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NAB, Microsoft Spar Over TV White Spaces Signal Availability Determination

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(Image credit: Future Media)

Broadcasters are telling the FCC that using a popular method of determining signal reach could undo the good work the commission has done to help them better serve the public.

It is the latest volley in the battle between broadcasters and computer companies--specifically Microsoft--over opening up the TV band for more unlicensed (so-called TV white spaces, or TVWS) broadband use. 

That volley came in comments by the National Association of Broadcasters to the FCC this week on a Further Notice of Proposed Rulemaking (FNPRM) approved last October.

The FCC voted in October to open TV white spaces to higher powered wireless devices, saying it could do so while protecting those TV signals from potential interference. That item, which was approved unanimously, was based on a petition by Microsoft for more spectrum and an agreement between the computer company and NAB on how to do that while protecting incumbent broadcasters.

But the FCC also approved the FNPRM, which sought input on how to determine where Microsoft and others could use the spectrum without interfering with broadcasters. Microsoft suggests using the familiar Longley-Rice terrain-based model. NAB said definitely not. 

That is the model the FCC used to determine coverage areas in repacking TV stations after the broadcast incentive auction. Broadcasters weren't so happy with its use in updated form there, either.

The FCC currently defines white spaces in reference to a station’s protected contour. Microsoft said Longley-Rice will provide a more accurate picture of where available channels are. NAB said it definitely won't. It argues the model has an unacceptably high error rate.

In comments filed this week, the association said using that terrain-based propagation model, with its high error rate, would lead to "harmful interference to television service in pursuit of marginal, and likely illusory, gains in spectrum efficiency.

It suggests the Longley-Rice predictive model is not nimble enough to account for differences in seasonal foliage or atmospheric conditions, or individual antennal performance characteristics, and so will wind up allowing TVWS operations that cause interference. Plus, it said, getting that more precise information on which to predict channel availability is a nonstarter because "there is no remotely accurate way of determining the precise location of individual television receivers that might allow for more granular determinations of coverage."

NAB also argues that the commission doesn't want to reverse the gains it has made toward a more robust broadcast service, including allowing for greater flexibility in the use of distributed transmission systems and authorizing deployment of ATSC 3.0, so-called Next Gen TV. Combined with the changes the FCC has already made, per that Microsoft/NAB agreement, to authorize higher power TV white spaces devices, greater antenna heights and more, NAB said this is exactly the wrong time to change the way the FCC determines channel availability, "risk[ing] more interference in the very areas where television coverage is already challenging at the very moment when broadcasters are trying to improve it."