White Spaces Testing Provides Data, Not Conclusions, OET Chief Says

Knapp said OET will listen to industry advice on whether more tests should be done, including on the proper threshold for testing for broadcast signals and whether the -114 dBm level suggested by the White Spaces Coalition is suitable. He conceded that tests which might provide some answers to the last question would be time consuming and more difficult than the limited testing done. “Testing helps inform the process, but there’s a limitation to what you can do,” he said. FCC engineers did tests at the lab and in the field, checking potential interference to cable TV reception at townhouses in the Washington-Baltimore area.

“Engineers love to do tests,” Knapp joked: “The commission still remains committed to finding ways that we can make use of the white space spectrum without interfering with incumbent services… We're very open-minded as to what additional things can be done to make the technology work and to get this all done.” He noted repeatedly that the testing was on the cutting edge, since no manufacturer has developed a device for use by consumers. “We worked with the devices that we had,” he said.

Three of the FCC engineers who did the tests went over the data and how the tests were conducted. They fielded mostly technical questions from representatives of various companies and coalitions. The fight over use of the white spaces pits major high-tech players like Microsoft, Google and Dell against broadcasters and the companies that make and use wireless microphones, which already use the broadcast spectrum.

Meanwhile, the FCC received conflicting written advice from opponents and supporters of allowing mobile devices to use the white spaces spectrum for wireless access to the Internet. Comments were due Wednesday on the tests.

The White Spaces Coalition said the Microsoft device was broken and more tests are called for -- but a second device submitted by Philips shows that sensing works. “The OET Report confirms that white space devices can effectively detect both digital television and wireless microphone signals,” the high tech group said. “It also validates several of the fundamental claims made by the Coalition in this proceeding, including that spectrum sensing is feasible at -114 dBm for TV and wireless microphones.”

The coalition noted that OET didn’t notify Microsoft during tests when its device failed to perform as promised. It called for further tests, to be done in an “open and collaborative” way. “As representatives from Microsoft recently confirmed in an ex parte visit to the FCC Laboratory, the device’s scanner was severely damaged, making the Commission’s ultimate determination that the device it tested could not detect incumbent signals using the specified detection threshold a foregone conclusion,” the group said. “As a result, these sensing test results must be set aside. It belabors the obvious to say that any reliance on sensing data from a prototype with damaged sensing capabilities to establish the final operating rules for later, functional devices makes little sense, and could be arbitrary and capricious.”

A group led by the New America Foundation, the Media Access Project and the Cuwin Foundation said the OET tests show that mobile devices can use the white spaces without threatening TV broadcasts. The group questioned whether the bar set by the FCC is too high and called for more research to show what levels of protection are needed by broadcasters.

“OET should… regard the successful laboratory tests of the prototypes as establishing that even with today’s sensing technology, devices can identify incoming signals at strength levels well below what is necessary to protect television reception,” the group said. “It is critical to distinguish between the technical ability to sense a DTV signal at -114 dBm and the practical policy wisdom of prohibiting the constructive use of spectrum when the signal is this low, particularly where the typical DTV cannot display the signal, or where the signal is originating from a non-local TV market.”

But Hitachi Home Electronics, LG Electronics USA, Panasonic of North America, and Samsung Electronics told the FCC it should allow only fixed devices to use the spectrum. “The Commission’s recent reports confirm that without a robust geolocation requirement, unlicensed devices will deprive consumers of access to digital television on newly purchased DTV receivers (including cable-ready sets) and government subsidized digital-to-analog converter boxes,” the group said.

Banning the use of mobile devices like those promoted by the White Spaces Coalition will promote broadband deployment without posing a threat to the DTV transition, the manufacturers said: “With respect to the digital transition, the stakes could not be higher… More than 50 million DTV receivers are in the hands of the American public. Between now and the analog shutdown on Feb. 17, 2009, consumers will purchase over 60 million more receivers, plus millions of digital-to-analog converter boxes… Simply put, reception of digital television will be impaired if unlicensed devices fail to properly detect and protect a DTV station’s channel, or if they operate on a station’s first adjacent channel.”

The Microphone Interests Coalition also said the FCC should heed the result of OET’s tests and allow only fixed devices to access the white spaces spectrum. The coalition represents the American Federation of Musicians, the Grand Ole Opry and others that use wireless microphones. “As the Commission’s test report demonstrates, unlicensed low power devices, if permitted to operate in the band, cannot consistently sense or detect wireless microphone signals and could also cause direct interference to incumbent wireless microphone operations,” the group said. “OET’s testing confirms everything wireless microphone interests, including MIC, have said over the past three years. MIC is optimistic that the results of the testing will finally put an end to the debate about using the ‘white spaces’ of the TV broadcast channels for unlicensed personal and portable devices.”

The NAB and the Association for Maximum Service TV told the FCC that the OET tests left no room for doubt about the wisdom allowing portable devices to operate in the spectrum. “The Commission’s most recent reports in this proceeding lead to an inevitable conclusion: if let loose in the DTV band, personal/portable unlicensed devices will cause widespread disruption of digital television service. The ’spectrum sensing’ scanners used by these devices cannot reliably detect occupied digital television channels and are easily broken. There is thus no basis for authorizing personal/portable devices.”

Broadcasting groups said the Philips device didn’t perform well enough to show that TV broadcasts will be protected from harmful interference. “While the Commission’s tests of the Philips device indicate that the device performed better in the laboratory than the Microsoft devices, these results are incomplete at best,” the groups said. “Philips declined to subject its device to ‘real world’ field trials, but rather elected to test its device in the laboratory under pristine signal conditions.” The Philips device also failed to sense effectively at -116 dBm., they said. “While it is not yet clear what sensing level is necessary to ensure protection to all television viewers, what is certain is that the proposed -114 dBm and -116 dBm levels will fail to prevent harmful interference.”