基于改进Markov模型IEEE802.11b性能分析

Performance Analysis of 802.11b Based on Improved Markov Model

IEEE 802.11b理论最高传输速率可达11 Mbit/s,但在实际应用中,发现其IP层数据传输速率远低于此。为了准确评估其数据业务支持能力,对已有基于退避窗口机制的二维Markov模型进行改进,从成帧效率和DCF协议效率两个方面对IEEE 802.11b无线局域网的性能进行了分析,得出饱和条件下系统归一化吞吐率和平均分组时延,并使用NS2进行验证。IEEE 802.11RTS/CTS机制可以改善大数据帧长条件下系统性能,但IEEE 802.11b协议并未给出切换门限建议值。基于上述改进模型,通过理论计算,给出了不同节点数下基本接入模式与RTS/CTS模式切换门限值。

The theoretical maximum data rate of wireless LAN based on IEEE 802.11b is up to 11Mbit/s.However,in practical applications,we find that the actual user data rate is much lower than that.By use of two-dimension Markovian analysis on the framing efficiency and the DCF efficiency,we provide an extensive throughput performance evaluation of the basic access and the RTS/CTS access mechanisms of IEEE 802.11b.The accuracy of the proposed new model is validated by comparing it with simulation results,with respect to saturation throughput.Based on this,this paper gives a compartmentalization of the RTS/CTS threshold,with which the system throughput and average packet delay could be improved.