为进一步改进无线局域网媒体访问控制机制，提高大规模无线局域网的性能，深入研究了IEEE802.11标准的分布式协调功能及两种典型改进方案。与分布式协调功能相比，快速冲突分解机制大幅提高了网络的吞吐量，但网络的时延抖动和公平性却更加恶化；新型自适应DCF机制显著改善了网络的时延抖动和公平性，对网络吞吐量也有所提升。因此，新型自适应DCF机制经进一步完善后，更适用于大规模无线局域网传输多媒体信息。

To improve the media access control mechanism and enhance the performance of largescale wireless LANs, the distributed coordination function of IEEE802.11 standard and two typical improved schemes are studied extensively. Compared with the distributed coordination function, the fast collision resolution mechanism greatly enhances the throughput, but deteriorates the delay jitter and fairness of wireless LANs. The new selfadaptive distributed coordination function markedly improves the delay jitter and fairness performance, while enhancing the throughput of wireless LANs to a certain degree. Hence, with further improvement, the new selfadaptive distributed coordination function is more suitable for largescale wireless LANs for multimedia information transmission.

国家科技部国际科技合作资助项目（2007DFR10420）；重庆市科技攻关项目(CSTC2008AC2075)；重庆市教委科技研究资助项目(KJ080425)