CEA Supports Extending Deadline in TV ‘White Spaces’ Proceeding

Like the IEEE advisory group and others, CEA is asking the Commission for a 180-day extension beyond the current deadline of Sept. 1 for comments and Oct. 1 for replies. CEA hailed the work of the FCC to allow operation of unlicensed devices in the vacant broadcast TV bands, but said “we must ensure that unlicensed devices do not interfere with broadcast TV reception.” Intel and others, however, said a 180-day delay would stall the progress of technology.

To thwart possible interference, CEA said it has begun discussions with other players and needs more time “to develop consensus solutions to interference concerns.” CEA said it plans technical studies and “multi-faceted field- testing that will involve multi-industry cooperation.” It said it’s committed to finding technical solutions that will allow unlicensed use of vacant TV channels without causing interference. “In order to best serve the public interest,” CEA said, more time is needed “to provide a complete and thorough technical analysis” of the FCC’s complex rulemaking.

CEA’s request came as little surprise, since it had told the Commission in an ex parte filing a week earlier it might seek an extension because it would be “virtually impossible to make reasonable measurements in the comment filing period” as a result of its field tests. Harris Corp. agreed, telling the FCC that broadcasters “have been working cooperatively” within the 802.18 advisory group with the CE, public safety and wireless industries to develop “potential solutions” for the unlicensed sharing of vacant TV channels without causing interference. Advisory group members are evaluating one such “interference avoidance” proposal, Harris said. The advisory group has scheduled meetings for Sept. 12-17, Nov. 14-19 and Jan. 16-21 to discuss this and other proposals, it said. “This cooperative effort, when completed, will provide the Commission with industry-wide recommendations” on which to base its final rules, Harris said. Without such input, the FCC will be basing its decision “without valuable insight” from the advisory group, which “represents all interested stakeholders,” it said. The public interest benefits from granting a 6 month delay would outweigh “any potential disadvantages of extending the deadline,” Harris said.

In its earlier ex parte, CEA said it fundamentally supports the Commission’s rulemaking on the use of unlicensed devices in vacant TV channels, “as long as protection of TV services is assured.” Among its concerns, CEA told the FCC, was there was no guarantee a control signal would stay within its “protection contour.” If that control signal were received by a portable device outside the protection contour and within a neighboring contour, “interference will necessarily result,” CEA said. Although the rulemaking provides for protection within a station’s Grade B contour, TV set-makers don’t believe protection should be limited to Grade B, CEA said.

CEA said it considered questions raised in the rulemaking about the use of “spectrum-sensing” techniques for unused channel detection “an area of active discussion and testing.” As for assumptions raised in the rulemaking that unlicensed devices would be kept more than 10 meters from “victim” TV receivers, CEA said the distance was “unrealistic in urban settings, in apartments, in condominiums and even in many suburban homes.” Unchecked, CEA said, strong unlicensed signals on channels near the desired TV channel can cause the automatic gain control on a TV set to reduce tuner gain, “impairing the reception of weak TV signals.”

In its field tests, CEA said it plans to measure ambient environmental noise around a PC and other devices to guide the studies on spectrum-sensing. To test “reception diversity,” CEA said it will record “spectral plots” of ATSC and NTSC signals using an outside antenna at 30 ft., comparing the results with those of indoor reception using a dipole antenna. Any differences would affect the ability to detect a vacant channel or receive a control signal, it said.

To measure for possible adjacent channel or out-of-band interference, CEA said the tests will record actual ATSC and NTSC out-of-band emissions as well as those of a “mockup” unlicensed device. The tests will allow for a variety of different scenarios, CEA said; for example, they'll measure the effect of filling the band with relatively strong unlicensed signals in a weak TV signal reception environment. The tests also will measure “worst case” field strength from an unlicensed device to assess “tuner overload,” CEA said.