Most broadcast channels are separated by small swaths of spectrum, or unused channels called, which limit interference from other stations. Technology companies and consumer advocates believe the use of this unlicensed spectrum could open up a wireless broadband pipe into the home, providing a competitor to cable and DSL services.
Technology companies in particular say that using the spectrum between the TV channels could unleash a wave of innovation. These companies, which include Microsoft, Intel, Google, EarthLink and Dell, have joined forces. Calling themselves the White Space Coalition, they've been lobbying the FCC and Congress to open up this spectrum.
Not surprisingly, TV broadcasters oppose allowing any unlicensed device to use white-space spectrum because, they argue, these devices would interfere with television broadcasts, potentially harming the federally mandated transition from analog to digital TV service.
"There are serious interference issues with unlicensed devices," said Dennis Wharton, spokesman for the National Association of Broadcasters. "Our suggestion to the FCC is, let's get through the analog transition to digital TV before we suggest introducing unlicensed devices onto airwaves that could cause disruption to millions of TV viewers."
Congress has mandated the airwaves in the 700MHz band be vacated in February 2009,as part of the long-anticipated switch to all-digital television. are eager to get their hands on the spectrum because of its inherent physical properties, which allow signals to travel farther and more easily penetrate walls.
Countering Wharton's argument, the White Space Coalition says that it can design devices that don't interfere. And it submitted prototypes to be tested by the FCC earlier this spring.
Testing of these devices has recently been completed with mixed results. On July 31, the saying that a testing prototype developed by Microsoft failed to detect digital TV signals in order to avoid them in tests designed by the commission. But another device, made by Koninklijke Philips Electronics, was able to detect broadcast signals, according to the commission's report.
Microsoft is now saying that the results of the FCC test are invalid. In a letter it filed this week with the FCC, Microsoft said the device the FCC tested was defective. And another model of the same device worked successfully in a demonstration it gave to the FCC last week, according to the letter.
"We don't think anything the commission did in its testing in any way diminishes the potentiality of white-space devices," said Ed Thomas, former chief engineer at the FCC and now technology policy adviser and partner at Harris Wiltshire & Grannis, the firm representing the White Space Coalition. "We still believe that the white spaces could be used without causing harm to broadcasters. And we want to work with the commission to product the services of incumbent licensees."
What is white space and why should I care?
The FCC has had an open proceeding on the possibility of using this spectrum since 2002, but it still hasn't taken any action. The FCC's office of engineering and technology plans to hold an open meeting Thursday to discuss testing options for new white-space devices.
Today, both the 700MHz and white-space frequencies are used to deliver analog TV service. But when, the 700MHz spectrum, which includes broadcast channels 52 to 69, will be auctioned off. And spectrum between channels 2 to 52 will essentially lay fallow. Public policy experts see this transition to digital as a perfect opportunity to make spectrum available for new players who want to compete in the broadband market.
On their own, these slivers of wireless spectrum are not sufficient to provide enough capacity for companies to build wireless broadband services that truly compete against high-bandwidth services offered by the cable and phone companies. But combined with other pieces of spectrum, like Wi-Fi, this spectrum could provide enough capacity to deliver competitive services.
"The 700MHz spectrum is not enough to compete against a service like Verizon's Fios," said Harold Feld, senior vice president of public-interest nonprofit Media Access Project, in reference to Verizon Communications' high-capacity network featuring fiber-optic connections to the home. "It's only 62MHz of spectrum. So you're going to need a lot more. That's why it's important to provide access to licensed as well as unlicensed spectrum."
The amount of spectrum that is available in white spaces varies from market to market. In rural areas where fewer broadcasters are operating, it can provide a substantial amount of capacity. But in dense urban areas, white spaces offer far less capacity because more broadcasters are using the spectrum. For this reason, white-space spectrum could be particularly valuable for providing broadband access in rural areas, where large cable companies and telephone companies have not built wired infrastructure.
But it also could be used in urban areas. Because white-space spectrum is unlicensed and, therefore, free to anyone who wants to use it, it makes a nice complement to citywide Wi-Fi networks. Wi-Fi operates in the higher frequency bands of 2.4GHz and 5.0GHz. But because it's at a higher frequency, it propagates over much shorter distances and has difficulty penetrating walls and sometimes even foliage.
White-space spectrum in the analog channels, which operate between 54MHz and 698MHz, provides an inexpensive way for service providers such as EarthLink, which is building citywide Wi-Fi networks, to extend their reach and improve in-home coverage.
And now that theto that spectrum, access to white-space spectrum is even more important for prospective competitors of the cable and phone companies.
"We didn't get the open access that we wanted on the 700MHz auction," Feld said. "So it makes it that much more important that new providers can access white-space spectrum."
But broadcasters say they don't think it's possible to solve the interference issues. With roughly 15 percent to 20 percent of the TV-viewing public still getting their TV service over the air, Wharton said, the risk is still too high.
"If there was ironclad proof that no person in America would lose access to over-the-air TV signals, then maybe we wouldn't have a problem with the introduction of unlicensed portable devices," he said. "But engineering studies and folks that we have talked to say the likelihood of developing a product that wouldn't interfere with TV broadcasts in large markets is nil."