i) first, all securities proposed to be sold by the Company for
its own  account;  (ii)  second,  the  Registrable  Securities  requested  to be
included in such  registration by the Holder pursuant to this Section 3, and all
other securities being registered pursuant to the exercise of contractual rights
comparable  to the  rights  granted  in this  Section  3, pro rata  based on the
estimated  gross  proceeds  from the sale  thereof;  and (iii) third,  all other
securities requested to be included in such registration.

                  3.3. During the Registration  Rights Period,  the Holder shall
be  entitled  to have  its  Registrable  Securities  included  in up to five (5)
Piggyback Registrations pursuant to this Section 3.


                  Section 4.  Registration  Procedures.  Whenever required under
Section 2 or Section 3 to effect the registration of any Registrable Securities,
the Company shall, as promptly as practicable:

                  4.1.  Prepare  and file  with the  Commission  a  registration
statement  with respect to such  Registrable  Securities  and use the  Company's
reasonable  best  efforts  to  cause  such  registration   statement  to  become
effective; provided, however, that before filing a registration statement or

                                      -13-

<PAGE>



prospectus  or  any  amendments  or  supplements  thereto,  including  documents
incorporated by reference after the initial filing of the registration statement
and prior to  effectiveness  thereof,  the Company  shall furnish to one firm of
counsel  for the  Selling  Holder  copies  of all  such  documents  in the  form
substantially  as proposed to be filed with the  Commission  prior to filing for
review and comment by such counsel.

                  4.2.  Prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
with  such  registration  statement  as may be  necessary  to  comply  with  the
provisions  of the  Securities  Act and rules  thereunder  with  respect  to the
disposition of all securities  covered by such  registration  statement.  If the
registration  is for an  underwritten  offering,  the  Company  shall  amend the
registration  statement or supplement  the prospectus  whenever  required by the
terms of the  underwriting  agreement  entered  into  pursuant  to Section  4.5.
Pending such  amendment or  supplement  the Holder shall cease making  offers or
Transfers of Registerable Shares pursuant to the prior prospectus.  In the event
that any Registrable Securities included in a registration statement subject to,
or required by, this  Agreement  remain  unsold at the end of the period  during
which the Company is  obligated to use its  reasonable  best efforts to maintain
the Continuously  Effective status of such registration  statement,  the Company
may  file a  post-effective  amendment  to the  registration  statement  for the
purpose of removing such securities from registered status.

                  4.3.  Furnish to the  Selling  Holder,  without  charge,  such
numbers  of  copies  of  the  registration   statement,   any  pre-effective  or
post-effective amendment thereto, the prospectus,

                                      -14-

<PAGE>



including each preliminary prospectus and any amendments or supplements thereto,
in each case in conformity  with the  requirements of the Securities Act and the
rules  thereunder,  and such other related  documents as the Selling  Holder may
reasonably  request in order to facilitate the  disposition  of all  Registrable
Securities included in the registration.

                  4.4. Use the Company's reasonable best efforts (i) to register
and qualify the securities  covered by such  registration  statement  under such
other  securities or Blue Sky laws of such states or jurisdictions of the United
States as shall be reasonably  requested by the Underwriters'  Representative or
Agent (as  applicable,  or if  inapplicable,  in those states  designated by the
Selling  Holder),  and (ii) to obtain the withdrawal of any order suspending the
effectiveness of a registration  statement,  or the lifting of any suspension of
the qualification (or exemption from qualification) of the offer and transfer of
any of the Registrable Securities in any jurisdiction,  at the earliest possible
moment; provided,  however, that the Company shall not be required in connection
therewith  or as a  condition  thereto to qualify  to do  business  or to file a
general consent to service of process in any such states or jurisdictions.

                  4.5.  In the event of any  underwritten  or agented  offering,
enter into and perform the Company's obligations under an underwriting or agency
agreement   (including   indemnification   and   contribution   obligations   of
underwriters  or  agents),  in usual  and  customary  form,  with  the  managing
underwriter or  underwriters  of or agents for such offering.  The Company shall
also cooperate with the Selling Holder and the  Underwriters'  Representative or
Agent  for  such  offering  in  the  marketing  of the  Registrable  Securities,
including making reasonably available the Company's officers,

                                      -15-

<PAGE>



accountants,  counsel,  premises,  books and records for such  purpose,  but the
Company  shall not be required to incur any  significant  out-of-pocket  expense
pursuant to this sentence.

                  4.6.  Promptly  notify  the  Selling  Holder of any stop order
issued or threatened to be issued by the Commission in connection therewith (and
take all reasonable  actions required to prevent the entry of such stop order or
to remove it if entered).

                  4.7. Make available for inspection by the Selling Holder,  any
underwriter  participating  in  such  offering  and the  representatives  of the
Selling  Holder  and  Underwriter  (but not more than one firm of counsel to the
Selling  Holder),  all  financial and other  information  as shall be reasonably
requested by them, and provide the Selling Holder, any underwriter participating
in such offering and the  representatives  of the Selling Holder and Underwriter
the  reasonable  opportunity  to discuss  the  business  affairs  and  financial
statements of the Company with its principal  executives and independent  public
accountants who have certified the audited financial statements included in such
registration statement, in each case all as necessary to enable them to exercise
their due diligence responsibility under the Securities Act; provided,  however,
that information that the Company determines,  in good faith, to be confidential
and which the Company advises such Person in writing is  confidential  shall not
be disclosed  unless such Person signs a  confidentiality  agreement  reasonably
satisfactory  to the Company or the Selling Holder agrees to be responsible  for
such Person's breach of confidentiality on terms reasonably  satisfactory to the
Company.


                                      -16-

<PAGE>



                  4.8.  Use the  Company's  reasonable  best efforts to obtain a
so-called  "comfort letter" from its independent public  accountants,  and legal
opinions of counsel to the Company addressed to the Selling Holder, in customary
form and covering such matters of the type customarily  covered by such letters,
and in a form that shall be reasonably  satisfactory to the Selling Holder.  The
Company shall  furnish to the Selling  Holder a signed  counterpart  of any such
comfort letter or legal opinion.  Delivery of any such opinion or comfort letter
shall be subject to the recipient  furnishing  such written  representations  or
acknowledgments as are customarily  provided by selling shareholders who receive
such comfort letters or opinions.

                  4.9.  Provide and cause to be maintained a transfer  agent and
registrar for all Registrable  Securities covered by such registration statement
from and after a date not later  than the  effective  date of such  registration
statement.

                  4.10. Use the Company's  reasonable  best efforts to cause the
Registrable  Securities covered by such registration  statement (i) to be listed
on a  securities  exchange or included for  quotation  in a  recognized  trading
market to the extent that the Common Stock is so listed or included, and (ii) to
be registered with or approved by such other United States or state governmental
agencies  or  authorities  as may be  necessary  by virtue of the  business  and
operations  of the Company to enable the Selling  Holder  lawfully to consummate
the disposition of such Registrable Securities.


                                      -17-

<PAGE>



                  4.11. Use the Company's  reasonable  best efforts to provide a
CUSIP number for the Registrable  Securities  prior to the effective date of the
first registration statement filed hereunder including Registrable Securities.

                  4.12.  Take such other actions as are  reasonably  required in
order to  expedite or  facilitate  the  disposition  of  Registrable  Securities
included in each such registration.


                  Section  5.  Holder's  Obligations.  It shall  be a  condition
precedent to the  obligations of the Company to take any action pursuant to this
Agreement with respect to the Registrable  Securities of the Selling Holder that
the Selling Holder shall:

                  5.1.  Furnish to the Company such  information  regarding  the
Selling  Holder,  the number of the Registrable  Securities  owned by it and the
intended method of disposition of such securities as shall be required to effect
the  registration  of  the  Selling  Holder's  Registrable  Securities,  and  to
cooperate with the Company in preparing such registration;

                  5.2.  Agree  to  sell  its   Registrable   Securities  to  the
underwriters  at the  same  price  and  on  substantially  the  same  terms  and
conditions  as the Company or the other  Persons,  if any,  on whose  behalf the
registration statement is being filed have agreed to sell their securities,  and
to execute the  underwriting  agreement  agreed to by the Selling Holder (in the
case of a registration

                                      -18-

<PAGE>



under  Section  2) or the  Company  and the  Selling  Holder  (in the  case of a
registration under Section 3).


                  Section 6.  Expenses of  Registration.  Expenses in connection
with  registrations  pursuant to this  Agreement  shall be allocated and paid as
follows:

                  6.1.  With  respect to each Demand  Registration,  the Selling
Holder  shall  bear  and  pay all  expenses  incurred  in  connection  with  any
registration, filing, or qualification of Registrable Securities with respect to
such  Demand  Registration,  including  all  registration,  filing and  National
Association of Securities Dealers, Inc. fees, all fees and expenses of complying
with securities or blue sky laws, all word processing,  duplicating and printing
expenses, messenger and delivery expenses, the reasonable fees and disbursements
of counsel for the Company, and of the Company's independent public accountants,
including the expenses of "cold comfort" letters required by or incident to such
performance  and  compliance,  the fees and  disbursements  of  counsel  for the
Selling Holder, and the management fees,  underwriting discounts and commissions
relating  to the  Selling  Holder's  Registrable  Securities  included  in  such
registration (collectively, the "Registration Expenses").

                  6.2. The Company shall bear and pay all Registration  Expenses
incurred in connection with any Piggyback  Registrations  pursuant to Section 3;
provided,  however,  that  the  Selling  Holder  shall  pay  (i)  the  fees  and
disbursements of counsel for the Selling Holder and (ii) the

                                      -19-

<PAGE>



management fees,  underwriting discounts and commissions relating to the Selling
Holder's Registrable Securities included in such registration.

                  6.3.  Any failure of the Selling  Holder or the Company to pay
any  Registration  Expenses as required by this  Section 6 shall not relieve the
Selling Holder or the Company,  as  applicable,  of its  obligations  under this
Agreement.


                  Section 7. Indemnification;  Contribution.  If any Registrable
Securities are included in a registration statement under this Agreement:

                  7.1. To the extent  permitted by  applicable  law, the Company
shall indemnify and hold harmless the Selling Holder,  each Person,  if any, who
controls the Selling Holder within the meaning of the  Securities  Act, and each
officer,  director,  partner,  and  employee  of the  Selling  Holder  and  such
controlling Person, against any and all losses, claims, damages, liabilities and
expenses (joint and several),  including  attorneys' fees and  disbursements and
expenses  of  investigation,  incurred  by such party  pursuant to any actual or
threatened  action,  suit,  proceeding or investigation,  or to which any of the
foregoing  Persons may become subject under the Securities Act, the Exchange Act
or other  federal  or state  laws,  insofar  as such  losses,  claims,  damages,
liabilities  and  expenses  arise out of or are based upon any of the  following
statements, omissions or violations (collectively a "Violation"):


                                      -20-

<PAGE>



                  (i) Any untrue  statement  or alleged  untrue  statement  of a
         material fact contained in such registration  statement,  including any
         preliminary  prospectus  or final  prospectus  contained  therein,  any
         amendments  or  supplements  thereto or any documents  incorporated  by
         reference therein (collectively, the "Registration Statement");

                  (ii)  The  omission  or  alleged  omission  to  state  in  the
         Registration  Statement a material fact required to be stated  therein,
         or necessary to make the statements therein not misleading; or

                  (iii) Any violation or alleged violation by the Company of the
         Securities Act, the Exchange Act, any applicable  state  securities law
         or any rule or regulation  promulgated  under the  Securities  Act, the
         Exchange Act or any applicable state securities law;

provided,  however, that the indemnification  required by this Section 7.1 shall
not  apply to  amounts  paid in  settlement  of any such  loss,  claim,  damage,
liability or expense if such  settlement is effected  without the consent of the
Company, which consent shall not be unreasonably withheld, nor shall the Company
be  liable in any such  case for any such  loss,  claim,  damage,  liability  or
expense to the extent that it arises out of or is based upon a  Violation  which
occurs in reliance upon and in conformity with written information  furnished to
the Company by the  indemnified  party expressly for use in connection with such
registration.


                                      -21-

<PAGE>



                  7.2. To the extent  permitted by  applicable  law, the Selling
Holder shall  indemnify  and hold harmless the Company,  each of its  directors,
each of its officers who shall have signed the registration statement,  and each
Person,  if any, who controls the Company  within the meaning of the  Securities
Act,  against any and all losses,  claims,  damages,  liabilities  and  expenses
(joint and several), including attorneys' fees and disbursements and expenses of
investigation,  incurred  by such party  pursuant  to any  actual or  threatened
action,  suit,  proceeding  or  investigation,  or to which any of the foregoing
Persons may become subject under the  Securities  Act, the Exchange Act or other
federal or state laws, insofar as such losses, claims, damages,  liabilities and
expenses  arise  out of or are  based  upon any  Violation,  in each case to the
extent (and only to the extent) that such Violation  occurs in reliance upon and
in conformity with written information furnished by the Selling Holder expressly
for use in connection with such registration;  provided,  however,  that (x) the
indemnification  required by this Section 7.2 shall not apply to amounts paid in
settlement of any such loss, claim,  damage,  liability or expense if settlement
is effected  without the consent of the Selling Holder,  which consent shall not
be unreasonably  withheld, and (y) in no event shall the amount of any indemnity
under this Section 7.2 exceed the gross  proceeds from the  applicable  offering
received by the Selling Holder.

                  7.3. Promptly after receipt by an indemnified party under this
Section  7 of  notice  of the  commencement  of any  action,  suit,  proceeding,
investigation or threat thereof made in writing for which such indemnified party
may make a claim under this Section 7, such  indemnified  party shall deliver to
the  indemnifying  party a written  notice of the  commencement  thereof and the
indemnifying party shall have the right to participate in and, to the extent the
indemnifying party so

                                      -22-

<PAGE>



desires,  jointly with any other indemnifying party similarly noticed, to assume
the defense thereof with counsel mutually satisfactory to the parties; provided,
however,  that an  indemnified  party  shall  have the right to  retain  its own
counsel,  with  the  fees  and  disbursements  and  expenses  to be  paid by the
indemnifying  party, if  representation of such indemnified party by the counsel
retained  by the  indemnifying  party  would be  inappropriate  due to actual or
potential differing interests between such indemnified party and any other party
represented by such counsel in such  proceeding.  The failure to deliver written
notice  to the  indemnifying  party  within  a  reasonable  time  following  the
commencement  of any such action,  if materially  prejudicial  to its ability to
defend such action,  shall relieve such  indemnifying  party of any liability to
the  indemnified   party  under  this  Section  7  but  shall  not  relieve  the
indemnifying  party of any liability that it may have to any  indemnified  party
otherwise than pursuant to this Section 7. Any fees and expenses incurred by the
indemnified  party (including any fees and expenses  incurred in connection with
investigating or preparing to defend such action or proceeding) shall be paid to
the indemnified  party,  as incurred,  within thirty (30) days of written notice
thereof to the  indemnifying  party  (regardless  of  whether  it is  ultimately
determined  that  an  indemnified  party  is  not  entitled  to  indemnification
hereunder).  Any such indemnified  party shall have the right to employ separate
counsel  in any such  action,  claim or  proceeding  and to  participate  in the
defense thereof, but the fees and expenses of such counsel shall be the expenses
of such indemnified  party unless (i) the  indemnifying  party has agreed to pay
such fees and  expenses  or (ii) the  indemnifying  party  shall have  failed to
promptly  assume the defense of such action,  claim or  proceeding  or (iii) the
named parties to any such action,  claim or proceeding  (including any impleaded
parties)  include both such indemnified  party and the  indemnifying  party, and
such indemnified  party shall have been advised by counsel that there may be one
or more legal defenses

                                      -23-

<PAGE>



available to it which are  different  from or in addition to those  available to
the  indemnifying  party and that the assertion of such defenses  would create a
conflict of interest such that counsel employed by the indemnifying  party could
not  faithfully  represent  the  indemnified  party  (in  which  case,  if  such
indemnified  party notifies the indemnifying  party in writing that it elects to
employ  separate  counsel  at  the  expense  of  the  indemnifying   party,  the
indemnifying  party  shall  not have the  right to assume  the  defense  of such
action,  claim or  proceeding  on behalf  of such  indemnified  party,  it being
understood,  however,  that the indemnifying party shall not, in connection with
any one such action,  claim or proceeding or separate but substantially  similar
or related actions,  claims or proceedings in the same jurisdiction  arising out
of the same general  allegations or circumstances,  be liable for the reasonable
fees and expenses of more than one firm of attorneys  (together with appropriate
local  counsel)  separate  from  its  own  counsel  at any  time  for  all  such
indemnified parties, unless in the reasonable judgment of such indemnified party
a conflict of interest may exist between such indemnified party and any other of
such indemnified  parties with respect to such action,  claim or proceeding,  in
which  event  the  indemnifying  party  shall be  obligated  to pay the fees and
expenses of such additional counsel or counsels). No indemnifying party shall be
liable to an indemnified  party for any settlement of any action,  proceeding or
claim without the written consent of the indemnifying party, which consent shall
not be unreasonably withheld.

                  7.4. If the  indemnification  required by this  Section 7 from
the  indemnifying  party is  unavailable to an  indemnified  party  hereunder in
respect of any losses, claims,  damages,  liabilities or expenses referred to in
this Section 7:


                                      -24-

<PAGE>



                  (a) The  indemnifying  party,  in lieu  of  indemnifying  such
indemnified  party,  shall  contribute  to the  amount  paid or  payable by such
indemnified party as a result of such losses,  claims,  damages,  liabilities or
expenses in such  proportion as is  appropriate to reflect the relative fault of
the  indemnifying  party and indemnified  parties in connection with the actions
which resulted in such losses, claims, damages, liabilities or expenses, as well
as any other  relevant  equitable  considerations.  The  relative  fault of such
indemnifying party and indemnified  parties shall be determined by reference to,
among other things,  whether any Violation has been  committed by, or relates to
information supplied by, such indemnifying party or indemnified parties, and the
parties'  relative intent,  knowledge,  access to information and opportunity to
correct or prevent  such  Violation.  The amount paid or payable by a party as a
result of the losses,  claims,  damages,  liabilities  and expenses  referred to
above  shall be deemed  to  include,  subject  to the  limitations  set forth in
Section 7.1 and  Section  7.2,  any legal or other fees or  expenses  reasonably
incurred by such party in connection with any investigation or proceeding.

                  (b) The  parties  hereto  agree  that it would not be just and
equitable if  contribution  pursuant to this Section 7.4 were  determined by pro
rata  allocation or by any other method of  allocation  which does not take into
account the equitable  considerations  referred to in Section 7.4(a).  No Person
guilty of fraudulent  misrepresentation  (within the meaning of Section 11(f) of
the Securities  Act) shall be entitled to  contribution  from any Person who was
not guilty of such fraudulent misrepresentation.


                                      -25-

<PAGE>



                  7.5. If indemnification is available under this Section 7, the
indemnifying  parties shall indemnify each indemnified  party to the full extent
provided  in this  Section  7  without  regard  to the  relative  fault  of such
indemnifying  party or indemnified  party or any other  equitable  consideration
referred to in Section 7.4.

                  7.6.  The  obligations  of the Company and the Selling  Holder
under this Section 7 shall survive the completion of any offering of Registrable
Securities pursuant to a registration statement under this Agreement.


                  Section  8.  Holdback.  The  Holder,  if so  requested  by the
Underwriters'  Representative  or Agent in  connection  with an  offering of any
securities covered by a registration statement filed by the Company,  whether or
not the Holder's  securities are included  therein,  shall not effect any public
sale or  distribution  of shares of Common Stock or any  securities  convertible
into or exchangeable or exercisable for shares of Common Stock, including a sale
pursuant  to  Rule  144  under  the  Securities  Act  (except  as  part  of such
underwritten or agented  registration),  during the 15- day period prior to, and
during the 180-day period beginning on, the date such registration  statement is
declared  effective  under the Securities Act by the  Commission,  provided that
such Holder is timely  notified of such effective date in writing by the Company
or such Underwriters' Representative or Agent. In order to enforce the foregoing
covenant,  the Company  shall be entitled to impose  stop-transfer  instructions
with respect to the  Registrable  Securities of the Holder until the end of such
period.

                                      -26-

<PAGE>




                  Section  9.  Amendment,   Modification  and  Waivers;  Further
Assurances.  (a) This  Agreement  may not be amended,  modified or  supplemented
except by an  agreement  in  writing  executed  by each of the  Company  and the
Holder.

                  (b) No  waiver of any terms or  conditions  of this  Agreement
shall  operate as a waiver of any other breach of such terms and  conditions  or
any other term or  condition,  nor shall any  failure to enforce  any  provision
hereof operate as a waiver of such provision or of any other  provision  hereof.
No written waiver hereunder,  unless it by its own terms explicitly  provides to
the contrary, shall be construed to effect a continuing waiver of the provisions
being waived and no such waiver in any instance shall constitute a waiver in any
other instance or for any other purpose or impair the right of the party against
whom such waiver is claimed in all other  instances or for all other purposes to
require full compliance with such provision.

                  (c) Each of the parties  hereto shall execute all such further
instruments  and documents  and take all such further  action as any other party
hereto may  reasonably  require in order to effectuate the terms and purposes of
this Agreement.

                  Section 10.  Assignment and Assumption.

                  Section 10.1.  Assignment;  Benefit. This Agreement and all of
the  provisions  hereof  shall be binding upon and shall inure to the benefit of
the parties hereto and their respective heirs,

                                      -27-

<PAGE>



assigns,  executors,  administrators  or  successors;  provided,  however,  that
neither this Agreement nor any of the rights, interests or obligations hereunder
shall be assigned or  delegated by the Holder to any person who  purchases  such
Registrable Securities from the Holder, except (i) as provided in the Investment
Agreement or (ii) to one or more  "affiliates"  of the Holder within the meaning
of Rule 144(a)(1) adopted by the Commission pursuant to the Securities Act.

                  10.2 Assumption Upon Merger,  Consolidation or Reorganization.
The  Company  shall  not,  directly  or  indirectly,   enter  into  any  merger,
consolidation or  reorganization in which the Company shall not be the surviving
corporation unless the proposed surviving corporation shall, before such merger,
consolidation or  reorganization,  agree in writing to assume the obligations of
the Company under this Agreement,  and for that purpose references  hereunder to
"Registrable  Securities"  shall be deemed to be  references  to the  securities
which the  Holder  would be  entitled  to receive in  exchange  for  Registrable
Securities  under any such merger,  consolidation or  reorganization;  provided,
however,  that the provisions of this Agreement  shall not apply in the event of
any  merger,  consolidation  or  reorganization  in which the Company is not the
surviving  corporation  if the Holder is entitled to receive in exchange for its
Registrable  Securities  (i) cash or (ii)  securities  which may be sold without
registration or other restriction under the Act.


                                      -28-

<PAGE>



                  Section 11.  Miscellaneous.

                  11.1.  Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF DELAWARE, WITHOUT GIVING 
REGARD TO THE CONFLICT OF LAWS PRINCIPLES THEREOF.

                  11.2. Notices. All notices,  requests and other communications
hereunder shall be in writing and shall be made by hand delivery,  facsimile, or
overnight air courier guaranteeing next day delivery, as follows:

                  (a)  If to the Company, at:

                           Aerial Communications, Inc.
                           8410 West Bryn Mawr Avenue
                           Suite 1100
                           Chicago, Illinois  60631
                           Attention:  Donald W. Warkentin
                           Telephone:  (773) 399-4145
                           Facsimile:  (773) 399-7997

                  with a copy (which shall not constitute notice) to:

                           Telephone and Data Systems, Inc.
                           30 North LaSalle Street
                           Suite 4000
                           Chicago, Illinois  60602
                           Attention:  LeRoy T. Carlson, Jr.
                           Telephone:  (312) 630-1900
                           Facsimile:  (312) 630-9299


                                      -29-

<PAGE>



                  and a copy (which shall not constitute notice) to:

                           Sidley & Austin
                           One First National Plaza
                           42nd Floor - SW
                           Chicago, Illinois  60603
                           Attention:  Michael G. Hron, Esq.
                           Telephone:  (312) 853-2030
                           Facsimile:  (312) 853-7036


                  (b)  if to the Holder, at:

                           SONERA LTD.
                           P.O. Box 106
                           FIN-00051-TELE
                           Teollisuuskatu 15, HELSINKI
                           Attention: Maire Laitinen, Esq.
                           Telephone:  011-35-8-2040-3641
                           Facsimile:  011-35-8-2040-3414


                  with a copy (which shall not constitute notice) to:

                           Patton Boggs, L.L.P.
                           2550 M. Street, N.W.
                           Washington, D.C.  20037-1350
                           Attention:  Richard M. Stolbach, Esq.
                           Telephone:  (202) 457-6324
                           Facsimile:  (202) 457-6315


or at such other address as any party may from time to time furnish to the other
parties by a notice  given in  accordance  with the  provisions  of this Section
11.2.  All such  notices  and  communications  shall be deemed to have been duly
given at the time  delivered  by hand,  if  personally  delivered;  when receipt
confirmed, if sent by facsimile; and the next business day after timely delivery
to the courier,  if sent by an overnight air courier service  guaranteeing  next
day delivery.

                                      -30-

<PAGE>



                  11.3. Entire Agreement; Integration. This Agreement supersedes
all prior agreements  between or among either of the parties hereto with respect
to the subject  matter  contained  herein and embodies the entire  understanding
among the parties relating to such subject matter.

                  11.4.   Injunctive   Relief.   Each  of  the  parties   hereto
acknowledges  that in the  event  of a  breach  by any of  them of any  material
provision  of this  Agreement,  the  aggrieved  party may be without an adequate
remedy at law. Each of the parties  therefore agrees that in the event of such a
breach  hereof  the  aggrieved  party  may  elect  to  institute  and  prosecute
proceedings  in  any  court  of  competent   jurisdiction  to  enforce  specific
performance or to enjoin the continuing  breach hereof.  By seeking or obtaining
any such relief,  the  aggrieved  party shall not be  precluded  from seeking or
obtaining any other relief to which it may be entitled.

                  11.5.  Section Headings.  Section headings are for convenience
of  reference  only and shall not affect the  meaning of any  provision  of this
Agreement.

                  11.6.  Counterparts.  This  Agreement  may be  executed in any
number of  counterparts,  each of which shall be an  original,  and all of which
shall together  constitute one and the same instrument.  All signatures need not
be on the same counterpart.

                  11.7.  Severability.  If any provision of this Agreement shall
be invalid or  unenforceable,  such  invalidity  or  unenforceability  shall not
affect the validity and enforceability of

                                      -31-

<PAGE>



the remaining  provisions of this Agreement,  unless the result thereof would be
unreasonable,  in which case the parties hereto shall negotiate in good faith as
to appropriate amendments hereto.

                  11.8.  Filing.  A copy of this Agreement and of all amendments
thereto shall be filed at the principal executive office of the Company with the
corporate recorder of the Company.

                  11.9.  Termination.  This  Agreement  may be terminated at any
time by a  written  instrument  signed  by the  parties  hereto.  Unless  sooner
terminated in accordance with the preceding sentence, this Agreement (other than
Section 7 hereof) shall terminate in its entirety on the earlier to occur of (i)
the  expiration  of the  Registration  Rights  Period or (ii) such date as there
shall be no  Registrable  Securities  outstanding,  provided  that any shares of
Common  Stock  previously  subject to this  Agreement  shall not be  Registrable
Securities  following  the sale of any such  shares  in an  offering  registered
pursuant to this Agreement.

                  11.10. Attorneys' Fees. In any action or proceeding brought to
enforce  any  provision  of this  Agreement,  or where any  provision  hereof is
validly asserted as a defense, the successful party shall be entitled to recover
reasonable  attorneys'  fees  (including  any fees  incurred  in any  appeal) in
addition to its costs and expenses and any other available remedy.

                  11.11. No Third Party Beneficiaries.  Nothing herein expressed
or implied is intended to confer upon any person,  other than the parties hereto
or their respective permitted assigns,

                                      -32-

<PAGE>



successors, heirs and legal representatives,  any rights, remedies,  obligations
or liabilities under or by reason of this Agreement.

                  11.12.  Compliance  with  Rule  144.  With  a view  to  making
available  to the  Holder  the  benefits  of  Rule  144  promulgated  under  the
Securities Act, the Company agrees to use its reasonable best efforts during the
Registration Rights Period to:

                  (a) if the Company is required to file reports pursuant to the
Securities  Exchange Act of 1934, as amended (the "Exchange Act"), file with the
Commission,  as and when applicable,  on a timely basis, all reports required to
be filed by the Company under the Exchange Act; or

                  (b) if the Company is not required to file reports pursuant to
the Exchange Act, upon the request of any Holder of Registrable Securities,  the
Company shall make publicly available the information  specified in subparagraph
(c)(2) of Rule 144 of the Securities Act, and take such further action as may be
reasonably  required  from  time to time  and as may be  within  the  reasonable
control of the Company, to enable the Holder to Transfer Registrable  Securities
without  registration  under the  Securities  Act within the  limitation  of the
exemptions  provided by Rule 144 under the Securities Act or any similar rule or
regulation hereafter adopted by the Commission.

                                    * * * * *



                                      -33-

<PAGE>



                  IN WITNESS  WHEREOF,  this Agreement has been duly executed by
the parties hereto as of the date first written above.

AERIAL COMMUNICATIONS, INC.



By:      /s/ Donald W. Warkentin
         -------------------------------
         Donald W. Warkentin
         President and Chief Executive Officer





SONERA LTD.


By:      /s/ Aulis Salin
         ----------------------------  
Name:    Aulis Salin
         ---------------------------- 
Title:   President  and CEO
         ----------------------------




                SIGNATURE PAGE TO REGISTRATION RIGHTS AGREEMENT,
                         DATED AS OF SEPTEMBER 8, 1998,
               BETWEEN AERIAL COMMUNICATIONS, INC. AND SONERA LTD.





                                      -34-

<PAGE>



                                                                    EXHIBIT 99.4

                                                                  EXECUTION COPY











                             JOINT VENTURE AGREEMENT


                                  By and Among


                           AERIAL COMMUNICATIONS, INC.


                           AERIAL OPERATING CO., INC.


                                       and


                             SONERA CORPORATION U.S.




                          Dated as of September 8, 1998







<PAGE>

                                TABLE OF CONTENTS
                                -----------------

                                                                            Page
                                                                            ----
                                                                           
ARTICLE I         DEFINITIONS

         Section 1.01  Defined Terms..........................................3
                       -------------
         Section 1.02  Determination of Beneficial Ownership.................14
                       -------------------------------------

ARTICLE II        FORMATION AND PURPOSE

         Section 2.01  Formation and Purpose of Joint Venture................15
                       --------------------------------------
         Section 2.02  Formation of LLCs.....................................15
                       -----------------

ARTICLE III       VENTURE OPPORTUNITIES

         Section 3.01  Exclusivity of Venture; Venture Opportunities.........16
                       ---------------------------------------------
         Section 3.02  Partial Termination of Exclusivity Period.............19
                       -----------------------------------------
         Section 3.03  Termination of Agreement..............................21
                       ------------------------
         Section 3.04  Other Business; Non-Competition.......................23
                       -------------------------------
         Section 3.05  Exempt Aerial Party Markets...........................25
                       ---------------------------
         Section 3.06  C or F Block B-PCS Licenses...........................26
                       ---------------------------

ARTICLE IV        INVESTMENT

         Section 4.01  Initial Investment in LLC.............................27
                       -------------------------
         Section 4.02  Carried Interest......................................29
                       ----------------
         Section 4.03  Additional Initial Investment.........................33
                       -----------------------------
         Section 4.04  Amount of Investment..................................34
                       --------------------
         Section 4.05  Additional Initial Investors..........................35
                       ----------------------------
         Section 4.06  Limitation on Percentage Interest.....................37
                       ---------------------------------


ARTICLE V         TRANSFER OF INTEREST

         Section 5.01  Restrictions on Transfer..............................37
                       ------------------------
         Section 5.02  Right of First Negotiation............................39
                       --------------------------
         Section 5.03  Tag-Along Rights......................................43
                       ----------------
         Section 5.04  Limitation on Non-Transferring Party's Rights.........44
                       ---------------------------------------------

ARTICLE VI        TECHNOLOGY

         Section 6.01  Technological Changes and Advances....................45
                       ----------------------------------


                                      - i -

<PAGE>





ARTICLE VII    NAME OF LLC

         Section 7.01  Name of LLC...........................................46
                       -----------

ARTICLE VIII   MANAGEMENT AND OPERATION

         Section 8.01  Board of Managers.....................................46
                       -----------------
         Section 8.02  Unanimous Approval....................................48
                       ------------------
         Section 8.03  Right of First Negotiation............................49
                       --------------------------
         Section 8.04  Management and Operation..............................53
                       ------------------------

ARTICLE IX        DISPUTES

         Section 9.01  General...............................................54
                       -------
         Section 9.02  Negotiation Procedure.................................54
                       ---------------------
         Section 9.03  Unresolved Disputes...................................55
                       -------------------
         Section 9.04  Jurisdiction; Consent to Service of Process...........57
                       -------------------------------------------

ARTICLE X         REPRESENTATIONS AND WARRANTIES

         Section 10.01  Organization and Standing............................59
                        -------------------------
         Section 10.02  Authorization........................................59
                        -------------
         Section 10.03  Litigation...........................................59
                        ----------
         Section 10.04  Absence of Conflict..................................59
                        -------------------
         Section 10.05  Absence of Undisclosed Liabilities...................60
                        ----------------------------------

ARTICLE XI        MISCELLANEOUS

         Section 11.01  Confidentiality......................................60
                        ---------------
         Section 11.02  Notices..............................................62
                        -------
         Section 11.03  Further Assurances...................................63
                        ------------------
         Section 11.04  Amendment............................................64
                        ---------
         Section 11.05  Waiver of Compliance; Consents.......................64
                        ------------------------------
         Section 11.06  Expenses.............................................64
                        --------
         Section 11.07  Entire Agreement.....................................64
                        ----------------
         Section 11.08  Counterparts.........................................65
                        ------------
         Section 11.09  Headings and Captions................................65
                        ---------------------
         Section 11.10  Severability.........................................65
                        ------------
         Section 11.11  Governing Law........................................65
                        -------------
         Section 11.12  Compliance with FCC Rules............................65
                        -------------------------
         Section 11.13  No Claim of Immunity.................................67
                        --------------------

                                     - ii -

<PAGE>



         Section 11.14  Successors and Assigns...............................68
                        ----------------------
         Section 11.15  Equitable Remedies...................................68
                        ------------------
         Section 11.16  Remedies Cumulative..................................68
                        -------------------
         Section 11.17  Limitation on Damages................................69
                        ---------------------


SCHEDULES
- ---------

           3.05            -- Exempt Aerial Party Markets
           9.02(c)         -- Designated Employees, Representatives and Officers


EXHIBITS
- --------

         A        --       Form of Certificate of Formation
         B        --       Form of Limited Liability Company Agreement
         C        --       Form of Trademark License Agreement
         D        --       Form of Management Agreement












                                     - iii -

<PAGE>



                             JOINT VENTURE AGREEMENT


                  This JOINT  VENTURE  AGREEMENT,  dated as of September 8, 1998
(the  "Agreement"),  is entered  into  between  AERIAL  COMMUNICATIONS,  INC., a
Delaware  corporation  ("Aerial"),   AERIAL  OPERATING  CO.,  INC.,  a  Delaware
corporation  and  wholly-owned  subsidiary of Aerial  ("AOC" and,  together with
Aerial,  the  "Aerial  Parties"),   and  SONERA  CORPORATION  U.S.,  a  Delaware
corporation ("Sonera U.S.").

