PERFORMANCE EVALUATION AND ENHANCEMENT OF IEEE 802.11 MAC PROTOCOL

Abstract

The popularity of mobile devices has increased the need for wireless LANs (WLAN). These Wireless LANs provide high bandwidth to users in a limited geographical area. The key requirements of Medium Access Control (MAC) protocol used in these wireless LANs is the efficient Backoff Mechanism, which guarantees high throughput and less delay. A Backoff Mechanism can work efficiently only when the stations in the WLAN are able to predict the network traffic. This thesis deals with the performance issues of MAC protocol used in IEEE 802.11 wireless LAN. Since there is no way for the stations to predict the network traffic in Basic MAC protocol in 802.11 WLANs (DCF), its Backoff Mechanism does not perform well under full load conditions. Many improvements have been suggested in the literature to improve its performance under full load conditions. In this thesis, we consider two Backoff Mechanisms viz,, DCF Backoff Mechanism and Load Adaptive Backoff Mechanism. We compare the performance of the protocol with DCF Backoff Mechanism and with Load Adaptive Backoff Mechanism through simulation. The results obtained show that protocol with Load Adaptive Backoff Mechanism has significantly increased the performance as compared with DCF Backoff Mechanism. We also propose a modified Load Adaptive Backoff Mechanism, to further improve the performance of Basic IEEE 802.11 MAC protocol. The software is written in C++ and runs under Linux environment iii