Broadcasters hammered the FCC's upbeat take on its white space tests, saying the hype doesn't match the actual data in the FCC's own report.
NAB and others fought back at news of FCC Chairman Kevin Martin's far-reaching proposal to allow unlicensed devices in DTV white spaces—including on channels adjacent to occupied DTV channels—at power levels close to what was recommended by Google and high-tech companies. Martin's plan came as the FCC Office of Engineering and Technology released its report on its tests.
Friday NAB and the Association for Maximum Service Television, along with the major networks and the Open Mobile Video Coalition, filed what they called an "emergency request" to allow a period of public comment on the 400-page OET report.
(TV Technology columnist Doug Lung takes looks at the white space report in this week's RF Report)
If Martin has the support of two of his four fellow commissioners, he will even comply with the demand from Google founder Larry Page that the FCC deliver new rules by Election Day (Nov. 4). Martin has scheduled the vote for that day, but has frequently canceled or delayed votes when he didn't have the support he needed.
According to the plan as described by Martin Wednesday, there will be no licensing or auction of the frequencies. Portable devices that use both spectrum-sensing technology and geolocation databases to prevent interference to DTV would be limited to 100 mW of power, or 40 mW when operating on channels adjacent to active DTV channels. If the devices use only spectrum sensing, they would be limited to 50 mW, or 40 mW on adjacent channels.
MSTV said that the 40 mW level on adjacent channels would "eviscerate" DTV in some areas, particularly in cities.
Fixed devices would operate at a maximum of 4 W, and not at all on adjacent channels unless they can show to the commission that they can avoid interfering with DTV.
Broadcasters have attacked the reliability of spectrum-sensing technology, and the report notes the poor performance of some of the spectrum-sensing devices. But the OET says "proof of concept" was shown for spectrum sensing.
The power limits come close to a recent proposal by Google. Its regime would rely on geolocation but not spectrum sensing. For non-adjacent channels, it proposed maximum power levels of 36 dBm (about 4 W) for fixed devices and 20 dBm (100 mW) for portable devices.
Broadcasters have called for lower power levels. MSTV wants no fixed devices in adjacent channels and portable devices at just 5 mW on those channels and 10 mW on the other channels.
The OET report shows a mixed performance by the devices. On spectrum sensing, OET said in most cases, the devices correctly reported channels as occupied when the device was operated within the service contour of the stations broadcasting on those channels and signals were viewable.
But in some instances, devices from Adaptrum, the Singapore-based Institute for Infocomm Research (I2R) and Motorola (in sensing-only mode) incorrectly reported channels as unoccupied (available) even inside a station's service contour and when the signal was viewable.
Furthermore, there were many false positives. All of the devices reported some channels as occupied outside of the service contours of stations broadcasting on those channels whether the signal was viewable or not.
The device from Philips had the most false positives, said OET. It generally reported most channels occupied, whether operating inside or outside any service contours and whether the signal was viewable or not. It had similar problems with detecting wireless mics. "At both sites and all the test locations, the Philips device reported all the channels on which the microphones were designated to transmit as occupied whether the microphone was transmitting or not," OET reported, referring to mic tests at FedEx Field in Maryland and a theater on Broadway.
MSTV said the technology was not ready for prime time.
"These devices failed to differentiate between an occupied and unoccupied TV channel nearly 33 percent of the time. Specifically, our analysis of the data reveals these devices have a 'sensing error rate' ranging from 26.9 percent to 37.3 percent," MSTV said in a statement. "Allowing millions of unlicensed devices, which rely exclusively on sensing to avoid interference, on to TV channels will decimate digital television reception across the country."
NAB said the discrepancies between the OET data and its own report were "curious" and the contrasts "stark"
"It would appear that the FCC is misinterpreting the actual data collected by their own engineers," said NAB Executive Vice President Dennis Wharton in a statement. "Any reasonable analysis of the OET report would conclude that unlicensed devices that rely solely on spectrum sensing threaten the viability of clear television reception. Basing public policy on an imprecise Cliffs Notes version of a 149-page report raises troubling questions."
Motorola got a thumbs-up for its use of a geolocation database in combination with spectrum sensing. "The Motorola device correctly reported all occupied channels used by stations within whose contours the WSD was operated," OET said of one set of tests.
Motorola Senior Director for Regulatory and Spectrum Policy Steve Sharkey said the report, from what he'd seen, was "extremely positive," although the public won't see any more details of the plan until after it's voted upon.
"It really affirms what we've been saying, that the devices can protect the incumbents," he said.
He predicted the FCC, concerned about interference, will be conservative with the devices allowed, but reach a higher comfort level as manufacturers develop and test more devices.
He said the rules will probably be sufficient to allow manufacturers to actually start building devices. The kind of devices and service may vary wildly from company to company, ranging from in-home networking to rural wide-area wireless broadband.
MSTV said the record was insufficient for writing a rule. "It is difficult to see how repeated failure proves the concept," MSTV said. "Failure means the FCC does not know the sensing level that is necessary to protect TV viewers. As a result, the FCC will not know if devices built to any proposed 'sensing' rules will be sufficient to protect consumers. Moreover, after nearly four years, white spaces advocates have failed to build a device that works under controlled experimental conditions. There is absolutely no reason to believe that they will be able to build a device that will work in the real world."
