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03.28.2008
Originally featured on BroadcastEngineering.com
Google offers white space device solution; NAB, MSTV reject proposal

Google last week presented the FCC with a proposal that offers an alternative to spectrum-sensing technology in the ongoing white space device (WSD) debate that it said could satisfy both WSD advocates and detractors.

In an ex parte filing with the commission, the search engine giant, which also seeks to enter the wireless business, suggested the commission rely upon a combination of technologies, a database of clear channels for given geographic areas and beacons to protect broadcasters and wireless mic users from WSD harmful interference.

In its proposal, Google commended the efforts of Motorola last fall to advance this approach and suggested the addition of “safe harbor” frequencies from channel 36 to channel 38, which would be reserved for wireless mic applications as well as existing radio astronomy and medical telemetry uses on channel 37.

The Google filing envisions prohibition of WSD transmission on a channel until such a device “first has received an ‘all clear’ signal for that channel, either directly from a database of licensed transmitters in that area, or from a geolocated device with access to that database.”

A “permission to transmit” signal would be transmitted to the device on channels known to be free of licensed users. Devices with no geolocation and database access would not be allowed to transmit until receiving permission.
Google also proposed that inexpensive beacons be added for wireless mic applications outside the “safe harbor” to announce their presence and prevent WSDs from operating on channels being used.

The issue of WSD interference to DTV and wireless mic transmission to this point has centered on spectrum-sensing technology that, as envisioned, would identify what channels are in use by DTV stations and wireless microphones and prevent use on those and adjacent channels to prevent interference. The first round of FCC Lab testing of spectrum-sensing technology generally revealed their failure to perform. A second round of testing was launched on a new generation of prototypes earlier this year.

In its filing, Google said its proposal should make issues raised in the spectrum sensing tests moot. “Simply put, no product will come to market unless the FCC can verify that the device does not interfere with TV or wireless microphone signals. And the combination of geolocation, beacons and ‘safe harbors’ is more than sufficient to ensure the protection of all licensed uses,” the filing said.

The NAB on Monday responded tepidly to Google’s proposal. While acknowledging the company’s recognition “that spectrum sensing alone” won’t protect TV viewers from WSD interference, the NAB questioned the effectiveness of Google’s strategy for personal, portable WSDs. A statement from NAB executive VP Dennis Wharton said “simply adding geolocation and beacon sensing does not mean that mobile operation is suddenly feasible.”
Allowing portable, mobile devices to operate in the same band as television “continues to be a guaranteed recipe for producing interference and should not be allowed under any circumstances,” he said.

The Association for Maximum Service Television (MSTV) also found fault with the Google proposal. Saying the company’s plan “offers nothing new,” MSTV President David Donovan found fault with the lack of new technical information in the proposal to demonstrate that it would work. “Vague promises about ‘no interference’ are not sufficient to protect consumers, who are spending billions of dollars in new digital equipment, or to protect wireless microphones used in live on-the-spot coverage of news and sports events,” he said.

In particular, Donovan pointed out that the Google proposal failed to address adjacent channel interference and dismissed the beacon approach as not adequate to protect wireless mics used for electronic newsgathering (ENG).

To read Google’s filing, visit http://www.nab.org/xert/corpcomm/pressrel/releases/032108_Google_FCC_WhiteSpaces.pdf.



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