When you change channels on your TV set, you probably don't notice the "white spaces" between them. That's because they're not officially there - at least for TV broadcasts.
But in a few years, they might be another path from your home to the Internet - one that's potentially faster and cheaper than the broadband your cable or phone company provides today.
In fact, the only stumbling blocks between you and this cheap, high-speed wireless service are the cable, telephone, wireless and broadcast industries - all of whom have good reasons to oppose it. And one other minor item - somebody has to prove that white space wireless transmission actually works.
You haven't heard about this so far because the discussion has taken place among the same group of corporate geeks, bureaucrats and politicians who quietly hatched the scheme to switch the country from analog to digital broadcasting next February. But I predict that white space wireless will bubble its way into the public consciousness the way today's short-range Wi-Fi did at the turn of the century.
What's it all about? Well, white space is the industry's term for the unused portion of the radio spectrum between current analog TV channels. When our traditional broadcast system was established (a process that concluded with UHF in the 1960s), the government left unused frequencies between the channels to keep broadcasters from interfering with one another.
That was smart then, and for decades there was no reason to tinker with the system, even after broadcast equipment and TV tuners improved to the point where the precautions weren't strictly necessary.
Today, however, the broadcast world has been turned upside down by the switch from analog to digital transmission. I've written a lot about this: The most obvious impact is on TVs that receive signals over-the-air with an antenna instead of by cable, satellite or fiber. These sets won't be able to get digital broadcasts without a converter box.
The flip side of the conversion is that the government will take back the so-called 700 megahertz spectrum, which you and I know as UHF channels 52 and up. Like the rest of the TV spectrum, it's prime real estate for broadcasts that have to travel long distances and penetrate walls. That's why Verizon, AT&T; and other wireless outfits recently bid a record $19.6 billion to use various chunks of that spectrum once the switchover happens.
Now don't worry about your favorite UHF station. It won't disappear; it will just move to a different frequency. Your digital TV or converter box will find it the first time you turn it on. And the new system definitely has advantages: Besides allowing high-definition TV signals, it allows each broadcaster to provide additional channels.
With the spectrum auction out of the way, a group of heavyweights known as the Wireless Innovation Alliance is pushing the FCC to allow unlicensed use of white spaces in the TV band after the Feb. 17, 2009, switchover. The group includes Microsoft, Google, Dell, Hewlett-Packard and a variety of computer industry and public interest groups.
They see a future with new Internet service providers who transmit directly from towers into homes and businesses at high speed - over distances much greater than current WI-Fi technology allows. They argue that it will provide more competition and cheaper service, particularly in rural areas under served by cable, DSL and fiber.
This month they trotted out no less a personage than Microsoft founder Bill Gates to make that argument to a Washington trade group.
Although the alliance has serious congressional support, so does the opposition: the National Association of Broadcasters, which is worried about possible interference with its broadcasts.
The broadcast industry may have some reason for concern. Nobody in the industry wants to talk about this yet, but I suspect that that a lot of people with over-the-air TVs won't be able to get some of their current channels after the switchover. It's more likely to be a problem with sets that have rabbit-ear antennas than powered rooftop models, but it's going to be ugly. Any interference at all from white space transmissions could make the problem worse. But this is pure speculation.
A lesser problem: The ubiquitous wireless microphones used by everyone from clergymen to rock stars are licensed to use the same part of the spectrum. So interference could be an issue in those quarters, too.
So the first thing white space backers will have to prove is that it's possible to avoid the kind of interference that worries the broadcasting association. Twice Microsoft has delivered devices to the FCC that can transmit in the white spaces but are designed to sense TV or wireless microphone broadcasts and work around them.
Twice those devices have failed - although from defects that had nothing to do with proving or disproving the concept.
Any long-suffering Windows user would have to ask why the industry would put Microsoft in the lead of an endeavor like this when Intel and Hewlett-Packard are available. But last week Google stepped in to help salvage the attempt.
Google, by the way, was jubilant after using its corporate war chest as a club in the spectrum auction to force a big chunk of the 700 MHz band into "open standards" territory. That will allow customers to use a greater variety of gadgets than phone companies now provide - among them devices running Google's fledgling mobile operating system.
Hoping to expand on that victory, the search-engine giant filed a proposal with the FCC last week pledging its influence and finances to develop a foolproof wireless white space system.
Will this be enough?
It's hard to say at this point. If it's technically possible for carriers to provide fast service this way without stepping on TV broadcasts or wireless mikes - and Microsoft's flubs notwithstanding, it's possible we could see another revolution in Internet access. Stay tuned.