Multi-hop Broadcast for Warning in Urban VANETs

Abstract

Traditional directional broadcast protocols cannot efficiently provide data dissemination in urban Vehicular Ad Hoc Networks (VANETs) due to constructions at intersection. To improve dissemination toward all directions and decrease retransmission, in this paper, MBW (Multi-hop Broadcast for Warning) protocol in urban VANETs is proposed. With the MBW protocol, the road is classified into four directions according to the area in which vehicles are, they are east, south, west and north. Relay node at the intersection is decided by following rules: (1) one node records itself is at intersection if it has neighbor nodes from two or more different road direction, and distance between node and neighbor is more than road width. (2) and its ID is the smallest among the nodes at the intersection. Relay nodes at intersections prioritize to forward messages without waiting. On the road, relay nodes are selected according to a waiting time equation, message is broadcasted if waiting time ends, message is propagated in both directions on the road. With relay node selection strategy, The number of relay nodes is decreased, and the number of retransmissions is decreased. Simulation results show that MBW offers better coverage ratio, low delay, low forwarding nodes ratio and lower overhead comparing to exiting broadcasting protocols in urban VANETs.