On the construction of virtual multicast backbone for wireless ad hoc networks

With the proliferation of portable computing devices and ascending popularity of group-oriented computing, wireless ad hoc network multicasting remains a challenging research subject. While the virtual multicast backbone (VMB) structure is commonly used in current multicast protocols, this paper focuses on the construction of the optimal VMB with the fewest forwarding nodes to decrease overhead and cost, due to the scarce resource in ad hoc networks. Instead of the conventional Steiner tree model, the optimal shared VMB in ad hoc networks is modeled as the minimum Steiner dominating set (MSCDS) in unit-disk graphs (UDG), which is NP-hard. A performance evaluation of flooding for MSCDS is given and a one-hop algorithm is proposed with an approximation ratio of at most 10. To adapt various network scenarios, this paper further presents a fully distributed d-hop algorithm also with a constant approximation ratio, which organizes multicast nodes to form a hierarchical VMB. Based on the hierarchical structure, this paper proposes some approaches to maintain and update VMB, and gives a security framework to exclude malicious nodes from multicast groups. Simulation results show that the proposed algorithms perform very well.