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Federal Register / Vol. 86, No. 7 / Tuesday, January 12, 2021 / Rules and Regulations
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requirements for public safety entities would complicate equipment certification and would be difficult to enforce since there could be multiple versions of the same device, some of which could be legally used only by specific types of entities. It is not clear how the Commission could ensure that devices approved for use only by public safety entities would be marketed to, and operated by, only those entities.
Higher Power on Adjacent Channels 63. White space devices must generally operate outside the protected contours of adjacent channel TV
stations because a strong signal on an adjacent channel can cause interference to the reception of a channel being viewed. The general requirement that white space devices avoid operation within the protected contours of a station operating on an adjacent channel means that, as a practical matter, a white space device may operate only at locations where there are three contiguous vacant channels, i.e., the channel used by the white space device plus both adjacent channels. The Commissions rules do, however, provide two exceptions that permit white space device operations at lower power levels when adjacent channels are occupied, based upon the shorter distances at which interference to adjacent channel TV stations could occur. First, both fixed and personal/
portable white space devices may operate at up to 40 milliwatts EIRP at locations where both adjacent channels are occupied. Second, fixed white space devices may operate within the protected contour of adjacent channel TV stations with a power level of 100
milliwatts EIRP when the white space device operates in a six-megahertz band centered on the boundary of two contiguous vacant channels, i.e., 50
milliwatts EIRP within a threemegahertz band in each channel.
64. In the NPRM, the Commission sought comment on whether it could permit white space devices to operate at higher power levels than the rules currently permit when adjacent TV
channels are occupied. In particular, the Commission sought comment on methods that could be used to determine the locations where it could permit higher power unlicensed operations on adjacent channels, and if so, what specific technical parameters would need to be considered or specified in such calculations. The Commission also sought comment on whether there is any information available on adjacent channel selectivity and interference rejection capabilities of next-generation TV receivers, such as
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manufacturers specifications or actual measurement results, and whether there is any indication that next-generation TV receivers will have better adjacent channel interference rejection than current receivers.
65. The Commission does not increase the maximum permissible power for white space devices operating inside the protected contour of adjacent channel TV stations at this time. As an initial matter, the Commission does not at this time have sufficient evidence in the record on which to change the manner of protecting broadcast services to a terrain-based model, as Microsoft and others suggest. Microsoft argues that the Commission should permit white space device operation within the protected contour of adjacent channel TV stations at higher power levels than the rules currently permit. In so doing, Microsoft supplied a test report on the results of laboratory measurements of current model ATSC 1.0 TV receivers and next generation ATSC 3.0 TV receivers that it claims shows higher power adjacent channel operation is possible because these TV receivers have better selectivity than the Commission assumed in developing the current power limits and because the use of terrain-based propagation models e.g., Longley-Rice can provide a more accurate determination of where higher power adjacent channel white space device operation can be permitted without causing harmful interference.
Microsoft also supplied a test report on field measurements conducted with Ark Multicasting, a lower power TV network operator, that it claims validates its laboratory measurements and demonstrates that for the given parameters e.g., fixed white space device EIRP and antenna pattern, DTV
transmitter characteristics, adjacent channel selectivity of the newer model TV receivers with integral display tested, and distance between the DTV
transmitter and the TV receiver a white space device can operate within the protected contour on a first adjacent channel at higher powers than currently allowed.
66. But while data supplied by Microsoft shows that some newer model TV receivers have better adjacent channel selectivity than the 33 dB D/
U ratio the Commission assumed when it adopted the power limits for white space devices operating inside the protected contour of adjacent channel TV stations, NAB disputes Microsofts analysis, arguing that the TV receivers it used are not representative of the currently installed consumer base.
Microsofts report shows that the average adjacent channel selectivity of
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tested ATSC 1.0 receivers is better than the value the Commission assumed, and that ATSC 3.0 receivers have a selectivity 10 dB better than that of ATSC 1.0 receivers at lower order modulations and similar to ATSC 1.0
receivers at higher order modulations.
In addition, the report shows that receiver adjacent channel selectivity improves by 5.7 dB on average when a white space device operates at a 3
megahertz offset from a TV channel edge.
67. The improved receiver selectivity shown in Microsofts testing could allow white space devices to operate within adjacent channel protected contours at higher power levels than the rules currently permit without increasing the potential for interference to TV reception. The Commission recognizes, however, NABs concern that Microsofts testing was performed with a limited number of TV receivers which may not be representative of the currently installed base. The Commission encourages Microsoft and other parties to continue studies and white space device and TV receiver testing to determine whether or how the Commission can permit higher power for white space devices without causing harmful interference to TV reception.
The Commission welcomes interested parties to file a petition in the future when this work has been done.
Other Matters 68. Directional antennas. Broadband Connects America Coalition, Public Interest Spectrum Coalition, and WISPA
request that the white space database be allowed to consider the directivity of white space device transmit antennas in determining channel availability for white space devices. NAB opposes this request, arguing that there is no way of determining whether a directional antenna has been installed properly without hiring a licensed land-surveyor, which it believes is unlikely to occur.
The Commission previously considered and rejected requests to consider white space device transmit antenna directivity in the White Spaces Order on Reconsideration and did not make any proposals on this issue in the NPRM.
The Commission declines to take any action on these requests.
69. Wireless microphone issues.
Wireless microphone interests request that the Commission not take action to change the rules for white space devices until it acts on the outstanding proceeding GN Docket No. 14166 that proposed to expand the eligibility for obtaining a part 74 license for wireless microphones and until the Commission addresses difficulties with the white
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