Overlay small group multicast mechanism for MANET

In order to provide the multicast service in MANET, a lot of multicast routing protocols have been proposed. Most of them create tree or mesh-based graphs and require network nodes over the tree or mesh to maintain the membership information. In particular, high node mobility causes the tree or mesh to be broken and reconstructed by generating much overhead to manage the membership at network nodes. In accordance with overlay multicast protocols to reduce such overhead, which enables the packet transmission regardless of the movement of intermediate nodes over the paths between group members, we propose an overlay small group multicast mechanism, called SPM (Shortest Path overlay Multicast) for MANET. SPM multicasts packets over the shortest paths from a source to each group member without duplicate packet delivery over common partial paths. When creating a multicast overlay tree, SPM utilizes the route information provided by ad hoc unicast routing protocol without further control messages and any other information. Extensive simulations through NS-2 simulator proved that SPM has better throughput, loss rate and packet transmission delay than MAODV, a typical tree based multicast routing protocol used in MANET.