Spectrum ‘spaces’ hold allure for technology companies
According to some high-tech companies, access to white spaces is "a once-in-a-lifetime opportunity to provide ubiquitous wireless broadband access to all Americans." Such devices could, in turn, spawn a large market for chips, just as the Wi-Fi market did.
By Tam Harbert, Contributing Editor -- EDN, April 29, 2008
The high-tech industry and TV broadcasters battled for decades over whether and how to switch television from analog to digital channels. Now that the transition is imminent, they are battling over what to do with the spectrum in between those channels.
Once TV makes the transition to digital next February, there will be a large swath of such spectrum, called white spaces, lying fallow. “We’re talking about 40 to 70 megahertz of very good spectrum that could be available at any given place at any given time,” Richard Whitt, Washington telecom and media counsel for Google Inc, said. The tech industry covets that spectrum because it has propagation characteristics that would allow data, video, and audio to travel farther and penetrate obstructions better than Wi-Fi. Tech companies argue that this is an opportunity to create a whole new market for devices that could stream video, control home-automation systems, and enable mesh networks, to name just a few. Google, whose business model depends on more consumers using the Internet more often, calls access to white spaces "a once-in-a-lifetime opportunity to provide ubiquitous wireless broadband access to all Americans." Such devices could, in turn, spawn a large market for chips, just as the Wi-Fi market did.
High tech has ratcheted up the pressure on the US Federal Communications Commission (FCC) to approve the unlicensed use of the spaces for wireless applications. But several politically powerful groups, including TV broadcasters, wireless mobile service providers, and wireless microphone manufacturers, oppose that idea, arguing that such devices could interfere with their transmissions. The technology industry is pushing for the FCC to make a decision by late summer. If the issue drags on any longer, it fears, the FCC may move the issue to the backburner in anticipation of a new administration in the White House.
The FCC has been investigating the issue for several years. In October 2006 it ruled that white spaces could be used for high-power fixed broadband deployments, but called for further study on whether low-power portable devices could also use these airwaves without causing harmful interference. The key to opening this potential market is whether the technology industry can demonstrate the viability of cognitive radio, i.e. radios that use spectrum sensing algorithms sophisticated enough to enable these new devices to detect that a TV signal is using the channel and then immediately jump to a different channel. While it has seen limited use in the military, cognitive radio has not yet been widely used in commercial applications.
Several major companies – including Google, Microsoft, Intel, Dell, Hewlett-Packard and Philips – formed a coalition last year to lobby for freeing up the white spaces. In addition, four individual companies submitted prototype devices to the FCC for testing. Coalition members Microsoft and Philips submitted devices in spring of 2007. Last fall, additional devices were submitted by Motorola and from a tiny startup, Adaptrum, founded by Robert Broderson, an engineering professor at the University of California at Berkeley and co-founder of Wi-Fi chip vendor Atheros Communications Inc.
Each of the prototypes attempt to prove that spectrum sensing technology adequately detects incumbent signals from interference. But there have been problems. The FCC reported last summer that the initial devices did not consistently sense or detect TV broadcast or wireless microphone signals. Then the Microsoft device broke down – twice.
That has given opponents ammunition to argue that spectrum sensing won’t work. “It’s quite clear from the FCC tests that there are serious flaws in all the spectrum sensing technologies that they’ve looked at,” said David Donovan, president of MSTV, the Association of Maximum Service Television, which is the technical association of the broadcast industry.
But the operational failures of the prototypes have nothing to do with the efficacy of the technology, according to Steve Sharkey, Motorola’s director of spectrum and standards strategy. “The testing is not intended to see if any device passes or fails,” he noted. “It’s intended to give the FCC an understanding so that they can set the rules.”
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Nevertheless, the opponents’ objections and political power threaten to stop FCC action on the issue. So in March Google tried a different tack and proposed including some additional technologies to protect against interference. “We still think spectrum sensing can work, but it’s not clear at this point whether the commission has the comfort level, at least with the current round of testing,” said Whitt.
Whitt characterized Google’s latest proposal as an attempt to reach out to both broadcasters and wireless microphone vendors. For the TV broadcasters, Google suggested that white-space devices be required to incorporate both Internet access and some type of geo-location technology, such as GPS. That way, the devices could check an online database, maintained either by the FCC or a third party, of licensed users of the spectrum at a particular location at a particular time. For the microphone makers, Google proposes setting aside three channels for their exclusive use plus incorporating beacons into the microphones that would send a clear, definitive signal warning all other devices to stay out of its spectrum.
But some high-tech companies fear that Google’s proposal might prompt the FCC to drop its investigation into spectrum sensing technology and therefore eliminate a large part of the potential market for white space devices. “The problem is that requiring geo-location and Internet access makes devices more expensive, and it effectively prohibits a number of applications that the other companies have in mind – for example, networking devices around the home,” said Michael Calabrese, VP and director of the Wireless Future Program at the New America Foundation, which favors unlicensed use of white spaces.
In April the FCC’s Office of Technology Policy was expected to finish its bench tests and begin field tests, which could last till the end of June. Within the next several weeks, Philips plans to demonstrate on behalf of the high-tech coalition a complete cognitive radio system running various applications over white spaces, according to Kursat Kimyacioglu, director of wireless business development at Philips Research of North America.
High-tech companies are hoping for a ruling from the FCC by October of this year. If approved, consumer devices using cognitive radio technology could be on the market anytime after the digital TV transition date of February 19, 2009.
For more information, see:
FCC web page of OET’s TV band device testing
NAB comments on OET’s tests of white space devices
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I find it hard to believe that no one has suggested an obvious solution
for using the extra spectrum. Perhaps 10MHz could be set aside as a
new ISM type band. Look at the success of the 900 and 2.4GHz
unlicensed devices. Rather than giving all of the pie to one company
like Google or Microsoft, let the market decide.
Peter J. Merkin - 2008-7-5 13:47:00 PDT
