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类型 基础研究 预答辩日期 2018-04-12
开始(开题)日期 2014-10-22 论文结束日期 2017-10-25
地点 东南大学四牌楼校区中心楼609会议室 论文选题来源 973、863项目     论文字数 4.7 (万字)
题目 无线传感器网络中一致性时钟同步算法性能分析
主题词 时钟同步,一致性,随机时延,统一建模,拓扑结构
摘要 近年来随着微电子技术在自配置、功能强大且成本低廉的微型传感器终端方面的技术突破,无线传感器网络引起广泛关注,并在环境监测、工业质控、军事作战以及智能家居等诸多领域得到迅速发展。无线传感器网络由一些具有感知、存储和计算能力的节点构成,这些节点布控在一定的应用环境中,邻居之间能够互相通讯,彼此协作共同完成特定的任务。绝大部分应用要求网络中的所有节点都在统一时间尺度下处理和交流信息,这样融合和分析不同节点所探测的数据才有意义,因此时钟同步是无线传感器网络中关键的基本技术之一。 传统的时钟同步协议在建立和维持特定拓扑结构方面开销过大,当遭遇拓扑变换和节点故障时,协议鲁棒性和可扩展性都不尽人意。最近受一致性问题收敛性分析的成熟研究启发,学者们设计了众多基于一致性协议的时钟同步算法。本文重点探讨了无线传感器网络为有向通信拓扑且存在随机通讯时延的情形,对一致性协议的时钟同步算法进行统一建模和收敛性分析,并研究了拓扑结构和回路时延对时钟同步稳态性能的影响。文中用到的分析工具主要包括代数图论、矩阵论和一致性理论。论文的主要工作如下: 1.在随机有界时延存在的无线传感器网络中,考察了一致性时钟同步算法统一建模和有界收敛的必要条件。首先为一致性协议时钟同步算法构造一个统一的结构模型,然后通过调节算法参数将各种一致性时钟同步算法(如 ATS 、WMTS 和 LSTS)匹配到此结构模型上。借助相对时钟斜率估计误差的渐近特性,发现了CBTS算法发散条件以及均方发散条件,结果表明 ATS算法几乎必然发散,WMTS算法均方发散,而 LSTS算法则有界收敛。 2.研究了无线传感器网络中LSTS算法下时钟同步稳态误差与拓扑结构的关系。考虑节点之间存在随机有界通信时延的情形,分别考察了基本拓扑、复杂拓扑以及固定和随机切换拓扑模式下LSTS算法时钟同步误差的稳态性能。文中定义了“误差指标”用来描述全局同步误差的统计特性。在存在根节点与路径(或环)的网络结构中,“误差指标”可被精确计算。研究表明节点间路径或环越多,那么全局时钟同步误差会越大。 3.针对随机有界时延给时钟同步算法的设计和分析带来的挑战,讨论了无线传感器网络中LSTS算法时钟同步稳态误差与时延分布的关系。研究表明时钟斜率补偿的误差主要依赖于随机通讯时延的方差而不是期望,时钟同步误差的大小主要由通讯时延的期望决定。分析传感器节点双向通讯情形下回路时延的性质,通过回路时延对时钟相位进行补偿,并引入一致性问题中的衰减因子,二者联合控制可以同时减小时钟同步误差的期望和方差。
英文题目 The performance analysis of consensus-based time synchronization algorithms in wireless sensor networks
英文主题词 time synchronization, consensus, random time delay, algorithm convergence, uniform modeling, topological structure
英文摘要 Recently, wireless senor networks (WSNs) have drawn great interest and have obtained exciting advances in many fields including environment monitoring, industrial quality control, military operation, home automation and so forth due to the development of inexpensive, miniature, self-configuring and powerful sensor terminals in micro-electro-mechanical systems (MEMS) technology. WSNs are comprised of a collection of nodes with sensing, memory and computational capabilities that are deployed within an environment and can communicate with their neighbors to execute mission cooperatively. Most of the applications based on WSNs demand all of the nodes to operate on a common notion of time. The requirement for precision time synchronization has become more and more critical in WSNs as it makes no sense to integrate and interpret information sensed at different nodes without accurate time information. Traditional time synchronization protocols suffer from large overhead in building and maintaining specific structures and show poor robustness and scalability to the topology changes and failures of nodes. Inspired by great advances in convergence analysis tools for consensus problem, design and convergence analysis of consensus-based distributed time synchronization (CBTS) protocols have begun to emerge.This dissertation specially investigates the problem of structural modeling and convergence analysis of consensus-based distributed time synchronization algorithms under the general directed communication topology with random communication delays, and attempts to discover the impacts of the topological structure and round delay on the performance of time synchronization steady state error .The main analysis tools utilized in this dissertation include algebraic graph, matrix theory and consensus theory. The main work of the dissertation is summarized as follows: 1. The divergence conditions of a consensus-based