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Analytical models for IEEE 802.11 Distributed Coordination Function (DCF) play important roles in performance estimation, protocol optimization and admission control for wireless networks utilizing this MAC protocol. While a myriad of models for IEEE 802.11 DCF channel access delay and throughput exist, such models' accuracy is generally limited to rather narrow ranges of scenario parameters. Our investigations single out the inaccuracy in modeling the backoff process as the primary reason for the said deviations. In this paper, we introduce two highly accurate models for IEEE 802.11 DCF protocol in a single-hop setting under both saturated and unsaturated traffic loads. First, a crucial augmentation to the classical model proposed by Bianchi is presented for the saturation load analysis to account for channel state during the backoff countdown process, resulting in a highly accurate estimation of collision probability, channel throughput and channel access delay. We then extend this accurate model to unsaturated traffic cases through an iterative approach which similarly results in highly accurate performance metric estimations for a wide range of parameters. Both models have been evaluated through simulations and in comparison with existing analytical models.
Date of Publication: October 2011