Optimized multicast routing algorithm based on tree structure in MANETs

Mobile Ad hoc Networks (MANETs) play an important role in emergency communications where network needs to be constructed temporarily and quickly. Since the nodes move randomly, routing protocols must be highly effective and reliable to guarantee successful packet delivery. Based on the data delivery structure, most of the existing multicast routing protocols can be classified into two folders: tree-based and mesh-based. We observe that tree-based ones have high forwarding efficiency and low consumptions of bandwidth, and they may have poor robustness because only one link exists between two nodes. As a tree-based multicast routing protocol, MAODV (Multicast Ad hoc On-demand Vector) shows an excellent performance in lightweight ad hoc networks. As the load of network increases, QoS (Quality of Service) is degraded obviously. In this paper, we analyze the impact of network load on MAODV protocol, and propose an optimized protocol MAODV-BB (Multicast Ad hoc On-demand Vector with Backup Branches), which improves robustness of the MAODV protocol by combining advantages of the tree structure and the mesh structure. It not only can update shorter tree branches but also construct a multicast tree with backup branches. Mathematical analysis and simulation results both demonstrate that the MAODV-BB protocol improves the network performance over conventional MAODV in heavy load ad hoc networks.