Original URL: http://www.theregister.co.uk/2012/03/08/white_spaces/

Ofcom supremo dreams of filling WORLD'S cracks

Gaps in spectrum need a lick of white paint

By Bill Ray

Posted in Broadband, 8th March 2012 09:04 GMT

Ofcom's chief executive has been telling Brussels about the importance of White Spaces, and how Europe should be leading the shift to dynamic spectrum allocation rather than following behind the Americans.

Speaking at the Dynamic Spectrum Access Forum, Ed Richards reminded the crowd that filling the White Spaces – locally empty TV channels – would mean building an infrastructure which could then be applied across the radio spectrum, removing the need for international harmonisation and filling the airwaves as never before.

White Spaces are radio frequencies which aren't being used locally for TV transmissions. For example, the frequency being used to transmit TV in London can't be used to transmit TV in Milton Keynes, but could be used by a low-powered device for local networking. That means having a database of available frequencies, and requiring every White Space device to check with that database to see what frequencies are available locally.

That database could, once established, provide information on local laws and limits on broadcast power, so the device could operate only within the frequencies and the power levels allowed in that country. More importantly it means manufacturers can churn out the same device for sale internationally.

That's important, as the success of Wi-Fi is largely attributable to the global reservation of the 2.4GHz band in which it operates (where Bluetooth also plays). The same thing applies to GSM. Although 2G telephony now operates in a handful of bands, manufacturers were able to achieve economy of scale even with single-band handsets thanks to the international agreements.

But international harmonisation takes time, and it's getting more difficult to find bands on which everyone is prepared to agree. LTE (4G telephony) is already being spread across 32 separate bands, and the fragmentation is only going to increase.

The solution, claims Richards, is to apply the White Space model more widely, allowing all sorts of devices to check for locally available spectrum and regulation so they can be manufactured for international sale.

The more astute reader will have noticed the flaw in this plan: that every device will need a working internet connection before it starts transmitting. For some devices that's fine; they can use a low-bandwidth connection such as 2G cellular to find an available frequency – and where an access-point architecture is being deployed – and then the access point can decide on the best band to use and broadcast that out to client devices.

But White Space devices will do all sorts of things, such as the latest from MELD which broadcasts a high-definition video stream around one's home. The MELD devices use TV frequencies as intended, so one can tune in an unmodified digital television. The devices are being developed in cooperation with US database pioneer Spectrum Bridge (your speakers aren't broken; there is no audio):

Spectrum Bridge is still the only FCC-approved database operator, but another dozen companies should be approved very soon. Ofcom hasn't started that process yet, so we're still at least a year away from being able to buy White Space devices in Blighty, let alone overtake the Americans. But once we can, we'll be taking part in a massive beta test of the technology which should, if it works, revolutionise the way we use radio spectrum. ®