Estimation of speed of travel using the dynamic signal strength variation of multiple WLAN access points

• US 8,014,788 B2
• Filed: 05/08/2006
• Issued: 09/06/2011
• 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 J.
• Primary Examiner(s): Appiah; Charles
• Assistant Examiner(s): DOAN, KIET M
• Application Number:
  US11/429,862
• Publication Number:
  US 20070258420A1
• Time in Patent Office: 1,947 Days
• Field of Search: 455/456.1, 455/456.3, 455/422.1, 455/456, 455/440, 455/450, 455/67.11, 455/424, 455/456.2, 455/441, 342/451, 701/207, 370/252, 370/338, 370/331, 370/332, 370/328, 370/318
• US Class Current: 455/456.1
• CPC Class Codes: G01S 11/06 using intensity measurements
• 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 without requiring position estimates of the Wi-Fi enabled device, the method comprising:

the Wi-Fi enabled device receiving all signals from detected Wi-Fi access points in range of the Wi-Fi enabled device;

measuring a power value for each of the received signals, the measuring occurring from individual Wi-Fi access points during a window of time;

calculating an amount of variation between the power values measured from the individual Wi-Fi access points during the window of time; and

using the amount of variation of the power values to estimate a speed of travel of the Wi-Fi enabled device so that the speed of travel can be estimated without requiring position estimates 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 at least one of the calculating the amount of variation between the power values and estimating 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 at least one of the Wi-Fi access points is not in a reference database.

6. The method of claim 1, wherein a length of time over which the individual Wi-Fi access points during the window of time are measured varies according to the rate of change of speed of travel of the Wi-Fi enabled device.

7. The method of claim 1, wherein a Fourier Transform is performed to calculate the amount of variation between the power values.

8. The method of claim 1, wherein a standard deviation of power values is used to calculate the amount of variation between the power values.

9. The method of claim 1, wherein the speed of travel of the Wi-Fi enabled device is mapped as zero when the amount of variation between the power values is below a threshold value.

10. The method of claim 1, wherein the amount of time over which the individual Wi-Fi access points during the window of time are measured is about 20 seconds and the power measurements are taken at a rate of about one per second.

11. The method of claim 1, wherein the amount of time over which the individual Wi-Fi access points during the window of time are measured is about 15 seconds and the power measurements are taken at a rate of about one per second.

12. The method of claim 1, wherein the amount of time over which the individual Wi-Fi access points during the window of time are measured is about 10 seconds and the power measurements are taken at a rate of about one per second.

13. The method of claim 1, wherein the amount of time over which the individual Wi-Fi access points during the window of time are measured is about 5 seconds and the power measurements are taken at a rate of about one per second.

14. A method used to estimate a speed of travel of a Wi-Fi enabled device without requiring position estimates of the Wi-Fi enabled device, the method comprising:

the Wi-Fi enabled device receiving all signals from detected Wi-Fi access points in range of the Wi-Fi enabled device;

measuring a power value for each of the received signals, the measuring occurring from individual Wi-Fi access points during a window of time, wherein a length of time over which the individual Wi-Fi access points occur varies according to the speed of travel of the Wi-Fi enabled device;

calculating an amount of variation between the power values measured from the individual Wi-Fi access points during the window of time; and

using the amount of variation of the power values to estimate a speed of travel of the Wi-Fi enabled device so that the speed of travel can be estimated without requiring position estimates of the Wi-Fi enabled device.

15. The method of claim 14, wherein a length of time over which the individual Wi-Fi access points during the window of time are measured decreases as the speed of travel of the Wi-Fi enabled device increases.