Performance of Real-Time Traffic in EDCA-BASED IEEE 802.11 b/g WLANS

The IEEE 802.11e draft specification is intended to solve the performance problems of WLANs for real time traffic by extending the original 802.11 medium access control (MAC) protocol and introducing priority access mechanisms in the form of the enhanced distributed channel access mechanism (EDCA) and hybrid coordination channel access (HCCA). The draft standard comes with a lot of configurable parameters for channel access, admission control, etc. but it is not very clear how real time traffic actually performs with respect to capacity and throughput in such WLANs that deploy this upcoming standard. In this report we have provided detailed simulation results on the performance of enterprise-anticipated real time VoIP application and collaborative video conferencing in presence of background traffic in EDCA-based IEEE 802.11 WLANs. We estimate the channel capacity and acceptable load conditions for some important enterprise usage scenarios. Subsequently, admission control limits are experimentally derived for these usage scenarios for voice and video traffic. Our simulations show that admission control greatly helps in maintaining the quality of admitted voice calls and video conferencing sessions that are prioritized as per EDCA mechanisms within acceptable channel load conditions. The use of admission control allows admitted voice calls and video sessions to retain their throughput and delay characteristics while unadmitted traffic (voice/video streams) greatly suffer from poor quality (delays, packet drops, etc.) as the channel load increases