With the high demand for vehicular communication, vehicular ad hoc network (VANET) has become a promising technology to enable Intelligent Transportation Systems (ITS) by providing efficient vehicle-to-vehicle (V2V) communications and vehicle-to-RSU (V2R) communications. Yet, due to the high mobility and unreliable channel quality, VANET has unique characteristics which pose many challenging routing issues, such as traffic awareness, line-of-sight (LOS) obstruction, infrastructure utilization. In this paper, we propose GeoTAR, a map-based and traffic-aware routing protocol, which novelly utilizes digital map and Geohash code system to collect traffic information for routing decision and designs an intersection-first restricted forwarding algorithm (IFRF) for packets forwarding with carefully considering buildings as radio obstacles. Moreover, GeoTAR takes the wired channel equipped in the Roadside Units (RSUs) into consideration when calculating the routing path. Simulation-based evaluations of GeoTAR demonstrate that GeoTAR can significantly improve VANET performance in terms of packet delivery ratio (PDR), with a comparable end-to-end delay to other geographic routing protocols.
