Document:

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                                                                    EXHIBIT 10.1

                                                                  EXECUTION COPY

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                               INVESTOR AGREEMENT

                         DATED AS OF SEPTEMBER 17, 1999

                                  BY AND AMONG

                                   SONERA LTD.
                      A FINNISH LIMITED LIABILITY COMPANY,

                        VOICESTREAM WIRELESS CORPORATION,
                            A WASHINGTON CORPORATION

                                       AND

                    VOICESTREAM WIRELESS HOLDING CORPORATION,
                             A DELAWARE CORPORATION.

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                               INVESTOR AGREEMENT

        This INVESTOR AGREEMENT (this "AGREEMENT") is made as of September 17,
1999 by and between Sonera Ltd., a limited liability company organized under the
Laws of the Republic of Finland ("Sonera"), VoiceStream Wireless Corporation, a
Washington corporation ("VOICESTREAM"), and VoiceStream Wireless Holding
Corporation, a Delaware corporation (the "COMPANY").

        WHEREAS, Aerial Communications, Inc, a Delaware corporation ("AERIAL"),
Telephone and Data Systems, Inc. ("TDS"), VoiceStream, the Company and
VoiceStream Subsidiary III Corporation, a Delaware corporation and wholly owned
subsidiary of the Company ("SUB"), have entered into an Agreement and Plan of
Reorganization, dated as of September 17, 1999 (the "AERIAL REORGANIZATION
AGREEMENT"), pursuant to which Sub will be merged into Aerial.

        WHEREAS, VoiceStream, the Company and Omnipoint Corporation, a Delaware
corporation ("Omnipoint"), have entered into an Agreement and Plan of
Reorganization, dated June 23, 1999 (the "Omnipoint Reorganization Agreement"),
whereby, among other things, a subsidiary of the Company will merge with and
into Omnipoint (the "Omnipoint Reorganization").

        WHEREAS, the Investor and the Company wish to set forth certain
agreements concerning the ownership and transfer of shares of Common Stock, and
certain other matters as provided herein.

        NOW, THEREFORE, in consideration of the mutual and dependent promises
set forth herein, the Investor hereby agrees with the Company, and the Company
hereby agrees with the Investor, as follows:

1. EFFECTIVE DATE OF AGREEMENT AND OTHER MATTERS.

        (a) This Agreement shall become effective at the earlier of (i) the
Effective Time pursuant to and as defined in the Omnipoint Reorganization
Agreement, or (ii) the Effective Time pursuant to and as defined in the Aerial
Reorganization Agreement.

        (b) All representations, warranties and covenants made by either
VoiceStream or the Company are hereby made on a joint and several basis by
VoiceStream and the Company.

2. DEFINITIONS.

        (a) Unless the context requires otherwise, capitalized terms used but
not defined in this Agreement have the meanings given in the Aerial
Reorganization Agreement.

        (b) As used in this Agreement, the following terms have the respective
meanings set forth below (applicable to both the singular and plural forms of
such terms):

        "AFFILIATE" shall have the meaning set forth in Rule 12b-2 of the rules
and regulations promulgated under the Exchange Act; provided, however, that for
purposes of Section 3 of this

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Agreement, none of the following shall be deemed to be an Affiliate of the
Investor: (A)(i) the Company, (ii) the Cook Inlet Parties, or (iii) any of the
Current Principal Stockholders or their Affiliates, or (B) any Person who would
be an Affiliate of Investor solely because such Person is an Affiliate of any of
the Persons referred to in clause (A) of this provision.

        "AGREEMENT" means this Investor Agreement, as amended, modified,
supplemented or restated from time to time in accordance with the terms hereof.

        "BANKRUPTCY EVENT" means the filing by the Company or VoiceStream of a
petition in bankruptcy or the expiration of sixty (60) days after a petition in
bankruptcy shall have been filed against the Company or VoiceStream and such
petition shall not have been stayed or discharged during such sixty (60) day
period; or upon the expiration of sixty (60) days after the commencement of any
proceeding under any law for the relief of debtors seeking the relief or
readjustment of the Company's or VoiceStream's indebtedness either through
reorganization, winding-up, extension or otherwise, and such proceedings
involving the Company or VoiceStream as debtor shall not have been vacated or
stayed within such sixty (60) day period; or upon the appointment of a receiver,
custodian or trustee for all or substantially all of the Company's or
VoiceStream's property, or the making by the Company or VoiceStream of any
general assignment for the benefit of creditors, or the admitting in writing by
the Company or VoiceStream of its inability to pay its debts as they mature; or
upon the voluntary or involuntary liquidation or dissolution of the Company or
VoiceStream, other than the liquidation or dissolution of VoiceStream with or
into the Company or another wholly-owned subsidiary of the Company.

        "BENEFICIALLY OWNED" and "BENEFICIAL OWNERSHIP" have the meaning set
forth in Rule 13d-3 of the rules and regulations promulgated under the Exchange
Act, excluding paragraph (d) of such Rule relating to the deemed beneficial
ownership of a security if such person has the right to acquire such security
within sixty (60) days.

        "BOARD" means the board of directors of the Company.

        "CHANGE OF CONTROL" means the acquisition by any Person or 13D Group of
direct or indirect Beneficial Ownership of Voting Securities representing 50% or
more of the Voting Power, pursuant to (i) an acquisition of Common Stock, (ii)
any merger, consolidation or business combination involving the Company or any
material portion of its business, or (iii) a recapitalization, restructuring,
liquidation, dissolution or similar extraordinary transaction relating to the
Company or any material portion of its business; provided, that the foregoing
shall not be deemed to constitute a Change of Control if immediately after such
transaction or event Persons who were stockholders of the Company immediately
prior to such transaction or event continue to Beneficially Own on a
proportionate basis Voting Securities which represent more than fifty percent
(50%) of the Voting Power of the surviving or resulting entity immediately after
such transaction or event; provided further, that, notwithstanding the
foregoing, a Change of Control shall be deemed to occur if any one of the
Current Principal Stockholders shall Beneficially Own fifty percent (50%) or
more of the Voting Power.

        "COMMISSION" means the United States Securities and Exchange Commission.

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        "COMMON STOCK" means the Company's Common Stock, $0.001, and shall
include any new, substituted and additional securities issued at any time in
replacement of the Common Stock or issued or delivered with respect to the
Common Stock.

        "COMPANY" means VoiceStream Wireless Holding Corporation, a Delaware
corporation, and its successors and assigns.

        "COOK INLET PARTIES" means (i) Cook Inlet Western Wireless PV/SS PCS,
L.P., (ii) Cook Inlet VoiceStream PCS, LLC, (iii) Cook Inlet VoiceStream II,
LLC, (iv) Cook Inlet VoiceStream III, LLC and any similar joint venture in which
the Company, Omnipoint, VoiceStream or their Subsidiaries from time to time are
significant equity owners.

        "CURRENT PRINCIPAL STOCKHOLDERS" means the individuals and entities
listed on Schedule I and their Permitted Affiliated Transferees (as defined in
the Voting Agreement) and, with respect to Hutchinson USA, its Disqualified
Affiliates (as defined in the Hutchinson USA Investor Agreement).

        "DISINTERESTED BOARD APPROVAL" means the affirmative vote or written
consent of a majority of the Board (excluding Investor Directors) then in
office.

        "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended.

        "IMPUTED COST OF FUNDS" means LIBOR plus 275 basis points.

        "INCREMENTAL SHARES" has the meaning given in Section 3(c)(i).

        "INVESTOR" unless otherwise specified herein, means Sonera and its
successors and assigns and Affiliates which from time to time hold shares of
Voting Securities.

        "INVESTOR DIRECTOR" means any member of the Board who has been
designated by Investor or any member of the Investor Group for nomination or
appointment as a director of the Company.

        "INVESTOR GROUP" means Investor and any of their respective Affiliates.

        "INVESTOR'S OWNERSHIP PERCENTAGE" means the percentage determined by
dividing the shares of Common Stock Beneficially Owned by the Investor Group by
the Voting Power of the Company both determined as of the same relevant date of
determination.

        "INVESTOR TENDER OFFER" means a bona fide public tender offer subject to
the provisions of Regulation 14D when first commenced within the meaning of Rule
14d-2(a) of the rules and regulations under the Exchange Act, by any of the
Investor Group (or any 13D Group that includes any of the Investor Group) to
purchase or exchange for cash or other consideration any Common Stock and which
consists of an offer to acquire one hundred percent (100%) of the outstanding
Common Stock (without regard to Common Stock owned by any of the Investor

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Group) and is conditioned (which condition may not be waived) on a majority of
the shares of outstanding Common Stock held by shareholders other than any of
the Investor Group being tendered and not withdrawn with respect to such offer.

        "HUTCHINSON USA" means Hutchinson Telecommunications PCS (USA) Limited,
a British Virgin Islands Corporation.

        "HUTCHINSON USA INVESTOR AGREEMENT" means the Investor Agreement dated
June 23, 1999 among Hutchinson USA, Hutchinson Telecommunications Limited and
the Company.

        "PERMITTED TRANSFEREE" means any entity in which Investor owns, directly
or indirectly, more than 40% of the outstanding voting power and of which
members of the Investor Group collectively are the largest shareholder.

