【作者】 孙强；

【导师】 李腊元；

【作者基本信息】 武汉理工大学 ， 计算机应用技术， 2007， 博士

【摘要】 Ad hoc网络作为移动通信和计算机网络结合的产物，是一种无需任何基础设施支持就可以实现通信的自组网络。与传统的固定网络和蜂窝网络相比，它具有部署快速，环境适应力强，抗毁性强等特点，因而在诸如战场、灾难救助、野外考察、工业现场监控等领域有着广泛的应用前景。但由于无基础设施的支持且网络拓扑结构动态变化，因此Ad hoc网络中存在着许多与传统网络不同的新问题和挑战。这包括路由问题、能量问题、QoS问题和安全问题等。与传统无线网络不同，Ad hoc网络作为一种多跳自治系统，其网络中每个节点都具有路由功能。由于传统的距离矢量和链路状态算法需要在节点间交换大量信息，且需花费较长时间才能达到算法收敛，因此并不适用于节点频繁移动，网络拓扑结构高度动态变化的Ad hoc网络环境。如何设计一个简单高效的路由协议使之能感知网络拓扑结构的变化，动态维护网络拓扑的连接，更新链路状态，快速准确发现路由，是当前Ad hoc网络急需解决的关键问题之一。在无线通信系统中，能耗一直是衡量系统性能的重要性能指标。降低能耗不仅可以延长网络节点的工作时间，而且还可以提高整个网络的鲁棒性。另外，通过采用低能耗的无线通信还能缓解人们对使用移动通讯可能造成损害健康问题的担忧。Ad hoc网络作为一种无线移动网络，与其他类型的无线网络一样，也存在着能量问题。与其它类型的无线网络相比，在Ad hoc网络中，能量问题不仅对网络性能有影响而且还关系到整个网络的“生死”。因此，能量问题是Ad hoc网络需要解决的关键问题之一。本文就移动Ad hoc网络中节能与路由的一些关键技术进行了讨论。就以下几个方面进行了创新性研究：1)基于距离和计数门限的分布式Ad hoc网络广播算法广播作为无线Ad hoc网络中一种重要通信方式，被许多单播和多播协议用来完成路由建立和路由维护工作。但是在Ad hoc网络中，采用洪泛方式广播，会带来广播风暴问题。针对Ad hoc网络中广播风暴问题，采用跨层设计方法，设计了一种分布式广播算法。该算法利用从物理层提取的报文接收信号强度信息和从网络层提取的相邻节点信息确定广播报文转发节点，并动态调整MAC层的退避时间和网络层的报文发送等待延迟时间。仿真实验结果表明该算法在显著减轻广播风暴问题的同时也取得了较高的协议能效。2)非合作Ad hoc网络功率控制博弈优化算法本文针对Ad hoc网络中能量控制问题做了讨论，由于在Ad hoc网络中，采用控制数据报文向相邻节点发射功率的方法来提高能量使用效率是一种常用的方法，但是采用功率控制也会对网络连通性、延迟和容量带来负面影响。因此本文提出了一种以满足网络连通性、容量最大化、网络半径最小为目标的分布式非合作功率控制博弈算法，并给出了对该算法纳什均衡存在性和唯一性的证明。仿真试验结果表明，该算法具有较好的综合性能。3) Ad hoc网络最大化生命周期QoS路由协议由于移动无线自组网是由一组移动节点组成的、无需任何基础设施支持的网络自治系统，网络中各节点以多跳方式转发报文。随着网络应用及Internet的发展，要求在移动无线自组网中提供一定的服务质量(QoS)保证。在无线自组网中，每个节点都以电池作为工作能源，且每个节点既是主机还是路由器，当一些节点由于能量耗尽而停止工作时，将会导致整个网络的崩溃。因此在移动无线自组网中，进行路由选择时，仅考虑QoS路由约束是不够的，还需考虑能耗问题。在保证QoS的同时如何延长网络的生存时间已经成为QoS路由的一个重要目标。针对这一问题，本文给出了针对Ad hoc网络中存在多业务情况下网路生命周期最大化QoS路由问题描述，通过将网络生命周期最大化QoS路由问题转化为最大流问题，借鉴最大流算法思想，提出了一种基于最大流的分布式网络生命周期最大化QoS路由协议，并给出了协议描述、实现及性能分析。仿真结果表明该协议在满足业务QoS要求的基础上使网络生命周期得到较大的延长，同时改善了数据分组递交率和端到端延迟。本文得到国家自然科学基金项目(60672137，90304018)，教育部博士点基金项目(20060497015)，湖北省武汉市科技攻关项目(20041001001)的资助。更多还原

