An adaptive routing algorithm for two-tier traffic information system

Intelligent Transportation Systems (ITSs) have attracted much attention recently. One of the most important services for ITSs is to provide real-time traffic information service. To reduce the deployment cost and achieve high service availability, decentralized approaches such as vehicular ad hoc network (VANET)-based or infrastructure-based peer-to-peer (P2P) traffic information systems were proposed. To further improve the success rate and lookup latency of traffic information lookups, a new two-tier traffic information system which integrates low-tier VANET and high-tier P2P overlay has been developed. However, conventional two-tier traffic information system may introduce extra routing overheads since the information lookups are broadcasted over two tier networks and introduce redundant lookup messages. This paper proposes an adaptive routing mechanism in the two-tier traffic information system to improve the efficiency of traffic information lookup. Simulation results demonstrate that the proposed adaptive scheme reduces the lookup latency and overhead while achieving the same lookup success rate compared with the conventional approach.