MICRO MOBILITY: Microsoft Research set up a WiFi-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." The company believes that mobile phones, PCs and access points enabled for both WiFi and white spaces could hit in the market in roughly two years. Image: COURTESY OF MICROSOFT
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Consumer electronics companies got an early Christmas present this year when the Federal Communications Commission (FCC) decided to grant unlicensed smart phones, computers and other wireless devices approval to connect to the Internet via vacant "white space" airwaves. Exactly which Christmas, however, is less clear—consumer electronics–makers wanting to take advantage of broadcast spectrum space abandoned as a result of last year's shift to digital television have much work ahead of them to meet the requirements laid out by the FCC.
In a formal ruling on September 23 the FCC assured broadcasters and incumbent users of the spectrum that they will be protected from interference by new, unlicensed wireless gadgets seeking to use white spaces. In a statement (doc) the agency called its move the "first significant block of spectrum made available for unlicensed use in more than 20 years."
In addition to the requirement that mobile phones, netbooks, tablets and other devices have access to the information needed to determine their position and consult an FCC-approved geographic database listing licensed broadcast spectrum users (in particular, TV stations) in their area, the FCC reserved two vacant UHF channels for licensed wireless microphones and other low-power auxiliary service devices in all areas of the country.
The FCC's decision is a boon for Internet addicts, who can look forward to faster, more reliable wireless connections via the broadcast spectrum. White space access is also a shot in the arm to makers of mobile devices (as well as the operating systems, apps and chips that these gadgets use) who covet the broadcast spectrum's low-frequency waves, which have strong propagation characteristics allowing the signals to reach farther than wi-fi and penetrate walls and other impediments (doc).
Spectral sensing suspended
The FCC eliminated the requirement that wireless devices have built-in spectral sensing capabilities that can detect whether a white space is being used before connecting to the Internet, as long as those devices have geolocation capabilities and access to the FCC-approved white space database (yet to be created). The agency has not ruled out the use of spectral sensing in the future, but it backed away from demanding such technology over concerns that it could not be done accurately at this time and that such a capability would be a serious drain on wireless device batteries.
There has been a swing away from the spectral sensing approach because it was deemed too difficult to do at this time, says Luke D'Arcy, head of cognitive radio at Cambridge Consultants, a company that stands to gain much by the FCC's ruling. Cambridge is developing a product called InCognito, a package of microprocessors, circuit design and software that makers of mobile phones, computers, set-top boxes and wireless base stations can use to enable their devices to find available white spaces by linking up to the free-spectrum database when it becomes available.
The InCognito platform, however, also supports spectral sensing technology, which can detect free spectrum when the database is not available (for example, when the white space device is not connected to the Internet). Part of the FCC's ruling lowers the spectral sensing requirements, making the design of the sensor significantly easier than originally expected, D'Arcy says. If the device does not have to work as hard to detect white space, such searches will be less of a threat to battery life.
Microsoft chose a different path, feeling "strongly" that a database lookup function was sufficient in lieu of a spectral-sensing capability that could probe white spaces to see if they are being used by an FCC-licensed user at any given time, says Dan Reed, head of Microsoft Research's eXtreme Computing Group. The argument is that, if the database indicates vacant white space in the area of a laptop or mobile phone, that device should be able to connect to the Internet via that white space without interfering with local TV stations or wireless mics.