| Wireless mobile Ad Hoc networks formed by a collection of mobile nodes through radio links are typically characterized by their multi-hop, temporary and un-center. They can be quickly built up in anywhere and at anytime, and needn't be supported by basic network devices. In these networks every terminal is equal and can move freely. Considering the moving of nodes in Ad Hoc networks and constantly variety of network topology, at the same time, due to the compute-capability of mobile nodes and storage-capacity are low and the energy sources are limited, so the routing protocols have to be simple as best. All those add the difficulty to routing protocol design in Ad Hoc networks. So research and design of stable and highly efficient protocols have been very hot issues for current Ad Hoc networks.Firstly, this thesis introduces current typical Ad Hoc routing protocols, analyzes and compares their performances in sum. AODV(Ad hoc On-demand Distance Vector) has been described in detail and simulated in NS2(Net Simulator 2) under different scenes, performance result is given through the packet delivery fraction, end to end delay, and routing overhead. According to the simulation results, the best working environment of AODV is presented. Because the AODV is a well-known single path routing protocol, it shows that AODV doesn't performance as well as multi path routing protocols in the process of route discovery, and has a comparatively long latency. So we introduce a new improved protocol AODV-BLR(AODV with Backup routing and Local Repair) and its theoretical model on the basic of AODV. This protocol saves several ways to the destination in the route table. If one route is invalid, the backup route is used to send packets immediately. This will reduce route discovery latency and the number of route request, and improve the packet delivery fraction of the protocol. We implement and simulate these two protocols in NS2, and conclude that AODV-BLR has a better performance than AODV. Chapter 1 introduces the characteristic of Ad Hoc networks and classification of Ad Hoc networks routing protocol. The future application and the significance about the research are simply concerned. At last it presents the research work and innovation of this thesis.Chapter 2 describes the principle of AODV in detail, also examples are showed to detail the process of routing.Chapter 3 describes the Ad Hoc routing protocols in detail and their performances are compared and analyzed. Finally we simulated the performances of AODV under different simulation environment.Chapter 4 introduces the detailed process of AODV-BR, and puts forward a newly improved protocol AODV-BLR. It is simulated in NS2 and the result shows that it has a better performance than AODV.Chapter 5 on the basis of using NS2 for a long time, design and implement an automatic simulation tool based in NS2, this tool will greatly reduce the work of simulation process. And the implementation details of this tool are showed in this chapter.Chapter 6 summarizes this thesis, and suggestions for future research are also given.This thesis is supported by National Natural Science Foundation of China (90304018, 60672137) and Specialized Research Fund for the Doctoral Program Foundation of Ministry of Education of China under Grant(20060497015). |
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