Analytical Modelling and Performability Evaluation of Multi-Channel WLANs with Global Failures

Abstract

<pre>Wireless local area networks (<span>WLANs</span>) which are based on IEEE 802.11 standard are used widely in existing local area network configurations. IEEE 802.11 offers multiple non-overlapping channels to increase the capacity of the network. There are strong evidences that <span>WLANs</span> are prone to impairments. In order to improve the quality of service (QoS) and to evaluate the performance of <span>WLANs</span> realistically, the availability of the systems should be considered. This paper studies <span>performability</span> evaluation of a multi-channel <span>WLAN</span> using analytical modelling approach. Unlike the existing studies, the failures of the overall system, where a critical function unit fails making all the channels unavailable are considered. A new term is introduced as global failures. It is possible to solve the models considered using matrix geometric method where system parameters and minimal non negative solution <span>R</span> is computed by an iterative method. However spectral expansion method is a well-known alternative where the iterative calculations for solving <span>R</span> is avoided using eigenvalues and eigenvectors. The exact spectral expansion method is employed to obtain <span>performability</span> measures such as mean queue length and blocking probability. Iterative refinements are employed in solution of simultaneous equations.</pre>