A New Markov Model for Non-Saturated 802.11 Networks

In this work, we introduce a new Markov model for the distributed coordination function (DCF) protocol which accurately predicts the network throughput of 802.11 networks under realistic traffic load. Specifically, we provide an improved treatment of the post backoff, the probability of immediate transmission after DIFS, and the probability of having a new packet for transmission after the post backoff. A key feature of our model is the ability to predict the optimal network throughput and the network capacity (in terms of number of stations with acceptable QoS). Knowledge of the network capacity aids to network planning and QoS for multimedia applications. Another feature is that the model converges to a saturated model when the number of stations becomes large. Based on this feature, we introduce a new method to estimate the lower bound of network capacity.