一种改进WLAN的PCF轮询系统数学建模和分析.pdf

Scientific Journal of Information Engineering April 2013, Volume 3, Issue 2, PP.27-33 Modeling and Analyzing for an Improved PCF Polling System of WLAN 1 2# 2 Qianlin Liu , Dongfeng Zhao , Yifan Zhao 1. Yunnan Province Military Command Region, Kunming, Yunnan 650051, PR China 2. School of Information, Yunnan University, Kunming, Yunnan 650091, PR China #Email: zhaodf123@263.net Abstract The RR (Round Robin) scheme adopted in PCF (Point Coordination Function) of WLAN seems difficult to guarantee QoS and satisfy the low delay of the sensitive traffic, yet it can hardly differentiate from priority service for the specific polling station. Thus we develop an improved polling model with priority service, multi-level-polling mechanism and mixed service discipline to enhance the RR scheme. With the help of Embedded Markov Chain and Probability Generating Function Method, we set up the mathematical model for the proposed polling system, and make preparations for the closed form expressions of the system parameters. Keywords: WLAN; PCF; Polling System; Modeling and Analyzing 一种改进WLAN 的PCF 轮询系统数学建模及分析* 1 2 2 柳虔林 ，赵东风 ，赵一帆 1. 云南省军区，云南 昆明650051 2. 云南大学信息学院，云南 昆明650091 摘 要：针对WLAN 中PCF (Point Coordination Function)采用RR (Round Robin)轮询控制方式难以对轮询站点进行区分服 务的问题，将优先级服务、多级轮询控制以及混合轮询服务策略有机结合起来，提出一种改进 WLAN 的PCF 轮询控制模 型。采用嵌入式 Markov 链和概率母函数方法，对该系统模型建立起相应的数学模型，为下一步解析系统特性参数奠定理 论基础。 关键词：WLAN ；PCF ；轮询系统；建模与分析 引言 轮询系统基本模型是由一个服务器和 N 个终端组成，服务器依据一定的规则按一个方向依次对每一个 终端进行服务，最后一个终端服务完成后再返回第一个终端，这样便实现