The Value of Cooperation

As computers get faster, this gain in capacity (which technologists call "processing gain") grows. Like a better antenna ("antenna gain"), processing gain means we can have more capacity in a particular radio architecture than otherwise would be possible. Technologists are increasingly discussing a related kind of gain called "cooperation gain." Again, think about a party. If I need to tell you that it's time to leave, I could choose to shout that message across the room. Shouting, however, is rude. So instead, imagine I choose to whisper my message to the person standing next to me, and he whispered it to the next person, and she to the next person, and so on. This series of whispers could get my message across the room without forcing me to shout.

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Radios can achieve a similar gain from cooperation. Rather than blasting a message at high power so that you can hear it at the other end of the city, I could instead whisper the message to a receiver near me, and it could whisper the message to the next receiver, and so on. Through their cooperation, these nodes operating in a "mesh" could reduce the power required by any particular transmission. And if the power of any particular transmission is reduced, then the total capacity again would increase.

Radio technology thus tries to find the mix of antenna gain, processing gain and cooperation gain that maximizes total capacity for the system. And as Wi-Fi and meshed wireless networks are increasingly demonstrating, that increase in capacity can be realized without any centralized controller deciding who gets to say what when, or without allocating exclusive rights to "spectrum." Instead, with the proper protocols and an etiquette between different protocols, radios can simply "share" spectrum without central coordination.

But won't such "sharing" lead to congestion? Won't this "commons" lead to a "tragedy of the commons"? The answer, surprisingly, is "not necessarily." No doubt a bad architecture will quickly bust. But many believe that there are good architectures for spectrum sharing that would have the property of increasing spectrum capacity as the number of users increase. It's too early to know whether such systems will scale, but it's not too early to see that their ability to exist depends upon lots of spectrum remaining free for experimentation.

Wi-Fi is the first successful example of these spectrum-sharing technologies. Within thin slices of the spectrum bands, the government has permitted "unlicensed" spectrum use. The 802.11 family of protocols has jumped on these slivers to deliver surprisingly robust data services. These protocols rely on a hobbled version of spread-spectrum technology. Even in this crude implementation, the technology is exploding like wildfire.

And this is just the beginning. If the Federal Communications Commission frees more spectrum to such experimentation, there is no end to wireless technologies' potential. Especially at a time when broadband competition has all but stalled, using the commons of a spectrum to invite new competitors is a strategy that looks increasingly appealing to policy makers.

For more information, see the papers collected at cyberlaw.stanford.edu/spectrum. For a commercial implementation of "meshed" technologies, see www.meshnetworks.com.

Lawrence Lessig is a regular columnist for CIO Insight Magazine, and a professor of law at Stanford University Law School. He is the author of The Future of Ideas: The Fate of the Commons in a Connected World and Code and Other Laws of Cyberspace.

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