A cross-layer analysis for evaluating the voice conversation performance over wireless LANs

In this article, we present a mathematical model for evaluating the throughput of IEEE 802.11 MAC layer as well as the network-layer performance such as queueing delay or packet loss at each station. Our proposal combines a Markov chain model for evaluating the throughput of the IEEE 802.11 DCF and a queueing model for analyzing the network-layer performance of each station. Through extensive simulations using the simulator ns2, we show that our model can accurately predict how many voice conversations can be multiplexed over a WLAN without loss of any packets. Our model allows us to evaluate the IEEE 802.11 DCF with contention window (CW) differentiation, which is a service differentiation scheme provided by EDCA. In this article, we also investigate how much the CW differentiation could improve the bandwidth utilization by making contention window of the access point smaller than wireless stations.