Infrared-based vehicular positioning with the automatic radiation-strength control

Infrared dedicated short-range communication (IR-DSRC) has been used in single-lane vehicle-to-roadside applications, and is challenged for its application in multi-lane-free-flow vehicle-to-vehicle (V2V) conditions. However, based on IR positioning technology, the IR-DSRC is expected to be useful and valuable under V2V conditions for several intelligent-transportation-system applications. In the previous studies, a three-dimensional IR positioning system was developed to position a preceding vehicle. However, the positioning performance degrades as the longitudinal or the lateral distance between vehicles increases because the resolution of the received signal is deteriorated for weak signals. In this study, onboard units (OBUs) with wide radiation-pattern designs and automatic radiation-strength control are realised to provide stable signal strength for positioning, and the non-ideality of the IR positioning system is compensated by the calibrating procedures as well. A two-vehicle trial is performed, in which the positioning OBU is installed on the most front of the following vehicle to reduce the scattering effect of the vehicle body. The experimental result demonstrates that the positioning performance is greatly improved after aforementioned improvements.