Google Alleges Rigging of Wireless Microphone White Space Tests
September 26, 2008
Remember the white space device testing at FedEx field in August?
TV Technology covered it in the article Philips Disputes White Space Test 'Failures". This week, Google's Larry Page claimed the FedEx field tests were rigged. The Google Public Policy Blog reports, "Larry addressed the ways in which TV broadcasters and wireless microphone companies have unfortunately injected politics into the FCC's testing process, referring to August tests at FedEx Field just outside of D.C. and at the Majestic Theater in New York City. Those tests were intended to assess whether white space device prototypes could sense the presence of wireless microphone signals. However actions suggest that wireless microphone operators actually transmitted not on their normal channels but instead on channels occupied by TV broadcast signals. For instance during the FedEx Field test, wireless microphones were improperly used on the very station that carried the broadcast of the game. As a result, the white spaces devices naturally could not detect the microphone signals, as they were hidden by the much more powerful TV signals." It isn't clear exactly what part of the tests Larry Page is talking about, but if he is referring to the Philips white space device—which found few if any channels available at multiple test sites (wireless mics in use or not)—most engineers would say the device was either too sensitive or was acting in a random manner. In any event, if a full-power station was active on the channel and it was detected, the white space device is doing what it should do—block transmission on an occupied channel. Should he be referring to the devices that failed to detect the wireless microphones, if they were transmitting on an "in use" TV channel, why didn't they detect the TV broadcast? From the testing reports I saw, TV signals were very weak on the field. It isn't unusual, in such cases, for a broadcaster or other wireless microphone user to use those channels for wireless microphones. If it was an analog channel, as I suspect was the case, microphones that avoided transmitting on the visual, aural or chroma carriers could operate with little received interference. Consequently, I don't see how Google can claim the tests were rigged by using wireless microphones on channels occupied by TV stations. In either case, the white space devices should have avoided the channel. If anything, the presence of a full-power TV station should have made it easier to detect the channel was in use. Of course, if the wireless microphones were using existing TV channels at FedEx field, white space device supporters can argue, with some validity, that "white space devices"—in this case the wireless microphones—are able to co-exist with TV broadcasting, even on the same channel! The difference, of course is that the wireless microphones were low-power narrowband short-range devices operating on the floor of a stadium. This is an area where it is unlikely anyone except for a fan in the stands with a portable TV set would be attempting to receive an off-air TV signal.
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