Performance Analysis And Improvement Mechanism Study Of IEEE 802.11eMAC Protocol

Wireless LANs have infiltrated into our social life in various fields. At present, mobile communication has become the most active and fastest-growing area in communication industry. At the same time, requirement of audio, video, real-time services in mobile communication, is improving, such as Quality of Service. IEEE802.11e protocol provided a reliable transmission protection for multimedia services, with a certain degree of optimization .And it provided effective QoS support for large number of different traffic.When the network load changes in large-scale frequently, the network throughput was not smooth and there was emergence of a serious slump, especially the network load become larger. Therefore, the recommended value was often insufficient to meet the business requirement, with the default value of EDCA (Enhanced Distributed Channel Access) parameters in 802.11e standard. The standard of the EDCA mechanism lacked of a simple and adaptive bandwidth resources management plan, so a reasonable mechanism to automatically adjust EDCA parameters was needed to optimize network performance. The research work was necessary, and its content had important research value and practical significance.The core principle of EDCA mechanism in IEEE802.11eMAC protocol was analyzed in-depth, and the improved 802.11eMAC protocol mechanisms were studied. The research was done in the following aspects.1. The principle of the IEEE 802.11e was introduced and the core thought of the 802.11e EDCA mechanism was analyzed, compared to IEEE802.11 Distributed Coordination Function DCF mechanism.2. A detailed analysis of various parameters impact on network performance in EDCA mechanism was given, and the EDCA mechanism of the virtual collision problem and its solution was studied in-depth.3. An adaptive mechanism, a-EDCA mechanism, is proposed to adjust EDCA parameters, as complement for the 802.11e EDCA mechanism in the dynamic network.The access point (AP) adjusted the size of the EDCA parameters contention window parameter values automatically, according to current network throughput variation in a-EDCA mechanism. 4. The effect of a-EDCA mechanism is verified, with the network load changing frequently under high load condition in network simulation software NS2. The results shows that the adaptive adjustment mechanism achieves a better service for real-time operational purposes, providing timely service for audio and video real-time traffic.And it ensures transmission fairness between high and low priority level traffic.