一种改进WLAN的PCF轮询系统数学建模及分析

Modeling and Analyzing for an Improved PCF Polling System of WLAN

针对WLAN中PCF（PointCoordinationFunction）~RR（RoundRobill）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。

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 Mark0v 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.