A preferred link based multicast protocol for wireless mobile ad hoc networks

Existing multicast routing protocols for mobile ad hoc networks can be broadly classified into two categories, tree based protocols and mesh based protocols. Mesh based protocols have high packet delivery ratio compared to tree based protocols, but incur more control overhead. The packet delivery ratio of tree based protocols decreases with increasing mobility. This is due to the occurrence of frequent tree breaks and lack of proper tree maintenance mechanisms. These tree breaks result in frequent flooding of JoinQuery packets by the multicast group member nodes which try to get re-connected to the tree. These broadcast packets collide with the data packets and reduce the efficiency of the protocol. We propose an efficient protocol which we call as preferred link based multicast protocol (PLBM). PLBM uses a preferred link approach for forwarding JoinQuery packets. Subsets of neighbors of a node are selected using a preferred link based algorithm. These nodes, termed as preferred nodes, are only eligible for further forwarding of JoinQuery packets. We also propose a quick link break detection mechanism that locally repairs broken links. Simulation results show that our protocol performs better than other existing multicast protocols in terms of packet delivery ratio and control overhead.