Research On The Distributed Coordination Function Algorithm Of IEEE802.11

With the rapid development of Internet, Wireless Local Area Network has beenwidely studied and applied in recent years. IEEE802.11protocol is the most importantstandard for WLAN, and its MAC layer protocol is an important factor which affectingthe performance of WLAN, therefore, research on the MAC layer protocol is ofpractical significance.In today’s wireless networks, stations using the IEEE802.11standard contend forthe channel using the Distributed Coordination Function, of which the key idea is usingthe backoff scheme to reduce the collision probability. In this thesis, on the basis of keyresearch on DCF, the backoff algorithm of which is improved. And the new backoffalgorithm reduces the probability of collision between stations and increases systemthroughput.In this thesis, the Markov model is established according to the binary exponentialbackoff algorithm, the formula for calculating the saturated throughput of system isderived. Then, the simulation analysis gives conclusion that theory inference result isreliable. The improved algorithms of DCF are summarized in this thesis, and thesimulation of the typical algorithms is carried on, with NS2.Based on above analysis, a new backoff algorithm is proposed to improve theperformance of WLAN. In the new backoff algorithm, a threshold is set to determinethe network congestion, and the backoff mechanism is remodeled to let stations accessthe channel more effectively and fairly. Then the network simulation is carried on withthe NS2simulation software. Simulation result shows that the new algorithm enhancesthe fairness and throughput of the system effectively.