Accurate Indoor Positioning System Using Near-Ultrasonic Sound from a Smartphone

This paper describes new concepts and techniques for an indoor positioning system that uses near-ultrasonic sound from a smartphone. The indoor positioning system can be used in many practical applications, for example, in detecting the location of moving objects, such as a person or a wheelchair, and navigation within a wide indoor area. Indoor positioning systems seem to require a higher positioning accuracy compared with systems for use in outdoor areas. The authors have previously proposed a solution for indoor positioning using ultrasonic sensors. However, these suffer from a shortcoming in that users have to possess a special ultrasonic transmitter. The system proposed here does not need such a transmitter, because a smartphone is used as the sound source. Smartphones are already widely used, so the proposed system seems to be easy to introduce for practical use. The sound transmitted from the smartphone has been investigated and confirmed, as has the validity of the developed receiving unit which makes use of the timer count values of a microcomputer, which gives an indication of the timing of the detection of sound from the smartphone. Positioning tests for static and moving objects have been carried out in both quiet and noisy environments. It has been verified that the positioning accuracy is sufficient for navigation for visually impaired persons and for other applications.