【作者】 年梅；

【导师】 王能；

【作者基本信息】 华东师范大学 ， 系统分析与集成， 2006， 博士

【摘要】 Ad Hoc网络无需固定基站的支持，节点之间通过无线链路进行通信，使用方便、配置灵活，已经引起了人们广泛的关注。Ad Hoc网络的研究领域中有许多需要解决的问题，如：路由协议、能量节省和网络安全等，其中路由协议是Ad Hoc网络实现的关键问题。路由可分为单播路由、组播路由和广播路由。本文研究具有平面结构的Ad Hoc网络的单播和组播问题，围绕着优化和提高网络性能等问题进行了深入的研究，主要的研究内容和创新性结果如下： 1．网络拓扑的动态性使路由节点维护的路由信息具有很强的时效性。针对Ad Hoc网络拓扑易变的特性，必须设计出简单有效的路由维护算法。本文将链路状态预测算法引入到Ad Hoc网络的单播路由协议AODV中。解决了AODV不能及时发现断裂链路而导致网络报文丢失和网络传输时延增加的问题。链路预测算法根据无线传播的原理和节点运动的规律，利用接收报文的能量发现即将失效的链路，然后对即将失效的路径提前作出处理。本文提出了二个基于链路失效预测的路由维护算法。第一个算法是：当节点发现即将失效的链路后，在该链路失效前，将链路即将失效的信息传递给所有使用该链路的活动路径的源节点，由源节点根据需要进行相应的处理。这样避免了失效链路的使用以及报文的丢失，降低了网络中报文的投递时延。第二种方法称为抢先式路由算法，即在路由失效前不但要报告链路失效的信息而且修复失效路径，为了避免产生过多的控制开销，我们使用了局部路由修复的方法。抢先式路由算法降低了网络中报文的投递时延，减少了因无路由而丢失的报文数，但导致路由开销略有增加。 2．组播是Ad hoc中的重要应用，组播的实现需要良好的组播路由协议的支持。在已提出的组播协议中，ODMRP协议性能良好，对节点移动导致的网络拓扑结构变化的抗毁性也较强。但当网络中发送节点数较多时，ODMRP协议中冗余路径太多，使网络中的无效冗余报文占用过多的网络带宽资源，容易引起信道资源的竞争和网络冲突。针对该问题，本文提出了两个基于概率的数据转发算法，并将其应用到ODMRP协议中。第一个转发算法使ODMRP协议中的转发节点根据局部转发节点的密度，动态地选择转发概率并按此概率转发数据报文。当局部转发节点密度较小时，使用较大的转发概率，这样不会降低网络的报文投递率；当局部转发节点密度较大时，则以较小的概率转发报文，从而控制网络中的冗余报文数，减少网络带宽的浪费程度，提高报文传递的效率。第二个概率转发算法使ODMRP中的转发节点根据收到同一个报文的次数和与发送报文的节点距离决定是否转发该报文，如果同一个报文被收到的次数达到某个阈值，则丢弃该报文，否则进行转发操作。阈值通过接收节点与发送节点间的距离动态调整，如果转发节点距离发送节点较远，则设置较大的阈值，使报文被转发的概率增加；否则，设置较小的阈值，使报文被丢弃的概率增加。仿真结果证实，这两个转发算法通过减少网络中无效冗余的数据报文，提高了ODMRP中报文传递的有效性，明显降低了数据报文的传输时延，增强了协议的可扩展性。 3．本文还提出了反应式的组播路由协议RMMP。RMMP是基于负载的反应式组播路由协议，因此能有效地利用网络资源。此外，协议从所有发送节点中选出一个核更多还原

【Abstract】 Mobile Ad hoc Network (MANET) is gaining increasing popularity in recent years because of its ease of deployment. Ad Hoc Network owns some characteristics like self-organization, multi-hop and a frequently changed topology. MANET is useful when infrastructure is not available, impractical, or expensive.The uniqueness of Wireless Ad Hoc Network made it impossible to adopt the technologies utilized in traditional networks. So some new protocols and technologies need to be developed specially for Ad Hoc network on channel access, network security and routing. We focused on the routing protocols and algorithms of Ad Hoc network in this paper, and we chose the unicast and multicast routing techniques as our main research points. The main research works and results are listed as follows:In this paper, the unicast protocols are analyzed and compared against each other. Our study shows that AODV is better suited for mobile networks than other routing protocols. A major aspect of ad-hoc networks is that the nodes can move randomly, which requires the routing protocols in ad-hoc network to respond quickly to the network topology change in order to guarantee successful data packet delivery. But AODV can’t find the link error and repairs the invalid path in time, which results in the longer end-to-end packet delivery latency and much more control overhead. The link state prediction algorithms by received data signal strength is proposed to resolve the problem. A link state prediction method can predict the exact link breakage time of an active path. In this thesis, two enhanced route maintenance algorithms of link state prediction method on AODV are proposed. The first one aims to find the to-be-broken link by link state prediction and then notify the corresponding source nodes before the breakage occurs actually. So the invalid paths are avoided to be used. The second one is called preemptive algorithm which is associating the proactive and reactive protocol. This algorithm not only finds the to-be-broken link but also takes response to repair the invalid path corresponding to the link in the local area. So the packet transmission is not affected by the broken link. Simulation results demonstrate that these two algorithms reduce the end-to-end delivery latency and increase the packet delivery ratio at the heavy traffic load with slight overhead increase.We provide a detailed description and comparison of Ad Hoc multicast protocols. By this, we conclude that ODMRP is a suitable protocol for MANET in the situation of node moving frequently. Its performance is well in most condition, but the network overhead increases drastically because of the numerous redundant data packet to be relayed, which in turn results in the network performance degration quickly. Two data forwarding algorithms are introduced in this paper to resolve this problem. The two algorithms are probability-based data forwarding algorithm which intents on reducing the probability of forwarding the data packet, thus the redundant data packets in the network are reduced accordingly.The first one uses the number of neighbor forwarder to determine the relay probability. Then the forwarding nodes relay data packet following the probability. The second one is used to determine whether the packet should be relayed or be discarded更多还原