Monday, December 1, 2008
Gadgets that operate over television frequencies promise to transform the wireless landscape.
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.
Motorola's early tests show that there's still work to be done. During an FCC trial in October, Motorola's device, which is about the size of a suitcase and can currently only receive signals, was able to find some but not all of the allocated frequencies in its vicinity. "These aren't ready to go," admits Sharkey. "They are more developmental devices, and the idea of the test is to demonstrate the basic technologies and help the FCC understand all the interactions [between transmissions]."
While eventually it may be possible to shrink down a white-space radio to the size of a cell phone, Sharkey says that Motorola is more focused on bypassing wired Internet technology by providing broadband to rural areas and providing point-to-point wireless antennas.
Other companies are more reticent to talk about their white-space plans, but Jake Ward, spokesperson for the Wireless Innovation Alliance, a consortium of companies that helped convince the FCC to open up white spaces, says that these companies have a wide range of motives. For example, computer manufacturers such as Dell may want to build broadband wireless Internet cards that are faster and have more range than existing ones do. Software companies like Microsoft could be interested in building software and applications for new devices. And an Internet giant like Google may simply want to push Internet coverage to increase the number of people who see Google ads. "Each company has its own interests," Ward says, "but the underlying principle is that higher connectivity is better for everybody."
Ward describes one white-space application as "mind blowing": sending high-definition television signals from one room to another within a house. "You have a TiVo, a DVD player, a cable box, and three high-definition TVs," he says. "Using a white-space device, you could beam those signals anywhere, to any TV."
Of course, technical and policy challenges still remain. "Right now, a device capable of moving around to different frequencies at will is very expensive," notes UC Berkeley's Sahai. But he suspects that economies of scale will lead to affordable devices within the next couple of years. Additionally, he says, regulations need to be established to ensure that devices consistently avoid causing interference. Ultimately, however, Sahai sees no shortage of demand for the wireless spectrum. "If you build it better and faster and easy to deploy, then the applications will come," he says.
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