A Directional Broadcast Protocol for Emergency Message Exchange in Inter-Vehicle Communications

Broadcast is an effective approach for safety-related information exchange to achieve cooperative driving in vehicular ad hoc network (VANET). However, it suffers from several fundamental challenges such as message redundancy, link unreliability, hidden terminal and broadcast storm, etc., which degrade the efficiency of the network greatly. To address these issues, this paper proposes a position based multi-hop broadcast protocol (PMBP) for emergency message dissemination in inter-vehicle communications. By adopting a cross-layer approach considering both the MAC and Network layers in the proposed scheme, the candidate vehicle for forwarding an emergency message is selected according to its distance from the source vehicle in the message propagation direction. Analysis and simulation results show that PMBP can not only quickly deliver emergency messages, but also reduce broadcast message redundancy significantly.