Abstract: Considering that IEEE 802.11 DCF does not support any QoS（Quality of Service） for real-time traffic，this paper proposes an improved diffserv mechanism based on packet retransmission.This mechanism can achieve saturation throughput，saturation delay and frame dropping probability differentiation by differentiating the packet retransmission and the retry limit for different priority traffic.Then，a Markov Chain model is designed to analyze and evaluate the mechanism performance.Mathematical analyses demonstrate that the new mechanism can support QoS in 802.11 DCF effectively，moreover，enhance the saturation throughput significantly.

摘要： 针对IEEE 802.11 DCF不能为实时业务提供服务质量（QoS）保证，提出了一种基于数据包重传的区分服务机制。该机制通过对不同优先级的数据流采用不同的重传机制和重传次数，实现饱和吞吐量、饱和时延和分组丢弃概率的相对区分。然后采用二维Markov Chain模型对该机制进行数学分析与评价。数学分析表明，该机制能够有效支持区分服务，并且能够显著提高系统饱和吞吐量，获得更好的性能。