Patent ID: 7764574

Claim:
A method for operating a mobile device positioning system, wherein a positioning system comprises a plurality of ultrasonic signal transmitters, the method comprising: assigning an identification number to each of the plurality of ultrasonic signal transmitters; and transmitting an ultrasonic signal from each of the plurality of ultrasonic signal transmitters in a predetermined order of the plurality of ultrasonic signal transmitters for transmitting the ultrasonic signals, in order to allow the mobile device to compute a distance between the mobile device and each of the plurality of ultrasonic signal transmitters based on the ultrasonic signal and to determine the mobile device's position using the distance between the mobile device and each of the plurality of ultrasonic signal transmitters, wherein each of the plurality of ultrasonic signal transmitters transmits the ultrasonic signal with a time delay after a synchronization signal, wherein the delay time for each of the plurality of ultrasonic signal transmitters is predetermined according to the predetermined order.