In an emergency, cell phone calls can rapidly swamp the network.
When Western New Yorkers tried to call from their snowbound cars during last November's blizzard, many found the airwaves were already jammed.
Now, a University at Buffalo researcher has proposed a wireless technology for bouncing calls from an overloaded transmitter to a nearby tower, connecting calls that would otherwise be blocked.
Chunming Qiao (pronounced CHOW), an associate professor of computer science and engineering, said that the "Ad hoc Relay System" could be produced as a small, low-powered device, allowing cellular companies to deploy them quickly in an emergency.
After meeting a busy signal, the caller's handset "would send out something like an SOS signal, saying 'Is there a relay that can help me?' " Qiao said.
The low-powered relay's coverage area reaches only 400 or 500 meters, one-quarter the area of a cell tower. However, several relays could work together to handle a call, using several hops to reach a tower in an uncongested area, he said.
The work of Qiao and his research group at UB is featured in Business Week's Oct. 29 issue, which appears on newstands this week. The technology could alleviate congestion like that experienced in Manhattan's cell network on Sept. 11, the magazine said.
However, the relay technology wouldn't work with existing cell phones, making it unlikely to be adopted anytime soon.
Existing radio equipment could be adapted to provide the hardware for a relay device, Qiao said. His work has focused on the signaling language necessary for relays to work with existing cell site technology. Finnish cellphone maker Nokia has granted $25,000 a year to support the research.
The idea for a low-power relay got under way in 1999 as a way of filling in cellular dead zones, where terrain blocks transmissions between a cell phone and the nearest tower. The relay should appeal to carriers by allowing their networks to handle more calls with existing transmitters, Qiao said.
But the idea will have to overcome technological and business hurdles before it can bear fruit, said Sudhir Dixit, a senior research manager at Nokia.
To conserve cellular channels, Qiao's relay would use a publicly available radio frequency to bounce calls to a nearby cell tower. "Since those are open bands, there could be interference from other users," Dixit said.
In addition, cellular carriers wouldn't want to bounce calls to the nearest available tower if that meant sending business to their competitors.
The relay technology's first use might be for connecting cell phones to wireless data networks that are springing up in malls and airports, Dixit said.
Instead of relaying calls to a cell tower, Qiao's low-power devices could connect callers into the wireless network's hub, where they would link with land lines. Integrating the popular new wireless networks with the cellular system is a hot research area, he said.
Qiao developed the relay technology with Hongyi Wu, a doctoral candidate in UB's Computer Science and Engineering department, and Ozan Tonguz, former UB professor of electrical engineering, who is now at Carnegie Mellon University.
The technology is described in the October issue of J-SAC, the Journal of Selected Areas in Communications of the Institute of Electrical and Electronics Engineers.