time synchronization algorithm have been studied over a network with random communication delays. A unified structural model of CBTS algorithms is presented firstly. Then different CBTS algorithms such as ATS, WMTS and LSTS, are fitted into the same structural model with just different algorithm parameters respectively. Divergence conditions and mean-square divergence conditions of CBTS algorithms have been discovered by studying the asymptotic property of the relative drift estimation error. It clearly point out that the ATS algorithm is divergent almost surely, the WMTS algorithm is mean-square divergent, but the LSTS overcomes all of these divergence conditions. 2. The relationship is analyzed between the steady state error and the topological structure for a least square estimation bases time synchronization (LSTS) algorithm in wireless sensor networks. Given the presence of random bounded communication delays between nodes, the performance of the steady state error is considered under the basic, complex and determined/random switching topology. The definition of an \emph{error indicator} is proposed to describe the impact on the statistical property of the global synchronization error. The error indicators are computed among several network architectures with the existence of root node and paths (or cycles). It is discovered that the more paths or cycles between nodes (except root node) exist, the larger the global synchronization error appears which is against our intuition. 3. In order to tackle the problem of random communication delays in time synchronization process, the relationship is discussed between the steady state error and the probability distribution of delay for LSTS algorithm in wireless sensor networks. It is shown that the error of clock drift compensation mainly depends on the variance of random communication delays rather than expectation, while the global synchronization error depends on the expectation of communication delays. Considering the characteristic of round delay in pairwise synchronization of sensor nodes, clock offset compensation is added with round delay. The introduction of round delay and decaying factor in consensus based algorithm can decrease both the expectation and the variance of time synchronization error.
学术讨论
主办单位时间地点报告人报告主题
东南大学 数学学院 2012.05 数学系第一报告厅 曹明 Clock synchronization in distributed networks
东南大学 自动化学院 2017.10 中心楼二楼教育部重点实验室会议室 Brian D. O Anderson The Mathematics of Formation Control
复杂工程系统测量与控制实验室 2012.06 中心楼609会议室 刘鹏 内省个体网络的输出一致及常时滞异构网络的同步
复杂工程系统测量与控制实验室 2013.11 中心楼609会议室 邵敬平 Cooperative Source Localization of Multi-agent Systems With a Cooperatively PE Condition
复杂工程系统测量与控制实验室 2012.06 中心楼609会议室 曹青青 文献解读-clock synchronization
复杂工程系统测量与控制实验室 2013.05 中心楼609会议室 曹青青 ATS推导skew的均值和方差
复杂工程系统测量与控制实验室 2014.10 中心楼609会议室 曹青青 LSTS与其他算法收敛速度和收敛误差
复杂工程系统测量与控制实验室 2015.10 中心楼609会议室 曹青青 时钟同步误差影响因素
     
学术会议
会议名称时间地点本人报告本人报告题目
The 32nd Chinese Control Conference 2013.7.26 西安 一种改进的基于分数幂的极值搜索控制方法
The 34th Chinese Control Conference and SICE Annual Conference 2015 2015.7.29 杭州 Topological analysis of the time synchronization error for LSTS algorithm in the WSNs
     
代表作
论文名称
Topological analysis of the time synchronization error for LSTS algorithm in WSNs
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
徐胜元 正高 教授 博导 南京理工大学
达飞鹏 正高 教授 博导 东南大学
朱建栋 正高 教授 博导 南京师范大学
李新德 正高 教授 博导 东南大学
李俊 副高 副教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
陈杨杨 副高 副教授 东南大学