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WiFi Eyes the Empty Airwaves

Date:2011-08-13  [ Print ]  Hits:
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Ever since the government licensed the first radio stations, we've been accustomed to thinking of the airwaves as a scarce resource. Once handed out to the politically well-connected, in more recent years it has been auctioned off to services such as wireless phones for many billions of dollars.   

Look at a chart of how the airwaves are divided, and you'll see sections devoted to radio, TV, cell phones, police radios, and other devices, each of which has its own band of frequencies. Policymakers have talked about allocating those frequencies more efficiently. Reducing the space given over to TV by moving to digital broadcasts has been one key aim.

Now Michael Calabrese, a vice-president at the New America Foundation, a liberal Washington think tank, has advanced a new plan to use some of the wireless spectrum. It qualifies as one of the most promising and innovative ideas in communications. The idea: to open up "white space"—unused frequencies between TV channels—for unlicensed use to anybody who wants to put up a transmitter.

OPEN SPECTRUM. "Unlicensed" spectrum is something we already know about. It's the principle behind WiFi, the networking technology employed to provide the wireless Internet connections you're probably using with your laptop: hotspots at Starbucks, in-home wireless networks, and in the citywide wireless clouds now in the planning stages in Philadelphia and San Francisco.

Anybody who wants to put up a WiFi network can—it uses spectrum that regulators two decades ago decided to leave open instead of parceling it out as they did with the channels used for radio or TV (before WiFi came into its own, most of the uses to which that spectrum was put remained very specialized).

The problem with WiFi is that the signal doesn't travel very far or penetrate walls well. That's something opponents of big citywide WiFi networks have been eager to mention. They have a point, and it's part of the reason WiFi isn't yet an adequate alternative to wired broadband services like cable or DSL.

"BEACHFRONT." One way of getting around the problem might be to make the signal stronger with more powerful transmitters. But that's not an option because WiFi has to operate on very low power to avoid interfering with other WiFi networks or devices such as cordless phones. Another option is to use a different frequency. Lower frequency signals travel further and go through obstacles more easily.

But there isn't very much desirable low frequency spectrum—Calabrese calls it "beachfront" spectrum—up for grabs. And that's where "white space" comes in. TV stations use powerful transmitters to send their signals out for many miles. But the stations can't operate at frequencies too close to each other or the signals would bleed together. That's why not every channel number can be used (in New York City, for instance, stations operate on channels 2, 4, 5, 7, and 9, and some of the channels in between are left empty).

The insight of the proposal advanced by Calabrese and his colleagues is that lower power services can be slotted into those unused spaces and still leave enough of a buffer zone to avoid interfering with TV signals. Calabrese calls unlicensed spectrum between today's TV channels "rocket fuel for broadband networking."

CHEAP SPACE. When he first proposed it in 2001, Calabrese says it seemed like a quixotic plan. That's no longer so. The Federal Communications Commission is interested enough in the proposal that it has gone to the stage of soliciting public comments. And technology companies are very much behind it.

Intel's technical studies show unlicensed networks in the white space between TV channels could allow better signals than current WiFi and still, because they would require fewer transmitters, cut the cost of building extensive wireless networks like those planned by many municipalities to a quarter of what they would cost now. Calabrese's plan demands very little in the way of new technology. Effectively, it operates just like today's WiFi, but in a different part of the airwaves.

Broadcasters have opposed the new plan, waging what Calabrese calls a "scorched earth" campaign against it. They claim their main concern is interference with TV signals. But regulators have been trying to pry some of their spectrum away from broadcasters for years, and there might be a lot more at work than just concerns about interference. In earlier decades, having a broadcast license meant having a right to deliver one kind of service—radio or TV, for instance.

THREAT TO INVESTMENT. But now lots of n

ew data services can use just about any frequency. Letting new services into the space between TV channels reduces broadcasters' hopes that eventually they would just get to keep their big swaths of spectrum and might be allowed use them to offer new services without having to spend billions to buy spectrum at auction (as the phone companies had to do to offer cell phone services).

The big telcos aren't thrilled about the idea either. More powerful services in unlicensed spectrum would pose a threat to the big investments they have made in 3G data services for which they charge $60 to $80 a month. And it could present a more powerful competitive threat to cable and DSL lines than the current crop of municipal wireless plans.

So far, the telcos have been sitting out most of the debate, but there are hints that they'll act if opening the TV band white space gets closer to reality. One handout that Verizon (VZ ) distributed on Capitol Hill—provided to BusinessWeek by Calabrese—argues that there's already plenty of spectrum available for unlicensed uses. The problem is that most of that spectrum is at very high frequencies and has only limited usefulness.

MORE TO AUCTION? Another objection to allowing unlicensed uses of the white space: Selling spectrum licenses has in fact been a very good public policy idea. It has raised billions of dollars for the government and let the market have a voice in deciding what services will be offered.

A recent paper by a researcher at the Progress and Freedom Foundation, a libertarian-leaning think tank that has often sided with the big telcos, argues that if the white space is to be opened up, it can simply be auctioned off. That would certainly be better than nothing. But the incredibly rapid growth of WiFi over the past years proves auctioning spectrum off to the highest bidder isn't the only way to make the most of the airwaves.

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