Guglielmo Marconi’s first radio broadcast was a point-to-point affair, a transmission from England to one person in Nova Scotia. It was the radio equivalent of flying an airline’s passengers across the Atlantic one at a time. Today, we pack radio waves into the air as tightly as economy seats on a 747.

We need to. New radio technologies keep coming along—Wi-Fi, WiMax, Bluetooth, ZigBee, the growing panoply of cellular voice and digital services, broadcast satellite, and more. Each requires unique hardware appropriate to its special way of sending and receiving radio waves. To minimize interference, each is restricted to specific bands of the spectrum and is limited in the way it divides that spectrum into channels and in the encoding and modulation schemes it can use. If we tried to impose this sort of regime on road transportation, we might wind up with a system in which buses, cars, and trucks were each restricted to their own separate roadways.

Some of these rules can be justified by the fact that certain parts of the spectrum work best for certain radio applications. But others are merely the legacies of telecommunications history. Spectrum has long been allocated in a first-come, first-served way, with broadcast radio and television in particular getting the most desirable bands. Even though in much of the world cable and satellite television eclipsed broadcast television many years ago, broadcast’s control of prime spectral real estate will most likely continue for at least the next decade.

If radios could somehow use a portion of the broadcast TV spectrum without causing interference, cellular telephony and other important services would be able to exploit those bands, too. With more room to operate, cellphone calls would be a lot cheaper, as would mobile Internet access, which would get faster as well. Your handset would be able to pull in audio and visual entertainment from all over the globe, and videophoning would finally be a reality.

To manage such feats, cellphone handsets would have to be able to shift their frequency of operation on demand and without packing in lots of extra hardware. Telecommunications engineers have a name for that goal—software-defined radio. And the more visionary among them see it as a stepping-stone to an even more distant ideal. Their goal is a wireless device that is smart enough to analyze the radio environment and decide for itself the best spectral band and protocol to reach whatever base station it needs to communicate with, at the lowest level of power consumption.

The name for such remarkable systems is ”cognitive radios,” and some are already emerging from the laboratory to be field-tested by the U.S. military, which has long sponsored research in the area.

Some analysts say it’s only a matter of time before cognitive radios get into the commercial arena, because the economics are compelling. Indeed, many experts say a typical cellphone a decade or two from now will have cognitive features.

Here’s why: widespread use of cognitive radios could make more efficient use of radio spectrum. Estimates of how much additional traffic the airwaves could hold vary, but by some accounts, less than 14 percent of radio spectrum is truly busy at any given time. That includes big chunks of spectrum that are assigned but that aren’t fully used. Prime among them are the upper ranges of the TV bands: channels 14 to 83, better known as ultrahigh frequency or UHF. In 2004, a study by the International Telecommunication Union, in Geneva, found that ”many TV channels are unused over significant geographical areas” and concluded that ”cognitive radio techniques appear to be a promising approach” for using spectrum more efficiently while avoiding interference with current operations.

It’s no surprise, then, that the possibility of supersmart radios has attracted the attention of governmental regulatory bodies on both sides of the Atlantic. The U.S. Federal Communications Commission (FCC) and its UK counterpart, the Office of Communications (Ofcom), have launched technical reviews of cognitive-radio technologies as a way of better managing the scarce resource that spectrum has become. As we’ll see, however, the two agencies couldn’t be more different in their approaches.

Deciding which portion of the spectrum to use at any given moment is only one aspect of what a cognitive radio could do. Adding audio and video sensors as well as speech- and vision-recognition capabilities, the radio handset could, for example, act as a health aid for the elderly. ”It could detect heart palpitations; if necessary, it could ask the user ’Do you feel okay?’ ” says Joseph Mitola III, a consulting scientist with Mitre Corp., in Bedford, Mass. ”If you stuck a shock-vibration sensor on the cellphone and it detected a clonking as a person fell to the floor, it could dial emergency 911 and ask for help.” Mitola has the distinction of having coined the names for both software radio and cognitive radio.