Original URL: http://www.theregister.co.uk/2009/02/26/white_space_mapping/

Spectrum Bridge maps out the white spaces

You said no strings could secure you

By Bill Ray

Posted in Mobile, 26th February 2009 13:08 GMT

While big names compete for the contract to run the white-space database, Spectrum Bridge has quietly put the information online, allowing anyone in America to discover what is in their personal white room.

Spectrum Bridge is better known as the world's first, and only, trading site for those wanting to buy and sell radio spectrum, and has suggested that ultra-short-term licensing might be the best way to make use of white space in the future. But for the moment the company is happy to share the information on what the FCC's historic decision actually means to Americans.

Checking our San Francisco vulture perches, we can see that only channel 22 is available - which puts a mighty 6MHz of spectrum at our disposal between 518 and 524MHz. Not that we're allowed to just start transmitting in that spectrum; only FCC-approved white space devices will be allowed to take advantage of the swath of spectrum available.

6MHz of spectrum might not seem like a lot, and compared to the 100MHz of bandwidth available to Wi-Fi and Bluetooth it is something of a squeeze, but compared to the 5MHz of spectrum that Ofcom has offered as a sop to the UK operators bereft of 900MHz spectrum it's a generous allowance. Ofcom seems to think that 5MHz is enough to run a 3G network in, though 3 will see it in court over that, so perhaps 6MHz isn't that useful.

Not only will our hypothetical white space device have to squeeze into 6MHz of spectrum, but it will be expected to avoid interfering with other users too. It will also need to know where it is at all times so it won't try and make use of all those other channels nearby.

Of course, that's in the crowded urban environment of San Francisco; more rural readers might like to check out their own locations to see what white space might be able to offer them. ®