【作者】 高海燕；

【导师】 冯秀芳；

【作者基本信息】 太原理工大学 ， 计算机应用技术， 2011， 硕士

【摘要】 近年来,随着信息技术、嵌入式技术以及传感器技术的飞速发展与日益成熟,并且由于小型化、低成本、低功耗技术的迅猛发展,从而推动了分布式、大规模的无线传感器网络的飞速发展。无线传感器网络是新时代新兴的信息收集和处理技术,它主要是由传感器、微处理器以及无线通信接口共同组成的,是一种集数据采集与融合处理以及通信为一体的网络,在多种领域上,如国防军事、医疗卫生、环境监测、家庭护理、灾难拯救和空间探索等等都显示出了广阔的应用前景,现今已经引起了全世界学术界与工业界的高度重视,成为了当前国际备受关注的热点研究领域。与传统的无线网络相比,无线传感器网络有明显不同的研究目标、技术指标和应用要求。时间同步技术作为无线传感器网络应用中的一项重要支撑技术,对于无线传感器网络的研究与应用都具有关键的作用,无线传感器网络的大多数部分都有需要,例如：在传感器的数据融合技术中需要时间同步来识别事件在物理世界当中发生的时间。但无线传感器网络中,在时钟的准确性与精度上比传统网络中的要求高,另外还需要考虑能量要求的限制,而传统的时间同步方法NTP与GPS因其复杂度和能量问题、代价以及尺寸因素等都不适合于传感器网络使用。因此,由于考虑到传感器节点受到诸如成本、能量以及体积等限制,而传统网络中时间同步算法最终已经不能达到无线传感器网络现有的要求。从而使得现有无线传感器网络的同步技术遇到了前所未有的新挑战,以至于研究出适合传感器网络的新的时间同步方法成为国内外现有传感器网络研究领域的关注焦点。此论文就是立足于前人研究的基础上,讨论了现有网络时间同步协议为什么不适用于传感器网络,分析了几种现有传感器网络的时间同步协议的优缺点。并着重分析了RBS时间同步协议所使用的时间同步信息传输的方法与降低时间同步误差的具体原理。然后又进一步对无线传感器网络当中的时间同步技术加以更细致的研究,其中包括了其时间同步算法的必要性、同步技术及其分类、系统的时钟同步模型,以及对各种同步机制做了比较。最后特别对RBS(参考广播同步算法)这种典型的时间同步算法做了优化改进。优化后的算法主要是针对RBS算法中节点时钟相对不稳定,并且节点之间消息交换延迟所导致的同步误差,通过概率论中有关极大似然估计的相关知识来减少时间同步的误差。此算法在多跳网络环境中比RBS算法的同步精度明显提高；本文还就优化后的算法进行了安全性方面的深入研究。归结到最后,从仿真结果我们可以得出,该算法在一定程度上能够提高无线传感器网络的时间同步精度,具有较好的可靠性。更多还原

【Abstract】 In recent years, as information technology, built-in technology and sensor technology developed and maturated rapidly, and the miniature, low cost and low power consuming techniques improved considerably, the distributed large scale wireless sensor network has been developing greatly. Wireless sensor network is a newly emerging information collecting and processing technique. It mainly consists of sensors, microprocessor, and wireless communication interface, and it is a network that integrates data acquisition, fusion processing and communication. It is applied in a variety of areas, such as the defense military, medicine and health, environmental monitoring, family care, disaster rescue and space exploration, etc. It has drawn great attention in field of academic and industry, and become the international focus of research. Compared with the traditional wireless network, wireless sensor networks have obviously different research objective, technical indicators and application requirements.As an important technique in wireless sensor network applications, time synchronization technology plays an essential part in research and application of wireless sensor network, and is needed in most part of wireless sensor networks, for example:in a sensor data fusion technology time synchronization is used to identify the time when events happen in the physical world. However, in wireless sensor networks, accuracy and precision is demanded more strictly than in traditional network. Considering energy requirements restriction, traditional time synchronization method NTP and GPS are not suitable for sensor networks for the matter of complexity, energy issues, price and size. Therefore, considering cost, energy, and volume limitation on network sensors, the time synchronization algorithm for can not meet requirements of wireless sensor network. The existing wireless sensor network synchronization techniques encountered unprecedented challenges, thus research for new time synchronization method suitable for sensor network has become the focus of domestic and foreign research of existing sensor network research.Based on previous studies, this paper discusses why the existing network time synchronization protocol does not apply to sensor network and analyses advantages and disadvantages of several time synchronization protocols for existing sensor networks. It mainly analyses the time-synchronized information transmission method used in RBS time synchronization protocol and the specific principle of how to reduce the time synchronization error. Then it makes further investigation on time synchronization technique of wireless sensor network, including the necessity of its time synchronization algorithm, synchronous technology and its classification, system clock synchronization model, as well as the comparison of various synchronization mechanisms. Finally it optimizes and improves RBS (reference radio synchronous algorithm), a typical time synchronization algorithm. Mainly aiming at the relatively unstableness of node clock, and the synchronization error caused by the delay of message exchanges between nodes, the optimized algorithm synchronization uses theories related to Bayesian estimation to reduce time synchronization error. In the network environment of multiple hops, this algorithm is distinctly more accurate than RBS algorithm. This paper also thoroughly studies the safety of the optimized algorithm. To sum up, from the simulation results we can draw the conclusion that the algorithm improves time synchronization accuracy of wireless sensor network to a certain extent, and it is highly reliable.更多还原