Estimation of speed and direction of travel in a WLAN positioning system

• US 20070259624A1
• Filed: 05/08/2006
• Published: 11/08/2007
• Est. Priority Date: 05/08/2006
• Status: Active Grant

• Current Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Original Assignee: Skyhook Wireless Incorporated (Liberty Broadband Corp.)
• Inventors: Pahlavan, Kaveh, Alizadeh-Shabdiz, Farshid, Morgan, Edward
• Granted Patent: US 7,835,754 B2
• Time in Patent Office: Days
• US Class Current: 455/67.110
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/027 using movement velocity, acceleration information
• CPC Class Codes: H04W 64/006 with additional information processing, e.g. for direction or speed determination

Abstract

A method for estimating the speed and bearing of a Wi-Fi enabled device using WLAN radio signals in a WLAN based location service is provided. A method used to estimate a speed of travel of a Wi-Fi enabled device comprises the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device, and using the signals to estimate the speed of and/or direction of travel of the Wi-Fi enabled device.

Claims

1. A method used to estimate a speed of travel of a Wi-Fi enabled device, comprising:

the Wi-Fi enabled device receiving signals transmitted by Wi-Fi access points in range of the Wi-Fi enabled device; and

using the signals to estimate the speed of travel of the Wi-Fi enabled device.

2. The method of claim 1, wherein the Wi-Fi enabled device communicates with at least one of the Wi-Fi access points to cause the Wi-Fi access point to transmit signals.

3. The method of claim 1, wherein the estimation of the speed of travel of the Wi-Fi enabled device is performed by the Wi-Fi enabled device.

4. The method of claim 1, further comprising using the estimated speed of travel to estimate a subsequent position of the Wi-Fi enabled device.

5. The method of claim 1, wherein a geographic location of at least one of the Wi-Fi access points is contained in a reference database accessible by the Wi-Fi enabled device.

6. The method of claim 1, wherein at least one of the Wi-Fi access points is unaudited.

7. The method of claim 1, further comprising:

the Wi-Fi enabled device measuring an individual observation period for each of the Wi-Fi access points during which the Wi-Fi enabled device is receiving the signal transmitted by the individual Wi-Fi access point, the measuring occurring during a window of time;

calculating an average observation period based on the individual observation periods; and

estimating the speed of travel of the Wi-Fi enabled device using the average observation period.

8. The method of claim 7, further comprising:

obtaining a signal coverage area corresponding to each of the Wi-Fi access points; and

when calculating the average observation period, weighting the individual observation periods for each of the Wi-Fi access points according to their corresponding signal coverage area.

9. The method of claim 8, wherein the signal coverage area of some of the Wi-Fi access points is obtained from a reference database.

10. The method of claim 8, wherein a default value is used as the signal coverage area of some of the Wi-Fi access points.

11. The method of claim 7, wherein at least one of the Wi-Fi access points is unaudited.

12. The method of claim 7, wherein the speed of travel of the Wi-Fi enabled device is mapped as zero when the average observation period is above a threshold value.

13. The method of claim 12, wherein the threshold value is about 8 seconds.

14. The method of claim 7, wherein the window of time is about 21 seconds.

15. In a location-based services system having a plurality of Wi-Fi access points in a target area, the Wi-Fi access points being positioned at geographic locations, the method comprising:

estimating a first speed of travel of a Wi-Fi enabled device using a calculated average observation period during which the Wi-Fi enabled device is receiving signals transmitted by the Wi-Fi access points;

estimating a second speed of travel of the Wi-Fi enabled device using calculated variations of signal strengths transmitted by the Wi-Fi access points as received by the Wi-Fi enabled device;

estimating a third speed of travel of the Wi-Fi enabled device using a plurality of estimated positions and associated time values of the Wi-Fi enabled device estimated using the geographic locations of the Wi-Fi access points; and

calculating a fourth speed of travel of the Wi-Fi enabled device based on the first, second, and third estimated speeds of travel.

16. The method of claim 15, further comprising:

estimating a first, a second, and a third coefficient; and

calculating the fourth speed of travel of the Wi-Fi enabled device based on weighting the first, second, and third estimated speeds of travel with the first, second, and third coefficients, respectively.

17. The method of claim 16, further comprising:

measuring an actual speed of travel of the Wi-Fi enabled device;

calculating an error of speed estimation based on the actual speed and the fourth speed;

determining values for the first, second, and third coefficients to minimize the error of speed estimation.

18. The method of claim 15, further comprising:

determining that the Wi-Fi enabled device is stationary if the calculated fourth speed of travel is below a threshold.