Document:

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                                                                   EXHIBIT 10.28

================================================================================

                            STOCKHOLDERS AGREEMENT

                                     among

                                  IPCS, INC.

                                  AND CERTAIN

                                    OF ITS

                                 STOCKHOLDERS

                           Dated as of July 12, 2000

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                               TABLE OF CONTENTS
                                                                            Page
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SECTION 1.  DEFINITIONS...................................................    4
     1.1    Defined Terms.................................................    4
     1.2    Other Definitional Provisions; Interpretation.................    5

SECTION 2.  TRANSFERS AND ISSUANCES.......................................    5
     2.1    Limitations on Transfer.......................................    5
     2.2    Permitted Transfers...........................................    6
     2.3    Effect of Void Transfers......................................    7
     2.4    Legend on Securities..........................................    7
     2.5    Tag-Along Rights..............................................    8
     2.6    Drag-Along Rights.............................................    9

SECTION 3.  BOARD OF DIRECTORS............................................   11
     3.1    Board of Directors............................................   11

SECTION 4.  PREEMPTION RIGHTS.............................................   12
     4.1    Preemptive Rights.............................................   12

SECTION 5.  BLACKSTONE RIGHT..............................................   13
     5.1    Redemption Request............................................   13
     5.2    Sale of the Company...........................................   15

SECTION 6.  BLACKSTONE INITIAL PUBLIC OFFERING............................   15
     6.1    Initial Public Offering.......................................   15

SECTION 7.  BLACKSTONE INFORMATION RIGHTS.................................   15
     7.1    Information Rights............................................   15

SECTION 8.  BLACKSTONE BUSINESS COMBINATION RIGHTS........................   16
     8.1    Approval Rights...............................................   16
     8.2    Public Company Change of Control..............................   18
     8.3    Private Company Change of Control.............................   20

SECTION 9.  REPRESENTATIONS AND WARRANTIES................................   21
     9.1    Representations of Each of the Parties........................   21

SECTION 10. MISCELLANEOUS.................................................   23
     10.1   Additional Securities Subject to Agreement....................   23
     10.2   Registration and Listing......................................   23
     10.3   Restrictions on Blackstone Investments........................   23
     10.4   Restrictions on Company Investments...........................   24
     10.5   Geneseo and Cambridge Approval................................   24
     10.6   Injunctive Relief.............................................   24
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     10.7   Other Stockholders' Agreements.................................   24
     10.8   Amendments.....................................................   24
     10.9   Successors, Assigns and Transferees............................   24
     10.10  Notices........................................................   25
     10.11  Integration....................................................   26
     10.12  Consent of Blackstone..........................................   26
     10.13  Severability...................................................   26
     10.14  Counterparts...................................................   26
     10.15  Governing Law..................................................   27
     10.16  Jurisdiction...................................................   27
     10.17  Mutual Waiver of Jury Trial....................................   27
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                            STOCKHOLDERS AGREEMENT

          STOCKHOLDERS AGREEMENT (this "Agreement"), dated as of July 12, 2000,
                                        ---------
by and among Blackstone/iPCS L.L.C., a Delaware limited liability company,
Blackstone iPCS Capital Partners L.P., a Delaware limited partnership, and
Blackstone Communications Partners I L.P., a Delaware limited partnership
(collectively with any of their Affiliates which may purchase Series A-2
Convertible Participating Preferred Stock of the Company pursuant to the
Investment Agreement (as defined below), "Blackstone"), TCW/Crescent Mezzanine
                                          ----------
Partners II, L.P., TCW/Crescent Mezzanine Trust II, TCW Leveraged Income Trust,
L.P., TCW Leveraged Income Trust II, L.P., TCW Leveraged Income Trust IV, L.P.,
TCW Shared Opportunity Fund II, L.P., Shared Opportunity Fund IIB, L.L.C. and
TCW Shared Opportunity Fund III, L.P. (collectively with any of their Affiliates
which may purchase Series A-2 Convertible Participating Preferred Stock of the
Company pursuant to the Investment Agreement, "TCW" and, together with
                                               ---
Blackstone, the "Purchasers"), Geneseo Communications, Inc., an Illinois
                 ----------
corporation ("Geneseo"), Cambridge Telcom, Inc., an Illinois corporation
              -------
("Cambridge") (Blackstone, TCW,  Geneseo and Cambridge, collectively, the
  ---------
"Stockholders"), and iPCS, Inc., a Delaware corporation (the "Company").
 ------------                                                 -------

                             W I T N E S S E T H :
                             - - - - - - - - - -

          WHEREAS, the Company and the Purchasers are parties to an Investment
Agreement, dated as of July 12, 2000, pursuant to which the Purchasers are
purchasing newly issued shares of Series A-1 Convertible Participating Preferred
Stock of the Company and have agreed, subject to certain conditions, to purchase
newly issued shares of Series A-2 Convertible Participating Preferred Stock of
the Company, in each case convertible into shares of Common Stock (as defined
below);

          WHEREAS, as a condition to such purchases, the parties hereto desire
to make certain arrangements among themselves with respect to matters set forth
herein; and

          NOW, THEREFORE, in consideration of the mutual covenants and
agreements herein contained, the parties hereto agree as follows:

          SECTION 1.  DEFINITIONS

          1.1  Defined Terms.  As used in this Agreement, the following
               -------------
capitalized terms shall have the meanings ascribed to them below:

          "Affiliate" means, with respect to any Person, any other Person which
           ---------
directly or indirectly controls or is controlled by or is under common control
with such Person. As used in this definition, "control" (including its
correlative meanings, "controlled by" and "under common control with") shall
mean possession, directly or indirectly, of power to direct or cause the
direction
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of management or policies (whether through ownership of securities or
partnership or other ownership interests, by contract or otherwise) of such
Person.

          "Beneficial owner" or "beneficially own" has the meaning given such
           ----------------      ----------------
term in Rule 13d-3 under the Exchange Act and a Person's beneficial ownership of
either Common Stock or Preferred Stock or other voting securities of the Company
shall be calculated in accordance with the provisions of such Rule; provided,
                                                                    --------
however, that for purposes of determining beneficial ownership, a Person shall
-------
be deemed to be the beneficial owner of any security which such Person has the
right to acquire, without the occurrence of any contingency other than the
payment of any conversion or exercise price within sixty (60) days of the date
of calculation, upon the conversion, exchange or exercise of any warrants,
options, rights or other securities, including the Preferred Stock.

          "Business Combination Transaction" shall mean any merger,
           --------------------------------
consolidation, reorganization, recapitalization, spin-off, liquidation, joint
venture, partnership, tender or exchange offer or asset or stock purchase, sale
or exchange or any similar transaction or any series or combination of related
transactions pursuant to any agreement between the Company or any of its
Subsidiaries, on the one hand, and any other Person, on the other.

          "Business Day" shall mean any day except a Saturday, a Sunday, or
           ------------
other day on which commercial banks in the State of New York or Illinois are
authorized or required by law or executive order to close.

          "Common Stock" means the common stock, par value $0.01 per share, of
           ------------
the Company and any securities issued in respect thereof, or in substitution
therefor, in connection with any stock split, dividend, spin-off or combination,
or any reclassification, recapitalization, merger, consolidation, exchange or
other similar reorganization or business combination.

          "Common Stock Equivalents" means any stock (including the Preferred
           ------------------------
Stock), warrants, rights, calls, options, debt or other securities exchangeable
or exercisable for or convertible into Common Stock.  Any reference herein to
the number of Common Stock Equivalents shall be deemed to refer to the number of
shares of Common Stock into which such Common Stock Equivalents are exchangeable
or exercisable or convertible into.

          "Company Sale" shall mean a sale of all or substantially all of the
           ------------
assets or all or substantially all of the capital stock of the Company,
including by way of merger or consolidation, in a single transaction or series
of related transactions.

          "Excluded Issuances" means (i) issuances of Securities with respect to
           ------------------
acquisitions by the Company or any of its Subsidiaries of assets or interests in
a business or entity in arm's length bona fide transactions with an unaffiliated
third party, (ii) issuances of Securities (including stock options and similar
securities or rights) to current or former employees, directors or consultants
of the Company or any of its Subsidiaries as approved by the Board of Directors
of the Company (the

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"Company Board") or pursuant to plans or arrangements approved by the Company
 -------------
Board and (iii) issuances of Common Stock in a Public Offering.

          "Governmental Entity" means any court, department, body, board,
           -------------------
bureau, administrative agency or commission or other governmental authority or
instrumentality.

          "Investment Agreement" means the Investment Agreement dated as of July
           --------------------
12, 2000 among the Purchasers and the Company, as amended from time to time.

          "Minimum Public Offering" means the first underwritten Public Offering
           -----------------------
in which (i) the Company receives aggregate gross proceeds (before deduction of
underwriting discounts and expenses of sale) of at least $30,000,000 and (ii)
the Common Stock has been accepted for listing on The New York Stock Exchange,
Inc. or admitted for quotation to the Nasdaq National Market, or such other
securities exchange or market as Blackstone may approve, subject to official
notice of issuance.

          "Person" or "person" means an individual, corporation, limited
           ------      ------
liability company, association, partnership, group (as defined in Section
13(d)(3) of the Exchange Act), trust, joint venture, business trust or
unincorporated organization, or a government or any agency or political
subdivision thereof or other entity of any nature whatsoever.

          "POPs" means, with respect to any Basic Trading Area for which a Basic
           ----
Trading Area license is issued by the Federal Communications Commission or other
geographical area, the most recent projection of the population of such
geographical area as published in a demographic data source based upon the most
recent U.S. census bureau data.

          "Preferred Stock" means the Series A-1 Convertible Participating
           ---------------
Preferred Stock of the Company and the Series A-2 Convertible Participating
Preferred Stock of the Company.

          "Private Company" shall mean any Person other than a Public Company.
           ---------------

          "Private Company Business Combination Transaction" means any Business
           ------------------------------------------------
Combination Transaction between the Company or any of its Subsidiaries and a
Private Company or any of its Subsidiaries.

          "Public Company" shall mean a Person whose common stock or equivalent
           --------------
thereof is listed on The New York Stock Exchange, Inc. or quoted on the Nasdaq
National Market and of which (i) the aggregate market value of such common stock
or equivalent thereof exceeds $200,000,000, (ii) the aggregate market value of
such common stock or equivalent thereof held by Persons who are not Affiliates
or any officer, director, employee or stockholder holding of record or
beneficially more than 5% of any class of voting securities of such Person or
any Subsidiary of such Person or any individual related by blood, marriage or
adoption to such individual or any entity in which such Person or individual
owns a greater than 5% beneficial interest (collectively, "Related Parties") of
                                                           ---------------
such Person exceeds $50 million and (iii) it is reasonably anticipated that such
common

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stock or equivalent thereof will continue to be listed on The New York Stock
Exchange, Inc. or quoted on the Nasdaq National Market upon the consummation of
the applicable transaction, in each case on the date the applicable transaction
agreement with such Public Company is entered into by the Company or any of its
Subsidiaries.

          "Public Company Business Combination Transaction" means any Business
           -----------------------------------------------
Combination Transaction between the Company or any of its Subsidiaries and a
Public Company or any of its Subsidiaries.

          "Public Offering" means the closing of a public offering of shares of
           ---------------
Common Stock by the Company (other than shares of Common Stock issuable upon
exercise of the Excluded Warrants (as defined in the Certificates of
Designations)) in a primary offering pursuant to an effective registration
statement (other than on Form S-4, Form S-8 or their equivalent) filed by the
Company under the Securities Act.

          "Recognized Exchange" means The New York Stock Exchange, Inc. or  the
           -------------------
Nasdaq National Market.

          "Registration Rights Agreement" means the Registration Rights
           -----------------------------
Agreement, dated as of July 12, 2000 among the Purchasers and the Company, as
amended from time to time.

          "Restricted Securities" means all Securities other than (i) Securities
           ---------------------
that have been registered under an effective registration statement pursuant to
the Securities Act and (ii) Securities with respect to which the holder thereof
shall have delivered to the Company either (A) an opinion, in form and substance
reasonably satisfactory to the Company, of counsel, who shall be reasonably
satisfactory to the Company, or (B) a "no action" letter from the staff of the
Securities and Exchange Commission, to the effect that subsequent Transfers of
such Securities may be effected without registration under the Securities Act or
compliance with such Rule 144.

          "Securities" means shares of Common Stock or Common Stock Equivalents
           ----------
or other securities of the Company, other than debt securities that are not
Common Stock Equivalents, whether owned on the date hereof or hereafter
acquired.

          "Subsidiary" means, with respect to any Person, any other corporation,
           ----------
limited liability company, association or other business entity of which more
than 50% of the shares of voting stock or other voting rights are owned or
controlled, directly or in directly, by such Person or a Subsidiary of such
Person.

          "Securities Act" means the Securities Act of 1933, as amended, and the
           --------------
rules and regulations promulgated thereunder, as the same may be amended from
time to time.

          "Transaction Agreements" shall mean the Investment Agreement, the
           ----------------------
Stockholders Agreement, the Series A-1 Preferred Stock Certificate of
Designations, the Series A-2 Preferred

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Stock Certificate of Designations, the Registration Rights Agreement and the
Transaction Fee Agreement.

          "Transfer" means any direct or indirect transfer, sale, assignment,
           --------
distribution, exchange, hypothecation or other disposition of any Securities or
any interest therein, including transfers by operation of law in connection with
a merger transaction or otherwise, but excluding any mortgage, pledge or
granting of a security interest therein.

          "Unrestricted Marketable Securities" means equity securities which (i)
           ----------------------------------
are listed or quoted, as applicable, on a Recognized Exchange, (ii) may be
freely sold to the public on such Recognized Exchange without restriction
(including without compliance with the registration requirements of the
Securities Act) other than customary restrictions pursuant to the trading rules
of such Recognized Exchange and (iii) have an average daily trading volume in
terms of number of securities over the past six months on the applicable
Recognized Exchange ending the third trading day preceding the proposed date of
Transfer hereunder that is at least 10% of the number of securities to be
received by the Purchasers pursuant to Section 2.6.

          1.2  Other Definitional Provisions; Interpretation.  (i) The words
               ---------------------------------------------
"hereof", "herein" and "hereunder" and words of similar import when used in this
Agreement shall refer to this Agreement as a whole and not to any particular
provision of this Agreement, and Section and Subsection references are to this
Agreement unless otherwise specified.

          (ii)  The headings in this Agreement are included for convenience of
reference only and shall not limit or otherwise affect the meaning or
interpretation of this Agreement.

          (iii) The meanings given to terms defined herein shall be equally
applicable to both the singular and plural forms of such terms.

          SECTION 2.  TRANSFERS AND ISSUANCES

          2.1  Limitations on Transfer.  (a) Each of the Stockholders hereby
               -----------------------
agrees that it will not, directly or indirectly, Transfer any Securities unless
such Transfer complies with the provisions hereof and (i) such Transfer is made
pursuant to an effective registration statement under the Securities Act and, if
required, has been registered under all applicable state securities or "blue
sky" laws  or (ii)  no such registration is required because of the availability
of an exemption from registration under the Securities Act and all applicable
state securities or "blue sky" laws.

          (b)  Except as provided in Section 2.2 hereof or pursuant to any
Business Combination Transaction, from and after the first Public Offering,
Geneseo and Cambridge each agrees that without the prior written consent of
Blackstone, it will not Transfer any Securities at any time until after the date
occurring six months after the expiration of the lockup period referred to in
Section 2.1(c) hereof with respect to such Public Offering.

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          (c)   Except as provided in Section 2.2 hereof or pursuant to a
Business Combination Transaction, each Stockholder agrees that it shall not, and
it shall cause any transferee of its Securities to agree not to (in form and
substance reasonably satisfactory to the non-transferring Stockholders),
Transfer any Securities during the 20 days prior to, and for up to a 180-day
period beginning upon, an underwritten Public Offering of Securities (whether
pursuant to the Registration Rights Agreement or otherwise, except as part of
such Public Offering) if and to the extent reasonably requested in writing (with
reasonable prior written notice) by the managing underwriter of such
underwritten Public Offering or by the Company on its behalf.

          (d)   Except as provided in Section 2.2 or pursuant to any Business
Combination Transaction or Public Offering, Geneseo and Cambridge each agrees
that without the prior written consent of Blackstone it will not Transfer any
Securities at any time until after July 12, 2002.

          2.2   Permitted Transfers.  (a) Notwithstanding anything contained
                -------------------
herein to the contrary (including the limitations set forth in Sections 2.1(b),
(c) and (d) above), each of Geneseo and Cambridge shall be entitled, from time
to time, to Transfer any or all of the Securities owned by it to any of its
Affiliates who agree in a writing reasonably satisfactory in form and substance
to Blackstone to become a party to, and be bound to the same extent as its
transferor by the terms of, this Agreement, and any such transferee shall be
deemed to be a "Stockholder" hereunder (any such transferee, a "Permitted
                                                                ---------
Transferee").
----------

          (b)   If, while any Permitted Transferee holds any Securities, such
Permitted Transferee ceases to qualify as Permitted Transferee in relation to
the transferor Stockholder from whom such Permitted Transferee received such
Securities (an "Unwinding Event"), then:
                ---------------

          (i)   the relevant transferor Stockholder shall forthwith notify the
other Stockholders of the pending occurrence of such Unwinding Event; and

          (ii)  prior to such Unwinding Event, such transferor Stockholder shall
     take all actions necessary to effect a Transfer of all the Securities held
     by the relevant Permitted Transferee either back to such transferor
     Stockholder or, pursuant to this Section 2.2, to another Person that
     qualifies as a Permitted Transferee of such transferor Stockholder.