        "PERSON" means an individual, partnership, joint-stock company,
corporation, trust or unincorporated organization, limited liability company, or
a government or agency or political subdivision thereof or any other entity.

        "QUALIFIED DESIGNEE" means an individual designated by Investor,
provided that the Company shall have the right to approve such designee, which
approval shall not be unreasonably withheld, so long as such individual's
membership on the Board shall not cause any violation of any Federal anti-trust
law or any other Federal or state law.

        "REORGANIZATION" has the meaning given in the Omnipoint Reorganization
Agreement.

        "SALE" means (i) a public offer and sale or other public distribution of
securities, including pursuant to an effective registration statement under the
Securities Act, or (ii) an offer or sale not involving a public offering
pursuant to an exemption from registration under Rules 144 or 145 or otherwise
under the Securities Act.

        "STANDSTILL PERIOD" has the meaning given in Section 3(a)(i).

        "STANDSTILL TERMINATION EVENT" means the date on which the first of the
following occurs: (i) the Investor Group Beneficially Owns, in the aggregate,
less than ten percent (10%) of the Voting Power, (ii) the Investor Group
Beneficially Owns, in the aggregate, more than 90% of the Voting Power, (iii) a
Change of Control or (iv) a Bankruptcy Event.

        "SUBSIDIARY" means, as to any Person, another Person which is an entity
as to which such Person owns more than fifty percent (50%) of the outstanding
voting power and more than fifty percent (50%) of the equity.

        "THIRD PARTY CHANGE OF CONTROL" has the meaning given in Section
3(a)(i)(C).

        "THIRD PARTY OFFER" has the meaning given in Section 3(a)(i)(C).

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        "THRESHOLD PERCENTAGE" means nineteen and nine tenths percent (19.9%);
provided that the Threshold Percentage shall be less to the extent necessary if
such ownership would cause a violation of the spectrum cap limits set by 47
C.F.R. Section 20.6 or other legislation or rule or that will require
divestiture by VoiceStream or the Company (including for this purpose the Cook
Inlet Parties) pursuant to said rule, as such rule may be modified or replaced
from time to time; provided that, in such event, upon the request of Investor,
VoiceStream and the Company shall use commercially reasonable efforts and
cooperate with the Investor Group to seek to obtain appropriate waivers from
such FCC rules or effect other commercially reasonable arrangements which would
permit the Investor Group to increase its ownership percentage to a maximum of
nineteen and nine tenths percent (19.9%). The Threshold Percentage shall be
calculated by dividing the Voting Power of the Voting Securities which are
Beneficially Owned by the Investor Group by the Voting Power as of the date of
determination.

        "TRANSFER" means any sale, assignment, pledge, hypothecation, or other
transfer, disposition or encumbrance of any interest (and includes an exchange
of shares in a merger, consolidation or similar transaction).

        "TRIGGERING PERSON" has the meaning given in Section 3(b)(i)(A).

        "VOTING AGREEMENT" means any voting or similar agreement to which any
member of the Investor Group and either or both of the Company or VoiceStream
are party from time to time which provides, among other things, for the voting
of securities for the election of directors of VoiceStream or the Company.

        "VOTING POWER" means, as of the date of determination, the total number
of votes which may be cast in the election of directors of the Company at any
meeting of shareholders of the Company if held on such date of determination if
all Voting Securities then outstanding were present and voted to the fullest
extent possible at such meeting. Voting Power shall be determined based on
information included in the Company's or VoiceStream's most recently filed Form
10-K or Form 10-Q notwithstanding subsequent changes thereto unless such changes
have been reported on a Form 8-K or reported to Investor in writing by the
Company or VoiceStream.

        "VOICESTREAM" means VoiceStream Wireless Corporation, a Washington
corporation.

        "VOTING SECURITY" means, as of the date of determination, the Common
Stock of the Company, any other security generally entitled to vote for the
election of directors.

        "13D GROUP" means any group of persons formed for the purpose of
acquiring, holding, voting or disposing of Voting Securities which would be
required under Section 13(d) of the Exchange Act, and the rules and regulations
promulgated thereunder, to file a statement on Schedule 13D or a Schedule 13G
with the Commission as a "person" within the meaning of Section 13(d)(3) of the
Exchange Act if such group Beneficially Owned (as defined without excluding
paragraph (d) of Rule 13d-3) sufficient securities to require such a filing
under the Exchange Act. When references herein are to a group under Section
13(d) and not to members of such group, such references shall be deemed to refer
to actions of the group acting as such group

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and not to the individual actions of any members of such group, unless and to
the extent such actions would not be permitted to be taken by the group.

        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,"
"hereunder" 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.

3. STANDSTILL.

        (a) STANDSTILL OBLIGATIONS.

                  (i) LIMITATION. Unless there shall have occurred a Standstill
Termination Event, until the fifth (5th) anniversary of the date of this
Agreement (the "STANDSTILL PERIOD"), except with Disinterested Board Approval,
no member of the Investor Group shall, directly or indirectly,

                (A) acquire or agree to acquire any Voting Securities (except by
        way of stock splits, stock dividends or other distributions) if, in any
        such case, the effect of such acquisition would be to increase the
        Investor's Ownership Percentage to more than the Threshold Percentage;

                (B) solicit proxies with respect to the Voting Securities or
        become a "PARTICIPANT" in any "ELECTION CONTEST" (as such terms are used
        in Rule 14(a)-11 of Regulation 14A promulgated under the Exchange Act)
        relating to the election of directors of the Company, it being
        understood that the Investor Group shall not be deemed to be such a
        participant merely by reason of the membership of any Investor Directors
        on the Board pursuant to the terms of any Voting Agreement; provided,
        that if VoiceStream or the Company shall be in breach under any Voting
        Agreement (which breach, in the reasonable judgment of Investor, could
        likely result in an Investor Director not being elected in accordance
        with the terms of the Voting Agreement), the Investor Group may engage
        in such activities for the limited purpose of electing the Investor
        Directors; or

                (C) join a 13D Group (other than a 13D Group which includes all
        of the Current Principal Stockholders) with any Person which is not a
        member of the Investor Group or otherwise induce, attempt to induce or
        in any manner act in concert with any such Person for the purpose of
        initiating or effectuating a tender offer or exchange offer for any
        Voting Securities (a "THIRD PARTY OFFER") or a transaction which would
        result in a Change of Control (a "THIRD PARTY CHANGE OF CONTROL");
        provided that the provisions of this clause (C) shall not be applicable
        if any Current Principal Stockholder holding more than 5% of the Voting
        Power shall have engaged in any material respect in any of the
        activities referred to in this clause (C).

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                (D) either alone or through or with any Person initiate, induce,
        attempt to induce or in any manner act in concert with or otherwise
        support, encourage or act in concert with, any such Person for the
        purpose of initiating or effectuating a tender or exchange offer or
        Change of Control; or

                (E) disclose to any Person any intention, plan or arrangement
        inconsistent with the foregoing.

        Nothing in this Section 3(a)(i) shall have the effect of (i) precluding
a member of the Investor Group from participating in a Third Party Offer or
voting or agreeing to vote its shares in favor of a Third Party Change of
Control in which the Investor Group would receive consideration on the same
basis as is generally available to other holders of Common Stock or (ii)
prohibiting any Investor Director (acting in such capacity) from participating
(A) in discussions with other members of the Board or (B) in meetings of the
Board.

        If any member of the Investor Group makes such an acquisition or
exercise that would increase the percentage interest of the Investor Group in
the Voting Power to more than the Threshold Percentage, such excess shares shall
(for so long as the Voting Power exceeds the Threshold Percentage) be voted in a
manner proportionate to shares voted by the shareholders of the Company other
than the Investor Group and the Permitted Transferees; provided, that if the
excess shares shall result from the bad faith actions of the Investor Group or
its Affiliates, it shall promptly divest such excess; provided, further,
however, that no member of the Investor Group shall be obligated to divest
itself of such excess pursuant to this Section 3(a)(i) until such time as such
divestment would not subject such member of the Investment Group to liability
under Section 16(b) of the Exchange Act or any other applicable provision of
Federal or state law.

                  (ii) RECAPITALIZATIONS, ETC. Notwithstanding Section 3(a)(i),
no member of the Investor Group shall be obligated to dispose of any Voting
Securities if the aggregate percentage ownership of the Investor Group is
increased as a result of (x) a recapitalization, merger, consolidation or other
reorganization of the Company, (y) a repurchase of Voting Securities by the
Company or (z) any other action taken by the Company or its Affiliates other
than the Investor Group.

                  (iii) REINSTATEMENT OF STANDSTILL. If a Standstill Termination
Event shall have occurred by virtue of the Investor Group Beneficially Owning
less than ten percent (10%) of the Voting Power and thereafter the Investor
Group shall Beneficially Own more than ten percent (10%) of the Voting Power
(other than as a result of (x) a recapitalization, merger, consolidation or
other reorganization of the Company, (y) a repurchase of Voting Securities by
the Company or (z) any other action taken by the Company or its Affiliates other
than the Investor Group), the provisions of this Section 3 shall be deemed to
have been reinstated.

        (b) EXCEPTION FOR CERTAIN THIRD-PARTY ACQUISITIONS.

