Static Over Bandwidth
Willl allowing wireless devices on a market's unused channels interfere with stations' signals?
By Bill McConnell -- Broadcasting & Cable, 10/3/2004 8:00:00 PM
For almost 50 years, TV stations have had a valuable slice of the airwaves almost entirely to themselves. Soon, however, their gated community could become considerably less exclusive.
To accommodate the explosion of wireless products and the resulting demand for spectrum, the FCC wants to squeeze a gaggle of new gizmos—including computer printers, Blackberries and high-speed Wi-Fi networks—into the handful of TV channels that lie vacant in every market.
Although the government's plan has gained little notice among network chiefs and station owners, TV engineers and others keeping tabs on TV-technology policy are worried. They warn that adding a host of new consumer devices into the TV channel band could wreak havoc with stations' signals. "The FCC is playing interference roulette with television sets," says David Donovan, president of the Association for Maximum Service Television (MSTV), a trade group focusing on digital TV and other technology issues.
By summer 2005, the FCC plans to issue rules permitting unlicensed use of vacant TV channels for connecting to high-speed networks, transmitting e-mails and linking up home offices. Although forbidden in the TV band, unlicensed consumer products are common in other portions of the communications spectrum. Examples include garage-door openers, TV remote controls and cordless phones.
Unlike licensed services such as TV, radio and satellite transmissions, for which permits are issued to a single user for a specific purpose, unlicensed devices can be sold or used for a wide range of uses without prior approval from the FCC. The main condition: Unlicensed devices may not interfere with licensed services.
Despite a promise from FCC staff not to allow interference with TV, Donovan warns, the fine print of the FCC's proposal poses some threats. For instance, computers connected to a Wi-Fi network would be allowed to interfere with TVs within a radius of 10 meters. That means an apartment dweller surfing the Web could knock out the TV signal for residents on the floor below.
Also, the Wi-Fi networks the agency envisions would not work effectively unless they operate at power levels high enough to conflict with TV transmissions. "It's easy to say this will work on paper," Donovan says, "but in the real world, it's a very different situation."
The threat of interference is particularly worrisome because of the switch to digital transmission, he explains. Traditional analog transmissions are reasonably tolerant of interference and often absorb signal conflicts with little more than some snow or ghosting on the viewers' screens. Digital pictures, however, can be completely obliterated by even a small amount of interference.
To mitigate broadcasters' worries somewhat, FCC Chairman Powell has pledged not to let unlicensed users have access to TV channels in crowded markets until 2006. By then, the government should know exactly how much room is available.
To keep a flurry of new products from wreaking havoc on TV signals, Donovan wants to delay the new rules until extensive lab and field tests prove that stations won't be hurt.
To broadcasters accustomed to operating with three or more vacant frequencies between channels, sharing prime spectrum with unlicensed consumer products is akin to building a strip mall along a stretch of prime country real estate.
But at a time when demand for communications services is burgeoning, channels can no longer lie fallow, says Alan Stillwell, associate chief of the FCC's office of engineering and technology. "That spectrum is going to be used one way or another," he told MSTV's Washington conference last week.
Broadcasters are not the only ones wary of the plan. Cellphone provider Qualcomm, which paid $38 million for licenses auctioned by the FCC last summer, says competitors would gain an unfair advantage if they obtained access to free unlicensed spectrum.
Qualcomm lobbyist Dean Brenner also predicts that, if potential buyers have free access to unlicensed frequencies, the government will have difficulty raising the tens of billions of dollars it expects when TV stations' old analog channels are auctioned. "Why are they giving away beachfront spectrum?"
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