Overlay multicast protocol builds a virtual mesh spanning all member nodes of a multicast group. It employs standard unicast routing and forwarding to fulfill multicast functionality. The advantages of this approach are robustness and low overhead. However, efficiency is an issue since the generated multicast trees are normally not optimized in terms of total link cost and data delivery delay. In this paper, we propose an efficient overlay multicast protocol to tackle this problem in MANET environment. The virtual topology gradually adapts to the changes in underlying network topology in a fully distributed manner. A novel Source-Based Steiner tree algorithm is proposed for constructing the multicast tree. The multicast tree is progressively adjusted according to the latest local topology information. Simulations are conducted to evaluate the tree quality. The results show that our approach solves the efficiency problem effectively.

Overlay networks have made it easy to implement multicast functionality in wireless ad hoc networks. Their flexibility to adapt to different environments has helped in their steady growth. In MANETs, the position of nodes constantly changes; as a result, overlay multicast trees that are built using location information to account for node movement would certainly have a low latency. However, the performance gains of such a tree are offset by the overhead involved in maintaining precise location information. As the degree of (location) accuracy increases, the performance improves but the overhead required to store and broadcast this information also increases. In this paper, we present SOLO-Net�, a design to build a sub-optimal location aided overlay multicast tree, where location updates of each member node are event based. Our simulation results indicate that such a sub-optimal tree does not compromise the performance gains of a location aided overlay multicast tree. 1.