Forget Wi-Fi and 4G — in the future your phone may access the Internet via unused TV transmission bands.

Nokia is testing hardware that allows mobile phones to tap into "white space" — the unused spectrum allotted to TV stations. White space is there because decades ago, broadcast TV stations were given certain frequencies to use, and in the pre-digital era needed space between those stations to prevent interference. Now that television is digital, broadcasters no longer need the analog buffer zone and so that unused spectrum could theoretically be used by someone else.

Why would someone want to tap into the unused spectrum from television days gone by? Because it's hearty and works well indoors. When it was previously used for analog television, it propagated nicely through walls. The idea is to use it like GPS — which doesn't work well indoors — for location-based services. One could have a map-like application that helps a person navigate a university, conference, mall or giant office complex, for instance.

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Nokia set up a demonstration in the Imperial War Museum in Duxford, England. As Scott Probasco, a senior engineer at Nokia, walked around, his Nokia N9 displayed information about the various exhibits. There are other uses — retailers could stream information to shoppers, for example.

The down side (so far) is that phones don't come equipped with chips that decode the signals, so he had to walk around with a box-like contraption attached to the phone. But the proof of principle was a success.

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In the United States, the Federal Communications Commission approved the use of unlicensed "white space" spectrum in 2008, with the rules being set out in September 2010 and adjusted earlier this month. Device makers haven't jumped on it though, largely because standards for broadcast still need to be worked out. So any real devices are not likely to appear before 2015 or thereabouts.

Photo: Nokia engineer Scott Probasco wih the white space hardware in a box

Via Nokia, CNET