On Supporting Robust Voice Multicasting Over Ad Hoc Wireless Networks

In this paper, we address the problem of voice multicasting in ad hoc wireless networks. The unique characteristics of voice traffic ( viz . small packet size, high packet rate, and soft realtime nature) make conventional multicasting protocols perform quite poorly, hence warranting application-centric approaches in order to increase robustness to packet losses and lower the overhead due to high packet rate. By exploiting the path diversity and the error resilience properties of multiple description coding (MDC), we propose a robust voice multicast routing (RVMR) protocol. Our protocol uses a novel path based Steiner tree heuristic to reduce the number of forwarders in each tree, and constructs two trees in parallel with reduced number of common nodes among them. Moreover, unlike other on-demand multicast protocols, RVMR specifically attempts to reduce the periodic (non on-demand) control traffic. We propose several optimizations for reducing the overhead while transmitting high packet rate voice traffic in ad hoc networks. We extensively evaluate RVMR in the NS-2 simulation framework and show that it out-performs existing single-tree and two-tree multicasting protocols.