"Network is busy"¿three dreaded words for cellular phone users. But they may appear less often in the near future, thanks to researchers at the University at Buffalo. Chunming Qiao and colleagues have devised a new technology for rerouting calls and thus alleviating traffic jams at wireless network relay towers. On these networks, as on roads and highways, the key problem is not necessarily too much "traffic" but unevenly distributed traffic. "The shortcoming of these systems is that even though a neighboring tower may have channels available for use, if you are physically in a busy cell, you cannot place or receive a call," Qiao explains.

The new technology, called iCAR (integrated Cellular Ad hoc Relay), builds on the existing relay tower technology but improves it with the help of Ad hoc Relay Station (ARS) devices. Unlike a relay tower, which has a range of several kilometers, an ARS can cover only a few hundred meters but is small and mobile, Qiao says. It receives the signal from a cell phone or other wireless device and transmits it to a nearby cell tower or another ARS, diverting traffic from busy cell towers. ICAR finds a route automatically, moving from ARS to ARS until it locates a free cell. "If a route is available, it shouldn't take more than a few tens of milliseconds [to find it]," Qiao estimates. The UB researchers ran computer simulations to test a potential iCAR system and concluded that it should fare well in the real world. "Either technology by itself, the cell tower or the relay station, will not scale up cost-effectively," Qiao says, "which is why integrating the two of them is such a good idea."

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