Abstract:

For the urgent needs of indoor positioning technology and the platform,we proposed a based  ultrasonic indoor three-dimensional positioning system,and described its working principle and the analyzed  ultrasonic signals.Based on the character of radio frequency and ultrasonic sensors the system encodes the ultrasonic signal using CDMA（Code Division Multiple Access） technology,so that the destination node can distinguish each beacon signal sent to the ultrasound,and combines with the RF signal to achieve TDOA（Time Difference Of Arrival） location algorithm,and ultimately does three-dimensional positioning.Experimental  shown that a three-dimensio
nal coordinate system is built by a beacon for the origin and the other two beacons placed on the X axis and the Y axis,which can simplify the triangular positioning algorithm and achieve high precision three-dimensional positioning.

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