**Peer Review Panel Report**

**On**

**OET Report FCC/OET 08-TR-1005**

**Evaluation of the Performance of Prototype TV-Band White Space
Devices**

**Phase II**

Peer Reviewers:

Mary Bucher, WTB

George Dillon, EB

James Higgins, EB/Columbia

Martin Liebman, WTB

Doug Miller, EB/Atlanta

**Background:**

The following is the peer review of OET Report FCC/OET 08-TR-1005,
entitled "Evaluation of the Performance of Prototype TV-Band White
Spaces Devices Phase II." The report is a result of OET's second phase
study of hardware development devices with capabilities for operating on
an unlicensed basis in the TV bands as part of the "TV white spaces"
proceeding, ET Docket No. 04-186. This second phase study examined four
development devices and follows OET's initial study of TV white space
development devices, which was released July 31, 2007, *see* "Initial
Evaluation of the Performance of Prototype TV-Band White Space Devices,"
OET Report FCC/OET 07-TR-1006 (Phase I Report).[^1] The devices examined
in this second phase study were submitted by industry in response to an
OET public notice inviting submittal of additional prototype white space
devices and are product development platforms, rather than models of
products that could actually be marketed. One of these devices has both
transmitting and spectrum sensing capabilities; the other three have
only spectrum sensing capability. Each of the devices has unique
spectrum sensing capabilities and was examined in the laboratory and the
field with respect to its ability to detect the presence of digital TV,
analog TV, and/or Part 74 wireless microphone signals. The one device
with a transmitter was also examined for its potential to cause
interference to the reception of digital television signals and cable
service.

Peer review of the OET report was performed as required under the OMD
Information Improvement Act for influential scientific and engineering
studies. The review panel was made up of five engineers, three from the
Enforcement Bureau and two from the Wireless Telecommunications Bureau.
The review panel analyzed and discussed various subject areas in the OET
report, both independently and jointly. Specifically, as requested in
the OET memo, the review panel addressed the following:

1.  Whether the scope of testing in terms of spectrum sensing abilities
    and signal conditions examined was appropriate and sufficient;

2.  Whether the measurement methodologies used in the testing of the
    prototype devices spectrum sensing abilities was appropriate;

3.  Whether the scope of testing of the device with transmitting
    capability for its potential to cause interference to digital TV,
    analog TV, and wireless microphone signals was appropriate

4.  Whether the various tests performed were properly conducted
    consistent with the selected methodologies.

The response of the review panel is presented below for each question
shown above:

**1) Whether the scope of testing in terms of spectrum sensing abilities
and signal conditions examined was appropriate and sufficient.**

In the opinion of the review panel, the overall scope of the spectrum
sensing testing was appropriate. Tests were performed against a range of
devices that utilized various signal sensing methods. Initial laboratory
tests were performed under controlled conditions, followed up by field
tests utilizing live over-the-air television signals.

For the laboratory tests, initial measurements were taken at multiple
channels across the operating range of the prototype devices, which
consisted of UHF channels 21-51, to determine if the devices responded
consistently. The devices were tested against a clean digital TV signal,
alone and in the presence of TV signals on both the first and second
adjacent channels, as well as recorded RF captures of DTV signals to
simulate various multi-path conditions. These tests were followed up by
field tests at nine different locations representing a variety of
topography including urban, suburban, rural, residential and business
locations. Multiple measurements were taken at each location under
varied indoor and outdoor conditions. The field tests were performed
over the entire operating range of the devices and examined the ability
of the devices to detect live over-the-air ATSC and NTSC signals. For
these tests, channel occupancy based on TV contours was noted, but
actual measurements were taken to determine the occupancy of each
channel.

The wireless microphone portion of the testing was performed both in the
laboratory and in the field. Laboratory tests were performed using
signals generated by two different wireless microphones. The microphones
were placed in an anechoic chamber to isolate the test signal and avoid
undesired signals. White space device sensitivity measurements were
taken for the wireless microphone signal alone and with simulated DTV
signals at various first and second adjacent channels. The field tests
were performed under actual real world conditions during a pre-season
football game at FedEx Field in Landover, MD and before and during a
performance of a Broadway play at the Majestic Theater in New York City.
Measurements were taken at multiple locations and times at these
locations.

