Exploiting RFID technology for indoor positioning

Indoor positioning of objects and people has becoming of great importance in the Internet of Things (IoT), in-home automation, and navigation in mall, airports or very large buildings. Position can be geometrically calculated from multiple measurements of the distance between reference points and moving sensors. Distance measurement can be done by measuring the time of flight of an ultrasonic signal traveling from an emitter to receiving sensors. This requires close synchronization between the emitter and the sensors. In this work this synchronization is done using the RFID standard protocol features. RFID tags included in the emitter and sensor circuitry are synchronized each other via the RFID reader interrogation pulse. The system architecture is explained and experimental results on the synchronization accuracy are presented. Moreover, the synchronization uncertainty influence on the positioning performances is discussed. Calculations ensure a mean positioning error below 5 cm in the volume of a typical room.