Robust and Scalable Geographic Multicast Protocol for Mobile Ad-hoc Networks

Group communications are important in mobile ad hoc networks (MANET). Multicast is an efficient method to implement the group communications. However, it is challenging to implement scalable, robust and efficient multicast in MANET due to the difficulty in group membership management, multicast packet forwarding and the maintenance of a tree-or mesh-based multicast structure over the dynamic topology for a large group size or network size. We propose a novel robust and scalable geographic multicast protocol (RSGM). Scalable and efficient group membership management has been performed through zone-based structure, and the location service for group members is combined with membership management. Both the control messages and data packets are forwarded along efficient tree-shape paths, but there is no need to actively maintain a tree structure, which efficiently reduces the maintenance overhead and makes the transmissions more robust to dynamics. Geographic forwarding is used to achieve further scalability and robustness. To avoid periodic flooding-based sources´ announcements, an efficient source tracking mechanism is designed. Furthermore, we handle the empty zone problem faced by most zone-based routing protocols. Our simulation studies show that RSGM can scale to large group size and large network size, and a high delivery ratio is achieved by RSGM even under high dynamics.