          (c)   Notwithstanding anything contained herein to the contrary,
during the restrictive period referred to in Section 2.1(d) hereof Geneseo and
Cambridge shall be entitled to Transfer in one or more bona fide private
placement transactions up to such aggregate number of shares of Common Stock
that result in aggregate gross proceeds (before deduction of underwriting
discounts, if any, and expenses of sale) of $40,000,000.

          2.3   Effect of Void Transfers. In the event of any purported Transfer
                ------------------------
of any Securities in violation of the provisions of this Agreement, such
purported Transfer shall be void and of no effect and the Company shall not give
effect to such Transfer. The Company shall not be required to enter in its stock
or other records, or reflect, recognize or give effect to for any purpose, any
Transfer of Securities in violation of this Agreement.

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          2.4  Legend on Securities.  (a) Each certificate representing
               --------------------
Securities issued to any Stockholder shall bear the following legend on the face
thereof:

          "THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
          SECURITIES ACT OF 1933, AS AMENDED, OR UNDER ANY STATE SECURITIES
          LAWS. SUCH SECURITIES MAY NOT BE SOLD OR OTHERWISE TRANSFERRED, EXCEPT
          (1) ACCORDING TO AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO
          iPCS, INC. (THE "COMPANY") IN A TRANSACTION THAT IS EXEMPT FROM, OR
          NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT,
          OR (2) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE
          SECURITIES ACT, IN EACH CASE IN ACCORDANCE WITH ANY APPLICABLE
          SECURITIES LAWS OF ANY STATE OF THE UNITED STATES."

          "THE SECURITIES REPRESENTED HEREBY ARE SUBJECT TO A STOCKHOLDERS
          AGREEMENT AMONG THE HOLDER HEREOF, CERTAIN OTHER PARTIES AND THE
          COMPANY, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE COMPANY.
          NO TRANSFER, SALE, ASSIGNMENT, EXCHANGE, HYPOTHECATION OR OTHER
          DISPOSITION OF THE SECURITIES REPRESENTED BY THIS CERTIFICATE MAY BE
          MADE EXCEPT IN ACCORDANCE WITH THE PROVISIONS OF SUCH AGREEMENT,
          ALTHOUGH MORTGAGES AND PLEDGES OF SUCH SECURITIES ARE PERMITTED."

          (b)  In the event that any Securities shall cease to be Restricted
Securities, the Company shall, upon the written request of the holder thereof,
issue to such holder a new certificate evidencing such Securities without the
first paragraph of the legend required by Section 2.4(a) endorsed thereon.  In
the event that any Securities shall cease to be subject to the restrictions on
transfer set forth in this Agreement, the Company shall, upon the written
request of the holder thereof, issue to such holder a new certificate evidencing
such Securities without the legend required by the second paragraph of Section
2.4(a).

          2.5  Tag-Along Rights.  (a) Except for any proposed Transfer or series
               ----------------
of related Transfers by Geneseo and Cambridge (in such capacity, a "Transferring
                                                                    ------------
Stockholder") of 500,000 or fewer shares of Common Stock and/or Common Stock
-----------
Equivalents individually or 2,000,000 shares of Common Stock and/or Common Stock
Equivalents in the aggregate as otherwise permitted hereunder, the Transferring
Stockholder shall have the obligation, and each Purchaser shall have the right,
to require the proposed transferee to purchase from such Purchaser a number of
shares of Common Stock or Common Stock Equivalents in the aggregate up to the
product (rounded up to the nearest whole number) of (i) the quotient determined
by dividing (A) the aggregate number of shares of Common Stock and Common Stock
Equivalents beneficially

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owned by such Purchaser by (B) the aggregate number of shares of Common Stock
and Common Stock Equivalents beneficially owned by the Transferring Stockholder
and (ii) the total number of shares of Common Stock and Common Stock Equivalents
proposed to be Transferred by the Transferring Stockholder to the transferee in
the contemplated Transfer, and at the same price (on a per share of Common Stock
basis) as to be paid and given to the Transferring Stockholder, with an
appropriate adjustment to take into account the exercise or conversion price
payable, if any, in connection with the exercise or conversion of any Common
Stock Equivalent to be sold by the Transferring Stockholder or such Purchaser
and on substantially the same terms (other than indemnities) applicable to the
Transferring Stockholder (to the extent such terms are customary and
reasonable). In the event any proposed Transfer by the Transferring Stockholder
to which this Section 2.5 applies would result in a Change of Control (other
than a Change of Control arising pursuant to a Private Company Business
Combination Transaction with respect to which Blackstone has exercised its
waiver rights pursuant to subsection 2(h)(ii) of the Certificates of
Designations for the Preferred Stock), such Purchaser shall be deemed
immediately prior to any such proposed Transfer to beneficially own the shares
of Preferred Stock acquired by operation of Section 2(h) of the applicable
Certificates of Designations for the Preferred Stock, and shall be permitted to
exercise its rights to require the proposed transferee to purchase any such
shares of Preferred Stock (or Common Stock into which such shares of Preferred
Stock may have been converted) in accordance with this Section 2.5.

          (b)  The Transferring Stockholder shall give notice to each Purchaser
of each proposed Transfer giving rise to the rights of the Purchasers set forth
in Section 2.5(a) at least 15 Business Days prior to the proposed consummation
of such Transfer, setting forth the number of shares of Common Stock or Common
Stock Equivalents proposed to be so transferred, the name and address of the
proposed transferee, the proposed amount and form of consideration and other
terms and conditions of payment offered by the proposed transferee, including,
if applicable, a copy of the offer of the proposed transferee and a copy of the
proposed Transfer agreement and a representation that the proposed transferee
has been informed of, and agrees to comply with, the tag-along rights provided
for in this Section 2.5. The tag-along rights provided by this Section 2.5 must
be exercised by any Purchaser within 10 Business Days following receipt of the
notice required by the preceding sentence, by delivery of a written notice to
the Transferring Stockholder indicating the desire of such Purchaser to exercise
its rights and specifying the number of shares of Common Stock or Common Stock
Equivalents it desires to sell. Promptly following any such exercise, such
Purchaser shall execute the applicable Transfer agreement or other documentation
to the extent provided to such Purchaser and otherwise in compliance with this
Section 2.5. Any exercise of tag-along rights by any Purchaser hereunder shall
only become binding upon execution by such Purchaser of the applicable Transfer
agreement or other documentation.

          (c)  The Transferring Stockholder shall be entitled under this Section
2.5 to Transfer to the proposed transferee the number of shares of Common Stock
or Common Stock Equivalents equal to the excess of (x) the number referred to in
clause (ii) of Section 2.5(a) over (y) the aggregate number of shares of Common
Stock or Common Stock Equivalents set forth in the written exercise notice or
notices, if any, delivered by any Purchaser, as to which such Purchaser was
entitled to exercise its tag-along rights.

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<PAGE>

          (d)   If the proposed transferee fails to purchase shares of Common
Stock or Common Stock Equivalents from any Purchaser as to which such Purchaser
has exercised its rights under this Section 2.5, then the Transferring
Stockholder shall not be permitted to make the proposed Transfer, and any such
attempted Transfer shall be void and of no effect, as provided in Section 2.3
hereof.

          (e)   The rights granted to the Purchasers pursuant to this Section
2.5 shall not apply to any Transfer by Geneseo or Cambridge (i) to any of their
respective Affiliates in accordance with Section 2.2, (ii) in a Public Offering
or (iii) in a transaction in compliance with Rule 144 under the Securities Act.

          (f)   The rights granted to the Purchasers pursuant to this Section
2.5 shall terminate following a Public Offering at such time that Geneseo and
Cambridge shall cease to beneficially own, in the aggregate, at least 25% of the
outstanding shares of Common Stock and Common Stock Equivalents, determined on a
fully diluted basis.

          2.6   Drag-Along Rights.  (a)  If Geneseo and Cambridge receive an
                -----------------
offer (the "Drag-Along Offer") from a Person other than an Affiliate thereof (a
            ----------------
"Third Party") to purchase in a bona fide arm's length transaction all, but not
 -----------
less than all, of the shares of Common Stock then beneficially owned by Geneseo
and Cambridge and such offer is accepted by Geneseo and Cambridge in their sole
discretion, then, at the joint election of Geneseo and Cambridge, each of the
Purchasers hereby agrees that it will Transfer all of the shares of Common Stock
and Preferred Stock owned by it (including any shares of Preferred Stock
acquired by operation of Section 2(h) of the Certificates of Designations for
the Preferred Stock as a result of the Transfers to which this Section 2.6
applies) to such Third Party on substantially the same terms (other than
indemnities) of the Drag-Along Offer so accepted by Geneseo and Cambridge (to
the extent such terms are customary and reasonable), including the same per
share of Common Stock consideration; provided that:

          (i)   the price per share of Common Stock is greater than (A) if the
     Drag-Along Offer is consummated before July 12, 2002, three times $5.50
     (subject to adjustment to such price pursuant to subsections 5(e), (f),
     (g), (i) and (j) of the Certificate of Designations for the Series A-1
     Preferred Stock) or (B) if the Drag-Along Offer is consummated on or after
     July 12, 2002, four times $5.50 (subject to adjustment to such price
     pursuant to subsections 5(e), (f), (g), (i) and (j) of the Certificate of
     Designations for the Series A-1 Preferred Stock);

          (ii)  the per share price to be paid for the Preferred Stock owned by
     the Purchasers shall be equal to the per share price to be paid for the
     Common Stock multiplied by the number of shares of Common Stock into which
     each share of the Preferred Stock is then convertible;

          (iii) the consideration to be received by the Purchasers shall
     consist solely of U.S. dollars cash or Unrestricted Marketable Securities
     or any combination thereof; and

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<PAGE>

          (iv) this provision shall only apply to any shares of Preferred Stock
     once such shares have been outstanding for over one year.

          (b)  If  Geneseo and Cambridge elect to exercise their rights under
Section 2.6(a), they shall give notice (the "Drag-Along Notice") to each of the
                                             -----------------
Purchasers of any proposed Transfer giving rise to, and exercising, such rights
as soon as practicable (but in no event later than three Business Days)
following the execution of an agreement setting forth the Drag-Along Offer. The
Drag-Along Notice shall set forth the name of the proposed transferee, the
proposed amount and form of consideration and the other terms and conditions of
the offer, including a copy of the agreement setting forth the Drag-Along Offer.
If the Transfer referred to in the Drag-Along Notice is not consummated within
90 days from the date of the Drag-Along Notice, the Transferring Stockholder
must deliver another Drag-Along Notice in order to exercise its rights under
this Section 2.6 with respect to such Transfer or any other Transfer. In the
event any proposed Transfer by the Transferring Stockholder to which this
Section 2.6 applies would result in a Change of Control (other than a Change of
Control arising pursuant to a Private Company Business Combination Transaction
with respect to which Blackstone has exercised its waiver rights pursuant to
subsection 2(h)(ii) of the Certificates of Designations for the Preferred
Stock), the Purchasers shall be deemed immediately prior to any such proposed
Transfer to beneficially own the shares of Preferred Stock acquired by operation
of Section 2(h) of the applicable Certificates of Designations for the Preferred
Stock, and shall be permitted to exercise their rights to require the proposed
transferee to purchase any such shares of Preferred Stock (or Common Stock into
which such shares of Preferred Stock may have been converted) in accordance with
this Section 2.6.

          (c)  If Geneseo and Cambridge elect to exercise their rights under
Section 2.6(a), the closing of the purchase of the shares of Common Stock and/or
Common Stock Equivalents of the Purchasers with respect to which such rights
have been exercised shall take place concurrently with the closing of the
purchase of the shares of Common Stock and/or Common Stock Equivalents of all
other Persons participating in the applicable Drag-Along Offer; provided that
such closing (including the purchase of the shares of Common Stock and/or Common
Stock Equivalents of all other Persons participating in the applicable Drag-
Along Offer) may be extended by such time as any Purchaser may reasonably
require in order to obtain any approval or authorization of any Governmental
Entity or to comply with any applicable law or regulation.

          (d)  The rights granted to Geneseo and Cambridge pursuant to this
Section 2.6 shall terminate upon the earlier of (i) a Public Offering, (ii) such
time as Geneseo and Cambridge shall cease to beneficially own, in the aggregate,
at least 25% of the outstanding shares of Common Stock and (iii) the
consummation of any Business Combination Transaction resulting in a Change of
Control that results in an Automatic Conversion.  Geneseo and Cambridge shall
only be entitled to exercise their rights pursuant to this Section 2.6 if (i)
the shares of Common Stock and Common Stock Equivalents beneficially owned by
them plus (ii) all of the shares of Common Stock and Common Stock Equivalents
     ----
then beneficially owned by the Purchasers (including any shares of Preferred
Stock issuable by operation of Section 2(h) of the Certificates of Designations
for the Preferred Stock as a result of the Transfers to which this Section 2.6
applies) plus (iii) if any of Cass Communications Management, Inc., Technology
         ----
Group, LLC, Montrose Mutual PCS, Inc., Respond

                                       10
<PAGE>

Communications, Inc., Gridley Enterprises, Inc. or Timothy M. Yager, or any of
their Affiliates then holding Common Stock or Common Stock Equivalents, has
agreed to Transfer pursuant to the applicable Drag-Along Offer all of the shares
of Common Stock and Common Stock Equivalents then beneficially owned by them,
all of such shares of Common Stock or Common Stock Equivalents, equal a majority
                                                                -----
of the then outstanding shares of Common Stock on a fully diluted basis.

          SECTION 3.  BOARD OF DIRECTORS

          3.1  Board of Directors.  (a)  The parties hereto agree to cause the
               ------------------
Company Board to consist of nine directors (individually, a "Director" and,
                                                             --------
collectively, the "Directors").  The Company hereby acknowledges the rights of
                   ---------
the holders of the Preferred Stock, including Blackstone, so long as it is the
majority holder of such Preferred Stock, to designate persons to the board of
directors of the Company in accordance with the Certificates of Designations.

          (b)  In the event but only in the event holders of the Preferred Stock
are not entitled to designate any Directors under the Certificates of
Designations, then (i) for so long as Blackstone beneficially owns on an as-
converted basis 8% or more of the outstanding Common Stock, Blackstone shall be
entitled to designate two Directors, (ii) for so long as Blackstone beneficially
owns on an as-converted basis less than 8% but more than 4% of the outstanding
Common Stock, then Blackstone shall be entitled to designate one Director and
(iii) if Blackstone beneficially owns on a fully diluted basis less than 4% of
the outstanding Common Stock, then Blackstone shall not be entitled to designate
any Directors.

          (c)  In the event holders of the Preferred Stock are entitled to
designate only one Director under the Certificates of Designations, then, in
addition to the Director the holders of the Preferred Stock shall have the right
to designate, (i) for so long as Blackstone beneficially owns on an as-converted
basis 8% or more of the outstanding Common Stock, Blackstone shall be entitled
to designate one additional Director and (ii) if Blackstone beneficially owns on
an as-converted basis less than 8% of the outstanding Common Stock, then
Blackstone shall not be entitled to designate any additional Directors.

          (d)  The Stockholders agree to vote their Common Stock (or any other
voting security) in favor of any designee Director proposed by Blackstone
pursuant to Section 3.1(b) and (c) hereof. The Company and the Stockholders each
agree to take such other actions as may be necessary to implement the provisions
of this Section 3.

          (e)  The removal from the Company Board of any Director nominated to
the Company Board by Blackstone pursuant to this Section 3 without cause shall
be only upon the written request of Blackstone.  In the event that any person
designated as a Director by Blackstone hereunder for any reason ceases to serve
as a Director during such person's term of office, the resulting vacancy shall
be filled by a representative designated by Blackstone.

                                       11
<PAGE>

          (f)  The Company shall reimburse the Directors designated by
Blackstone for all reasonable out-of-pocket expenses borne by such Directors in
connection with the performance of their duties as Directors and such Directors
shall also be entitled to receive any other compensation or indemnity
arrangements which all other Directors of the Company are entitled to receive.

          (g)  If Blackstone is entitled to designate one Director pursuant to
this Section 3.1, such Director shall be designated to be a member of the class
of Directors having the longest remaining term at the time of such designation.
If Blackstone is entitled to designate two Directors pursuant to this Section
3.1, one Director shall be designated to be a member of the class of Directors
having the longest remaining term at the time of such designation and one
Director shall be designated to be a member of the class of Directors having the
second longest remaining term at the time of such designation. In the event that
Blackstone's beneficial ownership of Common Stock falls below the percentages
set forth in subsections (b) and (c) above, the Director or Directors, as
applicable, that Blackstone is no longer entitled to designate shall promptly
resign and be replaced in accordance with the Company's bylaws.

