一種802.11DCF性能分析的簡單方法

為了簡化全互連環(huán)境飽和情況下IEEE 802.11DCF的性能分析方法，采用了一種簡單的盒子－球模型。研究了將活躍結(jié)點(diǎn)發(fā)送報(bào)文時(shí)的碰撞轉(zhuǎn)換成對相同數(shù)目的球獨(dú)立隨機(jī)放入多個(gè)盒子問題，盒子數(shù)目與活躍節(jié)點(diǎn)的平均競爭窗口相關(guān)。當(dāng)有多個(gè)球恰巧落入同一個(gè)盒子中時(shí)，表明相應(yīng)時(shí)刻會有碰撞發(fā)生。針對結(jié)點(diǎn)重發(fā)次數(shù)有限的實(shí)際情況，將發(fā)送結(jié)點(diǎn)的狀態(tài)變化看作一個(gè)一維有限狀態(tài)的馬爾可夫過程，提出了一種基于虛發(fā)送周期和平均競爭窗口的計(jì)算802.11DCF容量的簡單方法。仿真結(jié)果驗(yàn)證了該方法的合理性。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.