Abstract:

For the disadvantages of  based on CDMA (Code Division Multiple Access)TDOA (Time Difference Of Arrival) low accuracy for the  indoor positioning technology, we proposed a  indoor ultrasonic positioning system, and described its working principle and analysed  ultrasonic signals. The system that is based on the character of radio frequency and ultrasonic sensors encodes the ultrasonic signal using CDMA technology, so that the destination node can distinguish which beacon signal is sent to the ultrasound, and they combines with the RF signals to achieve TDOA location algorithm, and ultimately does threedimensional positioning. The ultrasonic signal of the three beacons is made simulation and analysis by Matlab/Simulink blocks. Finally, simulation results from the three beacons that send a coded ultrasonic signal can be received and identified at the destination node.

Key words: ultrasonic positioning, code division multiple access（CDMA）, time difference of arrival（TDOA）