Relay of multi-hop safety message based on beaconing in VANET

In Vehicular Ad-hoc Networks (VANETs), active safety messages play a high role in preventing possible accidents. Delivering safety messages to all vehicles and further locations in the network requires reliable, fast multi-hop transmission. As there is no infrastructure support on roads, vehicles should take their own action cooperatively based on a robust MAC mechanism. In this paper, an enhanced protocol utilizing beacon message exchange is presented. Assuming GPS drift in reality, transmission range is divided into smaller segments and nodes in the furthest segment are selected as candidate nodes for relaying. Among candidate nodes, single node which finds the medium free first according to their back off time will be responsible for relaying the packet. Other candidate nodes will behave as back-up nodes. Thus, maximum coverage is reached selecting a group of nodes in the furthest segment and cooperative medium access mechanism is designed among these nodes in order to relay the packet in the first attempt. The protocol is simulated on multi-lane in one direction under dynamic traffic density due to high difference occurred between vehicle speed. Experimental results show that even though beacon messaging leads packet drops due to noise the enhanced protocol performs well in terms of packet reception rate and end-to-end delay metric.