The Federal Communications Commission completed its first field test of a prototype unlicensed wireless device that would share the digital-TV spectrum with broadcasters.
Motorola said it showed that its proposed geolocation database works, while broadcasters argued that the devices continue to fall short.
Bruce Oberlies, Motorola’s senior director of advanced technology and strategy, said the first test was a tough one, in a valley with trees, and the device's geolocation database correctly identified channels in use.
He added that the testing in sensing mode also went "very well," saying that there might have been a missed a channel or two, but the geolocation database is the primary safeguard for TV channels and the devices’ first line of defense.
David Donovan, who heads the broadcasters' spectrum watchdog group, the Association for Maximum Service Television, saw the tests a lot differently, zeroing in on the sensing tests, where the devices remotely sense whether a channel is being used.
"The FCC’s field tests demonstrated that these devices are not reliable and will result in interference to consumers’ DTV sets," he said. "Today, the FCC conducted two tests of two devices at two locations roughly 50 feet apart. In each instance, the devices recorded sensing different channels. The same device operating at the same location got different results. Some of the most significant stations in Washington [D.C.] were missed. In other cases, the devices registered channels as being occupied that were in fact vacant. Another device being examined took more than an hour-and-a-half to scan 30 channels."
The Motorola devices had some sensing problems in FCC lab testing, which broadcasters said showed that they were not ready to share the DTV band and potentially interfere with the beautiful new digital pictures most viewers would be migrating to in February 2009. Motorola countered that the device ultimately passed the test and that the combination of spectrum sensing, geolocation and other technologies will "fully protect the television-viewing public."
Google -- which is all for promoting wireless Internet access via laptops that would operate in the white spaces -- backed Motorola's approach.
Broadcasters fear that if a device cannot tell when a broadcaster is already using a channel, it could mistakenly start transmitting on that channel and interfere, literally and figuratively, with the DTV transition.
The FCC is trying to figure out how and whether to allow unlicensed devices to operate in the DTV spectrum in an effort to more efficiently use the spectrum. Most are on the record favoring allowing them to share the band, but only so long as they don't interfere with DTV broadcasts. It is conducting the field tests in about one-dozen locations over the next month or so.