Measuring Distances with RSSI from Vehicular Short-Range Communications

In vehicular networks many applications and services require the use of vehicle position, which is typically obtained from off-the-shelf Global Positioning Systems (GPS). However, GPS´ position accuracy is low and the GPS receiver relies on line-of-sight signalling from the satellites. For the sake of application consistency, when the GPS position is not received due to signalling failures, vehicular applications need to find a way to obtain their positions or, at least, their distances to other vehicles or road-side units (RSU). In this paper, we propose an architecture based on beaconing vehicular communication and its received signal strength indicator (RSSI) to estimate the distance from the vehicle to the RSU and vice-versa, as base for an ancillary positioning system. To this end, we implemented and deployed a vehicular network testbed in order to collect datasets of RSSI and distances. Thus, we characterized the RSSI behaviour and evaluated our architecture using real environment datasets. In the absence of GPS signalling, the results show that RSSI-based distance estimation provides absolute mean error of ≃16 m for the vehicle and ≃14 m for the RSU. Finally, we compared the solution with the traditional distance measure based on free-space model.