Adaptive Contention Window Scheme to Improve Multi-Hop Broadcast in VANETs

Most VANET safety applications use multi-hop broadcast communications to disseminate safety information as far as needed in the zone of relevance. Recently, many multi-hop broadcast forwarder selection schemes have been proposed. Their aim is to reduce the number of forwarders by selecting a subset of nodes in the zone of relevance that forward the messages to cover the entire zone as fast as possible. In this paper, we propose a density-distance based multi-hop broadcast scheme to address the problems of (i) redundant broadcasts particularly in dense network and (ii) the high latency in sparse networks. We present a solution where both the distance and the network density are considered in calculating the waiting time before deciding whether to rebroadcast received messages or not. Simulation results show that our scheme achieves better performance in terms of number of rebroadcasts and dissemination delay compared to existing solutions.