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Congressman quizzes FCC on white space management

White noise in white spaces?

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Congressman John Dingell, chair of the House Energy & Commerce Committee, has joined the white space debate, asking the FCC to explain more about its tests and how it intends to police white spaces in the spectrum.

Dingell asks in a letter to Kevin Martin (FCC chair) if the trials run by the FCC were peer-reviewed, and if not, why not - it's those trials that have given white-space technology the all clear and on which deployment depends. He also wants to know if the FCC has properly considered licensing the spectrum, rather than giving it away for free in the interests of management rather than revenue generation.

The decision on whether to allow use of "white space" - radio spectrum used for TV transmissions in locations where it's not being used - will be made next week when the FCC votes on the issue on Tuesday. The problem is potential interference with licence holding TV broadcasters, and the uncertainty as to how bad that will be, if it exists at all.

Both sides have engaged in disinformation campaigns, with the white-space crowd delighting in descriptions of "Wi-Fi on steroids". Meanwhile the National Association of Broadcasters has roped in sports stars and produced adverts complete with evil cavorting telephones to argue its case.

White space devices are supposed to dance around licensed broadcasts through a combination of techniques: a database of known broadcasters, a sense-and-avoid process to notice when someone else is broadcasting, and a beacon system for existing users, such as wireless microphones. The beacon system is largely dead now, so most devices are using a database approach, combined with sense-and-avoid to allow for unusual conditions, and to avoid other white space devices.

Sense-and-avoid is complex, as it's perfectly possible for a white space device to interfere with a transmitter it can't see if a third party can see both the transmitter and the offending device. Using a database, supplied by the FCC, works great for fixed deployments, with the advantage that a device that has to call home every few days to get a database update can also have it's firmware updated, or be deactivated if it's causing problems.

But remedial action is only possible once the problem has been identified, and the good Congressman has concerns that the FCC hasn't worked out how that's going to happen.

The FCC hasn't defined a process for approving white space devices. The companies involved are hoping that will come out of next week's vote, but it's more likely to follow later in the year. It's also possible that the FCC will decide to limit the use of white space - such as for fixed locations providing rural broadband, where identifying interference should be less difficult.

It's unlikely that the FCC is going to suddenly decide to sell licences to use white spaces, unlike the UK's Ofcom. But this would give the regulator ultimate sanction against anyone generating interference. The entire debate about white space has been based on the premise that it would be free to use, but the Congressman also wants the FCC to explain the thinking behind that:

"Why did the Commission decline to adopt a licensed approach to some or all of this spectrum? Does the Commission not believe that a licensed approach could help alleviate some of the accountability concerns expressed above?"

If next week's vote approves white space devices, as expected, then we'll see the first devices towards the middle of next year. But we won't know if the FCC made the right decision until early 2010 when the white spaces will start filling up with white noise. ®

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