Partner based broadcasting for multi-hop emergency message dissemination in VANETs

Most safety-related applications targeting at Vehicular Ad-hoc Networks (VANETs) use Vehicle-to-Vehicle (V2V) broadcast method to disseminate safety-related information to all surrounding vehicles. However, most broadcast schemes used the standard 802.11 CSMA/CA technique to avoid forwarding storm which will cause the delay from waiting timeout. This paper develops an efficient protocol in which the selected node will broadcast the emergency message immediately without the waiting time by looking for a partner for every source. Before broadcasting a message, the source selects a neighbor as its partner and adds the selected neighbor´s identifier to the emergency message to tell its neighbors. Upon receiving of a broadcasting message, the partner will rebroadcast the message immediately. Specifically, we choose the partner by cross-layer optimizations and exploit cooperative forwarding mechanism to help the forwarding when the partner fail to transmit the message to increase reliability and real-time. With the realistic simulation studies, the protocol demonstrates better performance than previous contention-based schemes by reducing end-to-end delay and keeping high message reception rate.