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

• US 20070258420A1
• 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 8,014,788 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• 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, the method comprising:

the Wi-Fi enabled device receiving and measuring signal strengths of signals transmitted by a plurality of Wi-Fi access points in range of the Wi-Fi enabled device as received by the Wi-Fi enabled device, the measuring occurring during a window of time;

calculating variations of the signal strengths as received by the Wi-Fi enabled device during the window of time; and

using the signal strength variations to estimate a 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 at least one of the calculating variations of the signal strength 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 unaudited.

6. The method of claim 1, wherein the duration of the window of time varies according to the speed of travel of the Wi-Fi enabled device.

7. The method of claim 6, wherein the duration of the window of time decreases as the speed of travel of the Wi-Fi enabled device increases.

8. The method of claim 1, wherein the duration of the window of time varies according to the rate of change of speed of travel of the Wi-Fi enabled device.

9. The method of claim 1, wherein a Fourier Transform is preformed to calculate signal strength variation.

10. The method of claim 1, wherein a standard deviation of signal strength is used to calculate signal strength variation.

11. The method of claim 1, wherein the speed of travel of the Wi-Fi enabled device is mapped as zero when the variation of signal strength is below a threshold value.

12. The method of claim 1, wherein the window of time is about 20 seconds and the signal strength measurements are taken at a rate of about one per second.