A Sustained QoS Solution by Contention Adaptation in IEEE 802.11e Wireless LANs

The most significant issue in 802.11 contention based networks is to prevent collisions and to ensure connection quality. Researchers have shown an increased interest in collision aware back-off algorithms. However, collision aware back-off algorithms are still failed to ensure strict priority for the high priority traffic. Especially in the heavy loading network, a large number of unsuccessful collisions of low priority traffic are the leading cause of the performance degradation of high priority traffic. Our scheme aims to share the transmission channel efficiently and to provide the strict priority contention scheme. Our approach is derived from the Enhanced Distributed Channel Access (EDCA) induced in the IEEE 802.11e standard. Relative priorities adjust the average size of the CW of each traffic class according to both applications requirements and network conditions. We demonstrate the effectiveness of our solution by comparing with existing approaches through extensive simulations. Results show that our scheme improves the throughput of higher priority traffic as well when traffic load is heavy. Furthermore, our scheme is simple and easy to implement. Key-Words: 802.11e, Back-off, EDCF, Contention Window, Collision, QoS