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

• US 7,835,754 B2
• Filed: 05/08/2006
• Issued: 11/16/2010
• 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 N
• Assistant Examiner(s): DOAN, KIET M
• Application Number:
  US11/430,079
• Publication Number:
  US 20070259624A1
• Time in Patent Office: 1,653 Days
• Field of Search: 455/456.3, 455/562.1, 455/440, 455/450, 707/5, 342/450, 370/338, 370/331
• US Class Current: 455/456.1
• 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 without requiring position estimates of the Wi-Fi enabled device, comprising:

the Wi-Fi enabled device receiving signals transmitted by a plurality of Wi-Fi access points in range of the Wi-Fi enabled device, the receiving occurring over time;

the Wi-Fi enabled device measuring an individual amount of time during which the Wi-Fi enabled device continually detects signals transmitted by a corresponding individual Wi-Fi access point of the plurality of Wi-Fi access points;

calculating an average amount of time during which signals transmitted by the individual Wi-Fi access points are detected based on the individual amounts of time signals from the corresponding individual Wi-Fi access points are detected; and

estimating the speed of travel of the Wi-Fi enabled device using the average amount of time signals are detected, 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, further comprising:

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

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

3. The method of claim 2, wherein the signal coverage area of some of the Wi-Fi access points is obtained from a reference database.

4. The method of claim 2, wherein a default value is used as the signal coverage area of some of the Wi-Fi access points.

5. The method of claim 1, wherein the Wi-Fi enabled device consults a database to determine if said received Wi-Fi signals correspond to a known access point, and if not, uses a default value of Wi-Fi coverage for the access point to estimate the speed of travel of the Wi-Fi enabled device.

6. The method of claim 1, wherein the speed of travel of the Wi-Fi enabled device is mapped as zero when the average detection period is above a threshold value.

7. 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, a method for generating a speed of travel of a Wi-Fi enabled device by combining a plurality of speed estimation techniques using received Wi-Fi signals, said method comprising:

the Wi-Fi enabled device receiving signals transmitted by said Wi-Fi access points;

using said received signals to provide a first estimated speed of travel using a first estimation technique;

using said received signals to provide a second estimated speed of travel using a second estimation technique;

using said received signals to provide a third estimated speed of travel using a third estimation technique; and

using the first, second, and third estimated speeds of travel to generate a fourth speed of travel;

wherein said first, second, and third estimation techniques are different techniques to estimate speed of travel.

8. The method of claim 7, further comprising:

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

generating 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.

9. The method of claim 8, further comprising:

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

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

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

10. The method of claim 7, further comprising:

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

11. The method of claim 7, wherein the first estimation technique comprises generating an average detection period during which the Wi-Fi enabled device detects the existence of the signals transmitted by the Wi-Fi access points.

12. The method of claim 7, wherein the second estimation technique comprises calculating an amount of variation between power values, wherein said power values are measured at individual instances in time for each of the signals received by the Wi-Fi enabled device.

13. The method of claim 7, wherein the third estimation technique comprises using a plurality of positions and associated time values of the Wi-Fi enabled device estimated using the geographic locations of the Wi-Fi access points.