Multi-rate interference-sensitive and conflict-aware multicast in wireless ad hoc networks

The broadcast nature of the wireless medium makes multicast communication subject to various challenges, especially the unreliability due to the interference [2] and the impact of the transmission data rate choice on the conflicts between communicating users. In fact, a fundamental trade-off exists between communication speed (transmission data rate) and communication range. Actually, the effect of interference is more important when the communication speed decreases, i.e. when communication range increases. In this paper, we propose a multiple rate multicast scheme that is applied to capture the effect of transmission conflicts on the wireless multicast throughput. This work exploits the diversity between users to provide an accurate and efficient method that enables each multicast transmitter, i.e. forwarder or sender, to select the data rates to use to serve its interested neighbours. The choice of the set of data rates, i.e. the choice of multi-rate multicast scheme, should be conflict sensitive in order to guarantee high multicast throughput in multi-rate multi-hop MANET's. We start by introducing two new concepts: The Transmission data Rate based Interference graph (TRIGraph) and Concurrent Multi-rate Multicast Transmitter set (CMMS). Then, we describe the use of these concepts to characterize the interference conflicts caused by multi-rate multicast transmissions. Unlike all the existing conflict graphs, TRIGraph and CMMS are not only used to model interference conflicts, but they are also used to choose the multicast data rates that reduce the effect of such network inconsistency on the system performance.