High Precision Vehicle Positioning: Towards Cooperative Driving Based on VANET

Abstract

High precision vehicle positioning is a crucial component for intelligent transportation systems. Current technologies based on the use of GPS signals have limitations in providing high precision positioning. Recently, dependence on roadside units (RSUs) has been introduced as alternative positioning methodology. Positioning errors are still encountered, however, due to lack of LOS signals among RSUs and vehicles, for dense traffic. This research proposes a GPS-free cooperative positioning method that considers signals from both RSUs as well as neighbor vehicles. A communication channel model in urban environment is developed based on IEEE 802.11p DSRC at 5.9 GHz. The model implements Wireless InSite ray-tracing tool, and is validated using published measurement results of pathloss and received power levels in urban roads. Accuracy is enhanced by estimating time-of-arrival (TOA) and direction-of-arrival (DOA) information of signals from neighbor RSUs and vehicles. Results show that the proposed method provides consistently less errors compared to other methods. In particular, the proposed framework with dependence on only three RSUs is found to improve accuracy by 92% compared to GPS based procedures, and by about 15% with respect to conventional techniques that depend on four RSUs.