An information addition technique for indoor self-localization systems using SS ultrasonic waves

In this paper, we propose an information addition technique for a 3-D indoor positioning system using spread spectrum (SS) ultrasonic waves, and evaluate its effectiveness. The system can position a target with high resolution, noise tolerance, and an ability of implementing CDMA by SS code using a limited number of transmitting channels. An M-sequence is employed as the SS ultrasonic code. Our aim is a positioning system for self-localization of people and robots; the location of a receiver installed on a target can be measured with SS signals from transmitters mounted in the positioning area. To evaluate the effectiveness of the proposed technique, an experiment to measure the distance from transmitter to receiver was conducted with the original hardware used with this technique. In this experiment, 4-bit information in a period of the M-sequence, generated by an 8-bit shift register, was applied. The result showed that the distance from transmitter to receiver and the added information can be detected at the same time. This experiment demonstrated the effectiveness of the information addition technique for SS ultrasonic waves.