Analyzing the Perfomance of Wireless Local Area Networks with an Improved Collision Avoidande Mechanism<br /> DOI: 10.14209/jcis.2004.11

Abstract

In this paper we present and analyze a collision avoidance mechanism to increase the throughput and decrease the delay in wireless local area networks. The analysis considers the IEEE 802. I I Standard parameters employed in the Distributed Coordination Function used in the Ad Hoc mode operation. The mechanism is based on the deferral counter (DC) algorithm proposed in HomePlug Standard. The purpose of the Deferral Counter is to increase the contention window faster than the regular backoff function from IEEE 802. I I to prevent collisions. Different from IEEE 802.11, the mechanism increments the contention window of the deferring stations to minimize collisions. We implement this mechanism in ns-2 simulator in order to compare it with IEEE 802.11. We propose three different functions to use in the Deferral Counter mechanism and evaluate their performances considering network throughput, packet delay, and the percentage of overlapping transmissions. Results show that the proposed mechanism performs better when there is more than four active stations no matter the packet size. Furthermore, we also show that the DC function that achieves the best network throughput depends on the packet size and the number of active nodes.