Aodv Protocol Performance In Manet Research

Wireless mobile ad hoc network (MANET, Mobile Ad hoc Network) is a special kind of network in which nodes don't relay on any existing infrastructure. The characters of MANET include of quick change of topology, multi-hops, decentralization, limited power and bandwidth. Routing protocol is one of the most important factors that limit development of MANET. AODV (Ad hoc On-demand Distance Vector) is a typical on-demand protocol with simplicity, loop-freedom, on-demand routing. The faults of AODV include of large amount of redundant messages, poor protocol efficiency especially in mobilization.In order to research these faults and give a resolution, this article introduces the basic algorithm of AODV and researches the influence of redundant messages at first, designs a model of producing redundant RREQ message, which can store and forward RREQ messages. This model shows the influence of redundant RREQ to protocol performance. Secondly, it presents an AODV modification, in which we set a lifetime for RREQ messages and set delay when the immediate node send a RREP message and forward a RREP message in order to balance the route load and decrease the number of RREQ messages. We call this modification AODV-DL. At the same time, we present another modification based on count method—AODV-BH. This modification uses the inherent property that some nodes needn't forward messages in dense area but it can achieve better performance. The immediate node will forward RREQ messages or not according to the amount of RREQ that node received in a fixed time in AODV-BH. If the amount of RREQ exceeds a threshold value, the node will keep silence to any RREQ messages in a fixed time. Compared with AODV and AODV-DL, AODV-BH fits the dense network or heavy business network better.Finally we simulate these modifications in NS2 network simulator, and study the packet delivery ratio, average end-to-end delay, routing load, path optimality according to RFC 2501. The result shows these modifications have better performance than basic AODV protocol.