          SECTION 4.  PREEMPTION RIGHTS

          4.1  Preemptive Rights.  (a)  Until the earlier of (i) a Minimum
               -----------------
Public Offering and (ii) the consummation of a Public Company Business
Combination Transaction or a Private Company Business Combination Transaction
resulting in a Change of Control, the Company shall not, after the date of this
Agreement, issue (an "Issuance") any Securities (other than Excluded Issuances
                      --------
or the Excluded Warrants and shares of Common Stock issuable upon exercise of
the Excluded Warrants) unless, prior to such Issuance, the Company notifies each
of the Purchasers, in writing, of the proposed Issuance and grants to each of
the Purchasers the right (the "Right") to subscribe for and purchase a portion
                               -----
of such Securities proposed to be issued at the same price per share and upon
the same terms and conditions (including, in the event such Securities are
issued as a unit together with other securities, the purchase of such other
securities) as issued in the Issuance such that:

          (A)  immediately after giving effect to the Issuance and exercise of
     the Right, the shares of Common Stock beneficially owned by each of the
     Purchasers and the shares of Common Stock into which shares of Preferred
     Stock owned by each of the Purchasers are then convertible (rounded to the
     nearest whole share) on a fully diluted basis shall represent the same
     percentage of the aggregate number of shares of Common Stock outstanding on
     a fully diluted basis as was beneficially owned by such Purchaser and the
     shares of Common Stock into which shares of Preferred Stock owned by such
     Purchaser are then convertible on a fully diluted basis immediately prior
     to the Issuance; and

          (B)  in the case of an Issuance in which shares of capital stock (or
     options, warrants or other rights therefor) other than Common Stock or
     Common Stock Equivalents ("Other Capital Stock") are to be issued,  each of
                                -------------------
     the Purchasers shall have the Right to acquire a percentage of the Other
     Capital Stock to be issued in the Issuance equal to the percentage

                                       12
<PAGE>

     of shares of Common Stock on a fully diluted basis that was beneficially
     owned by such Purchaser (including shares of Common Stock into which the
     Preferred Stock owned by such Purchaser is convertible) immediately prior
     to the Issuance.

          (b)  If any Issuances are made in exchange for all or any non-cash
consideration, then, in the absence of an agreement between the Company and
Blackstone, (i) the fair market value of such non-cash consideration shall be
determined by an independent appraiser of recognized standing appointed by the
Company (subject to the approval of Blackstone (such approval not to be
unreasonably withheld)) and (ii) each of the Purchasers shall have the right, in
accordance with this Section 4.1, to subscribe for the applicable Securities by
paying cash in an amount equal to the value of any such non-cash consideration
as so determined.

          (c)  The Right may be exercised by  each of the Purchasers at any time
by written notice to the Company received by the Company within 10 Business Days
after the date on which such Purchaser receives notice from the Company of the
proposed Issuance and, if the Right is exercised, the closing of the purchase
and sale pursuant to the exercise of the Right shall occur at least 15 Business
Days (but not later than 60 days) after the Company receives notice of the
exercise of the Right concurrently with the closing of the Issuance.

          SECTION 5.  BLACKSTONE RIGHT TO CAUSE A SALE

          5.1  Redemption Request.  (a)  In the event that (i) the Company has
               ------------------
not issued Securities in Public Offerings (including one Minimum Public
Offering) resulting in gross proceeds to the Company (before deduction of
underwriting discounts and expenses of sale) of at least $50 million or (ii) a
Public Company Business Combination Transaction has not been consummated, then,
beginning on the fifth anniversary of the date hereof, Blackstone shall have the
right (which may be withdrawn at any time within five Business Days after the
determination of the Fair Market Value pursuant to Section 5.1(b) hereof) to
request that the Company repurchase for cash any or all of Blackstone's
outstanding shares of Preferred Stock and Common Stock received from the
conversion of the Preferred Stock and TCW shall have the right to participate in
any such Redemption Request with respect to a pro rata portion of the Preferred
Stock and Common Stock received from the conversion of the Preferred Stock held
by it (collectively, the "Redemption Securities") at the Fair Market Value
                          ---------------------
(determined in accordance with Section 5.1(b) below) thereof by giving the
Company a written request therefor (the "Redemption Request").
                                         ------------------

          (b)  The fair market value of any Redemption Securities shall be
determined pursuant to this Section 5.1(b).  For a period of 20 days following
the receipt of a Redemption Request by the Company, Blackstone and the Company
shall attempt in good faith to agree on the fair market value of the Redemption
Securities. Any agreement reached by Blackstone and the Company shall be final
and binding on all parties hereto. If Blackstone and the Company are unable to
reach agreement within 20 days after the receipt by the Company of the
Repurchase Request, Blackstone and the Company shall each, within 10 days
thereafter, choose one investment banker or other appraiser with experience in
valuing companies such as the Company, and the two investment

                                       13
<PAGE>

bankers or appraisers so selected shall together select a third investment
banker or appraiser similarly qualified. The three investment bankers or
appraisers shall appraise the fair market value of the Redemption Securities
that are not publicly traded, determined on the basis of an orderly, arm's
length sale (structured to produce the highest price for such securities) to a
willing, unaffiliated buyer, taking into account all relevant factors
determinative of value (but without any discount for lack of liquidity or
minority status). Within 30 days of their retention, the three investment
bankers or appraisers shall provide the written results of such appraisals to
Blackstone and, if applicable, TCW and the Company. The "Fair Market Value" of
                                                         -----------------
the Redemption Securities shall be the average of the three appraisals, and such
amount shall be final and binding on all parties hereto. The reasonable costs of
such appraisals shall be borne by the Company.

          (c)  In the event Blackstone has not withdrawn its redemption request
pursuant to Section 5.1(a) hereof, the Company shall purchase the Redemption
Securities at the Fair Market Value thereof on or prior to the twentieth
Business Day following the expiration of Blackstone's withdrawal right unless
the Company Board determines in its sole discretion that it is not in the best
interests of the Company to repurchase the Redemption Securities. In the event
the Company Board determines not to purchase the Redemption Securities on or
prior to such date or if Blackstone has withdrawn its redemption request
pursuant to Section 5.1(a) hereof, Blackstone shall have the right, subject to
the rights of Sprint Spectrum, LP and SprintCom, Inc. under the Sprint
Management Agreement (as defined in the Investment Agreement), to require a
Company Sale in accordance with Section 5.2 hereof.

          5.2  Sale of the Company.  If Blackstone exercises its rights pursuant
               -------------------
to Section 5.1(c) to effect a Company Sale, the Company  Board shall cause a
Company Sale as expeditiously as practicable (subject to the pursuit of a
favorable price), consistent with the fiduciary duties of the Company Board. If
Blackstone exercises such rights, each of Geneseo and Cambridge covenants that
it shall exercise all rights available to it as a stockholder of the Company to
effect a Company Sale as expeditiously as practicable (subject to the pursuit of
a favorable price) within six months of Blackstone's election pursuant to
Section 5.1(c) hereof, including directing their Director designees to pursue a
Company Sale or electing new Directors, if necessary, to pursue such a sale. The
parties agree that for a period of ninety days following the exercise of
Blackstone's right to cause a Company Sale, that the Company Board shall pursue
in good faith such a sale exclusively with Sprint or any of its Affiliates then
in good standing. If an agreement for a Company Sale is not reached within such
ninety day period with any of such Persons, the Company Board shall, and
Blackstone may, pursue a Company Sale with any other Persons, subject in all
cases to the rights of Sprint Spectrum, LP and SprintCom, Inc. under the Sprint
Management Agreement.

          SECTION 6.  BLACKSTONE INITIAL PUBLIC OFFERING RIGHTS

          6.1  Initial Public Offering.  If, within two years after the date
               -----------------------
hereof, a Minimum Public Offering has not occurred, then upon Blackstone's
request the Company shall use its best efforts to consummate a Minimum Public
Offering as expeditiously as possible (but in any event within 180 days).  The
Company shall comply with the terms of Section 5 of the Registration Rights

                                       14
<PAGE>

Agreement (to the extent applicable to a sale of securities by the Company) as
if such terms had been set forth herein.

          SECTION 7.  BLACKSTONE INFORMATION RIGHTS

          7.1  Information Rights.  The Company hereby agrees that for so long
               ------------------
as any Purchaser continues to hold any Securities, the Company shall, with
respect to each entity included within the definition of "Blackstone" or "TCW"
that is intended to qualify as a "venture capital operating company" within the
meaning of 29 C.F.R. (S) 2510.3-101(d) (each, a "VCOC Investor"):
                                                 -------------

          (a)    provide the VCOC Investor or its designated representative with
     (A) the right to inspect and copy the books and records of the Company and
     the Subsidiaries, (B) copies of all audited financial statements of the
     Company and the Subsidiaries and (C) copies of all materials provided to
     the Company Board;

          (b)   make appropriate officers and/or directors of the Company
     available periodically for consultation with the VCOC Investor or its
     designated representative with respect to matters relating to the business
     and affairs of the Company, including significant changes in management
     personnel and compensation of employees, introduction of new products or
     new lines of business, important acquisitions or dispositions of plants and
     equipment, significant research and development programs, the purchasing or
     selling of important trademarks, licenses or concessions or the proposed
     commencement or compromise of significant litigation;

          (c)  inform the VCOC Investor or its designated representative in
     advance with respect to any significant corporate actions, including
     extraordinary dividends, mergers, acquisitions or dispositions of assets,
     issuances of significant amounts of debt or equity and material amendments
     to the certificate of incorporation or by laws of the Company, and provide
     the VCOC Investor or its designated representative with the right to
     consult with the Company with respect to such actions; and

          (d)   provide the VCOC Investor or its designated representative with
     such other rights of consultation as may reasonably be determined by the
     VCOC Investor to be necessary to qualify its investment in the Company as a
     "venture capital investment" for purposes of the United States Department
     of Labor Regulation published at 29 C.F.R. Section 2510.3-101(d)(3)(i) (the
     "Plan Asset Regulation").

          The Company agrees to consider, in good faith, the recommendations of
each VCOC Investor or its designated representative in connection with the
matters on which it is consulted as described above, recognizing that the
ultimate discretion with respect to such matters shall be retained by the
Company in its sole discretion.

                                       15
<PAGE>

          Notwithstanding the foregoing, Blackstone acknowledges and agrees that
it and its representatives shall not have access to any confidential promotional
and marketing information and confidential results of operations of Sprint PCS.
Blackstone has reviewed the confidentiality provisions in Section 12.2 of the
Sprint Management Agreement and agrees to assist the Company in complying with
such provisions.

          SECTION 8.  BLACKSTONE BUSINESS COMBINATION RIGHTS

          8.1  Approval Rights.
               ---------------

          (a)    Change of Control Public Company Business Combination
                 -----------------------------------------------------
Transactions.  The consummation of any Public Company Business Combination
------------
Transaction which would or would reasonably be expected to result in a Change of
Control shall be subject to the prior written approval of the Blackstone
designees, if any, on the Company Board or, if Blackstone ceases to have the
right to appoint any such designees, Blackstone, unless one or more of the
following is true, in which case Blackstone shall have no approval rights with
respect to any such Public Company Business Combination Transaction:

          (i)    the Series A-2 Closing (as defined in the Investment Agreement)
     has not occurred;

          (ii)   all Preferred Stock previously issued has been converted into
     Common Stock; or

          (iii)  the consideration to be received by Blackstone in such Public
     Company Business Combination Transaction includes only cash and/or shares
     of common stock of the Public Company and implies a valuation of
     Blackstone's total investment in the Company determined at the time of the
     consummation of such transaction of greater than the greater of (A) $11.00
     per share of Common Stock (including shares of Common Stock issuable upon
     conversion of the Preferred Stock), such price being subject to adjustment
     pursuant to subsections 5(e), (f), (g), (i) and (j) of the Series A-1
     Preferred Stock Certificate of Designations and (B) an internal rate of
     return on Blackstone's investment in the Company, determined from the date
     of its investment(s) therein, equal to an annual rate of 35%. For purposes
     of determining the implied valuation of Blackstone's total investment in
     the Company, (A) the value of any consideration in the form of common stock
     shall be based on the closing public market price of such common stock on
     the trading day immediately prior to the consummation of such transaction
     and (B) internal rate of return shall mean an interest rate that, when used
     to calculate the net present value of all cash inflows (the value of the
     consideration to be received by Blackstone pursuant to the applicable
     transaction) and cash outflows (Blackstone's investment in the Company) as
     of the date of any such determination, causes such net amount to be zero,
     it being understood that Blackstone's total investment in the Company shall
     be determined without taking into account any dividends paid or accrued on
     the Preferred Stock originally issued at the Series A-1 Closing (as defined
     in the Investment Agreement) and the Series A-2 Closing or any shares of
     Common Stock

                                       16
<PAGE>

     or Preferred Stock previously sold by Blackstone (or the corresponding
     investment made by Blackstone in the Company with respect to such shares),
     but taking into account any consideration received by Blackstone in
     connection with such Public Company Business Combination Transaction in
     respect of Preferred Stock received by Blackstone as dividends and taking
     into account any and all amounts receivable by Blackstone as a special
     dividend pursuant to Section 2(h) of the Certificates of Designations for
     the Preferred Stock.

          (b)   Change of Control Private Company Business Combination
                ------------------------------------------------------
Transactions. The consummation of any Private Company Business Combination
------------
Transaction which would or would reasonably be expected to result in a Change of
Control shall be subject to the prior written approval of the Blackstone
designees, if any, on the Company Board or, if Blackstone ceases to have the
right to appoint any such designees, Blackstone, unless one or more of the
following is true, in which case Blackstone shall have no approval rights with
respect to any such Private Company Business Combination Transaction:

          (i)   the Series A-2 Closing has not occurred;

          (ii)  all Preferred Stock previously issued has been converted into
     Common Stock; or

          (iii) the consideration to be received by Blackstone in such Private
     Company Business Combination Transaction includes only cash and/or shares
     of common stock of the Private Company and implies a valuation of
     Blackstone's total investment in the Company determined at the time of the
     consummation of such transaction of greater than the greater of (A) $11.00
     per share of Common Stock (including shares of Common Stock issuable upon
     conversion of the Preferred Stock), such price being subject to adjustment
     pursuant to subsections 5(e), (f), (g), (i) and (j) of the Series A-1
     Preferred Stock Certificate of Designations and (B) an internal rate of
     return on Blackstone's investment in the Company, determined from the date
     of its investment(s) therein, equal to an annual rate of 35%. For purposes
     of determining the implied valuation of Blackstone's total investment in
     the Company, (A) the value of any consideration in the form of common stock
     shall be based on the Fair Market Value of such common stock on the day
     immediately prior to the consummation of such transaction or, so long as
     there has not been any material diminution in the value of such
     consideration prior to the date of consummation, as close thereto as
     reasonably practicable, determined in accordance with the procedures set
     forth in Section 5.1(b) and (B) internal rate of return shall mean an
     interest rate that, when used to calculate the net present value of all
     cash inflows (the value of the consideration to be received by Blackstone
     pursuant to the applicable transaction) and cash outflows (Blackstone's
     investment in the Company) as of the date of any such determination, causes
     such net amount to be zero and Blackstone's total investment in the Company
     shall be determined without taking into account any dividends paid or
     accrued on the Preferred Stock originally issued at the Series A-1 Closing
     (as defined in the Investment Agreement) and the Series A-2 Closing or any
     shares of Common Stock or Preferred Stock previously sold by Blackstone (or
     the corresponding investment made by Blackstone in the Company with

                                       17
<PAGE>

     respect to such shares), but taking into account any consideration received
     by Blackstone in connection with such Private Company Business Combination
     Transaction in respect of Preferred Stock received by Blackstone as
     dividends, and taking into account any and all amounts receivable by
     Blackstone as a special dividend pursuant to Section 2(h) of the
     Certificates of Designations for the Preferred Stock.

          (c)  Non-Change of Control Business Combination Transactions.  So long
               -------------------------------------------------------
as Blackstone and its Affiliates shall hold in the aggregate at least 2% of the
outstanding shares of Common Stock, the consummation of any Business Combination
Transaction which would not result in a Change of Control shall be subject to
the prior written approval of the Blackstone designees, if any, on the Company
Board or, if Blackstone ceases to have the right to appoint any such designees,
Blackstone.  The approval rights set forth in this clause (c) shall terminate
when all Preferred Stock previously issued has been converted into Common Stock.

