Estimation of position using WLAN access point radio propagation characteristics in a WLAN positioning system

• US 9,052,378 B2
• Filed: 04/10/2012
• Issued: 06/09/2015
• 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: Alizadeh-Shabdiz, Farshid, Pahlavan, Kaveh
• Primary Examiner(s): DOAN, KIET M
• Application Number:
  US13/443,482
• Publication Number:
  US 20120196621A1
• Time in Patent Office: 1,155 Days
• Field of Search: 455/416, 455/456.5, 455/456.1, 455/411, 370/252, 370/350, 370/329, 370/330, 370/336, 370/331, 370/338, 370/216, 370/401, 370/340, 370/315
• US Class Current: 1/1
• CPC Class Codes: G01S 11/06 using intensity measurements
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method for estimating position using WLAN access point radio propagation characteristics in a WLAN location based service is provided. A location-based services system has a plurality of Wi-Fi access points in a target area. The Wi-Fi access points are positioned at geographic locations and have signal coverage areas. A method of characterizing at least one of the Wi-Fi access points comprises determining the geographic location of the Wi-Fi access point, dividing the signal coverage area of the Wi-Fi access point into at least one section, and determining radio propagation characteristics for each section. The radio propagation characteristics of each section characterize a radio channel of the Wi-Fi access point, and the characterization can be used in a location algorithm.

Claims

1. A method of characterizing a wireless local area network (WLAN) access point, comprising:

receiving a plurality of positions at which signals transmitted by the WLAN access point have been detected;

estimating a signal coverage area of the WLAN access point based on the plurality of positions at which the signals were detected;

dividing the estimated signal coverage area of the WLAN access point into at least one section;

determining radio propagation characteristics of the WLAN access point for each section of the signal coverage area of the WLAN access point based on at least a radius of the estimated signal coverage area or signal strength at the plurality of positions at which the signals were detected; and

storing the radio propagations characteristics in a reference database of a computing device.

2. The method of claim 1, the dividing the signal coverage area of the WLAN access point into at least one section including dividing the signal coverage area of the WLAN access point into at least two sections, wherein the at least two sections are divided according to at least two radials from the WLAN access point.

3. The method of claim 1, wherein the at least one section is further divided according to at least one distance from the WLAN access point.

4. The method of claim 3, wherein the number of distances is one.

5. The method of claim 1, the dividing the signal coverage area of the WLAN access point into at least one section including dividing the signal coverage area of the WLAN access point into at least two sections, wherein the at least two sections are divided according to at least two radials and at least one distance from the WLAN access point.

6. The method of claim 1, wherein determining the radio propagation characteristics for each section includes determining a signal power-distance gradient for each section.

7. The method of claim 1, further comprising estimating a geographic location of the at least one WLAN access point.

8. The method of claim 1, wherein the receiving the plurality of positions at which signals transmitted by the WLAN access point have been detected includes receiving the transmitted signals.

9. The method of claim 1, further comprising receiving measured power values for the detected signals, wherein the estimating a signal coverage area of the WLAN access point is based only on positions at which signals having a power value above a threshold were detected.

10. The method of claim 1, further comprising:

selecting a number of sections for the WLAN access point, the number of sections including the at least one section, and

wherein the dividing divides the estimated signal coverage area of the WLAN access point into the number of sections.

11. The method of claim 10, wherein the number of sections is selected based on a number of, and a distribution of, the plurality of positions at which the signals were detected.

12. A computing device having software stored therein that when executed is operable to:

receive a plurality of positions at which signals transmitted by a wireless local area network (WLAN) access point have been detected;

estimate a signal coverage area of the WLAN access point based on the plurality of positions at which the signals were detected;

divide the estimated signal coverage area of the WLAN access point into two or more sections;

determine radio propagation characteristics of the WLAN access point for each section based on at least radius of the estimated signal coverage area or signal strength at the plurality of positions at which the signals were detected; and

store the radio propagations characteristics.

13. The computing device of claim 12, wherein the radio propagation characteristics for each section include a signal power-distance gradient for each section.

14. The computing device of claim 13, wherein the software when executed is further operable to:

determine the signal power-distance gradient as a function of the radius of the estimated signal coverage area.

15. The computing device of claim 13, wherein the software when executed is further operable to:

determine the signal power-distance gradient by fitting a line to signal strength samples at the plurality of positions at which the signals were detected.

16. The computing device of claim 12, wherein the two or more sections are defined at least in part by division of the signal coverage area into sectors along two or more radials extending from the WLAN access point.

17. The computing device of claim 12, wherein the two or more sections are defined at least in part by division of the signal coverage area into tiers at one or more distances from the WLAN access point.

18. The computing device of claim 12, wherein the two or more sections are defined at least in part by division of the signal coverage area into sectors along two or more radials extending from the WLAN access point, and by division of the sectors into tiers at one or more distances from the WLAN access point.

19. The computing device of claim 12, wherein the software when executed is further operable to:

estimate a position of a WLAN-enabled device using the stored radio propagation characteristics.

20. The computing device of claim 19, wherein the software that when executed estimates the position of the WLAN-enabled device utilizes a weighted triangulation algorithm, the weighting determined at least in part based on the stored radio propagation characteristics.

21. The computing device of claim 19, wherein the radio propagation characteristics for each section include a signal power-distance gradient for each section, and the software that when executed estimates the position of the WLAN-enabled device utilizes a weighted triangulation algorithm, the weighting determined at least in part based on signal power-distance gradients.

22. A method of characterizing a wireless local area network (WLAN) access point and using the characterized WLAN access point in WLAN based positioning, comprising:

receiving a plurality of positions at which signals transmitted by a wireless local area network (WLAN) access point have been detected;

estimating a signal coverage area of the WLAN access point based on the plurality of positions at which the signals were detected;

dividing the estimated signal coverage area of the WLAN access point into two or more sections;

determining radio propagation characteristics of the WLAN access point for each section;

storing the radio propagations characteristics in a reference database; and

utilizing at least some of the stored radio propagation characteristics of the WLAN access point from the reference database by positioning software executing on a WLAN-enabled device to estimate a position of the WLAN-enabled device, when the WLAN-enabled device is within range of the WLAN access point.

23. The method of claim 22, wherein the determining is based on at least a radius of the estimated signal coverage area or signal strength at the plurality of positions at which the signals were detected, and the radio propagation characteristics for each section include a signal power-distance gradient for each section calculated using the radius of the estimated signal coverage area or signal strength at the plurality of positions at which the signals were detected.