Research On Optimization Of AODV-based Multipath Routing Protocol

Mobile Ad Hoc network (MANET) is a multi-hop temporary autonomous system composed of mobile nodes having wireless transceivers. Because MANET does not depend on any established infrastructure and has not the central controlling node, and is good in performance to stand against destruction, it is applicable to many situations that have difficulties in wiring networks. Based on above advantages, MANET plays an important part in military applications, and also has good prospect in civil applications. AODV (Ad Hoc On-Demand Distance Vector) protocol is an on-demand routing protocol specifically designed for MANET and is one of the few MANET routing protocols authorized to publish as the RFC documentations by IETF and will possibly play an important role in the future MANET applications.Based on the detailed research on MANET characteristics, this paper analyzes the present research status of AODV multipath routing protocol at home and abroad and summarizes the advantages of multipath routing. After deeply analyzing the mechanism of AOMDV and thoroughly evaluating the protocol performance with NS2, a new protocol named AODV-PD is proposed to solve the problems of AOMDV. The new protocol is an optimization to AOMDV with path diversity.After route discovery, AOMDV only selects one primary path on transmission, and meanwhile does not perform any kind of maintenance of alternate paths. It cannot make full use of the multiple paths obtained in the earlier routing discovery phase. As a result, when an alternate path is selected after the failure of a primary path, the alternate is likely to be also invalid. To remedy this problem, the AOMDV-PD proposed by this author introduces the conception of the path correlation factor, and a distributed algorithm is designed to process the multiple routes with the lower correlation factor during the route discovery phase. AOMDV-PD uses multipath to transmit packets simultaneously, and the physical diversity of paths can reduce the interference from each other. The results of NS simulation to the optimized AOMDV-PD show that the packet delivery ratio and the end-to-end delay are enhanced obviously; meanwhile the routing overhead basically is not increased.