Ieee802.11mac Protocol And Optimization

Wireless local area network (WLAN), with the advantages of convenient, flexible, low-cost and easy to extend, has been widely used in various occasions, recently. IEEE 802.11, as the most important international standard for WLAN, has a good application prospect and great study space, and attaches more and more attention. However, because of the poor conditions of wireless channel, it is more likely to have packet loss, collisions, and retransmission and so on. As any transmission must rely on shared, open wireless medium, the collision is inecitable. The conflicting data will cost more bandwidth resources and reduce the throughput of the network. In recent wireless network's research, the topic of how to improves and optimizes the throughput of the MAC'protocol become more and more important.The main purpose of this thesis is to optimize the the core mechanism, called DCF (Distributed Coordination Function) mechanism, in MAC'protocol. Through analyzing the MAC'protocol performance model - Markov chain model, we obtain the relationship between the competition window and the network scale in optimal system throughput. As it is difficult to accurately estimate the networks scale in a dynamic wireless network, we use the average collision count to replace the accurate measurement of the number of competition terminals in the previous algorithm, and then we get the relationship between the competition window and the collision count in optimal system throughput. At the same time, for the shortcomings of that the distributed coordination function can not distinguish the conflict, we add"Conflict weights"to the DCF mechanism, and propose the dynamic optimization algorithm based on the conflict Weights.In this thesis, we program the improving algorithm. Then we do comparison tests to the optimization mechanism and the original mechanism, separately in the Independent BSS and the Infrastructure BSS, and get the system throughput, system latency and system stability. From these data, the improved algorithm has obvious advantages. We get the maximum 2 times of the system throughput and lower 80% of the system delay, base on Standard algorithm. In the study of system stability, the improved scheme is more stable in throughput and system latency comparing original mechanism. Through the simulation, we improved that the improving algorithm is effective.