Method and apparatus for locating a mobile device

• US 10,247,807 B2
• Filed: 08/25/2017
• Issued: 04/02/2019
• Est. Priority Date: 06/03/2015
• Status: Active Grant

• Current Assignee: Carnegie Mellon University
• Original Assignee: Carnegie Mellon University
• Inventors: Lazik, Patrick, Rajagopal, Niranjini, Shih, Oliver, Rowe, Anthony, Sinopoli, Bruno
• Primary Examiner(s): Mehra, Inder P
• Application Number:
  US15/686,582
• Publication Number:
  US 20170350958A1
• Time in Patent Office: 585 Days
• Field of Search: 701516, 701434, 701468, 701500, 701515, 701514, 367128, 367118, 367129
• CPC Class Codes: G01S 11/16 using difference in transit time between electrical and acoustic signals
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0264 at least one of the systems being a non-radio wave positioning system
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves
• CPC Class Codes: G01S 5/22 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence
• CPC Class Codes: G01S 5/26 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/28 takes precedence
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: H04W 4/30 Services specially adapted for particular environments, situations or purposes

Abstract

A method for locating a mobile device is disclosed. Initially, a set of modulated ultrasound signals and a set of radio signals are separately broadcast from a group of transmitters. The ultrasound signals include at least one symbol configured for pulse compression. After the receipt of a demodulated ultrasound signal from a mobile device, wherein the demodulated ultrasound signal is derived from the modulated ultrasound signals, transmitter identifier and timing information are extracted from the demodulated ultrasound signal. Timing information include, for example, the arrival time of the demodulated ultrasound signal in relation to the start time of its transmission. After the locations of the transmitters have been ascertained from the transmitter identifier information, the location of the mobile device can be determined based on the timing information and the locations of the transmitters.

Claims

1. A method for locating a mobile device, said method comprising:

periodically transmitting radio signals via a transmitter;

utilizing said radio signals to time synchronize a mobile device;

transmitting a modulated ultrasound signal via said transmitter, wherein said modulated ultrasound signal includes at least one symbol configured for pulse compression;

in response to the receipt of a demodulated ultrasound signal sent from said mobile device, wherein said demodulated ultrasound signal is derived from said modulated ultrasound signal,

determining whether or not said demodulated ultrasound signal is originated from a line-of-sight (LOS) source; and

in response to a determination that said demodulated ultrasound signal is not originated from a LOS source, discarding said demodulated ultrasound signal;

otherwise, extracting transmitter identifier and timing information from said demodulated ultrasound signal;

determining a location of said transmitter based on said transmitter identifier information; and

determining a location of said mobile device based on said timing information and said determined location of said transmitter.

2. The method of claim 1, wherein said extracting further includes extracting a signal strength of said demodulated ultrasound signal.

3. The method of claim 1, wherein said determining a location of said transmitter further includes determining said location of said mobile device by looking up said transmitter identifier in a transmitter map.

4. The method of claim 1, wherein said radio signals are Bluetooth signals.

5. The method of claim 1, wherein said radio signals are WiFi signals.

6. A method for locating a mobile device, said method comprising:

periodically transmitting radio signals via a transmitter;

utilizing said radio signals to time synchronize a mobile device;

transmitting a modulated ultrasound signal in a frequency range between 19-24 kHz via said transmitter, wherein said modulated ultrasound signal includes at least one symbol configured for pulse compression;

in response to the receipt of a demodulated ultrasound signal sent from said mobile device, wherein said demodulated ultrasound signal is derived from said modulated ultrasound signal, extracting transmitter identifier and timing information from said demodulated ultrasound signal;

determining a location of said transmitter based on said transmitter identifier information; and

determining a location of said mobile device based on said timing information and said determined location of said transmitter.

7. An apparatus for locating a mobile device, said apparatus comprising:

a radio for transmitting radio signals, and utilizing said radio signals to time synchronize a mobile device;

a speaker for transmitting a modulated, ultrasound signal, wherein said modulated ultrasound signal is formed by modulating an ultrasound signal having at least one symbol configured for pulse compression;

a network interface for receiving a demodulated ultrasound signal sent from said mobile device, wherein said demodulated ultrasound signal is derived from said modulated ultrasound signal; and

a processor for

determining whether or not said demodulated ultrasound signal is originated from a line-of-sight (LOS) source, and discarding said demodulated ultrasound signal, in response to a determination that said demodulated ultrasound signal is not originated from a LOS source;

extracting transmitter identifier and timing information from said demodulated ultrasound signal;

determining a location of said transmitter based on said transmitter identifier information; and

determining a location of said mobile device based on said timing information and said determined location of said transmitter.

8. The apparatus of claim 7, wherein said speaker includes a horn having a tapered acoustic wave guide and a base that provides an airtight seal with said speaker.

9. The apparatus of claim 7, wherein said transmitting further includes transmitting said modulated ultrasound signal in a frequency range between 19-24 kHz via said transmitter.

10. The apparatus of claim 7, wherein said extracting further includes extracting a signal strength of said demodulated ultrasound signal.

11. The apparatus of claim 7, wherein said determining a location of said transmitter is performed by looking up said transmitter identifier in a transmitter map.

12. The apparatus of claim 7, wherein said radio signals are Bluetooth signals.

13. The apparatus of claim 7, wherein said radio signals are WiFi signals.