The review panel believes that the approach taken and procedures
followed by the staff were well thought out and provided an excellent
analysis of the sensing capabilities of the WSDs. The review panel
believes that if more time and testing equipment had been available for
the laboratory testing, it would be more realistic to have tested
multiple, adjacent DTV signals at the same time, rather than testing
only a single adjacent channel at a time. In addition, if there had been
no time constraints, performing more scans at the various field
locations to obtain a larger set of results for determining detection
reliability would have been useful.

**2)** **Whether the measurement methodologies used in the testing of
the prototype devices spectrum sensing abilities was appropriate.**

The review panel believes that the measurement methodologies used in the
testing of the prototype devices were appropriate. OET developed a Phase
II test plan which largely follows the procedures used for Phase I
testing with some modifications. As in the Phase I test plan, guidance
and procedures established to date by IEEE 802.22 for testing the
spectrum sensing capability of fixed/access WSDs were considered where
applicable. In the instances where the testing deviated from those
methodologies, the review panel feels that the underlying objectives
were met by the tests that were performed. OET indicated that comments
and suggestions offered within the public record in the Commission's TV
white spaces proceeding with respect to both previous and current
testing were considered and included in the test plan where appropriate
and practicable.

As stated above, both laboratory and field tests were performed to
assess the scanning/sensing capability of the prototype WSDs for the
television portion of the testing. Three separate bench tests were
performed to determine the minimum DTV signal detection threshold for
each of the prototype devices submitted for evaluation. The first
laboratory test utilized a single, unimpaired, laboratory-grade DTV
signal as the test input. The second laboratory test utilized recorded
(captured) DTV signals that incorporated "real world" distortions
resulting from reflections and multi-path fading. The third laboratory
test utilized two unimpaired, laboratory-grade signals as the input, one
on the detection channel and the other placed on the first or second
adjacent channel. Measurements were taken to determine DTV power levels
resulting in 100% detection reliability. Data was also collected for a
few points above and below the breakpoint where the detection
reliability degrades from 100%.

In the laboratory multiple measurements were taken in order to determine
the percentage of successful detections with some statistical relevance,
and initial tests were performed for multiple channels to investigate
potential frequency related differences in performance. For the baseline
detection signal test using a single DTV input, the input DTV signal was
initially set to a measurable level and then further attenuated
incrementally with the calibrated step attenuator bank while exercising
the scanner over the occupied channel. At each attenuation step (input
power level), thirty independent trials were performed. Tests were
performed on three channels in the lower (channel 21), middle (channel
36 or 37) and upper (channel 51) portions of the WSD tuning range.

The review panel feels that the number of trials and channels tested was
sufficient. Since the initial test results revealed that the sensing
performance of the devices was fairly consistent over their tuning
range, the remaining tests were performed on a single channel in the
middle of the tuning range. The review panel agrees that testing on a
single channel was appropriate given the results of the baseline
testing.

The methodologies for the two DTV signal tests and the recorded DTV
signal tests were similar to the methodology used in the single DTV
input signal tests. For the two DTV signal test, a second DTV input
signal was introduced at N±1 and N±2. Detection threshold measurements
were performed with the adjacent channel signal power set to -28 dBm
(high), -53dBm (moderate) and -68dBm (low) levels. The review panel
feels that it would be helpful if the report explained the rational for
the selection of these signal levels (i.e., an explanation as to why -28
dBm was considered a high signal level and why -68 dBm was considered a
low signal level).

For both tests thirty independent trials were performed at each
attenuation step (power level in detection channel) in order to
determine the percentage of successful detections with some statistical
relevance. Additional recorded DTV signal measurements utilizing one
thousand independent trials were performed on the Motorola device to
smooth out variations resulting from significant instantaneous temporal
variations in the RF captures. Had time allowed, the panel feels that it
would had been useful to perform these additional measurements on all of
the devices.

Field tests were performed utilizing live OTA ATSC and NTSC television
signals at nine different locations representing a variety of topography
including urban, suburban, rural, residential and business locations. At
each field test site, testing was conducted at two locations under
varied indoor and outdoor conditions. At each of these locations, two
scans were performed with each device over its entire channel range and
the results were recorded. The review panel felt that the measurements
taken at these locations provide a good initial assessment of the
scanners/sensors performance under "real world" conditions. However, the
review panel believes that it would have been useful to consider the
potential effects of interfering structures on the results (i.e., by
performing tests inside and outside at the same site and describing the
nature of any interfering structures). The panel also believes that it
may have been worthwhile to attempt to identify areas subject to fading
and shadowing and to perform tests in and around these areas.

