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在无线局域网(W LAN)系统中,IEEE 802.11协议在媒介访问控制(M AC)层对各个站点提供公平的信道接入机会。然而由于中心站点的业务量远远大于其他移动站点,M AC层的公平性恶化了传输控制协议(TCP)上、下行业务的公平性。该文以M AC层的观点分析了造成TCP业务不公平性的原因以及现有改进算法中存在的问题。提出了一种利用M AC层突发传输提高中心站点优先级的算法,并采用成批服务M/M/1/B排队模型分析了该算法的性能。仿真结果显示,该算法能够很好地保证TCP上、下行业务流的公平性,大量节省缓冲区容量,而且具有实现简单的优点。
In a wireless LAN (W LAN) system, the IEEE 802.11 protocol provides fair access to channels at various sites at the Medium Access Control (MAC) layer. However, due to the fact that the traffic volume at the central site is much larger than that at other mobile stations, the fairness of the MAC layer deteriorates the fairness of the upstream and downstream services in Transmission Control Protocol (TCP). This paper analyzes the reasons for the unfairness of TCP service and the existing problems in the existing improved algorithms from the viewpoint of MAC layer. This paper proposes an algorithm to improve the priority of the central site using MAC layer burst transmission, and analyzes the performance of the algorithm by using batch service M / M / 1 / B queuing model. The simulation results show that this algorithm can well guarantee the fairness of the upstream and downstream traffic on TCP and save a large amount of buffer capacity, and has the advantages of simple implementation.