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| reply to MrMoody
Re: Ummm, what? We are all making a lot of assumptions here.
"why in the hell were the whitespace devices transmitting there too?"
Firstly we don't know that this was happening.
I don't know any more about the details of the test than most others here. The test, according to page was specifically intended:
" ... to assess whether white space device prototypes could sense the presence of wireless microphone signals." not whether they could sense any signal.
I'm speculating as well but this suggests that specific mechanisms were in place to alter the transmitting behavior of microphones in the area to see if the device detected this. If the device was picking up other signals then it would have trouble detecting this changing behavior wouldn't it?
Again I don't know how the test was structured, but presumably google does. | |
| Additional information from Philips about test of their device.. »www.tvtechnology.com/article/65658
quote:
Shure said in a press release that the prototype devices (actually technology demonstration devices as opposed to prototypes of future products) “were unable to consistently identify operating wireless microphones or distinguish occupied from unoccupied TV channels.” Philips disputes that interpretation ...
Shure Senior Director for Public and Industry Relations Mark Brunner said the Philips device consistently showed channels to be nearly completely occupied even before wireless mics were turned on, while the other (from the Institute for Infocomm Research , backed by the government of Singapore) had the opposite problem, failing to detect occupied channels even after the mics were turned on.
Monisha Ghosh of Philips Research said the Philips device detected channels as occupied because they were in fact occupied—by television signals that in some cases were too weak for a regular handheld spectrum analyzer to detect. The Philips device detects whether a channel is occupied but does not display the strength of the detected signals or distinguish whether they come from wireless mics or television transmitters. It detects TV signals at a level far weaker (less than -120 dBm) than what is viewable on television or can be picked up by conventional spectrum analyzers, she said.
In the case of the FedEx Field tests, she said that in one round of testing—on the football field itself—the device successfully detected a mic turning on (on Channel 31). At higher locations, it detected that channel as occupied from the start, consistent with what FCC data indicated it might detect, she said. Once the device detects a channel as occupied by any source, that channel would be avoided by a future white space device, so there’s no need to further detect low-power wireless activity on the same channel.
“If a wireless mic is using a channel that already has a DTV or NTSC channel on it, the white space device is actually providing more protection [than a wireless mic],” she said.
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