Motorola is resubmitting its digital-TV white-spaces device to the Federal Communications Commission Wednesday with modifications that the company said will help it to perform better when there are strong TV signals on adjacent channels.
Motorola is one of three companies with prototype unlicensed wireless devices being tested by the FCC to see whether/how they can be allowed to share the DTV spectrum with TV stations.
Steve Sharkey, senior director of regulatory and spectrum policy for Motorola, conceded that the company's prototype "cognitive radio" had trouble when the FCC injected strong adjacent-channel signals into the mix, which means that it could potentially use a channel that was already occupied. But he argued that it was a test Motorola hadn't expected, so the device wasn't prepared to handle it.
The devices are supposed to seek out unused frequencies on which to transmit, but broadcasters fear that they will instead try to use occupied channels and cause interference to TV signals. Initial FCC testing of TV sets found that spectrum-sensing devices interfered with them. Then, in more recent testing of the prototypes, Microsoft had to withdraw its device after it malfunctioned.
Since the FCC did not include the strong adjacent-channel interference test in the first round of testing, Sharkey said, Motorola did not anticipate that it would be part of the testing. "We’ve adjusted the device accordingly," he added.
Sharkey said the modification was not the result of a failed prototype, but of adjustments "to the test conditions these devices are being put through."
He added that the testing is not about a particular device, but about giving the FCC the information it needs to come up with rules and standards. He said whatever those are, Motorola will meet them. "As soon as the FCC defines the protection criteria and tests for actual devices that will be tested after the rules, our devices will meet that," he said. "Going into the test, there wasn't a clear set of guidelines for what the conditions of the tests will be."
Sharkey said the FCC is scheduled to begin two days of testing Wednesday morning. The agency in March extended lab testing on the devices and is expected soon to move those tests into the field.
The commission is under a mandate to boost spectrum efficiency and broadband deployment, both of which the devices' backers argued would be served by allowing them to share the spectrum with DTV stations. But while expressing confidence in a technological solution, the FCC commissioners have also said that the devices must not interfere with DTV signals.
Broadcasters said there is essentially no way to assure that unlicensed devices will not cause interference, potentially jeopardizing the DTV transition.
David Donovan of the Association for Maximum Service Television (MSTV) has been making broadcasting's case against the unlicensed devices. "It appears they are trying to coorect their past failures," he says.