(Performance Analysis of Wireless Local Area Networks (WLANs

Abstract

Attention is increasingly being directed to computer networks with mobility, such as wireless local area networks (WLANs). This is being motivated by the growing number of Notebook personal computers, as well as the need for fast installation and re­ installation of local area networks in several applications (e.g. construction firms, retail activities, hospitals,... etc.).

This thesis addresses the subject of WLAN and presents an overview of its current technology and the standards that have been proposed for its implementation (namely, IEEE 802.11 and HYPERLAN of ETSI). The thesis also analyzes the performance of a WLAN, which is based on the CSMA/CA access control method, using a closed queuing model approach. The solution utilizes a technique called Single Station Superposition (SSS) technique, which provides a set of four interrelated equations for the throughput, delay, probability of collision, and probability of having a busy medium. Numerical results are obtained using the Minerr() function of the MathCad package. The use of this technique allowed for analyzing CSMAICA protocol including the effect of the important back-off algorithm. This feature was neglected in the analytical work for CSMA/CA found in the literature review. It was only considered in simulation work. This is because it complicates the analytical model and makes it mathematically •intractable using classical techniques. Moreover, even in the simulation work on the subject no studies were made on the effect of changing back-off parameters on the system performance. It was found from our results that back-off parameters, such as maximum number of retrials on a collided packet, affect the system performance and may result in degradation of performance if not chosen correctly.