A system for determining a location and an identity of a portable device, the system comprising: means for transmitting timing synchronization information including a plurality of RF transceivers coupled to a backbone network and a time server generating the timing synchronization information; wherein each of the plurality of RF transceivers periodically transmits a request to the time server to receive the timing synchronization information; a plurality of stationary ultrasonic base stations, each ultrasonic base station configured to receive the timing synchronization information and 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; and a plurality of portable devices, each portable device configured to 1) receive the timing synchronization information, 2) detect the ultrasonic location codes from the ultrasonic base stations and 3) 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 received timing synchronization information. view more

A system for determining a location and an identity of a portable device, the system comprising: means for transmitting timing synchronization information; a plurality of stationary ultrasonic base stations, each ultrasonic base station configured to receive the timing synchronization information and to transmit an ultrasonic signal including 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; and a plurality of portable devices, each portable device including a corresponding ultrasonic detector and being configured to 1) receive the timing synchronization information, 2) detect the ultrasonic location codes from the ultrasonic signals transmitted by the ultrasonic base stations and 3) transmit an output signal including a portable device ID representative of the portable device and the detected location code, wherein each of the portable devices activates the corresponding ultrasonic detector concurrently with a time that each of the plurality of ultrasonic base stations transmits the corresponding ultrasonic location code of the ultrasonic base station, based on the received timing synchronization information. view more

A system for determining a location and an identity of a portable device, the system comprising: means for transmitting timing synchronization information; a plurality of stationary ultrasonic base stations, each ultrasonic base station configured to receive the timing synchronization information and 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; and a plurality of portable devices, each portable device configured to 1) receive the timing synchronization information, 2) detect the ultrasonic location codes from the ultrasonic base stations and 3) 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 received timing synchronization information, and wherein multiple ultrasonic base stations of the plurality of stationary ultrasonic base stations concurrently transmit the respective ultrasonic location codes of the multiple ultrasonic base stations. view more

An ultrasonic base station, comprising: a radio frequency (RF) receiver, coupled to a time server via a backbone network and configured to receive timing synchronization information from the time server via the backbone network; and an ultrasonic transmitter configured to transmit an ultrasonic location code in a time period based on the received timing synchronization information, the ultrasonic location code representative of a location of the ultrasonic base station, wherein the ultrasonic base station periodically transmits a request to the time server, via the backbone network, to receive the timing synchronization information. view more

The system according to claim 1, wherein each of the plurality of portable devices includes an ultrasonic receiver configured to receive ultrasonic signals containing the ultrasonic location codes and is configured to derive the timing synchronization information from the received ultrasonic signals. view more

The system according to claim 7, wherein the ultrasonic detector of each of the plurality of portable devices is configured to derive the timing synchronization information from the detected ultrasonic signals.

The system according to claim 8, wherein each of the plurality of portable devices includes an ultrasonic receiver configured to receive ultrasonic signals containing the ultrasonic location codes and is configured to derive the timing synchronization information from the received ultrasonic signals. view more

An ultrasonic base station, comprising: a radio frequency (RF) receiver configured to receive timing synchronization information; and an ultrasonic transmitter configured to transmit an ultrasonic location code in a time period based on the received timing synchronization information, the ultrasonic location code representative of a location of the ultrasonic base station, wherein the RF receiver is configured to receive beacons in predetermined time slots, the beacons including the timing synchronization information and respective time delay information relative to a unified time of origin. view more