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, cochannel cells cannot all transmit simultaneously without causing interference on one another. A carrier-sense contention-based MAC protocol can allocate channel bandwidth among cochannel 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 cochannel neighbours of access. In general, may be instability, with the channel retained by a group of cells for long time intervals. This can cause delays, with negative impact on QoS. The paper describes the problem and presents a remedy.