High Accuracy 3D Indoor Positioning Using Broadband Ultrasonic Signals

In this paper we propose a high accuracy indoor positioning system based on broadband ultrasonic signals and time of arrival (ToA) measurements. Using low cost transducers we were able to use acoustic chirps of between 20 and 45KHz as pulse signals. This overcomes most of the problems faced by the narrow band signals usually used with common piezo-ultrasonic transducers, which include poor resolution, low environment noise immunity, short range and low robustness to the Doppler effect. Using synchronized ultrasonic anchor nodes and time division multiplexing to share the medium, we build a GPS-like system for indoor pervasive applications. A set of experiments were performed to evaluate the proposed system. Very stable 3D position estimates were obtained (absolute standard deviation less than 2.3cm) and a position refresh rate of 350ms was achieved.