Improvement of multicast routing supporting Mobile Ad Hoc Networks with unidirectional links

In Mobile Ad Hoc Networks (MANETs), unidirectional links between nodes exist due to the variation of transmission power or wireless interferences. In such a network, traditional routing protocols for bidirectional links cannot use unidirectional links as transmission paths. This causes the decline of network's connectivity and capacity. In recent years, researchers have addressed unidirectional links and the associated unidirectional routing problem. To overcome such inefficiency, various routing protocols have been proposed to solve unidirectional link problem, which enhance the robustness of the network remarkably. However, the main focus has been on unicast routing. In this paper, we consider a multicast case and put forward an optimized protocol based on MAODV (Multicast Ad Hoc On Demand Distance Vector), which is called MAODV-SUL (Support Unidirectional Links). When a unidirectional link is detected, the broadcasting message mechanism in a limited range is adopted to support fast reconstructions of multicast tree. It not only improves network's connectivity and capacity but also saves nodes' power. The simulation results demonstrate MAODV-SUL robustness against unidirectional links and superiority over conventional MAODV.