TOPO: Routing in Large Scale Vehicular Networks

A vehicular ad hoc network (VANET) is a high mobility wireless ad hoc network that is targeted to support vehicular safety, traffic monitoring, and other commercial applications. Routing in large scale VANET is an important issue, because road complexity and traffic variety may bring many potential problems that existing routing protocol can not address. In this paper, we introduce a two-phase routing protocol (TOPO) that incorporates map information in routing. The proposed protocol defines an overlay graph with roads of high vehicular density and forwards packet along the pre-calculated path in the overlay. We argue that the proposed TOPO can serve as a framework integrating existing VANET routing protocols. In particular, we adopt modified AODV and GPSR in the access (residential area) to send packets to overlay, while greedy forwarding is used in overlay. We also consider the data diversity in VANETs and design TOPO as an ITS friendly protocol. To validate our design philosophy and the routing protocol, we use real world road layouts in Orlando, and generate vehicular mobility traces following some mobility models. We feed the traces to network simulator and study the routing behavior. Simulation results show the performance and effectiveness of our proposed routing protocols for large scale VANET scenarios.