Capacity Planning for Voice/Data Traffic in IEEE 802.11e Based Wireless LANs

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. Extensive simulation results are given to illuminate the efficiency of the proposed scheme.