The unique characteristics of vehicular ad hoc network (VANET) such as highly dynamic mobility and constrained mobility pattern along predetermined road have made the existing routing protocols designed for traditional mobile adhoc network (MANET) cannot be directly applied to support the reliability of vehicle-to-vehicle (V2V) communication in VANET. AODV+ protocol was proposed to support the internet connectivity for MANETs by utilizing a gateway to communicate between mobilenetwork and infrastructure network. However, AODV+ only considers that the destination node lies on the infrastructure network (Internet). When a link breaks, reliable transmission from source to destination cannot be maintained. In the present paper, an extension of AODV+ routing protocol for VANETs called M-AODV+ (Modified AODV+) is proposed.
The proposed M-AODV+ routing protocol supports the reliability of vehicle-to-vehicle communication in VANETs by enabling vehicleto- infrastructure (V2I) and infrastructure-to-infrastructure (I2I) communications as alternative communication links among vehicles when single hop or multi-hop communication in the mobile networkis not possible. M-AODV+ consists of three parts: communication channel selection, gateway discovery, and I2I communication routing. The simulation results show that the proposed protocol improves the performance in terms of packet delivery fraction in the given simulation scenarios compared to that of AODV+ routing protocol with a slight loss on the average end-to-end delay.