A Non-linear Dynamic Tuning of the Minimum Contention Window (CWmin) for Enhanced Service Differentiation in IEEE 802.11 ad-hoc Networks

EDCA is a contention-based channel access scheme defined in the 802.11e standard. It is part of the HCCA for infrastructure networks and may be used as a separate coordination function for wireless ad-hoc networks. In this paper, we propose to extend EDCA with a non-linear dynamic adaptation algorithm of the minimum contention window (CWmin) that enables each station to tune the size of the CWmin used in its back-off algorithm at run time. The purpose of our scheme is to reduce delay and jitter and increase the efficiency of the transmission channel. The performance of the IEEE 802.11e EDCA, enhanced with our non-linear adaptation algorithm, is extensively investigated by simulations and compared with other contention window adaptation schemes. Results obtained indicate that our CWmin adaptation scheme outperforms basic EDCA, AEDCF and SD in terms of channel utilization, throughput, and packet delay. Indeed, the delays for high priority and medium priority access categories decrease by respectively up to 63% and up to 96%. In addition, total throughput increases by up to 24%, and channel capacity is at least 30% higher as compared to EDCA