Methods and Systems for Determining the Location of an Electronic Device

• US 20090243932A1
• Filed: 03/31/2008
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Golba LLC
• Original Assignee: Radliofy LLC
• Inventors: Moshfeghi, Mehran
• Granted Patent: US 7,800,541 B2
• Time in Patent Office: Days
• US Class Current: 342/378
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01S 1/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/38 wherein more than one modulation frequency is used
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

Embodiments of the present invention include a method of determining a location of a mobile device. The method comprises transmitting a signal between a plurality of known locations and receiving signal at device of unknown location such as a mobile device. The signal may include multiple tones having different frequencies and resulting in sets of residual phase differences. The location of the mobile device may be determined using the known locations and the frequency and phase differences between the transmitted tones. In one embodiment, OFDM signals may be used between an access point and mobile device, for example, to determine the location of the mobile device.

Claims

1. A method of determining a location of an electronic device, the method comprising:

transmitting one or more signals between a first electronic device at an unknown location and three or more electronic devices at three or more corresponding known locations, wherein the one or more signals each include a plurality of tones having different frequencies;

determining at least one first phase difference between at least two tones having a first frequency difference in the one or more signals accumulated during transmission between the first electronic device and a first electronic device of said three or more electronic devices;

determining at least one second phase difference between at least two tones having a second frequency difference in the one or more signals accumulated during transmission between the first electronic device and a second electronic device of said three or more electronic devices;

determining at least one third phase difference between at least two tones having a third frequency difference in the one or more signals accumulated during transmission between the first electronic device and a third electronic device of said three or more electronic devices; and

determining the location of said first electronic device using said first, second, and third phase differences and said first, second, and third frequency differences.

2. The method of claim 1 further comprising determining a fourth phase difference between at least two tones having a fourth frequency difference in the one or more signals accumulated during transmission between the first electronic device and a fourth electronic device of four or more electronic devices, wherein said determining the location further comprises using the fourth phase difference and the fourth frequency difference.

3. The method of claim 1 wherein the first, second, and third frequency differences are the same.

4. The method of claim 1 wherein the one or more signals comprise orthogonal frequency division multiplexed signals.

5. The method of claim 1 wherein a first signal of the one or more signals comprises first wireless standard and a second signal of the one or more signals comprises a second wireless standard.

6. The method of claim 1 wherein a first signal of the one or more signals is transmitted from the first electronic device of said three or more electronic devices and received by the first electronic device at the unknown location, a second signal of the one or more signals is transmitted from the second electronic device of said three or more electronic devices and received by the first electronic device at the unknown location, and a third signal of the one or more signals is transmitted from the third electronic device of said three or more electronic devices and received by the first electronic device at the unknown location.

7. The method of claim 1 wherein a first signal of the one or more signals is transmitted from the first electronic device at the unknown location and received by the first electronic device of said three or more electronic devices, a second signal of the one or more signals is transmitted from the first electronic device at the unknown location and received by the second electronic device of said three or more electronic devices, a third signal of the one or more signals is transmitted from the first electronic device at the unknown location and received by the third electronic device of said three or more electronic devices.

8. The method of claim 1 wherein the one or more signals is one signal transmitted from the first electronic device at the unknown location and received by each of said three or more electronic devices.

9. The method of claim 1 wherein at least one of said electronic devices comprises a plurality of antennas, and wherein the method comprises:

determining a first phase difference between at least two tones received by a first antenna of said plurality of antennas; and

determining a second phase difference between at least two tones received by a second antenna of said plurality of antennas.

10. The method of claim 1 wherein the first electronic device at the unknown location includes a gyrator, wherein the method further comprises determining a first location of said first electronic device;

storing said first location;

generating movement vector indicating the movement of the first electronic device relative to first location; and

adding the movement vector to the first location to determine a second location.

11. The method of claim 1 further comprising estimating the distance between the first electronic device and at least one of said three or more electronic devices using a transmitted power and received power of said one or more signals.

12. The method of claim 11 further comprising encoding the transmitted power in at least one signal.

13. The method of claim 1 wherein determining the location further comprises:

selecting a first integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and said first electronic device of said three or more electronic devices;

selecting a second integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and said second electronic device of said three or more electronic devices;

selecting a third integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and said third electronic device of said three or more electronic devices;

determining a first distance between the first electronic device and said first electronic device of said three or more electronic devices, a second distance between the first electronic device and said second electronic device of said three or more electronic devices, a third distance between the first electronic device and said third electronic device of said three or more electronic devices using said first, second, and third integers.

14. The method of claim 13 wherein the first, second, and third distances are final distances indicating the location of the first electronic device relative to three of the three or more electronic devices if the first, second, and third distances intersect at a single point.

15. The method of claim 13 further comprising

estimating the first distance between the first electronic device and said first electronic device of said three or more electronic devices using a transmitted power and received power of said one or more signals;

and

determining said first integer based on said estimated distance.

16. The method of claim 1 further comprising:

determining a plurality of received amplitudes for the plurality of tones;

processing one or more of the received amplitudes to determine estimated distances for each tone;

weighting the estimated distances based on received amplitude values; and

determining the location of said first electronic device using said estimated distances.

17. The method of claim 16 wherein processing comprises normalizing a plurality of received amplitudes.

18. The method of claim 16 wherein processing comprises averaging a plurality of received amplitudes and normalizing the received amplitudes to an average amplitude value.

19. The method of claim 16 wherein processing comprises determining a highest and a lowest amplitude value of said received amplitudes and normalizing the received amplitudes to said highest and lowest amplitude values.

20. A method of determining a location of an electronic device, the method comprising:

determining a first distance between a first electronic device having an unknown location and a second electronic device having a known location, determining the first distance comprising;

generating a plurality of tones having a plurality of frequencies;

modulating the tones with a carrier frequency to produce a first signal;

transmitting the first signal between the first electronic device and the second electronic device;

receiving the first signal;

demodulating the first signal to extract the plurality of tones;

extracting the phase of at least a portion of the plurality of tones; and

determining phase differences between tones at different frequencies, each phase difference having a corresponding frequency difference;

determining a second distance between the first electronic device having the unknown location and a third electronic device having a known location, determining the second distance comprising the same method as determining the first distance;

determining a third distance between the first electronic device having the unknown location and a fourth electronic device having a known location, determining the third distance comprising the same method as determining the first distance; and

calculating the first, second, and third distances based on the phase differences and corresponding frequency differences; and

determining the location of said first electronic device based on said first, second, and third distances.

21. The method of claim 20 further comprising:

extracting an amplitude for each of said plurality of tones;

estimating the first, second, and third distances using said extracted amplitudes and a transmitted power value;

selecting a first integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and the second electronic device, a second integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and the third electronic device, and a third integer representing the difference in the integer number of wavelengths of two tones transmitted between the first electronic device and the third electronic device, wherein the integers are selected based on the estimated first, second, and third distances; and

calculating the first, second, and third distances based on the first, second, and third integers.

22. The method of claim 20 further comprising:

determining a fourth distance between the first electronic device having the unknown location and a fifth electronic device having a known location, determining the fourth distance comprising the same method as determining the first distance; and

calculating the fourth distances based on the phase differences and corresponding frequency differences; and

determining the location of said first electronic device based on said first, second, third, and fourth distances.