A Novel Contention Window Control Scheme Based on a Markov Chain Model in Dense WLAN Environment

Abstract

In IEEE 802.11[1] wireless LANs based onCSMA/CA (Carrier Sense Multiple Access with CollisionAvoidance), parameters such as contention window (CW)significantly affects its throughput performance. In this paper,we propose a novel CW control scheme in order to achievethe high throughput performance in dense user environments.While the standard CSMA/CA mechanism employs an adaptiveCW control according to the number of packet retransmissions,the proposed scheme uses the optimum CW size, which is afunction of the number of terminal stations (STAs). In theproposed scheme, an access points (AP) estimates the numberof STAs from the measured packet collision probability, andderives the optimum CW size based on a theoretical analysisusing a Markov chain model. With simulation experimentsin a dense environment, we evaluate the performance of theproposed scheme and show that it significantly improves thethroughput performance.