                  (i) EXCEPTION TO STANDSTILL OBLIGATION. Notwithstanding
Section 3(a)(i), the Investor Group may:

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                (A) acquire Voting Securities without regard to the limitations
        set forth above but in accordance with Section 3(b)(ii) if at any time
        any person or 13D Group of persons, (other than any 13D Group which
        includes Investor or any of its Affiliates) (such person or persons
        together with any of their Affiliates, collectively, a "TRIGGERING
        Person"), directly or indirectly, (x) makes a bona fide offer to
        acquire, or (y) acquires, Beneficial Ownership of Voting Securities
        which, if added to the Voting Securities (if any) already Beneficially
        Owned by such Triggering Person, would represent ownership of Voting
        Securities greater than the Threshold Percentage or, in the event the
        Triggering Person is Hutchinson USA, greater than the "Threshold
        Percentage" specified in the Hutchinson USA Investor Agreement, which is
        applicable at such time;

                (B) with Disinterested Board Approval, make an Investor Tender
        Offer during the Standstill Period; and

                (C) with Disinterested Board Approval, acquire Voting Securities
        (including stock options, warrants or rights to purchase Voting
        Securities) without regard to the limitations set forth above.

The Company shall give Investor written notice of the occurrence of any event of
the type referred to in clause (A) promptly after it obtains knowledge of such
event.

                  (ii) COMPETING OFFERS. If an event identified in Section
3(b)(i)(A) occurs and shall not have been withdrawn or terminated, the Investor
Group shall be permitted to take such action and make such offers as may be
considered to be of the same nature and type of action or offer and for the same
resulting number of shares as that which is being taken by the Triggering
Person; provided that the Investor Group may only acquire that number of shares
which when added to the number of shares already owned by the Investor Group
shall not exceed the number of shares Beneficially Owned (as defined without
excluding paragraph (d) of Rule 13d-3) and to be acquired (assuming any
proposals or offers to purchase have been consummated) by the Triggering Person.
In proceeding with any action or offer permitted under this Section 3(b)(ii),
the Investor Group shall be permitted to offer more favorable terms such as
price, cash versus securities or other such terms as may be consistent with an
offer of the same nature and type of consideration as that which is being
proposed by the Triggering Person.

                  (iii) NO CONTESTING. If the Investor Group shall take any such
action permitted by this Section 3(b), the Company agrees that it shall not in
any way (whether by active opposition, Board announcement or otherwise) contest
such action, subject in all events to the fiduciary obligations of the Company's
Board and officers to the Company's stockholders.

        (c) OPTION TO PURCHASE INCREMENTAL SHARES.

                  (i) INCREMENTAL SHARES. If an event identified in Section
3(b)(i) occurs and as a result the Investor Group acquires Voting Securities
which increase the Investor Group's percentage interest in the Voting Power to
more than the Threshold Percentage (the "INCREMENTAL SHARES"), and thereafter
the Triggering Person holds Voting Securities representing a percentage of the
Voting Power less than the Threshold Percentage, then, upon the

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expiration of the Investor Group's right to dispose of the Incremental Shares as
provided in Section 3(c)(ii) below, the Investor Group hereby grants to the
Company or a designee selected with Disinterested Board Approval, for a period
of ninety (90) days (subject to extension in the event of Investor's exercise of
rights under Section 3(c)(ii) below), an option to acquire any Incremental
Shares at a price equal to the price paid by the Investor Group for such shares,
plus such expenses and costs reasonably necessary to acquire the Incremental
Shares and incurred by the Investor Group in acquiring the Incremental Shares
(including the Imputed Cost of Funds of the Investor Group of holding the
Incremental Shares until acquired by the Company or such designee); provided,
however, that the Investor Group shall not be obligated to sell any Voting
Securities pursuant to this Section 3(c)(i) until such time as such sale would
not subject the Investor Group to liability under Section 16(b) of the Exchange
Act or any other applicable provision of Federal or state law.

                  (ii) DISPOSITION. In the event that the Investor Group has
acquired Incremental Shares from a seller or sellers other than the Company, for
a period of sixty (60) days from the date on which the Investor Group holds
Incremental Shares, the Investor Group shall have the right to sell such
Incremental Shares as follows: (x) to an independent third party in a bona fide
transaction or transactions; (y) if Rule 144 is available, into the public
market in accordance with the terms of Rule 144; or (z) as provided under both
(x) and (y). In the event that the Investor Group elects to dispose of the
Incremental Shares as provided in this Section 3(c)(ii), Investor shall provide
written notice to the Company of such disposition and the purchase option
granted to the Company pursuant to Section 3(c)(i) shall apply only to those
Incremental Shares which have not been so disposed of; provided, however, that
the Investor Group shall not be obligated to sell any Voting Securities pursuant
to this Section 3(c)(ii) until such time as such sale would not subject the
Investor Group to liability under Section 16(b) of the Exchange Act or any other
applicable provision of Federal or state law.

                  (iii) ADJUSTMENT FOR FAILURE TO EXERCISE OPTION. In the event
that the Company or its designee fails to exercise its option as provided in
Section 3(c)(i), the Threshold Percentage shall be increased to a percentage
equal to the percentage of the Voting Power held by the Investor Group upon the
expiration of the right to exercise such option by the Company or such designee.

                  (iv) VOTING OF INCREMENTAL SHARES. Until the Incremental
Shares shall have been disposed of as provided in Section 3(c)(ii) and, if
applicable, the option of the Company or its designee provided in Section
3(c)(i) shall have expired, the Incremental Shares shall be voted in a manner
proportionate to shares voted by the shareholders of the Company other than the
Investor Group and the Permitted Transferees.

                  (v) NO CIRCUMVENTION. (a) The Investor Group shall not attempt
to circumvent the provisions of this Section 3(c) by taking any action that
would have the effect of extending the periods for which Section 16(b) liability
would apply.

                  (b) The Investor Group shall not acquire or agree to acquire
any Voting Securities of, or other equity interest in, the Cook Inlet Parties
except as a member of a 13D Group which includes all of the Current Principal
Stockholders.

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4. TRANSFER.

        (a) The Voting Securities Beneficially Owned by the Investor Group shall
be freely tradable and may be Transferred by the Investor Group in Sales as
provided herein or in the Registration Rights Agreement, provided that the
Investor Group takes reasonable care in approving a plan of distribution for
sales of Common Stock pursuant to a registration statement or authorizing sales
pursuant to Rules 144 or 145 or otherwise to preclude the acquisition of more
than five percent (5%) of the Voting Power by any Person, Affiliate or 13D Group
(other than the Current Principal Stockholders and their Permitted Affiliate
Transferees (as defined in the Voting Agreement) and, with respect to Hutchinson
USA, the Disqualified Affiliates (as defined in the Hutchinson USA Investor
Agreement) unless otherwise approved by Disinterested Board Approval. Any Sale
not made pursuant to a registration statement as permitted by the Registration
Rights Agreement shall be made in compliance with Rule 144 and/or 145 or
pursuant to another exemption from registration.

        (b) Provided that it shall have provided prior written notice to the
Company, the Investor Group and the Permitted Transferees shall have the
unrestricted right to Transfer their Voting Securities and the rights and
obligations hereunder to members of the Investor Group and the Permitted
Transferees (provided that any such transferees agree in writing to be bound by
the terms of this Agreement).

        (c) Nothing herein shall restrict in any way the Transfer of any
derivative security with respect to the Voting Securities Beneficially Owned by
the Investor Group and the Permitted Transferees.

5. COVENANTS OF THE INVESTOR.

        Until the termination of the Aerial Reorganization Agreement in
accordance with the terms thereof, Investor agrees as follows:

        (a) At any stockholders meeting of Aerial (or at any adjournment
thereof) or in any other circumstances upon which a vote, consent or other
approval with respect to the Aerial Reorganization or the Aerial Reorganization
Agreement is sought, the Investor shall vote (or cause to be voted) the shares
of Aerial Common Stock owned by it or its Affiliates in favor of the Aerial
Reorganization, the approval and adoption of the Aerial Reorganization Agreement
and the approval of the terms thereof and each of the other transactions
contemplated by the Aerial Reorganization Agreement.

        (b) At any meeting of stockholders of Aerial (or at any adjournment
thereof) or in any other circumstances upon which a vote, consent or other
approval is sought, other than with respect to the Aerial Reorganization or
Aerial Reorganization Agreement, the Investor shall vote (or cause to be voted)
the shares of Aerial Common Stock owned by it or its Affiliates against any
merger agreement or merger, consolidation, sale of all or substantially all of
the assets of Aerial, or reorganization, recapitalization, dissolution,
liquidation or winding up of or by Aerial or any

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Subsidiary of Aerial or any other Acquisition Proposal. The Investor further
agrees not to commit or agree to take any action inconsistent with the
foregoing.

        (c) The Investor agrees not to (i) sell transfer, pledge, encumber,
assign or otherwise dispose of (including by gift) (collectively, "Transfer"),
or enter into any contract, option or other arrangement (including any
profit-sharing arrangement) with respect to any Transfer of the shares of Aerial
Common Stock owned by it or its Affiliates to any person or (ii) enter into any
voting arrangement, whether by proxy, voting agreement or otherwise
(collectively, "Voting Agreement"), in relation to the shares of Aerial Common
Stock owned by it or its Affiliates, and agrees not to commit or agree to take
any of the foregoing actions. Notwithstanding the foregoing, the Investor may
make Transfers to Permitted Transferees.

