基于队列理论CSMA/CA机制的无线传感器异构机制OSTS的实时性分析

摘要

自从IEEE 802.15.4标准发布以来,基于低功耗、低速率传输的无线传感器网络的应用几乎涉及到现实生活的方方面面;但是关于这个标准的CSMA/CA机制大部分都是基于均匀、饱和的传感器网络应用。文中针对非饱和、带缓存的无线传感器异构网络,提出了一种新的异构的CSMA/CA机制OSTS。该机制采用2个马尔可夫链来分别表示异构节点访问信道的过程、一个宏观马尔可夫链来表达信道状态转移,且结合M/G/1/K队列理论分析数据包传送的实时性能,并相应地改进系统的实时性。文中最大的特点是两组非均匀节点被赋予了公平的机会访问信道,而不存在优先权的问题。此外,详细分析了这种机制的数据包传送时间,包括数据包到达率、包大小、节点数量、缓存大小等参数对系统实时性的影响;这些分析结果与我们采用NS-2工具仿真的结果十分吻合。%Analyses of IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance（CSMA/CA） mechanism have received considerable attention recently,and most of these analyses focus on homogeneous or saturated traffic.In this paper,we propose a new CSMA/CA scheme OSTS to evaluate and improve the performance of heterogeneous buffered networks which is more realistic in our applications.We adopt two modified semi-Markov chains with one macro-Markov chain and the theory of M/G/1/K queues to evaluate characteristics of our time-critical non-priority network.Packet delay of unsaturated,unacknowledged 802.15.4 beacon enabled networks based on these models are predicted,including the impact of different parameters such as packet arrival rate,packet size,node’s buffer size and the number of different kinds of nodes.Comprehensive simulation results are consistent with the predictions of these models.