Abstract: The purpose of this paper is to build a proper mathematical model for IEEE 802.11e EDCA channel access mechanism.This work begins with a thorough investigation of EDCA mechanism.On this basis，a new EDCA analytical model is proposed under saturation condition.The model，using two-dimensional Markov chain，considers the channel busy probability when different access categories back off，as well as the collision probability when different access categories back off to zero，respectively.In addition，the impact of collision probability is analysed on competition of multi-access categories.Furthermore，delay analyses are conducted using the model.The comparison of the analytical results and the simulation results shows that the model can characterize the MAC access delay of the IEEE 802.11e EDCA mechanism very well.

Key words: Enhanced Distributed Channel Access（EDCA） mechanism, Markov model, delay analysis

摘要： 建立了一个合适的IEEE 802.11e EDCA信道接入机制的数学分析模型。首先深入研究了IEEE 802.11e EDCA机制；在此基础上提出了一种新型的饱和状态下EDCA分析模型。该模型采用二维Markov链的分析方法，分别考虑了不同业务在进行退避时，检测到信道忙的概率以及不同业务退避到零，发送数据帧时发生冲突的概率在多业务竞争中产生的影响。进一步地，对该模型进行了延迟分析。数学分析和仿真实验的对比表明，该模型能够很好地描述IEEE 802.11e EDCA信道接入机制的MAC接入延迟。

关键词: 增强型分布信道接入（EDCA）机制, Markov模型, 延迟分析