        (d) The Investor shall not, nor shall the Investor authorize any
affiliate, director, officer, employee, investment banker, attorney or other
advisor or representative of the Investor to, (i) directly or indirectly
solicit, initiate or encourage the submission of, any Acquisition Proposal or,
(ii) directly or indirectly participate in any discussions or negotiations
regarding, or furnish to any person any information with respect to, or take any
other action to facilitate any inquiries or the making of any proposal that
constitutes or may reasonably be expected to lead to, any Acquisition Proposal
or (iii) directly or indirectly take or participate in any actions set forth in
Section 5.3 of the Aerial Reorganization Agreement.

        (e) The Investor shall use all reasonable efforts to take, or cause to
be taken, all actions, and to do, or cause to be done, and to assist and
cooperate in doing, all things necessary, proper or advisable to consummate and
make effective, in the most expeditious manner practicable, the Aerial
Reorganization and the other transactions contemplated by the Aerial
Reorganization Agreement.

        (f) Investor hereby irrevocable waives any rights of appraisal or rights
to dissent from the Aerial Reorganization that Investor may have.

        (g) Sonera agrees to execute at the closing of the Omnipoint
Reorganization and again at the closing of the Aerial Reorganization a tax
certificate in the form attached hereto.

6. VOTING AGREEMENT AND DIRECTOR DESIGNEES.

        (a) Certain Stockholders of VoiceStream ("Parent Stockholders") are
parties to a Voting Agreement, dated May 3, 1999 ("VoiceStream Voting
Agreement"), pursuant to which each Parent Stockholder agreed on the terms set
forth in the VoiceStream Voting Agreement to vote the shares of VoiceStream
Common Stock Beneficially Owned by it at the time of a vote in favor of
directors designated by such Parent Stockholders. On June 23, 1999 the Parent
Stockholders entered into an Agreement (the "Omnipoint Voting Agreement") with
certain stockholders of Omnipoint (the "Omnipoint Stockholders") in which they
agreed, among other things, to terminate the VoiceStream Voting Agreement and
enter into a new Voting Agreement

                                     - 11 -
<PAGE>   13

on terms mutually satisfactory to Omnipoint Stockholders and Parent Stockholders
("Newco Voting Agreement") which will set forth voting arrangements which will
apply to the Company after the Omnipoint Reorganization. The Parent Stockholders
and Investor hereby agree to enter into a voting agreement ("Newco Voting
Agreement II") effective on the Effective Time of the Omnipoint Reorganization
on terms mutually satisfactory to the Parent Stockholders and Investor, pursuant
to which (w) the voting arrangements which existed under the VoiceStream Voting
Agreement will apply to the Company, (x) the provisions of Section 6 (b) below
shall also be effectuated, (y) the provisions of the letter agreement, dated
June 23, 1999 ("Hutchinson Letter"), with Hutchinson will be effectuated, and
(z) upon consummation of the Omnipoint Reorganization, the provisions of Section
7.4 of the Omnipoint Agreement shall be effectuated. On September 17, 1999,
Parent Stockholders, Aerial, TDS, VoiceStream and the Company entered into a
Parent Stockholders Agreement, whereby, among other things, Parent Stockholders
and TDS agreed, effective on the Effective Time of the Aerial Reorganization, to
enter into a voting agreement substantially similar to that contemplated hereby
pursuant to which, in addition to the provisions referred in clauses (w), (y)
and (z) above, the Principal Stockholders and TDS agreed to vote for one
director designated by TDS. The Parent Stockholders and Investor shall use
reasonable efforts to seek to have the Omnipoint Stockholders enter into Newco
Voting Agreement II, effective on the Effective Time of the Omnipoint
Reorganization, on terms mutually satisfactory to the Parent Stockholders,
Investor and the Omnipoint Stockholders. If the Omnipoint Stockholders do not
enter into Newco Voting Agreement II effective at the Effective Time of the
Omnipoint Reorganization, the Parent Stockholder and Investor shall enter into
Newco Voting Agreement II effective at the Effective Time of the Omnipoint
Reorganization, it being understood and agreed that the Parent Stockholders and
the Omnipoint Stockholders will still enter into the Newco Voting Agreement. The
Parent Stockholders and Investor shall use reasonable efforts to seek to have
TDS enter into Newco Voting Agreement II, effective on the Effective Time of the
Aerial Reorganization, on terms mutually satisfactory to the Parent
Stockholders, Investor and TDS. If TDS does not enter into Newco Voting
Agreement II effective at the Effective Time of the Aerial Reorganization, the
Parent Stockholder and Investor shall enter into Newco Voting Agreement II
effective at the Effective Time of the Omnipoint Reorganization, it being
understood and agreed that the Parent Stockholders and TDS will still enter into
an appropriate voting agreement

        (b) Pursuant to Newco Voting Agreement II each of the Parent
Stockholders and Investor (and the Omnipoint Stockholders if they agree to enter
into such agreement) shall agree, on the terms set forth therein, to vote, or
cause to be voted, all of the shares of Parent Common Stock Beneficially Owned
by it at the time of the vote in person or by proxy (and shall take all other
necessary or desirable action within the Investor's or such Parent Stockholder's
control including attendance at meetings in person or by proxy for purposes of
obtaining a quorum and execution of written consents in lieu of meetings), for
the election and continuation in office of (i) one (1) Qualified Designee as a
director of the Company so long as the Investor Beneficially Owns at least
4,500,000 shares of Parent Common Stock; provided, however, if Investor owns
more than 9,800,000 shares of Parent Common Stock and TDS owns less than
4,500,000 shares of Parent Common Stock, Investor shall be permitted to
designate two (2) Qualified Designees; and (ii) the directors designated by the
Parent Stockholders pursuant to the VoiceStream Voting Agreement (as restated in
Newco Voting Agreement II), the Hutchinson Letter and Section 7.4 of the
Omnipoint Agreement.

                                     - 12 -
<PAGE>   14

        (c) Parent agrees if necessary, to amend the Bylaws of Parent, to
increase the number of authorized directors to a number sufficient to satisfy
the obligations in the VoiceStream Voting Agreement, Newco Voting Agreement and
Newco Voting Agreement II, as applicable.

7. MISCELLANEOUS.

        (a) WAIVER; AMENDMENTS. Except as expressly provided otherwise herein,
neither this Agreement nor any provision hereof may be changed, waived,
discharged or terminated orally, but only by an instrument in writing signed by
the Company and the Investor.

        (b) RECAPITALIZATION, EXCHANGES, ETC. The provisions of this Agreement
shall apply to the full extent set forth herein with respect to shares or other
securities of the Company that may be issued to the Investor in respect of, in
exchange for, or in substitution of the Common Stock.

        (c) SPECIFIC PERFORMANCE. Each of the parties hereto acknowledges and
agrees that, in the event of any breach of this Agreement, the non-breaching
parties would be irreparably harmed and could not be made whole by monetary
damages. Accordingly, each party hereto agrees that the other party, in addition
to any other remedy to which they may be entitled at law or in equity, shall be
entitled to compel specific performance of this Agreement.

        (d) NOTICES. All notices, requests, demands and other communications
hereunder shall be in writing and, except to the extent otherwise expressly
provided in this Agreement, shall be deemed to have been duly given if delivered
by same day or next day courier (guaranteed delivery) or mailed, registered
mail, return receipt requested, or transmitted by telegram, telex or facsimile
(i) if to the Investor, at the Investor's address appearing below or at any
other address the Investor may have provided in writing to the Company and (ii)
if to the Company, at 3650 131st Avenue S.E., Suite 400, Bellevue, WA 98006,
U.S.A., Tel: (425) 586-8014, Fax: (425) 586-8080; Attention: General Counsel, or
such other address as the Company may have furnished to the Investor in writing,
with copies (which shall not constitute notice) to Preston Gates & Ellis LLP,
5000 Columbia Center, 701 Fifth Avenue, Seattle, WA 98104, Attention: Richard B.
Dodd, Esq., Facsimile No.: (206) 623-7022 and to Friedman Kaplan & Seiler LLP,
875 Third Avenue New York, NY 10022 Attention: Barry A. Adelman, Esq. Facsimile
No.: (212) 355-6401. If a notice hereunder is transmitted by confirmed fax so as
to arrive during normal business hours during a Business Day at the place of
receipt, then such notice shall be deemed to have been given on such Business
Day at the place of receipt or, if so transmitted to arrive after normal
business hours during a Business Day at the place of receipt, then such notice
shall be deemed to have been given on the following Business Day at the place of
receipt. If such notice is sent by next-day courier it shall be deemed to have
been given on the next Business Day at the place of receipt following sending
and, if by registered mail, on the fifth Business Day at the place of receipt
following sending, provided, that the date of sending shall be deemed to be the
date at the place of receipt at the time such notice is posted.

