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In its second memorandum opinion on white spaces issued Thursday, the FCC removed the requirement that devices operating on TV bands have built-in sensors that would automatically shut down the devices if they came into contact with an adjacent television signal. That requirement had originally been put in place to satisfy concerns of television broadcasters that were worried that unlicensed use of white spaces could interfere with their broadcast quality.
Instead of requiring white-space devices to have sensing technology, the FCC now says that giving devices geo-location capability and access to a spectrum database will be sufficient to protect broadcasters' spectrum from interference. Geo-location databases are designed to track mobile devices by locating them through their specific IP address, media-access-control address, radio-frequency identification or other location-based information. Once the database has a fix on the device's location, it then selects the optimal white-space spectrum for the device and can even switch the device to a different spectrum once it moves to a different location.
The FCC said its reason for eliminating the sensor technology requirement was that the technology had not yet evolved to the point where it would be especially useful in helping to preserve television broadcast quality. Additionally, the FCC said that requiring sensing technology would place an unnecessary burden on manufacturers when simply providing access to the spectrum database would be sufficient.
"The geo-location and database method is already the primary means for preventing interference to TV stations," wrote the FCC in its order. "We continue to believe that spectrum sensing will continue to develop and improve… however, at this juncture, we do not believe that a mandatory spectrum sensing requirement best serves the interest of the public."
Television "white spaces" are pieces of unlicensed spectrum that are currently unused by television stations on the VHF and UHF frequency bands and that have long been seen as prime spectrum for unlicensed wireless Internet services. In 2008, the FCC, then headed by former chairman Kevin Martin, voted to let carriers and other vendors deploy devices in white space spectrum that operates unlicensed at powers of 100 milliwatts, as well as on white space channels adjacent to existing television stations at powers of up to 40 milliwatts.
The debate over white spaces has been a contentious one, with tech companies such as Google and Microsoft pitted against all the major broadcasting companies, as well as major telecom carriers such as Verizon. Proponents of unlicensed white space use have often argued that opening up the spectrum would help bring mobile broadband to under-served regions and would help close the so-called "digital divide" between many urban and rural areas in the United States. On the other side, the National Association of Broadcasters has argued that mobile Internet devices cannot operate on unlicensed spectrum without clashing with broadcasts on nearby frequencies.