          8.2  Public Company Change of Control.  Notwithstanding any other
               --------------------------------
provision  of the Transaction Agreements, upon a Change of Control pursuant to
any Public Company Business Combination Transaction, the following provisions
shall apply and compliance therewith in form and substance reasonably
satisfactory to Blackstone shall be a condition to the consummation of any such
transaction:

          (i)  subject to the terms and conditions of the Certificates of
     Designations of the Preferred Stock, the holders of the Preferred Stock
     shall be entitled to receive the special dividend set forth in Subsection
     2(h)(i) of the Certificates of Designations and all shares of Preferred
     Stock (including shares of Preferred Stock constituting the special
     dividend) shall be automatically converted into Common Stock in accordance
     with Section 5 of the Certificates of Designations; and the holders of
     shares of Common Stock issuable upon such conversion shall be entitled to
     receive the same per share consideration pursuant to any such transaction
     as received by all other holders of Common Stock;

          (ii)  if not yet terminated, satisfied or expired, the obligation of
     the Company to sell and of Blackstone and TCW to purchase the Series A-2
     Preferred Stock pursuant to the Investment Agreement shall be terminated;

          (iii) unless the Company becomes the ultimate parent entity of the
     combined businesses (defined as the beneficial owner of 50% or more of the
     voting securities of the combined businesses) as a result of any such
     transaction, the parent entity resulting from such Public Company Business
     Combination Transaction (the "Resulting Company") shall assume the
                                   -----------------
     obligations of the Company under the Registration Rights Agreement, Section
     4.01, 4.02, 4.03 and 6.01 through 6.15 of the Investment Agreement and
     Sections 2.1(c), 7.1, 10.4 and 10.6 through 10.16 of this Agreement, and
     (except as provided in clauses (iv) and (v) below, the other provisions of
     this Agreement shall terminate; and in order to give effect to the
     foregoing, at Blackstone's election, the appropriate parties shall amend
     and restate such provisions of this Agreement, the Investment Agreement and
     the Registration

                                       18
<PAGE>

     Rights Agreement as are appropriate, with references therein to the
     "Company" referring to the Resulting Company;

          (iv) (A)  Cambridge and Geneseo shall use their best efforts to obtain
     for Blackstone the right to designate at least one person to the board of
     directors of the Resulting Company (the "New Board"); (B) if Cambridge and
                                              ---------
     Geneseo obtain the right to designate two or more persons to the New Board,
     Blackstone shall be entitled to designate one of such persons or, if
     greater, 2/9ths of such number of persons; (C) if Cambridge and Geneseo
     obtain the right to designate only one person to the New Board, Cambridge
     and/or Geneseo shall be entitled to designate such person, and Blackstone
     shall be entitled in any case to designate one person to attend and
     participate as a non-voting observer at all meetings of the New Board (and
     to receive all materials and information voting members of the New Board
     receive); and (D) the provisions of Sections 3.1(d), (e), (f) and (g) of
     this Agreement shall, with such appropriate and necessary modifications,
     apply to Blackstone's right to designate any such person or persons to the
     New Board; and

          (v)  if the Company is not the Resulting Company, the rights granted
     to Blackstone pursuant to Section 2.5 of this Agreement shall nonetheless
     continue to apply to Geneseo and Cambridge and any equity securities of the
     Resulting Company received by them in any such transaction until such time
     that they cease to beneficially own, in the aggregate, 25% of the
     outstanding equity securities of the Resulting Company.

          8.3  Private Company Change of Control.  Notwithstanding any other
               ---------------------------------
provision of the Transaction Agreements, upon a Change of Control pursuant to
any Private Company Business Combination Transaction, the provisions of the
following paragraph (i) shall apply unless Blackstone makes the election
described in the following paragraph (ii). Blackstone agrees that it will either
make the election described in paragraph (ii) below, or irrevocably decline to
make such election with respect to such proposed Private Company Business
Combination Transaction, within fifteen Business Days of the Company's written
request for such decision. In either case, compliance with such provisions in
form and substance reasonably satisfactory to Blackstone shall be a condition to
the consummation of any such Private Company Business Combination Transaction.

          (i)  Subject to the terms and conditions of the Certificates of
Designations of the Preferred Stock, the holders of the Preferred Stock shall be
entitled to receive the special dividend set forth in Subsection 2(h)(i) of the
Certificates of Designations and all shares of Preferred Stock (including shares
of Preferred Stock constituting the special dividend) shall be automatically
converted into Common Stock in accordance with Section 5 of the Certificates of
Designations. The holders of shares of Common Stock issuable upon such
conversion shall be entitled to receive the same per share consideration
pursuant to any such transaction as received by all other holders of Common
Stock. In addition, the following provisions shall apply:

          (A) subject to clause (C) below, the provisions of clauses (ii)
     through (v) of Section 8.2,

                                       19
<PAGE>

          (B)  Blackstone shall have a right of first refusal (exercisable
     within fifteen Business Days of its presentation) to provide up to 50% of
     any private equity raised or proposed to be raised by the Company or the
     Resulting Company or their respective Subsidiaries at the time of, or at
     any time within eighteen months after, the entering into of any such
     Private Company Business Combination Transaction; provided that (I) the
     terms of Blackstone's right to make such investment shall be as negotiated
     with the other party providing such private equity and (II) the Company or
     the Resulting Company shall provide prior notice to Blackstone of its
     intention to raise any private equity and shall consult with Blackstone
     with respect thereto and shall provide Blackstone with the same information
     as provided to any other potential investor;

          (C)  Blackstone's right to cause a Minimum Public Offering of the
     Resulting Company pursuant to Section 6.1 of this Agreement shall continue
     to apply but shall only become exercisable after three years from the date
     of consummation of any such transaction and, if the Company is not the
     Resulting Company, the Resulting Company shall assume the obligations of
     the Company under such provision and such provision shall be deemed to
     apply to the equity securities of the Resulting Company issued as
     consideration in any such transaction; and

          (D)  if Geneseo and Cambridge obtain in any such transaction any
     stockholder rights not generally available to all stockholders (including
     any approval or veto rights but excluding any registration rights (subject
     to the Registration Rights Agreement) or rights to designate persons to the
     New Board which are provided for in Section 8.2(ii) and 8.2(iv) above),
     Blackstone shall be entitled to the same rights on a unilateral basis.

          (ii)   As an alternative to clause (i) above, Blackstone may elect to
waive in accordance with Subsection 2(h)(ii) of the Certificates of Designations
of the Preferred Stock the application of Subsection 2(h)(i) of the such
Certificates of Designations with respect to the issuance of a special dividend
upon a Change of Control pursuant to any Private Company Business Combination
Transaction, and, in such case, such provision shall apply to any subsequent
Change of Control consummated prior to July 12, 2005 and the provisions of
clause (i) above shall not apply. In such case, all of the rights and
obligations of the Company and the Stockholders pursuant to the Investment
Agreement (including, if not yet terminated, satisfied or expired, the
obligation of the Company to sell and of Blackstone and TCW to purchase the
Series A-2 Preferred Stock), the Registration Rights Agreement and the
Stockholders Agreement shall continue in full force and effect in accordance
with their respective terms and, at Blackstone's election, if the Company is not
the Resulting Company, the Resulting Company shall assume the obligations of the
Company under all or any of such agreements with such appropriate and necessary
modifications as may be reasonably agreed to by the applicable parties.

                                       20
<PAGE>

          SECTION 9.  REPRESENTATIONS AND WARRANTIES

          9.1  Representations of Each of the Parties.  Each of the parties
               --------------------------------------
hereto represents and warrants solely with respect to himself or itself to each
of the other parties hereto as follows:

          (a)  Due Organization and Good Standing.  Each party, is duly
               ----------------------------------
     organized, validly existing and in good standing under the laws of the
     jurisdiction of its organization.

          (b)  Authority Relative to This Agreement.  Each party has all
               ------------------------------------
     necessary power and authority to execute and deliver this Agreement and to
     perform its obligations hereunder. The person executing and delivering this
     Agreement on behalf of such party is duly authorized to execute and deliver
     this Agreement on behalf of such party. The execution and delivery of this
     Agreement by it has been duly and validly authorized by all requisite
     action and no other proceedings on its part are necessary to authorize this
     Agreement. This Agreement has been duly and validly executed and delivered
     by it and, assuming the due authorization, execution and delivery by the
     other parties hereto, constitutes a legal, valid and binding obligation of
     it.

          (c)  No Conflict.  The execution, delivery, and performance by it of
               -----------
     this Agreement do not and shall not violate any provision of any applicable
     law or any order of any court or other Governmental Entity or conflict with
     or constitute a default, breach, or violation of the terms, conditions, or
     provisions of any contract, agreement or instrument to which such party is
     subject which would prevent such party from performing any of its
     obligations hereunder or thereunder.

          (d)  Required Filings and Consents.  The execution and delivery by it
               -----------------------------
     of this Agreement do not, and the performance of this Agreement will not,
     require any consent, approval, authorization or permit of, or filing by it
     with or notification to, any Governmental Entity, except (i) any such
     consents, approvals, authorizations, permits, filings or notifications as
     have been already obtained or made, (ii) as disclosed in the Investment
     Agreement and schedules thereto and (iii) where failure to obtain such
     consents, approvals, authorizations or permits, or to make such filings or
     notifications, would not prevent or materially delay it from performing any
     of his or its obligations under this Agreement.

          (e)  Ownership of Stock.  Geneseo represents and warrants that (i) it
               ------------------
     is the sole record owner and a beneficial owner of 15,468,809 shares of
     Common Stock, (ii) except for a bank pledge, it has good and marketable
     title to such Common Stock, free and clear of all liens, claims, security
     interests, encumbrances and charges of any nature whatsoever, (iii) Alan C.
     Anderson is the beneficial owner of 1,598 shares of Geneseo common stock
     constituting approximately 9% of the voting power of Geneseo's
     stockholders, (iv) Alan C. Anderson's Related Parties do not beneficially
     own in the aggregate in excess of 908 shares of Geneseo common stock or
     approximately 5% of the Geneseo voting rights and (v) no other Person is
     the record or beneficial owner of a greater number of shares or percentage
     of voting power of Geneseo than Alan C. Anderson. Cambridge represents and
     warrants that (i) it is the sole record

                                       21
<PAGE>

     owner and a beneficial owner of 13,258,979 shares of Common Stock, (ii) it
     has good and marketable title to such Common Stock, free and clear of all
     liens, claims, security interests, encumbrances and charges of any nature
     whatsoever, (iii) Alan C. Anderson is the beneficial owner of 811 shares of
     Cambridge common stock constituting approximately 8.5% of the voting power
     of Cambridge's stockholders, (iv) Alan C. Anderson's Related Parties do not
     beneficially own in the aggregate in excess of 760 shares of Cambridge
     common stock or approximately 8% of the Cambridge voting rights and (v) no
     other Person is the record or beneficial owner of a greater number of
     shares or percentage of voting power of Cambridge than Alan C. Anderson.

          SECTION 10.  MISCELLANEOUS

          10.1  Additional Securities Subject to Agreement.  Each Stockholder
                ------------------------------------------
agrees that any other Securities which it shall hereafter acquire by means of a
stock split, stock dividend, distribution, exercise of stock options, or
otherwise shall be subject to the terms hereof.

          10.2  Registration and Listing.  If any shares of  Common Stock
                ------------------------
required to be reserved for purposes of conversion of the Preferred Stock as
provided in the Certificates of Designations for the Preferred Stock require
registration with or approval of any Governmental Entity under any applicable
law before such Common Stock may be issued or delivered upon conversion, the
Company will use its best efforts to cause such Common Stock to be duly
registered or approved as expeditiously as practicable, as the case may be. If
the Common Stock is quoted on or listed on any national quotation system or
securities exchange, the Company, if permitted by the rules of such system or
exchange, will quote or list and keep quoted or listed on such system or
exchange, upon official notice of issuance, from time to time upon request, all
Common Stock issuable or deliverable upon conversion of the Preferred Stock.

          10.3  Restrictions on Blackstone Investments.  Blackstone agrees that
                --------------------------------------
neither it nor any private equity funds established in parallel or in lieu of
Blackstone or any of their respective successors (collectively, the "Blackstone
                                                                     ----------
Funds") shall acquire any equity securities, or any security convertible into
-----
equity securities, pursuant to a private equity investment made after the date
hereof in any Person whose primary business is the provision of mobile wireless
telecommunication services over cellular, PCS or ESMR technologies to POPS which
overlap with greater than 30% of the POPS of the Company as of the date hereof
(a "Competing Business"); provided that this provision shall not apply if:
    ------------------

          (i)  Blackstone ceases to designate any persons to the Company Board
     and removes any then-serving person appointed by Blackstone thereon, and
     sends a notice to the Company waiving its information rights under this
     Agreement with respect to any competitively sensitive non-public
     information about the Company for as long as it holds the otherwise
     restricted investment; or

                                       22
<PAGE>

          (ii) Blackstone and the Blackstone Funds beneficially own less than
     10% of the outstanding shares or other equity securities or interests of
     any Competing Business.

In addition, Blackstone agrees that prior to any Blackstone Fund purchasing any
equity securities of any other Sprint PCS Affiliate which is a Competing
Business, it shall notify the Company of the proposed investment and, subject to
any applicable confidentiality obligations, consult with the Company as to such
investment.

The parties agree that this Section 10.3 shall not restrict in any way or be
applicable to Blackstone Mezzanine Partners L.P. or any other vehicle that has
similar business or investment activities or any successor thereto.

          10.4  Restrictions on Company Investments. The parties agree that any
                -----------------------------------
merger, consolidation sale of assets or other business combination transaction
or issuance of securities or other similar transaction by the Company or any of
its Subsidiaries that includes non-cash consideration and, in the opinion of
counsel as selected by Blackstone, would not result in the non-recognition of
taxable gain with respect to the receipt of such non-cash consideration by the
holders of the Series A-1 Preferred Stock or Series A-2 Preferred Stock, if any,
in connection with (i) any such transaction or (ii) any conversion of the Series
A-1 Preferred Stock or Series A-2 Preferred Stock, if any, thereafter will be
subject to the prior approval of Blackstone.

          10.5  Geneseo and Cambridge Approval. Geneseo and Cambridge, in their
                ------------------------------
capacity as stockholders of the Company, hereby approve the sale and issuance of
the Preferred Stock to the Purchasers.

          10.6  Injunctive Relief. The Stockholders acknowledge and agree that a
                -----------------
violation of any of the terms of this Agreement will cause the Stockholders
irreparable injury for which adequate remedy at law is not available.
Accordingly, it is agreed that each Stockholder shall be entitled to an
injunction, restraining order or other equitable relief to prevent breaches of
the provisions of this Agreement and to enforce specifically the terms and
provisions hereof in any court of competent jurisdiction in the United States or
any state thereof, in addition to any other remedy to which they may be entitled
at law or equity.

          10.7  Other Stockholders' Agreements. None of the parties hereto shall
                ------------------------------
enter into any stockholder agreement or other arrangement of any kind with any
Person with respect to any Securities which is inconsistent with the provisions
of this Agreement.

          10.8  Amendments.  This Agreement may be amended only by a written
                ----------
instrument signed by all of the parties hereto.

          10.9  Successors, Assigns and Transferees.  The provisions of this
                -----------------------------------
Agreement shall be binding upon and shall inure to the benefit of the parties
hereto, their Permitted Transferees and their respective successors and assigns,
provided that (i) no Stockholder may assign to any Permitted Transferee any of
--------
its rights hereunder other than in connection with a Transfer to such Permitted
Transferee of Securities in accordance with the provisions of this Agreement and
(ii) Blackstone

                                       23
<PAGE>

may assign all or any portion of its rights and obligations hereunder to any
transferee of its Securities (other than its rights pursuant to Section 3) and
(iii) the Company may not assign its rights hereunder without the prior consent
of each of the Stockholders.

          10.10 Notices.  All notices, requests and demands to or upon the
                -------
respective parties hereto to be effective shall be in writing (including by
telecopy), and, unless otherwise expressly provided herein, shall be deemed to
have been duly given or made when delivered by hand, or when delivered by a
recognized courier or, in the case of telecopy notice, when received, addressed
as follows to the parties hereto, or to such other address as may be hereafter
notified by the respective parties hereto:

                if to the Company:

                121 West First Street
                Suite 200
                Geneseo, IL 61254
                Attention: Timothy M. Yager
                Facsimile: (309) 945-1651

                with a copy to:

                Mayer, Brown & Platt
                190 South LaSalle Street
                Chicago, IL 60603-3444
                Attention: Paul W. Theiss, Esq.
                Facsimile: (312) 701-7711

                if to Blackstone

                c/o The Blackstone Group
                345 Park Avenue
                31/st/ Floor
                New York, NY 10154
                Attention: Michael Chae
                Facsimile: (212) 583-5712

                with a copy to:

                Simpson Thacher & Bartlett
                425 Lexington Avenue
                New York, NY 10017-3954
                Attention: Wilson S. Neely, Esq.
                Facsimile: (212) 455-2502

                                       24
<PAGE>

                if to TCW

                TCW/Crescent Mezzanine, LLC
                11100 Santa Monica Boulevard, Suite 2000
                Los Angeles, CA 90025
                Attention: John C. Rocchio
                Facsimile: (310) 235-5967

                with a copy to:

                O'Melveny & Myers LLP
                400 South Hope Street
                Los Angeles, CA 90072-2899
                Attention: Kathryn Sanders
                Facsimile: (213) 430-6407

          10.11 Integration.  This Agreement, the Investment Agreement, the
                -----------
Registration Rights Agreement, the Certificates of Designations of the Series A-
I Preferred and Series A-2 Preferred Stock of the Company and the Transaction
Fee Agreement, dated as July 12, 2000 by and between the Company and Blackstone
Management Partners III L.L.C. contain the entire understanding of the parties
with respect to the subject matter hereof and thereof.  There are no agreements,
representations, warranties, covenants or undertakings with respect to the
subject matter hereof and thereof other than those expressly set forth herein
and therein.  This Agreement supersedes all prior agreements and understandings
between the parties with respect to such subject matter.

