Research And Improvement Of On-demand Routing Protocol In Ad Hoc Networks

A mobile ad hoc network is a multi-hop and temporary network of mobile nodes equipped with wireless transmitter-receiver set,which needs not the use of any existing fix infrastructure and central management. The nodes in the network act both as host and router,and they participate in route establishment and packet forwarding according to the routing algorithm. The traditional Internet routing protocol can not satisfy the need of Ad hoc network because of the frequently changing network topology, the research and design of stable and effective routing protocol has become the hotspot of Ad hoc research.Ad hoc routing protocols can be classified into two major types: table-driven and on-demand. There are some constraint in this wireless network,such as frequent host mobility, smaller radio propagation,bandwidth limitations and battery power, so on-demand protocols can satisfy the Ad hoc networks better. On-demand protocols attempt to discover a route only when a node originates a packet,and need not periodically disseminate topology updating information. So it can avoid much unnecessary routing overhead and save the network bandwidth,but it responses to the changed topology slowly. We proposed two improved methods for the Dynamic Source routing protocol through the deep research on it.On-demand routing protocol often uses the routes in the route cache to send dada packet and reply the RREQ message, so whether the cache can be updated in timely is an important factor for the performance of on-demand routing protocol. The paper first proposed a novel cache updating method to update the route cahches in timely. After that the paper gave a novel packet salvage algorithm which can fully use the routes in the node's route cache,and the algorithm would repair the source route if the source route has no another route to the destination. Then the source node can avoid a new route discovery process which can greatly save the routing overhead.The dynamic source routing protocol can get more than one routes to the destination in a route discovery process,these route's reliability are different,the closer it to the destination,the more reliability it has. The paper proposed a method to distinguish the reliability of these routes,so the node can select a most reliable route while it sends data packet or reply the route request message. We simulated the two improved algorithm using the network simulation software OPNET,the result proved that both of them performed better than the dynamic source routing protocol from the aspect of average end-to-end delay and packet delivery ratio.