【作者】 何建平；

【导师】 孙优贤； 陈积明；

【作者基本信息】 浙江大学 ， 控制科学与工程， 2013， 博士

【摘要】 近年来,随着传感器技术、计算技术、通信技术和微电子技术等方面的飞速发展,无线传感器网络已经在越来越多的领域得到广泛应用,如环境监测、电子医疗、农牧业应用、物联网和智能电网等,并已经渗透到人们生活的方方面面,极大地改善了人们工作和生活方式,因此受到学术界和工业界的高度关注并进行了大量的科学研究。时钟同步作为无线传感器网络中的基本问题之一,是无线传感器网络众多应用的基础前提,因此一直是研究者重点研究的对象。最近,基于一致性的时钟同步算法研究得到了广泛的关注并成为时钟同步问题的研究热点之一。基于一致性的时钟同步算法不但克服了传统时钟同步算法鲁棒性和可扩展性差的缺点,而且具有完全分布式运行、同步精度高和同时补偿时钟斜率和偏差等优点,极大的提高了算法的可应用性。然而,现有的基于一致性的时钟同步研究存在两方面的不足,ⅰ)算法的收敛速度慢,实现时钟同步的能耗较大；ⅱ)时钟同步安全性欠缺,受到网络攻击时无法保障时钟同步。本文结合国际上最新研究成果,考虑有限时间收敛的一致性时钟同步和时钟同步安全问题,提出相应的时钟同步算法并给出了相应的理论分析。本文的主要工作有如下几个方面：1.概述了无线传感器网络发展和时钟同步及其安全问题的相关研究进展。2.针对静态传感器网络中的时钟同步问题,提出了基于最大一致性的时钟同步算法MTS。利用Lyapunove稳定性理论证明了MTS的有限时间收敛性,并给出了收敛时间的上界。为了解决MTS在随机延时下的不稳性,提出了加权最大一致性时钟同步算法WMTS,并从理论上证明了WMTS的有限时间期望收敛性。3.针对随机移动传感器网络中时钟同步问题,结合MTS和邻居探测算法提出了一种优化的基于最大一致性时钟同步算法RMTS,并从理论上证明了RMTS依概率为1的收敛性。利用关系图对随机移动网络进行建模,给出了RMTS的有限时间收敛的下界,并设计了相应的下界计算算法。此外,从理论上证明了增强网络连通性能提升算法的收敛速度,并给出新节点加入提高算法收敛速度的充要条件。4.针对信息操控攻击下基于最大一致性的时钟同步安全问题,设计了硬件时钟和逻辑时钟防御机制,提出了安全的最大一致性时钟同步算法SMTS,并证明了SMTS的有限时间收敛性。SMTS限制了攻击节点的攻击方式和攻击次数,并能在受到攻击时快速实现再次同步,从而确保了时钟同步安全。5.针对信息操控攻击下基于平均一致性的时钟同步安全问题,设计了硬件时钟和逻辑时钟时钟防御机制,提出了一种安全的平均一致性时钟同步算法SATSo基于Lyapunov稳定性理论,证明了SATS与传统的ATS算法具有相同数量级的指数收敛速度。此外,较之其它安全算法,SATS无需隔离攻击节点,而且可以灵活地利用攻击信息来提升收敛速度。6.对最大一致性时钟同步算法MTS的平均一致性时钟同步算法ATS进行实验实现和评估。基于大量实验结果,并结合相应的仿真结果,分析比较了MTS和ATS的收敛速度、同步精度和鲁棒性。结果验证了MTS具有更快的收敛速度和更高的同步精度,说明了一致性算法的实际应用性。最后对全文进行了总结,并展望了进一步的研究工作。更多还原

【Abstract】 With rapid advancement in sensors, computing, communications and MEMS technologies, wireless sensor networks (WSNs) are widely applied in a large range of fields such as environment surveillance, E-health care, architecture and smart grid, etc. WSNs are penetrating into our daily lives, changing the way we work and live. Attracted by their tremendous potential and bright blueprint, many researchers from the academic and industry communities devote huge effort and money to in-depth investigation of WSNs.As one of the fundamental problems in WSNs, time synchronization has been a hot and chal-lenging research topic as well as the basis of many applications of WSNs. Recently, consensus-based time synchronization protocols have attracted widespread concern and have been one of the hottest issues. Such protocols can not only overcome the lack of robustness and less scalability of traditional time synchronization protocols, but also can operate with distributed manner and high synchronization accuracy and compensate both clock skew and offset, which makes the al-gorithm more practical. Unfortunately, there are two problems in the existing research works in terms with consensus-based time synchronization protocols. One aspect is the slow convergence speed as well as the high energy consumption of achieving time synchronization; the other is the lack of security guarantee for time synchronization, which makes the time synchronization under attack uncertain. In order to solve these problems, in this article, we consider the consensus-based time synchronization with finite time convergence and the security problem for time synchroniza-tion based on the state-of-the-art research findings, propose corresponding protocols and provide theoretical analysis. The main work and contributions are summarized as follows.1. A brief literature review on the development of WSNs, time synchronization and secure time synchronization problem related works is provided.2. For the time synchronization problem in static WSNs, a maximum time synchronization (MTS) protocol is proposed based on maximum consensus. We prove the finite convergence of MTS based on the satiability theory of Lyapunov, and give an upper bound of the finite time convergence. To overcome the random communication delay, a weighted maximum time synchronization (WMTS) protocol is provided, which is proved with finite time conver-gence in expected.3. For the time synchronization problem in random mobile sensor networks, by combining maximum consensus and neighbor discover protocol, we propose a revised maximum time synchronization (RMTS) protocol, and prove that the protocol will converge with probabil-ity1. Based on the modeling of random mobile network with relation graph, we give the lower bound of the probability of the finite time convergence for RMTS, and also design the related computing protocol. Furthermore, we prove that strengthening the connectivity of network can improve the convergence speed of algorithm, and provide a necessary and sufficient condition to improve the convergence speed of algorithm when new nodes join in the network.4. For the security problem of consensus-based time synchronization under message manipu-lation attack in WSNs, we design hardware clock and logical clock safeguard mechanisms for MTS to obtain a secure maximum time synchronization (SMTS) protocol, and prove the finite time convergence of SMTS. SMTS is able to limit the attack manners and the number of attacks of attack nodes, and achieve synchronization again after being attacked, which guarantees the time synchronization security.5. For the security problem of average time synchronization under message manipulation attack in WSNs, we design hardware clock and logical clock checking process for ATS to obtain a secure average time synchronization (SATS) protocol. Based on the satiability theory of Lyapunov, we prove that SATS has exponentially convergence rate, which is the same as traditional ATS. Moveover, compared with other algorithms, attack nodes are not necessary to be isolated in SATS and such algorithm can utilize the attack information to accelerate its convergence speed.6. A real sensor network testbed consisted of Micaz nodes has been established, on which various experiments and evaluations for both of the Maximum consensus-based time syn-chronization algorithm (MTS) and Average consensus-based time synchronization algorithm (ATS) have been conducted. Based on substantial results of large amounts of experiments and previously-done simulations, we give the analysis and comparison of MTS and ATS re-garding convergence rate, synchronization accuracy and robustness. The results show that MTS has faster convergence rate and better synchronization accuracy than ATS, which also illustrates the practical feasibility of such consensus algorithm.In the end, the thesis is concluded and some future research works are discussed.更多还原