A multicast routing protocol for multihop wireless networks

We propose a new protocol, Clustered Group Multicast (CGM), for multicasting in multihop wireless networks. In CGM, there is a set of forwarding nodes (called multicast backbone) which are responsible for forwarding multicast datagrams. Unlike the multicasting protocols in wired networks (e.g. Internet) which construct and maintain a shortest path tree for every multicast {source, group} pair, the connectivity among the nodes in the backbone is of no longer importance. Thus, there is no tree maintenance overhead. In addition, a key feature of CGM is the use of the advertising agents to reduce advertising traffic to the system. An advertising agent acts as both a server and a client for the purpose of advertising join requests on behalf of its local clients. Because in CGM multicast traffic is only allowed to be delivered over the backbone, CGM restricts the amount of hosts participating in the backbone to decrease the impact of multicast traffic to the system. From the simulation results, the multicast group management traffic and multicast datagram traffic are much less than the other protocols. This is particularly important for wireless networks which lacks bandwidth.