【作者】 熊志强；

【导师】 杨宗凯；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2007， 博士

【摘要】 无线传感器网络(Wireless Sensor Networks, WSN)是由部署在监测区域内的大量低成本、微型传感器节点组成,通过无线通信方式形成的多跳自组织网络系统,其目的是感知、采集和处理网络覆盖区域内监测对象的信息,并传输给汇聚节点。在以数据为中心的无线传感器网络应用中,由于数目庞大的节点硬件结构脆弱且能量受限、部署环境恶劣和无线信道本身不可靠等特性,网络经常出现节点损坏、通信链路断开等故障,使得理论上提出的各层网络协议往往难以实际应用,因而近年来研究界普遍认识到,传统基于冗余的容错(Fault Tolerance)技术由于没有综合考虑能量受限等传感器网络特性,因而难以在传感器网络中实现,节能高效的容错技术已经成为传感网络研究的关键问题。一般意义上的容错性是指在故障存在的情况下系统不失效、仍然能够正常工作的特性。传感器网络的容错性指的是当部分节点或链路失效后,网络能够进行传输数据的恢复或者网络结构自愈,从而尽可能减小节点或链路失效对传感器网络功能的影响。目前相关学术研究主要集中在以下三个方面:部署覆盖中的容错。传感器网络的部署阶段,研究主要关注于在部分节点、链路失效的情况下,如何事先部署或事后移动、补充传感器节点,从而保证对监测区域的覆盖和保持网络节点之间的连通。事件检测中的容错。传感器网络应用于外部环境中特定事件的侦测,如火灾、入侵等等。研究主要关注于当网络部分失效时,如何判断当地传感器节点发出的信息是否正确、综合多个传感器节点的汇报信息之后做出的决策是否正确,以及如何最终保证对特定事件检测的成功率等。数据传输中的容错。传感器网络作为一项新型的信息采集技术,将数据传输到汇聚节点是非常重要的环节,研究主要考虑当部分节点或链路失效时,数据如何在网络中存储、聚合、传输、恢复等问题,主要关注网络层及其以上层的容错技术和策略。本文针对传感器网络容错性的需求及容错问题的研究现状,基于数据冗余和路径冗余方法,对传感器网络数据传输过程中的容错技术进行了研究。本文的研究从五个方面展开:(1)传感器网络节点失效分析和模型研究,该模型提供了对协议、算法进行容错检验的平台;(2)适应传感器网络特性的数据源节点前向纠错(FEC)算法研究;(3)基于网络编码技术的数据转发节点容错编码研究;(4)基于路径冗余和跨层设计的数据转发节点容错选路算法研究;(5)集成以上单元容错技术的分簇传感器网络簇内数据交换和簇间数据传输的效率及容错性研究。本文取得的研究成果包括如下几个方面:1.基于数据包的自适应前向纠错编码算法:针对现有的前向纠错码编码复杂、计算量大而不适用于传感器网络的问题,提出一种以数据包为处理对象的自适应FEC编码。该编码采用异或运算,编解码速度快,同时提出了可以进行失效路径诊断的路由反馈机制。2.容错网络编码技术:针对数据传输中间节点现有容错技术效率不高的问题,提出一种结合多路径路由和随机网络编码的数据传输机制。该机制结合多路路径,采取低计算复杂度的线性随机网络编码算法,在保证能量有效性的同时能够对数据包的丢失进行较好的恢复。3.能量感知的容错路由协议:针对现有的传感器网络路由协议没有考虑容错性的问题,采用跨层设计提出了一种能量感知的、基于路径冗余的容错路由协议。该协议利用延时测量的方法检测节点失效,并通过将网络层控制消息附着于MAC层的方式减小控制开销,可以在能量有效的情况下提供较好的实时性和容错性。4.分簇传感器网络数据传输容错策略:以分簇的无线传感器网络为场景,提出了基于网络编码的无线传感器网络簇内数据交换算法和簇间数据传输改进方案,综合运用FEC编码算法和容错选路策略,提高了网络数据交换与传输的效率和容错能力。更多还原