          10.12 Consent of Blackstone.  Except as expressly set forth otherwise
                ---------------------
herein, whenever the "consent of Blackstone" or words of similar import are
used, such consent may be obtained by means of the written consent of any
Blackstone designee to the Board of Directors, or by the written consent of any
authorized representative of any of the entities included in the definition of
"Blackstone" herein.

          10.13 Severability.  Should any part of this Agreement for any reason
                ------------
be declared invalid, such decision shall not affect the validity of any
remaining portion, which remaining portion shall remain in full force and effect
as if this Agreement had been executed with the invalid portion thereof
eliminated, and it is hereby declared the intention of the parties hereto that
they would have executed the remaining portion of this Agreement without
including therein any such part or parts which may, for any reason, be hereafter
declared invalid.

          10.14 Counterparts.  This Agreement may be executed in two or more
                ------------
counterparts, and by different parties on separate counterparts each of which
shall be deemed an original, but all of which shall constitute one and the same
instrument.

                                       25
<PAGE>

          10.15 Governing Law. This Agreement shall be governed by and
                -------------
construed and enforced in accordance with the laws of the State of New York.

          10.16 Jurisdiction. The courts of the State of New York in New York
                ------------
County and the United States District Court for the Southern District of New
York shall have jurisdiction over the parties with respect to any dispute or
controversy between them arising under or in connection with this Agreement and,
by execution and delivery of this Agreement, (i) each of the parties to this
Agreement submits to the exclusive jurisdiction of those courts, including the
in personam and subject matter jurisdiction of those courts, waives any
-- --------
objections to such jurisdiction on the grounds of venue or forum non conveniens,
                                                           ----- --- ----------
the absence of in personam or subject matter jurisdiction and any similar
               -- --------
grounds, (ii) consents to service of process by mail (in accordance with Section
10.11) or any other manner permitted by law, and (iii) irrevocably agrees to be
bound by any judgment rendered thereby in connection with this Agreement.

          10.17 Mutual Waiver of Jury Trial.  THE PARTIES HERETO WAIVE ALL RIGHT
                ---------------------------
TO TRIAL BY JURY IN ANY ACTION, SUIT OR PROCEEDING BROUGHT TO ENFORCE OR DEFEND
ANY RIGHTS OR REMEDIES UNDER THIS AGREEMENT.

                                       26
<PAGE>

          IN WITNESS WHEREOF, each of the undersigned has executed this
Agreement or caused this Agreement to be executed on its behalf as of the date
first written above.

                                iPCS, INC.

                                By: /s/ Timothy M. Yager
                                    --------------------------------------------
                                    Name:  Timothy M. Yager
                                    Title: President and Chief Executive Officer

                                GENESEO COMMUNICATIONS, INC.

                                By: /s/ Alan C. Anderson
                                    --------------------------------------------
                                    Name:  Alan C. Anderson
                                    Title: President and Chief Executive Officer

                                CAMBRIDGE TELCOM, INC.

                                By: /s/ Alan C. Anderson
                                    --------------------------------------------
                                    Name:  Alan C. Anderson
                                    Title: President and Chief Executive Officer

                                      S-1
<PAGE>

                               BLACKSTONE iPCS CAPITAL PARTNERS L.P.

                               By: Blackstone Media Management Associates III,
                                   L.L.C., as general partner

                               By: /s/ Mark T. Gallogly
                                   ---------------------------------------------
                                   Name:  Mark T. Gallogly
                                   Title: Member

                               BLACKSTONE/iPCS L.L.C.

                               By: Member

                               By: /s/ Mark T. Gallogly
                                   ---------------------------------------------
                                   Name:  Mark T. Gallogly
                                   Title: Member

                               BLACKSTONE COMMUNICATIONS PARTNERS I L.P.

                               By: Blackstone Communications Management
                                   Associates I L.L.C., as general partner

                               By: /s/ Mark T. Gallogly
                                   ---------------------------------------------
                                   Name:  Mark T. Gallogly
                                   Title: Member

                                      S-2
<PAGE>

                               TCW/CRESCENT MEZZANINE PARTNERS II, L.P.
                               TCW/CRESCENT MEZZANINE TRUST II

                               By: TCW/Crescent Mezzanine II, L.P.
                                   its general partner or managing owner

                               By: TCW/Crescent Mezzanine, L.L.C.
                                   its general partner

                               By: /s/ John C. Rocchio
                                   ---------------------------------------------
                               Name:  John C. Rocchio
                               Title: Managing Director

                               TCW SHARED OPPORTUNITY FUND II, L.P.

                               By: TCW Investment Management Company
                               Its Investment Manager

                               By: /s/ John C. Rocchio
                                   ---------------------------------------------
                               Name:  John C. Rocchio
                               Title: Managing Director

                               By: /s/ Mark D. Senkpiel
                                   ---------------------------------------------
                               Name:  Mark D. Senkpiel
                               Title: Managing Director

                               SHARED OPPORTUNITY IIB, L.L.C.

                                By: TCW Asset Management Company
                                as its Investment Adviser

                               By: /s/ John C. Rocchio
                                   ---------------------------------------------
                               Name:  John C. Rocchio
                               Title: Managing Director

                               By: /s/ Mark D. Senkpiel
                                   ---------------------------------------------
                               Name:  Mark D. Senkpiel
                               Title: Managing Director

                                      S-3
<PAGE>

                               TCW SHARED OPPORTUNITY FUND III, L.P.

                               By: TCW Asset Management Company
                               Its Investment Adviser

                               By: /s/ John C. Rocchio
                                   ---------------------------------------------
                               Name:  John C. Rocchio
                               Title: Managing Director

                               By: /s/ Mark D. Senkpiel
                                   ---------------------------------------------
                               Name:  Mark D. Senkpiel
                               Title: Managing Director

                               TCW LEVERAGED INCOME TRUST, L.P.

                               By: TCW Advisers (Bermuda), Ltd.
                               as its General Partner

                               By: /s/ Mark D. Senkpiel
                                   --------------------------------------------
                               Name:  Mark D. Senkpiel
                               Title: Managing Director

                               By: TCW Investment Management Company
                               as Investment Adviser

                               By: /s/ John C. Rocchio
                                   ---------------------------------------------
                               Name:  John C. Rocchio
                               Title: Managing Director

                                      S-4
<PAGE>

                              TCW LEVERAGED INCOME TRUST II, L.P.

                              By: TCW (LINC II), L.P.
                              as its General Partner

                              By: TCW Advisers (Bermuda), Ltd.
                              its General Partner

                              By: /s/ Mark D. Senkpiel
                                  ----------------------------------------------
                              Name:  Mark D. Senkpiel
                              Title: Managing Director

                              By: TCW Investment Management Company
                              as Investment Adviser

                              By: /s/ John C. Rocchio
                                  ----------------------------------------------
                              Name:  John C. Rocchio
                              Title: Managing Director

                                      S-5
<PAGE>

                              TCW LEVERAGED INCOME TRUST IV, L.P.

                              By: TCW Asset Management Company
                              As its Investment Adviser

                              By: /s/ John C. Rocchio
                                  ----------------------------------------------
                              Name:  John C. Rocchio
                              Title: Managing Director

                              By: /s/ Mark D. Senkpiel
                                  ----------------------------------------------
                              Name:  Mark D. Senkpiel
                              Title: Managing Director

                              By: TCW (LINC IV), L.L.C.
                              As General Partner

                              By: TCW Asset Management Company
                              As its Managing Member

                              By: /s/ John C. Rocchio
                                  ----------------------------------------------
                              Name:  John C. Rocchio
                              Title: Managing Director

                              By: /s/ Mark D. Senkpiel
                                  ----------------------------------------------
                              Name:  Mark D. Senkpiel
                              Title: Managing Director

                                      S-6<PAGE>

                                                                   EXHIBIT 10.29

                         REGISTRATION RIGHTS AGREEMENT

          Registration Rights Agreement, dated as of July 12, 2000 (this
"Agreement"), among iPCS, Inc., a Delaware corporation (the "Company"),
                                                             -------
Blackstone/iPCS L.L.C., a Delaware limited liability company, Blackstone iPCS
Capital Partners L.P., a Delaware limited partnership, and Blackstone
Communications Partners I L,.P., a Delaware limited partnership (collectively
and including successors, assigns and Transferees thereof, "Blackstone"), and
                                                            ----------
TCW/Crescent Mezzanine Partners II, L.P., TCW/Crescent Mezzanine Trust II, TCW
Leveraged Income Trust, L.P., TCW Leveraged Income Trust II, L.P., TCW Leveraged
Income Trust IV, TCW Shared Opportunity Fund II, Shared Opportunity Fund IIB,
L.L.C. and TCW Shared Opportunity Fund III, L.P. (collectively and including
successors, assigns and Transferees, "TCW") (Blackstone and TCW, collectively,
                                      ---
the "Holders").
     -------

          WHEREAS, the Company, and Blackstone and TCW are parties to an
Investment Agreement, dated as of July 12, 2000, (the "Investment Agreement")
pursuant to which Blackstone and TCW are purchasing newly issued shares of
Series A-1 Convertible Participating Preferred Stock and, subject to certain
conditions, committed to purchase newly issued shares of Series A-2 Convertible
Participating Preferred Stock (collectively, the "Preferred Stock"), in each
                                                  ---------------
case convertible into shares of Common Stock (as defined below); and

          WHEREAS, as a condition to such purchases, the Company is providing
the purchasers with such registration rights described herein.

          NOW THEREFORE, the Company and Blackstone hereby agree as follows:

          1.   Definitions.  As used in this Agreement, the following terms
               -----------
shall have the following respective meanings:

          "Common Stock" means the common shares, par value $0.01 per share, of
           ------------
     the Company and any securities issued or distributed in respect thereof, or
     in substitution therefor, in connection with any stock split, dividend,
     spin-off or combination, or any reclassification, recapitalization, merger,
     consolidation, exchange or other similar reorganization or business
     combination.

          "Common Stock Equivalents" means any stock (including the Preferred
           ------------------------
     Stock), warrants, rights, calls, options, debt or other securities
     exchangeable or exercisable for or convertible into Common Stock.

          "Exchange Act" shall mean the Securities Exchange Act of 1934, as
           ------------
     amended, or any similar federal statute then in effect, and a reference to
     a particular section thereof shall be deemed to include a reference to the
     comparable section, if any, of any such similar federal statute.
<PAGE>

          "Initial Public Offering" shall mean the earlier of (i) the closing of
           -----------------------
     the first public offering of shares of Common Stock or Common Stock
     Equivalents or other equity securities by the Company or any other Person
     in a primary or secondary offering pursuant to an effective registration
     statement filed by the Company under the Securities Act or (ii) the
     effectiveness of any "shelf" registration statement pursuant to Rule 415
     under the Securities Act filed by the Company under the Securities Act
     other than, in each case, (A) any "shelf" registration pursuant to Rule 415
     under the Securities Act of the Warrants and Warrant Shares pursuant to the
     Warrant Registration Rights Agreement (as such terms are defined in the
     Purchase Agreement dated June 29, 2000 among the Company, iPCS Equipment,
     Inc., iPCS Wireless, Inc., Donaldson Lufkin & Jenrette Securities
     Corporation and TD Securities (USA) Inc. and (B) any registration under the
     Securities Act of the shares of Common Stock issuable upon exercise of any
     warrant issued in accordance with the Amended and Restated Addendum III to
     the Management Agreement (as defined in the Investment Agreement).

          "Registrable Securities" shall mean any shares of Common Stock and any
           ----------------------
     shares of Common Stock owned or to be acquired upon conversion, exercise or
     exchange of Common Stock Equivalents, in each case now or hereafter owned
     by the Holders. As to any particular Registrable Securities, once issued,
     such Registrable Securities shall cease to be Registrable Securities when
     (i) a registration statement with respect to the sale by the applicable
     Holder of such securities has become effective under the Securities Act and
     such securities have been disposed of in accordance with such registration
     statement, (ii) such securities have been distributed to the public
     pursuant to Rule 144 (or any successor provision) under the Securities Act,
     (iii) such securities have been otherwise transferred, new certificates for
     such securities not bearing a legend restricting further transfer have been
     delivered by the Company and subsequent disposition of such securities does
     not require registration or qualification of such securities under the
     Securities Act or any state securities or blue sky law then in force, or
     (iv) such securities have ceased to be outstanding.

          "Registration Expenses" shall mean all expenses incident to the
           ---------------------
     Company's performance of or compliance with this Agreement, including,
     without limitation, all SEC and stock exchange or National Association of
     Securities Dealers, Inc. (the "NASD") registration and filing fees and
                                    ----
     expenses, fees and expenses of compliance with securities or blue sky laws
     (including, without limitation, reasonable fees and disbursements of
     counsel for any underwriters in connection with blue sky qualifications of
     the Registrable Securities), rating agency fees, printing expenses,
     messenger, telephone and delivery expenses, the fees and expenses incurred
     in connection with the listing of the securities to be registered on any
     securities exchange or national market system, fees and disbursements of
     counsel for the Company and all independent certified public accountants
     (including the expenses of any annual audit, special audit and "cold
     comfort" letters required by or incident to such performance and
     compliance), securities laws liability insurance (if the Company so
     desires), the fees and disbursements of underwriters (including, without
     limitation, all fees and expenses of any "qualified independent
     underwriter" required by the rules of the NASD)

                                       2
<PAGE>

     customarily paid by issuers or sellers of securities (excluding, for the
     sake of clarity, the fees and expenses of counsel), the expenses
     customarily borne by the issuers of securities in a "road show"
     presentation to potential investors, the reasonable fees and disbursements
     of any Holder's counsel, the reasonable fees and expenses of any special
     experts retained by the Company in connection with such registration, fees
     and expenses of other persons retained by the Company (but not including
     any underwriting discounts or commissions (which shall be paid or borne by
     the selling Holder) or transfer taxes, if any, attributable to the sale of
     Registrable Securities) and other reasonable out-of-pocket expenses of the
     Holder.

          "SEC" shall mean the Securities and Exchange Commission or any other
           ---
     federal agency at the time administering the Securities Act or the Exchange
     Act.

          "Securities Act" shall mean the Securities Act of 1933, as amended, or
           --------------
     any similar federal statute then in effect, and a reference to a particular
     section thereof shall be deemed to include a reference to the comparable
     section, if any, of any such similar federal statute.

          "Transferee" means any Person (as defined in the Investment Agreement)
           ----------
     to whom any Holder or any Transferee thereof transfers Registrable
     Securities.

          2.   Demand Registration.
               -------------------

          (a) Request by Blackstone.  Upon the written request of Blackstone
              ---------------------
at any time after an Initial Public Offering requesting that the Company effect
the registration under the Securities Act of all or part of the Registrable
Securities and specifying the intended method of disposition thereof, the
Company will use its reasonable best efforts to effect the registration under
the Securities Act of such Registrable Securities (which registration shall also
include such Registrable Securities requested by TCW to be included in such
registration request made by Blackstone).  Blackstone and the Company shall
consult with one another at the beginning of, and throughout, the registration
process to coordinate the timing of the proposed offering, among other things
with respect to the existence of any material business combination discussions
that may be ongoing.

          (b) Registration Statement Form.  If any registration requested
              ---------------------------
pursuant to this Section 2 which is proposed by the Company to be effected by
the filing of a registration statement on Form S-3 (or any successor or similar
short-form registration statement) shall be in connection with an underwritten
public offering, and if the managing underwriter shall advise the Company in
writing that, in its opinion, the use of another form of registration statement
is of material importance to the success of such proposed offering, then such
registration shall be effected on such other form.

The Company agrees to include in any registration statement all information
which, in the opinion of counsel to the underwriters, if any, Blackstone and the
Company is required to be included.

          (c) Effective Registration Statement.  A registration requested
              --------------------------------
pursuant to this Section 2 shall not be deemed to have been effected:

                                       3
<PAGE>

          (i)   unless a registration statement with respect thereto has become
effective and remained effective in compliance with the provisions of the
Securities Act for at least 6 months with respect to the disposition of all
Registrable Securities covered by such registration statement until such time as
all of such Registrable Securities have been disposed of in accordance with the
intended methods of disposition thereof set forth in such registration
statement, other than primarily as a result of acts or omissions of any selling
Holder or any authorized agent thereof;

          (ii)  if after it has become effective, such registration is
interfered with by any stop order, injunction or other order or requirement of
the SEC or other Governmental Entity (as defined in the Investment Agreement)
for any reason not attributable to Blackstone or any of its Affiliates and has
not thereafter become effective; or

          (iii) if the conditions to closing specified in the underwriting
agreement, if any, entered into in connection with such registration are not
satisfied or waived.

