Where the Spectrum Goes

In response to my post yesterday on the Google-Verizon agreement, a reader commented in an email message:

“The way I see it, AT&T and Verizon would love to have lots more spectrum space for their wireless networks, for the simple reason that they could handle much more traffic and make a lot more money. But the entities which currently hold the additional spectrum don’t want to give it up, and will fight hard to keep it. If anyone wants to point a finger and identify “bad guys” who threaten to restrict the future growth of mobile in this country, I believe those entities would be an appropriate target.”

It’s mostly wrong to think in terms of bad guys. The biggest bandwidth hog is the U.S. government (and other governments), particularly the military. But it is well nigh impossible for an outsider to assess how much of the spectrum they hold they really need.

At one level, of course, the wireless spectrum will always be limited. We’re basically talking about a swatch of electromagnetic spectrum between around 100 MHz and 3 GHz that is useful for terrestrial wireless data communications. The problem is that we don’t use it very efficiently.

One problem: Radios used to be pretty sloppy about their tuning and tended to drift off frequency. This led regulators to leave lots of guard bands or “white space” around assigned frequencies to avoid interference. The greater precision of radios means the protections could be greatly reduced, but the assignments don;t change. The worst offender is over-the-air television. Most of the channels in any given market go unused to avoid interference with neighboring channels or  stations in nearby markets. More precise radios would allow this white space to be reclaimed for data, and the FCC has a proposal that would do just that. It’s technically somewhat difficult–it requires radios that can ascertain that white space is in fact empty before trying to use it, a requirement complicated by the fact that the vacant channels vary for location to location. And the politics are even more difficult, since the idea is opposed both by current broadcast license holders and by various parties (wireless microphone makers and users being the most prominent) who are, i9n effect, squatting on the white space spectrum.

(The FCC also has a plan to recapture digital spectrum that broadcasters are not using. And some folks, nothing the fact that the overwhelming majority of Americans get their television content from some source other than over-the-air broadcasts, would reclaim the hundreds of megahertz dedicated to TV. It’s not going to happen, and even the FCC’s more modest plan, which would require auctioning the spectrum with the current licensees to share in the proceeds, faces massive opposition from politically powerful broadcasters.)

The ultimate improvement in spectrum utilization would be a new breed of smart radios (sometimes called agile radios or software-defined radios) that could operate on a broad range of frequencies and that could sniff out and use bits of free spectrum wherever it was available. These have been under development for years, but still have not escaped from the labs.

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