Subject: [NEXTEL-1] Unlicensed Operation in the TV Broadcast Bands ET Docket No. 04-186 Additional Spectrum for Unlicensed Devices Docket No. 02-380 Below 900 MHz and in the 3 GHz Band ET

From: NEXTEL-1
Date: Fri, 23 Jul 2004 12:04:51 -0400

Before the
Federal Communications Commission
Washington, D.C. 20554
In the Matter of
Unlicensed Operation in the TV Broadcast Bands  ET Docket No. 04-186
Additional Spectrum for Unlicensed Devices ) ET Docket No. 02-380 Below
900 MHz and in the 3 GHz Band )

TO: The Commission

REQUEST FOR CLARIFICATION OF
THE ASSOCIATION FOR MAXIMUM SERVICE TELEVISION

The Association for Maximum Service Television, Inc. (MSTV) respectfully
requests that the Commission clarify certain aspects of its proposal to
allow unlicensed devices to operate in the broadcast television spectrum
at locations where the spectrum is “unused” by television stations.1
Such clarification will allow MSTV and other parties to produce a full
and responsive assessment of issues raised by that proposal.

I. REASON FOR AND PREMISES OF MSTV’S STUDIES.

An oft-repeated premise of the Commission’s proposal is that unlicensed
devices will cause no interference to the public’s television service.2
At the same time,
substantial concern and uncertainty have been raised about the
theoretical and practical
validity of that premise, both during the digital television transition
and afterwards. A

1 Unlicensed Operation in the TV Broadcast Bands, Notice of Proposed
Rulemaking, ET Docket No. 04-186,
FCC 04-113 (rel. May 25, 2004) (hereinafter “NPRM”).

2 Id. at  15 (“[I]t appears that there are technical options now
available that make it feasible for new types of
unlicensed equipment to share spectrum in the TV bands without causing
harmful interference to TV broadcast or other licensed services
operating within these bands.”); OET Chief Sees Potential Solution For
“White Spaces” TV Proposal, Communications Daily, April 19, 2004
(Quoting Office of Engineering & Technology Chief Edmond Thomas as
stating that the unlicensed devices proposal is “design[ed]… in such a
way [that] it doesn’t create interference for the TV broadcasters in the
channels that are used.”).

- 2 -
productive discussion concerning the Commission’s unlicensed devices
proposal will depend on a full and reliable evaluation of that
underlying premise. Accordingly, MSTV, alone or with other interested
organizations, is proceeding with a comprehensive measurement and
evaluation program to assess the impact of the Commission’s proposal on
the public’s current television service and the digital transition.
Specifically, it intends to conduct:

??A laboratory evaluation of the interference potential of unlicensed
devices on existing analog and DTV receivers;
??An assessment of the available spectrum for unlicensed devices; and
??Other tests that are deemed appropriate to develop a technically sound
and complete record in this proceeding, such as an evaluation of the
feasibility and practicality of unlicensed equipment that would provide
the interference protection necessary to safeguard the integrity of the
broadcast television service.  The Commission’s Notice of Proposed
Rulemaking, however, fails to provide certain important technical
information necessary for such an evaluation. 3 These uncertainties make
it both difficult and risky for MSTV (or any other party) to undertake
its planned tests. Although, in the interest of time, MSTV is willing to
begin its studies and assume the risk that its preliminary findings may
rest on an incomplete understanding of the NPRM’s parameters, it also
requests that, as soon as possible, the Commission provide clarification
on the issues described below.

II. TECHNICAL ISSUES ON WHICH MSTV REQUESTS CLARIFICATION.

Following is a description of technical matters raised in the
Commission’s
NPRM for which MSTV respectfully requests additional clarification. MSTV
has separately
identified and described each factor to facilitate the Commission’s
ability to respond to this

3 When it files comments in this proceeding, MSTV may raise questions
about the Commission’s suggestions
for the parameters of unlicensed operation in the broadcast television
spectrum. At this time and for the purposes of its comprehensive
studies, however, MSTV simply wishes to understand the parameters of the
Commission’s proposal.
- 3 -
request, but the factors are dependent with one another. As a
consequence, an error in one factor may affect conclusions that are
dependent not only on that factor, but some or all of the others as
well.

