Dynamic Contention Window Adaptation (DCWA) in IEEE 802.11e wireless local area networks

The Wireless LAN medium access control (MAC) protocol is responsible for an efficient sharing of the limited communication bandwidth. With the demand for Quality of Service (QoS), which is supported by different traffic classes in 802.11e, this task becomes even more complex. In this paper, we present a dynamic contention window adaptation (DCWA) algorithm which adapts the contention window parameters for a single traffic class such that they are as small as possible to meet realtime conditions and large enough to cope with the current network load. The results reveal that the DCWA increases the overall cell capacity significantly compared to the fixed IEEE standard settings, it adaptively minimizes the contention delay when possible and maximizes the throughput when needed. Furthermore, we extended the method to handle competing high and low priority traffic and showed that the new mechanism can effectively protect voice from best effort traffic.