A trial cell-phone network in Fort Lauderdale, Florida, gets by without something every other wireless carrier needs: its own chunk of the airwaves. Instead, xG Technology, which made the network, uses base stations and handsets of its own design that steer signals through the unrestricted 900-megahertz band used by cordless phones and other short-range devices.

It's a technique called "cognitive" radio, and it has the potential to make efficient use of an increasingly limited resource: the wireless spectrum. By demonstrating the first cellular network that uses the technique, xG hopes to show that it could help wireless carriers facing growing demand but a relatively fixed supply of spectrum.