Motorola, maker of wireless gear and a member of the White Spaces Coalition, demonstrated a beacon device at the FCC Thursday, and claimed it has shown the viability of the technology to protect wireless mic from interference from white space devices.
Motorola has pitched beacon technologies to help protect wireless mic users from interference from white space devices at unscheduled events such as breaking news scenes. Under Motorola’s proposal, mic users would emit the beacon signal—more reliably detectable that a regular wireless mic signal—and warn white space users off the spectrum.
Unlike Philips and the Singapore-backed Institute for Infocomm Research, Motorola did not participate in the FCC’s mic-sensing field tests at an NFL game and Broadway theater earlier this month, because Motorola does not propose to protect the mics through simple detection. It recommends a regime of a geolocation database of licensed mic users, plus use of the beacon by mic users during the unplanned events.
Motorola said its spectrum-sensing device tested RF levels of the beacon well below the -138 dBm it considered the necessary detection threshold.
Broadcasters and wireless mic users have panned beacon technology, in part because of the non-existence so far of such beacons. They have also complained that such a regime places the burden of the beacons on the incumbent wireless mic users. David Donovan of the Association for Maximum Service Television dismissed the beacon regime as reliant on the spectrum-sensing, which he said the summer of FCC tests have proven ineffective at accurately determining whether channels are occupied.
Motorola has suggested a two-tier regime of white space devices, with licensed fixed devices, for application such as rural broadband and wide-area mobile systems, and an unlicensed, lower-power category. To protect TV signals, it wants to use geolocation technology, combined with spectrum sensing.
Motorola also want to see white space devices operate in the adjacent co-channels of DTV stations, something broadcasters oppose.
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