A Rebroadcasting Approach for Reliable Broadcast Message Dissemination in Urban Environments

Fast and reliable message broadcasting is critical for safety critical applications of VANET due to the urgency and/or significance of the messages for passengers and drivers. For reliable message delivery, a mechanism for checking the reception of message at the neighboring vehicles and retransmitting it if necessary is required. Especially, in urban environments, where the traffic density tends to be high, mechanisms that minimize control message overhead such as beacon are appropriate in order to minimize the message collisions. Furthermore, broadcast delivery is especially difficult at the intersection due to the road side obstacles such buildings, and hence, a mechanism that enables effective and efficient delivery across intersections is required. In this paper, we propose a beaconless reliable and efficient broadcast approach which specifically taking into account the urban streets. The proposed approach checks the message reception of neighboring vehicles implicitly by taking into account the broadcast of message by next vehicle as the acknowledgement. When retransmissions is necessary around the intersections, vehicles located within the intersection area, where the chance of successful signal propagation toward every branch of the intersection is higher due to less signal attenuation caused by road side obstacles, are to do the retransmissions. Simulation results show that the proposed approach can provide better reliability while consume less resources than the existing approaches.