Demand Routing Protocols In Ad Hoc Networks Research And Improvements

With the development of science and technology, portable computer and palmtop computer are increasingly prevalent, and the wireless communication technology develops promptly. In some cases, for instance, the rapid expansion of the army in a war, the rescue after earthquake or flood, it need a communication technology which don't depend on any network facility erected beforehand. Then Ad Hoc network emerge as the times require. Ad Hoc network is one special kind of mobile network which don't need fixed basestation. It's one sort of self-creation , self-organization and self-supervisory network which formed by the cooperation of a boodle of autonomic wireless node or terminal who have wireless R-T unit.In Ad Hoc network, every host must be a router at the same time. And nodes in the network could move discretionarily, which make the topology change frequently and the routing protocol be assumed to reconstruct and maintain routing path in time. Because of the highly dynamic variation of topology in Ad Hoc network, the conventional distance vector routing protocols and link status routing protocols are not suitable. Since 1970 year, DARPA subsidize one extraordinary research—Ad Hoc network, a lot of protocols of Ad Hoc are under exploitating and developing. The route mechanism of Ad Hoc network should conform to three basic feature: the population density of mobile node, the topology of nodes, and the operating mode of network.There are two kind of routing protocols for Ad Hoc network : table- driven and on - demand routing protocol.The article firstly described the significance and the target, it also describes the current status of the schedule. In the second section we analyzed and compared the performances of some kind of table- driven and on - demand routing protocol, in which the expounding of on-demand protocol is highlight. In the third section we present an optimized protocol: OAODV base on AODV, and introduce the realization of this optimistic protocol in detail. In the fourth section we completed simulation with different scenes based on NS2 and analyzed the performance of OAODV according the data obtained by simulation.