The Research Of Access Mechanism In IEEE 802.11 DCF

The access protocol of Medium Access Control sublayer is a main factor that affects the performance of IEEE 802.11 wireless local networks, so studying MAC mechanisms of wireless local networks is the important task in the field of wireless local networks.First, this paper mainly expounds the contents and working principles of DCF, analyzes a kind of cooperative MAC strategy based on the basic network architecture. A collision resolution algorithm is improved in order to improve unfair phenomenon in a short scale of time area and the waste of network resource under the traditional 802.11 DCF which adopt binary exponential backoff algorithm. When collision happened among several stations, it keeps other stations that have not encounter collision waiting and transports. All the groups adopt tree splitting algorithm. Theoretic analysis and Simulation results show that the improved collision resolution algorithm improves the performance of system, the backoff slots to access are reduced and the throughput in each station is more balance.Then, when the network is saturated, as more and more packets enter the network, it will inevitably lead to more collisions and network latency. So this paper introduces the rate adaptive mechanism to improve the handshake protocol so that the entire network to achieve an optimal throughput. The algorithm send feedback information to the source stations by the destination stations or cooperative ones, it speed up or slow down the rate of source stations by an adaptive rate controller. Simulation results show that the mechanism can improve further the system throughput although reduce certain stations'.