Proc. of ICC 2008
In this paper, we concentrate on IEEE 802.11e based WLANs with mixed Voice-over-IP (VoIP) and data services. Although the enhanced distributed coordination access mechanism of IEEE 802.11e can differentiate VoIP and data services, the unsaturated feature of VoIP traffic and the unbalance between downlink and uplink degrade the capacity for VoIP seriously. To address these issue, we propose a queueing system based analytical model to investigate the contention between unsaturated voice traffic and saturated data traffic. Moreover, our queueing analysis indicates that the bottleneck of increasing the capacity for VoIP is the downlink. Based on the capacity analysis, we propose an admission control mechanism to guarantee the Quality-of-Service of admitted VoIP sessions, and also propose a multiple APs solution to enhance the capacity for VoIP. Extensive simulation results are given to illuminate the efficiency of the proposed two schemes.