Media access control (MAC) protocols play a vital role in determining the performance of wireless local area networks (WLANs). While a variety of MAC protocols have been proposed recently for wireless LANs, the problem of efficient bandwidth utilization, higher throughput, lower mean delay, and fairness has not been fully solved yet. For example, IEEE 802.11 protocol does not perform well and the bandwidth utilization drops below 50% of the total bandwidth under heavy traffic load conditions. Therefore, in order to address these problems of WLANs under heavy traffic load, this thesis proposes a new scheme named Buffer MAC. We analyze the performance of Buffer MAC by using a number of simulation experiments based on ns-2 network simulator. Results show that the proposed Buffer MAC protocol not only improves bandwidth utilization of WLANs but also improves average packet delay, throughput and fairness performance under heavy traffic load conditions. This thesis also contains an exhaustive and comparative study of the new MAC protocol and the original IEEE 802.11 protocol. Some implementation aspects of Buffer MAC protocol are also discussed.