                                     - 13 -
<PAGE>   15

The Investor Group:

                             Sonera Ltd.
                             P.O. Box, Fin - 00051 - Tele
                             Teollisuuskatu 15
                             Helsinki, Finland
                             Attention:  Maire Laitinen, Esq.
                             Facsimile No.: 011-358-2040-3414

                      with a copy to:

                             Patton Boggs LLP
                             2550 M. St. N.W.
                             Washington, D.C.  20037
                             Attention: Richard M. Stolbach, Esq.
                             Facsimile No.:  (202) 457-6315

        (f) SUCCESSORS AND ASSIGNS. Except as otherwise provided herein, this
Agreement shall inure to the benefit of, and be binding upon, the successors and
assigns of each of the parties; provided, however, that this Agreement may not
be assigned by any party hereto other than in compliance with the terms hereof.

        (g) COUNTERPARTS. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original and all of which
together shall be considered one and the same agreement.

        (h) ENTIRE AGREEMENT. This Agreement constitutes the entire
understanding of the parties hereto with respect to the subject matter hereof
and supersedes all prior understandings among such parties with respect to such
subject matter.

        (i) APPLICABLE LAW. The validity of this Agreement, its construction,
interpretation and enforcement, and the rights of the parties hereunder, shall
be determined under, governed by and construed in accordance with the internal
laws of the State of Delaware applicable to contracts formed in such State. Each
party hereto agrees that any suit, action or other proceeding arising out of
this Agreement shall be brought and litigated in the courts of the State of
Delaware or the United States District Court for the District of Delaware and
each party hereto hereby irrevocably consents to exclusive personal jurisdiction
and venue in any such court and hereby waives any claim it may have that such
court is an inconvenient forum for the purposes of any such suit, action or
other proceeding.

        (j) SECTION HEADINGS. The headings of the sections and subsections of
this Agreement are inserted for convenience only and shall not be deemed to
constitute a part thereof.

        (k) FAILURE TO PURSUE REMEDIES. The failure of any party to seek redress
for violation of, or to insist upon the strict performance of, any provision of
this Agreement shall not

                                     - 14 -
<PAGE>   16

prevent a subsequent act, which would have originally constituted a violation,
from having the effect of an original violation.

        (l) CUMULATIVE REMEDIES. The rights and remedies provided by this
Agreement are cumulative and the use of any one right or remedy by any party
shall not preclude or waive its right to use any or all other remedies except as
otherwise expressly provided in this Agreement. Such rights and remedies are
given in addition to any other rights the parties may have by law, statute,
ordinance or otherwise.

        (m) SEVERABILITY. The invalidity or unenforceability of any particular
provision of this Agreement shall not affect the other provisions hereof, and
this Agreement shall be construed in all respects as if such invalid or
unenforceable provision were omitted.

            [The remainder of this page was intentionally left blank]

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

                             SONERA LTD.

                             ---------------------------------
                             Name:
                             Title:

                             VOICESTREAM WIRELESS CORPORATION

                             ----------------------------------
                             Name:
                             Title:

                             VOICESTREAM WIRELESS HOLDING
                             CORPORATION

                             ----------------------------------
                             Name:
                             Title:

                                     - 15 -
<PAGE>   17

                                   SCHEDULE I

                         CURRENT PRINCIPAL STOCKHOLDERS

NAME AND ADDRESS OF STOCKHOLDER

Hellman & Friedman Capital Partners II, L.P.
c/o Hellman & Friedman LLC
One Maritime Plaza, Suite 1200
San Francisco, California 94111
Attention: Mitchell R. Cohen
Fax: 415-788-0176

H&F Orchard Partners, L.P.
c/o Hellman & Friedman
One Maritime Plaza, Suite 1200
San Francisco, California 94111
Attention: Mitchell R. Cohen
Fax: 415-788-0176

H&F International Partners, L.P.
c/o Hellman & Friedman
One Maritime Plaza, Suite 1200
San Francisco, California 94111
Attention: Mitchell R. Cohen
Fax: 415-788-0176

GS Capital Partners, L.P.
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention: Terence O'Toole
Fax: 212-902-3000

The Goldman Sachs Group, Inc.
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention: Terence O'Toole
Fax: 212-902-3000

<PAGE>   18

Bridge Street Fund 1992, L.P.
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention: Terence O'Toole
Fax: 212-902-3000

Stone Street Fund 1992, L.P.
c/o Goldman, Sachs & Co.
85 Broad Street
New York, NY 10004
Attention: Terence O'Toole
Fax: 212-902-3000

Providence Media Partners L.P.
c/o Providence Ventures, Inc.
900 Fleet Center
50 Kennedy Plaza
Providence, Rhode Island 02903
Attention: Jonathan Nelson
Fax: 401-751-1790

John W. Stanton and Theresa E. Gillespie
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention: John W. Stanton
Fax: 425-586-8010

PN Cellular, Inc.
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention: John W. Stanton
Fax: 425-586-8010

Stanton Family Trust
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention: John W. Stanton
Fax: 425-586-8010

<PAGE>   19

Stanton Communications Corporation
c/o VoiceStream Wireless Corporation
3650 131st Avenue S.E., Suite 400
Bellevue, WA 98006
Attention: John W. Stanton
Fax: 425-586-8010

Hutchinson Telecommunications
PCS (USA) Limited
c/o Offshore Incorporations Limited
P.O. Box 957
Offshore Incorporations Centre
Road Town, Tortola
British Virgin Islands
Telephone No.: 809-494-2233
Facsimile No.: 809-494-4885

Hutchinson Telecommunications Holdings (USA) Limited
c/o Offshore Incorporations Limited
P.O. Box 957
Offshore Incorporations Centre
Road Town, Tortola
British Virgin Islands
Telephone No.: 809-494-2233
Facsimile No.: 809-494-4885<PAGE>   1
                                                                    EXHIBIT 10.2

                                                                  EXECUTION COPY

                          STOCK SUBSCRIPTION AGREEMENT

                                  BY AND AMONG

                    VOICESTREAM WIRELESS HOLDING CORPORATION,

                                       AND

                                   SONERA LTD.

                            DATED: SEPTEMBER 17, 1999

<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
<S>                                                                               <C>
ARTICLE 1 DEFINITIONS .....................................................       1

ARTICLE 2 PURCHASE OF STOCK; CLOSING ......................................       3

    2.01   Purchase and Exchange of Stock .................................       3
    2.02   Closing ........................................................       3
        (a)    Closing Date ...............................................       3
        (b)    Location ...................................................       3

ARTICLE 3 COVENANTS AND AGREEMENTS ........................................       4

    3.01   Covenant of the Company ........................................       4
    3.02   Covenant of the Investor .......................................       4
    3.03   HSR Act ........................................................       4
    3.04   FCC Consent ....................................................       4
    3.05   Cooperation ....................................................       4
    3.06   Certificate ....................................................       4
    3.07   Merger Consolidation ...........................................       5
    3.08   Settlement Agreement ...........................................       5

ARTICLE 4 REPRESENTATIONS AND WARRANTIES ..................................       5

    4.01   Representations and Warranties of the Company ..................       5
        (a)    Due Organization ...........................................       5
        (b)    Power and Authority; No Violation ..........................       5
        (c)    Legal Matters ..............................................       6
        (d)    Truth and Correctness ......................................       6
        (e)    Purchased Shares ...........................................       6
        (f)    Investment Company Act .....................................       6
        (g)    No Brokers .................................................       6
        (h)    Reports and Financial Statements ...........................       6
    4.02   Representations and Warranties of the Investor .................       7
        (a)    Due Organization ...........................................       7
        (b)    Power and Authority; No Violation ..........................       7
        (c)    Legal Matters ..............................................       7
        (d)    Securities Representation ..................................       8
        (e)    Investment Company Act .....................................       8
        (f)    Truth and Correctness ......................................       9
        (g)    No Brokers .................................................       9
</TABLE>

<PAGE>   3
<TABLE>
<CAPTION>
<S>                                                                              <C>
ARTICLE 5 CONDITIONS TO OBLIGATIONS .......................................       9

    5.01   Conditions to the Obligation of the Company ....................       9
        (a)    Representations and Warranties True ........................       9
        (b)    HSR Act ....................................................       9
        (c)    Purchase Price .............................................       9
        (d)    Resolutions ................................................       10
        (e)    No New Statutes ............................................       10
        (f)    Omnipoint Reorganization Agreement .........................       10
        (g)    Consents ...................................................       10
    5.02   Conditions to the Obligation of the Investor ...................       10
        (a)    Representations and Warranties True ........................       10
        (b)    HSR Act ....................................................       10
        (c)    Stock Certificates .........................................       10
        (d)    Resolutions ................................................       10
        (e)    No New Statutes ............................................       11
        (f)    Omnipoint Reorganization Agreement .........................       11
        (g)    Consents ...................................................       11

ARTICLE 6 MISCELLANEOUS ...................................................       11

    6.01   Expenses .......................................................       11
    6.02   Equitable Remedies .............................................       11
    6.03   Notices ........................................................       11
        (a)    if to the Company, to it at: ...............................       11
        (b)    if to the Investor, to it at; ..............................       12
    6.04   Entire Agreement ...............................................       12
    6.05   Remedies Cumulative ............................................       13
    6.06   Governing Law ..................................................       13
    6.07   Counterparts ...................................................       13
    6.08   Waivers ........................................................       13
    6.09   Successors and Assigns .........................................       13
    6.10   Further Assurances .............................................       13
    6.11   Disclosures ....................................................       13
    6.12   Termination ....................................................       13
        (a)    Events Triggering Termination ..............................       13
        (b)    No Further Obligation ......................................       14
    6.13   Jurisdiction, Consent to Service of Process ....................       14
    6.14   No Claim of Immunity ...........................................       14
</TABLE>

<PAGE>   4

                          STOCK SUBSCRIPTION AGREEMENT

                  STOCK SUBSCRIPTION AGREEMENT, dated as of September 17, 1999
(the "Agreement"), by and between VOICESTREAM WIRELESS HOLDING CORPORATION, a
Delaware corporation (the "Company"), and SONERA LTD., a Finnish limited
liability company ("Investor").

