The NAB today sharply criticized the credibility of an FCC report on white spaces. But in focusing on wireless interference issues that appeared in early field tests, the broadcasters appear to have ignored later test results.

A major TV broadcasting industry association today challenged the viability of an FCC report, calling for a period of public comment on whether devices operating in the so-called "white spaces" will interfere with broadcasting equipment if the spectrum is freed for public access.

In a statement, the National Association of Broadcasters pointed to "contradictions" between an executive summary issued on Wednesday and the full text of an earlier engineering report. The NAB contended that test results included in the earlier report clearly shows the spectrum sensing technology used in a Microsoft field trial "is not a reliable technique."

Specifically, the NAB's statement pointed to language in the full report stating that, during the test, "the Microsoft prototype sample device began to malfunction and eventually ceased to operate, necessitating the abandonment of further measurement utilizing this device."

However, the NAB's statement does not address the results of later FCC testing which revolved around the Android platform.

Also today, WIA members and other white spaces advocates held a press teleconference in which they pointed to challenges from the NAB and an unclear roadmap from the FCC as two possible future barriers to deployment of white space devices within the next year.

As previously reported in BetaNews, the WIA -- a rapidly growing group of computer industry vendors and telecom providers -- has been lobbying the FCC hard for free and public access to the white space spectrum. The NAB and the wireless microphone industry, however, strongly oppose that move, arguing that use of mobile devices in that spectrum will cause interference with TV broadcasting.

In the absence of a period of public comment, the FCC is now set to deliver a ruling on November 4 about opening up the white spaces around licensed spectrum to free and open access. If the ruling is in favor of the move, an implementation directive is anticipated in early December.

Back in February, Microsoft admitted that one of two devices designed and made by Microsoft's partner Metric Systems Corp. for use in white spaces had "experienced an apparent power issue."

"Testing at the FCC will continue with the primary Microsoft device and we are committed to providing the Commission with any further assistance it needs to complete testing successfully. We remain confident in the technology and look forward to the conclusion of the FCC's testing process which will expand broadband Internet access in underserved areas and enable a new wave of broadband devices and services," Microsoft said in a statement to BetaNews at the time. Then in March, Google proposed its Android platform as an alternative environment for mobile devices operating in the white space spectrum, also suggesting that interference could be prevented by combining "spectrum sensing" with two technologies already proposed by Motorola: "geo-location" for safeguarding broadcast TV and so-called "beacons" for preventing interference to wireless microphones.

The FCC later conducted field tests of Google's proposed approach, for example, but these results are not mentioned in the statement issued by the NAB today.