Spectrum and public safety: It's OK to share

Give first responders priority over spectrum during an emergency

For as long as I can remember, there has been a fundamental debate about how best to use the radio spectrum.

Just as a brief review, the electromagnetic spectrum is the carrier for radio and other electromagnetic waves, which include microwaves, visible light, X-rays and most of the other energy that moves through space without the benefit of an otherwise physical connection between the two points. (Note to you physicists out there: I know this is a pretty loose definition, but bear with me.)

As it turns out, only part of the spectrum is useful for mobile communications, especially in urban and otherwise populated locations, and much of that spectrum is allocated less than optimally. The radio spectrum today is scarce and thus a very valuable resource, but it used to be allocated to specific users and applications rather haphazardly. The trend in recent years has been to refarm (that's a technical term for moving spectrum from one application to another) the spectrum via an auction process, thereby enriching the U.S. Treasury, which, as we all know, really needs the money.

In general, I'm against the idea of auctions, and I've covered that topic before. But I think we can all agree that certain government communications -- for the military, law enforcement, public safety, first responder and similar applications -- should have priority in their access to appropriate chunks of radio spectrum. Traditionally, these applications have had their own spectrum, and that philosophy dominates to this day. And it makes sense: When one needs to communicate during an emergency, one had better not get a busy signal.

And so, we have paid special attention to the requirements of public safety since the radio became a practical vehicle for mobile communications more than 70 years ago. As we continue to refarm spectrum, care is being taken to make sure we have sufficient space for public safety needs. Of course, the definition of "adequate" depends upon who is asking. As anyone with a basic knowledge of economics knows, it's always best to have too much of a commodity and worry about the details later. In a real crisis, though, "too much" spectrum for public safety could be an abstract, theoretical concept indeed.

It's important to draw the distinction here that we are only talking about the licensed bands, and not the unlicensed spectrum used by Wi-Fi, cordless phones and similar devices. The unlicensed bands are by definition a free-for-all with no coordination among users, and there is no way to prioritize traffic except within a given operational system. Interestingly, a chunk of spectrum at 4.9 GHz has been allocated for the use of local governments, and this spectrum is often used for Wi-Fi technology, but in licensed bands reserved just for municipal needs.

So, the question is how much additional spectrum -- in the choice bands below 3 GHz that are essential for mobility -- is required for the exclusive use of public safety and related applications. And the answer just might be, not much at all.

I want to put forth a radical idea, to wit: There is no longer any real need for dedicated public safety spectrum in licensed bands. First of all, many public agencies use the same cell phones that we do for their mission-critical needs. This includes push-to-talk, which is moving from analog technology to IP-based implementations on cellular networks. So it really becomes a question of prioritization. Let's give the public safety subscriber units priority in times of emergency on otherwise public voice and data networks. This is easy for the network itself to enforce, and allows all of us access to more spectrum under "normal" conditions.

Apart from the military, dedicating spectrum to a particular user, given the ever-increasing demand for mobile communications services, is no longer a very good idea. Ignoring the politics of spectrum allocations for the moment, making a big chunk of spectrum available to all users and restricting access as needed is a far better strategy, ignoring the politics, of course.

Craig J. Mathias is a principal at Farpoint Group, an advisory firm specializing in wireless networking and mobile computing. He can be reached at craig@farpointgroup.com.

Copyright © 2007 IDG Communications, Inc.

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