【摘要】 分布式协调功能(DCF)采用有冲突避免的载波侦听多路访问(CSMA/CA,Carrier Sense Multiple Access with Collision Avoid-ance)方式访问共享无线媒体,是IEEE802.11媒体访问控制协议的基础。然而,在活动节点数目较大的环境下,这种机制容易造成性能恶化,且难以提供实时业务的服务质量(QoS)保证。概述了IEEE802.11的DCF机制及其性能分析方法,重点剖析了当前基于DCF的各种QoS机制,讨论了它们各自的优缺点,最后得出了优化DCF的一些有益的结论。更多还原

【Abstract】 The Distributed Coordination Function(DCF) mechanism is based on Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA),and is the basis of the IEEE802.11 Medium Access Control (MAC) protocol.However,DCF cannot support QoS (Quality of Service) for real-time traffics since the backoff scheme may cause performance deterioration,especially under the environment with large number of active nodes.In this paper,the DCF mechanism and the method for evaluating DCF performances are outlined,and various DCF-based QoS schemes are mainly discussed.From the discussions,some valuable conclusions for optimizing DCF to support QoS are also given.更多还原