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                                                                     EXHIBIT 8.3

                                                                  DRAFT 12/29/99

                         [Letterhead of Sidley & Austin]

                                January __, 2000

Aerial Communications, Inc.
8410 West Bryn Mawr
Suite 1100
Chicago, IL 60631

Ladies and Gentlemen:

        We have acted as counsel for Aerial Communications, Inc., a Delaware
corporation ("Aerial"), in connection with the proposed merger (the "Merger") of
VoiceStream Subsidiary III, a Delaware corporation ("Merger Sub"), all of whose
outstanding stock is owned by VoiceStream Wireless Holding Corporation, a
Delaware corporation ("VoiceStream Holding"), with and into Aerial pursuant to
an Agreement and Plan of Reorganization dated as of September 17, 1999 (the
"Aerial Merger Agreement"), among VoiceStream Wireless Corporation, a Washington
corporation ("VoiceStream"), VoiceStream Holding, Merger Sub, Aerial and
Telephone and Data Systems, Inc., a Delaware corporation, and as described in
the registration statement on Form S-4 (the "Registration Statement") which
includes the Proxy Statement/Prospectus of VoiceStream, Aerial and Omnipoint
Corporation, a Delaware corporation ("Omnipoint"), as filed with the Securities
and Exchange Commission (the "SEC") on January ___, 2000. Capitalized terms used
but not defined herein have the meanings ascribed to them in the Aerial Merger
Agreement.

        As provided in the Aerial Merger Agreement, at the Effective Time, by
reason of the Merger: (i) each issued and outstanding Series A Common Share, par
value $1.00 per share, of Aerial (collectively "Aerial Series A Shares") and
each issued and outstanding Common Share, $1.00 par value per share, of Aerial
(collectively "Aerial Common Shares" and together with the Aerial Series A
Shares, the "Aerial Common Stock") (other than shares of Aerial Common Stock to
be canceled as described below) will be converted into (a) shares of validly
issued, fully paid and nonassessable shares of common stock, no par value, of
VoiceStream Holding ("VoiceStream Holding Common Stock"), with cash paid in lieu
of fractional shares of VoiceStream Holding Common Stock, and/or (b) with
respect to Aerial Common Stock held by Public Holders, the


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Aerial Communications, Inc.
January __, 2000
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right to receive $18.00 in cash (subject to adjustment in certain
circumstances), and (ii) each share of Aerial Common Stock that is owned by
Aerial as treasury stock or by any of its Subsidiaries and each share of Aerial
Common Stock that is owned by VoiceStream Holding or by any of its Subsidiaries
will be canceled and no VoiceStream Holding Common Stock or other consideration
will be delivered in exchange therefor.

        You have requested our opinion concerning certain federal income tax
consequences of the Merger. For purposes of our opinion, we have reviewed the
Aerial Merger Agreement, the Debt/Equity Replacement Agreement, the Registration
Statement and such other documents and corporate records, and have considered
such matters of law, as we have deemed necessary or appropriate. We have assumed
the authenticity of all documents submitted to us as originals, the genuineness
of all signatures, the legal capacity of all natural persons and the conformity
with original documents of all copies submitted to us for our examination. In
addition, we have assumed that (i) the Merger will be consummated in the manner
contemplated by the Registration Statement and in accordance with the provisions
of the Aerial Merger Agreement, (ii) the Merger will qualify as a statutory
merger under the laws of the State of Delaware, (iii) the statements concerning
the Merger and the representations set forth in the Aerial Merger Agreement and
the Registration Statement are true, correct and complete and will continue to
be true, correct and complete at all times up to and including the Effective
Time, (iv) the representations made to us by Aerial and VoiceStream Holding in
the Company Tax Certificate and the Parent Tax Certificate, respectively, dated
on the date hereof are true, correct and complete and will continue to be true,
correct and complete at all times up to and including the Effective Time as if
made at the Effective Time, and (v) any representations in the Company Tax
Certificate, the Parent Tax Certificate or the Aerial Merger Agreement "to the
best knowledge of" or similarly qualified are true, correct, and complete and
will continue to be true, correct, and complete at all times up to and including
the Effective Time as if made at the Effective Time, in each case without such
qualification. If any of the foregoing assumptions is untrue for any reason, our
opinion as expressed below may be adversely affected and may not be relied upon.

        Our opinion is based on the current provisions of the Internal Revenue
Code of 1986, as amended (the "Code"), current regulations and proposed
regulations thereunder, current published administrative rulings and procedures
of the Internal Revenue Service, and judicial decisions published to date, all
of which are subject to change at any time. You should note that future
legislative, judicial, or administrative actions, decisions, or interpretations,
which may be retroactive in effect, could materially affect our opinion. We
assume no obligation to update or supplement this letter to reflect any facts or
circumstances which may hereafter come to our attention with respect to the
opinion expressed herein, including any changes in applicable law which may
hereafter occur.

        Our opinion does not address the tax consequences that may apply to
holders of Aerial Common Stock that are subject to special treatment under the
federal income tax laws (for


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Aerial Communications, Inc.
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example, holders that are banks, financial institutions, broker-dealers,
insurance companies, foreign persons or tax-exempt entities, holders that
acquired their Aerial Common Stock by exercising employee stock options or
otherwise as compensation or through a tax-qualified retirement plan, or holders
that have an excess loss account with respect to their Aerial Common Stock). Our
opinion assumes that holders of Aerial Common Stock will hold such stock as a
capital asset at the Effective Time and does not consider the tax consequences
to any such holders who also own stock of VoiceStream or Omnipoint.

        Based upon the foregoing, it is our opinion that, for federal income tax
purposes:

        1.  the Merger will constitute a reorganization within the meaning
            of section 368(a) of the Code, to which Aerial, VoiceStream Holding
            and Merger Sub will each be a party within the meaning of section
            368(b) of the Code; and

        2.  holders of Aerial Common Stock that do not elect to receive any
            cash in the Merger will not recognize gain or loss solely as a
            result of the conversion of shares of Aerial Common Stock into
            shares of VoiceStream Holding Common Stock in the Merger, except
            with respect to cash, if any, received in lieu of fractional shares.

        Except as expressly set forth above, we express no opinion on any issue
relating to the tax consequences of, or any other matters related to, the
Merger. An opinion of counsel is not binding on the Internal Revenue Service or
the courts, and there can be no assurance that the Internal Revenue Service or a
court would not take a contrary position with respect to the conclusions set
forth above.

        We are furnishing this opinion in connection with the filing of the
Registration Statement with the SEC, and this opinion is not to be used,
circulated, quoted or otherwise referred to for any other purpose without our
express written permission.

        We consent to the filing of this opinion as Exhibit 8.1 to the
Registration Statement and to the reference to our firm name therein. In giving
this consent, we do not admit that we are within the category of persons whose
consent is required under Section 7 of the Securities Act of 1933, as amended,
or the rules or regulations of the SEC promulgated thereunder.




                                              Very truly yours,