基于分组到达率的802.11 DCF性能分析

针对WLAN(wireless local area network)基础结构模式中的IEEE 802.11 DCF(distributed coordination function)机制,提出了一种基于分组到达率的性能分析模型.模型不仅考虑了终端数量、传输负载、二进制指数回退机制等因素,而且分析了MAC(mediunl access control)层有限队列对系统性能的影响.在每个终端被模型化为M/M/1/K队列的基础上,进一步利用虚拟时隙在时间上离散化终端MAC层队列状态,并采用离散时间的三维马尔可夫链对系统性能建模.基于该模型得到了归一化吞吐量、分组时延和丢包率.仿真分析结果表明,该模型能够有效地预测变化的分组到达率情形下DCF机制的性能.

Performance Analysis Based on Packet Arrival Rate for the IEEE 802.11 DCF

A performance analytic model based on packet arrival rate is proposed for IEEE 802.11 DCF (distributed coordination function)in infrastructure-based WLAN(wireless local area network).The model does not only take into account the factors of number of terminals,traffic loads,the binary exponential back-off mechanism, but also analyzes the impact of the finite queue system at the MAC(medium access control)layer.Each terminal is modeled as an M/M/1/K queue,and the virtual time slot is introduced to discretize the state of the queue system. Based on this,a three dimensional discrete time Markov chain is used to model the system.By using the model, normalized throughput,packet delay and packet losing ratio are obtained.Simulation results show that the proposed model can validly predict the performance of the DCF under various packet arrival rates.