Hybrid routing for safety data with intermittent V2I connectivity

Abstract

V2I communications complement V2V safety applications by dealing with emergency situations such as crash scenarios that the V2V program cannot handle or that could be addressed more effectively. However, depending on the deployed infrastructure, we can distinguish between three situations regarding allowed communications: infrastructure-based, infrastructure-less and intermittent infrastructure. We will focus in vehicular networks with an intermittent connectivity, where the unavailability of direct communication with RSUs poses huge problems, especially when vehicles have to send safety-related messages to the infrastructure. In fact, a scattered vehicular infrastructure leads to non-homogeneous coverage, especially in highway scenarios extending over long distances; it is very expensive to set up an infrastructure across the whole road. Our objective is to address the challenges related to safety information forwarding towards the RSU in such networks by enabling vehicles to make an optimal forwarding decision based on contextual information relative to the infrastructure and the neighbourhood. In this work, we present HyRSIC (Hybrid Routing for Safety data with Intermittent V2I Connectivity), a routing approach, combining geographical and topological routing, proposed to deal with data forwarding in intermittent infrastructure-based networks. We conducted an in-depth evaluation from three different perspectives: scalability, reliability and efficiency. The results show that HyRSIC is able to scale quickly and adapt promptly to density and speed variations. Compared to GPSR and its variant ILTS+GPSR, HyRSIC offers the best packet delivery ratio for sparse networks, 12-27% higher, and the lowest End-to-End delivery delay, 25-50% less.