Handshaking vs. instant broadcast in VANET safety message routing

Vehicular ad hoc networks (VANETs) rely on multi-hop communication in order to disseminate information to locations beyond the transmission range. In this paper, the use of handshaking mechanism is evaluated against instant transmission for safety message routing in VANETs for the first time. It is argued that due to the small size of VANET safety message (mean payload size of 100 bytes), handshaking may not be advantageous to avoid hidden node problem and may incur overhead delay. The simplified instant broadcast routing without the use of handshake mechanism is recommended. Theoretical analysis of message propagation delay using instant broadcast routing is shown which can be easily extended for any broadcast method. Two prominent handshake based broadcast routing schemes are implemented in ns-3 along with instant broadcast scheme. The simulation results reveal that instant broadcast effectively lowers the message propagation delay by 100% each hop and guarantees reliable dissemination of safety messages to all endangered vehicles on the road.