一种基于优先级的DCF退避机制  

A priority-based backoff mechanism for DCF

作　　者：成卫青[1] 齐龙[1] 

机构地区：[1]南京邮电大学计算机学院,江苏南京210023

出　　处：《南京邮电大学学报（自然科学版）》2015年第3期106-112,共7页Journal of Nanjing University of Posts and Telecommunications：Natural Science Edition

基　　金：国家自然科学基金(61170322;71171117;61272084)资助项目

摘　　要：针对当前IEEE 802.11 DCF(分布式协调功能)机制站点无优先级与有些站点需要实时性和高质量服务保证之间的矛盾,提出了一种兼顾优先级、吞吐量、时延的用于DCF的退避机制。该机制将优先级作为退避时隙选择的一个参考因素,将退避窗口分成数个无重叠、连续的子窗口,使不同优先级站点处于同阶退避时有不同的时隙选择范围,从而提升高优先级站点的吞吐量并降低其时延。该机制摒弃了很多复杂概念比IEEE 802.11e简单。采用二维马尔科夫链模型进行数学分析,并用NS2仿真工具加以验证,通过实验证明,采用该机制时,高优先级站点在吞吐量、时延上均能获得良好的服务质量保证。Considering the contradiction that the IEEE802. 11 DCF distributed coordination function （DCF） providing no priority mechanism while some nodes having real-time and high service quality re- quirements, this paper proposes a baekoff mechanism for DCF considering priority, throughput and de- lay. In order to enhance the throughput of high priority nodes and reduce the delay, this mechanism takes the node priority as a reference factor in selecting backoff value. It makes nodes have different priorities with different baekoff windows at the same backoff stage by dividing the backoff window into many non-o- verlapping and continuous sub-windows. It abandons many complicated concepts what makes it more sim- ple compared with IEEE 802.11 e. A Markov chain model is deployed and used to analyze and evaluate the mechanism performance. Besides, the analytical model is validated with NS2 simulation results. The results show that the proposed mechanism can provide better QoS assurance for high priority nodes in terms of the throughput and the delay.

关 键 词：无线局域网 优先级 分布式协调功能 退避机制 QOS 

分 类 号：TP393.1[自动化与计算机技术—计算机应用技术]