一种应用于Ad Hoc无线局域网的随机接入协议

本文分析了应用于Ad Hoc无线局域网的BSAC(Buffered Slotted ALOHA CDMA)随机接入协议,并且首次提出了采用Markov(马尔可夫)链方法的分析模型.此模型应用两个Markov链模型,一个表示节点中的M/M/1/k排队模型,另一个表示网络中活动节点数量.两个Markov链模型通过节点空闲概率相互联系.在此模型基础上,本文详细分析了扩频增益、队列长度与最大允许重传次数等输入参数对网络吞吐量、平均延迟与丢包概率等性能尺度的影响,推导得出了BSAC协议的吞吐量极限.另外,本文还引入多数据包接收技术-延迟捕获技术,该项技术可以有效降低数据包冲突概率,相对于没有采用延迟捕获技术的BSAC协议,平均提高吞吐量29.1%,最大吞吐量提高20.8%,使网络性能接近于理论极限.

A Novel Random Access Protocol for Ad Hoc Wireless LANs

The BSAC (buffered S-ALOHA CDMA) protocol that applies to the Ad Hoc Wireless LANs is analyzed,and its analytical model is first proposed by Markovian chain approach in this paper.The analytical model uses two Markovian chains;one is for the M/M/1/k queuing model in the individual node,and another is for the number of the busy nodes in whole networks.Two Markovian chains are connected by the idle probability of queue.The effect which the analytical model's input parameters of throughput,delay and times of failure to deliver has on its performance metric of spreading gain,queue size and maximum allowable number of retransmissions is analyzed.The throughput bound of the B-SAC protocol is given.Besides,the delay-capture technology is introduced to greatly decrease the probability of collision of packets and improve the throughput by averagely 29.1% and improve the maximum throughput by 20.8% compared with the pure BSAC protocol and close to theoretical bound.