Highway multihop broadcast protocols for vehicular networks

IEEE 802.11p Wireless Access in the Vehicular Environment (WAVE) standard is being developed, in order to support Intelligent Transportation System (ITS) applications including safety applications. This includes data exchange between vehicles (V2V), and between vehicles and infrastructure (V2I). Safety applications, e.g., collision and other safety warnings, rely on broadcast communication. Unfortunately, 802.11p does not allow mechanisms such as sending RTS/CTS and acknowledgements for broadcast communication. Therefore, several collisions can be caused by hidden nodes/vehicles. Moreover, the possibility of using the binary exponential back-off technique to reduce congestion is not supported due to the lack of acknowledgements. In this paper, we propose a new 802.11 based Vehicular Multi-hop Broadcast protocol, called Highway Multihop Broadcast (HMB) that addresses the broadcast storm, hidden node, and reliability problems of multi-hop broadcast in VANET. HMB selects the farthest vehicle, with the least speed deviation with respect to the source, to forward and acknowledge broadcast frames. Simulation results show that HMB has a very high success rate in delivering safety messages, and efficient channel utilization when compared with existing broadcast based protocols.