The company has wasted little time preparing to fill the vacuum. Last year, Microsoft Research set up a wi-fi–like network on its Redmond, Wash., campus to transmit high-speed data signals over white spaces using a technology the company refers to as "WhiteFi." Engineers from Microsoft's Networking Research Group received permission from the FCC last year to test a live WhiteFi network stretching over a 2.6-square-kilometer area of the campus to determine whether wireless devices would be able to get a high-speed connection without interfering with the TV broadcasts and wireless mics used in nearby buildings. "We needed to see what such a network would look like in the wild," says Ranveer Chandra, a researcher with the group.
One scenario enabled by Microsoft's WhiteFi network is the ability to give wireless users Internet access while they ride the 220 shuttle buses and cars used to transport employees and visitors around the company's city-size campus. The researchers installed a wi-fi access point in one such shuttle. The access points get their wireless signals from WhiteFi antennas set up last October and then hand off the connection to mobile devices on the shuttle via wi-fi. They rely on a prototype database Microsoft created to find vacant portions of the broadcast spectrum.
Microsoft Research continues to test its WhiteFi network. A particular area of interest moving forward is the WhiteFi's ability to divide spectrum channels so that a tablet PC, for example, could share that space with a wireless mic. Right now, this is a no-no—the FCC prohibits a white space device from sharing channels with wireless mics, even if that mic does not use the entire channel. The researchers are experimenting with ways to snag the unused portion of the channel for data transmission without interfering with that of the mic, Chandra says.
To ensure there is no interference, Chandra and his team are testing white space transmissions in an anechoic chamber, whose walls absorb sound to prevent echos and reverberations. In the chamber they record sounds via a wireless mic, at the same time exposing it to white space transmissions (they also make recordings without any white space transmissions). Then they analyze the quality of the recording using a set of standards known as perceptual evaluation of speech quality (PESQ), also used by phone-makers, network equipment vendors and telecom operators to assess voice quality. Their results show that vacating only a few 100 kilohertz of a six-meghertz TV channel is sufficient to avoid audible interference to wireless mics. The remaining spectrum can be simultaneously utilized for high-speed data communication.
Mobile phones, PCs and access points enabled for both wi-fi and white spaces could hit in the market in roughly two years, Reed says.
White space connectivity is needed, particularly as information technology reaches new heights—demand for wireless content will grow anywhere from five to 40 times what it is today within the next decade and a half, Reed says. The next big frontier is likely to be wireless video, which would let mobile phone users stream live video (a baseball game, for example) to their handsets with low latency. Wi-fi and cell networks are not prepared for this type of traffic, he says, adding, "Think about the challenges that carriers are facing now just to support smart phones."