                              W I T N E S S E T H:

                  WHEREAS,   each  of  Aerial   and   United   States   Cellular
Corporation, a Delaware corporation ("USCC"), are majority-owned subsidiaries of
Telephone and Data Systems,  Inc., a Delaware  corporation  ("TDS"),  and, thus,
AOC, Aerial, USCC and TDS are Affiliates (as defined herein);

                  WHEREAS,  Sonera U.S. is a  wholly-owned  subsidiary of Sonera
Ltd., a Finnish limited  liability  company  ("Sonera" and, together with Sonera
U.S., the "Sonera Parties"), and, thus, the Sonera Parties are Affiliates;

                  WHEREAS,  the parties  hereto  desire to form a joint  venture
which,  subject to certain exceptions as set forth herein, will serve during the
Exclusivity  Period (as defined  herein) as the exclusive  vehicle through which
the Aerial  Parties and the Sonera Parties will (i) acquire  licenses  issued by
the Federal  Communications  Commission to provide B-PCS (as defined herein) and
(ii)

                                      

<PAGE>



build and operate systems with respect to such licenses utilizing GSM Technology
(as defined herein);

                  WHEREAS,  the parties  hereto  desire that a separate  limited
liability  company be formed  pursuant to the laws of the State of Delaware  for
each Market (as defined  herein) in which one or more B-PCS Licenses (as defined
herein)  will be acquired as  contemplated  hereunder,  and that each of AOC and
Sonera U.S. (or a wholly-owned  direct or indirect  subsidiary of AOC or Sonera)
be a member of such limited liability company;

                  WHEREAS,  the  parties  hereto  desire  that  (i)  AOC  or  an
Affiliate  of AOC manage  such  B-PCS  system  for each such  limited  liability
company  pursuant to the terms of this Agreement and a Management  Agreement (as
defined  herein)  and (ii)  Aerial  grant a license  to such  limited  liability
company  authorizing,  inter  alia,  the  use of  Aerial's  name  pursuant  to a
Trademark License Agreement (as defined herein); and

                  WHEREAS,   the  parties  hereto  desire  to  set  forth  their
respective  rights and obligations  with respect to such joint venture,  limited
liability companies and management arrangements.

                  NOW,  THEREFORE,  in  consideration  of the  premises  and the
mutual  covenants,  conditions and promises  hereinafter set forth,  the parties
hereby agree as follows:


                                      - 2 -

<PAGE>



                                    ARTICLE I
                                   DEFINITIONS

                  Section 1.01  Defined  Terms.  Capitalized  terms used in this
Agreement shall have the meanings set forth in this Section 1.01.

                  "Additional  Initial Class A Member" has the meaning set forth
in Section 4.01(c) hereof.

                  "Aerial  Entity"  means  Aerial,  AOC and any  Person in which
Aerial,  directly or  indirectly,  through one or more  intermediaries,  owns an
interest, regardless of whether Aerial controls such Person.

                  "Aerial Group" means Aerial, each Aerial Sub and each alliance
that owns or operates a system  providing  B-PCS in which alliance  Aerial or an
Aerial Sub owns a 20% or greater interest.

                  "Aerial Sub" means AOC or any other Subsidiary of Aerial.

                  "Affiliate"  means any Person  that,  directly or  indirectly,
through  one or more  intermediaries,  controls,  is  controlled  by or is under
common control with such Person.  The term "control"  shall mean the possession,
direct or indirect, of the power to direct or cause the direction

                                      - 3 -

<PAGE>



of the management or policies of such person,  whether by reason of ownership of
voting stock or other equity interests, by contract or otherwise.

                  "Aggregate Class A Membership  Interest  Percentage" means the
sum of the percentages of the Class A Membership Interests.

                  "Aggregate Class B Membership  Interest  Percentage" means the
sum of the percentages of the Class B Membership Interests.

                  "Aggregate Required Capital  Contribution" means, with respect
to any LLC formed  pursuant  to Section  2.02  hereof,  the  aggregate  required
capital  contribution  set  forth in the  related  Proposed  Business  Plan with
respect to any Proposed Project  approved  pursuant to Section 3.01(b) hereof or
the aggregate required capital  contribution as reasonably  determined by Sonera
U.S.  with  respect  to any Market  identified  in Section  3.01(c)  hereof,  as
applicable.

                  "AOC  Initial  LLC  Interest"  has the  meaning  set  forth in
Section 4.03 hereof.

                  "AOC  Shares"  has the  meaning  set  forth in the  Investment
Agreement.

                  "B-PCS"  means  broadband  personal   communications  services
provided in the United States on the following frequency blocks:
                  Block A:  1850-1865 MHz paired with 1930-1945 MHz
                  Block B:  1870-1885 MHz paired with 1950-1965 MHz
                  Block C:  1895-1910 MHz paired with 1975-1990 MHz

                                      - 4 -

<PAGE>



                  Block D:  1865-1870 MHz paired with 1945-1950 MHz
                  Block E:  1885-1890 MHz paired with 1965-1970 MHz
                  Block F:  1890-1895 MHz paired with 1970-1975 MHz

B-PCS does not include narrowband personal  communications  services,  paging or
other  Wireless  Services not  constituting  broadband  personal  communications
services.

                  "B-PCS  License" means a license issued by the FCC authorizing
the holder thereof to provide B-PCS in any Market.

                  "BTA"  means any one of the 487 Basic  Trading  Areas based on
the Rand McNally 1992  Commercial  Atlas & Marketing  Guide,  123rd Edition,  at
pages 38-39, with the following additions licensed separately as BTA-like areas:
(i)  American  Samoa;   (ii)  Guam;  (iii)  Northern   Mariana   Islands;   (iv)
Mayaguez/Aguadilla-Ponce,  Puerto Rico; (v) San Juan,  Puerto Rico; and (vi) the
United States Virgin Islands. The Mayaguez/Aguadilla-Ponce BTA-like service area
consists of the  following  municipios:  Adjuntas,  Aguada,  Aguadilla,  Anasco,
Arroyo, Cabo Rojo, Coamo, Guanica, Guayama,  Guayanilla,  Hormigueros,  Isabela,
Jayuya,  Juana  Diaz,  Lajas,  Las Marias,  Maricoa,  Maunabo,  Mayaguez,  Moca,
Patillas,  Penuelas,  Ponce,  Quebradillas,  Rincon, Sabana Grande, Salinas, San
Germain,  Santa Isabel,  Villalba, and Yauco. The San Juan BTA-like service area
consists of all other municipios in Puerto Rico.

                  "Business  Day" means any day other than a  Saturday,  Sunday,
legal  holiday in Chicago,  Illinois or other day on which  commercial  banks in
Chicago are authorized by law or governmental decree to close.

                                      - 5 -

<PAGE>



                  "C or F Block  Notice"  has the  meaning  set forth in Section
3.06(b) hereof.

                  "Carried  Interest"  has the  meaning  set  forth  in  Section
4.02(a) hereof.

                  "Carried  Interest  Amendment"  has the  meaning  set forth in
Section 4.02(c) hereof.

                  "Carried  Interest  Negotiation  Notice"  has the  meaning set
forth in Section 4.02(c)hereof.

                  "Cellular Service" means any service governed by Section 22.99
of the rules of the FCC.

                  "Class A Member"  means a member of an LLC formed  pursuant to
Section 2.02 hereof holding a Class A Membership Interest.

                  "Class A Membership  Interest" means each beneficial  interest
in an LLC  formed  pursuant  to  Section  2.02  hereof  designated  as a Class A
Membership  Interest on Schedule I attached  to the  related  Limited  Liability
Company Agreement.

                  "Class B Member"  means a member of an LLC formed  pursuant to
Section 2.02 hereof holding a Class B Membership Interest.


                                      - 6 -

<PAGE>



                  "Class B Membership  Interest" means each beneficial  interest
in an LLC  formed  pursuant  to  Section  2.02  hereof  designated  as a Class B
Membership  Interest on Schedule I attached  to the  related  Limited  Liability
Company Agreement.

                  "Class C Member"  means a member of an LLC formed  pursuant to
Section 2.02 hereof holding a Class C Membership Interest.

                  "Class C Membership  Interest" means each beneficial  interest
in an LLC  formed  pursuant  to  Section  2.02  hereof  designated  as a Class C
Membership  Interest on Schedule I attached  to the  related  Limited  Liability
Company Agreement.

                  "Compete" and "Competition" means to provide, or the provision
of, respectively, Wireless Services within the same geographic area.

                  "Derivative"  has the  meaning  set  forth  in the  Investment
Agreement.

                  "Disapproved  License"  has the  meaning  set forth in Section
3.02(a) hereof.

                  "Disapproving  Party"  has the  meaning  set forth in  Section
3.02(a) hereof.

                  "Exclusivity  Period"  has the  meaning  set forth in  Section
3.01(a) hereof.


                                      - 7 -

<PAGE>



                  "Exempt  Aerial  Party  Markets"  has the meaning set forth in
Section 3.05(a) hereof.

                  "FCC"  means  the  Federal  Communications  Commission  or any
successor thereto.

                  "GSM    Technology"    means   Global   Systems   For   Mobile
Communications technology,  subject to such changes resulting from the evolution
of such technology or the development of subsequent  technologies  based thereon
or derived therefrom as determined pursuant to Section 6.01 hereof.

                  "Investment  Agreement" means the Investment Agreement,  dated
as of September 8, 1998, among TDS, Aerial, AOC and Sonera.

                  "Investment Election Period" has the meaning set forth in 
Section 3.01(b) hereof.

                  "Limited  Liability  Company  Agreement"  has the  meaning set
forth in Section 2.02 hereof.

                  "LLC" has the meaning set forth in Section 2.02 hereof.

                  "LLC Board" has the meaning set forth in Section 8.01(a) 
hereof.


                                      - 8 -

<PAGE>



                  "LLC Fifth  Anniversary"  means,  with  respect to an LLC, the
fifth  anniversary of the date of formation of such LLC pursuant to Section 2.02
hereof.

                  "LLC Tenth  Anniversary"  means,  with  respect to an LLC, the
tenth  anniversary of the date of formation of such LLC pursuant to Section 2.02
hereof.

                  "Majority  Class A Member" means the Class A Member  holding a
majority of the Aggregate Class A Membership Interest Percentage.

                  "Majority  Class B Member" means the Class B Member  holding a
majority of the Aggregate Class B Membership Interest Percentage.

                  "Management  Agreement"  has the  meaning set forth in Section
8.04 hereof.

                  "Management  Compensation Amendment" has the meaning set forth
in Section 4.02(c) hereof.

                  "Management  Compensation  Negotiation Period" has the meaning
set forth in Section 4.02(c) hereof.

                  "Market" means an MTA or BTA, as applicable.


                                      - 9 -

<PAGE>



                  "Minimum Sonera U.S. Initial LLC Interest" has the meaning set
forth in Section 4.01(a) hereof.

                  "Minority  Class A Member"  means  any Class A Member  holding
less than a majority of the Aggregate Class A Membership Interest Percentage.

                  "Minority  Class B Member"  means  any Class B Member  holding
less than a majority of the Aggregate Class B Membership Interest Percentage.

                  "MTA" means any one of the 47 Major Trading Areas based on the
Rand McNally 1992 Commercial  Atlas & Marketing Guide,  123rd Edition,  at pages
38-39, with the following exceptions and additions: (i) Alaska is separated from
the Seattle MTA and is licensed  separately;  (ii) Guam and the Northern Mariana
Islands are licensed as a single MTA-like area; (iii) Puerto Rico and the United
States Virgin Islands are licensed as a single  MTA-like area; and (iv) American
Samoa is licensed as a single MTA-like area.

                  "Non-Transferring Party" has the meaning set forth in Section 
5.01(a) hereof.

                  "Partial Termination Notice" has the meaning set forth in 
Section 3.02(a) hereof.

                  "Person" means any general  partnership,  limited partnership,
corporation,  limited liability company,  joint venture,  trust, business trust,
cooperative, association, individual or other

                                     - 10 -

<PAGE>



entity,  and  the  heirs,  executors,   administrators,  legal  representatives,
successors and assigns of such person, as the context may require.

                  "Project Notice" has the meaning set forth in Section 3.01(b) 
hereof.

                  "Proposal Recipient" has the meaning set forth in Section 3.01
(b) hereof.

                  "Proposed Business Plan" has the meaning set forth in Section 
3.01(b) hereof.

                  "Proposed Project" has the meaning set forth in Section 
3.01(b) hereof.

                  "Proposing Party" has the meaning set forth in Section 3.01(b)
hereof.

                  "Proposed  Sonera U.S. Initial LLC Interest" has the meaning
set forth in Section 4.03 hereof.

                  "Purchase Agreement" means the Purchase Agreement, dated as of
June 1, 1998, among TDS, Aerial, AOC and Sonera.

                  "Restricted   Business   Combination"   means   any   business
combination  of an LLC formed  pursuant to Section  2.02 hereof with or into any
other  entity  other than a business  combination  which  satisfies  each of the
following criteria: (i) such LLC is the surviving entity of

                                     - 11 -

<PAGE>



such  business  combination;  (ii) each of the  Majority  Class A Member and the
Majority Class B Member immediately prior to such business  combination continue
as the Majority  Class A Member and the Majority  Class B Member,  respectively,
immediately after such business combination; and (iii) such business combination
does not  materially  adversely  affect the rights of the Class A Members or the
Class B Members under this Agreement or the Limited Liability Company Agreement.

                  "Restricted  LLC  Action" has the meaning set forth in Section
8.03(a) hereof.

                  "Restricted LLC Action Negotiation Notice" has the meaning set
forth in Section 8.03(a) hereof.

                  "Restricted LLC Action Negotiation Period" has the meaning set
forth in Section 8.03(b) hereof.                                                
                                                                                
                  "Restricted  LLC Action  Notice"  has the meaning set forth in
Section 8.03(a) hereof.

                  "SMR  Service"  means any service  governed by Section 90.7 of
the rules of the FCC.

                  "Sonera  Entity" means  Sonera,  Sonera U.S. and any Person in
which Sonera, directly or indirectly,  through one or more intermediaries,  owns
an interest, regardless of whether Sonera controls such Person.

                                     - 12 -

<PAGE>



                  "Sonera U.S.  Initial LLC  Interest" has the meaning set forth
in Section 4.03 hereof.

                  "Subsidiary"  of a Person shall mean a corporation as to which
a majority of the voting power is owned or  controlled  by such  Person,  either
directly  or  indirectly;  but any  such  corporation  shall be  deemed  to be a
Subsidiary of such Person only as long as such ownership or control exists.

                  "Supplemental  Agreement"  means the  Supplemental  Agreement,
dated as of September 8, 1998, by and among Aerial, AOC and Sonera.

                  "Tag-Along  Notice"  has the  meaning  set  forth  in  Section
5.03(a) hereof.

                  "Technology Dispute" has the meaning set forth in Section 6.01
hereof.

                  "Third Party  Transferee" has the meaning set forth in Section
5.02(a) hereof.

                  "Trademark  License  Agreement"  has the  meaning set forth in
Section 7.01 hereof.

                  "Transfer" means to, directly or indirectly, sell, transfer or
otherwise dispose of.

                  "Transfer  Negotiation  Notice"  has the  meaning set forth in
Section 5.02(a) hereof.

                  "Transfer  Negotiation  Period"  has the  meaning set forth in
Section 5.02(b) hereof.

                                     - 13 -

<PAGE>



                  "Transfer Notice" has the meaning set forth in Section 5.02(a)
hereof.

                  "Transferring  Party"  has the  meaning  set forth in  Section
5.01(a) hereof.

                  "USCC Group" means USCC and each Subsidiary of USCC.

                  "Venture" has the meaning set forth in Section 2.01 hereof.

                  "Wireless  Services" means any B-PCS,  Cellular Service or SMR
Service.

                  Section  1.02  Determination  of  Beneficial  Ownership.   For
purposes  of  determining  in  connection  with this  Agreement  the  beneficial
ownership  interest  of one entity (the  "Owner") in another  entity (the "Owned
Entity"),  beneficial  ownership  shall be:  (i) if the Owner  directly  owns an
interest in the Owned Entity,  such  percentage  interest so directly  owned, or
(ii)  if the  Owner  indirectly  owns  an  interest  in the  Owned  Entity,  the
percentage  interest owned by the Owner in the  intervening  entity in which the
Owner directly owns an interest  multiplied by the percentage  interest directly
owned by the intervening  entity in the Owned Entity.  If there is more than one
intervening  entity between the Owner and the Owned Entity,  then the principles
of clause (ii) hereof shall be reapplied such that all  percentage  interests in
the intervening  entities  indirectly owned by the Owner are taken into account.
For  purposes  of  determining  the  beneficial  ownership  of Sonera U.S. or an
Affiliate  of Sonera U.S. in an Owned  Entity in which Aerial or any Aerial Sub,
directly or indirectly,

                                     - 14 -

<PAGE>



also owns an interest, any percentage interest owned, directly or indirectly, by
Sonera U.S.,  Sonera or an Affiliate of Sonera in Aerial or any Aerial Sub shall
not be taken into account.

                                   ARTICLE II
                              FORMATION AND PURPOSE

                  Section  2.01  Formation  and  Purpose of Joint  Venture.  The
Aerial Parties and Sonera U.S.  hereby form a joint venture (the  "Venture") for
the purpose of acquiring  B-PCS  Licenses and building and operating  systems in
the United States with respect to such B-PCS Licenses  utilizing GSM Technology.
It  shall be the  primary  intention  of the  Venture  (i) to build  out the GSM
Technology  footprint in the United  States by  providing  B-PCS  utilizing  GSM
Technology  and (ii) not to acquire  or attempt to acquire  control of any B-PCS
Licenses  for  geographic  areas in which the Venture  would  Compete with other
providers of Wireless  Services  that utilize GSM  Technology.  The scope of the
Venture shall not include narrowband personal communications services, paging or
other Wireless Services not constituting B-PCS.

                  Section 2.02 Formation of LLCs. AOC and Sonera U.S. shall form
a separate limited liability company (each an "LLC") with respect to each Market
for which the Venture  determines  pursuant to this  Agreement to acquire one or
more B-PCS Licenses.  Such LLC shall hold all of the B-PCS Licenses acquired for
such Market and shall build and operate the system related thereto. The LLC need
not be formed,  and AOC and Sonera  U.S.  need not invest  therein  pursuant  to
Article IV hereof,  until such time as the Venture has  negotiated  on behalf of
such LLC a definitive

                                     - 15 -

<PAGE>



agreement to acquire a B-PCS License.  Each such LLC shall be formed pursuant to
the  Delaware  Limited  Liability  Company  Act, as amended,  by filing with the
Delaware Secretary of State a Certificate of Formation in substantially the form
attached  hereto as Exhibit  A. Each such LLC shall have a duration  of 40 years
and shall be governed by an operating agreement in substantially the form of the
Limited Liability Company Agreement attached hereto as Exhibit B.

                                   ARTICLE III
                              VENTURE OPPORTUNITIES

                  Section 3.01  Exclusivity of Venture;  Venture  Opportunities.
(a) Except as otherwise expressly permitted by this Agreement,  the Venture will
be the exclusive vehicle through which any Aerial Entity expands in B-PCS in the
United States and through which any Sonera Entity  participates  in B-PCS in the
United  States,  in each case  during  the  period  (the  "Exclusivity  Period")
commencing  on the date hereof and  terminating  on the earlier to occur of: (i)
the fifth  anniversary  of the date  hereof;  or (ii) the date upon which Sonera
U.S.  has  invested  (as  determined  pursuant  to  Section  4.04(b)  hereof) an
aggregate of $400  million in the equity of one or more LLCs formed  pursuant to
Section 2.02  hereof;  provided,  however,  that the  Exclusivity  Period may be
extended by mutual written agreement of the parties hereto.  Except as otherwise
provided in this Article  III, all B-PCS  Licenses in all Markets are subject to
the provisions of this Section 3.01 during the  Exclusivity  Period.  During the
Exclusivity  Period,  the Aerial Parties and the Sonera Parties shall share with
each  other,  on a  regular  and  timely  basis,  information  in  such  party's
possession relating to possible Venture opportunities and to work together on an
ongoing basis to develop and review

                                     - 16 -

<PAGE>



possible  Venture  opportunities  prior to submission of a formal Project Notice
pursuant to Section 3.01(b) hereof.  Upon termination of the Exclusivity Period,
the parties shall no longer be required, but nonetheless may continue, to comply
with the provisions of this Section 3.01 with respect to pursuing  opportunities
to  acquire  B-PCS  Licenses.   Any  compliance  after  the  expiration  of  the
Exclusivity  Period by any party hereto with the provisions of this Section 3.01
shall not be deemed to be a reinstatement of the provisions of this Section 3.01
with respect to any other B-PCS Licenses.  For purposes of this Section 3.01(a),
the  terms  "expand"  and  "participate"  shall  mean  (i)  the  acquisition  or
beneficial ownership by any Aerial Entity or any Sonera Entity, respectively, of
a 20% or greater  interest in any  business  engaged in the  provision of B-PCS,
(ii)  the  active  involvement  by  any  Aerial  Entity  or any  Sonera  Entity,
respectively,  in the  acquisition of a B-PCS License or in the  solicitation of
other investors in such acquisition or in a business engaged in the provision of
B-PCS,  (iii) the  operation or  management  by any Aerial  Entity or any Sonera
Entity,  respectively,  of a business  engaged in the  provision of B-PCS or the
B-PCS  system  related  thereto  or (iv) the right of any  Aerial  Entity or any
Sonera Entity, respectively,  to elect or appoint one or more representatives to
the governing body of a business engaged in the provision of B-PCS.

                  (b) Except as set forth in Section 3.01(c)  hereof,  if at any
time during the Exclusivity  Period either Aerial Party or any Aerial Sub on the
one hand,  or either  Sonera Party or any  Affiliate  thereof on the other hand,
desires to acquire a B-PCS  License in any Market,  then AOC or Sonera U.S.,  as
applicable,  shall  prepare  and submit to the other  party a written  notice (a
"Project  Notice")  notifying  the other party of its desire to proceed with the
project  (the  "Proposed  Project")  and a proposed  business  plan (a "Proposed
Business Plan") setting forth in detail the proposed purchase

                                     - 17 -

<PAGE>



price  and  anticipated  sources  of  funding  (which  shall not  reasonably  be
projected  to result in a debt to equity ratio of greater than 80/20 at the time
of  commencement  of service in the Market) for acquisition of the B-PCS License
and  construction  of the  system,  the  projected  construction  schedule,  the
projected  financial  results and such other  information as the party preparing
the Proposed  Business  Plan (the  "Proposing  Party") deems  material.  AOC and
Sonera U.S. shall be required to prepare a separate  Project Notice and Proposed
Business  Plan for each B-PCS  License  that AOC or Sonera  U.S.,  respectively,
desires to acquire unless (i) such B-PCS  Licenses are in the same Market,  (ii)
such B-PCS Licenses are in contiguous  Markets or (iii) the Proposing  Party has
been advised by the party holding such B-PCS  Licenses that such B-PCS  Licenses
are only available for  acquisition as a group.  The party receiving the Project
Notice and Proposed Business Plan (the "Proposal Recipient") shall have a period
(the  "Investment  Election  Period") of 30 days from the date of receipt of the
Project Notice and Proposed Business Plan (or, if not received together, then 30
days from the later of the date of receipt of the Project Notice and the date of
receipt of the Proposed  Business  Plan) to review the Proposed  Business  Plan,
request additional information from the Proposing Party and notify the Proposing
Party of the Proposal Recipient's decision whether to invest in and, in the case
of AOC, manage the Proposed  Project;  provided,  however,  that if the Proposal
Recipient  has  requested  from  the  Proposing  Party  additional   information
reasonable  in scope and  relevant to a decision  with  respect to the  Proposed
Project within 15 days of commencement of the Investment  Election Period,  then
the Investment  Election Period shall terminate on the later of (i) the 30th day
after commencement of the Investment  Election Period or (ii) the 10th day after
receipt by the Proposal Recipient of such additional  information.  In the event
that the Proposal  Recipient elects to invest in and, in the case of AOC, manage
the Proposed Project,

                                     - 18 -

<PAGE>



then (A) AOC and  Sonera  U.S.  shall form an LLC for each  Market  which is the
subject of the Proposed  Project pursuant to Section 2.02 hereof for the purpose
of implementing  the Proposed  Project,  (B) AOC and Sonera U.S. shall invest in
each such LLC  pursuant to Article IV hereof and (C) AOC shall  manage each such
LLC pursuant to Article  VIII hereof.  The  provisions  of this Section  3.01(b)
shall  apply to any  Proposed  Project  for which  both a Project  Notice  and a
Proposed Business Plan have been received by the Proposal Recipient prior to the
expiration  of the  Exclusivity  Period,  regardless  of whether the  Investment
Election Period terminates after the expiration of the Exclusivity Period.

                  (c)  Notwithstanding the provisions of Section 3.01(b) hereof,
if at any time  during the  Exclusivity  Period  Sonera  U.S.  arranges  for the
acquisition  (on terms which shall not  reasonably  be  projected to result in a
debt to  equity  ratio of  greater  than  80/20 at the time of  commencement  of
service in the  applicable  Market) of control of one or more B-PCS Licenses (of
at least 15 megahertz) to serve either the Chicago BTA or the Dallas BTA and, in
each case, AOC receives  written notice from Sonera U.S. of such  arrangement on
or prior to the expiration of the  Exclusivity  Period,  then (A) AOC and Sonera
U.S.  shall form an LLC  pursuant  to  Section  2.02  hereof for the  purpose of
acquiring such B-PCS License(s) and building the system related thereto, (B) AOC
and Sonera U.S.  shall  invest in such LLC pursuant to Article IV hereof and (C)
AOC shall manage such system pursuant to Article VIII hereof.

                  Section 3.02 Partial Termination of Exclusivity Period. (a) In
the event that the  Proposal  Recipient  does not elect to invest in and, in the
case of AOC, manage a Proposed Project

                                     - 19 -

<PAGE>



pursuant to Section 3.01(b) hereof (such Proposal Recipient being referred to as
a "Disapproving Party"), then the Proposing Party may, but shall not be required
to,  terminate the  Exclusivity  Period with respect to each B-PCS License which
was the  subject of the  Proposed  Project  (each a  "Disapproved  License")  by
providing  written notice (a "Partial  Termination  Notice") to the Disapproving
Party of such termination within 30 days after receipt by the Proposing Party of
the  Disapproving  Party's  decision not to invest in the Proposed  Project,  in
which case the Disapproving  Party shall have no further  interest  hereunder in
such Disapproved  License and the Proposing Party shall have the right to pursue
independently  of the Venture the  opportunity  to invest in and operate a B-PCS
system for such Disapproved License; provided, however, that if, within 180 days
after providing such Partial  Termination Notice to the Disapproving  Party, the
Proposing  Party  has not  entered  into a binding  agreement  to  acquire  each
Disapproved  License  set forth in the  Project  Notice  at a price  equal to or
higher than the price set forth in the  Project  Notice,  then each  Disapproved
License  relating to such Project Notice shall remain subject to the Exclusivity
Period.  In the event that the  Proposing  Party  presents  a Project  Notice or
Proposed  Business Plan that  contemplates  the acquisition of B-PCS Licenses in
more than one Market (or more than one B-PCS License within a Market),  then the
Proposing Party shall have no right to pursue  independently  of the Venture any
Disapproved  License with respect to such Proposed  Project unless the Proposing
Party  pursues all of the  Disapproved  Licenses  with respect to such  Proposed
Project.  In the event that the  Disapproving  Party has not  received a Partial
Termination  Notice from the  Proposing  Party  within the time period set forth
above,  then each  Disapproved  License shall remain subject to the  Exclusivity
Period.


                                     - 20 -

<PAGE>



                  (b) In the event  that a  Proposal  Recipient  has  elected to
invest in a Proposed  Project  pursuant to Section 3.01(b) hereof or Sonera U.S.
has arranged for the acquisition of a B-PCS License  pursuant to Section 3.01(c)
hereof but, in either case,  either (i) Sonera U.S.,  either  individually or in
conjunction with an Additional  Initial Class A Member (as defined herein),  and
AOC  have  not  agreed  to fund  collectively  100% of the  equity  required  in
connection  therewith and firm commitments for funding of the remainder  through
additional  equity  investors  have not been  obtained  pursuant to Section 4.05
hereof within the 120-day period set forth therein or (ii) such Proposed Project
or arrangement  contemplated the use of debt financing (not reasonably projected
to exceed a debt to equity ratio of 80/20 at the time of commencement of service
in the  applicable  Market) and firm  commitments to provide such financing have
not been obtained within 120 days after the date on which AOC has advised Sonera
U.S. in writing of the AOC Initial LLC Interest pursuant to Section 4.03 hereof,
then:  (x) if AOC is the  Proposing  Party,  the related  B-PCS License shall be
deemed a "Disapproved  License" and Sonera U.S. shall be deemed a  "Disapproving
Party" with respect to such Disapproved  License for purposes of Section 3.02(a)
hereof and AOC may,  but shall not be required  to,  terminate  the  Exclusivity
Period  with  respect  to  such  Disapproved  License  by  providing  a  Partial
Termination  Notice to Sonera U.S.  within 30 days after the  expiration of such
120-day period set forth in clause (i) or (ii) hereof, as applicable;  or (y) if
Sonera U.S. is the Proposing Party or the B-PCS License is in one of the Markets
identified  in Section  3.01(c)  hereof,  then the B-PCS  License  shall  remain
subject to the Exclusivity Period.

                  Section 3.03  Termination  of Agreement.  This  Agreement and,
thus, the Venture may be terminated in its entirety as follows:

                                     - 21 -

<PAGE>



                  (a)  Unless  the  parties  hereto  shall  otherwise  agree  in
writing,  this Agreement shall automatically  terminate in the event that, prior
to the fifth  anniversary  of the date hereof,  Sonera or an Affiliate of Sonera
shall, pursuant to Section 5.5 of the Investment Agreement,  either (i) Transfer
any of its AOC Shares  without  the  consent of TDS or Aerial to a Person  other
than an Affiliate of Sonera or (ii) issue a Derivative.