【Abstract】 Wireless sensor network (WSN) consists of a large number of inexpensive minia-ture sensor nodes which are deployed in monitoring region, forming a multi-hop,self-organized network system through wireless communication. And the aim of wire-less sensor networks is sensing, gathering and processing the information in the regioncovered by the network and transferring the data to sink node.In the applications of data centric wireless sensor networks, there are often somefaults happened, such as node failure, wireless link break, etc. It is because themassive nodes in sensor networks are energy constrained and usually deployed inharsh environments, with the unreliable wireless communication channel. Therefore,the protocols and algorithms designed by researchers are not suitable for practicalsensor networks applications. In recent years, the researchers have come to a commonrealization that fault tolerance is a critical issue in the researches on wireless sensornetworks.Generally, fault tolerance means the system works normally even if some fail-ures happen. Accordingly, fault tolerance in wireless sensor networks means thatwhen some nodes or links fail, the network has ability to recover the lost data orstart self-healing mechanism to reduce the performance degradation. Now there arethree primary fields which researchers focus on about fault tolerance issues in sensornetworks:Fault tolerance in deployment and covering. In the stage of network deployment,study on how to optimally deploy sensor nodes to cover the monitoring regionand keep the network connective, when some nodes and links fail.Fault tolerance in event detection. Many wireless sensor networks are applied inspecial event detection, such as fire alarm, intrusion etc. The study issues are:under the situation of nodes and links failing, how to judge the information sentby sensors are correct, and how to make right decision with the consideration oflocal sensor reports, and how to detect the special event successfully.Fault tolerance in data transmission. Wireless sensor network is a new typeof data gathering technic, therefore data transmission is very important. Theresearch issues are in the condition of nodes and links fault, how to storage,fuse, transfer and recover the sensing data. And the corresponding fault toleranttechnics and schemes ares mainly considered in network layer and applicationlayer. To solve the above problems, this thesis addresses on the data redundancy andpath redundancy technologies of fault tolerant data transmission in sensor networks.The content of this thesis includes five issues: (1) modeling and analysis of the senornodes fault; (2) In data source nodes, Forward Error Correct (FEC) codes, which isconstrained by the speciality of sensor networks; (3) Fault tolerant coding technologybased on network coding in data relay nodes; (4) Fault tolerant delivery of datapackets at the relaying nodes based on path redundancy and cross-layer design; (5)E?ciency and fault tolerance of intra-cluster data exchange and inter-cluster datatransmission in clustered sensor networks.The contributions of this thesis include:1. Self-adaptive FEC algorithm based on data redundancy to provide better perfor-mance on delay and loss ratio: There are some existing channel coding algo-rithms, but they are not suitable for applying in sensor networks, due to theirhigh computing, storage, delay cost and in?exibility. We adopt a lightweightXOR-based FEC algorithm in network layer which uses information about packetloss to adjust the coding level according to the dynamics of the network.2. Fault tolerant coding algorithm in data relay nodes based on network coding: Adata transmission mechanism combined with multi-path routing and randomnetwork coding is presented. In routing discovery phase, we constructed multi-path for network coding and a low complexity random network coding algorithmis adopted to recover the loss of data packets with good energy e?ciency.3. Fault tolerant routing protocol with energy e?ciency based on path redundancy:Most routing protocols for sensor networks try to extend network lifetime byminimizing the energy consumption, but have not taken the network reliabilityinto account. To be adaptive to the harsh environment, we propose an energy-aware, load-balancing and fault-tolerant routing scheme. We adopt a cross-layer design to measure the transmission delay so as to detect the failed nodes.The routing scheme works with ACK feedback mechanism to transfer controlmessages to avoid producing extra control overhead messages.4. Fault tolerant schemes in cluster-based wireless sensor networks: Based on clus-tered sensor networks, the intra-cluster nodes topology models are proposed withsome intra-cluster data exchange algorithms. More specially, the network codingalgorithm is discussed in detail. And we improve the inter-cluster data transmis-sion method of the classical clustering protocol in sensor networks, LEACH. Thegateway nodes which are in the overlap of multiple clusters, is used to constructinter-cluster routing. Considering the procedure of data transmission, we apply FEC coding and fault tolerant routing algorithm to enhance the fault tolerantability of sensor networks.更多还原