Study of QoS Management In IEEE 802.11 and 802.11e MAC Layer Protocols

Wireless networks have become increasingly popular in recent times and it has become a pressing need to ensure that the various applications using it get the necessary Quality of service. Wireless networks being inherently different from wired networks and pose a unique set of challenges . Quality of Service(QoS) is dened as the performance oered by a network to its users in terms of providing resource assurance and service dierentiation to dierent kinds of trac ows .Due to scarcity of bandwidth and high rate of packet loss in wireless networks providing QoS to time critical applications is a challeng- ing task .In this thesis we attempt to study the QoS management strategies applied by the wireless networks at the MAC layer .The most common QoS provisioning strategy is to prioritize the dierent classes of trac and make sure that the high priority trac gets preferential access to the channel .In this thesis ,a study of the binary exponential back-o algorithm which is used by the wireless MAC protocols has been done and an improvement has been proposed in which the Contention Window(CW) is varied in a non-uniform manner for dierent access categories with an aim to improve the performance parameters. The CW denes the range[0,CW] from which a random no of slots are chosen by a station in case of a failure in transmission for backing o before attempt- ing to transmit again. To demonstrate the eect of the modied contention window variation scheme simulations have been carried out using the Qualnet Simulator designed by Scalable Network Technologies, Inc. After implementing the proposed modication a performance comparison has been carried out for parameters such as packet delivery ratio, throughput and jitter