01771nas a2200169   4500000000100000000000100001008004100002260011200043100002400155700002200179700001200201700002000213700002400233245007800257300001400335520125200349       2010                            d  c1bInstitute of Theoretical and Applied Informatics of the Polish Academy of SciencesaGliwice, Bałtycka 51 aTadeusz Czachórski1 aKrzysztof Grochla1 aT. Nycz1 aFerhan Pekergin1 aTadeusz Czachórski00aModeling the IEEE 802.11 Networks MAC Layer Using Diffusion Approximation  a429–4423 aAbstract: The article presents an analytical model of wireless networks using the IEEE 802.11 protocol to access the transport medium. The model allows to determine such key factors of the quality of service as transmission delays and losses. The model is based on diffusion approximation approach which was proposed three decades ago to model wired networks. We show that it can be adapted to take into consideration the input streams with general interarrival time distributions and servers with general service time distributions. The diffusion approximation has been chosen because of fairly general assumptions of models based on it, hard to be represented in Markov models. A queueing network model can have an arbitrary topology, the intensity of transmitted flows can be represented by non-Poisson (even self-similar) streams, the service times at nodes can be defined by general distributions. These assumptions are important: because of the CSMA/CA algorithm, the overall times needed to sent a packet are far from being exponentially distributed and therefore the flows between nodes are non-Poisson. Diffusion approximation allows us also to analyse the of transient behaviour of a network when traffic intensity is changing with time.