                  (b) In the event that  either (i) as of the fifth  anniversary
of the date hereof no LLC formed by AOC and Sonera U.S. pursuant to Section 2.02
hereof has acquired a B-PCS  License or (ii) at any time that,  but only at such
time that, on or after the fifth  anniversary of the date hereof there is no LLC
that had been formed  pursuant to Section 2.02 hereof which  continues to hold a
B- PCS License and in which each of AOC and Sonera own,  directly or indirectly,
a beneficial interest,  then, in either case, the Aerial Parties and Sonera U.S.
shall each have the option to elect to terminate  this Agreement in its entirety
upon  30  days'  advance  written  notice  to  the  other.  Notwithstanding  the
foregoing, such termination option shall not be exercisable (i) as long as there
is at least one  Management  Agreement  in force and  effect  between  AOC or an
Affiliate  thereof and an LLC formed  pursuant to Section 2.02 hereof or (ii) if
an LLC formed  pursuant  to Section  2.02  hereof  has, on or prior to the fifth
anniversary of the date hereof,  entered into a definitive  agreement to acquire
one or more B-PCS Licenses but such  acquisition  has not yet been  consummated,
unless  such  definitive  agreement  is  thereafter   terminated  prior  to  the
consummation  of such  acquisition.  In  addition  to the  foregoing  provisions
restricting  exercise  of the  termination  option  set  forth  in this  Section
3.01(b),  if both a  Project  Notice  and a  Proposed  Business  Plan  have been
received by a Proposal Recipient but the Investment Election Period with respect
to the related Proposed Project has not terminated

                                     - 22 -

<PAGE>



prior  to  expiration  of the  Exclusivity  Period,  then the  exercise  of such
termination option shall be further  restricted as follows:  (i) if the Proposal
Recipient does not accept the Proposed  Project  within the Investment  Election
Period,  then such termination option shall not be exercisable until the earlier
to occur of (A) the rejection of such Proposed Project by the Proposal Recipient
or (B) the expiration of the Investment Election Period; or (ii) if the Proposal
Recipient elects to accept the Proposed  Project within the Investment  Election
Period,  then such  termination  option shall not be exercisable  if, within six
months after the fifth anniversary of the date hereof, an LLC is formed pursuant
to Section 2.02 hereof and such LLC has either (A) acquired the B-PCS License(s)
relating to the Proposed  Project or (B) entered into a definitive  agreement to
acquire  the  B-PCS  License(s)  relating  to  the  Proposed  Project  but  such
acquisition has not yet been  consummated,  unless such definitive  agreement is
thereafter terminated prior to the consummation of such acquisition.

                  (c) This  Agreement  may be  terminated in its entirety at any
time upon the mutual written consent of the parties hereto.

                  Section 3.04 Other  Business;  Non-Competition.  (a) Except as
set forth in Section 3.01 and Section 3.04(b) hereof,  any Aerial Entity and any
Sonera Entity may engage in one or more other  businesses,  and own interests in
one  or  more  other  business   ventures,   of  every  kind  and   description,
independently  or with  others.  No party to this  Agreement  or any LLC  formed
pursuant to Section 2.02 hereof shall have any rights in or to such  independent
businesses or business  ventures of any other party to this  Agreement or to the
income or profits therefrom by virtue of this Agreement.

                                     - 23 -

<PAGE>



                  (b) Notwithstanding any other provision of this Agreement: (i)
neither an Aerial  Entity nor a Sonera  Entity  shall,  directly or  indirectly,
operate  or  manage,  or  beneficially  own a 20% or  greater  interest  in, any
business  engaged in the provision of Wireless  Services in Competition with any
LLC formed pursuant to Section 2.02 hereof to any significant  extent;  and (ii)
no  Sonera  Entity  shall,  directly  or  indirectly,   operate  or  manage,  or
beneficially  own a 20% or  greater  interest  in, any  business  engaged in the
provision of Wireless  Services if the population  within the  geographic  areas
served by the systems providing Wireless Services operated,  managed or owned by
the Sonera  Entities or such other  business,  as the case may be, which overlap
with geographic  areas served by the systems owned or operated by the USCC Group
or the Aerial Group, as applicable,  is equal to or greater than 2% of the total
population within the geographic areas of all such systems owned and operated by
the USCC Group or the Aerial Group, as applicable;  provided,  however, that the
provisions of this Section 3.04(b)(ii) shall not be applicable to the USCC Group
at any time that USCC ceases to be an  Affiliate  of Aerial;  provided  further,
that no  Sonera  Entity  shall be  deemed  to be in  violation  of this  Section
3.04(b)(ii) if (A) such violation results from the commencement of the ownership
or operation of a system by a member of the USCC Group or the Aerial Group after
the execution by a Sonera  Entity of a binding  commitment to operate or manage,
or own a 20% or greater  interest in, such business and (B) the execution by the
Sonera  Entity of such binding  commitment  preceded the  execution of a binding
commitment  to so own or  operate  such  system by a member of the USCC Group or
Aerial Group,  as  applicable.  The Sonera Parties and the Aerial Parties shall,
and with respect to members of the USCC Group the Aerial Parties shall use their
reasonable  best efforts to, timely advise a senior  officer of the other of the
execution of any such binding  commitment  by any Sonera Entity or any member of
the Aerial Group (or USCC Group),

                                     - 24 -

<PAGE>



respectively,  to operate, manage or own a system providing Wireless Services in
the United States,  and the party receiving such information hereby covenants to
maintain  the  confidentiality  thereof  pursuant to the terms of Section  11.01
hereof.

                  Section 3.05 Exempt  Aerial Party  Markets.  (a) Schedule 3.05
hereto sets forth a list of the Markets in which the Aerial Parties participate,
directly or indirectly, in B-PCS as of the date hereof (the "Exempt Aerial Party
Markets").  Notwithstanding the provisions of Section 3.01 hereof and subject to
the provisions of Section  3.05(b) hereof,  the Exclusivity  Period shall not be
applicable  to any Aerial  Entity with  respect to any of the B-PCS  Licenses in
such Exempt Aerial Party  Markets.  If Sonera U.S.  submits a Project Notice and
Proposed Business Plan to AOC proposing the acquisition of a B-PCS License in an
Exempt  Aerial  Party  Market  and AOC  elects  not to invest  in such  Proposed
Project, then such Project Notice and Proposed Business Plan shall not be deemed
to  constitute  a Project  Notice and  Proposed  Business  Plan for  purposes of
Section 5.5 of the  Investment  Agreement.  Such Schedule 3.05 shall be modified
from time to time as required pursuant to Section 3.05(b).

                  (b)  Notwithstanding  the  provisions  of Section 3.01 hereof,
during the  Exclusivity  Period any Aerial  Entity  shall be permitted to pursue
independently  of the  Venture  the  acquisition  of one or more B-PCS  Licenses
otherwise subject to the Exclusivity Period if the consideration to be exchanged
by such Aerial  Entity for such B-PCS  License(s)  consists of one or more B-PCS
Licenses in Exempt Aerial Party Markets.  Upon completion of such exchange,  (i)
the Market  relating to each such B-PCS License  obtained by an Aerial Entity in
such exchange shall be added

                                     - 25 -

<PAGE>



to Schedule  3.05,  thereby  including such Market among the Exempt Aerial Party
Markets not subject to the Exclusivity  Period and (ii) each Exempt Aerial Party
Market  relating to each such B-PCS  License so  exchanged  by an Aerial  Entity
shall, unless an Aerial Entity continues to hold a B-PCS License in such Market,
be deleted from Schedule 3.05, thereby causing the B-PCS Licenses in such Market
to become subject to the Exclusivity Period.

                  Section 3.06 C or F Block B-PCS Licenses.  (a) Notwithstanding
the  provisions of Section 3.01 hereof and subject to the  provisions of Section
3.06(b)  hereof,  each B-PCS License to provide  service on frequency Block C or
Block F, as  defined in the  definition  of  "B-PCS"  set forth in Section  1.01
hereof (each a "C or F Block License"),  shall not be subject to the Exclusivity
Period.

                  (b) If at any time during the Exclusivity Period either Aerial
Party or any Aerial Sub on the one hand, or either Sonera Party or any Affiliate
thereof on the other  hand,  desires to  acquire a C or F Block  License,  or an
interest in any entity holding a C or F Block License, in any Market (other than
an Exempt Aerial Party  Market),  then AOC or Sonera U.S. as  applicable,  shall
submit to the other party a written notice (a "C or F Block  Notice")  notifying
the other party of its desire to proceed with such acquisition.  For a period of
30 days  beginning  on the date of receipt of the C or F Block  Notice,  AOC and
Sonera U.S. shall engage in good faith negotiations in an attempt to structure a
transaction  in which they jointly  acquire such C or F Block  License,  or each
acquire an interest in an entity holding such C or F Block License, and in which
AOC or an Affiliate  thereof  shall manage the related  system,  all on mutually
acceptable terms and conditions.  As part of such negotiation  process,  AOC and
Sonera U.S. shall determine which provisions of this Agreement and

                                     - 26 -

<PAGE>



the  agreements  attached  hereto as exhibits  shall be  incorporated  into such
structure.  If AOC and Sonera U.S. do not reach an agreement as to the structure
of such transaction within such 30-day period, then AOC and Sonera U.S. shall be
permitted to pursue the acquisition of such C or F Block License, or an interest
in the entity  holding such C or F Block License,  independently  of the Venture
and such C or F Block  Notice  shall not be deemed to be a Project  Notice  (and
Proposed Business Plan) for purposes of Section 5.5 of the Investment Agreement.
If AOC  and  Sonera  U.S.  reach  an  agreement  as to  the  structure  of  such
transaction within such 30-day period, then the provisions of Section 5.5 of the
Investment Agreement shall no longer be applicable.

                                   ARTICLE IV
                                   INVESTMENT

                  Section  4.01 Initial  Investment  in LLC. (a) With respect to
each LLC formed  pursuant to Section 2.02 hereof,  (i) Sonera U.S.  shall invest
cash in  immediately  available  funds  (or  otherwise  in  accordance  with the
applicable  Project Notice and Proposed  Business Plan) in an amount  determined
pursuant to Section  4.04(a) hereof such that Sonera U.S.  beneficially  owns at
least  34.5% of the equity of the LLC (the  "Minimum  Sonera  U.S.  Initial  LLC
Interest"), subject to Section 4.01(c) hereof, and (ii) AOC shall invest cash in
immediately  available  funds (or  otherwise in accordance  with the  applicable
Project Notice and Proposed Business Plan) in an amount  determined  pursuant to
Section 4.04(a) hereof such that AOC beneficially owns at least 1% of the equity
of the LLC. Each of AOC and Sonera U.S.,  at its sole option,  may invest in any
of the LLCs formed  pursuant to Section 2.02 hereof either  directly in such LLC
or indirectly through one or more

                                     - 27 -

<PAGE>



wholly-owned subsidiaries of AOC or Sonera, respectively,  and the references in
this  Article IV to "AOC" and "Sonera  U.S." shall be deemed to include any such
wholly-owned  subsidiary of AOC or Sonera,  respectively.  Sonera U.S.  shall be
deemed a Class A Member in the LLC and the entire  initial  equity  interest  of
Sonera U.S. in such LLC shall be  designated  as a Class A Membership  Interest.
AOC shall be deemed a Class B Member in such LLC and the entire  initial  equity
interest  of AOC in such  LLC  shall  be  designated  as a  Class  B  Membership
Interest.  As a Class A Member or Class B Member in an LLC,  Sonera U.S. and AOC
shall be  subject  to the  provisions  applicable  to Class A Members or Class B
Members,  respectively, set forth in this Agreement and in the Limited Liability
Company Agreement governing such LLC.

                  (b)  Notwithstanding the provisions of Section 4.01(a) hereof,
either AOC or Sonera U.S. may, in lieu of cash,  contribute  property to an LLC,
to be used in the business of and in furtherance of the purpose of such LLC, but
only if: (i) with respect to any Market governed by Section 3.01(b) hereof,  the
parties hereto have agreed in writing to such  contribution and the value of the
property  so  contributed;  or (ii) with  respect to either  Market  governed by
Section 3.01(c) hereof,  the property  contributed is valued at the contributing
party's book value of such property.

                  (c)  Notwithstanding the provisions of Section 4.01(a) hereof,
Sonera U.S. may permit a third party (an "Additional Initial Class A Member") to
make a portion of the investment  required to be made by Sonera U.S. pursuant to
Section  4.01(a) hereof in connection  with the Minimum Sonera U.S.  Initial LLC
Interest,  provided  that  Sonera U.S.  beneficially  owns at least 19.5% of the
equity of the LLC and such Additional  Initial Class A Member owns equity in the
LLC equal to no

                                     - 28 -

<PAGE>



more than the portion of the Minimum Sonera U.S.  Initial LLC Interest not owned
by Sonera U.S.  Each of Sonera U.S. and such  Additional  Initial Class A Member
shall be deemed  Class A Members and the  investment  by each of Sonera U.S. and
such  Additional  Initial  Class  A  Member  shall  be  designated  as a Class A
Membership Interest.  It shall be a condition precedent to such investment by an
Additional  Initial Class A Member that such  Additional  Initial Class A Member
agree to be bound by the  provisions of Articles IV and V of this Agreement that
are applicable to such Additional Initial Class A Member.

                  Section 4.02 Carried Interest. (a) Upon the purchase by AOC of
at least a 1%  beneficial  interest in each LLC pursuant to Section 4.01 hereof,
AOC shall be  granted  an  additional  15%  beneficial  interest  in such LLC (a
"Carried  Interest").  Such Carried Interest shall not require the investment of
any  additional  cash  by AOC and may be held  directly  or  indirectly  by AOC.
Pursuant to Section  4.02(b)  hereof,  the  Carried  Interest in an LLC shall be
subject to divestiture  prior to the fifth  anniversary of the formation of such
LLC. Subject to Section 4.02(c) hereof,  the Carried Interest in an LLC shall be
non-dilutable  as long  as (i)  such  Carried  Interest  is  held,  directly  or
indirectly,  by AOC and (ii)  AOC or an  Affiliate  thereof  is  serving  in the
capacity as manager pursuant to the Management Agreement.

                  (b) (i) With  respect to each LLC formed  pursuant  to Section
2.02 hereof, if the related Management  Agreement between such LLC and AOC or an
Affiliate of AOC is properly  terminated  (after all applicable  cure provisions
have expired) pursuant to either Section 8.2(a) or

                                     - 29 -

<PAGE>



Section 8.3 thereof,  then the Carried  Interest shall be subject to divestiture
according to the following schedule:

<TABLE>
<CAPTION>
  Date of Termination of                   % of Carried          % of Carried
   Management Agreement                   Interest Divested   Interest Remaining
- --------------------------                -----------------   ------------------

<S>                                               <C>               <C>
Prior to 1st Anniversary                          12                 3

On or After 1st Anniversary
    but Prior to 2nd Anniversary                   9                 6

On or After 2nd Anniversary
    but Prior to 3rd Anniversary                   6                 9

On or After 3rd Anniversary
    but Prior to 4th Anniversary                   4                11

On or After 4th Anniversary
   but Prior to 5th Anniversary                    2                13

On or After 5th Anniversary                        0                15
</TABLE>

For purposes of determining the date of termination of the Management  Agreement
in connection with the foregoing  schedule,  such date shall be deemed to be the
date upon which (A) such LLC provides AOC or an Affiliate of AOC, as applicable,
acting as manager pursuant to the Management Agreement, with a written notice of
termination  pursuant to Section 8.2(a) of the  Management  Agreement or (B) the
date of automatic  termination of the Management  Agreement  pursuant to Section
8.3  thereof.  The term  "Anniversary"  as used  above  shall  refer to the date
occurring  12 months  after  the date of the  Management  Agreement  or the date
occurring in 12-month increments thereafter, as applicable.


                                     - 30 -

<PAGE>



                  (ii) Any  termination of the Management  Agreement  other than
pursuant  to  Section  8.2(a) or  Section  8.3  thereof  shall  not  result in a
divestiture of the Carried  Interest.  If AOC or its  Affiliate,  as applicable,
acting as manager pursuant to the Management  Agreement,  cures the event giving
rise to the right of such LLC to terminate the Management  Agreement  within the
applicable cure period, if any, set forth in the Management Agreement,  then the
Management  Agreement shall not terminate and the Carried  Interest shall not be
divested.  Any portion of the Carried Interest that is divested pursuant to this
Section 4.02(b) shall be  re-allocated  among the members of the LLC as provided
in the Limited  Liability  Company  Agreement and,  pursuant to Section  4.02(a)
hereof, the entire Carried Interest shall no longer be non-dilutable.

                  (c ) AOC and Sonera U.S.  acknowledge that the primary purpose
of the Carried Interest in each LLC formed pursuant to Section 2.02 hereof is to
compensate  AOC for its agreement to act as manager of the B-PCS System for such
LLC  and  provide  the  full  range  of  services  specified  in the  Management
Agreement,  all at AOC's cost thereof.  AOC and Sonera U.S. further  acknowledge
that it is their mutual intention and expectation that, over time,  depending on
the  initial  capitalization  of such  LLC  and in the  absence  of  exceptional
circumstances  such as  significant  changes in  technology  or in the nature or
scope of the LLC's  business,  each LLC will have the ability to raise  adequate
capital without  additional  capital  contributions by LLC members.  The parties
therefore  agree  that,  after a  reasonable  period of time  within  which such
capital self- sufficiency should have been achieved but in no event prior to the
LLC Tenth  Anniversary,  it may be  equitable  and  appropriate  to decrease the
non-dilutable  portion of the Carried  Interest and to increase the compensation
to be provided to Aerial pursuant to the Management Agreement.  Accordingly,  if
on

                                     - 31 -

<PAGE>



or after an LLC Tenth  Anniversary  Sonera U.S. desires to negotiate with AOC to
amend the  percentage  beneficial  interest  in such LLC which shall be deemed a
non-dilutable Carried Interest with respect to future capital contributions,  if
any, to such LLC (a "Carried  Interest  Amendment"),  then Sonera U.S.  shall so
notify AOC in writing,  which notice shall  reference this Section  4.02(c) (the
"Carried Interest Negotiation Notice"). Sonera U.S. and AOC shall then negotiate
with each other regarding such possible Carried Interest Amendment as well as an
amendment to the related  Management  Agreement to provide AOC or its Affiliate,
as applicable,  acting in the capacity of manager  thereunder,  with  additional
compensation  for such  management  services over and above such manager's costs
(together  with the  Carried  Interest  Amendment,  a  "Management  Compensation
Amendment")  for a period (the  "Management  Compensation  Negotiation  Period")
beginning on the date of receipt of the Carried Interest  Negotiation Notice and
ending on the earlier to occur of (i) the date upon which  Sonera  U.S.  and AOC
reach agreement on the terms of a Management  Compensation  Amendment or (ii) 60
days after  commencement  of the  Management  Compensation  Negotiation  Period.
During the Management Compensation Negotiation Period, Sonera U.S. and AOC shall
negotiate  in good  faith  to  reach  agreement  on the  terms  of a  Management
Compensation  Amendment.  If Sonera U.S. and AOC reach such agreement during the
Management  Compensation  Negotiation  Period,  then the  parties  hereto  shall
execute all documents as shall be necessary to effectuate such agreement. In the
event that Sonera U.S. and AOC do not reach such agreement during the Management
Compensation  Negotiation Period, then each of Sonera U.S. and AOC shall give to
the other a written  notice of its final  proposal  with respect to a Management
Compensation  Amendment (in whatever  form such party  desires) on or before the
last day of the Management Compensation Negotiation Period and such matter shall
be submitted to arbitration pursuant to

                                     - 32 -

<PAGE>



Section 9.03(b) hereof  (without first complying with the negotiation  procedure
set forth in Section 9.02 hereof),  with the arbitrator selecting one of the two
final proposals.  Upon resolution of such matter by the arbitrator,  the parties
hereto shall execute all documents  necessary to effectuate  the final  proposal
selected by the  arbitrator.  Notwithstanding  the  provisions  of this  Section
4.02(c), the percentage beneficial interest held by AOC in such LLC shall not be
decreased as a result of a Management Compensation Amendment.

                  Section 4.03 Additional Initial  Investment.  Each of AOC and,
if there is no Additional Initial Class A Member, Sonera U.S. shall be entitled,
at the time that an LLC is  formed,  to invest an  additional  amount of cash in
immediately  available  funds (or  otherwise in accordance  with the  applicable
Project Notice and Proposed Business Plan) in such LLC and thereby own a greater
percentage  interest in such LLC than the  minimum  34.5%  beneficial  ownership
interest  required  of Sonera  U.S.  or the  minimum  16%  beneficial  ownership
interest  (including the Carried  Interest)  required of AOC.  Sonera U.S. shall
advise AOC in writing of the aggregate  initial  percentage  interest in the LLC
that Sonera  U.S.  desires to acquire  (the  "Proposed  Sonera U.S.  Initial LLC
Interest"),  such Proposed  Sonera U.S.  Initial LLC Interest to be no less than
34.5% and no greater  than 84%,  such  written  notice to be delivered by Sonera
U.S.  (i) at the time  that  Sonera  U.S.,  as the  Proposing  Party,  submits a
Proposed  Business Plan to AOC pursuant to Section 3.01(b)  hereof,  (ii) at the
time that Sonera U.S., as the Proposal Recipient,  notifies AOC of Sonera U.S.'s
decision  to invest in a  Proposed  Project  submitted  to  Sonera  U.S.  by AOC
pursuant  to  Section  3.01(b)  hereof  or (iii) at the time  that  Sonera  U.S.
notifies  AOC of an  arrangement  to  acquire  a B-  PCS  License  for a  Market
identified in Section 3.01(c) hereof, as applicable. If Sonera U.S.

                                     - 33 -

<PAGE>



proposes to include an  Additional  Initial  Class A Member,  then the  Proposed
Sonera U.S.  Initial LLC Interest  shall be 34.5%.  AOC shall then advise Sonera
U.S. in writing of the aggregate  initial  percentage  interest  (including  the
Carried  Interest)  in the LLC that AOC  shall  acquire  (the "AOC  Initial  LLC
Interest"),  such AOC Initial LLC Interest to be no less than 16% and no greater
than the lesser of (A) 49% and (B) a percentage  interest  that is less than the
Proposed Sonera U.S.  Initial LLC Interest,  such written notice to be delivered
by AOC (i) at the time that AOC, as the Proposal Recipient, notifies Sonera U.S.
of AOC's  decision to invest in a Proposed  Project  submitted  to AOC by Sonera
U.S. pursuant to Section 3.01(b) hereof,  (ii) within 30 days after Sonera U.S.,
as the Proposal Recipient, notifies AOC of Sonera U.S.'s decision to invest in a
Proposed  Project  submitted to Sonera U.S. by AOC  pursuant to Section  3.01(b)
hereof or (iii) within 30 days after Sonera U.S.  notifies AOC of an arrangement
to acquire a B-PCS License for a Market  identified in Section  3.01(c)  hereof.
The actual  aggregate  initial  percentage  interest in the LLC that Sonera U.S.
and, if  applicable,  any  Additional  Initial Class A Member shall acquire (the
"Sonera U.S. Initial LLC Interest") shall then be equal to the lesser of (A) the
Proposed Sonera U.S. Initial LLC Interest and (B) the percentage  interest which
when added to the AOC Initial LLC Interest equals 100%. The amount of cash to be
invested by each of AOC, Sonera U.S. and, if applicable,  any Additional Initial
Class A Member shall be determined in accordance with Section 4.04(a).

                  Section 4.04 Amount of  Investment.  (a) The initial amount of
cash required to be invested by each of AOC, Sonera U.S. and, if applicable, any
Additional Initial Class A Member, as the case may be, in the equity of each LLC
shall  be  equal to the  quotient  of:  (x) the  product  of (A) the  percentage
interest to be acquired by AOC, Sonera U.S. or any Additional Initial Class A

                                     - 34 -

<PAGE>



Member,  as applicable,  expressed as a decimal  multiplied by (B) the Aggregate
Required Capital  Contribution;  divided by (y) 0.85. For purposes of performing
the foregoing  calculation,  the percentage interest to be acquired by AOC shall
not include the Carried Interest.

                  (b) For purposes of determining the amount of cash invested by
Sonera  U.S. in the equity of each LLC formed  pursuant  to Section  2.02 hereof
and,  therefore,  whether  Sonera U.S. has invested an aggregate of $400 million
for purposes of Section 3.01(a) hereof, the amount of cash deemed to be invested
by Sonera U.S. in each LLC shall be equal to the amount of cash  invested in the
equity of each LLC by Sonera  U.S.  and any  Additional  Initial  Class A Member
(exclusive  of such  amounts so invested  that are  re-allocated  to the capital
account of AOC in such LLC in connection with the Carried Interest).

                  Section 4.05 Additional  Initial  Investors.  (a) In the event
that the sum of the Sonera  U.S.  Initial LLC  Interest  and the AOC Initial LLC
Interest does not equal 100%, then Sonera U.S. and AOC shall have 120 days after
the date on which AOC has advised  Sonera U.S. in writing of the AOC Initial LLC
Interest  pursuant to Section  4.03 hereof to obtain  firm  commitments  for the
funding  of the  remaining  Aggregate  Required  Capital  Contribution  by third
parties,  subject to Section  4.05(b)  hereof,  and  Sonera  U.S.  and AOC shall
cooperate in seeking such funding.  If firm  commitments are obtained to provide
the remaining  Aggregate Required Capital  Contribution,  the initial percentage
interest  of each such third party in such LLC shall be equal to the product of:
(x) the quotient of (A) that portion of the remaining Aggregate Required Capital
Contribution  paid by such third  party  divided by (B) the  Aggregate  Required
Capital Contribution; multiplied by (y) 0.85.

                                     - 35 -

<PAGE>



Any third party  investing  in such LLC  pursuant to this  Section 4.05 shall be
deemed a Class C Member in the LLC and the equity  interest  of such third party
in the  LLC  shall  be  designated  as a Class C  Membership  Interest.  If firm
commitments  are not so  obtained,  then an LLC shall not be formed  pursuant to
Section  2.02  hereof  and the  related  B-PCS  License  shall be subject to the
provisions of Section  3.02(b)  hereof.  Notwithstanding  the  investment of any
third  party in such LLC,  the  beneficial  interest  of Sonera U.S. in such LLC
shall,  at all times prior to the LLC Fifth  Anniversary of such LLC, be greater
than the  beneficial  interest in such LLC of AOC or any other  Person  owning a
beneficial interest in such LLC.

                  (b)  No  third  party  shall  be  permitted  to  invest  as an
additional  initial investor in an LLC pursuant to Section 4.05(a) hereof if (A)
such third party,  directly or indirectly,  operates or manages, or beneficially
owns a 20% or greater  interest  in, any  business  engaged in the  provision of
Wireless Services,  and the population within the geographic areas served by the
systems  providing  Wireless Services  operated,  managed or owned by such third
party  (including its Affiliates)  which overlap with geographic areas served by
systems  providing  Wireless Services owned or operated by the USCC Group or the
Aerial  Group,  as  applicable,  is equal  to or  greater  than 2% of the  total
population within the geographic areas of all such systems owned and operated by
the  USCC  Group or the  Aerial  Group,  as  applicable,  or (B) AOC  reasonably
believes the identity of such third party, or the ownership of B-PCS Licenses by
the third party  through its  ownership  of an equity  interest in the  Company,
would be likely to  present  cross-ownership  or  competitive  problems  for any
member  of the USCC  Group or the  Aerial  Group  at the FCC or any  other  U.S.
government  agency or result in a violation of any federal or state law, rule or
regulation applicable to any member of the

                                     - 36 -

<PAGE>



USCC Group or the Aerial Group;  provided,  however, that the provisions of this
Section  4.05(b) shall not be applicable to the USCC Group at any time that USCC
ceases to be an Affiliate of Aerial.


                  Section 4.06  Limitation  on Percentage  Interest.  No Class C
Member,  Minority Class A Member or a Minority Class B Member in an LLC shall be
permitted to hold, directly or indirectly,  an aggregate equity interest in such
LLC, regardless of class, equal to or greater than 20%.

                                    ARTICLE V
                              TRANSFER OF INTEREST

                  Section 5.01  Restrictions on Transfer.  (a) All references in
this Article V to (i) a Class A Member shall be deemed to include each Affiliate
of such Class A Member that holds a  beneficial  interest in an LLC,  and (ii) a
Class B Member shall be deemed to include each  Affiliate of such Class B Member
that holds a beneficial  interest in an LLC. All references in this Article V to
the "Transferring Party" shall be deemed to refer to any Class A Member or Class
B Member that desires to Transfer its beneficial interest or any portion thereof
in an LLC. If either the Majority  Class A Member or the Majority Class B Member
is the  Transferring  Party,  then  the  references  in  this  Article  V to the
"Non-Transferring Party" shall be deemed to refer to the Majority Class B Member
or the Majority Class A Member, respectively.  If any Minority Class A Member or
any Minority Class B Member is the Transferring Party, then the Non-Transferring
Party shall be deemed to refer to (A) in the case of a Minority  Class A Member,
first the Majority Class A Member and

                                     - 37 -

<PAGE>



then the  Majority  Class B Member  and (ii) in the case of a  Minority  Class B
Member,  first the Majority Class B Member and then the Majority Class A Member,
such that,  in each case,  the  provisions  of this Article V shall be satisfied
sequentially with respect to each Non-Transferring Party in the applicable order
of  priority  prior to any  Transfer  by a  Transferring  Party to a Third Party
Transferee (as defined herein).

                  (b)  No  Transfer  by a  Transferring  Party  of a  beneficial
interest in an LLC shall be valid unless (i) such Transfer shall comply with the
provisions  of this  Article V and the  provisions  of Article VI of the Limited
Liability  Company  Agreement  governing  such LLC, (ii) such  transferee  shall
become bound by the terms and provisions of such LLC's  governing  documents and
(iii) all  necessary  approvals  shall have been  obtained  from the FCC and any
other regulatory agencies.

                  (c) Prior to an LLC Fifth  Anniversary,  no Transferring Party
shall Transfer its beneficial interest in such LLC or any portion thereof to any
other Person without the prior written  consent of the  Non-Transferring  Party,
which  consent  may  be  withheld  by the  Non-Transferring  Party  in its  sole
discretion.

                  (d) On or after an LLC Fifth  Anniversary,  each  Transferring
Party shall be permitted to Transfer its beneficial  interest in such LLC or any
portion  thereof to any other Person  without the prior  written  consent of the
Non-Transferring  Party;  provided,  however,  that such Transferring Party must
first comply with the provisions of Sections 5.02 and 5.03 hereof.


                                     - 38 -

<PAGE>



                  (e)  Notwithstanding  the  provisions of Sections  5.01(c) and
5.01(d), a Transferring Party may Transfer its beneficial  interest in an LLC or
any portion thereof to an Affiliate of such Transferring Party at any time after
the   formation  of  such  LLC  without  the  prior   written   consent  of  the
Non-Transferring  Party and without  compliance  with the provisions of Sections
5.02 and  5.03  hereof;  provided,  however,  that,  such  Affiliate  shall be a
wholly-owned subsidiary of such Transferring Party, so that, after giving effect
to such Transfer,  such  Transferring  Party shall continue to own,  directly or
indirectly,  the  percentage  beneficial  interest  in the  LLC  that  it  owned
immediately prior to such Transfer.

                  Section 5.02 Right of First Negotiation. (a) If on or after an
LLC Fifth  Anniversary a  Transferring  Party desires to Transfer its beneficial
interest in an LLC or any portion  thereof  without the prior written consent of
the Non-Transferring Party to a Person other than the Non- Transferring Party or
a  wholly-owned   Subsidiary  of  such   Transferring   Party  (a  "Third  Party
Transferee"), then the Transferring Party must first notify the Non-Transferring
Party in writing of its desire to effect a Transfer,  which  notice  shall state
the  percentage  interest  in the LLC that the  Transferring  Party  desires  to
Transfer  and  refer  to  this  Section  5.02  (the  "Transfer   Notice").   The
Non-Transferring  Party  shall have a period of ten days from the receipt of the
Transfer  Notice within which to provide the  Transferring  Party with a written
notice  that the  Non-Transferring  Party  desires to invoke the  provisions  of
Section 5.02(b) (the "Transfer  Negotiation  Notice").  If the Non- Transferring
Party fails to timely provide a Transfer  Negotiation  Notice or comply with any
of the provisions of Section 5.02(b),  then the Transferring  Party may Transfer
such interest in such LLC

                                     - 39 -

<PAGE>



to a Third  Party  Transferee,  subject to  compliance  with the  provisions  of
Sections 5.01(a) and 5.03 hereof.

                  (b) If the  Non-Transferring  Party timely provides a Transfer
Negotiation Notice to the Transferring  Party pursuant to Section 5.02(a),  then
the Non-Transferring  Party shall have the exclusive right to negotiate with the
Transferring  Party regarding the possible  acquisition by the  Non-Transferring
Party of such  interest of the  Transferring  Party in the LLC for a period (the
"Transfer  Negotiation  Period")  beginning  on  the  date  of  receipt  by  the
Transferring Party of the Transfer  Negotiation Notice and ending on the earlier
to  occur  of  (i)  the  date  upon  which  the   Transferring   Party  and  the
Non-Transferring  Party reach agreement on the terms of the Transfer of such LLC
interest from the Transferring  Party to the  Non-Transferring  Party or (ii) 60
days after the  commencement  of the  Transfer  Negotiation  Period.  During the
Transfer  Negotiation  Period, the Transferring  Party and the  Non-Transferring
Party  shall  negotiate  in good  faith to  reach  agreement  on the  terms of a
Transfer   of  such   LLC   interest   from  the   Transferring   Party  to  the
Non-Transferring  Party. If the parties reach such agreement during the Transfer
Negotiation  Period,  then  the  parties  shall  promptly  prepare  and file all
necessary  applications  with the FCC and any other regulatory  agencies and the
closing of the Transfer of the LLC interest from the  Transferring  Party to the
Non-  Transferring  Party  shall  occur  within 30 days after the receipt of all
necessary FCC and other regulatory  approvals.  In the event that the parties do
not reach  such  agreement  during the  Transfer  Negotiation  Period,  then the
Non-Transferring  Party shall give to the Transferring Party a written notice of
the  Non-Transferring  Party's  final bid to acquire such  interest (in whatever
form the Non-  Transferring  Party  desires)  on or  before  the last day of the
Transfer Negotiation Period, which final

                                     - 40 -

<PAGE>



bid the Transferring Party shall have the right to accept (A) for a period of 30
days after its receipt thereof,  during which 30-day period such final bid shall
be irrevocable, and (B) for a period of an additional 60 days thereafter, during
which  additional  60-day  period  such  final bid shall be  revocable  upon the
Transferring   Party's   receipt  of  written  notice  of  revocation  from  the
Non-Transferring  Party prior to the  Transferring  Party's  acceptance  of such
final bid.