A. Minimum/Maximum Operating Bandwidth and Channelization.
The Commission’s NPRM does not specify the minimum/maximum operating
bandwidth or channelization for the proposed unlicensed devices. For
example, it is unclear whether the unlicensed devices would operate with
a fixed channelization bandwidth similar to Wi-Fi devices currently
operating under the IEEE 802.11 standards, or a scalable channelization
bandwidth similar to IEEE 802.16 devices. It is also necessary to know
whether these devices will operate using all six MHz of a “vacant”
adjacent television channel, or only a sliver of megabits in the middle
of each channel. Moreover, the Commission should clarify whether the
fixed/access devices (i.e., fixed base stations) operate as stand-alone
devices, or a wireless network (such as in a WiMAN system), or both.
Perhaps the answer to these questions will vary depending on which type
of service is to be rendered by the unlicensed device?

Knowledge of the service types and operating bandwidth of the unlicensed
devices is necessary not only to determine their interference impact on
television receivers, but also to assess the related technical
complexity and economic viability of devices that would adequately
protect television reception from out-of-band emissions. Accordingly,
MSTV seeks clarification on these issues and requests that the
Commission clearly specify the operating bandwidth and the
maximum-allowed out-of-band emission (i.e., how many dB down relative to
their defined-peak power) for the fixed-base transmitters when they
operate on a single 6 MHz channel within the television spectrum bands.
Lacking such information, MSTV will assume a single architecture (mesh
network) in its tests of unlicensed device - 4 - operation in the
television broadcast spectrum. But if this assumption is mistaken,
MSTV’s test results may not accurately reflect the actual interference
risk posed by the unlicensed devices.
B. Operation Within a Single or Multiple Channels.

The NPRM proposes that fixed-base station devices be capable of
operating on multiple channels. It also, however, proposes to use D/U
ratios that were developed for a single six-MHz wide (i.e.,
broadcast-based) television channel in determining the appropriate
location of the fixed-base station devices.4 Thus, for a given fixed
location within a television service area, MSTV is uncertain whether 1)
these devices will operate on multiple channels, with a requirement that
they meet the D/U ratios for all the television stations in the vicinity
of that location, or 2) they will operate on a single television
channel, with a requirement only that they comply with the co-channel
and adjacent channels D/U ratios for that single channel.

Clarification regarding the scope of unlicensed device operation across
single or multiple channels is necessary to determine the availability,
if any, of white areas in congested markets, and/or the restrictions
necessary for these devices to operate in such markets. Lacking
clarification from the Commission, MSTV will assume that these fixed
devices will operate on multiple channels and will be placed in
locations where they have to meet all the required D/U ratios. If this
assumption is mistaken, MSTV’s test results may incorrectly identify
where fixed-base station devices could be located in a given market, as
well as the resulting interference from operation in those locations.
4 NPRM at  30.
- 5 -

C. Modulation Type.
The NPRM does not specify the type of modulation allowed for the
unlicensed devices. This factor may impact the performance and
manifestation of interference on both an analog and/or digital
television receiver.5 For example, depending on the modulation-type
used, interference from a device may appear as noise- like interference
on a television set, a band across the television screen, or a total
elimination of the television picture and/or sound.

Specifying the modulation type would allow MSTV and other interested
parties to properly test and assess the potential interference impact of
unlicensed devices on the current population of television receivers. In
addition to measuring interference potential, such information is
essential for conducting MSTV’s spectrum availability evaluation.
Without specification by the Commission regarding modulation type, MSTV
will have to assume a single modulation-type that, in its good faith
judgment, best approximates the likely character of the unlicensed
devices that would operate in the television spectrum. Using a
single-modulation type would limit MSTV’s findings to the chosen
modulation scheme and may not necessarily be appropriate to the actual
modulation-type eventually used by the unlicensed devices.

