两种异构CSMA／CA机制OSTS／BSTS无线传感网络公平性、实时性分析比较

摘要

Analyses of IEEE 802.15.4 Carrier Sense Multiple Access with Collision Avoidance （CSMA/CA） scheme have received considerable attention recently. In this paper, we propose two new CSMA/CA schemes OSTS/BSTS to analyze and improve the performance of CSMA/CA scheme with heterogeneous buffered traffic. We adopt two modified semi-Markov chains with one macro-Markov chain and the theory of queues to derive throughput, transmission probability and delay of unsaturated, unacknowledged 802.15A beacon enabled networks, 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. Nodes of OSTS/BSTS schemes are bestowed over the fair opportunity to access the channel, without any priority. Comprehensive analyses and comparisons between these two schemes are proposed in the paper, and the simulation results are consistent with the predictions of these models.%IEEE802．15．4作为一种专为低速率无线个人区域网络（WPAN）而设计的低成本、低功耗、低速率的短距离无线通信新标准，为无线传感器网络提供了一种很好的解决方案。本文针对异构、非饱和无线网络，提出了两种新的CS—MA／CA机制：OSTS／BSTS机制；异构节点数据到达率不同，其各自获取的吞吐量不同，由此分析获得异构网络节点的公平性。OSTS／BSTS机制最大的特点是异构节点被赋予了公平的机会来访问信道，不存在优先权等级的问题。这两种机制采用两个半马尔可夫链模型来分别表达两组节点的访问过程．一个宏观马尔可夫链模型来表达信道状态转换过程．结合队列理论模型来分析异构节点的延时量、吞吐量、传输概率等特性，以获取网络实时性、公平性理论模型，并采用NS-2仿真工具对分析结果进行了仿真。