                  (c) In the event that the  Transferring  Party neither reaches
agreement  via  negotiation  with the  Non-Transferring  Party to Transfer  such
interest   in  the  LLC  to  the   Non-Transferring   Party  nor   accepts   the
Non-Transferring  Party's  final  bid  pursuant  to  Section  5.02(b),  then the
Transferring  Party shall be permitted to Transfer such interest in the LLC to a
Third  Party  Transferee;   provided,  however,  that  in  no  event  shall  the
Transferring  Party Transfer,  or enter into an agreement to Transfer,  such LLC
interest  to a Third  Party  Transferee  unless (i) the  Transferring  Party has
negotiated  in good faith  during the  Transfer  Negotiation  Period to effect a
Transfer of such  interest  to the  Non-Transferring  Party  pursuant to Section
5.02(b),  (ii) the Transferring Party enters into a binding agreement within 180
days after the termination of the latest Transfer Negotiation Period to Transfer
such  interest  to a Third  Party  Transferee  at a higher  price than the price
offered to the Transferring Party by any Non-Transferring Party in its final bid
and (iii) the  Transferring  Party and the Third Party  Transferee  shall comply
with the  provisions  of Section  5.03  hereof.  If such  binding  agreement  is
terminated  prior to consummation of such Transfer,  then the provisions of this
Section 5.02 shall once again become  applicable  to such  Transferring  Party's
interest in the LLC.


                                     - 41 -

<PAGE>



                  (d) For  purposes  of this  Section  5.02,  if the  price in a
binding agreement to consummate a Transfer,  or in the Non-Transferring  Party's
final  bid,  is to be paid in  something  other  than money in a lump sum at the
closing,  then the Transferring Party and the  Non-Transferring  Party shall use
their reasonable best efforts to reach agreement as to an equivalent in monetary
terms, which shall constitute the price for the purposes of Section 5.02(c)(ii).
In the event that the price in a binding agreement or final bid is to be paid in
whole or in part in shares of a public  company  and such shares are traded on a
national  stock  exchange,  the  value  of  such  securities,  for  purposes  of
calculating  such price,  shall be the average  closing price for such shares as
reported in The Wall Street  Journal for the twenty  trading  days ending on and
including  the  third  trading  day  prior to the  date of the  Non-Transferring
Party's  written notice of its final bid as set forth in Section  5.02(b) or the
date of the execution of the binding agreement as referenced in Section 5.02(c),
as the case may be; provided, however,  appropriate adjustments shall be made to
the value of such shares for (i)  extraordinary  dividends,  stock splits or any
other extraordinary  distributions,  (ii) a combination of such public company's
outstanding  shares into a smaller number of shares or (iii) any  reorganization
or  reclassification  of such public  company's  shares or any  consolidation or
merger with another  company.  If such an agreement cannot be reached within ten
days  after  the  Transferring  Party  (in  the  case  of a  final  bid)  or the
Non-Transferring  Party  (in the case of a binding  agreement  to  consummate  a
Transfer) receives written notice of the price offered, such equivalent shall be
determined by an appraiser  agreed upon (and paid  equally) by the  Transferring
Party and the Non- Transferring Party or, if they cannot agree upon an appraiser
within  ten  days  after  the end of  such  initial  ten-day  period,  by  three
appraisers,  one of whom  shall be chosen  within ten days after the end of such
second ten-day period by the  Transferring  Party (and paid by the  Transferring
Party), one

                                     - 42 -

<PAGE>



of whom shall be chosen (and paid) by the Non-Transferring Party within the same
period,  and the third of whom shall be chosen by the first two so chosen within
an  additional  ten days and paid  equally  by the  Transferring  Party  and the
Non-Transferring  Party.  The decision of the  agreed-upon  appraiser or, as the
case may be, a majority  of the three  appraisers,  shall be made within 45 days
after he or they,  as the case may be, are chosen and shall be final and binding
upon the  Transferring  Party and the  Non-Transferring  Party. All time periods
specified  in  Sections  5.02(a)  through (c) shall be extended by the length of
time necessary for such  appraiser(s)  to be chosen and for such appraisal to be
made (if it becomes necessary).

                  Section 5.03 Tag-Along  Rights.  (a) Subject to the provisions
of Section  5.03(b)  hereof,  a Majority  Class A Member  shall not Transfer any
portion of its  beneficial  interest in an LLC formed  pursuant to Section  2.02
hereof to a Third Party  Transferee  unless the Majority Class B Member is given
the opportunity to Transfer to the Third Party  Transferee up to that percentage
of such Majority Class B Member's beneficial interest in such LLC that bears the
same  proportion  to the total  percentage  beneficial  interest of the Majority
Class B  Member  in the LLC as the  percentage  beneficial  interest  in the LLC
proposed to be  Transferred  by the  Majority  Class A Member bears to the total
percentage  beneficial  interest in the LLC of the Majority Class A Member, such
transfer to be  concurrent  with the Transfer by the Majority  Class A Member to
the Third Party Transferee and at a price per percentage beneficial interest and
on terms and subject to  conditions  that are no less  favorable to the Majority
Class B Member than those to the Majority  Class A Member.  The Majority Class B
Member may exercise such tag-along  right by giving written notice (a "Tag-Along
Notice") of such  exercise to the Majority  Class A Member no later than 15 days
after the Majority

                                     - 43 -

<PAGE>



Class A Member has provided  written  notice to the  Majority  Class B Member of
such proposed  Transfer,  such notice by the Majority  Class A Member to include
the identity of the Third Party  Transferee,  the  percentage  interest that the
Majority  Class A Member will  Transfer to the Third  Party  Transferee  and the
price,  terms and  conditions  upon which such Transfer is to be effected.  Such
Tag-Along Notice shall specify the percentage interest that the Majority Class B
Member  shall  Transfer to the Third Party  Transferee  pursuant to this Section
5.03. If the Majority Class B Member  exercises such tag-along  right,  then the
Majority  Class A Member  shall not Transfer its LLC interest to the Third Party
Transferee  unless the Third Party  Transferee also acquires the interest of the
Majority Class B Member specified in the Tag-Along Notice in accordance with the
provisions of this Section 5.03.

                  (b) In the event that the  Transfer  by the  Majority  Class A
Member would result in the Majority  Class A Member no longer holding a majority
of the Aggregate Class A Membership Interest Percentage, then the Majority Class
B Member shall be entitled to Transfer to the Third Party  Transferee up to 100%
of the Majority  Class B Member's  beneficial  interest in such LLC. Any partial
exercise by the Majority  Class B Member of, or failure by the Majority  Class B
Member to exercise, its rights set forth in this Section 5.03 shall not prohibit
the Majority Class B Member from  exercising  such rights in connection with one
or more subsequent Transfers to which this Section 5.03 is applicable.

                  Section 5.04 Limitation on Non-Transferring  Party's Rights. A
Non-Transferring  Party or a Majority  Class B Member  shall only be entitled to
exercise its rights as set forth in

                                     - 44 -

<PAGE>



Sections 5.02 or 5.03 hereof,  respectively,  with respect to an LLC at any time
that  either the Non-  Transferring  Party (and any  Affiliate  thereof)  or the
Majority  Class B Member (and any  Affiliate  thereof),  respectively,  holds at
least a 15% beneficial interest in such LLC.

                                   ARTICLE VI
                                   TECHNOLOGY

                  Section 6.01 Technological  Changes and Advances.  The parties
hereto  agree that one of the  primary  reasons  for  forming the Venture is the
parties'  mutual  interest in GSM  Technology.  Sonera  U.S.  and AOC shall work
together to  determine,  with respect to the system  operated by each LLC formed
pursuant to Section  2.02  hereof,  the  nature,  timing and  implementation  of
technological changes and advances, including changes involving the evolution of
GSM  Technology  and the  development  of  subsequent  technologies  based on or
derived  from GSM  Technology,  consistent  with  such  mutual  interest  in GSM
Technology.  In making such  determination,  Sonera U.S. and AOC shall give full
consideration  to  the  operational  plans  and  capabilities  of  AOC  and  its
Affiliates  with respect to other B-PCS  Markets  owned or managed by AOC or its
Affiliates,  as well as the parties' mutual interest in maintaining  consistency
between  the  technology  utilized by each LLC formed  pursuant to Section  2.02
hereof and the  technology  utilized  by (i) each other LLC formed  pursuant  to
Section 2.02  hereof,  (ii) AOC and its  Affiliates  with respect to other B-PCS
Markets owned or managed by AOC or its Affiliates  and (iii) other  providers of
B-PCS in the United States utilizing GSM Technology.  If Sonera U.S. and AOC are
unable to agree  regarding  the  proposed  implementation  of any  technological
changes or advances with respect

                                     - 45 -

<PAGE>



to any LLC formed  pursuant  to Section  2.02 hereof (a  "Technology  Dispute"),
then,  prior to such  implementation,  Sonera U.S.  and AOC shall  address  such
Technology  Dispute  pursuant  to the  provisions  of Section  9.02 and  Section
9.03(b) hereof.

                                   ARTICLE VII
                                   NAME OF LLC

                  Section  7.01  Name  of  LLC.  At  all  times  that  AOC or an
Affiliate  thereof is  managing  the B-PCS  System of an LLC formed  pursuant to
Section 2.02 hereof, the business of such LLC shall be carried on using the same
name,  and only  such  name,  as that  used  from  time to time by Aerial in the
Markets identified on Schedule 3.05, with such variations and changes thereto as
Aerial shall deem useful,  appropriate  or necessary for any legal or reasonable
business  purpose,  giving due  consideration to the potential impact on any LLC
formed  pursuant  to Section  2.02  hereof,  and Aerial  shall  grant each LLC a
license  to use such  name,  all  pursuant  to the terms and  conditions  of the
Trademark License Agreement in substantially the form attached hereto as Exhibit
C.

                                  ARTICLE VIII
                            MANAGEMENT AND OPERATION

                  Section  8.01 Board of  Managers.  (a) The Class A Members and
the  Class B  Members  will  appoint  a Board of  Managers  for each LLC  formed
pursuant to Section 2.02 hereof (an "LLC  Board"),  which LLC Board in each case
will consist of seven Managers. Four of the

                                     - 46 -

<PAGE>



Managers shall be elected by the Class A Members and three of the Managers shall
be  elected by the Class B Members.  The Class C Members,  if any,  shall not be
entitled  to elect any  Managers  to the LLC  Board.  In  electing  Managers  to
represent the Class A Members and the Class B Members on the LLC Board, the vote
of a  majority  of the  Aggregate  Class A  Membership  Interest  Percentage  or
Aggregate Class B Membership Interest Percentage, respectively, shall govern.

                  (b) Sonera  U.S.  agrees  that,  as long as Sonera  U.S. or an
Affiliate of Sonera U.S. is the Majority  Class A Member and AOC or an Affiliate
of AOC  directly  or  indirectly  owns a  beneficial  interest  in an LLC formed
pursuant  to  Section  2.02  hereof,   Sonera  U.S.  will  not  designate  as  a
representative of Sonera U.S. on the LLC Board of such LLC any individual who is
an officer,  director or representative of any third party (other than Sonera or
Sonera  U.S.) that is in  Competition  with AOC or any  Affiliate  of AOC to any
significant  extent.  AOC agrees that,  as long as AOC or an Affiliate of AOC is
the  Majority  Class B Member and Sonera  U.S.  or an  Affiliate  of Sonera U.S.
directly or indirectly  owns a beneficial  interest in an LLC formed pursuant to
Section 2.02 hereof,  AOC will not designate as a  representative  of AOC on the
LLC  Board  of  such  LLC  any  individual  who  is  an  officer,   director  or
representative  of any  third  party  (other  than  Aerial  or  AOC)  that is in
Competition  with Sonera U.S. or any Affiliate of Sonera U.S. to any significant
extent.

                  (c) In addition, if (i) either AOC or an Affiliate thereof, on
the one hand,  or Sonera U.S. or an Affiliate  thereof,  on the other hand,  has
appointed as its  representative  to the LLC Board of any LLC formed pursuant to
Section 2.02 hereof an officer or director of a third party,  (ii) either AOC or
any Affiliate thereof, on the one hand, or Sonera U.S. or any Affiliate thereof,
on the other

                                     - 47 -

<PAGE>



hand,  jointly  pursuant to this Agreement or  individually,  has entered into a
binding  agreement  to acquire a license  issued by the FCC to provide  Wireless
Services or to operate or manage a system providing Wireless Services, (iii) the
presence of such officer or director of such third party on such LLC Board would
prevent such  acquisition,  operation or management due to the  restrictions  on
spectrum  aggregation  set forth in  Section  20.6 of the FCC rules and (iv) the
party  committing  to acquire  such license or operate or manage such system has
requested a waiver from the FCC with respect to the application of Section 20.6,
then the party that  appointed  such third party  officer or director  agrees to
replace such third party officer or director as its  representative  on such LLC
Board with a representative that will not prevent such acquisition, operation or
management pursuant to Section 20.6 of the FCC rules; provided, however, that if
such waiver subsequently is granted by the FCC, then such third party officer or
director  shall again become  eligible to serve on such LLC Board.  All expenses
incurred  in  connection   with  the  preparation  and  filing  of  such  waiver
application shall be the responsibility of the party requesting such waiver.

                  Section 8.02  Unanimous  Approval.  No LLC formed  pursuant to
Section  2.02  hereof  shall  take  any of the  following  actions  without  the
unanimous approval of its LLC Board:

                  (i)  prior  to the LLC  Fifth  Anniversary  of such  LLC,  any
         transfer,  assignment or disposition of all or any substantial  portion
         of the  assets of such LLC,  any plan or  agreement  by which  such LLC
         disaggregates  or  partitions  its B-PCS  License or assigns  its B-PCS
         License  or  makes   spectrum   available   through  a  resale  or  use
         arrangement, or any Restricted Business Combination of such LLC with or
         into any other entity, in each case whether

                                     - 48 -

<PAGE>



         involving  a  member  of such  LLC,  an  Affiliate  of such LLC or of a
         member, or a third party; or

                  (ii) any other action for which unanimous  approval of the LLC
         Board  is  required  as set  forth  in the  Limited  Liability  Company
         Agreement governing such LLC.

                  Section 8.03 Right of First Negotiation. (a) If on or after an
LLC Fifth  Anniversary  the  Majority  Class A Member  desires  to enter into or
permit such LLC to enter into any agreement with respect to any matter set forth
in clause (i) of Section  8.02  hereof (a  "Restricted  LLC  Action"),  then the
Majority Class A Member must first notify the Majority Class B Member in writing
of its desire to effect a Restricted LLC Action, which notice shall indicate the
type of Restricted LLC Action that the Majority Class A Member desires to effect
and refer to this  Section  8.03  (the  "Restricted  LLC  Action  Notice").  The
Majority  Class B Member shall have a period of ten days from the receipt of the
Restricted LLC Action Notice within which to provide the Majority Class A Member
with a written  notice that the  Majority  Class B Member  desires to invoke the
provisions of Section 8.03(b) (the "Restricted LLC Action Negotiation  Notice").
If the Majority  Class B Member fails to timely  provide a Restricted LLC Action
Negotiation Notice or comply with any of the provisions of Section 8.03(b), then
the  Majority  Class A Member and the LLC may  consummate  such  Restricted  LLC
Action with one or more Persons other than the Majority Class B Member.

                  (b)  If  the  Majority  Class  B  Member  timely   provides  a
Restricted LLC Action Negotiation Notice to the Majority Class A Member pursuant
to Section 8.03(a), then the Majority

                                     - 49 -

<PAGE>



Class B Member shall have the  exclusive  right to  negotiate  with the Majority
Class A Member (with the Majority Class A Member representing the LLC) regarding
the possible consummation of the Restricted LLC Action with the Majority Class B
Member rather than with one or more other Persons for a period (the  "Restricted
LLC Action Negotiation Period") beginning on the date of receipt by the Majority
Class A Member of the Restricted LLC Action Negotiation Notice and ending on the
earlier to occur of (i) the date upon which the Majority  Class B Member and the
Majority Class A Member reach agreement on the terms of the  consummation of the
Restricted  LLC Action with the Majority  Class B Member rather than with one or
more other  Persons,  or (ii) 60 days after  commencement  of the Restricted LLC
Action Negotiation Period.  During the Restricted LLC Action Negotiation Period,
the Majority Class A Member and the Majority  Class B Member shall  negotiate in
good faith to reach  agreement on the terms of a consummation  of the Restricted
LLC Action with the Majority  Class B Member  rather than with one or more other
Persons.  If the parties reach such  agreement  during the Restricted LLC Action
Negotiation  Period,  then  the  parties  shall  promptly  prepare  and file all
necessary  applications  with the FCC and any other regulatory  agencies and the
closing of the  Restricted  LLC Action with the  Majority  Class B Member  shall
occur within 30 days after  receipt of all  necessary  FCC and other  regulatory
approvals.  In the event that the parties do not reach such agreement during the
Restricted LLC Action Negotiation Period, then the Majority Class B Member shall
give to the Majority  Class A Member a written  notice of the  Majority  Class B
Member's  final bid to consummate  such  Restricted  LLC Action with the LLC (in
whatever form the Majority Class B Member  desires) on or before the last day of
the Restricted LLC Action Negotiation Period, which final bid the Majority Class
A Member  shall  have the right to accept  (A) for a period of 30 days after its
receipt thereof, during which 30-day period such final bid

                                     - 50 -

<PAGE>



shall be irrevocable,  and (B) for a period of an additional 60 days thereafter,
during which additional 60-day period such final bid shall be revocable upon the
Majority  Class A  Member's  receipt of written  notice of  revocation  from the
Majority  Class B Member prior to the Majority  Class A Member's  acceptance  of
such final bid.

                  (c) In the  event  that the  Majority  Class A Member  neither
reaches agreement via negotiation with the Majority Class B Member to consummate
the  Restricted  LLC Action  with the  Majority  Class B Member nor  accepts the
Majority  Class B  Member's  final bid  pursuant  to Section  8.03(b),  then the
Majority  Class A  Member  and the LLC  shall be  permitted  to  consummate  the
Restricted  LLC Action with one or more Persons other than the Majority  Class B
Member; provided, however, that in no event shall the Majority Class A Member or
the LLC consummate, or enter into an agreement to consummate, the Restricted LLC
Action  with such  other  Persons  unless  (i) the  Majority  Class A Member has
negotiated in good faith during the Restricted LLC Action  Negotiation Period to
effect such  Restricted LLC Action with the Majority Class B Member  pursuant to
Section  8.03(b) and (ii) the  Majority  Class A Member or the LLC enters into a
binding  agreement  within 180 days after the  termination of the Restricted LLC
Action  Negotiation  Period to consummate such Restricted LLC Action with one or
more Persons  other than the Majority  Class B Member at a higher price than the
price offered to the Majority  Class A Member or the LLC by the Majority Class B
Member in its final bid.

                  (d) For  purposes  of this  Section  8.03,  if the  price in a
binding  agreement to  consummate a  Restricted  LLC Action,  or in the Majority
Class B Member's final bid, is to be paid

                                     - 51 -

<PAGE>



in something  other than money in a lump sum at the  closing,  then the Majority
Class A Member and the Majority Class B Member shall use their  reasonable  best
efforts to reach  agreement as to an equivalent in monetary  terms,  which shall
constitute the price for the purposes of Section 8.03(c)(ii).  In the event that
the price in a binding  agreement or final bid is to be paid in whole or in part
in shares of a public  company  and such  shares are traded on a national  stock
exchange, the value of such securities,  for purposes of calculating such price,
shall be the  average  closing  price for such  shares as  reported  in The Wall
Street  Journal for the twenty  trading days ending on and  including  the third
trading day prior to the date of the Majority Class B Member's written notice of
its final bid as set forth in Section  8.02(b) or the date of the  execution  of
the binding  agreement as  referenced  in Section  8.02(c),  as the case may be;
provided,  however,  appropriate  adjustments shall be made to the value of such
shares for (i) extraordinary dividends,  stock splits or any other extraordinary
distributions,  (ii) a combination of such public company's  outstanding  shares
into a smaller number of shares or (iii) any reorganization or  reclassification
of such public  company's  shares or any  consolidation  or merger with  another
company.  If such an  agreement  cannot be  reached  within  ten days  after the
Majority  Class A Member  (in the case of a final bid) or the  Majority  Class B
Member  (in the case of a binding  agreement  to  consummate  a  Restricted  LLC
Action) receives  written notice of the price offered,  such equivalent shall be
determined by an appraiser  agreed upon (and paid equally) by the Majority Class
A Member  and the  Majority  Class B Member  or, if they  cannot  agree  upon an
appraiser within ten days after the end of such initial ten-day period, by three
appraisers,  one of whom  shall be chosen  within ten days after the end of such
second  ten-day  period by the Majority Class A Member (and paid by the Majority
Class A Member),  one of whom shall be chosen (and paid) by the Majority Class B
Member within the same period, and the third of whom shall be

                                     - 52 -

<PAGE>



chosen by the first two so chosen within an additional ten days and paid equally
by the Majority Class A Member and the Majority Class B Member.  The decision of
the  agreed-upon  appraiser  or,  as the case may be, a  majority  of the  three
appraisers,  shall be made within 45 days after he or they,  as the case may be,
are chosen and shall be final and binding upon the  Majority  Class A Member and
the  Majority  Class B Member.  All time periods  specified in Sections  8.03(a)
through  (c)  shall  be  extended  by the  length  of time  necessary  for  such
appraiser(s)  to be  chosen  and for such  appraisal  to be made (if it  becomes
necessary).

                  (e) The  Majority  Class B Member  shall  not be  entitled  to
exercise its rights as set forth in this Section 8.03 with respect to any LLC at
any time that the Majority Class B Member (and any Affiliate thereof) holds less
than a 15% beneficial interest in such LLC.

                  Section  8.04  Management  and  Operation.   Each  LLC  formed
pursuant to Section 2.02 hereof shall, as of the date of formation, enter into a
management  agreement with AOC or an Affiliate of AOC in substantially  the form
attached hereto as Exhibit D (the "Management  Agreement") pursuant to which AOC
or an Affiliate of AOC shall manage the daily  operations of the B-PCS system of
such LLC. If the System  Manager is not AOC but rather an Affiliate of AOC, then
AOC shall cause such Affiliate to perform the covenants and  obligations of such
Affiliate set forth in the Management Agreement and shall make available to such
Affiliate  sufficient  resources  to enable such  Affiliate  to so perform.  The
Management  Agreement  between  AOC or its  Affiliate  and the LLC  shall not be
terminated by the LLC except pursuant to the terms thereof.


                                     - 53 -

<PAGE>



                                   ARTICLE IX
                                    DISPUTES

                  Section   9.01   General.   The   parties   agree  to  address
disagreements  and disputes  arising out of or related to this  Agreement or the
breach hereof through the procedures set forth in this Article IX.

                  Section 9.02 Negotiation Procedure. (a) The Aerial Parties, on
the one hand,  and Sonera U.S., on the other hand,  shall  designate one or more
employees  or  representatives  who will be the initial  contact  for  resolving
disputes  that may arise under this  Agreement  that do not involve an amount in
excess of $50,000.  The Aerial  Parties  and Sonera U.S.  shall first raise such
disputes with a designated  employee or  representative  of the other party. The
designated  employees  or  representatives  shall work  together  to resolve the
relevant  issue in a manner that meets the interests of both the Aerial  Parties
and Sonera U.S.,  or until the issue is referred to  designated  officers of the
parties as set forth in Section 9.02(b).  Any disputes that involve an amount in
excess of $50,000 shall be referred to the designated officers of the parties as
set forth in Section 9.02(b).

                  (b) The Aerial  Parties and Sonera U.S.  shall also  designate
one or more  officers  who will review (i)  disputes  that  involve an amount in
excess  of  $50,000  or  (ii)   disputes  that  the   designated   employees  or
representatives  are unable to resolve pursuant to Section  9.02(a).  Any matter
not resolved by such designated employees within 30 days after the date on which
a party hereto first notifies a designated  employee of the other party shall be
referred to such designated

                                     - 54 -

<PAGE>



officers for resolution.  The designated officers shall work together to resolve
the  disputes so referred to them in a manner that meets the  interests  of both
the Aerial Parties and Sonera U.S.,  either until such agreement is reached,  or
until an  impasse is  declared  by either  the  Aerial  Parties or Sonera U.S.;
provided,  however,  that an impasse  shall not be declared by either the Aerial
Parties or Sonera U.S.  prior to the  fifteenth day after such dispute has first
been referred to such designated officers.  Notice of declaration of any impasse
shall be given pursuant to Section 11.02 hereof.

                  (c) The employees or  representatives  and officers  initially
designated  by the Aerial  Parties and Sonera U.S.  for purposes of this Section
9.02 are set forth in  Schedule  9.02(c) to this  Agreement.  Parties may change
such  designation  by giving  notice of such change  pursuant  to Section  11.02
hereof.

                  (d) Any resolution of a dispute by the designated employees or
representatives pursuant to Section 9.02(a) hereof or by the designated officers
pursuant to Section 9.02(b) hereof shall be in writing signed by such persons on
behalf of the  parties.  Notwithstanding  any  provision  of this Article IX, no
resolution of any dispute by any designated employee,  representative or officer
shall  constitute  an  amendment of this  Agreement  without the approval of the
respective boards of directors of each party hereto.

                  Section 9.03 Unresolved  Disputes.  (a) Except as set forth in
Section 9.03(b)  hereof,  the parties shall be entitled to exercise or resort to
any and all rights and remedies provided in this

                                     - 55 -

<PAGE>



Agreement  or at law or in equity with respect to any  controversy  or claim not
resolved through the procedures set forth in Section 9.02 hereof.

                  (b) Any Technology  Dispute  arising  pursuant to Section 6.01
hereof not resolved  through the procedures set forth in Section 9.02 hereof and
any final  proposals  submitted in  connection  with a  Management  Compensation
Amendment  pursuant to Section  4.02(c) hereof shall be settled by  arbitration,
which  shall  be  final  and   non-appealable,   administered  by  the  American
Arbitration  Association in accordance with its Commercial Rules and judgment on
the  award  rendered  by the  arbitrator  may be  entered  in any  court  having
jurisdiction  thereof.  The  arbitration  proceeding  shall be  conducted in the
Washington, D.C. metropolitan area by one neutral arbitrator,  unless either the
Aerial Parties or Sonera U.S.  notifies the other,  prior to commencement of the
procedure to select an  arbitrator,  that such Aerial Parties or Sonera U.S., as
applicable, desire to have the arbitration proceeding conducted by three neutral
arbitrators.  The  arbitrator  shall have the  authority  to award any remedy or
relief that a court of competent  jurisdiction could order or grant,  including,
without  limitation,  the  issuance of an  injunction.  However,  any party may,
without inconsistency with this arbitration provision, apply to any court having
jurisdiction hereof and seek interim provisional,  injunctive or other equitable
relief until the  arbitration  award is rendered or the controversy is otherwise
resolved.  The  arbitrator  shall set forth the  arbitration  award in a written
opinion  issued  within 90 days from the date of selection  of such  arbitrator,
unless  such  90-day  period is extended  by mutual  agreement  of the  parties.
Neither a party or an  Affiliate  thereof nor an  arbitrator  may  disclose  the
existence,  content,  or results of any arbitration  hereunder without the prior
written  consent of all parties,  except as necessary  in court  proceedings  to
enforce this

                                     - 56 -

<PAGE>



arbitration  provision  or an award  rendered  hereunder,  or to obtain  interim
relief, or as otherwise  required by law (including the requirement of Aerial or
any Affiliate  thereof to disclose such terms under the federal  securities laws
or under the  rules of any  securities  exchange  on which  its  securities  are
listed,  and including  the  requirement  of Sonera or any Affiliate  thereof to
disclose  such terms under the  securities  laws of Finland or other  applicable
jurisdictions).   The  parties   acknowledge  that  this  contract  evidences  a
transaction  involving  interstate  commerce.  Notwithstanding any choice of law
provision included in this Agreement,  the United States Federal Arbitration Act
shall govern the interpretation and enforcement of this arbitration provision.

                  Section 9.04 Jurisdiction;  Consent to Service of Process. (a)
Subject to and in  furtherance  of the  provisions of Section  9.03,  each party
hereby irrevocably consents and submits to the jurisdiction of the United States
District  Court  for the  District  of  Delaware  and any  court of the State of
Delaware in any action,  suit or proceeding  arising out of,  resulting  from or
relating to this Agreement,  and agrees that any such action, suit or proceeding
shall be brought  only in such courts (and waives any  objection  based on forum
non conveniens or any other objection to venue therein); provided, however, that
such  consent to  jurisdiction  is solely for the  purpose  referred  to in this
Section  9.04  and  shall  not  be  deemed  to be a  general  submission  to the
jurisdiction  of said  courts  or the  State  of  Delaware  other  than for such
purpose.

                  (b) Sonera U.S.  hereby  irrevocably  appoints The Corporation
Trust Company, at its office at 1209 Orange Street, Wilmington, Delaware, United
States of  America,  its lawful  agent and  attorney  to accept and  acknowledge
service of any and all process against it in any action, suit or

                                     - 57 -

<PAGE>



proceeding  arising out of,  resulting from or relating to this  Agreement,  and
upon whom  such  process  may be  served,  with the same  effect as if it were a
resident  of the  State of  Delaware,  and had been  lawfully  served  with such
process  in such  jurisdiction,  and waives all claim of error by reason of such
service,  provided that in the case of any service upon such agent and attorney,
the Aerial  Parties  shall also  deliver a copy  thereof to Sonera  U.S.  at the
address and in the manner  specified  in Section  11.02.  In the event that such
agent and  attorney  resigns or otherwise  becomes  incapable of acting as such,
Sonera U.S. will appoint a successor agent and attorney in Wilmington, Delaware,
reasonably  satisfactory to the Aerial  Parties,  with like powers or, if Sonera
U.S. fails to make such appointment, Sonera U.S. hereby authorizes either Aerial
Party to appoint  such agent.  Sonera  U.S.  shall pay the annual fee due to The
Corporation  Trust Company or such successor  agent for acting in such capacity;
provided,  however,  that if Sonera U.S.  fails to make such  payment,  then the
Aerial Parties shall be permitted to do so.

                                    ARTICLE X
                         REPRESENTATIONS AND WARRANTIES

                  Each party hereby  represents  and warrants to the other party
as follows (each party making said  representations  and warranties as to itself
and as to and on behalf of each of its Affiliates which is a party to any or all
of the  agreements  and  instruments  which are being  executed and delivered in
connection herewith):


                                     - 58 -

<PAGE>



                  Section 10.01 Organization and Standing.  It is a corporation,
duly  organized,  validly  existing and in good  standing  under the laws of the
jurisdiction of its organization, has all requisite authority and power to carry
on its business as now being  conducted  by it, and is in good  standing in each
jurisdiction in which the nature of the business  conducted by it requires it to
be qualified therein to do business.

                  Section 10.02 Authorization. It has taken all action necessary
for  the  authorization,  execution,  delivery  and  performance  by it of  this
Agreement and the other  agreements being delivered  simultaneously  herewith to
which it is a party,  and when this Agreement and other  agreements are executed
and delivered by it, they will  constitute its valid and binding  obligations in
accordance with their respective terms. It has all necessary corporate and other
power with respect to the foregoing.

                  Section 10.03 Litigation. It is not a party to any pending or,
to the best of its knowledge  threatened,  litigation or other proceeding which,
if adversely  determined,  would have a material adverse effect upon the Venture
or any LLC formed  pursuant  to Section  2.02  hereof or such LLC's  tangible or
intangible assets or operations.

                  Section  10.04  Absence of  Conflict.  Neither the  execution,
delivery or performance by it of this Agreement or of any other agreements which
are being executed and delivered simultaneously herewith to which it is a party,
nor the consummation of the transactions herein or therein contemplated, nor the
fulfillment of or compliance with the terms and conditions hereof or

                                     - 59 -

<PAGE>



thereof,  will  (nor with the  giving of notice or lapse of time or both  would)
conflict with its charter,  bylaws or other  instrument  pursuant to which it is
organized,  or result in a breach of or  constitute a default  under or conflict
with any material contract, agreement or instrument to which it is a party or by
which it or any of its  properties  are bound,  or any law,  rule, or regulation
applicable  to it or any of its  properties.  Any third party,  governmental  or
administrative  consents or approvals  which are required in connection with the
foregoing have been obtained and are in full force and effect.

                  Section 10.05 Absence of  Undisclosed  Liabilities.  It has no
material  debts,  liabilities,   contracts  or  other  obligations  which  could
reasonably  be  expected  to affect the  Venture or any LLC formed  pursuant  to
Section 2.02 hereof in a materially adverse manner.

