Abstract: Distributed coordination function(DCF) is basis access mechanism in the IEEE 802.11 MAC protocol. Research shows that the DCF performs unfairly and anomaly within multi-rate wireless LANs. A new adaptive backoff algorithm based on rate and channel state with fuzzy logic control is proposed. By doing this, an appropriate CW value can be got to reduce the collision and improve the performance of CSMA/CA and RTS/CTS. Simulation results show that the fuzzy logic control method can not only reduce the packet collision, but also enhance the performance and fairness of CSMA/CA and RTS/CTS

Key words: Multi-rate WLANs; DCF; Fuzzy adaptive control; Fairness

摘要： 针对DCF 应用在多速率无线局域网中存在吞吐量异常和严重不公平性问题，提出了一个基于信道状态和节点速率的模糊自适应退避算法——RCFAB 算法。仿真结果表明，RCFAB 能够适应多速率WLAN，并有效地改善系统的吞吐量和接入公平性。

关键词: 多速率无线局域网；分布式协调功能；模糊自适应控制；公平性