Implementation And Improvement Of Multicast Routing Protocol MAODV In Ad Hoc Networks

The wireless ad hoc network is a kind of network built by a group of mobile nodes with wireless communication device, and has characteristics of multi-hop, no center and self-organization. Wireless ad hoc networks have been widely used in local military operations, disaster relief and emergency rescue. In order to support all kinds of ad hoc network distribution service efficiently, as an important part of the network protocol, the multicast routing protocol has deep research significance.Based on an Ad Hoc network node system, the multicast routing protocol MAODV is analyzed and implemented firstly, and then on the basis of MAODV, a new protocol named MAODV-AL(MAODV With Auxiliary Link) is proposed for the purpose of improving the efficiency and reliability of multicast data transmission. The method uses neighbor relationship in the network and the nodes outside the tree to build auxiliary link among the members of sharing tree, so the multicast data not only can reach other nodes through the original link on the sharing tree, but also can use the broadcast characteristic of wireless channel to transmit through the auxiliary link. There are two aspects of optimization effect that can be achieved by the auxiliary link: Firstly, in multicast communication, the data can arrive other multicast members from the source node with less average transmission hops, which improves the efficiency of multicast data transmission; secondly, when the link disconnection leads to the topology segmentation, the auxiliary link can continue to exist in the form of backup links, improves the reliability of data transmission.In order to carry out the performance test and the comparative analysis of two kinds of multicast routing protocols, an ad hoc network topology simulation platform is designed and implemented, and three performance parameters of the MAODV protocol and MAODV-AL protocol including the average of data transmission hops, packet loss rate and normalized routing overhead are counted and compared in two different scenarios: the first scenarios is constant node speed with changing topology size and the second one is constant topology size with changing node speed. As is shown in the simulation results, compared with traditional MAODV, the protocol MAODV-AL has increase in term of normalized routing overhead, but achieves good optimization effect in reducing the data transmission hops and average packet loss rate, achieved the objective of this paper by and large.