                                   ARTICLE XI
                                  MISCELLANEOUS

                  Section  11.01   Confidentiality.   (a)  In  addition  to  any
obligations of  confidentiality  pursuant to other  agreements  already existing
between  the  parties  hereto  (which  this  Section  11.01 is not  intended  to
supersede with respect to information  disclosed  prior to the execution of this
Agreement),  each party hereto will,  and will cause its  Affiliates to, hold in
confidence  and not  disclose to any of its own  personnel  or  personnel of its
Affiliates  not having a need to know or to any third  party  without  the prior
written consent of the other parties hereto: (i) any information  received by it
from the other parties in connection with the transactions  contemplated  hereby
or (ii) any specific  terms of this Agreement or any agreement  being  delivered
simultaneously herewith.

                                     - 60 -

<PAGE>



                  (b) The foregoing  obligation  of confidence  shall extend for
the term of this Agreement and any extensions hereof and for a period of 5 years
thereafter;  provided,  however, that no party shall be obligated to maintain in
confidence information:

                  (i) which is or becomes  part of the public  domain other than
         through  breach of this Agreement or through the fault of the receiving
         party;

                  (ii) which is or becomes available to the receiving party from
         a  source  other  than  the  disclosing  party,  which  source  has  no
         obligation to the disclosing party in respect thereof;

                  (iii)  which  is made  available  by the  disclosing  party in
         written  form  to a  third  party  which  is  not an  Affiliate  of the
         disclosing party on an unrestricted basis;

                  (iv)  which is required to be disclosed by law; or

                  (v) disclosure of which is mutually agreed to by the parties.

                  (c) If any party hereto  discloses such information to a third
party, such disclosing party shall ensure that suitable  undertakings of secrecy
are imposed upon such third party which are no less stringent than those of this
Section 11.01.


                                     - 61 -

<PAGE>



                  Section  11.02   Notices.   All  notices,   claims  and  other
communications hereunder shall be in writing and shall be made by hand delivery,
facsimile, or overnight air courier guaranteeing next day delivery, as follows:

                  (a)  If to the Aerial Parties, at:

                           Aerial Communications, Inc.
                           8410 West Bryn Mawr Avenue
                           Suite 1100
                           Chicago, Illinois  60631
                           Attention:  Donald W. Warkentin
                           Telephone:  (773) 399-4145
                           Facsimile:  (773) 399-7997

                  with a copy (which shall not constitute notice) to:

                           Telephone and Data Systems, Inc.
                           30 North LaSalle Street
                           Suite 4000
                           Chicago, Illinois  60602
                           Attention:  LeRoy T. Carlson, Jr.
                           Telephone:  (312) 630-1900
                           Facsimile:  (312) 630-9299

                  and a copy (which shall not constitute notice) to:

                           Sidley & Austin
                           One First National Plaza
                           42nd Floor - SW
                           Chicago, Illinois  60603
                           Attention:  Michael G. Hron, Esq.
                           Telephone:  (312) 853-2030
                           Facsimile:  (312) 853-7036


                                     - 62 -

<PAGE>



                  (b) if to Sonera U.S., at:

                           Sonera Ltd.
                           P.O. Box 106
                           FIN-00051-TELE
                           Teollisuuskatu 15, Helsinki
                           Attention: Maire Laitinen, Esq.
                           Telephone:  011-35-8-2040-3641
                           Facsimile:  011-35-8-2040-3414

                  with a copy (which shall not constitute notice) to:

                           Patton Boggs, L.L.P.
                           2550 M. Street, N.W.
                           Washington, D.C.  20037-1350
                           Attention:  Richard M. Stolbach, Esq.
                           Telephone:  (202) 457-6324
                           Facsimile:  (202) 457-6315


or at such other address as any party may from time to time furnish to the other
parties by a notice  given in  accordance  with the  provisions  of this Section
11.02.  All such  notices and  communications  shall be deemed to have been duly
given at the time  delivered  by hand,  if  personally  delivered;  when receipt
confirmed, if sent by facsimile; and the next Business Day after timely delivery
to the courier,  if sent by an overnight air courier service  guaranteeing  next
day delivery.

                  Section 11.03 Further  Assurances.  Each of the parties hereto
agrees to take all  reasonably  necessary  steps to do all such further acts and
things as may be  necessary to carry out the  purposes  and  intentions  of this
Agreement and to ensure that the Venture can carry on its business  through LLCs
consistent with and as contemplated by this Agreement.


                                     - 63 -

<PAGE>



                  Section  11.04  Amendment.  This  Agreement  may  be  amended,
modified  and  supplemented  only by written  agreement  of Sonera U.S.  and the
Aerial Parties.

                  Section 11.05 Waiver of Compliance;  Consents.  Any failure by
the Aerial  Parties or Sonera  U.S.  to comply  with any  obligation,  covenant,
agreement  or condition  herein may be waived in writing by the other,  but such
waiver or  failure  to  insist  upon  strict  compliance  with such  obligation,
covenant,  agreement or condition  shall not operate as a waiver of, or estoppel
with  respect to, any  subsequent  or other  failure.  Whenever  this  Agreement
requires  or permits  waivers  or  consents  by or on behalf of any party,  such
waiver or consent shall be given in writing.

                  Section  11.06  Expenses.  Each party hereto shall pay its own
legal,  accounting  and  other  expenses  incident  to  this  Agreement  and the
consummation of the transactions contemplated thereby.

                  Section   11.07  Entire   Agreement.   This   Agreement,   the
Supplemental Agreement, the Purchase Agreement, the Investment Agreement and the
documents  referred  to  herein  and  therein  embody  the whole  agreement  and
understanding of the parties with respect to the relations  contemplated hereby.
There are no restrictions,  promises, representations,  warranties, covenants or
undertakings with respect thereto,  other than those set forth or referred to in
such   agreements.   Such   agreements   supersede  all  prior   agreements  and
understandings between the parties with respect to the subject matter hereof. No
rights in favor of third parties are hereby created.


                                     - 64 -

<PAGE>



                  Section 11.08 Counterparts.  This Agreement may be executed in
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.

                  Section 11.09 Headings and Captions. The headings and captions
contained in this Agreement are for reference purposes only and shall not affect
in any way the meaning or interpretation of this Agreement.

                  Section 11.10 Severability. In the event any provision of this
Agreement  is found to be  invalid  or  unenforceable  in whole or in part,  the
remaining  provisions of this  Agreement  nevertheless  shall be binding and the
invalid or unenforceable  provision shall be replaced by a valid and enforceable
provision  which comes closest to the intent or economic effect of the provision
to be replaced.

                  Section 11.11 Governing Law. This Agreement shall be construed
in  accordance  with and  subject  to the local,  internal  laws of the State of
Delaware.

                  Section 11.12 Compliance with FCC Rules.  (a)  Notwithstanding
any other  provision in this  Agreement,  the parties  hereto shall at all times
comply  with,  and all  provisions  of this  Agreement  shall be subject to, all
applicable  rules and  regulations  of the FCC,  including  but not  limited  to
approval  by the FCC prior to the  acquisition  of any B-PCS  License and to the
restrictions

                                     - 65 -

<PAGE>



on  spectrum  aggregation  set forth in Section  20.6 of the FCC rules,  and the
parties hereto shall  cooperate in the  preparation  and filing of all necessary
applications with the FCC.

                  (b) To the extent  that (i) any party  hereto or an  Affiliate
thereof,  jointly pursuant to this Agreement or  individually,  desires to enter
into a binding  agreement  to  acquire a  license  issued by the FCC to  provide
Wireless  Services or to manage or operate a system providing  Wireless Services
and (ii) such acquisition, operation or management would be prevented due to the
restrictions on spectrum aggregation set forth in Section 20.6 of the FCC rules,
then  the  parties  shall,  for a  period  of not less  than 15  business  days,
cooperate in good faith to consider, but (except as set forth in Section 8.01(c)
hereof)  shall not be  obligated  to take,  such action as may be  necessary  to
render  the  restrictions  of Section  20.6  inapplicable  to such  acquisition,
operation or management.

                  (c) Upon the request of any party hereto,  the parties  hereto
agree  to  reasonably  cooperate  in  seeking  a  waiver  from  the  FCC  of the
application  of Section 20.6 of the FCC rules to the  acquisition  by any Person
(other  than by a Person  who,  as a  result  of such  acquisition,  will be the
Majority Class A Member or the Majority Class B Member) of an equity interest in
an LLC formed  pursuant to Section 2.02 hereof equal to or greater than 20%. All
expenses  incurred in connection  with the  preparation and filing of such waver
application shall be the  responsibility of the party proposing that such waiver
be obtained. The pendency of such waiver request shall not restrict or otherwise
delay any party from taking any action  permitted by, or  exercising  any rights
set forth in, this Agreement or the related Limited Liability Company Agreement.
If such  waiver  is  granted  by the FCC,  then  such  acquisition  of an equity
interest equal to or greater than 20% shall

                                     - 66 -

<PAGE>



not be deemed a violation  of Section  4.06 hereof or Sections  3.4 or 6.2(f) of
the Limited Liability Company Agreement.

                  (d) In the  event  that  the  FCC,  pursuant  to a  rulemaking
proceeding,  adopts rules, which have become final and non-appealable,  amending
the  restrictions  on spectrum  aggregation set forth in Section 20.6 of the FCC
rules,  then the  parties  hereto  shall,  to the  extent  consistent  with such
amendment,  (i) amend  Sections  4.06 and 8.01(c)  hereof and  Sections  3.4 and
6.2(f) of the form of Limited Liability Company Agreement and (ii) in connection
with each LLC already formed  pursuant to Section 2.02 hereof,  propose that the
related Limited Liability Company Agreement be similarly amended.

                  Section 11.13 No Claim of Immunity.  Sonera U.S.  agrees that,
to the extent that it or any of its property, its Affiliates, or property of its
Affiliates is or becomes entitled at any time to any immunity, on the grounds of
sovereignty or otherwise,  based upon its status as an agency or instrumentality
of government,  from any arbitration,  legal action,  suit or proceeding or from
setoff or counterclaim  relating to this Agreement from the  jurisdiction of any
arbitrator or competent court, from service of process, from attachment prior to
judgment,  from  attachment  in aid of execution of a judgment,  from  execution
pursuant to a judgment or arbitration  award, or from any other legal process in
any jurisdiction,  it, for itself, its Affiliates,  its property and that of its
Affiliates,  expressly,  irrevocably and unconditionally  agrees not to plead or
claim,  any such immunity  with respect to such matters  arising with respect to
this  Agreement or the subject  matter hereof  (including any obligation for the
payment of money).

                                     - 67 -

<PAGE>



                  Section 11.14 Successors and Assigns.  This Agreement shall be
binding  upon and  inure  to the  benefit  of the  parties  hereto  and to their
respective permitted successors and assigns; provided, however, that neither the
rights nor the obligations of any party may be assigned or delegated without the
prior written consent of the other parties.

                  Section 11.15  Equitable  Remedies.  The parties  hereto agree
that  irreparable  damage would occur in the event that any of the provisions of
this Agreement  were not performed in accordance  with the specific terms hereof
or the provisions hereof were otherwise breached.  It is accordingly agreed that
the  parties  shall be  entitled  to an  injunction  or  injunctions  to prevent
breaches of this Agreement and to enforce  specifically the terms and provisions
hereof in any court of the United States or any state having jurisdiction,  this
being in  addition to any other  remedy to which they are  entitled at law or in
equity.  Each party agrees that it will not assert, as a defense against a claim
for specific  performance,  that the party seeking  specific  performance has an
adequate remedy at law.

                  Section  11.16  Remedies   Cumulative.   Except  as  otherwise
provided  herein,  each and all of the rights  and  remedies  in this  Agreement
provided,  and each and all of the  rights  and  remedies  allowed at law and in
equity in like  case,  shall be  cumulative,  and the  exercise  of one right or
remedy  shall not be exclusive of the right to exercise or resort to any and all
other rights or remedies provided in this Agreement or at law or in equity.


                                     - 68 -

<PAGE>



                  Section  11.17  Limitation  on  Damages.  Neither  the  Aerial
Parties  nor  Sonera  U.S.  shall be liable to the other for  damages  hereunder
except for reasonable direct economic and pecuniary costs (including  reasonable
attorneys' fees) and damages (which shall not include consequential,  exemplary,
expectancy,  indirect,  punitive  or  special  damages)  arising  out  of  or in
connection with any act or failure to act under, or breach of the terms of, this
Agreement.
                                    * * * * *










                                     - 69 -

<PAGE>



                  IN WITNESS  WHEREOF,  the parties  hereto have  executed  this
Agreement as of the date first written above.

AERIAL COMMUNICATIONS, INC.


By:      /s/ Donald W. Warkentin
         -------------------------------------
         Donald W. Warkentin
         President and Chief Executive Officer


AERIAL OPERATING CO., INC.


By:      /s/ Donald W. Warkentin
         -------------------------------------
         Donald W. Warkentin
         President and Chief Executive Officer


SONERA CORPORATION U.S.


By:      /s/ Kaj-Erik Relander
         -------------------------------------
Name:    Kaj-Erik Relander
         -------------------------------------  
Title:   President
         -------------------------------------





                   SIGNATURE PAGE TO JOINT VENTURE AGREEMENT,
                         DATED AS OF SEPTEMBER 8, 1998,
               AMONG AERIAL COMMUNICATIONS, INC., AERIAL OPERATING
                      CO., INC. AND SONERA CORPORATION U.S.



                                     - 70 -

<PAGE>



                                                                    EXHIBIT 99.5

                                                                  EXECUTION COPY












                             SUPPLEMENTAL AGREEMENT


                                  By and Among


                           AERIAL COMMUNICATIONS, INC.


                           AERIAL OPERATING CO., INC.


                                       and


                                   SONERA LTD.




                          Dated as of September 8, 1998







<PAGE>



                                TABLE OF CONTENTS
                                -----------------
                                                                            Page
                                                                            ----
ARTICLE I         DEFINITIONS

         Section 1.01  Defined Terms..........................................2
                       -------------

ARTICLE II        COVENANTS

         Section 2.01  Performance of Joint Venture Agreement.................2
                       --------------------------------------
         Section 2.02  Restriction on B-PCS Participation.....................3
                       ----------------------------------
         Section 2.03  References to Joint Venture Agreement..................3
                       -------------------------------------

ARTICLE III       TERMINATION

         Section 3.01  Termination............................................3
                       -----------

ARTICLE IV        DISPUTES

         Section 4.01  General................................................4
                       -------
         Section 4.02  Negotiation Procedure..................................4
                       ---------------------
         Section 4.03  Unresolved Disputes....................................6
                       -------------------
         Section 4.04  Jurisdiction; Consent to Service of Process............6
                       -------------------------------------------

ARTICLE V         REPRESENTATIONS AND WARRANTIES

         Section 5.01  Organization and Standing..............................7
                       -------------------------
         Section 5.02  Authorization..........................................8
                       -------------
         Section 5.03  Litigation.............................................8
                       ----------
         Section 5.04  Absence of Conflict....................................8
                       -------------------
         Section 5.05  Absence of Undisclosed Liabilities.....................9
                       ----------------------------------

ARTICLE VI        MISCELLANEOUS

         Section 6.01  Confidentiality........................................9
                       ---------------
         Section 6.02  Notices...............................................10
                       -------
         Section 6.03  Further Assurances....................................12
                       ------------------
         Section 6.04  Amendment.............................................12
                       ---------
         Section 6.05  Waiver of Compliance; Consents........................12
                       ------------------------------
         Section 6.06  Expenses..............................................13
                       --------
         Section 6.07  Entire Agreement......................................13
                       ----------------
         Section 6.08  Counterparts..........................................13
                       ------------
         Section 6.09  Headings and Captions.................................14
                       ---------------------

                                      - i -

<PAGE>



         Section 6.10  Severability..........................................14
                       ------------
         Section 6.11  Governing Law.........................................14
                       -------------
         Section 6.12  Compliance with FCC Rules.............................14
                       -------------------------
         Section 6.13  No Claim of Immunity..................................15
                       --------------------
         Section 6.14  Successors and Assigns................................15
                       ----------------------
         Section 6.15  Equitable Remedies....................................16
                       ------------------
         Section 6.16  Remedies Cumulative...................................16
                       -------------------
         Section 6.17  Limitation on Damages.................................16
                       ---------------------


SCHEDULES
- ---------

           4.02(c)    --     Designated Employees, Representatives and Officers




                                     - ii -

<PAGE>



                             SUPPLEMENTAL AGREEMENT


                  This  SUPPLEMENTAL  AGREEMENT,  dated as of  September 8, 1998
(the  "Agreement"),  is entered  into  between  AERIAL  COMMUNICATIONS,  INC., a
Delaware  corporation  ("Aerial"),   AERIAL  OPERATING  CO.,  INC.,  a  Delaware
corporation  and  wholly-owned  subsidiary of Aerial  ("AOC" and,  together with
Aerial,  the "Aerial  Parties"),  and SONERA LTD., a limited  liability  company
organized under the laws of the Republic of Finland and formerly known as Sonera
Corporation ("Sonera").

                              W I T N E S S E T H:

                  WHEREAS,  Aerial,  AOC and Sonera Corporation U.S., a Delaware
corporation and wholly-owned  subsidiary of Sonera ("Sonera U.S." and,  together
with Sonera, the "Sonera Parties"), have entered into a Joint Venture Agreement,
dated as of the date hereof (the "Joint Venture  Agreement"),  pursuant to which
Aerial,  AOC and Sonera U.S. have formed a joint venture (the "Venture")  which,
subject to  certain  exceptions  as set forth  therein,  will  serve  during the
Exclusivity  Period (as defined therein) as the exclusive  vehicle through which
the Aerial  Parties and the Sonera Parties will (i) acquire  licenses  issued by
the Federal Communications Commission to provide B- PCS (as defined therein) and
(ii) build and operate  systems  with  respect to such  licenses  utilizing  GSM
Technology (as defined therein);

                  WHEREAS,  the  Joint  Venture  Agreement  sets  forth  certain
obligations,  restrictions and prohibitions applicable to the Sonera Parties and
their affiliates with respect to the Venture; and



<PAGE>



                  WHEREAS,  Sonera,  as the corporate  parent of Sonera U.S., in
consideration  of the execution and delivery by the Aerial  Parties of the Joint
Venture Agreement,  desires to affirm to the Aerial Parties Sonera's  acceptance
of the  provisions  of the Joint  Venture  Agreement  and to set  forth  certain
covenants in this Agreement with respect thereto;

                  NOW,  THEREFORE,  in  consideration  of the  premises  and the
mutual  covenants,  conditions and promises  hereinafter set forth,  the parties
hereby agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

                  Section 1.01 Defined  Terms.  Capitalized  terms not otherwise
defined in this Agreement shall have the meanings set forth in the Joint Venture
Agreement.

                                   ARTICLE II
                                    COVENANTS

                  Section 2.01  Performance of Joint Venture  Agreement.  Sonera
hereby  covenants  to the Aerial  Parties  that  Sonera  shall not  directly  or
indirectly  (i) take,  or cause or permit Sonera U.S. or any Affiliate of either
Sonera  Party to take,  any action that Sonera U.S. or any  Affiliate  of either
Sonera Party is prohibited from taking  pursuant to the Joint Venture  Agreement
or (ii) cause

                                      - 2 -

<PAGE>



or permit Sonera U.S. or any Affiliate of either Sonera Party to fail to perform
any  obligation of Sonera U.S. or any Affiliate of either Sonera Party under the
Joint Venture Agreement.

                  Section  2.02  Restriction  on  B-PCS  Participation.   Sonera
expressly agrees to restrict its ability to participate, directly or indirectly,
by itself or through  any  Affiliate  or other  Sonera  Entity,  in B-PCS in the
United States except as expressly permitted by the Joint Venture Agreement or as
otherwise agreed in writing by the Aerial Parties.

                  Section 2.03  References  to Joint Venture  Agreement.  Sonera
further  expressly  acknowledges  and agrees that all  references  to the "Joint
Venture  Agreement"  set  forth  in  the  Purchase  Agreement,   the  Investment
Agreement,  the Limited Liability Company Agreement,  the Management  Agreement,
any agreement or instrument  referenced in, or attached as an exhibit to, any of
the  foregoing  agreements  and  any  certificate  or  instrument  delivered  in
connection  with the closing of the Purchase  Agreement on the date hereof shall
be deemed to include this Agreement.

                                   ARTICLE III
                                   TERMINATION

                  Section 3.01  Termination.  This Agreement shall commence upon
the date hereof and shall  remain in full force and effect at all times that the
Joint Venture Agreement  remains in effect.  This Agreement shall terminate only
upon termination of the Joint Venture Agreement.

                                      - 3 -

<PAGE>




                                   ARTICLE IV
                                    DISPUTES

                  Section   4.01   General.   The   parties   agree  to  address
disagreements  and disputes  arising out of or related to this  Agreement or the
breach hereof through the procedures set forth in this Article IV.

                  Section 4.02 Negotiation Procedure. (a) The Aerial Parties, on
the one  hand,  and  Sonera,  on the other  hand,  shall  designate  one or more
employees  or  representatives  who will be the initial  contact  for  resolving
disputes  that may arise under this  Agreement  that do not involve an amount in
excess of $50,000. The Aerial Parties and Sonera shall first raise such disputes
with a designated  employee or representative of the other party. The designated
employees or  representatives  shall work together to resolve the relevant issue
in a manner that meets the interests of both the Aerial  Parties and Sonera,  or
until the issue is referred to  designated  officers of the parties as set forth
in Section  4.02(b).  Any  disputes  that involve an amount in excess of $50,000
shall be  referred  to the  designated  officers  of the parties as set forth in
Section 4.02(b).

                  (b) The Aerial  Parties and Sonera shall also designate one or
more  officers who will review (i) disputes  that involve an amount in excess of
$50,000 or (ii) disputes that the designated  employees or  representatives  are
unable to resolve pursuant to Section  4.02(a).  Any matter not resolved by such
designated employees within 30 days after the date on which a party hereto first

                                      - 4 -

<PAGE>



notifies a  designated  employee  of the other  party  shall be referred to such
designated officers for resolution.  The designated officers shall work together
to resolve the disputes so referred to them in a manner that meets the interests
of both the Aerial  Parties and Sonera,  either until such agreement is reached,
or until an  impasse  is  declared  by either  the  Aerial  Parties  or  Sonera;
provided,  however,  that an impasse  shall not be declared by either the Aerial
Parties or Sonera prior to the  fifteenth  day after such dispute has first been
referred to such designated officers. Notice of declaration of any impasse shall
be given pursuant to Section 6.02 hereof.

                  (c) The employees or  representatives  and officers  initially
designated  by the Aerial  Parties and Sonera for  purposes of this Section 4.02
are set forth in  Schedule  4.02(c) to this  Agreement.  Parties may change such
designation by giving notice of such change pursuant to Section 6.02 hereof.

                  (d) Any resolution of a dispute by the designated employees or
representatives pursuant to Section 4.02(a) hereof or by the designated officers
pursuant to Section 4.02(b) hereof shall be in writing signed by such persons on
behalf of the  parties.  Notwithstanding  any  provision  of this Article IX, no
resolution of any dispute by any designated employee,  representative or officer
shall  constitute  an  amendment of this  Agreement  without the approval of the
respective boards of directors of each party hereto.


                                      - 5 -

<PAGE>



                  Section  4.03  Unresolved  Disputes.   The  parties  shall  be
entitled to exercise  or resort to any and all rights and  remedies  provided in
this  Agreement or at law or in equity with respect to any  controversy or claim
not resolved through the procedures set forth above.

                  Section 4.04 Jurisdiction;  Consent to Service of Process. (a)
Subject to and in  furtherance  of the  provisions of Section  4.03,  each party
hereby irrevocably consents and submits to the jurisdiction of the United States
District  Court  for the  District  of  Delaware  and any  court of the State of
Delaware in any action,  suit or proceeding  arising out of,  resulting  from or
relating to this Agreement,  and agrees that any such action, suit or proceeding
shall be brought  only in such courts (and waives any  objection  based on forum
non conveniens or any other objection to venue therein); provided, however, that
such  consent to  jurisdiction  is solely for the  purpose  referred  to in this
Section  4.04  and  shall  not  be  deemed  to be a  general  submission  to the
jurisdiction  of said  courts  or the  State  of  Delaware  other  than for such
purpose.

                  (b) Sonera hereby  irrevocably  appoints The Corporation Trust
Company,  at its office at 1209  Orange  Street,  Wilmington,  Delaware,  United
States of  America,  its lawful  agent and  attorney  to accept and  acknowledge
service of any and all  process  against it in any  action,  suit or  proceeding
arising out of, resulting from or relating to this Agreement, and upon whom such
process  may be served,  with the same  effect as if it were a  resident  of the
State of  Delaware,  and had been  lawfully  served  with such  process  in such
jurisdiction,  and waives all claim of error by reason of such service, provided
that in the case of any service upon such agent and attorney, the Aerial Parties
shall also  deliver a copy  thereof to Sonera at the  address  and in the manner
specified in Section 6.02.

                                      - 6 -

<PAGE>



In the event that such agent and attorney resigns or otherwise becomes incapable
of  acting as such,  Sonera  will  appoint a  successor  agent and  attorney  in
Wilmington,  Delaware,  reasonably satisfactory to the Aerial Parties, with like
powers or, if Sonera fails to make such  appointment,  Sonera hereby  authorizes
either  Aerial Party to appoint such agent.  Sonera shall pay the annual fee due
to The  Corporation  Trust  Company or such  successor  agent for acting in such
capacity; provided, however, that if Sonera fails to make such payment, then the
Aerial Parties shall be permitted to do so.

                                    ARTICLE V
                         REPRESENTATIONS AND WARRANTIES

                  Each party hereby  represents  and warrants to the other party
as follows (each party making said  representations  and warranties as to itself
and as to and on behalf of each of its Affiliates which is a party to any or all
of the  agreements  and  instruments  which are being  executed and delivered in
connection herewith):

                  Section 5.01  Organization and Standing.  It is a corporation,
in the case of each Aerial Party, or a limited liability company, in the case of
Sonera, duly organized,  validly existing and in good standing under the laws of
the jurisdiction of its organization,  has all requisite  authority and power to
carry on its business as now being  conducted by it, and is in good  standing in
each  jurisdiction in which the nature of the business  conducted by it requires
it to be qualified therein to do business.


                                      - 7 -

<PAGE>



                  Section 5.02 Authorization.  It has taken all action necessary
for  the  authorization,  execution,  delivery  and  performance  by it of  this
Agreement and the other  agreements being delivered  simultaneously  herewith to
which it is a party,  and when this Agreement and other  agreements are executed
and delivered by it, they will  constitute its valid and binding  obligations in
accordance with their respective terms. It has all necessary corporate and other
power with respect to the foregoing.

                  Section 5.03 Litigation.  It is not a party to any pending or,
to the best of its knowledge  threatened,  litigation or other proceeding which,
if adversely  determined,  would have a material adverse effect upon the Venture
or any LLC formed pursuant to the Joint Venture Agreement or such LLC's tangible
or intangible assets or operations.

                  Section  5.04  Absence of  Conflict.  Neither  the  execution,
delivery or performance by it of this Agreement or of any other agreements which
are being executed and delivered simultaneously herewith to which it is a party,
nor the consummation of the transactions herein or therein contemplated, nor the
fulfillment of or compliance  with the terms and  conditions  hereof or thereof,
will (nor with the  giving  of notice or lapse of time or both  would)  conflict
with its charter,  bylaws or other instrument pursuant to which it is organized,
or result in a breach of or  constitute  a default  under or  conflict  with any
material contract, agreement or instrument to which it is a party or by which it
or any of its properties are bound,  or any law, rule, or regulation  applicable
to it or any of its properties.  Any third party, governmental or administrative
consents or approvals  which are required in connection  with the foregoing have
been obtained and are in full force and effect.

                                      - 8 -

<PAGE>



                  Section 5.05  Absence of  Undisclosed  Liabilities.  It has no
material  debts,  liabilities,   contracts  or  other  obligations  which  could
reasonably  be expected to affect the Venture or any LLC formed  pursuant to the
Joint Venture Agreement in a materially adverse manner.

                                   ARTICLE VI
                                  MISCELLANEOUS

                  Section   6.01   Confidentiality.   (a)  In  addition  to  any
obligations of  confidentiality  pursuant to other  agreements  already existing
between the parties hereto (which this Section 6.01 is not intended to supersede
with respect to information disclosed prior to the execution of this Agreement),
each party hereto will, and will cause its Affiliates to, hold in confidence and
not disclose to any of its own  personnel or  personnel  of its  Affiliates  not
having a need to know or to any third party without the prior written consent of
the other  parties  hereto:  (i) any  information  received by it from the other
parties in  connection  with the  transactions  contemplated  hereby or (ii) any
specific terms of this Agreement or any agreement being delivered simultaneously
herewith.

                  (b) The foregoing  obligation  of confidence  shall extend for
the term of this Agreement and any extensions hereof and for a period of 5 years
thereafter;  provided,  however, that no party shall be obligated to maintain in
confidence information:

                  (i) which is or becomes  part of the public  domain other than
         through  breach of this Agreement or through the fault of the receiving
         party;

                                      - 9 -

<PAGE>



                  (ii) which is or becomes available to the receiving party from
         a  source  other  than  the  disclosing  party,  which  source  has  no
         obligation to the disclosing party in respect thereof;

                  (iii)  which  is made  available  by the  disclosing  party in
         written  form  to a  third  party  which  is  not an  Affiliate  of the
         disclosing party on an unrestricted basis;

                  (iv)  which is required to be disclosed by law; or

                  (v) disclosure of which is mutually agreed to by the parties.

                  (c) If any party hereto  discloses such information to a third
party, such disclosing party shall ensure that suitable  undertakings of secrecy
are imposed upon such third party which are no less stringent than those of this
Section 6.01.

                  Section  6.02   Notices.   All   notices,   claims  and  other
communications hereunder shall be in writing and shall be made by hand delivery,
facsimile, or overnight air courier guaranteeing next day delivery, as follows:


                                     - 10 -

<PAGE>



                  (a)  If to the Aerial Parties, at:

                           Aerial Communications, Inc.
                           8410 West Bryn Mawr Avenue
                           Suite 1100
                           Chicago, Illinois  60631
                           Attention:  Donald W. Warkentin
                           Telephone:  (773) 399-4145
                           Facsimile:  (773) 399-7997

                  with a copy (which shall not constitute notice) to:

                           Telephone and Data Systems, Inc.
                           30 North LaSalle Street
                           Suite 4000
                           Chicago, Illinois  60602
                           Attention:  LeRoy T. Carlson, Jr.
                           Telephone:  (312) 630-1900
                           Facsimile:  (312) 630-9299

                  and a copy (which shall not constitute notice) to:

                           Sidley & Austin
                           One First National Plaza
                           42nd Floor - SW
                           Chicago, Illinois  60603
                           Attention:  Michael G. Hron, Esq.
                           Telephone:  (312) 853-2030
                           Facsimile:  (312) 853-7036

                  (b)  if to Sonera, at:

                           Sonera Ltd.
                           P.O. Box 106
                           FIN-00051-TELE
                           Teollisuuskatu 15, Helsinki
                           Attention: Maire Laitinen, Esq.
                           Telephone:  011-35-8-2040-3641
                           Facsimile:  011-35-8-2040-3414


                                     - 11 -

<PAGE>



                  with a copy (which shall not constitute notice) to:

                           Patton Boggs, L.L.P.
                           2550 M. Street, N.W.
                           Washington, D.C.  20037-1350
                           Attention:  Richard M. Stolbach, Esq.
                           Telephone:  (202) 457-6324
                           Facsimile:  (202) 457-6315


or at such other address as any party may from time to time furnish to the other
parties by a notice  given in  accordance  with the  provisions  of this Section
6.02.  All such  notices  and  communications  shall be deemed to have been duly
given at the time  delivered  by hand,  if  personally  delivered;  when receipt
confirmed, if sent by facsimile; and the next Business Day after timely delivery
to the courier,  if sent by an overnight air courier service  guaranteeing  next
day delivery.

                  Section 6.03 Further  Assurances.  Each of the parties  hereto
agrees to take all  reasonably  necessary  steps to do all such further acts and
things as may be  necessary to carry out the  purposes  and  intentions  of this
Agreement and to ensure that the Venture can carry on its business  through LLCs
consistent with and as contemplated by the Joint Venture Agreement.

                  Section  6.04  Amendment.   This  Agreement  may  be  amended,
modified  and  supplemented  only by written  agreement of Sonera and the Aerial
Parties.

                  Section 6.05 Waiver of  Compliance;  Consents.  Any failure by
the Aerial Parties or Sonera to comply with any obligation,  covenant, agreement
or  condition  herein may be waived in writing by the other,  but such waiver or
failure to insist upon strict compliance with such obligation,

                                     - 12 -

<PAGE>



covenant,  agreement or condition  shall not operate as a waiver of, or estoppel
with  respect to, any  subsequent  or other  failure.  Whenever  this  Agreement
requires  or permits  waivers  or  consents  by or on behalf of any party,  such
waiver or consent shall be given in writing.

