A Dynamic Medium Access Control Algorithm for IEEE 802.11 Wireless Local Area Networks

Abstract-The Distributed Coordination Function (DCF) of IEEE 802.11 Medium Access Control (MAC) protocol has been widely employed due to its easy deployment and low cost. The DCF utilizes a Binary Exponential Back-off (BEB) scheme to reduce the collision probability by doubling the contention window ( cw) upon a packet collision. In this paper, we propose a new back-off algorithm to enhance the performance of DCF in IEEE 802.11 WLANs, which is based on the idea of using a threshold of the collision rate to switch between two different pairs of minimal/maximal contention windows ( mincw, maxcw). This dynamic algorithm can be easily integrated into the traditional DCF protocol. The performance of the improved DCF is investigated and compared with the original DCF using the network simulator NS-2. The performance results reveal that the improved DCF is able to achieve higher throughput and medium utilization as well as lower mean access delay and packet loss probability than the original DCF. I.