Bandwidth-guaranteed QoS multicast routing by multiple paths/trees in ad hoc wireless networks

In this paper, we investigate the issues of QoS multicast routing in ad hoc wireless networks. Due to limited bandwidth of a wireless node, a QoS multicast call could often be blocked if there does not exist a single multicast tree that has the requested bandwidth, even though there is enough bandwidth in the system to support the call. In this paper we propose a multicast routing scheme by using multiple paths or multiple trees to meet the bandwidth requirement of a call. Three multicast routing strategies are studied, SPT (shortest path tree) based multiple-paths (SPTM), least cost tree based multiple-paths (LCTM) and multiple least cost trees (MLCT). The final routing tree(s) can meet the user's QoS requirements such that the delay from the source node to the furthest destination node shall not exceed the bound and the aggregate bandwidth of the paths or trees shall meet the bandwidth requirement of the call. Extensive simulations have been conducted to evaluate the performance. The simulation results show that the new scheme has three major advantages: 1) it greatly reduces the system blockings; 2) multicast routing is in a fully distributed fashion; 3) the proposed routing protocol follows the format of existing on-demand multicast routing protocols for ad hoc networks, which makes it easy to be incorporated into the existing on-demand routing protocols.