                  Section  6.06  Expenses.  Each party  hereto shall pay its own
legal,  accounting  and  other  expenses  incident  to  this  Agreement  and the
consummation of the transactions contemplated thereby.

                  Section  6.07  Entire  Agreement.  This  Agreement,  the Joint
Venture  Agreement,  the Purchase  Agreement,  the Investment  Agreement and the
documents  referred  to  herein  and  therein  embody  the whole  agreement  and
understanding of the parties with respect to the relations  contemplated hereby.
There are no restrictions,  promises, representations,  warranties, covenants or
undertakings with respect thereto,  other than those set forth or referred to in
such   agreements.   Such   agreements   supersede  all  prior   agreements  and
understandings between the parties with respect to the subject matter hereof. No
rights in favor of third parties are hereby created.

                  Section 6.08  Counterparts.  This Agreement may be executed in
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.


                                     - 13 -

<PAGE>



                  Section 6.09 Headings and Captions.  The headings and captions
contained in this Agreement are for reference purposes only and shall not affect
in any way the meaning or interpretation of this Agreement.

                  Section 6.10 Severability.  In the event any provision of this
Agreement  is found to be  invalid  or  unenforceable  in whole or in part,  the
remaining  provisions of this  Agreement  nevertheless  shall be binding and the
invalid or unenforceable  provision shall be replaced by a valid and enforceable
provision  which comes closest to the intent or economic effect of the provision
to be replaced.

                  Section 6.11 Governing Law. This Agreement  shall be construed
in  accordance  with and  subject  to the local,  internal  laws of the State of
Delaware.

                  Section 6.12  Compliance with FCC Rules.  Notwithstanding  any
other provision in this Agreement,  the parties hereto shall at all times comply
with, and all  provisions of this Agreement  shall be subject to, all applicable
rules and  regulations of the FCC,  including but not limited to approval by the
FCC prior to the  acquisition  of any B-PCS License and to the  restrictions  on
spectrum aggregation set forth in Section 20.6 of the FCC rules, and the parties
hereto  shall   cooperate  in  the  preparation  and  filing  of  all  necessary
applications  with the  FCC.  To the  extent  that (i) any  party  hereto  or an
Affiliate   thereof,   jointly  pursuant  to  the  Joint  Venture  Agreement  or
individually,  desires  to enter into a binding  agreement  to acquire a license
issued by the FCC to provide Wireless  Services or to manage or operate a system
providing Wireless Services and (ii)

                                     - 14 -

<PAGE>



such  acquisition,  operation  or  management  would  be  prevented  due  to the
restrictions on spectrum aggregation set forth in Section 20.6 of the FCC rules,
then  the  parties  shall,  for a  period  of not less  than 15  business  days,
cooperate in good faith to consider, but (except as set forth in Section 8.01 of
the Joint Venture  Agreement) shall not be obligated to take, such action as may
be necessary to render the  restrictions  of Section 20.6  inapplicable  to such
acquisition, operation or management.

                  Section 6.13 No Claim of Immunity.  Sonera agrees that, to the
extent  that it or any of its  property,  its  Affiliates,  or  property  of its
Affiliates is or becomes entitled at any time to any immunity, on the grounds of
sovereignty or otherwise,  based upon its status as an agency or instrumentality
of government,  from any arbitration,  legal action,  suit or proceeding or from
setoff or counterclaim  relating to this Agreement from the  jurisdiction of any
arbitrator or competent court, from service of process, from attachment prior to
judgment,  from  attachment  in aid of execution of a judgment,  from  execution
pursuant to a judgment or arbitration  award, or from any other legal process in
any jurisdiction,  it, for itself, its Affiliates,  its property and that of its
Affiliates,  expressly,  irrevocably and unconditionally  agrees not to plead or
claim,  any such immunity  with respect to such matters  arising with respect to
this  Agreement or the subject  matter hereof  (including any obligation for the
payment of money).

                  Section 6.14  Successors and Assigns.  This Agreement shall be
binding  upon and  inure  to the  benefit  of the  parties  hereto  and to their
respective permitted successors and assigns; provided, however, that neither the
rights nor the obligations of any party may be assigned or delegated without the
prior written consent of the other parties.

                                     - 15 -

<PAGE>



                  Section 6.15 Equitable Remedies. The parties hereto agree that
irreparable  damage would occur in the event that any of the  provisions of this
Agreement were not performed in accordance with the specific terms hereof or the
provisions  hereof were otherwise  breached.  It is accordingly  agreed that the
parties shall be entitled to an injunction or injunctions to prevent breaches of
this Agreement and to enforce  specifically  the terms and provisions  hereof in
any court of the United States or any state having  jurisdiction,  this being in
addition  to any other  remedy to which they are  entitled  at law or in equity.
Each party  agrees  that it will not  assert,  as a defense  against a claim for
specific  performance,  that  the  party  seeking  specific  performance  has an
adequate remedy at law.

                  Section 6.16 Remedies Cumulative. Except as otherwise provided
herein, each and all of the rights and remedies in this Agreement provided,  and
each and all of the  rights  and  remedies  allowed at law and in equity in like
case, shall be cumulative,  and the exercise of one right or remedy shall not be
exclusive  of the right to  exercise  or  resort to any and all other  rights or
remedies  provided in this  Agreement or at law or in equity.  Sonera  expressly
agrees that  neither  Aerial  Party shall be required to exercise  its rights or
remedies  under the Joint  Venture  Agreement  prior to  exercise by such Aerial
Party of any right or remedy provided in this Agreement.

                  Section 6.17 Limitation on Damages. Neither the Aerial Parties
nor  Sonera  shall be  liable  to the other for  damages  hereunder  except  for
reasonable direct economic and pecuniary costs (including  reasonable attorneys'
fees) and damages (which shall not include consequential,

                                     - 16 -

<PAGE>



exemplary,  expectancy, indirect, punitive or special damages) arising out of or
in connection  with any act or failure to act under,  or breach of the terms of,
this Agreement.
                                    * * * * *
                  IN WITNESS  WHEREOF,  the parties  hereto have  executed  this
Agreement as of the date first written above.

AERIAL COMMUNICATIONS, INC.


By:      /s/ Donald W. Warkentin
         ------------------------------------
         Donald W. Warkentin
         President and Chief Executive Officer


AERIAL OPERATING CO., INC.


By:      /s/ Donald W. Warkentin
         ------------------------------------
         Donald W. Warkentin
         President and Chief Executive Officer


SONERA LTD.


By:      /s/ Aulis Salin
         -----------------------------------
Name:    Aulis Salin
         -----------------------------------
Title:   President  and CEO
         -----------------------------------


                    SIGNATURE PAGE TO SUPPLEMENTAL AGREEMENT,
                         DATED AS OF SEPTEMBER 8, 1998,
               AMONG AERIAL COMMUNICATIONS, INC., AERIAL OPERATING
                            CO., INC. AND SONERA LTD.


                                     - 17 -

<PAGE>



                  

                                                                    EXHIBIT 99.6

                                                                  EXECUTION COPY


                            TAX ALLOCATION AGREEMENT


                  This Tax Allocation Agreement,  dated as of September 8, 1998,
is entered into between Telephone and Data Systems, Inc., a Delaware corporation
(herein  called  "TDS"),  Aerial  Communications  Inc.,  a Delaware  corporation
(herein called "Aerial"), and Aerial Operating Co., Inc., a Delaware corporation
(herein called "AOC").

                  WHEREAS,  for  federal  income  tax  purposes,  Aerial and its
Subsidiaries  join with TDS and other members of its Affiliated  Group in filing
consolidated federal income tax returns; and

                  WHEREAS, in connection with a contemplated  offering by AOC of
its Common  Shares,  TDS,  Aerial and AOC desire to enter into this Agreement in
order to (i) specify  certain rights and  obligations of the parties hereto with
respect to the filing of consolidated federal income tax returns and the payment
of federal  income tax for taxable  years  during  which Aerial or AOC remains a
member of the TDS Affiliated Group, (ii) provide for certain  reimbursements and
specify the manner in which  adjustments to the federal  income tax  liabilities
for  consolidated  return  years shall be  determined  and  settled  between the
parties hereto in the event that Aerial or AOC leaves the group, (iii) apply the
provisions regarding federal income tax liabilities to state franchise or income



<PAGE>



tax liabilities required to be determined on a unitary, combined or consolidated
basis,  and (iv) specify  certain  rights and  obligations of the parties hereto
with respect to state franchise or income tax liabilities  that are not required
to be so determined.

                  NOW,  THEREFORE,  in  consideration  of the mutual  agreements
herein contained, the parties hereto agree as follows:

                  Section 1.  Definitions.  For purposes of this Agreement,  the
following definitions shall apply:

                  "Affiliated  Group" means an "affiliated  group" as defined in
Section 1504(a) of the Code.

                  "Code" means the Internal Revenue Code of 1986, as amended and
in effect  from time to time,  and any law that may be a  successor  thereto.  A
reference  to any Section of the Code means such  Section as in effect from time
to time and any comparable provision of any prior or successor law.

                  "Consolidated   Return   Regulations"   means   the   Treasury
Regulations  promulgated  under Section 1502 of the Code, as in effect from time
to time.

                                       -2-

<PAGE>



                  "Consolidated  Return  Year"  means a taxable  year of the TDS
Affiliated  Group  during  any part of which  Aerial  or AOC is a member of such
group and joins in the filing of a  consolidated  federal  income tax return for
such group.

                  "Final  Determination"  means  the  first  to  occur  of (i) a
decision  by a court of  competent  jurisdiction  that is not subject to further
judicial  review  (by  appeal  or  otherwise)  and has  become  final;  (ii) the
expiration  of 30 days  after  IRS  acceptance  of a Waiver of  Restrictions  on
Assessment and Collection of Deficiency in Tax and Acceptance of  Overassessment
on  Internal  Revenue  Form 870 or 870-AD  (or any  successor  comparable  form)
unless,  within such 30-day period,  TDS gives notice to Aerial of its intention
to attempt to recover all or part of any amount paid  pursuant to such Waiver by
the filing of a timely claim for refund;  (iii) the  expiration  of the time for
filing a claim for  refund,  or for  instituting  suit in respect of a claim for
refund  disallowed  in whole or in part by the IRS;  (iv) the execution by or on
behalf of the taxpayer and the IRS of a closing  agreement under Section 7121 of
the Code; (v) the  acceptance by the IRS or its counsel of a tender  pursuant to
an offer in  compromise  under Section 7122 of the Code; or (vi) any other event
that the  parties  hereto  agree is a final  and  irrevocable  determination  of
liability for federal income tax for any taxable year.

                  "IRS" means the United States Internal  Revenue Service or any
successor thereto,  including,  but not limited to, its agents,  representatives
and attorneys.


                                       -3-

<PAGE>



                  "Separate Return Year" means any taxable year for which Aerial
and its Subsidiaries  file separate federal income tax returns or join in filing
a  consolidated  federal  income tax return  with an  Affiliated  Group of which
Aerial is the common parent.

                  "Subsidiaries"   means  AOC  and  those  direct  and  indirect
subsidiaries of Aerial that are members of the TDS Affiliated Group from time to
time.

                  "Tax  Attribute"  means  income,  gain,  loss,  deduction  and
credit, and all items entering into the computation  thereof, for federal income
tax purposes.

                  "TDS Affiliated Group" means the Affiliated Group of which TDS
is the common parent.

                  "Transition Date" means January 1, 1996.

                  "Treasury   Regulations"  means  the  income  tax  regulations
promulgated under the Code.

                  Section 2.  Continued Filing of Consolidated Returns.

                  (a)  Aerial and its  Subsidiaries  shall  continue  to join in
filing consolidated federal income tax returns with the TDS Affiliated Group for
such taxable years for which they are eligible

                                       -4-

<PAGE>



to do so under the Code and the Consolidated Return Regulations unless TDS shall
request  otherwise.  TDS shall  have the right to  exercise  all the powers of a
common  parent  with  respect to such  returns as are  conferred  upon it by the
Consolidated  Return  Regulations.   Without  limiting  the  generality  of  the
foregoing, TDS shall be the sole agent for Aerial and its Subsidiaries in any or
all matters  relating to the federal  income tax liability of the TDS Affiliated
Group for all Consolidated  Return Years. Aerial and its Subsidiaries shall have
no authority to act for or to  represent  itself in any such matter.  Aerial and
its  Subsidiaries  shall not,  without the consent of TDS,  (i)  terminate  such
agency or (ii) participate, or attempt to participate, in any matters related to
the  federal  income  tax  liability  of  the  TDS  Affiliated   Group  for  any
Consolidated Return Year,  including,  but not limited to, preparation or filing
of, or resolution of disputes with the IRS concerning the  consolidated  federal
income tax return for any  Consolidated  Return Year.  The decision of the chief
executive  officer or the chief financial  officer of TDS shall,  subject to the
provisions of this  Agreement,  be binding in any dispute between TDS and Aerial
and its Subsidiaries as to the tax position to be taken with respect to any item
or transaction  of Aerial and its  Subsidiaries  includable in the  consolidated
federal income tax return for any Consolidated Return Year.

                  (b)  Aerial  and its  Subsidiaries  shall  furnish to TDS in a
timely manner such  information and documents as TDS may request for the purpose
of preparing  tax returns or in  connection  with any  subsequent  audit of such
returns,  claim for refund, or administrative or judicial  proceeding  involving
such returns.


                                       -5-

<PAGE>



                  (c) The federal  income tax  liability  of the TDS  Affiliated
Group for the Consolidated  Return Year ended December 31, 1995, as shown on the
return filed for such year,  shall be shared by all the members of such Group in
accordance  with the method of  allocation  used for prior  Consolidated  Return
Years.  The federal  income tax liability of the TDS  Affiliated  Group for each
Consolidated  Return  Year ending  after the  Transition  Date,  as shown on the
return filed for each such year, shall be allocated as follows: Aerial shall pay
to TDS an amount equal to the greater of (i) the federal income tax liability of
Aerial  and  its  Subsidiaries  computed  as  if  they  constituted  a  separate
Affiliated  Group  filing a  consolidated  return  (including  any  minimum  tax
liability of such Group), or (ii) the federal income tax liability of Aerial and
its  Subsidiaries  computed as if they  constituted a separate  Affiliated Group
filing a  consolidated  return subject to tax at a rate equal to the quotient of
(A) the federal income tax liability,  before tax credits, of the TDS Affiliated
Group for the  Consolidated  Return  Year,  divided by (B) the  federal  taxable
income of the TDS Affiliated  Group for such year; and TDS shall pay the balance
of the  consolidated  tax  liability,  if any.  For  purposes  of the  preceding
sentence, Aerial and its Subsidiaries shall be treated as if they were formed as
an Affiliated  Group (with Aerial as the common  parent) on January 1, 1996, and
shall be entitled to carry forward (within the allowable statutory period) their
Affiliated  Group's net  operating or capital  losses or unused tax credits,  if
any, arising  thereafter to offset the subsequent  income and tax liability,  if
any, of such Group.

                  (d)  Aerial  and  its  Subsidiaries  shall  pay to  TDS  their
respective  shares of the consolidated tax liability of the TDS Affiliated Group
for each  Consolidated  Return Year,  as  determined  pursuant to paragraph  (c)
above, (less any amounts previously paid in respect of

                                       -6-

<PAGE>



estimated  taxes for such year) no later than  March 15 of the  following  year;
provided,  however,  that  for 1996 and each  subsequent  year,  Aerial  and its
Subsidiaries shall be required to pay to TDS at least 90% of TDS's best estimate
of their respective  shares of the consolidated tax liability to be shown on the
return for the Consolidated Return Year in question (less any amounts previously
paid in respect of estimated taxes for such year) no later than March 15 and any
balance due shall be paid by the following September 15; and provided,  further,
that for each  Consolidated  Return Year after 1995, Aerial shall pay to TDS, no
later than each due date for an estimated tax payment prescribed by Section 6154
of the Code, the minimum amount required to be paid to avoid the imposition of a
penalty  under  Section  6655 of the Code,  determined  on the same basis as the
share  of  Aerial  and its  Subsidiaries  in the  total  tax  liability  for the
Consolidated Return Year in question is determined under paragraph (c) above.

                  (e)  Pursuant to the tax sharing or  allocation  agreement  or
arrangement in effect  between the parties hereto prior to the date hereof,  TDS
shall be and remain  obligated to pay to Aerial an amount equal to the reduction
(net of any actual or anticipated  loss of any unused tax credits eligible to be
carried  forward) in the provision for federal  income taxes  reflected in TDS's
audited  consolidated  statements  of income for all  Consolidated  Return Years
through 1995 that resulted from the inclusion of Aerial and its  Subsidiaries in
the TDS Affiliated Group for such Consolidated Return Years.


                                       -7-

<PAGE>



                  Section 3.  Contests and Claims for Refund.

                  (a) If TDS receives from the IRS a written  notice of proposed
deficiency  (30-day  letter) that  involves  any Tax  Attribute of Aerial or its
Subsidiaries for any Consolidated  Return Year, TDS shall within 15 days provide
Aerial  with a copy of such  30-day  letter  (and  any  accompanying  forms  and
schedules)  and shall  notify  Aerial of any  action  TDS  intends  to take with
respect to such proposed  deficiency  and the amount of any proposed  additional
taxes that,  in the  opinion of TDS,  are the  responsibility  of Aerial and its
Subsidiaries  under this  Agreement.  If TDS shall deem it appropriate to make a
claim for  refund of income  tax (by  filing an  amended  return or  otherwise),
arising from a Tax Attribute of Aerial or its  Subsidiaries for any Consolidated
Return Year (including carrybacks of losses or credits from a later Consolidated
Return Year or a Separate Return Year), TDS shall so notify Aerial.

                  (b) TDS shall be permitted,  through its counsel or otherwise,
at Aerial's expense,  to contest any proposed  deficiency or prosecute any claim
for refund with respect to any  Consolidated  Return Year in  administrative  or
judicial  proceedings,  and  shall  have the  right to make any  decision  as to
settlement  of the  contest or claim or any issue  involved  therein,  choice of
forum for judicial proceedings and prosecution of appeals.  Aerial shall pay TDS
for any  liability,  expense or loss  arising  out of or  relating to the Aerial
issues  involved in the contest or claim  (including,  without  limitation,  all
out-of-pocket expenses, costs, losses, reasonable legal, accounting,  engineers'
and like professional fees, disbursements,  interest, penalties and additions to
tax relating to such  issues) as the same shall be incurred.  If such contest is
to be conducted in a manner requiring payment of a

                                       -8-

<PAGE>



proposed tax deficiency, Aerial shall advance to TDS, on an interest-free basis,
an amount  sufficient  to make  payment  of the  amount  attributable  to Aerial
issues, together with any required interest or penalties.

                  (c) If  there  is a Final  Determination  of a  deficiency  in
federal  income  tax for any  Consolidated  Return  Year,  the  portion  of such
deficiency,  if any, that is  attributable  to an adjustment to the reported Tax
Attributes  of  Aerial  or its  Subsidiaries,  and  any  interest  or  penalties
applicable thereto,  shall be paid by Aerial. Any such payments shall be made to
TDS upon notice to Aerial.  If a refund of federal income tax is received by TDS
for any  Consolidated  Return Year, the portion of such refund,  if any, that is
attributable  to an  adjustment  to the  previously  assessed Tax  Attributes of
Aerial or its Subsidiaries,  and any interest applicable thereto,  shall be paid
by TDS to Aerial. Any such payments shall be made by TDS promptly after any such
refund and interest are received by it.

                  Section 4. Reimbursements Subsequent to Affiliation. If Aerial
and its  Subsidiaries  or AOC and its  Subsidiaries do not remain members of the
TDS  Affiliated  Group,  TDS shall reimburse the  former TDS  Affiliated  Group
members for any amount of federal income tax which they are thereafter  required
to pay for a Separate  Return  Year under the Code and which they would not have
been  required to pay if they had not been members of the TDS  Affiliated  Group
after the Transition Date; provided,  however,  that no such reimbursement shall
be made to Aerial or any of its  Subsidiaries  if, at any time after TDS becomes
the owner of Series A Common Shares, par value $1.00 per share, of Aerial,  less
than 500,000 Series A Common Shares are outstanding, and no such

                                       -9-

<PAGE>



reimbursement shall be made to any Subsidiary of Aerial if, after the Transition
Date, another person or group (other than a person or group owning capital stock
of TDS  having  more  than 50% of the  total  voting  power in the  election  of
directors of all shares of TDS's capital stock outstanding at the time) acquires
(i) capital  stock of such  Subsidiary  having more than 50% of the total voting
power in the election of directors  of all shares of such  Subsidiary's  capital
stock outstanding at the time or (ii) assets of such Subsidiary  representing in
the aggregate more than 50% of the total value of the assets of such  Subsidiary
as reflected on the most recent  balance  sheet of such  Subsidiary  prepared in
accordance with generally accepted accounting  principles in effect at the time.
As used in this  Section  4, the  term  "person"  means  any  individual,  firm,
corporation,  partnership, trust or other entity; and "group" means any group of
persons  formed for the purpose of  acquiring,  holding,  voting or disposing of
capital stock of Aerial or any Subsidiary  (or TDS).  Thus, any net operating or
capital  losses or tax  credits of Aerial and its  Subsidiaries,  computed as if
such  corporations  constituted a separate  Affiliated Group with Aerial (if the
event  triggering  the  application of this Section 4 is the departure of Aerial
and its Subsidiaries from the TDS Affiliated Group) or AOC (if such event is the
departure of AOC and its  Subsidiaries)  as the common parent,  that arise after
December 31, 1995, and are not used to offset the separate tax liability of such
Group in  subsequent  Consolidated  Return  Years shall be treated as  available
carryovers to Separate  Return Years (within the allowable  statutory  carryover
period).  For the purpose of  determining  the amount of  reimbursement:  (i) it
shall be assumed that Aerial and its Subsidiaries (or AOC and its  Subsidiaries)
would  have  filed  consolidated  federal  income tax  returns  for all  periods
commencing on January 1, 1996, and ending before the first Separate Return Year,
with the same Tax Attributes as were reported in the corresponding  consolidated
returns of the TDS Affiliated Group (without regard to any adjustments

                                      -10-

<PAGE>



to such Tax Attributes  reflected in any deficiency in tax or refund of tax paid
by or to Aerial  pursuant to Section 3(c) of this  Agreement);  and (ii) any Tax
Attributes of Aerial (or AOC) in Separate  Return Years,  or of other members of
the Aerial Affiliated Group (or the AOC Affiliated Group) joining in the returns
for such years, arising from sources other than the business activities in which
Aerial and its  Subsidiaries (or AOC and its  Subsidiaries)  were engaged on the
first  day  of the  first  Separate  Return  Year  shall  be  disregarded.  Such
reimbursement shall be made, on an interest-free basis, within 15 days after TDS
receives a copy of the tax return or of a Final  Determination  of tax liability
for the Separate Return Year in question and a claim for reimbursement, together
with sufficient  information  and/or  documentation  to permit TDS to verify the
accuracy of such claim.

                  Section  5.  Action  by  and  Payments  to  Subsidiaries.  Any
provision of this  Agreement that requires the  Subsidiaries  to take or refrain
from taking  action  shall be  construed  to include a  requirement  either that
Aerial cause its Subsidiaries to take or refrain from taking such action or that
Aerial take such action on behalf of its  Subsidiaries.  Any  provision  of this
Agreement  that  requires  TDS to make a payment  to the  Subsidiaries  shall be
satisfied  by a payment to Aerial on behalf of the  Subsidiaries,  except to the
extent  TDS is  required  to  make a  payment  to AOC  under  Section  4 of this
Agreement.

                  Section 6.  State Franchise or Income Tax Liabilities.

                  (a) To the extent appropriate, rules similar to the provisions
of Sections 2, 3, 4 and 5 of this Agreement shall be applied to the provision of
information and documents, the filing of

                                      -11-

<PAGE>



returns,  contests and claims for refund,  the allocation of and  reimbursements
with  respect  to state  franchise  or income tax  liabilities  to which TDS and
Aerial and its  Subsidiaries are subject and which are required to be determined
on a unitary, combined or consolidated basis.

                  (b) If any such state tax  liabilities  are not required to be
determined on a unitary, combined or consolidated basis, then TDS shall have the
option to act as the sole agent for Aerial and its  Subsidiaries  in any and all
matters  relating to such state tax  liabilities of Aerial and its  Subsidiaries
for all  Consolidated  Return Years. If TDS elects to exercise such option,  and
for so long as such agency continues, neither Aerial nor any of its Subsidiaries
shall have no authority  to act for or to  represent  itself in any such matter,
and neither  Aerial nor any of its  Subsidiaries  shall,  without the consent of
TDS, (i) terminate such agency or (ii)  participate,  or attempt to participate,
in matters related to such state  liabilities of Aerial and its Subsidiaries for
any  Consolidated  Return Year,  including,  but not limited to,  preparation or
filing of, or resolution of disputes with tax authorities concerning,  the state
franchise  or income tax returns  (including  returns  with respect to estimated
taxes) filed on behalf of Aerial for any  Consolidated  Return Year.  Aerial and
its  Subsidiaries  shall furnish to TDS in a timely manner such  information and
documents  as TDS may request for the purpose of  preparing  such  returns or in
connection with a subsequent audit of such returns by tax authorities or a claim
for refund or judicial proceeding  involving such returns.  Aerial shall execute
such returns at TDS's request,  and the decision of the chief executive  officer
or the chief financial  officer of TDS shall,  subject to the provisions of this
Agreement,  be  binding  in any  dispute  between  TDS and  Aerial as to the tax
position to be taken by Aerial in such  returns.  All taxes due with  respect to
such returns shall be the obligation of Aerial, and all refunds of such taxes

                                      -12-

<PAGE>



shall inure to the benefit of Aerial. TDS shall not have any obligation for such
taxes nor shall it be entitled to any refund for such taxes.

                  Section 7.  Additions to  Payments.  The amount of any payment
required  to be made by any party to another  under this  Agreement  shall be an
amount which, after subtraction of any additional federal,  state or local taxes
payable by the recipient in respect of the receipt of such payment,  is equal to
the amount payable hereunder.

                  Section 8. Election under Section 1552 of the Code. Nothing in
this Agreement is intended to change or otherwise affect any election made by or
on behalf  of the TDS  Affiliated  Group  with  respect  to the  calculation  of
earnings and profits under Section 1552 of the Code or the  Consolidated  Return
Regulations.

                  Section 9. Representations and Warranties. As an inducement to
enter into this Agreement,  each party  represents to and agrees with the others
that:

                  (a) it is a corporation  duly organized,  validly existing and
         in good standing under the laws of its state of  incorporation  and has
         all requisite corporate power to own, lease and operate its properties,
         to carry on its  business as presently  conducted  and to carry out the
         transactions contemplated by this Agreement;


                                      -13-

<PAGE>



                  (b) it  has  duly  and  validly  taken  all  corporate  action
         necessary to authorize the execution,  delivery and performance of this
         Agreement and the consummation of the transactions contemplated hereby;

                  (c) this  Agreement has been duly executed and delivered by it
         and constitutes its legal, valid and binding obligation  enforceable in
         accordance with its terms (subject,  as to the enforcement of remedies,
         to applicable  bankruptcy,  reorganization,  insolvency,  moratorium or
         other similar laws  affecting  the  enforcement  of  creditors'  rights
         generally  from  time to time  in  effect,  and  subject  to  equitable
         limitations on the availability of the remedy of specific performance);
         and

                  (d) none of the execution and delivery of this Agreement,  the
         consummation of the transactions  contemplated hereby or the compliance
         with any of the  provisions of this Agreement will (i) conflict with or
         result in a breach of any provision of its corporate charter or bylaws,
         (ii) breach,  violate or result in a default  under any of the terms of
         any agreement or other  instrument or obligation to which it is a party
         or by which it or any of its properties or assets may be bound or (iii)
         violate  any  order,  writ,  injunction,   decree,   statute,  rule  or
         regulation  applicable  to it or  affecting  any of its  properties  or
         assets.


                                      -14-

<PAGE>



                  Section 10. Term of  Agreement.  This  Agreement  shall become
effective as of the date of its  execution  and,  except as otherwise  expressly
provided herein, the respective  covenants of the parties contained herein shall
continue in full force and effect indefinitely.

                  Section 11. Prior Tax Sharing Agreements. This Agreement shall
supersede any other tax sharing or allocation agreement or arrangement in effect
between the parties  hereto prior to the date hereof with respect to the matters
expressly dealt with herein,  but any such prior agreement or arrangement  shall
otherwise remain in effect according to its terms.

                  Section 12.  Miscellaneous.

                  (a)  Injunctions.  The parties  acknowledge  that  irreparable
damage  would occur in the event that any of the  provisions  of this  Agreement
were not performed in accordance  with their  specific  terms or were  otherwise
breached.  Therefore,  the parties  hereto shall be entitled to an injunction or
injunctions  to prevent  breaches of the  provisions  of this  Agreement  and to
enforce  specifically  the terms  and  provisions  hereof  in any  court  having
jurisdiction,  such remedy  being in addition to any other  remedy to which they
may be entitled at law or equity.

                  (b)  Severability.   If  any  term,  provision,   covenant  or
restriction of this Agreement is held by a court of competent jurisdiction to be
invalid,  void  or  unenforceable,  the  remainder  of  the  terms,  provisions,
covenants  and  restrictions  set forth  herein  shall  remain in full force and
effect and shall in no way be affected,  impaired or  invalidated.  It is hereby
stipulated and declared to be

                                      -15-

<PAGE>



the intention of the parties that they would have executed the remaining  terms,
provisions,  covenants and restrictions  without including any of such which may
be hereafter declared invalid, void or unenforceable. In the event that any such
term,  provision,  covenant  or  restriction  is  held to be in  valid,  void or
unenforceable,  the  parties  hereto  shall use their  best  efforts to find and
employ an alternate means to achieve the same or  substantially  the same result
as that contemplated by such term, provision, covenant or restriction.

                  (c)  Assignment.  Except by operation of law or in  connection
with the sale or  transfer  of all or  substantially  all the  assets of a party
hereto  or of all or  substantially  all of the  capital  stock of Aerial or AOC
beneficially owned by TDS or Aerial,  respectively,  this Agreement shall not be
assignable,  in whole or in part,  directly or  indirectly,  by any party hereto
without the written  consent of the other  party,  and any attempt to assign any
rights or obligations arising under this Agreement without such consent shall be
void; provided,  however, that the provisions of this Agreement shall be binding
upon, inure to the benefit of and be enforceable by the parties hereto and their
respective successors and permitted assigns.

                  (d) Further Assurances.  Subject to the provisions hereof, the
parties  hereto  shall  make,  execute,   acknowledge  and  deliver  such  other
instruments and documents, and take all such other actions, as may be reasonably
required in order to effectuate the purposes of this Agreement and to consummate
the transactions  contemplated hereby. Subject to the provisions hereof, each of
the parties shall, in connection  with entering into this Agreement,  performing
its obligations hereunder and taking any and all actions relating hereto, comply
with all applicable laws,

                                      -16-

<PAGE>



regulations,  orders and decrees, obtain all required consents and approvals and
make all required  filings with any  governmental  agency,  other  regulatory or
administrative agency,  commission or similar authority and promptly provide the
other party with all such information as they may reasonably request in order to
be able to comply with the provisions of this sentence.

                  (e)   Parties  in   Interest.   Except  as  herein   otherwise
specifically  provided,  nothing  in this  Agreement  expressed  or  implied  is
intended  to confer any right or benefit  upon any person,  firm or  corporation
other than the parties and their respective successors and permitted assigns.

                  (f)  Waivers,  Etc.  No  failure  or  delay on the part of the
parties in  exercising  any power or right  hereunder  shall operate as a waiver
thereof, nor shall any single or partial exercise of any such right or power, or
any  abandonment  or  discontinuance  of steps to enforce such a right or power,
preclude  any other or further  exercise  thereof or the  exercise  of any other
right or power.  No amendment,  modification  or waiver of any provision of this
Agreement  nor consent to any  departure by the parties  therefrom  shall in any
event be  effective  unless the same shall be in writing and signed by the chief
executive  officer or the chief  financial  officer of each party in the case of
amendments  or  modifications,  or by the chief  executive  officer or the chief
financial  officer of the waiving or consenting  party,  and then such waiver or
consent shall be effective only in the specific instance and for the purpose for
which given.

                  (g)  Setoff.  All  payments to be made by any party under this
Agreement  shall be made without setoff,  counterclaim  or  withholding,  all of
which are expressly waived.

                                      -17-

<PAGE>



                  (h) Changes of Law. If, due to any change in applicable law or
regulations or the interpretation thereof by any court of law or other governing
body having jurisdiction  subsequent to the date of this Agreement,  performance
of any provision of this Agreement or any transaction contemplated thereby shall
become  impracticable  or  impossible,  the parties  hereto shall use their best
efforts  to find  and  employ  an  alternative  means  to  achieve  the  same or
substantially the same result as that contemplated by such provision.

                  (i)  Confidentiality.  Subject to any contrary  requirement of
law and the right of each party to enforce  its  rights  hereunder  in any legal
action,  each party agrees that it shall keep strictly  confidential,  and shall
cause its employees and agents to keep strictly  confidential,  any  information
which it or any of its agents or  employees  may acquire  pursuant to, or in the
course of performing its  obligations  under,  any provision of this  Agreement;
provided,  however,  that such obligation to maintain  confidentiality shall not
apply to  information  which  (x) at the time of  disclosure  was in the  public
domain  not as a  result  of  acts  by the  receiving  party  or (y)  was in the
possession of the receiving party at the time of disclosure.

