非饱和状态下的IEEE 802.11e性能分析模型

Analytic model for IEEE 802.11e EDCA for unsaturated conditions

为探讨非饱和状态下,基于802.11e的无线局域网中系统参数、用户数量和服务质量之间的关系,提出一种媒体接入(MAC)层性能分析模型。该模型的特点是考虑了增强的分布协调接入机制(EDCA)下各类站点在不同的退避阶段冲突概率不同的差分机制,以及高优先级业务可能在低优先级业务冻结期间传送的概率。该模型通过对MAC层退避过程的分析得到退避时延,将每个站点的数据包发送过程建立成一个排队系统,退避时延为该系统服务时间,并根据对该排队系统的分析得到每类业务包含排队时延和退避时延的总接入时延,以及各类业务的包丢失率。仿真结果和模型分析结果的对比,证明该文提出的分析模型可以准确分析非饱和状态下的802.11e EDCA系统的性能,并得到用户数和服务质量之间的关系。

A media access control （MAC） layer analytical model was developed to analyze the performance of 802. lie-based unsaturated WLAN （wireless local area network）. The algorithm relates each user＇s Quality of Service （QoS） parameters to the number of users and the system parameters. The model considers the enhanced distributed channel access （EDCA） mechanism for differential users, assumes different collision possibilities in different backoff periods, and considers the probability that high priority stations may transmit during the frozen periods of low priority stations. The model analyzes the MAC layer backoff process to calculate the backoff delay and then set up the packet transmission process as a queuing system in which the service time is the sum of the backoff delays. The queuing system analysis includes the whole access delay including the queuing delay, backoff delay, and packet loss rate. Simulations validate the accuracy of the model for unsaturated conditions.