          (d) Shelf Registration.  Blackstone shall be permitted to request
              ------------------
that any registration under this Section 2 be made under Rule 415 under the
Securities Act (the "Shelf Registration"). The Company shall use its reasonable
                     ------------------
best efforts to keep the Shelf Registration continuously effective for the
period beginning on the date on which the Shelf Registration is declared
effective and ending on the first date that there are no Registrable Securities
covered by such registration. During the period during which the Shelf
Registration is effective, the Company shall supplement or make amendments to
the Shelf Registration, if required by the Securities Act or if reasonably
requested by Blackstone or an underwriter of Registrable Securities, including
to reflect any specific plan of distribution or method of sale, and shall use
its reasonable best efforts to have such supplements and amendments declared
effective, if required, as soon as practicable after filing.

          (e) [Intentionally omitted]

          (f) Priority in Requested Registrations.  If a requested
              -----------------------------------
registration pursuant to this Section 2 involves an underwritten offering and
the managing underwriter advises the Company and the Holders in writing that, in
its opinion, the number of securities requested to be included in such
registration by all other holders (including securities of the Company which are
not Registrable Securities and which the holder thereof has the right to include
in any such registration) exceeds the largest number of securities which can be
sold without reasonably expecting to have an adverse effect on such offering,
including the price at which such securities can be sold, the number of such
securities to be included in such registration shall be reduced to such extent,
and the Company shall include in such registration such maximum number of
securities as follows:  (i) first, all the Registrable Securities requested to
be included in such registration by the Holders, (ii) second, to the extent that
the number of Registrable Securities which the Holders have requested to be
included in such registration is less than the number of equity securities which
the Company has been advised can be sold in such offering without having the
adverse effect referred to above, all the securities which the Company proposes
to sell for its own account, and (iii) third, to the extent that the number of
securities which the Holders have requested to be included in such registration
and the number of equity securities which the Company proposes to sell for its
own account is, in the aggregate, less

                                       4
<PAGE>

than the number of securities which the Company has been advised can be sold in
such offering without having the adverse effect referred to above, the number of
securities requested to be included in such registration by all other holders
thereof pursuant to this Section 2 shall be limited to such extent, and, subject
to any rights of such other holders, shall be allocated pro rata among all such
holders on the basis of the relative number of such securities then held by each
such holder; provided that any such amount thereby allocated to any such holder
that exceeds such holder's request shall be reallocated among the remaining
requesting holders in like manner. If any Holder advises the managing
underwriter of any underwritten offering that the Registrable Securities and
other securities covered by the registration statement cannot be sold in such
offering within a price range acceptable to such Holder, then such Holder shall
have the right to exclude its Registrable Securities from registration.

          (g) Postponements in Requested Registrations.  (i) If, upon receipt
              ----------------------------------------
of a registration request pursuant to Section 2(a), the Company is advised in
writing by a nationally recognized investment banking firm selected by the
Company that, in such firm's opinion, a registration by the Company at the time
and on the terms requested would adversely affect any public offering of
securities of the Company (other than in connection with employee benefit and
similar plans, in connection with the Sprint warrants or in connection with the
high yield warrants) (a "Company Offering") with respect to which the Company
                         ----------------
has commenced preparations for a registration prior to the receipt of a
registration request pursuant to Section 2(a) and the Company furnishes
Blackstone with a certificate signed by the Chief Executive Officer or Chief
Financial Officer of the Company to such effect (the "Transaction Delay Notice")
                                                      ------------------------
promptly after such request, the Company shall not be required to effect a
registration pursuant to Section 2(a) until the earliest of (A) 90 days after
the completion of such Company Offering, (B) promptly after the abandonment of
such Company Offering or (C) 90 days after the date of the Transaction Delay
Notice; provided, however, that in any event the Company shall not be required
to effect any registration prior to the termination, waiver or reduction of any
"blackout period" required by the underwriters to be applicable to Blackstone in
connection with any Company Offering.

          (ii)  If upon receipt of a registration request pursuant to Section
2(a) or while a registration request pursuant to Section 2(a) is pending, the
Company determines in its good faith judgment after consultation with its
securities counsel that the filing of a registration statement or any amendment
thereto would require disclosure of material information which the Company has a
bona fide business purpose for preserving as confidential and the Company
provides Blackstone written notice (the "Information Delay Notice" and, together
                                         ------------------------
with the Transaction Delay Notice, the "Delay Notice") thereof promptly after
                                        ------------
the Company makes such determination, which shall be made promptly after the
receipt of any request, the Company shall not be required to comply with its
obligations under Section 2(a) until the earlier of (A) the date upon which such
material information is disclosed to the public or ceases to be material or (B)
90 days after Blackstone's receipt of such notice.

          (iii) Notwithstanding the foregoing provisions of this Section 2(f),
the Company shall be entitled to serve only one Delay Notice (A) within any
period of 120 consecutive days or (B) with respect to any two consecutive
registrations requested pursuant to Section 2(a).

                                       5
<PAGE>

          (h) Limitations on Registration on Request.  Notwithstanding anything
              --------------------------------------
in this Section 2 to the contrary, in no event will Blackstone be entitled to
more than three registrations in the aggregate pursuant to Section 2(a), unless
either (i) a registration so requested is not deemed to have been effected
pursuant to Section 2(c) or (ii) the number of Registrable Securities included
by Blackstone in such registration and sold pursuant thereto is less than 90% of
the number of shares of Registrable Securities sought to be included by
Blackstone in such registration.

          (i) Expenses.  The Company will pay all Registration Expenses in
              --------
connection with the registrations requested pursuant to Section 2(a).

          (j) Selection of Underwriters.  If in any requested registration
              -------------------------
pursuant to Section 2 Blackstone requests that such registration shall be in the
form of an underwritten offering, such offering shall be an underwritten
offering and the Company, in consultation with Blackstone, shall have the right
to select any investment banker and manager or co-managers to administer the
offering (subject to the approval of Blackstone (such approval not to be
unreasonably withheld)). The Company shall (together with Blackstone) enter into
an underwriting agreement in customary form with the underwriter or underwriters
selected for such underwriting, as well as all other documents customary in
similar offerings, including, without limitation, underwriting agreements,
custody agreements, powers of attorney, and indemnification agreements.

          3.   Incidental Registration.
               -----------------------

          (a)  Rights to Include Registrable Securities. If the Company proposes
               ----------------------------------------
to register (other than pursuant to Section 2 hereof) any of its equity
securities under the Securities Act (other than a registration on Form S-8, S-4
or any successor or similar forms), whether or not for sale for its own account,
at any time after an Initial Public Offering (other than (i) a registration
relating to an Initial Public Offering, (ii) the registration of the Sprint
warrants exclusively and (iii) the registration of the high yield warrants
exclusively), then the Company will each such time, subject to the provisions of
Section 3(b) hereof, give prompt written notice to the Holders of its intention
to do so and of Holders' rights under this Section 3, at least 15 business days
prior to the anticipated filing date of the registration statement relating to
such registration. Such notice shall offer the Holders the opportunity to
include in such registration statement such number of Registrable Securities as
each Holder may request. Upon the written request any Holder made within 10
business days after the receipt of the Company's notice (which request shall
specify the number of Registrable Securities intended to be disposed of by such
Holder), the Company shall use its reasonable best efforts to effect the
proposed registration under the Securities Act of all Registrable Securities
which the Company has been so requested to register by such Holder to the extent
requisite to permit the disposition of the Registrable Securities so to be
registered; provided that (i) if such registration involves an underwritten
offering, any such Holder must sell its Registrable Securities to the
underwriters selected by the Company on the same terms and conditions as apply
to the Company (except that indemnification obligations of any such Holder shall
be limited to those obligations set forth in Section 6 hereof) and (ii) if, at
any time after giving written notice of its intention to register any securities
pursuant to this Section 3(a) and prior to the effective date of the
registration statement filed in connection with such registration, the Company
shall determine for

                                       6
<PAGE>

any reason not to register such securities, the Company shall give written
notice to each such Holder and, thereupon, shall be relieved of its obligation
to register any Registrable Securities in connection with such registration. If
a registration pursuant to this Section 3(a) involves an underwritten public
offering, any such Holder may elect, in writing prior to the effective date of
the registration statement filed in connection with such registration, not to
register such securities in connection with such registration. No registration
effected under this Section 3 shall relieve the Company of its obligations to
effect registrations upon request under Section 2 hereof. The Company will pay
all Registration Expenses in connection with each registration of Registrable
Securities requested pursuant to this Section 3.

          (b)  Priority in Incidental Registrations.  (i) Subject to paragraph
               ------------------------------------
(ii) below, if a registration pursuant to this Section 3 involves an
underwritten offering and the managing underwriter advises the Company in
writing that, in its opinion, the number of equity securities (including all
Registrable Securities) which the Company, the Holders and any other persons
intend to include in such registration exceeds the largest number of securities
which can be sold without reasonably expecting to have an adverse effect on such
offering, including the price at which such securities can be sold, the number
of such securities to be included in such registration shall be reduced to such
extent, and the Company will include in such registration such maximum number of
securities as follows:  (A) if such registration is initiated during the
eighteen month period following an Initial Public Offering, (I) first, all the
securities the Company proposes to sell for its own account in such
registration, (II) second, to the extent that the number of securities which the
Company proposes to sell for its own account pursuant to Section 3(a) hereof is
less than the number of equity securities which the Company has been advised can
be sold in such offering without having the adverse effect referred to above,
all Registrable Securities requested to be included in such registration by the
Holders shall be limited to such extent and shall be allocated pro rata among
such Holders on the basis of the relative number of Registrable Securities then
held by each such Holder, provided that any such amount thereby allocated to any
such Holder that exceeds such Holder's request shall be reallocated among the
remaining requesting Holders in like manner and (III) third, to the extent that
the number of equity securities which the Company proposes to sell for its own
account and the Registrable Securities which the Holders have requested to be
included in such registration pursuant to Section 3(a) hereof is, in the
aggregate, less than the number of securities which the Company has been advised
can be sold in such offering without having the adverse effect referred to
above, the number of such securities requested to be included in such
registration by the holders thereof shall be limited to such extent and, subject
to any rights of such holders, shall be allocated pro rata among all such
holders on the basis of the relative number of such securities then held by each
such holder; provided, that any such amount thereby allocated to any such holder
that exceeds such holder's request shall be reallocated among the remaining
requesting holders in like manner or (B) if such registration is initiated after
the expiration of the eighteen month period following an Initial Public
Offering, (I) first, all the securities the Company proposes to sell for its own
account and (II) second, to the extent that the number of securities which the
Company proposes to sell for its own account pursuant to Section 3(a) hereof is
less than the number of equity securities which the Company has been advised can
be sold in such offering without having the adverse effect referred to above,
the aggregate of the number of Registrable Securities requested to be included
in such registration by the Holder and the number of such

                                       7
<PAGE>

securities requested to be included in such registration by other holders shall
be limited to such extent, and shall be allocated pro rata among the Holder and
all such holders on the basis of the relative number of such securities then
held by the Holder and each such holder; provided, that any such amount thereby
allocated to each Holder or any such other holder that exceeds such Holder's or
such holder's request, respectively, shall be reallocated among the Holders and
the remaining requesting holders in like manner, as applicable.

          (ii) If any holder of Common Stock, Common Stock Equivalents or other
equity securities of the Company other than Blackstone makes a requested or
demand registration, other than in connection with the registration relating to
the Sprint warrants exclusively or the high yield warrants exclusively (the
"Requesting Holder") and such requested or demand registration involves an
underwritten offering and the managing underwriter advises the Company in
writing that, in its opinion, the number of securities requested to be included
in such registration (including Registrable Securities) exceeds the largest
number of securities which can be sold without reasonably expecting to have an
adverse effect on such offering, including the price at which such securities
can be sold, the number of such securities to be included in such registration
shall be reduced to such extent, and the Company shall include in such
registration such maximum number of securities as follows: (A) first, the
number of such securities requested to be included in such registration by the
Requesting Holder and the Holders shall be limited to such extent, and shall be
allocated pro rata between them on the basis of the relative number of such
securities then held by the Requesting Holder and the requesting Holders;
provided that any such amount thereby allocated to any such holder that exceeds
such holder's request shall be reallocated to the other remaining Requesting
Holders and requesting Holders, and (B) second, to the extent that the number of
securities which the Requesting Holder and the Holders have requested to be
included in such registration is less than the number of securities which the
Company has been advised can be sold in such offering without having the adverse
effect referred to above, the number of securities requested to be included in
such registration by all other holders thereof; provided that, the number of
Registrable Securities that can be registered by such other holders shall be
limited to such extent, and, subject to any rights of such other holders, shall
be allocated pro rata among all such holders on the basis of the relative number
of such securities then held by each such holder; and provided further that any
such amount thereby allocated to any such holder that exceeds such holder's
request shall be reallocated among the remaining requesting holders in like
manner.

          4.   Holdback Agreements.
               -------------------

          (a)  Restrictions on Public Sale by Blackstone.  So long as Blackstone
               -----------------------------------------
owns Registrable Securities representing not less than 5% of the outstanding
Common Stock, if any registration of Common Stock shall be in connection with an
underwritten public offering, the Holders agree not to effect any public sale or
distribution, including any sale pursuant to Rule 144 under the Securities Act,
of any Registrable Securities, and not to effect any such public sale or
distribution of other  equity securities of the Company or of any securities
convertible into or exchangeable or exercisable for any other equity securities
of the Company (in each case, other than as part of such underwritten public
offering) during the 15 days prior to, and during such period as the managing
underwriter may request (not to exceed 180 days) beginning on, the closing date
of

                                       8
<PAGE>

the sale of the Common Stock pursuant to an effective registration statement,
except as part of such registration.

          (b)  Restrictions on Public Sale by the Company and Others.  If any
               -----------------------------------------------------
registration of Registrable Securities shall be made in connection with an
underwritten public offering, the Company agrees (i) not to effect any public
sale or distribution of any Common Stock, Common Stock Equivalents or other
equity securities or of any security convertible into or exchangeable or
exercisable for any Common Stock, Common Stock Equivalents or other equity
securities of the Company (other than in connection with an employee stock
option or other benefit plan) during the 15 days prior to, and during the 180-
day period beginning on, the closing date of the sale of the Registrable
Securities pursuant to an effective registration statement (except as part of
such registration) and (ii) that any agreement entered into after the date of
this Agreement pursuant to which the Company issues or agrees to issue any
privately placed Common Stock, Common Stock Equivalents or other equity
securities shall contain a provision under which holders of such securities
agree not to effect any public sale or distribution of any such securities
during the period referred to in the foregoing clause (i), including any sale
pursuant to Rule 144 under the Securities Act (except as part of such
registration, if permitted).

