FCC Nears End of White Space Spectrum-Sensing Field Tests
August 1, 2008
At FCC headquarters in Washington and at residences in Maryland, the FCC Office of Engineering and Technology has completed its third week of white space field tests.
Four companies—Motorola, Philips, Silicon Valley startup Adaptrum and, from Singapore, the Institute for Infocomm Research—have devices submitted for the tests, which are focusing on their ability to sense, and thus avoid, channels occupied by DTV signals or those of wireless microphones. The devices consist of tuning units connected to computers, where hardware and/or software analyze the signals to see if they really represent occupied channels. Operators could see the progress on video interfaces. In tests at FCC conference rooms July 29, commission staff ran the devices through their processes. In each case, the devices identified occupied and unoccupied channels, although not necessarily the same ones each time. In general, the devices are testing for signals far below what would make a viewable TV picture, thus requiring the computers to distinguish real signals from background noise. “So far we are quite pleased with the results of the Philips device in all of the field tests,” said Monisha Ghosh, principal member of the research staff for wireless communications and networking with Philips Research, based in Briarcliff Manor, N.Y. The Philips device spends 40 milliseconds checking for signals on each channel, and scans continuously. Under its prototype system, a device would thus be able to detect new signals that turn up during use, and then switch transmission to a vacant channel if necessary. Philips demonstrated such transmission, of high-definition video signals at the FCC in June, according to the company’s filings. Philips envisions uses such as home networking and, through a mesh network, applications such as rural broadband and local networks. But proponents figure they might dream up all sorts of future applications. “The technology allows for lots of innovation to occur,” said Paul Simonetti, director of corporate stakeholder relations for Philips Electronics North America. The July 29 field tests also included test detection of a wireless mic. Motorola’s device, alone among the four being tested, uses a geolocation database to rule out channels already known to be occupied. The tests are open to the press and public, and a representative of the Association for Maximum Service Television has attended each test. Google, which has expressed interest in white space technology but does not have a device in the tests, sent a lawyer to watch the July 29 tests. FCC staff said a report on the data from the tests would likely be issued this summer. The current testing schedule calls for field tests to continue the week of Aug. 4-8, with tests at a sports venue and an entertainment venue also to be conducted, at times and places not yet specified. Broadcasters and wireless mic users have warned that white space devices, especially under an unlicensed regime with millions of portable consumer devices, could create problems. “To date, the poor results obtained from this testing strongly suggests that allowing the use of unlicensed devices in the TV ‘white space’ would cause serious interference to both existing television broadcasts and virtually all licensed microphone users,” the National Religious Broadcasters said in a letter to FCC Chairman Kevin Martin July 30. “We believe that if this problem is allowed to continue unaddressed, it might be one of the greatest technical blunders in our nation’s history.” Rep. Carolyn Maloney, D-N.Y., who represents part of Manhattan, also wrote the commission, echoing concerns of the Broadway League, which represents New York’s famed theater industry. Maloney said the devices now being tested fail to adequately protect wireless mic users. “I am increasingly concerned that the white space device manufacturers are attempting to strong arm the commission to approve new technology that is not yet fully tested,” she wrote.
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