【作者】 马丽霞；

【导师】 朱秋萍；

【作者基本信息】 武汉大学 ， 通信与信息系统， 2004， 硕士

【摘要】 Ad hoc网络是一种工作在无固定结构环境下的自组织的无线移动网络。它适用于军事或是一些战略应用场合，例如，战场上部队快速展开和推进、发生地震或水灾后的营救等。在没有网络基础设施的情况下，Ad hoc网络可以快速组网，其节点可以移动，网络中的每个节点既充当主机又充当路由器。由于Ad hoc网络具有组网快捷、灵活，且不受有线网络约束等优点而具有广泛的应用前景。 由于Ad hoc网络的拓扑动态性，使得常规路由协议在该环境下无法正常运行。因此，对该环境下路由协议的研究成为了Ad hoc网络中研究的主要课题。本文首先研究了现有的Ad hoc路由协议，分别介绍了两类路由协议，表驱动路由协议和按需驱动路由协议。然后使用网络仿真器NS-2对代表了Ad hoc的两类协议的四种典型路由协议进行了仿真，包括AODV、DSR、DSDV和TORA。给出了在不同的移动和流量场景下，这四种Ad hoc典型路由协议的仿真结果。结果表明按需路由的性能较优越，特别是在路由开销方面。但是在高负载的情况下，其路由发现机制中的查询泛洪会使这种优势大大降低。 针对这种情况，本文提出了两种控制按需路由查询泛洪的技术。第一种是查询局部化技术，它可以防止整个网络范围内的泛洪，有效地将泛洪控制在一个小范围内。查询局部化技术可以利用两类信息，一类是路径信息，一类是节点位置信息，本文对利用这两类信息来控制泛洪的协议都分别进行了阐述和仿真，仿真结果表明利用这两类信息的查询局部化技术都可以显著减少路由开销，利用路径信息可以更多的降低路由开销。第二种是多径路由技术，它使用备选路由来减少泛洪发生的频率。文中研究了两种不同的多径技术，一种只在源路由有备选路由，另一种是初始路由中的所有节点都有备选路由。仿真结果表明这两种多径技术都能显著减少协议的路由开销，而且当初始路由中的所有节点都有备选路由时，协议的路由开销更小。 目前，关于Ad hoc网络路由协议的研究才刚刚起步，而路由协议是关系到Ad hoc网络能否运行的关键因素，因此本文对Ad hoc网络中路由协议的研究和优化不仅在理论方面具有重要意义，而且为其应用提供了科学依据。更多还原

【Abstract】 A mobile Ad hoc network is an autonomous system of mobile hosts connected by wireless links. Such networks are useful in military and other tactical applications, e.g., emergency rescue or exploration missions, where cellular infrastructure is unavailable or unusable. In such a network, each mobile node operates not only as a host but also as a router. This network has a series of the strengths, for example: MANET can be built rapidly and easy, and it is not set measures to by wired network, and so on.Because of constantly changing topology, Ad hoc networks can’t adopt traditional protocols. Research of routing protocols becomes the most important part of the research of Ad hoc. This dissertation presents a comparative simulation study of on-demand protocols with the more traditional proactive protocols on a common platform across a range of traffic and mobility scenarios. This simulation cover a range of design choices: AODV, DSR, DSDV, TORA. The simulation results show that on-demand protocols indeed demonstrate low routing overheads, but over-reliance on query flooding can actually cause on-demand protocols to lose most of this overhead advantage at high loads.As a countermeasure, we develop and evaluate two techniques that reduces the routing overhead for on-demand protocols. The first technique, called query localization, uses certain routing histories to prevent network-wide query flood. It effectively limits the query to a small region where the route is very likely to be found. Query localization techniques can use two kinds of information, one is path information, the other is position information of node. Simulation results show that the query localization techniques can reduce routing overhead notably, and the routing overheads are smaller when using path information. The second technique, called multipath routing, focuses on reducing the frequency of query flooding by exploring multiple, disjoint routes per flood operation. This provides the routing protocol with alternate routes when the primary route breaks. Two variations were explored. In the first, only the source gets multiple alternate routes. In the second, each intermediate node on the primary route gets an alternate route (aside from the source). Simulation results show that either of these techniques can reduce routing overheads significantly. When each intermediate node on the primary route gets an alternate route, the routing overheads are smaller.At present, the research about Ad hoc network routing protocols has just started, and the routing protocols concerns the key factor whether Ad hoc network could run, So this paper is not merely significant to the research and optimization of the route agreement in Ad hoc network in theory, and also offer scientific basis for its application.更多还原