Original URL: http://www.theregister.co.uk/2012/05/09/white_spaces_nab/

US TV overlords retreat from White Space invaders

This town is big enough for the both of them

By Bill Ray

Posted in Hardware, 9th May 2012 14:28 GMT

The US National Association of Broadcasters has asked the courts to dismiss its own appeal against the FCC's decision to permit the exploitation of radio White Spaces - and not before time.

The appeal was lodged in 2009, when the use of White Space was fiercely debated, but these days there are White Space devices being legitimately deployed around the US and the unabated continuation of TV broadcasts rather undermines the NAB position that such devices would leave screens dark.

The NAB reckons that's thanks to the limits imposed by the FCC, which resulted from its campaign, but really it’s the dynamic nature of White Space radio which has rendered the appeal unnecessary.

The appeal was lodged back in 2009 as part of a huge publicity campaign against the reuse of television broadcast frequencies for short-range networking.

White Space devices utilise spare frequencies not being used locally for TV transmissions; those bands would interfere with neighbouring transmitters if used for TV broadcasting but can be used for short-range radio links – taking advantage of the building penetration and range the frequencies permit.

When White Spaces were first mooted, the idea was for devices to detect and avoid existing transmissions, but it turns out that's both impossible and impractical (despite the best efforts of both Google and Microsoft), so devices are now required to call up a national database to get a list of locally available bands.

But that database approach opens up a whole new set of possibilities, such as placing draconian restrictions on White Space devices and then slowly relaxing those restrictions as the devices prove themselves. White Space devices are required to check regularly with the database and can receive updated permissions, so the FCC can dial up, or down, the power, and even block out whole frequencies on a regional or national basis, all in a matter of minutes.

That's in stark contrast to technologies such as Bluetooth or Wi-Fi, which were conservatively specified, and will remain so for the lifetime of the kit.

It is generous to suggest that the NAB has evaluated the changes and decided the risk had disappeared – it's more probable that certain defeat loomed – but the rules do mean that should televisions across America go dark as the White Spaces fill up, then at least the FCC will be able to get them going again. ®