Wireless LANs and 'neighborhood capture'

A new capture effect, ‘neighborhood capture’, is described, which arises when Ethernet-type protocols are employed in multiple-cell wireless local area networks (WLANs) that re-use RF channels. Given the small number of channels available, co-channel cells cannot all transmit simultaneously without causing interference on one another. A carrier-sense contention-based MAC protocol can allocate channel bandwidth among co-channel cells dynamically and in a distributed manner, but if used without precautions, it may lead to channel capture; mutually non-interfering cochannel neighbours could deprive other co-channel neighbours of access. In general, there will be instability, with the channel retained by a group of cells for long time intervals. This would cause delays, with negative impact on QoS. This paper describes the problem and presents a remedy.