Gadgets that operate over television frequencies promise to transform the wireless landscape.This Motorola radio was tested by the FCC to determine whether it can find occupied frequencies of spectrum. It was also tested to determine the appropriate amount of power to use to avoid interfering with signals from television stations and wireless microphones.If you believe some radio researchers and engineers, within the next couple of years, high-bandwidth, far-reaching wireless Internet signals will soon blanket the nation. Thanks to a decision by the Federal Communications Commission (FCC) last week, megahertz frequency bands that were previously allocated to television broadcasters will be opened to other device manufacturers. The frequency liberation means that future wireless gadgets will be able to blast tens of megabits per second of data over hundreds of kilometers. They will cover previously unreachable parts of the country with Internet signals, enable faster Web browsing on mobile devices, and even make in-car Internet and car-to-car wireless communication more realistic.
The FCC announcement essentially lets wireless take advantage of unused frequencies in between channels used by broadcast television, so-called white spaces. "The announcement that the FCC will allow white-space devices has a lot of people feeling like this is a beginning of a wireless revolution," says Anant Sahai, a professor of electrical engineering and computer science at the University of California, Berkeley.
For years, researchers have been toying with radios that are smart enough to hop from one frequency to another, leaving occupied channels undisturbed--an approach known as cognitive radio. But until the FCC made its announcement, cognitive-radio research was a purely academic pursuit. "You could do all the research you wanted on it," Sahai says, "but it was still illegal."
With the FCC decision, however, researchers and companies finally have the opportunity to turn prototypes into products, knowing that the gadgets could hit the market in the next couple of years. Companies including Motorola, Phillips, and Microsoft have all tested prototypes with mixed results and hope to have robust white-space devices soon.
Motorola is one of the first companies to have developed a white-space radio device that meets the basic requirements of the FCC. The device is smart enough to find and operate on free frequencies in its vicinity while controlling the strength of signals to keep them from interfering with those from other devices using nearby frequencies.
There are still lingering concerns over interference, however. This is one of the main reasons why white spaces have been off limits until now. Broadcast companies, which fund a huge lobby in Washington, were not keen on sharing their airwaves, and musicians were concerned that future white-space devices would interfere with performances using wireless microphones.
Motorola's radio finds occupied frequencies by accessing a database of registered television stations and wireless devices within its vicinity, which it determines by using GPS. Steve Sharkey, Motorola's policy director, notes that the device has a secondary way of finding free signals that involves just "listening" to the airwaves and scoping out free space. Sharkey believes that combining both methods will provide the best results.
