The FCC released a Notice of Proposed Rulemaking last week that could impact broadcast TV viewers, TV white space users, and wireless microphone users. The proposed rules outline how the commission plans to make more TV band spectrum available for white space devices in more locations. The rules will also allow wireless microphone and white space device operations in the 600 MHz “duplex gap” and guard bands adjacent to 600 MHz spectrum licensed for wireless operations after completion of the incentive auction.
The proposed rules will eliminate the two channels reserved for wireless microphones, although they would set aside one channel, where possible, for wireless microphone and white space use in each market. To offset the loss of the reserved channels, the FCC is proposing modifying TV band (white space) database system rules and operations to make it effectively real-time. A broadcaster would be able to reserve a channel for wireless microphone use in the database. White space devices would have to receive and respond to that reservation (avoiding use of the channel) within 30 minutes in the area where the wireless microphone was being used. With elimination of the two reserved channels and far fewer channels available after the repacking, broadcast newsrooms will have to make sure wireless microphone use is registered. With limited spectrum, I also expect broadcasters will have to coordinate wireless microphone operations between news crews to avoid interference.
There would be some spectrum reserved for wireless microphones in the 600 MHz duplex gap. The NPRM proposes reserving 4 MHz of the 11 MHz duplex gap for licensed wireless microphones and an additional 6 MHz of spectrum would be shared between white space devices and unlicensed wireless microphones.
White space devices would be able to operate on channel 37, with protection provided for wireless medical devices through the “white space” database system. Since the database will be providing protection for duplex gap and channel 37 spectrum, the database name will have to be changed. Wireless microphones would not be allowed on channel 37. Operation would be restricted in areas where it could cause interference to radio-astronomy observations.
White space devices would also be allowed to operate on channels 3 and 4, since the FCC noted that most TV sets now have multiple inputs and devices such as cable set-top boxes, DVD players and PVRs that don't require the use of channel 3 and 4 to deliver video and audio to the TV set. White space devices would also be allowed on channels 14-20, with protection to public safety and land-mobile operations provided through the white space database system.
The NPRM asks whether wireless microphone users should be required to pay a fee to use the white space database system, since they would receive benefits from it. Currently only white space device operators have to pay to use the system.
Under the proposed rules, fixed white space devices would be allowed to reduce power and operate closer to the protected contours of TV stations. For example, a 4 watt (36 dBm) EIRP fixed white space transmitter at a height above average terrain (HAAT) of 100 meters must be 25.3 km co-channel TV stations' contours and 1.2 km from adjacent-channel TV stations' contours. If the same fixed white space device dropped its EIRP to 250 mw (24 dBm) it could operate at the same HAAT only 13.2 km from a co-channel TV protected contour and only 600 meters from an adjacent channel TV station's protected contour.
The NPRM considers allowing higher EIRP, up to 10 watts, for fixed wireless devices in rural areas and seeks comments on whether it should retain the maximum conducted power level of 1 watt, which would require more directional antennas to achieve the higher EIRP, improving spectrum efficiency, or allow higher conducted (transmitter) power.
This is a quick summary of some of the major changes proposed for white space devices and wireless microphones operating in the 600 MHz band. Refer to the almost 100 page Notice of Proposed Rulemaking (FCC 14-144) for additional information, including details on how the FCC would regulate certification of wireless microphone operating on frequencies in the UHF TV bands at different stages in the repacking process and the deadlines for moving wireless microphones and white space devices out of spectrum no longer used for TV broadcasting.
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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