IEEE802.11标准的分布式协调功能(DCF)模式下,节点通过竞争获得无线媒介的访问权,导致媒介服务时间远大于数据帧传输时间.通过深入分析数据帧传输、数据帧碰撞以及媒介空闲3种媒介状态的转换情况,采用近似二项分布建立媒介状态描述模型,获得了媒介服务时间估计值.仿真结果表明,所建立的模型能够准确地衡量给定网络状态下的媒介服务时间.
For the distributed coordination function (DCF) defined in the IEEE 802. 11 standard, the nodes is obtained an access rights to the wireless medium by contention method. As a result, the service time of the data frame becomes larger than the transmission time. Based on analysis of the transition between the status of frame transmitting, frame collision and idle, the medium status can be described by the binomial distribution; moreover, the service time for the given network status can be estimated. Simulations show that the estimated results are accurate.