一种802.11DCF性能分析的简单方法

为了简化全互连环境饱和情况下IEEE 802.11DCF的性能分析方法，采用了一种简单的盒子－球模型。研究了将活跃结点发送报文时的碰撞转换成对相同数目的球独立随机放入多个盒子问题，盒子数目与活跃节点的平均竞争窗口相关。当有多个球恰巧落入同一个盒子中时，表明相应时刻会有碰撞发生。针对结点重发次数有限的实际情况，将发送结点的状态变化看作一个一维有限状态的马尔可夫过程，提出了一种基于虚发送周期和平均竞争窗口的计算802.11DCF容量的简单方法。仿真结果验证了该方法的合理性。To simplify the performance analysis of IEEE 802.11DCF in a saturated wireless LAN environment, a simple box-ball model is proposed. It regards the problem of packet transmission collisions as throwing some balls into several boxes randomly and independently. Balls are equal to the number of active nodes and boxes are related to the average contention window of each node. When two or more balls happen to fall into the same box, it means a collision would occur when the corresponding time slot arrives. In concern of limited retransmissions for every packet, the state transform of transmitting node is approximated as a finite-state one-dimension Markovian process. A simple method is finally proposed to evaluate the capacity of 802.11DCF based on the concepts of virtual transmission period and average contention window. Simulation results validate the analysis.