                  (j) Headings.  Descriptive  headings are for convenience  only
and shall not control or affect the meaning or  construction of any provision of
this Agreement.

                  (k)  Counterparts.  For the  convenience  of the parties,  any
number of  counterparts of this Agreement may be executed by the parties hereto,
and each  such  executed  counterpart  shall  be,  and shall be deemed to be, an
original instrument.

                                      -18-

<PAGE>



                  (l) Notices. All notices,  consents,  requests,  instructions,
approvals and other  communications  provided for herein shall be validly given,
made or served, if in writing and delivered personally,  by telegram or sent by
registered mail, postage prepaid to:

                  TDS at:                   30 North LaSalle Street
                                            Suite 4000
                                            Chicago, IL  60602-2507
                                            Attention:  President

                  with separate copies at such address to the attention of the 
                  Chief Financial Officer and the Corporate Secretary

                  Aerial at:        8410 W. Bryn Mawr Ave.
                                            Suite 1100
                                            Chicago, IL 60631
                                            Attention:  President

                  with separate copies at such address to the attention of the 
                  Chief Financial Officer and the Corporate Secretary

                  AOC at:                   8410 W. Bryn Mawr Ave.
                                            Suite 1100
                                            Chicago, IL 60631
                                            Attention:  President

                  with separate copies at such address to the attention of the 
                  Chief Financial Officer and the Corporate Secretary


or to such other  address as any party may,  from time to time,  designate  in a
written  notice  given in a like manner.  Any notice given under this  Agreement
shall be deemed delivered when received at the appropriate address.


                                      -19-

<PAGE>



                  (m)  Governing  Law. This  Agreement  shall be governed by and
construed  and  enforced  in  accordance  with the laws of the State of Illinois
applicable to contracts made and to be performed therein.

                  IN  WITNESS  WHEREOF,  TDS,  Aerial and AOC have  caused  this
Agreement to be duly executed by their respective officers, each of whom is duly
authorized, all as of the day and year first above written.

                                     Telephone and Data Systems, Inc.


                                     By:      /s/ LeRoy T. Carlson, Jr.
                                              --------------------------------
                                              LeRoy T. Carlson, Jr.
                                              President and CEO


                                     Aerial Communications, Inc.


                                     By:      /s/ Donald W. Warkentin
                                              --------------------------------
                                              Donald W. Warkentin
                                              President and CEO


                                     Aerial Operating Co., Inc.


                                     By:      /s/ Donald W. Warkentin
                                              ---------------------------------
                                              Donald W. Warkentin
                                              President


                   Signature page of Tax Allocation Agreement
                         dated as of September 8, 1998.


                                      -20-

<PAGE>



                                                                    EXHIBIT 99.7

                                                                  EXECUTION COPY

                                    GUARANTY

                  This  GUARANTY  ("Guaranty")  is  made as of the  31st  day of
August,  1998,  by Aerial  Communications,  Inc.,  a Delaware  corporation  (the
"Guarantor"),  in  favor  of  Telephone  and  Data  Systems,  Inc.,  a  Delaware
corporation (the "Lender") under that certain Revolving Credit Agreement of even
date  herewith  by  and  among  Aerial  Operating  Company,   Inc.,  a  Delaware
corporation  (the  "Borrower")  and the Lender (the  "Credit  Agreement").  Such
Credit  Agreement,  as it may be amended,  modified or supplemented from time to
time, is hereinafter  referred to as the "Credit  Agreement".  Unless  otherwise
defined herein,  capitalized  terms used herein shall have the meanings ascribed
to them in the Credit Agreement.

                  1. Guaranty.  (i) For value received and in  consideration  of
any loan, advance or financial  accommodation of any kind whatsoever heretofore,
now or  hereafter  made,  given or granted to the  Borrower by the  Lender,  the
Guarantor unconditionally  guarantees for the benefit of the Lender the full and
prompt  payment  when  due,  whether  at  maturity  or  earlier,  by  reason  of
acceleration or otherwise,  and at all times  thereafter,  of all of the payment
and  performance  of  all  now  existing  and  hereafter   acquired  or  arising
obligations  and liabilities of the Borrower to the Lender under or with respect
to the Credit Agreement, whether or not fixed, matured, unmatured, liquidated or
contingent,  with  respect to  principal,  interest,  expenses,  indemnities  or
otherwise (including, without limitation, interest accruing following the filing
of a bankruptcy  petition by or against the  Borrower,  at the  applicable  rate
specified in the Credit Agreement,  whether or not such interest is allowed as a
claim in bankruptcy) (hereinafter, collectively, the "Obligations").

                  (ii) At any time after the  occurrence of an Event of Default,
the Guarantor  shall pay to the Lender,  on demand and in immediately  available
funds,  the full amount of the Obligations  (including any portion thereof which
is not yet due and payable).  The Guarantor  further agrees to pay to the Lender
and reimburse the Lender for, on demand and in immediately  available funds, (a)
all losses  (including,  without  limitation,  lost  profits),  fees,  costs and
expenses  (including,  without  limitation,  all court costs and  attorneys' and
paralegals'  fees,  costs and  expenses)  paid or incurred by the Lender in: (1)
endeavoring  to  collect  all  or  any  part  of  the  Obligations  from,  or in
prosecuting  any action against,  the Borrower or the Guarantor  relating to the
Credit Agreement,  this Guaranty or the transactions  contemplated  thereby; (2)
taking any action  with  respect to any  security  or  collateral  securing  the
Obligations  or the  Guarantor's  obligations  hereunder;  and  (3)  preserving,
protecting or defending the  enforceability  of, or enforcing,  this Guaranty or
its rights hereunder (all such costs and expenses are hereinafter referred to as
the "Expenses") and (b) interest on (1) the Obligations  which do not constitute
interest,  (2) to the extent permitted by applicable law, the Obligations  which
constitute  interest,  and (3) the Expenses,  from the date of demand under this
Guaranty  until  paid  in full  at  post-maturity  per  annum  rate of  interest
described  in Section 3 of the  Credit  Agreement  (the  "Interest  Rate").  The
Guarantor  hereby agrees that this  Guaranty is an absolute  guaranty of payment
and is not a guaranty of collection.


                                       

<PAGE>



                  2. Obligations Unconditional. The Guarantor hereby agrees that
its obligations under this Guaranty shall be unconditional, irrespective of:

                  (i)  the  validity,  enforceability,  avoidance,  novation  or
         subordination of any of the Obligations, the Credit Agreement or of any
         promissory note or other instrument,  document or agreement  evidencing
         or relating to all or any part of the  Obligations  (collectively,  the
         "Loan Documents");

                  (ii) the  absence  of any  attempt  by, or on behalf  of,  the
         Lender to collect,  or to take any other action to enforce,  all or any
         part of the Obligations whether from or against the Borrower, any other
         guarantor of the Obligations or any other person or entity;

                  (iii) the  election  of any  remedy  by, or on behalf  of, the
         Lender with respect to all or any part of the Obligations;

                  (iv) the waiver, consent,  extension,  forbearance or granting
         of any  indulgence  by, or on behalf of, the Lender with respect to any
         provision of any of the Loan Documents;

                  (v) the failure of the Lender to take any steps to perfect and
         maintain  its  security  interest in, or to preserve its rights to, any
         security or collateral for the Obligations;

                  (vi) the  election  by, or on behalf  of, the  Lender,  in any
         proceeding instituted under Chapter 11 of Title 11 of the United States
         Code  (11  U.S.C.  101  et  seq.)  (the  "Bankruptcy   Code"),  of  the
         application of Section 1111(b)(2) of the Bankruptcy Code;

                  (vii) any  borrowing  or grant of a security  interest  by the
         Borrower, as debtor-in-possession, under Section 364 of the Bankruptcy 
         Code;

                  (viii) the  disallowance,  under Section 502 of the Bankruptcy
         Code,  of all or any portion of the claims of the Lender for  repayment
         of all or any part of the Obligations or any Expenses; or

                  (ix) any other circumstance which might otherwise constitute a
         legal  or  equitable  discharge  or  defense  of  the  Borrower  or the
         Guarantor.

                  3. Enforcement;  Application of Payments.  Upon the occurrence
of an Event of Default,  the Lender may proceed  directly  and at once,  without
notice,  against  the  Guarantor  to obtain  performance  of and to collect  and
recover the full  amount,  or any portion,  of the  Obligations,  without  first
proceeding  against the Borrower or any other  person or entity,  or against any
security  or  collateral  for the  Obligations.  Subject  only to the  terms and
provisions of the Credit Agreement, the Lender shall have the exclusive right to
determine the  application of payments and credits,  if any, from the Guarantor,
the Borrower or from any other Person on account of the Obligations or any other
liability of the Guarantor to the Lender.

                                       -2-

<PAGE>



                  4.  Waivers.   (i)  The  Guarantor  hereby  waives  diligence,
presentment,  demand of  payment,  filing of claims with a court in the event of
receivership  or bankruptcy  of the Borrower,  protest or notice with respect to
the Obligations, all setoffs and counterclaims and all presentments, demands for
performance, notices of nonperformance, protests, notices of protest, notices of
dishonor  and  notices of  acceptance  of this  Guaranty,  the  benefits  of all
statutes of limitation,  and all other demands whatsoever (and shall not require
that  the  same  be  made  on  the  Borrower  as a  condition  precedent  to the
Guarantor's obligations hereunder), and covenants that this Guaranty will not be
discharged,  except  by  complete  payment  (in  cash)  and  performance  of the
Obligations and any other obligations  contained  herein.  The Guarantor further
waives all notices of the existence,  creation or incurring of new or additional
indebtedness,  arising either from additional  loans extended to the Borrower or
otherwise, and also waives all notices that the principal amount, or any portion
thereof, and/or any interest on any instrument or document evidencing all or any
part of the  Obligations is due,  notices of any and all  proceedings to collect
from the maker,  any  endorser or any other  guarantor of all or any part of the
Obligations, or from any other person or entity, and, to the extent permitted by
law, notices of exchange,  sale,  surrender or other handling of any security or
collateral  given to the  Lender  to  secure  payment  of all or any part of the
Obligations.

                  (ii) The Lender is hereby authorized, without notice or demand
and without  affecting the liability of the  Guarantor  hereunder,  from time to
time, (a) to renew, extend,  accelerate or otherwise change the time for payment
of,  or other  terms  relating  to,  all or any part of the  Obligations,  or to
otherwise  modify,  amend or change  the terms of any  promissory  note or other
agreement,  document or instrument now or hereafter  executed by the Borrower or
any other  guarantor of the  Obligations  and delivered to or for the benefit of
the  Lender;  (b)  to  accept  partial  payments  on  all  or  any  part  of the
Obligations;  (c) to take and hold security or collateral for the payment of all
or any part of the Obligations, this Guaranty, or any other guaranties of all or
any  part of the  Obligations  or  other  liabilities  of the  Borrower,  (d) to
exchange,  enforce,  waive and release any such security or  collateral;  (e) to
apply such security or collateral and direct the order or manner of sale thereof
as in  its  discretion  it may  determine;  (f) to  settle,  release,  exchange,
enforce,  waive, compromise or collect or otherwise liquidate all or any part of
the  Obligations,  this  Guaranty,  any other guaranty of all or any part of the
Obligations,  and any security or collateral for the Obligations or for any such
guaranty.  Any of the foregoing may be done in any manner,  without affecting or
impairing the obligations of the Guarantor hereunder.

                                       -3-

<PAGE>



                  5.  Setoff.  At  any  time  after  all  or  any  part  of  the
Obligations  have become due and payable (by  acceleration  or  otherwise),  the
Lender may,  without notice to the Guarantor and regardless of the acceptance of
any security or collateral for the payment hereof,  appropriate and apply toward
the payment of all or any part of the Obligations (i) any indebtedness due or to
become due from the Lender to the  Guarantor,  and (ii) any  moneys,  credits or
other property  belonging to the  Guarantor,  at any time held by or coming into
the possession of the Lender or its affiliates.

                  6.  Financial   Information.   The  Guarantor  hereby  assumes
responsibility  for keeping  itself  informed of the financial  condition of the
Borrower and any and all endorsers and/or other guarantors of all or any part of
the  Obligations,  and of all  other  circumstances  bearing  upon  the  risk of
nonpayment of the Obligations,  or any part thereof, that diligent inquiry would
reveal,  and the  Guarantor  hereby agrees that the Lender shall have no duty to
advise the Guarantor of information  known to it regarding such condition or any
such circumstances. In the event the Lender, in its sole discretion,  undertakes
at any  time  or  from  time to time to  provide  any  such  information  to the
Guarantor,  the  Lender  shall be  under  no  obligation  (i) to  undertake  any
investigation not a part of its regular business  routine,  (ii) to disclose any
information  which the Lender,  pursuant to  accepted or  reasonable  commercial
finance or banking practices,  wishes to maintain  confidential or (iii) to make
any other or future  disclosures of such information or any other information to
the Guarantor.

                  7. No Marshalling;  Reinstatement.  The Guarantor consents and
agrees that neither the Lender nor any person or entity  acting for or on behalf
of the Lender shall be under any  obligation  to marshall any assets in favor of
the  Guarantor  or against or in payment of any or all of the  Obligations.  The
Guarantor further agrees that, to the extent that the Borrower, the Guarantor or
any other  guarantor  of all or any part of the  Obligations  makes a payment or
payments to the Lender, or the Lender receives any proceeds of Collateral, which
payment or payments or any part thereof are subsequently  invalidated,  declared
to be fraudulent or preferential,  set aside and/or required to be repaid to the
Borrower,  the  Guarantor,  such other  guarantor or any other Person,  or their
respective estates, trustees,  receivers or any other party, including,  without
limitation,  the  Guarantor,  under any  bankruptcy  law,  state or federal law,
common law or equitable cause, then, to the extent of such payment or repayment,
the part of the  Obligations  which has been paid,  reduced or satisfied by such
amount shall be reinstated and continued in full force and effect as of the time
immediately preceding such initial payment, reduction or satisfaction.

                  8. Subrogation.  Until the Obligations have been paid in full,
the  Guarantor  (i) shall  have no right of  subrogation  with  respect  to such
Obligations and (ii) waives any right to enforce any remedy which the Lender now
has or may hereafter have against the Borrower, any endorser or any guarantor of
all or any part of the  Obligations  or any  other  person  or  entity,  and the
Guarantor  waives any benefit of, and any right to participate  in, any security
or collateral given to the Lender to secure the payment or performance of all or
any part of the  Obligations  or any  other  liability  of the  Borrower  to the
Lender.

                                                                                
                  9. Subordination. The Guarantor agrees that any and all claims
of the Guarantor  against the Borrower,  any endorser or any other  guarantor of
all or any part of the Obligations, or

                                       -4-

<PAGE>



against any of their respective properties,  shall be subordinate and subject in
right of payment to the prior payment,  in full and in cash, of all  Obligations
(including,  without  limitation,  interest  accruing  following the filing of a
bankruptcy petition by or against the Borrower, at the applicable rate specified
in the Credit  Agreement,  whether or not such interest is allowed as a claim in
bankruptcy). Notwithstanding any right of the Guarantor to ask, demand, sue for,
take or receive any payment from the  Borrower,  all rights,  liens and security
interests  of the  Guarantor,  whether now or  hereafter  arising and  howsoever
existing,  in any  assets  of the  Borrower  (whether  constituting  part of the
security or collateral  given to the Lender to secure payment of all or any part
of the  Obligations or otherwise)  shall be and hereby are  subordinated  to the
rights of the  Lender in those  assets.  The  Guarantor  shall  have no right to
possession  of any such asset or to  foreclose  upon any such asset,  whether by
judicial action or otherwise, unless and until all of the Obligations shall have
been  fully  paid and  satisfied  and all  financing  arrangements  between  the
Borrower and the Lender have been  terminated.  If all or any part of the assets
of the  Borrower,  or the  proceeds  thereof,  are subject to any  distribution,
division or  application  to the creditors of the Borrower,  whether  partial or
complete,  voluntary  or  involuntary,  and  whether  by reason of  liquidation,
bankruptcy, arrangement,  receivership,  assignment for the benefit of creditors
or any  other  action or  proceeding,  or if the  business  of the  Borrower  is
dissolved or if substantially  all of the assets of the Borrower are sold, then,
and in any such event,  any payment or  distribution  of any kind or  character,
either  in cash,  securities  or other  property,  which  shall  be  payable  or
deliverable  upon or with  resect to any  indebtedness  of the  Borrower  to the
Guarantor  ("Borrower  Indebtedness") shall be paid or delivered directly to the
Lender for  application on any of the  Obligations,  due or to become due, until
such Obligations  shall have first been fully paid and satisfied.  The Guarantor
irrevocably  authorizes and empowers the Lender to demand,  sue for, collect and
receive every such payment or distribution and give acquittance  therefor and to
make and  present  for and on behalf of the  Guarantor  such proofs of claim and
take such other action, in the Lender's own name or in the name of the Guarantor
or otherwise,  as the Lender may deem necessary or advisable for the enforcement
of this  Guaranty.  The  Lender  may  vote  such  proofs  of  claim  in any such
proceeding,  receive  and  collect any and all  dividends  or other  payments or
disbursements  made thereon in whatever  form the same may be paid or issued and
apply  the  same on  account  of any of the  Obligations.  Should  any  payment,
distribution,  security or  instrument  or  proceeds  thereof be received by the
Guarantor  upon  or with  respect  to the  Borrower  Indebtedness  prior  to the
satisfaction  of all of the  Obligations  and the  termination  of all financing
arrangements  between the Borrower and the Lender,  the Guarantor  shall receive
and hold the same in trust, as trustee,  for the benefit of the Lender and shall
forthwith deliver the same to the Lender, in precisely the form received (except
for the  endorsement  or  assignment  of the  Guarantor  where  necessary),  for
application to any of the Obligations,  due or not due, and, until so delivered,
the same shall be held in trust by the  Guarantor as the property of the Lender.
If the Guarantor fails to make any such endorsement or assignment to the Lender,
the Lender or any of its officers or employees are hereby irrevocably authorized
to make the same. The Guarantor agrees that until the Obligations have been paid
in full (in cash) and  satisfied  and all  financing  arrangements  between  the
Borrower and the Lender have been  terminated,  the Guarantor will not assign or
transfer  to any  Person any claim the  Guarantor  has or may have  against  the
Borrower.


                                       -5-

<PAGE>



                  10. Enforcement;  Amendments; Waivers. No delay on the part of
the Lender in the exercise of any right or remedy  arising under this  Guaranty,
the Credit Agreement,  any of the other Loan Documents or otherwise with respect
to all or any part of the  Obligations,  the Collateral or any other guaranty of
or security  for all or any part of the  Obligations  shall  operate as a waiver
thereof,  and no single or partial  exercise  by the Lender of any such right or
remedy shall preclude any further exercise thereof. No modification or waiver of
any of the provisions of this Guaranty shall be binding upon the Lender,  except
as  expressly  set forth in a writing  duly signed and  delivered by the Lender.
Failure  by the  Lender  at any  time  or  times  hereafter  to  require  strict
performance by the Borrower,  the Guarantor,  any other  guarantor of all or any
part  of  the  Obligations  or any  other  Person  of  any  of  the  provisions,
warranties,  terms and conditions  contained in any of the Loan Documents now or
at any time or times  hereafter  executed by such  Persons and  delivered to the
Lender  shall not waive,  affect or diminish any right of the Lender at any time
or times hereafter to demand strict performance thereof and such right shall not
be deemed to have been  waived by any act or  knowledge  of the  Lender,  or its
agents, officers or employees,  unless such waiver is contained in an instrument
in  writing,  directed  and  delivered  to the  Borrower  or the  Guarantor,  as
applicable,  specifying such waiver,  and is signed by the Lender.  No waiver of
any Event of Default by the Lender shall  operate as a waiver of any other Event
of Default or the same Event of Default on a future  occasion,  and no action by
the Lender  permitted  hereunder  shall in any way affect or impair the Lender's
rights and remedies or the obligations of the Guarantor under this Guaranty. Any
determination  by a  court  of  competent  jurisdiction  of  the  amount  of any
principal  and/or  interest  owing  by the  Borrower  to  the  Lender  shall  be
conclusive  and binding on the Guarantor  irrespective  of whether the Guarantor
was a arty to the suit or action in which such determination was made.

                  11.  Effectiveness;  Termination.  This Guaranty  shall become
effective  upon its execution by the Guarantor and shall  continue in full force
and effect and may not be terminated or otherwise  revoked until the Obligations
shall have been fully paid in cash and discharged  and the Credit  Agreement and
all financing  arrangements  between the Borrower and the Lender shall have been
terminated.  If,  notwithstanding  the foregoing,  the Guarantor  shall have any
right under  applicable law to terminate or revoke this Guaranty,  the Guarantor
agrees  that such  termination  or  revocation  shall not be  effective  until a
written notice of such revocation or termination, specifically referring hereto,
signed by the Guarantor,  is actually received by the Lender.  Such notice shall
not affect the right and power of the Lender to enforce  rights arising prior to
receipt thereof by the Lender.  If the Lender grants loans or takes other action
after the  Guarantor  terminates  or revokes this Guaranty but before the Lender
receives  such written  notice,  the rights of the Lender with  respect  thereto
shall be the same as if such termination or revocation had not occurred.

                  12.  Successors  and Assigns.  This Guaranty  shall be binding
upon the  Guarantor and upon its  successors  and assigns and shall inure to the
benefit of the Lender and its successors and assigns;  all references  herein to
the Borrower and to the Guarantor  shall be deemed to include  their  respective
successors  and assigns.  The  successors  and assigns of the  Guarantor and the
Borrower shall include, without limitation, their respective receivers, trustees
or  debtors-in-possession.  All  references  to the singular  shall be deemed to
include the plural where the context so requires.


                                       -6-

<PAGE>



                  13.  Governing  Law.  This  Guaranty  has  been  executed  and
delivered by the parties hereto in Chicago,  Illinois.  Any dispute  between the
Lender  and  the  Guarantor  arising  out  of or  related  to  the  relationship
established  between them in connection with this Guaranty,  and whether arising
in contract,  tort,  equity, or otherwise,  shall be resolved in accordance with
the internal  laws,  and not the  conflicts of law  provisions,  of the State of
Illinois.

                  14. Waiver of Jury Trial. Each of the Guarantor and the Lender
waives any right to trial by jury in any dispute,  whether sounding in contract,
tort,  or  otherwise,  between  the Lender and the  Guarantor  arising out of or
related  to  the  transactions  contemplated  by  this  Guaranty  or  any  other
instrument,  document or agreement executed or delivered in connection herewith.
Either the Guarantor or the Lender may file an original counterpart or a copy of
this Guaranty  with any court as written  evidence of the consent of the parties
hereto to the waiver of their right to trial by jury.

                  15. Notices. All notices and other communications  required or
desired to be served,  given or delivered  hereunder shall be in writing or by a
telecommunications  device  capable of  creating  a printed  record and shall be
addressed to the party to be notified as follows:

         if to the Guarantor, at:

                  Aerial Communications, Inc.
                  8410 West Bryn Mawr
                  Suite 1100
                  Chicago, Illinois   60631
                  Attention: Vice President-Finance
                  Telecopy:  (773) 399-4170

         if to the Lender, at

                  Telephone and Data Systems, Inc.
                  30 North LaSalle Street
                  Suite 4000
                  Chicago, Illinois  60602
                  Attention:  Treasurer
                  Telecopy:   (312) 630-9299/1908

         with a copy to

                  Sidley & Austin
                  One First National Plaza
                  Chicago, Illinois  60603
                  Attention: Michael G. Hron, Esq.
                  Telecopy:  (312) 853-7036


                                       -7-

<PAGE>



or, as to each party,  at such other  address as  designated  by such party in a
written notice to the other party. All such notices and communications  shall be
deemed to be validly  served,  given or delivered  (i) three (3) days  following
deposit in the United  States  mails,  with proper  postage  prepaid;  (ii) upon
delivery  thereof if delivered  by hand to the party to be notified;  (iii) upon
delivery thereof to a reputable overnight courier service, with delivery charges
prepaid;  or (iv) upon  confirmation  of  receipt  thereof if  transmitted  by a
telecommunications device.

                  16.  Severability.  Wherever possible,  each provision of this
Guaranty  shall be interpreted in such manner as to be effective and valid under
applicable  law, but if any provision of this Guaranty shall be prohibited by or
invalid under such law, such  provision  shall be  ineffective  to the extent of
such  prohibition  or  invalidity  without  invalidating  the  remainder of such
provision or the remaining provisions of this Guaranty.

                  17. Merger.  This Guaranty  represents the final  agreement of
the  Guarantor  with  respect  to the  matters  contained  herein and may not be
contradicted by evidence of prior or contemporaneous  agreements,  or subsequent
oral agreements, between the Guarantor and the Lender.

                  18. Execution in  Counterparts.  This Guaranty may be executed
in any  number of  counterparts  and by  different  parties  hereto in  separate
counterparts,  each of which when so executed  shall be deemed to be an original
and all of which taken together shall constitute one and the same agreement.

                                    * * * * *









                                       -8-

<PAGE>



                  IN WITNESS  WHEREOF,  this  Guaranty has been duly executed by
the Guarantor as of the day and year first set forth above.


                                                AERIAL COMMUNICATIONS, INC.



                                                By:      /s/ Donald W. Warkentin
                                                         -----------------------
                                                         Donald W. Warkentin
                                                         President & CEO


Acknowledged and agreed to 
as of the 31st day of August, 1998.


TELEPHONE AND DATA SYSTEMS, INC.



By:      /s/ LeRoy T. Carlson, Jr.
         --------------------------------
         LeRoy T. Carlson, Jr.
         President & CEO



                        SIGNATURE PAGE TO AERIAL GUARANTY
                                 OF TDS LOANS TO
                              AERIAL OPERATING CO.









                                       -9-

<PAGE>



                                                                    EXHIBIT 99.8

                                                                  EXECUTION COPY

                           REVOLVING CREDIT AGREEMENT



         This  Revolving  Credit  Agreement,  dated as of August  31,  1998,  is
entered into between  Telephone and Data Systems,  Inc., a Delaware  corporation
(herein called "TDS"),  and Aerial  Operating Co., Inc., a Delaware  corporation
(herein called the "Company").

         WHEREAS,  (i) TDS  owns   approximately   82%  of  the   issued   and
outstanding  shares of the  capital  stock of  Aerial  Communications,  Inc.,  a
Delaware  corporation  formerly known as American  Portable  Telecommunications,
Inc. ("Aerial"),  and (ii) Aerial owns 100% of the issued and outstanding shares
of the capital stock of the Company;

         WHEREAS,  TDS and Aerial  are  parties  to a certain  Revolving  Credit
Agreement dated as of August 1, 1995, as heretofore  amended (the "Aerial Credit
Agreement"),  pursuant to which TDS (including  certain of its  affiliates)  has
made revolving loans to Aerial, the entire proceeds of which have been loaned to
the Company by Aerial;

         WHEREAS,  as of August 31, 1998, the outstanding  principal  balance of
the loans  made by TDS and its  affiliates  to Aerial  under the  Aerial  Credit
Agreement,  and the outstanding principal balance of the loans made by Aerial to
the Company with the proceeds of such loans,  is  $665,000,000.00;  as of August
31,  1998,   accrued  and  unpaid   interest  with  respect  to  such  loans  is
$5,620,000.01;


<PAGE>




         WHEREAS, representatives of TDS, Aerial and the Company have negotiated
with  representatives  of Sonera  Ltd.  (f/k/a  Sonera  Corporation),  a limited
liability   company  organized  under  the  laws  of  the  Republic  of  Finland
("Sonera"),  a Purchase Agreement (the "Purchase  Agreement")  pursuant to which
the Company  would sell newly issued common stock of the Company to Sonera in an
amount  which,  upon  issuance,  would  constitute  19.423%  of the  issued  and
outstanding common stock of the Company;

         WHEREAS,   in   connection   with  the  closing  of  the   transactions
contemplated by the Purchase Agreement,  the Company, Aerial and TDS have agreed
that TDS and the Company  would enter into this  Revolving  Credit  Agreement in
order to (i)  enable  the  Company  to repay  its  loans  from  Aerial  in their
entirety,  together with accrued and unpaid interest with respect thereto , (ii)
enable  Aerial to repay its loans from TDS and its  affiliates  under the Aerial
Credit  Agreement in their  entirety,  together with accrued and unpaid interest
thereunder  and (iii)  provide  for TDS's  commitment  to  provide,  directly or
through  affiliates,  additional  revolving credit loans directly to the Company
for general corporate purposes;
         WHEREAS,  in order to provide the Company  with funds for the  purposes
specified above, the Company has requested TDS to extend loans to the Company in
an aggregate  amount not to exceed the  "Applicable  Maximum Amount" (as defined
below), and TDS is willing to extend such loans upon the terms and conditions of
this Revolving Credit Agreement;


                                       -2-

<PAGE>



         NOW,  THEREFORE,  in  consideration  of the  mutual  agreements  herein
contained, the parties hereto agree to as follows:

         1.  COMMITMENT  OF TDS.  Subject  to the terms and  conditions  of this
Revolving Credit  Agreement,  TDS, either directly or through one or more of its
Subsidiaries,  agrees to lend to the  Company on a revolving  basis,  during the
period  from the date  hereof  through  December  31,  1999,  such amount as the
Company may from time to time request  upon  written  notice given not less than
five Business  Days before the date of the loan,  but not exceeding an aggregate
outstanding  principal amount equal to the Applicable  Maximum Amount at any one
time  outstanding;  provided,  however,  effective  as of the date  hereof  upon
satisfaction  or waiver by TDS of the  conditions set forth in Section 8 hereof,
(a) the  Company  shall be deemed  to have  irrevocably  requested  that TDS and
certain of its affiliates  make, and TDS and certain of its affiliates  shall be
deemed to have made, an initial loan to the Company under this Revolving  Credit
Agreement in the aggregate  principal  amount of $665,000,000 and (b) the entire
proceeds  of such  initial  loan  shall be deemed to have  been  applied  by the
Company  to the  payment in full of all loans  heretofore  made by Aerial to the
Company which are  outstanding as of the date hereof,  together with all accrued
and unpaid  interest  thereon,  and further  applied by Aerial to the payment in
full of all loans heretofore made by TDS and certain of its affiliates to Aerial
under the Aerial Credit  Agreement  which are outstanding as of the date hereof,
together with all accrued and unpaid interest thereon,  in each case without the
necessity  of any actual  transfer of funds by TDS, any of its  affiliates,  the
Company or Aerial.  Notwithstanding any other provision of this Revolving Credit
Agreement, no loan shall be required

                                       -3-

<PAGE>



to be made hereunder if any Event of Default has occurred, or if any Default has
occurred and is continuing.

         2.  EVIDENCE OF  BORROWINGS.  Each  borrowing  hereunder by the Company
shall be evidenced by a recording of the  borrowing on a schedule  substantially
in the form set forth in Exhibit A and shall be dated the date of the borrowing,
and shall mature on December 31, 1999,  unless the Company in the written notice
requesting the loan specifies that an earlier date on which an interest  payment
is due shall be the maturity date.  Notwithstanding the foregoing, the aggregate
outstanding  principal  balance of the loans  shall be  prepaid  by the  Company
concurrently  with the Company's or Aerial's  receipt of any proceeds of debt or
equity  securities issued by any such entity to, or loans or advances made to or
for the  benefit of any such  entity by, any person or entity  other than TDS or
any affiliate of TDS, which  prepayments shall be made by the Company in amounts
equal to the gross  proceeds of such  securities,  loans or advances  net of all
reasonable  expenses and fees paid by the Company or Aerial in  connection  with
the closing of such transaction.

         3.  PAYMENT  OF  INTEREST  AND  PRINCIPAL.  The  Company  agrees to pay
interest on the unpaid  principal  amount of each borrowing  hereunder at a rate
per annum equal to 1 1/2% above the Prime Lending Rate as in effect from time to
time,  payable on the first day of January,  April,  July and October  until the
principal   amount  becomes  due  (whether  at  maturity,   by  acceleration  or
otherwise);  and to pay on demand interest on any overdue  principal and (to the
extent permitted by applicable law) on any overdue installment of interest, at a
rate per annum  equal to 3 1/2% above the Prime  Lending  Rate as in effect from
time to time. Interest shall be computed on the basis of a

                                       -4-

<PAGE>



year of 360 days,  as the case may be, and actual days  elapsed  (including  the
first day but excluding the last day) occurring in the period of which payable.

         4. COMPANY'S RIGHT TO PREPAY  BORROWINGS.  The Company may from time to
time and  without  premium  prepay  any  borrowing  in  whole  or in  part.  Any
prepayment of the full amount of any borrowings  shall include accrued  interest
thereon.  Any prepayment  made upon any borrowing  shall reinstate the Credit in
the amount of such prepayment.

