Adaptive techniques to guarantee QoS in a IEEE 802.11 wireless LAN

The proposed IEEE 802.11e standard aims to add Quality of Service (QoS) to the IEEE 802.11 wireless LAN (WLAN). The 802.11e MAC provides two different channel access schemes: a centrally-controlled one and a contention-based one. In this paper we focus on the contention-based channel access mechanism, called enhanced distributed channel access function (EDCA) [5]. In particular, we propose adaptive techniques to set MAC parameters via link adaptation to optimize QoS. Assuming as simulation model an infrastructure network, we claim that dynamically adapting MAC parameters on the basis of a wireless channel condition evaluation by both the AP and associated stations, could preserve QoS constraints for existing flows. The efficiency of those adaptive techniques is tested via simulation results in NS-2.