D. Desired Signal Level.

In its NPRM, the Commission proposes to apply the FCC Broadcast Curves
to
determine the separation distances necessary to protect television
receivers from interference
caused by unlicensed devices operating on a co-channel or first adjacent
channel(s) of a
5 For example, the potential for interference to digital television
receivers may vary depending on the spread
spectrum technique, such as direct sequence or frequency hopping, used
by the unlicensed devices.
- 6 -

television station. 6 Yet the Commission specifies the F(90,90) curves,
which are not defined under its rules, to determine the Desired signal
level (D) of unlicensed device operation inside a TV station adjacent
channel contour. It is thus unclear what dB correction should be used to
adjust the FCC’s F(50,50) or F(50,90) curves in order to calculate the
desired F(90,90) field strength level. MSTV also requests clarification
on whether that correction varies depending on the Antenna Height Above
Average Terrain value.  Without a correction factor for the F(90,90)
criteria, it is not possible to identify the required distance
separation needed to protect television service from unlicensed device
interference, or the availability of white areas within a TV station
adjacent channel contour. Lacking guidance from the Commission, MSTV’s
analysis will use a correction factor of 7.1 dB to be added to the field
of the FCC(50,90) curves for VHF and UHF.7 If this assumption is
incorrect, MSTV’s analysis may severely under- or overestimate the
appropriate interference protection area inside an adjacent channel TV
contour.

E. Undesired Signal Level.

The NPRM also proposes use of the broadcast F(50,50) curves, but
specifically the appropriate power of the unlicensed device and actua l
antenna height above ground, to compute the undesired signal level (U)
generated from the unlicensed devices.8 But the FCC (50,50) curves do
not specify antenna height above ground, but rather Antenna Height Above
Average Terrain (HAAT). MSTV thus asks the Commission to clarify whether
it proposes to substitute the antenna height above ground for HAAT for
purposes of computing interference from fixed-base unlicensed devices.

6 NPRM at  30. The Broadcast Curves are found in Section 73.684 of the
Commission’s rules.
7 The 7.1 dB correction factor is currently being used by the Canadian
government to compute coverage of
DTV stations.
8 The portable/personal devices are assumed to have a maximum antenna
height of 2 meters. Fixed base-station
devices are assumed to have a minimum antenna height above ground of 10
meters. NPRM at  31.
- 7 -
The requested information is essential for conducting a reliable
spectrum availability evaluation. Absent clarification from the
Commission, MSTV will use the Antenna Height Above Average Terrain
figure to compute the undesired field strength level.  Using the wrong
criteria could result in seriously under- or overestimating the
interference constraints necessary to protect the public’s television
service.

F. Other Appropriate Models.

The Commission also proposes to allow manufacturers and distributors of
unlicensed devices to calculate the undesired unlicensed signal levels
using “other appropriate models” besides the broadcast F(50,50) curves.9
In evaluating these proposals, it is impossible to assess interference
risks without knowing the parameters for these other unspecified models.

Specification of these alternative models by the Commission is necessary
for the television industry to conduct a thorough evaluation of the
unlicensed device proposal, and will eliminate confusion among the
various commenters about which model parties have used in reaching their
conclusions about the Commission’s proposal.10 Clarification on this
point is therefore essential to MSTV’s spectrum availability analysis.
Lacking guidance from the Commission, MSTV will use only the FCC
Broadcast Curves to conduct its analysis. As a result, its findings will
not necessarily be applicable to the many potential unspecified models
of determining undesired signal levels for unlicensed devices.
9 Id.
10 Moreover, because these devices are unlicensed, the Commission will
not be in a position to evaluate the
unspecified appropriate models before they will be used in the field.
- 8 -
CONCLUSION
MSTV seeks to undertake an objective, good faith analysis of the
Commission’s proposal to allow unlicensed device operation in the
television broadcast spectrum. In light of the impact that the accuracy
of MSTV’s assumptions will have on its comprehensive analysis, MSTV
respectfully requests prompt clarification on the points described
above.
Respectfully submitted,
_/s/ David Donovan_________________
David Donovan
Victor Tawil
ASSOCIATION FOR MAXIMUM SERVICE
TELEVISION, INC.
4100 Wisconsin Avenue, NW, 1st Floor
Washington, D.C. 20016
202-966-1956 (phone)
202-966-9617 (fax)
June 21, 2004
Jonathan D. Blake
Matthew S. DelNero
COVINGTON & BURLING
1201 Pennsylvania Ave., N.W.
Washington, D.C. 20004
202-662-6000 (phone)
202-662-6291 (fax)
Counsel for the Association for
Maximum Service Television, Inc.

http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf==pdf&id_document=e16214486

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