          5.   Registration Procedures.
               -----------------------

          If and whenever the Company is required to use its reasonable best
efforts to effect or cause the registration of any Registrable Securities under
the Securities Act as provided in this Agreement, the Company will, as
expeditiously as possible:

          (a)  use its reasonable best efforts to prepare and file with the SEC
     within 60 days (or, for registration on a Form S-3 or any similar short-
     form registration statement, 30 days), after receipt of a request for
     registration with respect to such Registrable Securities, a registration
     statement on any form for which the Company then qualifies or which counsel
     for the Company shall deem appropriate, and which form shall be available
     for the sale of the Registrable Securities in accordance with the intended
     methods of distribution thereof, and use its reasonable best efforts to
     cause such registration statement to become and remain effective as
     promptly as practicable, subject to the right Blackstone to defer the
     Company's request for the acceleration of effectiveness of any such
     registration statement as may be necessary to accommodate the anticipated
     timetable for such offering; provided that before filing with the SEC a
     registration statement or prospectus or any amendments or supplements
     thereto, the Company will (i) furnish to the selling Holders copies of the
     form of preliminary prospectus proposed to be filed and furnish to counsel
     of the selling Holders copies of all such documents proposed to be filed,
     which documents will be subject to the review of such counsel and shall not
     be filed without the approval of such counsel and (ii) notify the selling
     Holders of any stop order issued or threatened by the SEC and take all
     reasonable actions required to prevent the entry of such stop order or to
     remove it if entered;

          (b)  subject to Section 2(d) in the case of a Shelf Registration,
     prepare and file with the SEC such amendments and supplements to such
     registration statement and the

                                       9
<PAGE>

     prospectus used in connection therewith as may be necessary to keep such
     registration statement effective for a period of not less than 180 days or
     such shorter period which will terminate when all Registrable Securities
     covered by such registration statement have been sold (but not before the
     expiration of the 90-day period referred to in Section 4(3) of the
     Securities Act and Rule 174 thereunder, if applicable), and comply with the
     provisions of the Securities Act with respect to the disposition of all
     securities covered by such registration statement during such period in
     accordance with the intended methods of disposition by the sellers thereof
     set forth in such registration statement;

          (c)  promptly furnish to each Holder and each underwriter, if any, of
     Registrable Securities covered by such registration statement such number
     of copies of such registration statement, each amendment and supplement
     thereto (in each case including all exhibits thereto), the prospectus
     included in such registration statement (including each preliminary
     prospectus), in conformity with the requirements of the Securities Act,
     copies of any correspondence with the SEC or its staff relating to the
     registration statement and such other documents as any Holder or
     underwriter may reasonably request in order to facilitate the disposition
     of the Registrable Securities by Blackstone;

          (d)  use its reasonable best efforts to register or qualify such
     Registrable Securities under such other securities or blue sky laws of such
     jurisdictions as any Holder or each underwriter, if any, reasonably
     requests and do any and all other acts and things which may be reasonably
     necessary or advisable to enable such Holder and each underwriter, if any,
     to consummate the disposition in such jurisdictions of the Registrable
     Securities; provided that the Company will not be required to (i) qualify
     generally to do business in any jurisdiction where it would not otherwise
     be required to qualify but for this paragraph (d), (ii) subject itself to
     taxation in any such jurisdiction or (iii) consent to general service of
     process in any such jurisdiction;

          (e)  use its reasonable best efforts to cause the Registrable
     Securities covered by such registration statement to be registered with or
     approved by such other Governmental Entities as may be necessary by virtue
     of the business and operations of the Company to enable the selling Holders
     to consummate the disposition of such Registrable Securities;

          (f)  immediately notify the selling Holders (the facts prompting which
     notification the selling Holders shall keep confidential) at any time when
     a prospectus relating thereto is required to be delivered under the
     Securities Act, of the happening of any event which comes to the Company's
     attention if as a result of such event the prospectus included in such
     registration statement contains an untrue statement of a material fact or
     omits to state any material fact required to be stated therein or necessary
     to make the statements therein not misleading and the Company will promptly
     prepare and furnish to the selling Holders a supplement or amendment to
     such prospectus so that, as thereafter delivered to the purchasers of such
     Registrable Securities, such prospectus will not contain an untrue
     statement of a material fact or omit to state any material fact required to
     be stated therein or necessary to make the statements therein not
     misleading;

                                       10
<PAGE>

          (g)   use its reasonable best efforts to prevent the issuance of and
     obtain the withdrawal of any stop order suspending the effectiveness of a
     registration statement relating to the Registrable Securities or of any
     order preventing or suspending the use of any preliminary or final
     prospectus at the earliest practicable moment;

          (h)   if requested by the managing underwriter or underwriters or any
     Holder, immediately incorporate in a prospectus supplement or post-
     effective amendment such information as the managing underwriters and each
     applicable selling Holder agree should be included therein relating to the
     plan of distribution with respect to such Registrable Securities,
     including, without limitation, information with respect to the number of
     Registrable Securities being sold to such underwriters, the purchase price
     being paid therefor by such underwriters and with respect to any other
     terms of the underwritten (or best efforts underwritten) offering of the
     Registrable Securities to be sold in such offering; and make all required
     filings of such prospectus supplement or post-effective amendment as soon
     as notified of the matters to be incorporated in such prospectus supplement
     or post-effective amendment;

          (i)   cooperate with the Holders and the managing underwriters, if
     any, to facilitate the timely preparation and delivery of certificates
     representing Registrable Securities to be sold and not bearing any
     restrictive legends; and enable such Registrable Securities to be in such
     denominations and registered in such names as the managing underwriters may
     request at least three business days prior to any sale of the Registrable
     Securities to the underwriters;

          (j)   use its reasonable best efforts to cause all such Registrable
     Securities to be listed on a national securities exchange or quotation
     system, and on each securities exchange or quotation system on which
     similar securities issued by the Company are then listed, and enter into
     such customary agreements including a listing application and
     indemnification agreement in customary form, provided that the applicable
     listing requirements are satisfied, and to provide a transfer agent and
     registrar for such Registrable Securities covered by such registration
     statement no later than the effective date of such registration statement;

          (k)   enter into such customary agreements (including an underwriting
     agreement in customary form) and take all such other actions as Blackstone
     or the underwriters, if any, reasonably request in order to expedite or
     facilitate the disposition of such Registrable Securities, including
     customary indemnification and making appropriate members of senior
     management of the Company available (subject to consulting with them in
     advance as to schedule) for customary participation in "road show"
     presentations to potential investors;

          (l)   make available for inspection by the Holders, any underwriter
     participating in any disposition pursuant to such registration statement,
     and any attorney, accountant or other agent retained by any Holder or
     underwriter (collectively, the "Inspectors"), all financial and other
     records, pertinent corporate documents and properties of the Company and
     its subsidiaries, if any, as shall be reasonably necessary to enable them
     to exercise their due diligence responsibility, and cause the Company's and
     its subsidiaries' officers, directors

                                       11
<PAGE>

     and employees to supply all information and respond to all inquiries
     reasonably requested by any such Inspector in connection with such
     registration statement;

          (m)  use its reasonable best efforts to obtain (i) an opinion or
     opinions of counsel to the Company and (ii) a "cold comfort" letter or
     letters from the Company's independent public accountants in customary form
     and covering such matters of the type customarily covered by opinions and
     "cold comfort" letters as Blackstone or the underwriter requests;

          (n)  otherwise use its reasonable best efforts to comply with all
     applicable rules and regulations of the SEC, and make available to its
     security holders, within the required time periods, an earnings statement
     covering a period of at least twelve months, beginning with the first month
     after the effective date of the registration statement (as the term
     "effective date" is defined in Rule 158(c) under the Securities Act), which
     earnings statement shall satisfy the provisions of Section 11(a) of the
     Securities Act and Rule 158 thereunder or any successor provisions thereto;

          (o)  promptly prior to the filing of any document which is to be
     incorporated by reference into the registration statement or the prospectus
     (after initial filing of the registration statement), provide copies of
     such document to counsel to the selling Holders and to the managing
     underwriters, if any, make the Company's representatives available for
     discussion of such document and make such changes in such document prior to
     the filing thereof as counsel for the selling Holders may request;

          (p)  promptly notify the selling Holders, counsel for the selling
     Holders and the managing underwriter or agent, (i) when the registration
     statement, or any post-effective amendment to the registration statement,
     shall have become effective, or any supplement to the prospectus or any
     amendment to the prospectus shall have been filed, (ii) of the receipt of
     any comments from the SEC, (iii) of any request of the SEC to amend the
     registration statement or amend or supplement the prospectus or for
     additional information, and (iv) of the issuance by the SEC of any stop
     order suspending the effectiveness of the registration statement or of any
     order preventing or suspending the use of any preliminary prospectus, or of
     the suspension of the qualification of the registration statement for
     offering or sale in any jurisdiction, or of the institution or threatening
     of any proceedings for any of such purposes; and

          (q)  cooperate with the selling Holders and each underwriter or agent
     participating in the disposition of such Registrable Securities and their
     respective counsel in connection with any filings required to be made with
     or any other securities exchange and/or the NASD.

          It shall be a condition precedent to the obligation of the Company to
take any action pursuant to this Agreement in respect of the securities which
are to be registered at the request of any Holder that such Holder shall furnish
to the Company such information regarding the securities held by such Holder and
the intended method of disposition thereof as the Company shall reasonably
request in connection with such registration.

                                       12
<PAGE>

          Each Holder agrees that, upon receipt of any notice from the Company
of the happening of any event of the kind described in Section 5(f) hereof, such
Holder will forthwith discontinue disposition of Registrable Securities pursuant
to the registration statement covering such Registrable Securities until
Blackstone receives the copies of the prospectus supplement or amendment
contemplated by Section 5(f) hereof, and, if so directed by the Company, such
Holder will deliver to the Company (at the Company's expense) all copies, other
than permanent file copies, then in such Holder's possession, of the prospectus
covering such Registrable Securities current at the time of receipt of such
notice. In the event the Company shall give any such notice, the period
mentioned in Section 5(b) hereof shall be extended by the greater of (i) three
months or (ii) the number of days during the period from and including the date
of the giving of such notice pursuant to Section 5(f) hereof to and including
the date when such Holder shall have received the copies of the prospectus
supplement or amendment contemplated by Section 5(f) hereof.

          6.   Indemnification.
               ---------------

          (a)  Indemnification by the Company.  In the event of any registration
               ------------------------------
of any Registrable Securities under the Securities Act pursuant to Section 2 or
3 hereof, the Company will, and it hereby does, indemnify and hold harmless, to
the full extent permitted by law, each Holder, their directors and officers,
employees, stockholders, general partners, limited partners, members, advisory
directors and managing directors (and directors, officers, stockholders, general
partners, limited partners, members, advisory directors, managing directors and
controlling persons thereof), each other person who participates as an
underwriter in the offering or sale of such securities and each other person, if
any, who controls, is controlled by or is under common control with any Holder
or any such underwriter within the meaning of the Securities Act, against any
and all losses, claims, damages or liabilities, joint or several, and expenses
(including any amounts paid in any settlement effected with the Company's
consent) to which such Holder, any such director, or officer, employee,
stockholder, general or limited partner, member, or advisory or managing
director or any such underwriter or controlling person may become subject under
the Securities Act, state securities or blue sky laws, common law or otherwise,
insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) or expenses arise out of or are based upon (i)
any untrue statement or alleged untrue statement of any material fact contained,
on the effective date thereof, in any registration statement under which such
Registrable Securities were registered under the Securities Act, any
preliminary, final or summary prospectus contained therein, or any amendment or
supplement thereto or (ii) any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading (in the case of a prospectus, in light of the
circumstances under which they are made), and the Company will reimburse each
Holder and each such director, officer, employee, general partner, limited
partner, advisory director, managing director or underwriter and controlling
person for any legal or any other expenses reasonably incurred by them as such
expenses are incurred in connection with investigating or defending such loss,
claim, liability, action or proceeding; provided that the Company shall not be
liable in any such case to the extent that any such loss, claim, damage,
liability (or action or proceeding in respect thereof) or expense arises out of
or is based upon any untrue statement or alleged untrue statement or omission or
alleged omission made in such registration statement or amendment or supplement
thereto or in any such preliminary, final or

                                       13
<PAGE>

summary prospectus in reliance upon and in conformity with written information
furnished to the Company through an instrument duly executed by such Holder or
any such director, officer, employee, general or limited partner, managing
director or underwriter specifically stating that it is for use in the
preparation thereof; provided, further, however, that the Company shall not be
required to indemnify any such Person if such untrue statement or omission or
alleged untrue statement or omission was contained or made in any preliminary
prospectus and corrected in the final prospectus or any amendment or supplement
thereto and the final prospectus does not contain any other untrue statement or
omission or alleged untrue statement or omission of a material fact that was the
subject matter of the related proceeding and any such loss, liability, claim,
damage or expense suffered or incurred by such indemnified Person resulted from
any action, claim or suit by any Person who purchased Registrable Securities
which are the subject thereof from such indemnified Person and it is established
in the related proceeding that such indemnified Person failed to deliver or
provide a copy of the final prospectus (as amended or supplemented) to such
Person with or prior to the confirmation of the sale of such Registrable
Securities sold to such Person if required by applicable law, unless such
failure to deliver or provide a copy of the final prospectus (as amended or
supplemented) was a result of noncompliance by the Company with this Section 6
or as a result of the failure of the Company to provide such final prospectus.
Such indemnity shall remain in full force and effect regardless of any
investigation made by or on behalf of each Holder or any such director, officer,
employee, general partner, limited partner, managing director, underwriter or
controlling person and shall survive the transfer of such securities by any
Holder.

          (b)  Indemnification by Holders and Underwriters.  Each Holder and any
               -------------------------------------------
underwriter will, and they hereby do, indemnify and hold harmless (in the same
manner and to the same extent as set forth in subdivision (a) of this Section 6)
the Company and its directors, officers, employees, controlling persons and all
other prospective sellers and their respective directors, officers, general and
limited partners, managing directors, and their respective controlling persons,
against any and all losses, claims, damages or liabilities, joint or several,
and expenses (including any amounts paid in any settlement effected with the
consent of the applicable Holder and any underwriter) to which the Company and
its directors, officers, employees, controlling persons or any other prospective
sellers and their respective directors, officers, general and limited partners,
managing directors, and their respective controlling persons may become subject
under the Securities Act, state securities or blue sky laws, common law or
otherwise, insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) or expenses arise out of or are based upon (i)
any untrue statement or alleged untrue statement of any material fact contained,
on the effective date thereof, in any registration statement under which such
Registrable Securities were registered under the Securities Act, any
preliminary, final or summary prospectus contained therein, or any amendment or
supplement thereto or (ii) any omission or alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading (in the case of a prospectus, in light of the
circumstances under which they are made), and the applicable Holder and any
underwriter will reimburse the Company and its directors, officers, employees,
controlling persons and all other prospective sellers and their respective
directors, officers, general and limited partners, managing directors, and their
respective controlling persons for any legal or any other expenses reasonably
incurred by them as such expenses are

                                       14
<PAGE>

incurred in connection with investigating or defending such loss, claim,
liability, action or proceeding; provided that any Holder and any underwriter
shall only be liable in any such case if any such loss, claim, damage, liability
(or action or proceeding in respect thereof) or expense arises out of or is
based upon any untrue statement or alleged untrue statement or omission or
alleged omission made in such registration statement or amendment or supplement
thereto or in any such preliminary, final or summary prospectus in reliance upon
and in conformity with written information furnished to the Company through an
instrument duly executed by such Holder or any such underwriter specifically
stating that it is for use in the preparation thereof; provided, further,
however, that such Holder or underwriter shall not be required to indemnify the
Company if such untrue statement or omission or alleged untrue statement or
omission was contained or made in any preliminary prospectus and corrected in
the final prospectus or any amendment or supplement thereto and the final
prospectus does not contain any other untrue statement or omission or alleged
untrue statement or omission of a material fact that was the subject matter of
the related proceeding and any such loss, liability, claim, damage or expense
suffered or incurred by the Company resulted from any action, claim or suit by
any Person who purchased Registrable Securities which are the subject thereof
from the Company and it is established in the related proceeding that the
Company failed to deliver or provide a copy of the final prospectus (as amended
or supplemented) to such Person with or prior to the confirmation of the sale of
such Registrable Securities sold to such Person if required by applicable law,
unless such failure to deliver or provide a copy of the final prospectus (as
amended or supplemented) was a result of noncompliance by the Holder or any
underwriter with this Section 6 or as a result of the failure of the Holder or
any underwriter to provide such final prospectus. Such indemnity shall remain in
full force and effect regardless of any investigation made by or on behalf of
the Company or any such director, officer, employee or controlling person. No
Holder shall be liable under this Section 6 for any amounts exceeding the
product of the purchase price per Registrable Security and the number of
Registrable Securities being sold pursuant to such registration statement or
prospectus by such Holder.

          (c)  Notices of Claims, Etc.  Promptly after receipt by an indemnified
               -----------------------
party hereunder of written notice of the commencement of any action or
proceeding with respect to which a claim for indemnification may be made
pursuant to this Section 6, such indemnified party shall, if a claim in respect
thereof is to be made against an indemnifying party, promptly give written
notice to the latter of the commencement of such action; provided that the
failure of any indemnified party to give notice as provided herein shall not
relieve the indemnifying party of its obligations under the preceding
subsections of this Section 6, except to the extent that the indemnifying party
is actually materially prejudiced by such failure to give notice. In case any
such action is brought against an indemnified party, unless in such indemnified
party's reasonable judgment a conflict of interest between such indemnified and
indemnifying parties may exist in respect of such claim, the indemnifying party
will be entitled to participate in and, jointly with any other indemnifying
party similarly notified, to assume the defense thereof, to the extent that it
may wish, with counsel reasonably satisfactory to such indemnified party, and
after notice from the indemnifying party to such indemnified party of its
election so to assume the defense thereof, the indemnifying party will not be
liable to such indemnified party for any legal or other expenses subsequently
incurred by the latter in connection with the defense thereof, unless in such
indemnified party's reasonable judgement a conflict of interest between such
indemnified and indemnifying parties arises in respect

                                       15
<PAGE>

of such claim after the assumption of the defense thereof or a court of
competent jurisdiction determines that the indemnifying party is not vigorously
defending such action or proceeding. An indemnifying party will not be subject
to any liability for any settlement made without its consent (which consent
shall not be unreasonably withheld). No indemnifying party will consent to entry
of any judgment or enter into any settlement of any pending or threatened
proceeding which (i) does not include as an unconditional term thereof the
giving by the claimant or plaintiff to all indemnified parties of a release from
all liability in respect to such claim or litigation, (ii) involves the
imposition of equitable remedies or the imposition of any non-financial
obligations on such indemnified party or (iii) does not otherwise adversely
affect such indemnified party, other than as a result of the imposition of
financial obligations for which such indemnified party will be indemnified
hereunder. Notwithstanding anything to the contrary contained herein, an
indemnifying party will not be obligated to pay the fees and expenses of more
than one counsel (together with appropriate local counsel) for all parties
indemnified by such indemnifying party with respect to such claim, unless in the
reasonable judgment of any indemnified party a conflict of interest may exist
between such indemnified party and any other of such indemnified parties with
respect to such claim, in which event the indemnifying party shall be obligated
to pay the fees and expenses of such additional counsel or counsels (together
with the fees of appropriate local counsel).