         5. TERM OF REVOLVING  CREDIT  AGREEMENT.  Unless  sooner  terminated as
elsewhere provided herein,  this Revolving Credit Agreement and TDS's obligation
to furnish the Credit shall  terminate  on December  31,  1999.  Notwithstanding
anything in this Revolving Credit  Agreement to the contrary,  in the event that
TDS's direct  ownership of the  outstanding  voting equity  securities of Aerial
shall be less than 70% (computed on a fully-diluted  basis), TDS's commitment to
make  additional  loans  hereunder  shall  expire on the  180th day  immediately
following the date of such event.

         6.  REPRESENTATIONS  AND  WARRANTIES  OF THE COMPANY.  To induce TDS to
grant the Credit and make loans hereunder,  the Company  represents and warrants
that:

                  (a) The Company and its  Subsidiaries are  corporations,  each
         duly organized and existing,  in good  standing,  under the laws of the
         jurisdiction of its incorporation,  and each has the corporate power to
         own its property and to carry on its business as now being

                                       -5-

<PAGE>



         conducted.  The Company is duly qualified to do business and is in good
         standing in each  jurisdiction,  if any, in which the  character of the
         properties owned or leased by it therein or in which the transaction of
         its  business  makes  such  qualifications  necessary,  except for such
         failures  to  qualify  or to be in good  standing,  if  any,  as in the
         aggregate  are not material to the business or financial  conditions of
         the Company and its Subsidiaries taken as a whole.

                  (b) The  company has full  corporate  power and  authority  to
         enter into this  Revolving  Credit  Agreement,  to make the  borrowings
         hereunder,  to  execute  and  deliver  the  Notes,  and  to  incur  the
         obligations  provided  for herein and  therein,  all of which have been
         duly authorized by all proper and necessary corporate action.

                  (c) All authorizations,  consents,  approvals,  registrations,
         exemptions and licenses with or from governmental authorities which are
         necessary for the borrowings  hereunder,  the execution and delivery of
         this Revolving Credit  Agreement,  the Notes and the performance by the
         Company of its obligations  hereunder and thereunder have been effected
         or obtained and are in full force and effect.

                  (d) This Revolving Credit Agreement constitutes and the Notes,
         when executed and delivered  pursuant hereto for value  received,  will
         constitute,  the valid and legally  binding  obligations of the Company
         enforceable in accordance with their terms, subject, as to enforcement,
         to  bankruptcy,  insolvency,  reorganization  and other laws of general
         applicability relating to or affecting creditor's rights and to general
         equity principles.

                                       -6-

<PAGE>



                  (e) There are no  proceedings  or  investigations  pending  or
         threatened  before  any  court  or  arbitrator  or  before  or  by  any
         governmental authority in which there is a reasonable possibility of an
         adverse decision which would  materially  adversely affect the business
         or financial  conditions of the Company and its Subsidiaries taken as a
         whole or  materially  impair the  ability of the Company to perform its
         obligations under this Revolving Credit Agreement or the Notes.

                  (f) There is no statute,  regulation, rule, order or judgment,
         and no provision of any mortgage, indenture, contract, license, permit,
         agreement or other  instrument or obligation  binding on the Company or
         any Subsidiary or affecting  their  respective  properties  which would
         prohibit,  conflict  (except to the extent cured by waivers or consents
         or the extent  the  consequences  of such  conflict  would not,  in the
         aggregate,  be material to the  financial  condition of the Company and
         its  Subsidiaries  taken as a  whole)  with or in any way  prevent  the
         execution,  delivery,  or carrying  out of the terms of this  Revolving
         Credit Agreement and/or of the Notes.

                  (g) The Company and its  Subsidiaries,  taken as a whole, have
         good, valid and marketable title to their respective real, personal and
         other  properties and assets material to the conduct of the business of
         the  Company  and its  Subsidiaries,  free and clear of all  mortgages,
         liens, pledges, charges or encumbrances.



                                       -7-

<PAGE>




         7.  COVENANTS OF THE COMPANY.
                  (a) Until the  expiration  or  termination  of the  Credit and
         thereafter  until all the Notes and other  liabilities  of the  Company
         hereunder are paid in full, the Company as appropriate shall:

                           (1)  furnish  TDS,  (i)  within  120 days  after each
                  fiscal year of the Company,  a copy of the annual audit report
                  of  the   Company   and  its   Subsidiaries,   prepared  on  a
                  consolidated  basis  and  in  conformity  with  the  generally
                  accepted  accounting  principles applied on a basis consistent
                  with  that  of  the  preceding  fiscal  year,  and  signed  by
                  independent certified public accountants  satisfactory to TDS,
                  together with financial statements  consisting of consolidated
                  balance sheets of the Company and its  Subsidiaries  as of the
                  end of such fiscal year and  consolidated  statement of income
                  and expense,  retained  earnings,  paid-in capital and surplus
                  and cash flow  statement  of the Company and its  Subsidiaries
                  for such  fiscal  year;  (ii) as soon as  available  but in no
                  event  more  than  120  days  after  the  close of each of the
                  Company's  fiscal year, a letter or opinion of the accountants
                  who prepared  the annual audit report  relating to the Company
                  and  its   Subsidiaries   stating  whether  anything  in  such
                  accountants'  examination  has revealed the  occurrence of any
                  event which  constitutes a Default or an Event of Default and,
                  if so, stating the facts with respect  thereto  (provided that
                  the  furnishing  of such  letter or opinion  shall not require
                  expansion  of the  scope  of such  accountants'  examination);
                  (iii) within 60 days after each quarter (except the last

                                       -8-

<PAGE>



                  quarter)  of each fiscal  year of the  Company,  a copy of its
                  unaudited financial statements, similarly prepared, consisting
                  of at least a balance  sheet as at the  close of such  quarter
                  and a profit and loss  statement and a cash flow statement and
                  analysis of surplus  for such  quarter and for the period from
                  the  beginning  of  such  fiscal  year  to the  close  of such
                  quarter,  and  signed by a proper  accounting  officer  of the
                  Company  accompanied by a certificate of said officer  stating
                  whether any event has occurred which  constitutes a Default or
                  an Event of  Default;  and (iv) from time to time,  such other
                  information as TDS may reasonably request;

                           (2)  permit,  and cause each of its  Subsidiaries  to
                  permit, TDS to have one or more of its officers,  employees or
                  agents,  upon at least one day's notice, and at TDS's expense,
                  visit and inspect any of the  properties of the Company or any
                  Subsidiary and examine the minute books,  books of account and
                  other records of the Company or any Subsidiary and make copies
                  thereof  or  extracts  therefrom,  and  discuss  its  affairs,
                  finances and accounts with its officers and employees  and, at
                  the   request   of  TDS,   with  the   Company's   independent
                  accountants,  during normal  business  hours and at such other
                  reasonable times and as often as TDS may reasonably desire;

                           (3) maintain,  and cause each of its  Subsidiaries to
                  maintain,  insurance  to such extent and against  such hazards
                  and  liabilities  as  is  commonly   maintained  by  companies
                  similarly situated;


                                       -9-

<PAGE>



                           (4) pay, and cause each of its  Subsidiaries  to pay,
                  when due all taxes, assessments, and other liabilities, except
                  and so long as contested in good faith;

                           (5)  preserve  and  maintain,  and cause  each of its
                  Subsidiaries to preserve and maintain, its corporate existence
                  and  all of its  material  (considering  the  Company  and its
                  Subsidiaries   taken  as  a  whole)  rights,   privileges  and
                  Franchises  (including  Franchises and any licenses granted by
                  the Federal Communications Commission) necessary in the normal
                  conduct  of  its  business;   provided  that  nothing   herein
                  contained shall prevent (i) the termination of the business or
                  corporate  existence of any  Subsidiary  which  comprises less
                  than 5% of the  consolidated  assets  of the  Company  and its
                  Subsidiaries,  or (ii)  the  Company  or any  Subsidiary  from
                  merging with another Person if the Company or such  Subsidiary
                  is the surviving corporation or the other Person is controlled
                  by the  Company  or any  Subsidiary,  or any  Subsidiary  from
                  merging into, consolidating with or transferring assets to the
                  Company or another  Subsidiary or any Person controlled by the
                  Company or any  Subsidiary,  provided  that the effect of such
                  merger will not constitute a Default or Event of Default;

                           (6) comply, and cause each Subsidiary to comply, with
                  the  requirements of all applicable laws,  rules,  regulations
                  and orders of any  governmental  authority,  a breach of which
                  would  materially and adversely  affect the business or credit
                  of the

                                      -10-

<PAGE>



                  Company  and its  Subsidiaries  taken as a whole,  except were
                  contested in good faith and by proper proceedings;

                           (7)  promptly  notify TDS upon the  discovery  by any
                  officer of the  Company of the  occurrence  of any  Default or
                  Event of Default,  in each case  describing the nature thereof
                  and the  action  the  Company  proposes  to take with  respect
                  thereto; and

                           (8) cause each  Subsidiary of the Company,  except to
                  the extent limited by partnership  agreements,  to comply with
                  all sections of this Revolving Credit Agreement  applicable to
                  Subsidiaries to the same extent as if such Subsidiary were the
                  Company.

                  (b) Until the  expiration  or  termination  of the  Credit and
         thereafter  until all the Notes and other  liabilities  of the  Company
         hereunder are paid in full:

                           (1) the  Company  shall not  purchase  or redeem  any
                  shares of its  stock  (other  than  pursuant  to the  Purchase
                  Agreement,  in accordance with Article Fourth of the Company's
                  Certificate of Incorporation,  as amended,  in connection with
                  stock option or other employee  benefit  programs or where the
                  redemption  price is payable in shares of TDS furnished by TDS
                  to the Company to enable it to effect the redemption), declare
                  or pay any dividends thereon or make any other distribution to
                  any  of  its  shareholders,  except  to the  extent  that  the
                  cumulative sum of all such

                                      -11-

<PAGE>



                  payments  (excluding  any  payments  to  redeem  shares of the
                  Company's  stock with  shares of TDS  furnished  by TDS to the
                  Company  to  enable  it to effect  the  redemption)  shall not
                  exceed one-half of the cumulative  consolidated  net income of
                  the Company;

                           (2) the  Company  shall  not incur or permit to exist
                  any  indebtedness  for Borrowed  Money,  except (i) borrowings
                  under this Revolving Credit Agreement, or (ii) indebtedness of
                  the  Company or which is  guaranteed  by the Company if, as to
                  the Company's  obligations  thereunder,  such  indebtedness is
                  subordinate  to all  borrowings  and other  obligations of the
                  Company  under this  Revolving  Credit  Agreement  pursuant to
                  terms,  conditions and subordination  agreements acceptable to
                  TDS, unless otherwise waived in writing by TDS;

                           (3) the  Company  shall not create or permit to exist
                  or allow any of its  Subsidiaries to create or permit to exist
                  any  mortgage,   pledge,   title   retention  lien,  or  other
                  encumbrance  or security  interest  with respect to any assets
                  now owned or hereafter acquired by the Company's Subsidiaries,
                  except  (i)  liens  in  connection  with  the  acquisition  of
                  property  and  attaching  only to the property  acquired,  any
                  licenses related thereto, and the partnership interests in any
                  partnership  making the  acquisition;  (ii) liens for  current
                  taxes not delinquent or as security for taxes being  contested
                  in good faith,  or in connection  with workmen and materialmen
                  for sums not due or sums being contested in good faith;  (iii)
                  liens created in the normal course

                                      -12-

<PAGE>



                  of business to procure surety bonds; (iv) liens on property or
                  assets  of  a  Subsidiary  to  secure   obligations   of  such
                  Subsidiary  to the  Company or another  Subsidiary;  (v) liens
                  existing on real property  owned or leased that are incidental
                  to the conduct of business of the Company or the  ownership of
                  its  property  and  assets  and  that  were  not  incurred  in
                  connection  with the  borrowing  of money or the  obtaining of
                  advances  or  credit,  and  which  do  not  in  the  aggregate
                  materially detract from the value of the assets of the Company
                  and its Subsidiaries taken as a whole or materially impair the
                  use thereof in the  operation  of the  business of the Company
                  and its Subsidiaries  taken as a whole; (vi) liens existing on
                  the date  hereof and  approved  in writing by TDS on or before
                  the date  hereof;  (vii)  liens on assets  of any  corporation
                  existing  at the  time  such  corporation  is  merged  into or
                  consolidated with a Subsidiary or becomes a Subsidiary and not
                  created in contemplation of such event;  (viii) liens existing
                  on any asset prior to the acquisition  thereof by a Subsidiary
                  and not created in  contemplation  of such  acquisition;  (ix)
                  liens arising out of the  refinancing,  extension,  renewal or
                  refunding of any debt secured by any lien  permitted by any of
                  the foregoing clauses of this Section, provided that such debt
                  is not increased and is not secured by any additional  assets;
                  (x) deposits or pledges to secure  obligations  under worker's
                  compensation,  social  security  or  similar  laws,  or  under
                  unemployment insurance; and

                           (4) the  Company  shall not enter  into or be a party
                  to, or allow  any of its  Subsidiaries  to enter  into or be a
                  party  to,  any  contract  for  the  purchase  of   materials,
                  supplies, other property or services if such contract requires
                  that payment be made

                                      -13-

<PAGE>



                  by the  Company  or its  Subsidiaries  regardless  of  whether
                  delivery  is  ever  made of such  materials,  supplies,  other
                  property or services.

         8.  CONDITIONS OF LENDING.  TDS shall not be required to make the first
loan  contemplated  hereunder  unless the Company shall have first  delivered to
TDS:
                  (a) a  certified  copy of the  Company's  Board of  Director's
         resolutions  authorizing  the  execution  and delivery of the Notes and
         this Revolving Credit Agreement;

                  (b)  a  certificate  executed  by  the  President  or  a  Vice
         President of the Company and dated the date of the loan  certifying (i)
         that the warranties and representation made in Section 6 by the Company
         are true and  correct on such date,  (ii) that no Event of Default  has
         occurred or would result from the Company obtaining the requested loan,
         and (iii) that no Default has occurred and is continuing;

                  (c) a Note  appropriately  completed,  duly executed and dated
         the date the loan is to be made;

                  (d) such other documents as TDS shall request;

                  (e) an opinion from counsel to the Company that the Company is
         a corporation  duly  existing  under the laws of the State of Delaware;
         that the Company has full power to execute and deliver  this  Revolving
         Credit Agreement, to borrow money hereunder, to execute and

                                      -14-

<PAGE>



         deliver  its Note at each  borrowing,  and to perform  its  obligations
         under this Revolving Credit Agreement and the Notes;  that such actions
         are not in  conflict  with any  provision  of law or of the  charter or
         bylaws of the Company,  nor in conflict with any agreement binding upon
         the  Company  of which  such  counsel  has  knowledge;  and  that  this
         Revolving  Credit  Agreement  is,  and  the  Notes  when  executed  and
         delivered by the Company will be, the legal and binding  obligations of
         the Company;

                  (f) an agreement and acknowledgment  executed and delivered by
         Aerial,  in form  and  substance  acceptable  in all  respects  by TDS,
         pursuant to which Aerial agrees (i) to the provisions of the proviso to
         the  first  sentence  of  Section  1 hereof  and (ii)  that any and all
         commitments by, or obligations of, TDS to advance  additional  loans or
         provide  any other  accommodations  to Aerial  under the Aerial  Credit
         Agreement have been irrevocably terminated; and

                  (g) an unconditional  and irrevocable  guarantee of all of the
Company's  obligations  under  the  Notes and this  Revolving  Credit  Agreement
executed  and  delivered  by Aerial,  in form and  substance  acceptable  in all
respects to TDS.

         9.  EVENTS  OF  DEFAULT.  The  occurrence  of any  one or  more  of the
following  events,  unless  waived in writing by TDS either  before or after the
occurrence, shall constitute an "Event of Default" hereunder:


                                      -15-

<PAGE>



                  (a) the Company  fails to pay the  principal of or interest of
         any Note when and as the same shall become due and payable,  whether at
         the due date thereof,  by acceleration  or otherwise,  and such failure
         shall  continue for more than five  business days after notice is given
         to the Company;

                  (b) the Company,  or any Subsidiary  which comprises more than
         5% of the  consolidated  assets of the  Company  and its  Subsidiaries,
         admits in  writing  its  inability  to pay its debts as they  mature or
         applies for, consents to, or acquiesces in the appointment of a trustee
         or receiver for the Company or such Subsidiary or any property thereof;
         in the absence of such application, consent, or acquiescence, a trustee
         or receiver is appointed for the Company or any such  Subsidiary or for
         a substantial part of the property of any thereof and is not discharged
         within 30 days; or any bankruptcy, reorganization, debt arrangement, or
         other  proceeding  under  any  bankruptcy  or  insolvency  law,  or any
         dissolution or liquidation proceeding,  is instituted by or against the
         Company of any such Subsidiary,  and if instituted  against the Company
         or any such  Subsidiary is consented to or acquiesced in by the Company
         or any such Subsidiary or remains for 30 days undismissed;

                  (c) any  representation or warranty made by the Company herein
         is untrue in any material respect and such  representation  or warranty
         is not made true within 30 days after an officer of the Company becomes
         aware of such material untruth,  or if such  representation or warranty
         is not made true within 90 days after an officer of the Company becomes
         aware of such material  untruth  provided the Company is trying in good
         faith to make such

                                      -16-

<PAGE>



         representation  or  warranty  true at all times after an officer of the
         Company becomes aware of such material untruth;

                  (d)  any  schedule,  statement,  report,  notice,  or  writing
         furnished by the Company is untrue in any material  respect on the date
         as of which  the  facts set  forth  are  stated  or  certified  if such
         document is not revised to be true and  furnished by the Company to TDS
         within ten days after an officer of the Company  becomes  aware of such
         material untruth;

                  (e)  the  Company  breaches  any of the  terms,  covenants  or
         agreements  herein set forth and such breach  continues (i) for 30 days
         after notice to the  Company,  (ii) for 60 days after an officer of the
         Company  becomes  aware of such  breach,  or (iii) for 90 days after an
         officer of the  Company  becomes  aware of such breach in the case of a
         breach  of  any of the  terms,  covenants  or  agreements  of  Sections
         7(a)(5),  7(a)(6) and  7(b)(3),  provided  that the Company is making a
         good faith  effort to cure the breach at all times  after an officer of
         the Company becomes aware of it;

                  (f) any event  shall  occur or fail to occur if the  effect of
         such  occurrence  or  failure  is to  accelerate  the  maturity  of any
         indebtedness for Borrowed Money (other than the indebtedness under this
         Revolving Credit  Agreement) of the Company or any of its subsidiaries,
         which  indebtedness for Borrowed Money in the aggregate  exceeds 10% of
         the  Company's  consolidated  equity as  reflected  on the most  recent
         consolidated  balance sheet of the Company and its Subsidiaries,  or to
         permit the holder thereof to cause such

                                      -17-

<PAGE>



         indebtedness  to become due prior to the stated maturity  thereof,  and
         any such  occurrence  or failure shall not have been remedied or waived
         within any applicable period of grace;

                  (g) the  Company or any of its  Subsidiaries  defaults  in the
         payment  of  any   indebtedness  for  Borrowed  Money  other  than  the
         indebtedness  under this Revolving Credit Agreement if the aggregate of
         such indebtedness for Borrowed Money,  including the defaulted payment,
         exceeds 10% of the  Company's  consolidated  equity as reflected on the
         most  recent  consolidated   balance  sheet  of  the  Company  and  its
         Subsidiaries; and

                  (h) one or more  judgments  against  the Company or any of its
         Subsidiaries  or  attachments  against  its  property,   which  in  the
         aggregate exceed $2,000,000,  or the operation or result of which would
         be to  interfere  materially  and  adversely  with the  conduct  of the
         business of the Company and its Subsidiaries taken as a whole,  remain,
         unpaid, unstayed on appeal, undischarged, unbonded, or undissmissed for
         a period of 30 days.

          The Company shall immediately advise TDS of any Event of Default or of
any Default.  If any Event of Default shall occur,  whether the Event of Default
shall then be  continuing,  TDS may declare the Credit to be  terminated  at any
time thereafter and all Notes to be due and payable,  whereupon the Credit shall
immediately  terminate,  and all outstanding Notes shall become  immediately due
and payable,  both as to  principal  and  interest,  with  presentment,  demand,
protest  or any  other  notice of any kind,  all of which are  hereby  expressly
waived,   anything   contained   herein  or  in  the   Notes  to  the   contrary
notwithstanding (provided that TDS's commitment hereunder shall

                                      -18-

<PAGE>



forthwith  terminate,  and the unpaid  principal of and accrued  interest on the
loans and all other amounts owing  hereunder shall  automatically  become and be
forthwith due and payable upon the  occurrence of any event  specified in clause
(b) above  without  any such  notice or other  action,  all of which are  hereby
expressly  waived by the Company).  TDS shall promptly advise the Company of any
such  declaration,  but  failure  to do so shall not  impair  the effect of such
declaration.

         10.  DEFINITIONS.
                  (a) Unless otherwise  specified  herein,  all accounting terms
         used herein shall be interpreted,  all  determinations  with respect to
         accounting   matters   hereunder  shall  be  made,  and  all  financial
         statements  and  certificates  and  reports  as  to  financial  matters
         required to be delivered  hereunder  shall be prepared,  in  accordance
         with generally accepted accounting principles.

                  (b) The  following  terms shall have the meanings  ascribed to
them below:

                  "Applicable  Maximum  Amount"  shall  mean,  as of any date of
         determination,  the dollar  amount  set forth in  Schedule I hereto and
         pertaining  to the  period  during  which such date  occurs,  minus the
         aggregate  principal  amount  of all  prepayments  required  to be paid
         pursuant to the last sentence of Section 2.
                  "Borrowed Money" shall mean as to any Person any obligation of
         such Person to repay money,  and  indebtedness of such Person evidenced
         by notes, bonds,  debentures or similar obligations,  any obligation of
         such Person under a conditional sale or other title

                                      -19-

<PAGE>



         retention  agreement,  any obligation of others secured by any asset of
         such Person,  whether or not such obligation is assumed by such Person,
         any obligation of others  Guaranteed by such Person,  all Capital Lease
         Obligations,  and any reimbursement obligations of such Person (whether
         contingent  or  otherwise)  in respect  of  letters of credit,  bankers
         acceptances and similar instruments,  provided,  however, that Borrowed
         Money  indebtedness  shall not  include  performance  bonds,  franchise
         bonds, obligations to reimburse drawings under letters of credit issued
         in lieu of performance or franchise bonds and other obligations of like
         nature, trade payables,  and accrued liabilities and subscriber advance
         payments and deposits,  arising in the ordinary course of such Person's
         business.

                  "Business  Day" shall mean any day on which  commercial  banks
         are not generally authorized or required to close in Chicago, Illinois.

                  "Capital  Lease  obligations"  shall mean, to any Person,  the
         obligations  of such Person to pay rent or other  amounts under a lease
         of (or  other  agreement  containing  the  right  to use)  real  and/or
         personal  property which  obligations are required to be classified and
         accounted  for as a capital  lease on the balance  sheet of such Person
         under generally accepted accounting principles and, for the purposes of
         the Agreement,  the amount of such obligations shall be the capitalized
         amount  thereof,  determined  in  accordance  with  generally  accepted
         accounting principles.

                  "Code"  shall  mean the  Internal  Revenue  Code of  1986,  as
         amended.

                                      -20-

<PAGE>



                  "Control"   (including,   with   its   correlative   meanings,
         "controlled  by" and  under  "common  control  with")  shall  mean  the
         possession, directly or indirectly, of the power to direct or cause the
         direction of the management or policies of a Person.

                  "Credit"  shall  mean  TDS's  commitment  to loan funds to the
         Company  pursuant to the terms and conditions of this Revolving  Credit
         Agreement.

                  "Default"  shall  mean any  event  which,  with the  giving of
         notice  or the lapse of time,  or both,  would  constitute  an Event of
         Default.

                  "Dollars"  (including  "$")  shall  mean  lawful  money of the
United States of America.

                  "Franchise" shall mean a franchise, license,  authorization or
         right to construct,  own, promote,  extend and/or otherwise exploit any
         System  operated  or to be  operated  by  the  Company  or  any  of its
         Subsidiaries granted by the Federal Communications Commission or by any
         state,  county, city, town, village or other local government authority
         but shall not include any such  franchise,  license,  authorization  or
         right which is  incidentally  required  for the purpose of  installing,
         constructing or extending.

                  "Guarantee"   by  any  Person   shall  mean  any   obligation,
         contingent  or  otherwise,   of  such  Person  directly  or  indirectly
         guaranteeing any indebtedness for Borrowed Money or other obligation of
         any other Person, or in any manner providing for the payment of any

                                      -21-

<PAGE>



         indebtedness  for  Borrowed  Money or  other  obligation  of any  other
         Person, or otherwise protecting the holder of such indebtedness against
         loss  (whether by virtue of  partnership  arrangements,  agreements  to
         purchase assets,  goods,  securities or services,  or to take-or-pay or
         otherwise),  provided  that  the term  "guarantee"  shall  not  include
         endorsements  for  collection  or  deposit  in the  ordinary  course of
         business.  The term  "guarantee"  used as a verb shall have correlative
         meaning.

                  "Notes" shall mean any and all promissory notes of the Company
         to TDS,  evidencing  a  borrowing  made  under  this  Revolving  Credit
         Agreement.

                  "Person"   shall  mean  an  individual,   a   corporation,   a
         partnership, a joint venture, a trust or unincorporated organization, a
         joint  stock  company  or similar  organization,  a  government  or any
         political subdivision thereof, or any other legal entity.

                  "Prime Lending Rate" shall mean the rate of interest announced
         by LaSalle  National  Bank  ("LaSalle")  from time to time as its prime
         rate, or if no such rate of interest is announced by LaSalle,  the rate
         of interest  announced  by Bank of America  National  Trust and Savings
         Association from time to time as its "reference rate."

                  "Purchase Agreement" shall mean the Purchase Agreement,  dated
         as of June 1, 1998, by and among TDS, Aerial, the Company and Sonera.


                                      -22-

<PAGE>



                  "Subsidiary"  shall  mean any Person  other  than the  Company
         whose accounts are included in the consolidated financial statements of
         the Company and its Subsidiaries  prepared in accordance with generally
         accepted accounting principles in effect at the time.

                  "System"  shall  mean  the  assets   constituting  a  cellular
         telephone system serving subscribers within a geographical area covered
         by one or more Franchises.

         11.  MISCELLANEOUS.
                  (a) No delay on the part of TDS or the  holder  of any Note in
         the exercise of any power or right shall  operate as a waiver  thereof,
         nor shall any single or partial exercise of any power or right preclude
         other or further exercise  thereof,  or the exercise of any other power
         or right.  No waiver by TDS shall be valid  unless it is in writing and
         signed by the Chief Executive Officer or the Chief Financial Officer of
         TDS and then only to the extent specifically set forth in such writing.

                  (b) All notices, consents, requests,  instructions,  approvals
         and other  communications  provided for herein shall be validly  given,
         made or served, if in writing and delivered personally,  by telegram or
         sent by registered mail, postage prepaid to:

                           TDS at:                   30 North LaSalle Street
                                                     Suite 4000
                                                     Chicago, Illinois 60603
                                                     Attention of President


                                      -23-

<PAGE>



         with  separate  copies at such  address to the  Attention  of the Chief
         Financial Officer and the Corporate Secretary:
                           The Company at:           8410 W. Bryn Mawr
                                                     Suite 1100
                                                     Chicago, Illinois 60631
                                                     Attention of President

         with  separate  copies at such  address to the  Attention  of the Chief
         Financial Officer and the Corporate  Secretary or to such other address
         as any party  may,  from time to time,  designate  in a written  notice
         given in a like manner.  Any notice given under this Agreement shall be
         deemed delivered when received at the appropriate address.

                  (c) The Company  agrees to  reimburse  TDS upon demand for all
         reasonable out-of-pocket expenses (including reasonable attorney's fees
         and legal expenses) incurred by TDS in enforcing the obligations of the
         Company  hereunder  or under any Note and to pay, and save TDS harmless
         from all  liability  for, any stamp or other taxes which may be payable
         with  respect to the  execution  or delivery of this  Revolving  Credit
         Agreement  or the  issuance  of the  Notes,  which  obligations  of the
         Company  shall  survive  any  termination  of  this  Revolving   Credit
         Agreement.

                  (d) This Revolving  Credit  Agreement and each Note shall be a
         contract made under and governed by the laws of the State of Illinois.


                                      -24-

<PAGE>



                  (e) This Revolving  Credit Agreement shall be binding upon the
         Company and TDS and their respective  successors and assigns, and shall
         inure to the  benefit of the  Company  and TDS and the  successors  and
         assigns of TDS.

                  (f)  TDS  may  at  any  time  sell,  assign,  transfer,  grant
         participation  in, or  otherwise  dispose of all or any  portion of its
         loans or Notes or of its  Credit  or of its  right,  title or  interest
         therein  or  thereto  or in  or  to  this  Revolving  Credit  Agreement
         (collectively,  "Participation")  to any other Person  ("Participant").
         The Company agrees that any Participant may exercise any and all rights
         of  banker's  lien,  set-off  and  counterclaim  with  respect  to  its
         Participation  as fully as if such Participant were the maker of a loan
         in the  amount of its  Participation.  TDS shall be  released  from its
         obligations in connection  with any assignment of its rights  hereunder
         if such  obligations  are  expressly  assumed by the  assignee  of such
         rights.  TDS shall  promptly  furnish  the  Company  with notice of any
         assignment  or  Participation  hereunder,  specifying  in each case the
         identity of the  assignee or  Participant  and the amounts and terms of
         the assignment or Participation. Any provision of this Revolving Credit
         Agreement  may be amended,  modified or waived only by an instrument or
         instruments  in writing  and signed by the Chief  Executive  Officer or
         Chief Financial Officer of TDS and the Chief Executive Officer or Chief
         Financial Officer of the Company.


                                      -25-

<PAGE>



                  (g) This  Revolving  Credit  Agreement  may be executed in any
         number  of   counterparts   and  by   different   parties  in  separate
         counterparts.  Each  counterpart  shall be deemed an  original  and all
         counterparts taken together shall constitute one instrument.

                  (h)  All  representations,  warranties  and  covenants  of the
         parties shall  survive the delivery of the Notes and the  furnishing of
         the Credit and shall  expire  upon the  termination  of this  Revolving
         Credit Agreement.

                  (i) If any  provision of this  Revolving  Credit  Agreement is
         held prohibited,  invalid or  unenforceable  under applicable law, such
         provision shall be ineffective  only to the extent of such  prohibition
         or invalidity,  without invalidating the remainder of such provision or
         the remaining  provisions  of this  Revolving  Credit  Agreement or the
         Notes.

                  (j)  Subject to the  provisions  hereof,  TDS and the  Company
         shall  each  make,   execute,   acknowledge   and  deliver  such  other
         instruments  and  documents,  and take all such other actions as may be
         reasonably  required  in  order  to  effectuate  the  purposes  of this
         Revolving   Credit   Agreement  and  to  consummate  the   transactions
         contemplated  hereby.  Subject to the  provisions  hereof,  TDS and the
         Company  shall each, in  connection  with entering into this  Revolving
         Credit Agreement,  performing its obligations  hereunder and taking any
         and all  actions  relating  hereto,  comply with all  applicable  laws,
         regulations,  order and  decrees,  obtain  all  required  consents  and
         approvals and make all required filings with any  governmental  agency,
         other regulatory or administrative agency, commission or similar

                                      -26-

<PAGE>



         authority and promptly  provide the other with all such  information as
         the other may reasonably request in order to be able to comply with the
         provisions of this sentence.

                  (k) Nothing in this Revolving  Credit  Agreement  expressed or
         implied  is  intended  or shall be  construed  to  confer  any right or
         benefit  upon any  Person  other  than TDS and the  Company  and  their
         respective permitted successors and assigns.

                  (l) Subject to any contrary  requirement  of law and the right
         of each party to enforce its rights hereunder in any legal action, each
         party shall keep  strictly  confidential  and shall cause its employees
         and agents to keep strictly  confidential,  any information which it or
         any of its  agents or  employees  may  acquire  pursuant  to, or in the
         course of  performing  its  obligations  under,  any  provision of this
         Revolving Credit Agreement;  provided, however, that such obligation to
         maintain  confidentiality  shall not apply to information  which (x) at
         the time of disclosure was in the public domain not as a result of acts
         by the receiving  party,  or (y) was in the possession of the receiving
         party at the time of disclosure.

                  (m)  This  Revolving  Credit  Agreement  contains  the  entire
         understanding   of  the  parties  with  respect  to  the   transactions
         contemplated hereby.

                  (n) Descriptive  headings are for  convenience  only and shall
         not control or affect the meaning or  construction  of any provision of
         this Revolving Credit Agreement.
                                    * * * * *

                                      -27-

<PAGE>



                  IN WITNESS  WHEREOF,  the parties have executed this Revolving
Credit  Agreement  in  Chicago,  Illinois,  as of the day and year  first  above
written.

                                            TELEPHONE DATA AND SYSTEMS, INC.



                                            By:   /s/ LeRoy T. Carlson, Jr.
                                                  -----------------------------
                                                  LeRoy T. Carlson, Jr.
                                                  President & CEO


                                            AERIAL OPERATING CO., INC.



                                            By    /s/ Donald W. Warkentin
                                                  ------------------------------
                                                  Donald W. Warkentin
                                                  President


















                  Signature Page of Revolving Credit Agreement
                           dated as of August 31, 1998

                                      -28-

<PAGE>


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