An RFID-based technique for train localization with passive tags

The spatial localization of trains along the railway track is here addressed by using the passive RFID technology at UHF band. The train is equipped with a UHF-RFID reader, and a set of passive tags are distributed along the railway track at assigned known positions. By exploiting the measurement of the phase samples of the signal backscattered from each tag, the reader position with respect to the tags themselves is estimated through an algorithm with a relatively low computational complexity. The algorithm exploits the knowledge of the tag positions and the train speed vector. Based on a number of assumptions, preliminary numerical simulations demonstrated that the proposed technique could be a valid alternative to more expensive systems that are available for train localization, as for example active transponders.