**Before the**

**Federal Communications Commission**

**Washington, D.C. 20554**

In the Matter of )

)

Request For Declaratory Ruling on the ) DA 98-2129

Use of Orthogonal Frequency Division )

Multiplexing Modulation by Multipoint )

Distribution Service and Instructional )

Television Fixed Service Stations )

**DECLARATORY RULING AND ORDER**

**Adopted: March 19, 1999 Released: March 19, 1999**

By the Chief, Mass Media Bureau:

**INTRODUCTION**

Number range level0Number range level1Number range level2Number range
level3Number range level4Number range level5Number range level6Number
range level71. The Commission, by the Chief, Mass Media Bureau, acting
pursuant to delegated authority, has before it a request for declaratory
ruling filed by Clarity Wireless, Inc. (\"Clarity\") pursuant to Section
1.2 of the Commission\'s Rules, 47 C.F.R. § 1.2.[^1] Clarity seeks
approval for the regular use of Orthogonal Frequency Division
Multiplexing Modulation (\"OFDM\") at stations operating in the
Multipoint Distribution Service (\"MDS\") and the Instructional
Television Fixed Service (\"ITFS\"). For the reasons set out below, we
are granting Clarity\'s request and adding OFDM to the list of approved
digital emissions for stations in these services.

**BACKGROUND**

2\. On July 9, 1996, the Commission adopted a declaratory ruling[^2]
which permits stations operating in the MDS and ITFS services to utilize
certain digital emissions on a regular basis, so long as those emissions
meet certain requirements for power spectral uniformity and out-of-band
emissions (\"spectral mask\"). Based on comprehensive laboratory test
data submitted by the petitioners requesting the *Digital Declaratory*
*Ruling*, the Commission determined that the interference potentials of
Vestigial Sideband Modulation (\"VSB\") and Quadrature Amplitude
Modulation (\"QAM\") were no greater than that of NTSC analog video
modulation, and these modulation formats were adopted to be routinely
authorized up to densities of 8-VSB and 64-QAM. With respect to the
spectral mask, petitioners sought, and the Commission granted on an
interim basis, an amendment to the emission mask for MDS and ITFS
stations using VSB and QAM to account for the significant difference
between the spectral occupancy pattern of these emissions and the
spectral occupancy of the NTSC analog video emission.[^3] Additionally,
with respect to the spectral occupancy of these digital emissions, the
Commission set out a requirement in the *Digital Declaratory Ruling*
that the power spectral density be \"substantially uniform\" across the
occupied bandwidth, including at times when no data (input signal) is
applied to the transmitter.[^4]

3\. In the *MDS & ITFS Two-Way Order*, the Commission, *inter alia*,
amended its Rules for the MDS and ITFS services to permit the regular
use of Quadrature Phase Shift Keying (\"QPSK\") modulation and Code
Division Multiple Access (\"CDMA\") modulation.[^5] This action was
based on data and information submitted by ADC Telecommunications Corp.
et al. (\"ADC\") in a petition for declaratory ruling requesting the
addition of these digital modulation formats for use at MDS and ITFS
stations.[^6] Those petitioners argued, and the Commission agreed, that
QPSK was essentially an alternative designation for the
already-permissible 4-QAM. With respect to CDMA, petitioners submitted
the results of extensive laboratory testing which showed that CDMA
presented essentially the same potential for interference to NTSC
signals as do VSB and QAM, and therefore could be approved subject to
the same technical restrictions applying to VSB and QAM. The Commission
noted that it would \"continue our policy of authorizing the use of
other digital modulation formats where such use can be demonstrated to
be within the confines of the interference protection standards for the
MDS and ITFS services\"; *i.e.*, desired-to-undesired signal strength
ratios of 45 dB for cochannel stations and 0 dB for adjacent channel
stations.

**CLARITY PETITION & COMMENTS**

4\. In its petition, Clarity submits that OFDM offers performance
features not available in other digital modulations, specifically, the
means for \"achieving very high data rates in severe multipath
conditions.\"[^7] OFDM is generated by the creation of multiple signals
(carriers) within an authorized MDS or ITFS channel, each of which
carrier is modulated with a portion of the information being
transmitted. The signal modulating each of the carriers is typically a
form of QAM, *e.g.* QPSK, 16-QAM or 64-QAM. The amplitudes and spacings
of the carriers are configured such that the spectral energy of each
carrier is significantly attenuated at the frequencies of each of the
two adjacent carriers. The modulating QAM signals can be coded in order
to be more robust in the presence of multipath propagation and/or
interference, and Clarity proposes the use of its proprietary coding
schema, designated Vector OFDM (\"VOFDM\"). Clarity retained the
engineering firm of Hardin & Associates (\"Hardin\") to evaluate OFDM
and determine its compatibility with, and potential for interference to,
NTSC analog television signals. In an attachment (\"Hardin Study\") to
the Clarity Petition, Hardin found, using laboratory tests, that OFDM
\"easily complies\" with the interference protection requirements of the
Commission\'s Rules.[^8] Hardin\'s laboratory tests were designed to
insure that the OFDM emissions complied with the mask required for
digital MDS/ITFS emissions.[^9] Hardin\'s conclusions were based on
evaluations of two different OFDM waveforms, one with 256 carriers
modulated by 4-QAM and the other with 4096 carriers modulated by 64-QAM.

