Another Alliance pushes into White Space

Filling the airwaves with IEEE goodness

The WhiteSpace Alliance will endorse the IEEE 802.22 standard for networks operating in unused television frequencies, but world domination is far from assured.

While most developed countries are agreed that White Space should be filled – with unlicensed devices reliant on a central database of available frequencies – beyond that there are multiple standards which can, and will, be used. The newly formed Alliance has said that it is committed to promoting the IEEE's preferred solution.

White Space radios operate in the bands being used to transmit television elsewhere - so a transmitter in London might be using a band which can't be used for high-power TV transmissions in Oxford, as the cities are too close, but could be used for low-power radios as long as they know where they are and which bands can safely be used.

That information comes from a database, and device manufacturers sign up to specific database providers, but once that information is available the actual signals sent over the band aren't mandated.

So the band ends up like the 2.4GHz band: with baby-listeners, Wi-Fi devices and Bluetooth communications all coexisting, mostly happily, despite all using entirely incompatible protocols optimised for specific usage models. Bluetooth, for example, incorporates service discovery at a very low level and leaps around the band to avoid interference, while Wi-Fi keeps things as simple as possible to stay cheap but provides a faster connection when it is working.

Similarly 802.22 is aimed at Wireless Internet Service Providers (WISPs) who want to offer headline speeds of 29Mb/sec with a range of 100km, while Weightless (from UK-based Neul) only has a range of 10km but promises a battery life measured in years.

Other companies are trying to get LTE working in White Spaces, or want to just shoehorn the existing Wi-Fi standards into the White Space slots (particularly tough as White Space slots are 8MHz in the UK and 6MHz in the US, while Wi-Fi prefers channels of 20MHz or so).

Existing standards have to conform to the FCC's radio mask, which demands that radios operating in White Space devices are enormously square - they aren't allowed to leak into neighbouring bands as Neul demonstrates:

Graph showing white space mask in comparison to wi-fi

White Space radios must not fall outside the green line

That mask makes it very hard to use existing technologies, and the White Spaces are probably big enough to support a few technical standards as long as they can be convinced to play nicely together, or at least not to knock each other out on sight. ®

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