Mobile Ad Hoc Network Routing Protocols And Optimization Design

A mobile Ad hoc network is an autonomous system of mobile hosts connected by wireless links without an infrastructure. Such networks are useful in military and other tactical applications, e.g. army's quick spread in the battlefield, emergency rescue or exploration missions after earthquake or flood, where cellular infrastructure is unavailable or unusable. In an Ad hoc network, each mobile node operates not only as a host but also as a router. Ad hoc networks have a series of advantages, for instance, they can be built rapidly and easily and they are not restrained by wired networks and so on. Therefore, Ad hoc networks surely have a bright future.Because of constantly changing topology, Ad hoc networks cannot just adopt traditional routing protocols which do well in wired networks. Researches of developing new routing protocols for Ad hoc networks become the most important part of the Ad hoc network study.In this paper,the actuality and prospect of Ad hoc networks are summarized in chapter one, including the definition, architecture, characteristics, application fields and critical technologies of Ad hoc networks. In chapter two, the classification of routing protocols of Ad hoc networks are introduced. Two important routing protocols (AODV and DSR)are briefly introduced and compared. In the third chapter,we compared the performance of three on-demand routing protocols(AODV,DSR and TORA) under three scenarios. The results showed that AODV performed better than the other two routing protocols. Then, we give a detailed introduction of AODV, including the key technologies and operations in chapter 4. In the chapter of 5,we examine the influence on the performance of AODV which respectively led by the movement of the nodes, the number of the nodes, and load of the network. In chapter 6, both the advantage and weakness of AODV are analyzed. Then we propose an improvement of AODV against one weakness of the protocol. In the improvement method, we expand the packet format of both RREQ and RREP in order to make them have the ability to take more addresses during the routing discovery process. We also changed the way of processing every RREQ and RREP received. Through all these changes, the optimized AODV can acquire more routes during a routing discovery process. Thus, the performance of AODV is improved. Finally, the improvement is proved by some simulation test. Chapter 7 is the final chapter and we summarized our current work and some future work is prospected.The simulation experiments in this paper are carried out on OPNET network simulation environment. The results and conclusions of this paper may enrich the knowledge of Ad hoc network technologies and be helpful for developing real Ad hoc network systems in the future.