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US 7,010,290 B2Granted
System and method of determining short range distance between RF equipped devices
AssigneeEricsson Inc.
InventorPaul W. Dent
Life of this patent
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AssigneeEricsson Inc.
InventorPaul W. Dent
Estimating the term…
A first, transmitting, device transmits a digitized data message using a short range radio link followed by digital data representing a digitized acoustic signal, such as a tone. Simultaneously, or with a predetermined time delay, the transmitting device emits an acoustic version of the same signal using an acoustic transducer such as a loudspeaker. A second, receiving, device receives the data message and the digitized acoustic signal via the short range radio link and receives the acoustic version of the signal via a microphone, which converts the acoustic signal to a second digitized version of the acoustic signal. Digital signal processing circuits then correlate the second digitized signal received acoustically with the digitized acoustic signal received over the short range radio link to determine a time difference of arrival. The time difference is corrected for any predetermined delay between the radio and the acoustic signal emissions at the transmitter and predetermined processing delays in the receiver. Once the time delay is determined, the receiving device can determine its distance from the transmitting device using the difference between the speed of sound and the speed of radio propagation.
A method of determining the distance between a portable wireless communication device and an RF equipped Point-of-Sale device based on propagation delay between a pulse code modulation (PCM) RF signal and an acoustic signal that are emitted from the portable wireless communication device and received by the RF equipped Point-of-Sale device, the method comprising:
In a portable wireless communication device, a method of determining the distance between the portable wireless communication device and a RF equipped Point-of-Sale device, the RF equipped Point-of-Sale device capable of emitting a multi-tone acoustic signal and transmitting a pulse code modulation (PCM) radio signal that is a digitized version of the multi-tone acoustic signal, the method comprising:
A portable wireless communication device capable of determining the distance between itself and a RF equipped device wherein the RF equipped Point-of-Sale device emits a multi-tone acoustic signal and transmits a corresponding pulse code modulation (PCM) radio signal in the form of first digital audio samples, the portable wireless communication device comprising:
Dependencies are inferred from the claim text.