01.23.2007 08:00 AM
Broadcasters cast wary eye on unlicensed device proponents

Broadcasters, who have as an industry spent billions on their DTV conversion and are in the early stages of putting HD production capability in place, couldn't be blamed if they were a little apprehensive this past weekend.

That's because Jan. 19 was the date by which the FCC Office of Engineering and Technology wanted to receive notification from parties wishing to market low-power unlicensed devices that operate on so-called white spaces in the TV spectrum of their intent to submit prototypes for testing.

While the commission hasn't yet made public a list of those wishing to participate, what is known is that Friday's notification deadline is the first step of many toward what proponents of such devices hope will be FCC permission to operate in the TV band — something that makes many broadcasters uneasy.

"I am nervous about the whole process," said Sterling Davis, vice president of engineering for Cox Broadcasting. "If it is done in a controlled way where you know where the transmitter is and how much power there is, you can deal with it."

What makes broadcast engineers like Davis apprehensive is that even if smart or cognitive technology is built into such devices to prevent them from operating on a band used by a TV station, adjacent channel interference can wipe out DTV reception in a whole apartment building or block, he said.

According to the Association for Maximum Service Television president David Donovan, first-adjacent channel interference can have an impact on DTV receivers up to 2500ft, and co-channel interference can disrupt reception for miles — especially in low signal strength areas, he said.

Del Parks, vice president of engineering and operations for the Sinclair Broadcast Group, questioned how the commission could proceed with testing without first defining DTV receiver standards. "At the very heart of this issue is a receiver standard. What are the expectations for the receiver? It can be built with a very sloppy front end or a front end that rejects adjacent channels," he said. "What's acceptable interference? Zero. And how can you assure that? The answer is you would have to know the receiver parameters, and they are all over the map. Even if they use the same chip, the front ends can be different."

The high-tech industry has expressed a strong interest in using white spaces between occupied TV channels for new devices. The government in general, and FCC chairman Kevin Martin in particular, are proponents of expanding broadband Internet access nationwide. Using portions of the TV spectrum between occupied channels is seen as a possible solution for delivering wireless broadband service to rural areas of the country where running coax or fiber is too expensive or simply impractical.

"There's always been a little bit of bait and switch when it comes to these unlicensed devices," Donovan said. "They are sold [to policymakers and regulators] on the basis of helping rural broadband, but that's not what companies like Microsoft and Intel want. They want handheld portable devices. The two are very different."

Davis has similar suspicions about where these devices will be used. "The big companies pushing this say, 'Rural, rural, rural,' but they aren't spending all of that money just for rural," he said.

Broadcasters who have spent large sums building out their DTV transmission facilities will be casting a watchful eye on the commission to learn what sorts of devices will be tested and how they will perform to head off a potentially huge problem before it occurs.



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