          (d)  Contribution. If the indemnification provided for in this Section
               ------------
6 is unavailable to an indemnified party under Section 6(a) or Section 6(b)
hereof (other than by reason of exceptions provided in those Sections) in
respect of any losses, claims, damages, liabilities or expenses referred to
therein, then each applicable indemnifying party, in lieu of indemnifying such
indemnified party, shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages, liabilities or
expenses in such proportion as is appropriate to reflect the relative benefits
received by the indemnifying party on the one hand and the indemnified party on
the other, and the relative fault of the indemnifying party on the one hand and
of the indemnified party on the other in connection with the statements or
omissions which resulted in such losses, claims, damages, liabilities or
expenses, as well as any other relevant equitable considerations. The relative
fault of the indemnifying party on the one hand and of the indemnified party on
the other shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission or alleged
omission to state a material fact relates to information supplied by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission. The amount paid or payable by a party as a result of the
losses, claims, damages, liabilities and expenses referred to above shall be
deemed to include, subject to the limitations set forth in Sections 6(a) and
6(b), any legal or other fees or expenses reasonably incurred by such party in
connection with investigating or defending any action or claim.

          The Company and the Holders agree that it would not be just and
equitable if contribution pursuant to this Section 6(d) were determined by pro
rata allocation or by any other method of allocation which does not take account
of the equitable considerations referred to in the immediately preceding
paragraph.  Notwithstanding the provisions of this Section 6(d), no Holder shall
be required to contribute any amount in excess of the amount by which the total
price at which the Registrable Securities sold by such Holder and distributed to
the public were offered to the

                                       16
<PAGE>

public exceeds the amount of any damages which such Holder has otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged omission. No person guilty of fraudulent misrepresentation (within
the meaning of Section 11(f) of the Act) shall be entitled to contribution from
any person who was not guilty of such fraudulent misrepresentation.

          (e)  Other Indemnification. Indemnification similar to that specified
               ---------------------
in Sections 6(a) and 6(b) (with appropriate modifications) shall be given by the
Company and each Holder with respect to any required registration or other
qualification of securities under any law or with any governmental authority
other than as required by the Securities Act.

          (f)  Non-Exclusivity.  The obligations of the parties under this
               ---------------
Section 6 shall be in addition to any liability which any party may otherwise
have to any other party.

          (g)  Indemnification Payments.  The indemnification and contribution
               ------------------------
required by Sections 6(a), 6(b) and 6(d) shall be made by periodic payments of
the amount thereof during the course of the investigation or defense, as and
when bills are received or expense, loss, damage or liability is incurred.

          7.   Information to be Furnished by the Holders.  Each Holder shall
               ------------------------------------------
furnish to the Company such information as the Company may reasonably request
and as shall be required in connection with the registration and related
proceedings referred to herein. If such Holder fails to provide the Company with
such information within two weeks of the Company's request, the Company's
obligations hereunder with respect to such Holder's Registrable Securities shall
be suspended until such Holder provides such information.

          8.   Miscellaneous.
               -------------

          (a)  Remedies.  The Company and each Holder acknowledge and agree that
               --------
in the event of any breach of this Agreement by any of them, the Holders and the
Company would be irreparably harmed and could not be made whole by monetary
damages. Each party accordingly agrees to waive the defense in any action for
specific performance that a remedy at law would be adequate and that the
parties, 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.

          (b)  Entire Agreement. This Agreement and the Stockholders Agreement
               ----------------
dated July 12, 2000 among the Company, the Holders, Geneseo Communications, Inc.
and Cambridge Telcom, Inc. (the "Stockholders Agreement") constitutes the entire
agreement and understanding of the parties hereto in respect of the subject
matter contained herein, and there are no restrictions, promises,
representations, warranties, covenants, or undertakings with respect to the
subject matter hereof, other than those expressly set forth or referred to
herein. This Agreement supersedes all prior agreements and understanding among
the parties hereto with respect to the subject matter hereof (other than the
Stockholders Agreement).

                                       17
<PAGE>

          (c)  Notices. Any notice, request, instruction or other document to be
               -------
given hereunder by any party hereto to another party hereto shall be in writing,
shall be delivered personally or sent by certified or registered mail, postage
prepaid, return receipt requested, or by Federal Express or other delivery
service, to the address of the party set forth below or to such other address as
the party to whom notice is to be given may provide in a written notice to the
Company, a copy of which written notice shall be maintained on file with the
Secretary of the Company.

          (1)  If to Blackstone, to:

               c/o The Blackstone Group
               345 Park Avenue, 31/st/ Floor
               New York, NY 10154
               Phone: (212) 583-5541
               Fax:   (212) 583-5722
               Attention: Michael S. Chae

               With a copy to:

               Simpson Thacher & Bartlett
               425 Lexington Avenue
               New York, New York 10017
               Phone: (212) 455-7063
               Fax:  (212) 455-2502
               Attention: Wilson S. Neely

          (2)  If  to TCW, to:

               TCW/Crescent Mezzanine, LLC
               11100 Santa Monica Boulevard, Suite 2000
               Los Angeles, CA 90025
               Attention: John C. Rocchio
               Facsimile: (310) 235-5967

               with a copy to:

               O'Melveny & Myers LLP
               400 South Hope Street
               Los Angeles, CA 90072-2899
               Attention: Kathryn Sanders
               Facsimile: (213) 430-6407

          (3)  If  to the Company, to:

               iPCS, Inc.

                                       18
<PAGE>

               121 West First Street
               Suite 200
               Geneseo, Illinois 61254
               Phone: (309) 945-1650
               Fax: (309) 945-1651
               Attention: Timothy M. Yager

               With a copy to:

               Mayer Brown & Platt
               190 South LaSalle Street
               Chicago, Illinois 60603
               Phone: (312) 782-0600
               Fax: (312) 701-7711
               Attention: Paul Theiss

          (d)  Applicable Law. This Agreement shall be governed by, and
               --------------
interpreted in accordance with, the laws of the State of New York applicable to
contracts made and to be performed in that State.

          (e)  Jurisdiction.  The courts of the State of New York in New York
               ------------
County and the United States District Court for the Southern District of New
York shall have jurisdiction over the parties with respect to any dispute or
controversy between them arising under or in connection with this agreement and,
by execution and delivery of this agreement, each of the parties to this
Agreement submits to the exclusive jurisdiction of those courts, including but
not limited to the in personam and subject matter jurisdiction of those courts,
                   -- --------
waives any objections to such jurisdiction on the grounds of venue or forum non
                                                                      ----- ---
conveniens, the absence of in personam or subject matter jurisdiction and any
----------                 -- --------
similar grounds, consents to service of process by mail (in accordance with
Section 8(c)) or any other manner permitted by law, and irrevocably agrees to be
bound by any judgment rendered thereby in connection with this Agreement.

          (f)  MUTUAL WAIVER OF JURY TRIAL. THE PARTIES HERETO WAIVE ALL RIGHT
               ---------------------------
TO TRIAL BY JURY IN ANY ACTION, SUIT OR PROCEEDING BROUGHT TO ENFORCE OR DEFEND
ANY RIGHTS OR REMEDIES UNDER THIS AGREEMENT.

          (g)  Severability.  The invalidity, illegality or unenforceability of
               ------------
one or more of the provisions of this Agreement in any jurisdiction shall not
affect the validity, legality or enforceability of the remainder of this
Agreement in such jurisdiction or the validity, legality or enforceability of
this Agreement, including any such provision, in any other jurisdiction, it
being intended that all rights and obligations of the parties hereunder shall be
enforceable to the fullest extent permitted by law.

                                       19
<PAGE>

          (h) Other Agreements.  Nothing contained in this Agreement shall be
              ----------------
deemed to be a waiver of, or release from, any obligations any party hereto may
have under, or any restrictions on the transfer of Registrable Securities or
other securities of the Company imposed by, any other agreement.

          (i) Successors; Assigns; Transferees.  The provisions of this
              --------------------------------
Agreement shall be binding upon and accrue to the benefit of the parties hereto
and their respective heirs, successors and permitted assigns.  In addition, and
whether or not any express assignment shall have been made, the provisions of
this Agreement which are for the benefit of the Holders shall also be for the
benefit of and enforceable by any Transferee or subsequent holder of Registrable
Securities, subject to the provisions contained herein; provided that the
Company is given written notice at the time or within 90 days of said transfer,
stating the name and address of the Transferee and identifying the securities
with respect to which such registration rights are being transferred; and
provided, further, that the Transferee or assignee of such rights assumes in
writing the obligations of such Holder under this Agreement (in which case such
Holder shall be released from such obligations).  Each Holder shall have the
exclusive option to determine which rights and obligations shall be assigned to
any Transferee.

          (j) Other Entities.  The provisions of this Agreement shall be binding
              --------------
upon and accrue to the benefit of any affiliate or assignee of Blackstone or TCW
that purchases any of Series A-2 Preferred Stock at the Series A-2 Closing (as
such terms are defined in the Investment Agreement) and any such affiliate or
assignee shall be deemed to be a party to this Agreement and included in the
term "Blackstone" or "TCW", respectively, for purposes hereof.

          (k) Amendments, Waivers.  This Agreement may not be amended, modified
              -------------------
or supplemented and no waivers of or consents to departures from the provisions
hereof may be given unless consented to in writing by the Company, and
Blackstone and (other than with respect to those provisions which do not relate
to TCW) TCW.

          (l) Counterparts.  This Agreement may be executed in one or more
              ------------
counterparts, each of which shall be deemed an original but all of which shall
constitute one and the same Agreement.

          (m) Limited Liability.  Notwithstanding any other provision of this
              -----------------
Agreement, neither the members, general partners, limited partners or managing
directors, or any directors or officers of any members, general or limited
partner, advisory director, nor any future members, general partners, limited
partners, advisory director, or managing directors, if any, of Blackstone or TCW
shall have any personal liability for performance of any obligation of
Blackstone or TCW, respectively, under this Agreement in excess of the
respective capital contributions of such members, general partners, limited
partners or managing directors to Blackstone or TCW, as the case may be.

          (n) Adjustments Affecting Registrable Securities.  The Company will
              --------------------------------------------
not take any action, or permit any change to occur, with respect to the
Registrable Securities which would

                                       20
<PAGE>

(i) adversely affect the ability of any Holder to include such Registrable
Securities in a registration undertaken pursuant to this Agreement or (ii)
adversely affect the marketability of such Registrable Securities in any such
registration.

          (o) Rule 144.  If the Company is subject to the requirements of
              --------
Section 13, 14 or 15(d) of the Exchange Act, the Company covenants that it will
file any reports required to be filed by it under the Securities Act and the
Exchange Act (or, if the Company is not required to file such reports, it will,
upon the request of Blackstone, make publicly available such information) and it
will take such further action as any Holder may reasonably request, so as to
enable such Holder to sell Registrable Securities without registration under the
Securities Act within the limitation of the exemptions provided by (a) Rule 144
under the Securities Act, as such Rule may be amended from time to time, or (b)
any similar rule or regulation hereafter adopted by the SEC.  Upon the request
of any Holder, the Company will deliver to such Holder a written statement as to
whether it has complied with such requirements.

          (p) Other Registration Rights.  (i) The Company covenants that it will
              -------------------------
not grant any right of registration under the Securities Act relating to any of
its shares of Common Stock or Common Stock Equivalents or other equity
securities to any person unless the Holders shall be entitled to have included
in any registration effected (A) pursuant to Section 2 hereof, all Registrable
Securities requested by it to be so included prior to the inclusion of any
securities requested to be registered by the persons entitled to any such other
registration rights pursuant to any provision providing registration rights
comparable to those contained in Section 3 hereof and (B) pursuant to Section 3
hereof, during the period of eighteen (18) months following an Initial Public
Offering, all Registrable Securities requested by such Holder to be so included
(I) prior to the inclusion of any securities requested to be registered by the
persons entitled to any such other registration rights pursuant to any provision
providing incidental registration rights comparable to those contained in
Section 3 hereof and (II) with respect to any Requesting Holder, pro rata with
the inclusion of any securities requested to be registered by such Requesting
Holder as provided for in Section 3(b)(ii).

          (ii)  The Company covenants that it will not register any Common Stock
or Common Stock Equivalents or other equity securities held by any person or
entity, other than the Company, as part of an initial public offering of Common
Stock by the Company in a primary offering pursuant to an effective registration
statement (other than on Form S-4, Form S-8 or their equivalents) filed by the
Company under the Securities Act.

          (iii) If the Company at any time grants to any other holders of Common
Stock, Common Stock Equivalents or other equity securities of the Company any
rights to request the Company to effect the registration (whether requested or
incidental) under the Securities Act of any such securities on any terms more
favorable to such holders than the terms set forth in this Agreement, the terms
of this Agreement shall, at the request of Blackstone, be deemed amended or
supplemented to the extent necessary to provide the Holders such more favorable
rights and benefits.

                                       21
<PAGE>

          (iv)  The Company covenants that it will not enter into, or cause or
permit any of its Subsidiaries to enter into, any agreement which conflicts with
or limits or prohibits the exercise of the rights granted to the Holders in this
Agreement.

          (v)   The Company covenants that it will not grant any right of
registration under the Securities Act relating to any of its shares of Common
Stock or Common Stock Equivalents or other equity securities to any Person
pursuant to any provision providing registration rights comparable to those
contained in Section 2 hereof without providing that the exercise of such rights
during the eighteen month period following an Initial Public Offering will only
be permitted following the consummation of an underwritten public offering by
Blackstone.

          (r) Headings.  The headings and captions contained herein are for
              --------
convenience of reference only and shall not control or affect the meaning or
construction of any provision hereof.

                                       22
<PAGE>

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

                              iPCS, INC.

                              By: /s/ Timothy M. Yager
                                  ---------------------------------------------
                                  Name:  Timothy M. Yager
                                  Title: President and Chief Executive
                                         Officer

                              BLACKSTONE iPCS CAPITAL PARTNERS L.P.

                              By:  Blackstone Media Management Associates III,
                                   as general partner

                              By: /s/ Mark T. Gallogly
                                  ---------------------------------------------
                                  Name:  Mark T. Gallogly
                                  Title: Member

                              BLACKSTONE/iPCS L.L.C.

                              By:  Member

                              By: /s/ Mark T. Gallogly
                                  ----------------------------------------------
                                  Name:  Mark T. Gallogly
                                  Title: Member

                                      S-1
<PAGE>

                                  BLACKSTONE COMMUNICATIONS PARTNERS I L.P.

                                  By: Blackstone Communications Management
                                      Associates I L.L.C., as general partner

                                  By: /s/ Mark T. Gallogly
                                      ---------------------------------------
                                      Name:  Mark T. Gallogly
                                      Title: Member

                                  TCW/CRESCENT MEZZANINE PARTNERS II, L.P.
                                  TCW/CRESCENT MEZZANINE TRUST II

                                  By:  TCW/Crescent Mezzanine II, L.P.
                                       its general partner or managing owner

                                  By:  TCW/Crescent Mezzanine, L.L.C.
                                       its general partner

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  TCW SHARED OPPORTUNITY FUND II, L.P.

                                  By:  TCW Investment Management Company
                                  Its Investment Manager

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                      S-2

<PAGE>

                                  SHARED OPPORTUNITY IIB, L.L.C.

                                  By:  TCW Asset Management Company
                                  as its Investment Adviser

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                  TCW SHARED OPPORTUNITY FUND III, L.P.

                                  By:  TCW Asset Management Company
                                  Its Investment Adviser

                                  By: /s/ John C. Rocchio
                                     ------------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:   Mark D. Senkpiel
                                  Title:  Managing Director

                                      S-3

<PAGE>

                                  TCW LEVERAGED INCOME TRUST, L.P.

                                  By:  TCW Advisers (Bermuda), Ltd.
                                  as its General Partner

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                  By:  TCW Investment Management Company
                                  as Investment Adviser

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  TCW LEVERAGED INCOME TRUST II, L.P.

                                  By:  TCW (LINC II), L.P.
                                  as its General Partner

                                  By:  TCW Advisers (Bermuda), Ltd.
                                  its General Partner

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                  By:  TCW Investment Management Company
                                  as Investment Adviser

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                      S-4
<PAGE>

                                  TCW LEVERAGED INCOME TRUST IV, L.P.

                                  By:  TCW Asset Management Company
                                  As its Investment Adviser

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                  By: TCW (LINC IV), L.L.C.
                                  As General Partner

                                  By:  TCW Asset Management Company
                                  As its Managing Member

                                  By: /s/ John C. Rocchio
                                      -----------------------------------------
                                  Name:  John C. Rocchio
                                  Title: Managing Director

                                  By: /s/ Mark D. Senkpiel
                                      -----------------------------------------
                                  Name:  Mark D. Senkpiel
                                  Title: Managing Director

                                      S-5

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