Study Of A Multicast Routing Protocol In Airborne Ad Hoc Networks

In recent years, mobile ad hoc networks have been widely studied in many fields, because they do not rely on a fixed infrastructure and have the advantages of self-organization, wide coverage and survivable ability. With the increase of business requirements, multicast routing technologies are becoming more and more important in mobile ad hoc networks. So this dissertation is mainly concerned with multicast routing protocols in airborne ad hoc network.This thesis focuses on the hierarchical airborne ad hoc network that includes a backbone and several subnets. The backbone topology is relatively stable, and nodes in it can obtain the link duration and unicast routing information. The subnet topology changes frequently. The protocols overheads of traditional multicast routing are high, and they may cause loss of data due to link disconnections. Therefore, in order to satisfy the multicast requirements in airborne ad hoc network and provide packets reliable and effective transportation, an appropriate multicast routing protocol is studied in this thesis.The multicast routing protocol in the backbone in this article is improved on the basis of ODMRP protocol. Because of periodic flooding control information to establish a forwarding mesh and refresh routers, ODMRP protocol overhead will be relatively high. Considering from the two respects reducing network overhead and the characteristics of the backbone, a multicast routing protocol in the backbone is designed. The improvements of ODMRP protocol include the following aspects. Firstly, source nodes in new protocol obtain links duration in the network, and they begin to establish a forwarding mesh after some route table fail. Secondly, when a link is disconnected, the downstream node uses the known unicast routers to maintain multicast routes. Finally, in the new protocol nodes can active join and leave. The routers in subnets are set up through flooding and pruning. That is, when the multicast business data arrives, they are flooded to destination nodes, and then the multicast destination nodes send prune message to establish subnets multicast routers. All of these avoid frequent routers maintenance process when the data do not arrive and reduce the amount of data forwarding.At last, computer simulations are done. This thesis makes a simulation about the multicast routing protocol in airborne ad hoc network by the OPNET. The simulation results show that the designed multicast routing protocol in airborne ad hoc network can realize multicast and have better stability.