A new architecture for next-generation wireless systems for cellular phones proposed by University at Buffalo researchers could provide an efficient and flexible way to extend outdoor coverage, as well as provide indoor coverage, without building additional cellular phone towers.
It also could make it much easier to complete a call on a cell phone, even when cell phone use is heaviest.
Called iCAR, (integrated Cellular Ad hoc Relay), the new system is said to combine conventional cellular technology with Ad hoc Relay Station (ARS) technology, in which the stations relay or reroute calls from the congested cell to an adjacent one that is not congested.
An ARS is a wireless relaying device that receives a signal from a mobile handset or personal digital assistant and transmits it either to another ARS or to a regular cell tower. Unlike cellular towers, which have a range of a few kilometres, ad-hoc relay stations cover a much smaller area, typically only a few hundred meters.
The new system addresses what its developers say is the inability of the current cellular-phone system to effectively deal with ‘hot spots’ that arise when demand for cellular phone calls in some areas surges, or when traffic becomes unbalanced among different cells.
According to the UB researchers, that situation arises because callers located in one ‘cell’ cannot access resources available in neighbouring cells. ‘The shortcoming of these systems is that even though a neighbouring tower may have channels available for use, if you are physically in a busy cell, you cannot place or receive calls,’ explained Chunming Qiao, Ph.D., UB associate professor of computer science and engineering.
Qiao developed the system with Hongyi Wu, UB doctoral candidate in the Department of Computer Science and Engineering and Ozan Tonguz, Ph.D., UB professor of electrical engineering. ‘The challenge is to find a cost-effective way to dynamically balance the traffic load among the cells,’ said Qiao. ‘With iCAR, this means finding a relay route consisting of Ad-Hoc Relay Stations that will lead from a congested cell to a non-congested cell.’
The new system is reported to have performed well in computer simulations conducted by the UB researchers. Functionally, Qiao explained, the ARS is very similar to a cell tower, but on a much smaller scale.
Cell phone towers have to be tall, he explained, because they need to cover a range of several kilometres. They are usually connected to a wired network using conventional copper or fibre-optic cables, and they must be built according to local zoning regulations with permission from authorities.
On the other hand, Qiao explained, because an ARS can have a far-more-limited range of, say, only several hundred meters, it can be small, perhaps as small as a cell phone, and since it is completely wireless, it also is portable. An ARS could be mounted on top of a vehicle or a building, or even be carried by an individual.
‘Either technology by itself, the cell tower or the relay station, will not scale up cost-effectively,’ he said, ‘which is why integrating the two of them is such a good idea.’
According to Qiao, the iCAR works well because it will automatically find a route, jumping from one ARS to another, until it finds an uncongested cell and it will do so in real time. ‘If a route is available, it shouldn’t take more than a few tens of milliseconds,’ added Qiao.