The review panel feels that the measurement methodologies used for the
wireless microphone portion of the testing were appropriate to ascertain
the ability of the devices to scan for and detect Part 74 wireless
microphones. Two different types of microphones, FM modulated and
digitally modulated, were used in these tests. Regarding these tests,
the review panel did note that during most of the field testing scans
were performed with the microphones either turned on or turned off. The
panel believes that testing in a more dynamic environment with
microphones being turned on and off intermittently during the scans
would have been more beneficial. The report also indicates that there
were a large number of false positive indications during the wireless
microphone field testing. In relation to these results, the review panel
believes that it would be helpful if the report could expand on possible
explanations for these results and/or provide a rational for not
performing additional tests to possibly identify their cause.

**3) Whether the scope of testing of the device with transmitting
capability for its potential to cause interference to digital TV, analog
TV, and wireless microphone signals was appropriate.**

It is the opinion of the review panel that the scope of the testing of
the Adaptrum WSD prototype for its potential to cause interference to
digital TV was appropriate, given the study's stated limitations.
However, the review panel did not observe any discussion in the report
describing tests that may have been done to analyze potential
interference to analog TV signals or wireless microphone signals.

The project conducted limited, or "anecdotal," tests of the prototype
WSD transmitter to provide information on its potential to interfere
with digital TV reception. These tests were performed within the
confines of the FCC laboratory facility with an unobstructed
line-of-sight (LOS) propagation path between the WSD transmitter
operating at approximately 150 mW EIRP and the DTV test receiver
antenna. A test DTV receive antenna was mounted on an extendable mast to
simulate a consumer installed roof-top antenna. All available channels
were analyzed for the weakest receivable channel (i.e., the worst-case
interference scenario) and channel 30 was ultimately used for that
purpose. The WSD transmitter was then placed in the "main beam" of the
receive antenna, tuned to each of the immediately adjacent channels, and
activated at incremental distances from the DTV receive antenna while
observing for interference effects to the picture quality. Tests were
also performed with the WSD tuned to channel 30. The distance at which
interference was observed was measured and recorded. The tests were
repeated with the WSD transmitter located to the sides and behind the
DTV receive antenna. Overall, the review panel feels that these tests
provided valuable data on the effects of WSDs on DTV reception. The
panel feels that additional analysis of the WSD transmitter operating at
power levels other than an EIRP of 150 mW, e.g., the power level
initially proposed by the Commission for mobile WSD devices, would be
valuable.

The panel recognizes that use of OTA signals produces only anecdotal
results and the ability to perform tests were limited by the area where
the tests were being performed. Under different circumstances, the
review panel believes that it would have been useful for a larger number
of tests to have been conducted under more uniform conditions to provide
a larger set of results that could be more easily correlated. The review
panel also feels that normalizing the data in Table 4-2 for a standard
path length would perhaps make the results more meaningful. The review
panel recognizes that the testing was limited by the fact that the
Adaptrum WSD prototype was the only available working device with an
active transmitter. Had more transmitting devices been available, the
panel believes that simultaneous testing of multiple devices to
determine the cumulative interference affects of those devices would
have yielded valuable data.

**4) Whether the various tests performed were properly conducted
consistent with the selected methodologies.**

In the opinion of the review panel, the tests were properly conducted
consistent with the selected methodologies. OET developed a Phase II
test plan which largely follows the procedures used for Phase I testing
with some modifications. OET has indicated that comments and suggestions
offered within the public record in the Commission's proceeding on the
TV white spaces with respect to both previous and current testing were
considered and included in the test plan where appropriate and
practicable. For the most part, OET's testing was consistent with the
established Phase II test plan and deviation from the test plan did not
undermine the results. The review panel believes that the testing was
well done and thorough. For more description of the testing methodology,
see No 2 above.

[^1]: Five devices were submitted for this phase of testing; however,
    one of the devices stopped working after a few tests were performed
    on it and the reports contain only partial data for that device.