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White Spaces Test "Rigged," Says Google Co-Founder Page
Davide Marney writes "As reported by the Washington Post, Google co-founder Larry Page claims that an FCC field test of white space wireless devices was 'rigged' to make the test device fail to detect wireless microphone broadcasts. A Google spokesman explained later that testers had hidden the wireless microphones within the same frequency as local television stations, preventing the test device from detecting them."
It takes only a moment to see that it was a rigged test because the wireless Internet device did NOT interfere with the microphone, because it did successfully detect the local television station that was broadcasting on that frequency and therefore did not try to use it. Analog TV stations are some seriously high power broad spectrum noise. Any frequency-hopping wireless Internet device would be useless attempting to use the same frequency and would obviously move on to another part of the spectrum, thereby avoiding interfering with the TV station and any other device being masked by it. That part will be conveniently left out of the headlines. The fact that the wireless microphone itself may have been useless while attempting to use that frequency, due to interference from the television station, will also be left out.
The test is not rigged. I have been doing RF coordination for entertainment professionally for about a decade now and I can assure that with this test the FCC has highlighted one major strategy that we use in crowded RF environments.
An analog television station is not the high power broadband noise machine you make it out to be. An NTSC analog signal takes up 6MHz of bandwidth in the radio spectrum. That signal is actually made up of three distinct signals that are modulated into one channel; those signals are a video carrier, a chromance sub-carrier (color) and a sound sub-carrier. Those signals take up a few 100kHz of bandwidth and are separated by a few 100kHz.
The standard RF microphone used for stage, television and film production has a peak bandwidth of ~ +/- 56kHz or a grand total of ~112kHz total deviation. With that small usage of bandwidth we can fit three microphones into an operating analog television channel without causing interference to the primary spectrum user.
The FCC test seems to be showing that Google's engineers are unaware of this strategy employed by RF coordinators and that if their device decided to employ the same strategy, it would interfere with the operating microphone within the analog television channel.
Mind you, this becomes moot on 19 February 2009 as we cannot do this trick with a digital ATSC signal. That is the high-power noise generating machine you are refering to.
-e