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Бородин Александр
Petrozavodsk State University,Computer Science Department, aborod@cs.karelia.ru

Semi-Markov Model of the 802.11 Distributed Coordination Function

Recent investigations have shown that the performance of a Wi-Fi segment significantly depends on its workload and decreases very fast with the growth of the competing stations number. This misbehavior is mainly connected with the distributed coordination function (DCF), which is the 802.11 contention resolution method. Several improvements of DCF have been proposed by researchers but the most of them are based on simulations rather than on analytical models.

In our work we present the semi-Markov model of the contention process of a wireless station. We revise the previous investigations results of the generic DCF algorithm and its enhancements EIED, SD, PDCF and others from our model point of view. The comparison of the normalized throughput and average delay estimations was carried out for the DCF and its modifications. The theoretical results are illustrated by numerical examples.