A Multihop Broadcast Mechanism for Emergency Messages Dissemination in VANETs

In Vehicular Ad Hoc Networks (VANETs), using multihop broadcast to achieve fast and reliable dissemination of event-driven emergency messages among vehicles has positive significance. Most existing solutions make relay selection by either senders or receivers. However, the former would fall into invalidation due to the unstable links, while the latter would generate extra delay. In this paper, we propose a new mechanism named MBM-EMD (i.e., multihop broadcast mechanism for emergency messages dissemination) to solve these problems. Our contributions are two-fold. i) We integrate multiple influencing factors such as vehicle density, relative movement, and channel quality into a new metric named ETGPH (i.e., the expected transmission gain per hop), and use it to select the optimal relays. ii) After acquiring the candidate set for further rebroadcast, the current sender firstly appoints an optimal relay from it to rebroadcast immediately. Other candidates will assist in forwarding according to our rules if this relay fails. The simulation results demonstrate the feasibility and effectiveness of the proposed solution.