                              W I T N E S S E T H:

                  WHEREAS, the Company is engaged in the communications business
in the United States;

                  WHEREAS, upon the terms and conditions set forth in this
Agreement, the Company has determined to issue and sell, and the Investor has
determined to purchase, for an aggregate purchase price of Five Hundred Million
Ten ($500,000,010) Dollars in cash, 8,771,930 shares of Common Stock, par value
 .001 per share, of the Company (the "Common Stock").

                  NOW, THEREFORE, in consideration 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
hereunder shall have the meanings therein specified for all purposes of this
Agreement, applicable to both the singular and plural forms of any of the terms
defined herein. For purposes of this Agreement:

                  "Aerial Reorganization Agreement" shall mean the Agreement and
Plan of Reorganization, dated as of September 17, 1999, among the Company,
Aerial Communications, Inc., a Delaware corporation ("Aerial"), Telephone and
Data Systems, Inc., a Delaware corporation ("TDS"), VoiceStream Wireless
Corporation, a Washington corporation ("VoiceStream"), and VoiceStream
Subsidiary III Corporation, a Delaware corporation and wholly owned subsidiary
of the Company ("Sub"), pursuant to which Sub shall merge with and into Aerial
(the "Aerial Merger").

                  "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 either controls, is controlled by or
is under common control with, such party. The term "control" shall mean the
power to direct the affairs of such Person by reason of ownership of voting
stock or other equity interests, by contract or otherwise.

<PAGE>   5

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

                  "Beneficially Own" shall have the meaning set forth in Rule
l3d-3 of the Exchange Act.

                  "Business Day" shall mean any day other than a Saturday,
Sunday or a legal holiday in New York, New York, Helsinki, Finland, Seattle,
Washington or any other day on which commercial banks in those locations are
authorized by law or governmental decree to close.

                  "Closing" shall have the meaning set forth in Section 2.02.

                  "Closing Date " shall have the meaning set forth in Section
2.02.

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

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

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

                  "Exchange Act" shall mean the Securities Exchange Act of 1934,
and any similar or successor Federal statute, and the rules and regulations
promulgated thereunder, all as amended, and as the same may be in effect from
time to time.

                  "HSR Act" shall mean the Hart-Scott-Rodino Antitrust
Improvements Act of 1976, as amended.

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

                  "Liens" shall mean any lien, claim, security interest, charge,
encumbrance or title retention agreement of any nature.

                  "Material Adverse Effect on the Company" shall mean a material
adverse effect on the financial condition, operations or business of the Company
and its subsidiaries, taken as a whole, or the ability of the Company to enter
into and consummate the transactions contemplated by this Agreement in
accordance with its terms.

                  "Omnipoint Reorganization Agreement" shall mean the Agreement
and Plan of Reorganization, dated as of June 23, 1999, by and among the Company,
VoiceStream and Omnipoint Corporation, a Delaware corporation.

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

                  "Purchase Price" shall have the meaning set forth in Section
2.01.

                                       2
<PAGE>   6

                  "Purchased Shares" shall have the meaning set forth in Section
2.01.

                  "SEC" shall mean the Securities and Exchange Commission or its
successors.

                  "Securities Act" shall mean the Securities Act of 1933, and
any similar or successor Federal statute, and the rules and regulations
promulgated thereunder, all as amended, and as the same may be in effect from
time to time.

                  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

                           PURCHASE OF STOCK; CLOSING

        2.01 Purchase of Stock.

        Upon the terms and conditions herein set forth, the Investor hereby
subscribes for and agrees to purchase from the Company, and the Company hereby
accepts the Investor's subscription for and agrees to sell to the Investor,
8,771,930 shares of Common Stock (collectively the "Purchased Shares") for a
purchase price per share equal to Fifty-Seven ($57.00) Dollars, for an aggregate
purchase price of Five Hundred Million Ten ($500,000,010) Dollars (collectively,
the "Purchase Price").

        2.02 Closing.

                  (a) Closing Date. Consummation of the purchase of the
Purchased Shares (the "Closing") shall take place, subject to the satisfaction
(or express written waiver) of all conditions to the Closing under Article 5
hereof, simultaneously with the consummation of the transactions contemplated by
the Omnipoint Reorganization Agreement. The date on which the Closing takes
place shall be referred to herein as the "Closing Date."

                  (b) Location. The Closing shall take place at 11:00 A.M. on
the Closing Date, at the offices of the Company located at 3650 131st Avenue,
SE, Bellevue, Washington 98006 or at such other place as the parties hereto
shall agree. At the Closing the Company shall, upon receipt of the Purchase
Price by wire transfer of immediately available funds to the account specified
therefor by the Company, promptly deliver to the Investor duly executed and
issued stock certificates evidencing the Purchased Shares. The Company shall
give the Investor not less than seven (7) days notice of the Closing Date and
the account to which the wire transfer should be made.

                                       3
<PAGE>   7

                                    ARTICLE 3

                            COVENANTS AND AGREEMENTS

        3.01 Covenant of the Company. From and after the execution and delivery
of this Agreement to and including the Closing Date, the Company shall use its
best efforts to cause the transactions contemplated by this Agreement to be
consummated in accordance with the terms hereof.

        3.02 Covenant of the Investor. From and after the execution and delivery
of this Agreement to and including the Closing Date, the Investor shall use its
best efforts to cause the transactions contemplated by this Agreement to be
consummated in accordance with the terms hereof.

        3.03 HSR Act. It is understood that the consummation of this transaction
may be subject to the filing with the Federal Trade Commission and the Antitrust
Division of the Department of Justice of reports and notifications which are
required under the HSR Act and the expiration or termination of certain
applicable waiting periods under the HSR Act without objection by such
authorities. If required the Investor and the Company shall file, or cause to be
filed, as soon as practicable following the date hereof and in no event later
than ten (10) Business Days from the date hereof, with the Federal Trade
Commission and the Antitrust Division of the Department of Justice any and all
such reports or notifications and any other filings required under any other
Federal law or administrative regulations in connection with the purchase of the
Purchased Shares under this Agreement.

        3.04 FCC Consent. The consummation of the transactions contemplated
hereby may be subject to the prior approval or waiver of the FCC and one or more
state regulatory commissions. The parties shall use their best efforts to file
with the FCC and any relevant state regulatory commissions, to the extent the
prior approval or waiver of the FCC or of such regulatory commissions shall be
required, as soon as practicable following the date hereof and in no event later
than ten (10) Business Days from the date hereof, an application requesting the
approval or waiver of the FCC and of any such regulatory commissions to the
transactions contemplated hereby.

        3.05 Cooperation. Each of the parties hereto shall diligently take or
cooperate in the taking of all steps which are necessary or appropriate to
expedite the prosecution and favorable consideration of such applications. The
parties covenant and agree to undertake all actions reasonably requested by the
Federal Trade Commission, the Antitrust Division of the Department of Justice,
the FCC or other regulatory commission and to file such material as shall be
necessary or required to obtain any necessary approvals or waivers or other
authority in connection with the foregoing applications.

        3.06 Certificate. Investor agrees to execute and deliver to the Company
upon the closing of the Omnipoint Reorganization and on the closing of the
Aerial Merger a certificate in the form attached hereto as Schedule 3.06.

                                       4
<PAGE>   8

        3.07 Merger Consideration. In connection with the Aerial Merger,
Investor agrees that neither it nor any of its Affiliates shall submit a Cash
Election Form pursuant to Section 2(d) of the Aerial Reorganization Agreement.

        3.08 Settlement Agreement. Investor has concurrently herewith executed
and delivered the Settlement Agreement and Release in the form attached hereto
as Schedule 3.08.

                                    ARTICLE 4

                         REPRESENTATIONS AND WARRANTIES

        4.01 Representations and Warranties of the Company. The Company
represents and warrants to the Investor, which representations and warranties
shall survive the execution and delivery of this Agreement and the consummation
of the transactions herein contemplated, as follows:

                  (a) Due Organization. The Company is a corporation duly
organized, validly existing and in good standing under the laws of the State of
Delaware.

