完全服务和门限服务两级轮询系统E（x）特性分析

摘要

Based on priority differentiation and fairness of the system ,this paper proposes a two-class polling system ,namely exhaustive-gated service system ,which uses exhaustive service for ordinary stations and gated service for the central station .The scheme meets the requirements not only for priority differentiation but also fairness .The mathematical model of the new system is set up by method of imbedded Markov chain theory and generating function ,then the E(x) performance characteristics including mean queue length and polling cycle time are accurately analyzed .Theoretical and simulation results are identical and show that the new system efficiently differentiates priorities by always polling central station at first under better fairness for ordinary station .%本文基于区分业务的优先级和提高系统的公平性，提出了普通站点队列采用完全服务、中心站点采用门限服务策略的完全-门限服务两级轮询系统模型，该模型既能满足区分业务优先级的服务需求，又能兼顾系统的公平性。然后，应用嵌入式马尔科夫链和概率母函数建立了系统的数学模型，并精确解析了系统平均排队队长、平均查询周期等 E（x）特性。通过理论计算与仿真实验结果的对比，说明了二者的一致性，新的系统通过始终优先查询中心站点实现了区分优先级的控制，同时普通站点采用完全服务，在服务策略上得到较好的服务，使系统有更好的公平性。