Research On The Improvement Of DSR Protocol For Mobile Ad Hoc Networks

The Mobile Ad Hoc Network(MANET) is a wireless communication network,whose mobile nodes are self organized through distributed agreement. There is no need the support of base, and it has a great advantage in the network flexibility,anti-destroying ability, distributed management and cost, all of these make it widely applied in the military field and civilian field. However, fast moving of the terminal lead to the network topology changing frequently, researcheing effectively routing protocol to adapt to the dynamic network environment of MANET, which is very important to improve the network transmission performance. The DSR protocol is a kind of simple and efficient on-demand routing protocol,it specifically designed for MANET, is one of the most development prospect of routing protocols of MANET.This paper first discusses the characteristics of mobile ad-hoc network and related technology, and focus on routing technology and its research results. Second there is a deep research of the DSR agreement, analyzing its routing finding and routing maintenance operation mechanism, and founding that there are still some deficiencies in the DSR protocol, which are the DSR protocol use flooding to look for the route, all the nodes in network have to participate in the route request message forwarding, that make more network overhead; The whole source routing information must be embedded in each data packet, causing additional routing overhead; High-speed mobile node and the cache expiration routing affects the accuracy of the source routing, which will result in frequent route failure and a large number of land to call routing search process, these seriously affect the quality of network transmission.This paper also makes a deep research on clustering algorithms,and takes the advantage of the clustering structure, proposing an improved scheme based on clustering structure. It on the basis of the original DSR protocol, using the clustering algorithm divide the network into a number of mutually disjoint clusters, and each cluster in the formation is assigned to a unique label. Routing discovery process only happen in backbone network(cluster head and gateway), source routing cluster tags replaced by sequence,nodes in the current cluster can cooperative send the data to the node within next cluster. Because of the connectivity of the clustering structure,there can be lots of interconnected links in the adjacent cluster, so the source route carried by data packet can provide multiple paths to destination,so it has a high stability. TheImproved scheme uses the active routing maintenance mechanism, allowling redundant links quickly repair the failure path,s which improve the reliability of data transmission.Finally, using network simulation device NS2, a contrast is made by experiment between original DSR protocol and its improved scheme,and the results of simulation show that the improved DSR protocol effectively improved the performance of network in the routing overhead, packet delivery ratio and route failure frequency.