                  (b) Power and Authority; No Violation. The Company 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 all transactions contemplated hereby have been duly and validly authorized
by all necessary action on the part of the Company and this Agreement
constitutes a legal, valid and binding obligation of the Company enforceable in
accordance with its terms except as such enforceability may be limited by
bankruptcy, insolvency, 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 of the transactions
contemplated hereby by the Company will, with or without the giving of notice or
the passage of time, or both, (i) conflict with, result in a default 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, by-laws, stockholders agreements or other
constituent documents of the Company; (B) any note, bond, indenture, mortgage,
deed of trust, contract, agreement, lease or other instrument or obligation to
which the Company is a party or by which the Company or its property may be
bound or affected except for any default or loss of rights, which individually
or in the aggregate, would not have a Material Adverse Effect on the Company; or
(C) any law, order, judgment, ordinance, rule, regulation or decree to which the
Company is a party or by which it or its property is bound or affected; or (ii)
give rise to any right of first refusal or similar right with respect to any
interest, or any properties or assets, of the Company. Except as set forth on
Schedule 4.01(b) hereof, no permit, consent, approval, authorization,
qualification or registration of, or declaration to or filing with any
governmental or regulatory authority or agency or third party is required to be
obtained or made by the Company in connection with the execution and delivery of
this Agreement or the consummation of the transactions contemplated hereby or
thereby in order to (A) render this Agreement or the transactions contemplated
hereby or thereby valid and effective and (B) enable the Company to sell the
Purchased Shares.

                                       5
<PAGE>   9

                  (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 the Company threatened, against or relating
to the right of the Company to perform its obligations under this Agreement, nor
does the Company know or have reason to be aware 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 would individually or
in the aggregate impair in any material respect the performance of the
obligations of the Company hereunder or the consummation of the transactions
contemplated by this Agreement other than orders or decrees involving the
wireless telephone industry in general.

                  (d) Truth and Correctness. No representation or warranty by
the Company 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.

                  (e) Purchased Shares. The Purchased Shares (i) have been duly
authorized by all necessary corporate action on the part of the Company, (ii)
shall be (when issued in accordance with the terms of this Agreement) validly
issued and outstanding, fully paid and nonassessable, and (iii) shall not be
subject to any preemptive rights of the holders of any other class or series of
the capital stock of the Company, except for rights, if any, pursuant to the
Investor Agreement, dated as of June 23, 1999, among Hutchinson
Telecommunications PCS (USA) Limited, Hutchinson Telecommunications Limited and
the Company. At the Closing, the Purchased Shares shall be free and clear of all
Liens, with the exception of any restrictions on transferability under the
Securities Act or any securities laws of any jurisdiction.

                  (f) Investment Company Act. The Company is not an "investment
company" within the meaning of the Investment Company Act of 1940, as amended.

                  (g) No Brokers. No agent, broker, investment banker, Person or
firm is or will be entitled to any broker's or finder's fee or any other
commission or similar fee directly or indirectly in connection with the
transactions contemplated by this Agreement based in any way on any
arrangements, agreements or understandings made by or on behalf of the Company
or an Affiliate thereof, and the Company hereby agrees to indemnify the Investor
and agrees to hold harmless the Investor against and in respect of any claims
for brokerage and other commissions relating to such transactions based in any
way on any arrangements, agreements or understandings made by or on behalf of
the Company or an Affiliate thereof.

                  (h) Reports and Financial Statements. The Company has filed
all reports required to be filed with the SEC since May 3, 1999, (collectively,
including all exhibits thereto, the "SEC Reports"). None of such SEC Reports, as
of their respective dates (as amended through the date hereof), contained any
untrue statement of a material fact or omitted to state a material fact required
to be stated therein or necessary to make the statements therein, in light of
the circumstances under which they were made, not misleading. Each of the
financial statements (including the related notes) included in the SEC Reports
presents fairly, in all material respects, the consolidated financial position
and consolidated results of operations and cash flows of the

                                       6
<PAGE>   10

Company and its subsidiaries as of the respective dates or for the respective
periods set forth therein, all in conformity with generally accepted accounting
principles consistently applied during the periods involved, subject, in the
case of the unaudited interim financial statements, to normal yearend
adjustments and any other adjustments described therein. All such SEC Reports,
as of their respective dates (as amended through the date hereof), complied in
all material respects with the requirements of the Exchange Act.

        4.02 Representations and Warranties of the Investor. Investor represents
and warrants to the Company, which representations and warranties shall survive
the execution and delivery of this Agreement and the consummation of the
transactions herein contemplated, as follows:

                  (a) Due Organization. Investor is a limited liability company
duly organized validly existing and in good standing under the laws of the
Republic of Finland.

                  (b) Power and Authority; No Violation. The Investor 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 all transactions contemplated hereby have been duly and validly authorized
by all necessary action on the part of the Investor and this Agreement
constitutes a legal, valid and binding obligation of the Investor enforceable in
accordance with its terms, except as such enforceability may be limited by
bankruptcy, insolvency, 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 of the transactions
contemplated hereby by the Investor will, with or without the giving of notice
or the passage of time, or both, (i) conflict with, result in a default 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 memorandum and articles of association, certificate of
incorporation, by-laws, stockholders agreements or other constituent documents
of the Investor; (B) any material note, bond, indenture, mortgage, deed of
trust, contract, agreement, lease or other instrument or obligation to which the
Investor is a party or by which it or its property may be bound or affected,
except for any default or loss of rights, which, individually or in the
aggregate would not have a material adverse effect on the Investor or its
ability to perform its obligations under this Agreement or to purchase the
Purchased Shares; or (C) any law, order, judgment, ordinance, rule, regulation
or decree to which the Investor is a party or by which it or its property is
bound or affected; or (ii) give rise to any right of first refusal or similar
right with respect to any interest, or any properties or assets, of the
Investor. No permit, consent, approval, authorization, qualification or
registration of, or declaration to or filing with any governmental or regulatory
authority or agency or third party is required to be obtained or made by the
Investor in connection with the execution and delivery of this Agreement or the
consummation of the transactions contemplated hereby in order to (A) render this
Agreement or the transactions contemplated hereby valid and effective and (B)
enable the Investor to purchase the Purchased Shares.

                  (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 the Investor

                                       7
<PAGE>   11

threatened, against or relating to the Investor's right to perform its
obligations under this Agreement, nor does the Investor know or have reason to
be aware 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 would individually or in the aggregate impair in any material
respect the performance of the Investor's obligations hereunder or the
consummation of the transactions contemplated by this Agreement other than
orders or decrees involving the wireless telephone industry in general.

                  (d) Securities Representation. The Investor acknowledges that:
(i) it is not a United States Person (as defined in Regulation S under the
Securities Act) and, in determining to enter into this Agreement, purchase the
Purchased Shares and perform its obligations hereunder, has made its decision
outside the United States; (ii) it is an accredited investor (as defined in Rule
501 under the Securities Act); (iii) it has such knowledge and experience in
financial and business matters that it is capable of evaluating the merits and
risks of investing in the Company as contemplated hereby or, alternatively, that
it has engaged the services of a representative who has such knowledge and
experience in financial and business matters as to be capable of evaluating the
merits and risks of the proposed investment and who has reviewed the proposed
investment on its behalf, (iv) the Purchased Shares being delivered by the
Company to the Investor have not been registered under the Securities Act or
under the securities laws of any state in reliance upon Federal and state
exemptions for offshore transactions or transactions not involving a public
offering and are not being acquired with a view to the distribution thereof
except pursuant to a registration statement in compliance with Federal and state
securities laws or an exemption therefrom; (v) the Purchased Shares must be held
by the Investor indefinitely unless subsequently so registered or if an
exemption from such registration is available; and (vi) it has received
information concerning the Company and has had the opportunity to obtain
additional information as desired in order to evaluate the merits and risks
inherent in holding the Purchased Shares. The Investor agrees that the share
certificate(s) which the Investor receives from the Company shall be legended
with the following legend:

                "THE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE
                SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE
                OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED, EXCEPT
                PURSUANT TO AN EXEMPTION FROM REGISTRATION THEREUNDER OR
                PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT
                THEREUNDER."

                  (e) Investment Company Act. The Investor is not an "investment
company" within the meaning of the Investment Company Act of 1940, as amended.

                                       8
<PAGE>   12

                  (f) Truth and Correctness. No representation or warranty by
the Investor 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.

                  (g) No Brokers. No agent, broker, investment banker, Person or
firm other than ARC Associates is or will be entitled to any broker's or
finder's fee or any other commission or similar fee directly or indirectly in
connection with the transactions contemplated by this Agreement based in any way
on any arrangements, agreements or understandings made by or on behalf of the
Investor or an Affiliate thereof, and the Investor hereby agrees to indemnify
the Company and agrees to hold harmless the Company against and in respect of
any claims for brokerage and other commissions relating to such transactions
based in any way on any arrangements, agreements or understandings made by or on
behalf of the Investor or an Affiliate of the Investor, including any fees,
amounts or commissions owed to ARC Associates.

                                    ARTICLE 5

                            CONDITIONS TO OBLIGATIONS

        5.01 Conditions to the Obligation of the Company. The obligation of the
Company to perform, fulfill or carry out its agreements, undertakings and
obligations herein made or expressed to be performed, fulfilled or carried out
on the Closing Date is and shall be subject to fulfillment of or compliance
with, on or prior to the Closing Date, the following conditions precedent, any
of which may be waived by the Company in its sole discretion, in whole or in
part:

                  (a) Representations and Warranties True. The Investor's
representations and warranties contained in this Agreement shall be deemed to
have been made again at and as of the time of the Closing Date and shall then be
true in all material respects. The Investor shall have performed and complied in
all material respects with all agreements and covenants required by this
Agreement to be performed or complied with by it prior to or at the Closing
Date. The Company shall have been furnished with a certificate of the Investor
signed by one of its senior executive officers, dated the Closing Date,
certifying to the fulfillment of the foregoing conditions by it and to the truth
and correctness in all material respects, except for changes contemplated by
this Agreement, as of the Closing Date, of the representations and warranties
made by it contained herein and the satisfaction on the part of the Investor of
all conditions to the obligations of the Company under this Section 5. 01.