【Abstract】 The wireless ad hoc networks are product in combination with mobilecommunication and computer networks. A mobile ad hoc network is a self-organizingnetwork without any existing fixed communication infrastructure support. Comparedwith the traditional fixed networks and wireless mobile cell networks, the ad hocnetworks have some special characters such as instant deployment, strongenvironment adaptability and survivability and so on. So the ad hoc wirelessnetworking technology shows great potential and importance in many situations, suchas in military, disaster-relief, field investigation and industry field supervisionapplications. Because of the features of no existing fixed communicationinfrastructure support and dynamic changed network topology in ad hoc networks,there exist many problems and new challenges including routing, energy management,QoS (Quality of Service) guarantees, security and etc., which are different from thosein the traditional fixed networks.As a multi-hop autonomous system, the ad hoc networks are different from thetraditional wireless networks, in which each node acts as both host and router.However, traditional routing algorithms based on distance vector or link-state needexchange information between nodes and take long time to converge, which are notsuitable for mobile, dynamic changed topology ad hoc networks. So how to design asimple and efficient routing algorithm that can sense the change of network topology,maintain connectivity of network dynamically, update link state and find properroutes quickly is one of the key problems in ad hoc networks.In wireless communication system, energy consumption is a important metric tomeasure the system performance. In addition, low energy consumption can not onlyprolong operating time of the devices but also improve the system robustness.Moreover, through using lower power consumption to communicate can help peopleto release their anxiety for the health hazard from wireless communication. Theenergy problem also exists in ad hoc networks. Compared with other wirelesscommunication systems, it will influence not only on the performance of network butalso on "life-or-death" of the network. Therefore, energy conservation has becomethe key problem of ad hoc networks.This dissertation addresses the key technologies about energy conservation and routing in ad hoc networks and has made innovative progress in the followingrespects.1) A Distributed Broadcasting Algorithm for Ad Hoc Networks based onDistance and Counter ThresholdIn mobile ad hoc networks, many unicast and multicast protocols depend onbroadcasting mechanism to finish control and route establishment functionality. But astrightforward broadcasting in ad hoc networks will be easy to result the broadcaststorm problem. In order to deal with the broadcast storm problem in ad hoc networks,this dissertation proposes an efficient distributed broadcast algorithm which usescross-layer design manner. It changes the backoff defer in MAC layer according tothe receiving signal strength to estimate the distance from the sender. It alsoschedules the packet transmitting in network layer through inducing the distancethreshold and counter threshold. The simulation experiments have demonstrated thatthe proposed broadcast algorithm can lighten the broadcast storm problem andimprove the energy efficiency of broadcast.2) A Power Control Algorithm Based on Game Theory in Ad Hoc NetworksThis dissertation investigates the power control problem in ad hoc networks. Inmobile ad hoc networks, power control method is an efficient way to improve theefficiency of energy used to transmit data packets. However, it will also producenegative influence on the network connectivity, delay and capacity. So regarding asthe objectives of network connectivity, maximum network capacity and minimumnetwork delay, a distributed power control algorithm based on non-cooperative gametheory is proposed. The theoretical proving is given for the existing and uniqueness ofthe algorithm’s Nash equilibrium. Simulation results show that the algorithm isefficient and has a good integrated performance.3) A Distributed Maximum Network Lifetime QoS Routing Protocol in MobileAd Hoc NetworksA mobile ad hoc network is composed of a group of mobile wireless nodeswhich form a network independently of any centralized administration. The nodes inthe network communicate with each other in a multi-hop manner. With thedevelopment of the network applications and the technology of Internet, it demands MANETs to support Quality of Service (QoS) in a certain extent. Since the mobilenodes are battery-powered and each mobile node in a MANET performs the routingfunctions, the "death" due to energy exhaustion of even a few nodes might cause thedisruption of the entire network. So for obtaining routes on a MANET, it is notsufficient to only consider about traditional QoS constrints. Power consumptionshould also be taken into consideration. And how to prolong the network lifetime hasbecome very an important objective for guaranteeing QoS in a MANET. Finally, inthis dissertation, a formulation is given to describe the problem of maximizing thenetwork lifetime with QoS routing which is also proved as the maximum flowproblem later. Referring to the idea of solving the maximum flow problem, adistributed maximum network lifetime QoS routing protocol (DMNLQRP) isproposed. The performance of the protocol is analyzed. The simulation results showthat DMNLQRP can not only prolong network lifetime but also improve data packetsdelivery rate and delay.更多还原