5\. Comments on the Clarity Petition were submitted by PetroCom License
Corp., UltimateCom Wireless, LLC and ADC, and reply comments were
submitted by Cisco. All were supportive of the Clarity Petition. Cisco
urged the Commission to act expeditiously, arguing that, in the near
future, MDS and ITFS operators \"will make decisions about digital
equipment procurement and deployment\" and that \"uncertainty may
unnecessarily disadvantage OFDM technology competing in the market with
other digital modulation standards that the Commission has already
approved.\"[^10]

**DISCUSSION**

6\. We agree with Cisco that prompt action on the Clarity Petition is
warranted. The Commission\'s actions in the *MDS & ITFS Two-Way Order*
enhanced significantly the ability of MDS and ITFS licensees to offer a
broad range of communications services to the public. Many of these
services, such as high speed wireless Internet access, will depend on
the availability and use of sophisticated digital transmission
facilities configured with differing modulation formats, depending on
the service being offered, the bandwidth used, path lengths,
line-of-sight conditions and many other factors. For this reason, we
believe it is in the public interest to authorize the use of additional
types of modulation when it can be demonstrated that the potential for
interference will not exceed that provided by the existing protection
standards in the Rules. We conclude that Clarity has met this
requirement, and we therefore are granting its petition to add OFDM to
the list of approved emissions for MDS and ITFS stations.

7\. Specifically, based upon the Hardin laboratory test results, we will
permit the use of OFDM modulation, coded or uncoded, so long as a
minimum of 256 QAM-modulated carriers are used and the transmitted
signal complies with the spectral mask and power limitations set out in
our MDS and ITFS rules for digital emissions. It should be understood
clearly that this action is an interim step in our overall consideration
of the issue of digital modulation in the MDS and ITFS spectrum, as were
our actions in granting approval for VSB, QAM, QPSK and CDMA, pending
the establishment of permanent technical standards for MDS and ITFS
digital operations. We also emphasize at this time that this Declaratory
Ruling and Order and our actions with respect to digital modulation in
the *Digital Declaratory Ruling* and in the *MDS & ITFS Two-Way Order*
apply only to the MDS and ITFS services, and have *no* implications with
respect to other services regulated by the Commission.

**ORDERING CLAUSES**

8\. Accordingly, IT IS ORDERED that under the authority contained in
Section 4(i) of the Communications Act of 1934, as amended, 47 U.S.C. §
154(i), and in Section 554(e) of the Administrative Procedure Act, 5
U.S.C. § 554(e), the Petition for Declaratory Ruling, on the use of OFDM
modulation by MDS and ITFS stations, IS GRANTED to the extent specified
above. This Declaratory Ruling and Order shall be effective upon its
release and shall remain effective until adoption of rules governing
digital transmissions in MDS and ITFS in a future rulemaking proceeding.
See 47 C.F.R. §§ 1.4(b)(2) and 1.103. Nothing in this Declaratory Ruling
and Order shall prejudice the outcome of such a rulemaking proceeding.

9\. IT IS FURTHER ORDERED that the staff of the Mass Media Bureau shall
send copies of this declaratory ruling to the parties filing formal
comments by certified mail, return receipt requested.

FEDERAL COMMUNICATIONS COMMISSION

Roy J. Stewart

Chief, Mass Media Bureau

[^1]: ^?^ Petition for Declaratory Ruling, August 31, 1998 (\"Clarity
    Petition\"). Clarity was acquired effective November 2, 1998 by
    Cisco Systems, Inc. (\"Cisco\").

[^2]: ^?^ *Request for Declaratory Ruling on the Use of Digital
    Modulation by Multipoint Distribution Service and Instructional
    Television Fixed Service Stations, Declaratory Ruling and Order*, 11
    FCC Rcd 18839 (1996) (hereinafter *Digital Declaratory Ruling*)
    (petitions for clarification and partial reconsideration pending).

[^3]: ^?^ *Id.* at 18854. Subsequently, this mask was modified slightly
    when the Commission amended its Rules to expand significantly the
    scope of permissible two-way communications in the Multipoint
    Distribution Service and the Instructional Television Fixed Service.
    *See Amendment of Parts 21 and 74 to Enable Multipoint Distribution
    Service and Instructional Television Fixed Service Licensees to
    Engage in Fixed Two-Way Transmissions, Report and Order*, 13 FCC Rcd
    19112, 19123-27 (1998) (hereinafter *MDS & ITFS Two-Way Order*).

[^4]: ^?^ 11 FCC Rcd at 18857.

[^5]: ^?^ 13 FCC Rcd at 19121-23. The Commission also formally amended
    its Rules to implement the provisions of the *Digital Declaratory
    Ruling* which regularized use of QAM and VSB in these services.

[^6]: ^?^ Request for Declaratory Ruling on the Use of Code Division
    Multiple Access and Quadrature Phase Shift Keying Digital Modulation
    by Multipoint Distribution Service and Instructional Television
    Fixed Service Stations, December 2, 1997.

[^7]: ^?^ Clarity Petition at 3.

[^8]: ^?^ Hardin Study at 8.

[^9]: ^?^ *Id*. at 6; *see MDS & ITFS Two-Way Order*, 13 FCC Rcd at
    19123-27.

[^10]: ^?^ Reply Comments of Cisco Systems, Inc., November 23, 1998, at
    2.