Patent ID: 8907764

Claim:
A system for determining a location and an identity of a portable device, the system comprising: a plurality of stationary ultrasonic base stations, each ultrasonic base station including a radio frequency (RF) receiver configured to receive timing synchronization information and an ultrasonic transmitter configured to transmit a corresponding ultrasonic location code in a time period based on the received timing synchronization information, each ultrasonic location code representative of a location of the respective ultrasonic base station; a beacon transmitter configured to transmit beacons with the timing synchronization information to the RF receivers in the plurality of stationary ultrasonic base stations; and a plurality of portable devices, each portable device configured to detect the ultrasonic location codes from the ultrasonic base stations, and transmit an output signal including a portable device ID representative of the portable device and the detected location code, wherein each portable device is synchronized to detect the ultrasonic location code in the time period based on the ultrasonic signals received from the ultrasonic base-stations and the timing synchronization information.