Craig Mathias, an analyst with the Farpoint Group, which specializes in the wireless industry, has inspected the Fort Lauderdale network. "It really is just like using a regular cellular system, even though the technology is so different," he says.

The potential for cognitive radio to make better use of spectrum has motivated many companies and academic labs to work on the technology in recent years, says Mathias. "The real advance of xG's system is that it can be deployed in exactly the same way as a conventional cell-phone network," he says. But exactly how xG will bring the technology to market is unclear. "One option may be for a carrier to use this in an area or market where they don't have spectrum, or to serve rural areas without coverage."

Rotondo says that xG wants to offer its approach as a complement to existing networks. "We are interested in having devices able to dynamically access different areas of spectrum--both licensed and unlicensed," he says. Wireless carriers like AT&T are turning to Wi-Fi hot spots to offload some of the load on their licensed spectrum, he points out. Being able to have devices switch to the 900-megahertz band at times of high load could be an attractive option, because it can perform much more like a cell network. The radios developed by xG could be built into commercial phone handsets, says Rotondo.

Alternatively, the system could augment emerging networks that operate in the unlicensed "white spaces" recently freed up by the end of analog TV broadcasts, Rotondo says. A recent study by University of California-Berkeley academics revealed how the density of TV stations in metropolitan areas could reduce the availability of white spaces in such areas.