                  (b) HSR Act. The waiting periods, if applicable, of the HSR
Act shall have expired or been terminated.

                  (c) Purchase Price. The Investor shall have delivered the
Purchase Price to the Company as required hereunder.

                                       9
<PAGE>   13

                  (d) Resolutions. The Company shall have been furnished with
certified copies of the resolutions duly adopted by the board of directors of
the Investor authorizing the execution, delivery and performance of this
Agreement.

                  (e) No New Statutes. No statute, rule or regulation shall have
been enacted by any state or Federal government or governmental agency in the
United States or Finland which would render the consummation of this Agreement
unlawful.

                  (f) Omnipoint Reorganization Agreement. The transactions
contemplated by the Omnipoint Reorganization Agreement shall have been, or
simultaneously with the consummation of the transactions contemplated hereby
shall be, consummated in accordance with its terms.

                  (g) Consents. Any FCC consents required for the consummation
of the transactions contemplated hereby shall have been obtained, without any
conditions or restrictions which would have a Material Adverse Effect on the
Company, and such consents are final and nonappealable.

        5.02 Conditions to the Obligation of the Investor. The obligation of the
Investor to perform, fulfill or carry out its agreements, undertakings and
obligations herein made or expressed to be performed, fulfilled or carried out
on the Closing Date is and shall be subject to fulfillment of or compliance
with, on or prior to the Closing Date, the following conditions precedent, any
of which may be waived by the Investor, in its sole discretion, in whole or in
part:

                  (a) Representations and Warranties True. Each of the Company's
representations and warranties contained in this Agreement shall be deemed to
have been made again at and as of the time of the Closing Date and shall then be
true in all material respects. The Company shall have performed and complied in
all material respects, with all agreements and covenants required by this
Agreement to be performed or complied with by it prior to or at the Closing
Date. The Investor shall have been furnished with a certificate of the Company
signed by one of its senior executive officers, dated the Closing Date,
certifying to the fulfillment of the foregoing conditions by it and to the truth
and correctness in all material respects, except for changes contemplated by
this Agreement, as of the Closing Date, of the representations and warranties
made by it contained herein and the satisfaction on the part of the Company of
all conditions to the obligations of the Investor under this Section 5.02.

                  (b) HSR Act. The waiting periods, if applicable, of the HSR
Act shall have expired or been terminated.

                  (c) Stock Certificates. The Company shall have delivered to
the Investor duly executed and issued stock certificates representing the
Purchased Shares.

                  (d) Resolutions. The Company shall have delivered to the
Investor a certified copy of the resolution or resolutions duly adopted by its
board of directors authorizing the execution, delivery and performance of this
Agreement.

                                       10
<PAGE>   14

                  (e) No New Statutes. No statute, rule or regulation shall have
been enacted by any state or Federal government or governmental agency in the
United States or Finland which would render the consummation of this Agreement
unlawful.

                  (f) Omnipoint Reorganization Agreement. The transactions
contemplated by the Omnipoint Reorganization Agreement shall have been, or
simultaneously with the consummation of the transactions contemplated hereby
shall be, consummated in accordance with its terms.

                  (g) Consents. Any FCC consents required for the consummation
of the transactions contemplated hereby shall have been obtained, without any
conditions or restrictions which would have a material adverse effect on the
ability of the Investor to comply with its obligations hereunder, and such
consents are final and nonapplicable.

                                    ARTICLE 6

                                  MISCELLANEOUS

        6.01 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.

        6.02 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,
that the party seeking specific performance has an adequate remedy at law.

        6.03 Notices. All notices, claims and other communications hereunder
shall be in writing and shall be made by hand delivery, registered or certified
mail (postage prepaid, return receipt requested), facsimile, or overnight air
courier guaranteeing next day delivery

                  (a) if to the Company, to it at:

                            VoiceStream Wireless Holding Corporation
                            3650 131st Avenue, SE
                            Bellevue, Washington 98006
                            Attention: Alan R. Bender, Esq.
                            Facsimile No.: 425-586-8080

                                       11
<PAGE>   15

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

                            Friedman Kaplan & Seiler LLP
                            875 Third Avenue
                            New York, New York 10022
                            Attention: Barry A. Adelman, Esq.
                            Facsimile No.: 212-355-6401

                            and

                            Preston Gates & Ellis LLP
                            5000 Columbia Center
                            701 Fifth Avenue
                            Seattle, WA 98104
                            Attention: Richard B. Dodd, Esq.
                            Facsimile No.: 206-623-7022

                  (b)  if to the Investor, to it at;

                            Sonera Ltd.
                            P.O. Box, Fin - 00051 - Tele
                            Teollisuuskatu 15,
                            Helsinki, Finland
                            Attention: Maire Laitinen, Esq.
                            Facsimile No.: 011-358-2040-3414

                            with a copy (which shall not constitute notice) to:
                            Patton Boggs LLP
                            2550 M. St. N. W.
                            Washington, D.C. 20037
                            Attention: Richard M. Stolbach, Esq.
                            Facsimile No.: 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
6.03. All such notices and communications shall be deemed to have been duly
given at the time delivered by hand, if personally delivered; five (5) Business
Days after being deposited in the mail, first class postage prepaid, return
receipt requested, if mailed; when receipt is 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.

6.04 Entire Agreement. This Agreement, together with the Schedules annexed
hereto, contains 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

                                       12
<PAGE>   16

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.

        6.05 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.

        6.06 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.

        6.07 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.

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

        6.09 Successors and Assigns. This Agreement shall be binding upon and
inure to the benefit of the parties hereto and to their respective 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 party.

        6.10 Further Assurances. The Investor shall, at the request of the
Company, and the Company shall, at the request of the Investor, 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.

        6.11 Disclosures. No public announcement by any party hereto with regard
to the transactions contemplated hereby or the material terms hereof shall be
issued by any party without the mutual prior consent of the other parties,
except that in the event 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 and such party furnishes the other party a written opinion of
outside legal counsel, or other counsel reasonably acceptable to the party being
furnished such opinion, to that effect, then such party may issue the legally
required press release.

        6.12 Termination.

                  (a) Events Triggering Termination. This Agreement may be
terminated and the transactions contemplated hereby may be abandoned, without
further obligation of the Company and the Investor, at any time prior to the
Closing Date as follows:

                                       13
<PAGE>   17

                        (i) by mutual written consent duly authorized by the
boards of directors of the Company and the Investor; or

                        (ii) by the Company or the Investor if the Omnipoint
Reorganization Agreement shall have been terminated and the transactions
contemplated thereby abandoned; or

                        (iii) by the Company or the Investor if the consummation
of the transactions contemplated hereby shall be prohibited by a final,
non-appealable order, decree or injunction of a court of competent jurisdiction.

                  (b) No Further Obligation. In the event of a termination of
this Agreement, no party hereto shall have any liability or further obligation
to any other party to this Agreement except that nothing herein will relieve any
party from liability for any breach of this Agreement.

        6.13 Jurisdiction, Consent to Service of Process. (a) 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 objection to venue therein); provided, however, that such
consent to jurisdiction is solely for the purpose referred to in this Section
6.13 (a) 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.

                  (a) The Investor 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 the Investor were a resident of the State
of Delaware, and had been lawfully served with such process in such
jurisdiction, and waives all claims of error by reason of such service, provided
that in the case of any service upon such agent and attorney the Company shall
also deliver a copy thereof to the Investor at the address and in the manner
specified in Section 6.03 hereof. In the event that such agent and attorney
resigns or otherwise becomes incapable of acting as such, the Investor will
appoint a successor agent and attorney in Wilmington, Delaware, reasonably
satisfactory with like powers, or if the Investor fails to make such
appointment, the Investor hereby authorizes the Company to appoint such agent
and attorney for the Investor. The Investor shall pay the annual fee due to The
Corporation Trust Company or such successor agent for acting in such capacity;
provided, however, that if the Investor shall not make such payment, then the
Company shall have the right to do so.

        6.14 No Claim of Immunity. The Investor agrees that, to the extent that
it or any of its property, its Affiliates, or any 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

                                       14
<PAGE>   18

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).

                                       15
<PAGE>   19

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

                                       VOICESTREAM WIRELESS HOLDING CORPORATION

                                       By:
                                          ------------------------------------
                                             Name:
                                             Title:

                                       SONERA LTD.

                                       By:
                                          ------------------------------------
                                             Name:
                                             Title:

                                       16
<PAGE>   20

                                                                SCHEDULE 4.01(b)

                   Required Consents, Approvals, Filings, Etc.

Stockholder approval of VoiceStream Holding

Any FCC or state regulatory approval

Appropriate SEC Filings

HSR Filing

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