Estimation of Position Using WLAN Access Point Radio Propagation Characteristics in a WLAN Positioning System

• US 20110164522A1
• Filed: 03/14/2011
• Published: 07/07/2011
• 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
• Granted Patent: US 8,155,673 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• 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 WLAN access point, so that the characterization may be used later to effectively weigh signals transmitted by said WLAN access point when performing a location estimation, the method of characterization comprising:

measuring a plurality of power values for signals transmitted by at least one WLAN access point, each power value being measured at a position relative to the WLAN access point;

estimating a signal coverage area of the WLAN access point based on the measured plurality of power values;

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

assigning a weight to each section of the WLAN access point based on at least one of the estimated signal coverage area and the plurality of power values.

2. The method of claim 1, further comprising 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, further comprising 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, further comprising determining radio propagation characteristics for each section.

7. The method of claim 6, wherein the radio propagation characteristics include a signal power-distance gradient.

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

9. A system for characterizing a WLAN access point, so that the characterization may be used later to effectively weigh signals transmitted by said WLAN access point when performing a location estimation, the system of characterization comprising:

a computer readable information storage system;

a computer readable medium comprising instructions that when executed cause a computer system to;

receive a plurality of measured power values for signals transmitted by at least one WLAN access point, each power value being measured at a position relative to the WLAN access point;

estimate a signal coverage area of the WLAN access point based on the measured plurality of power values;

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

assign a weight to each section of the WLAN access point based on at least one of the estimated signal coverage area and the plurality of power values; and

store the weight assigned to each section of the WLAN access point in the computer readable information storage system.

10. The system of claim 9, the computer readable medium further comprising instructions that when executed cause the computer system to divide 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.

11. The system of claim 9, wherein the instructions cause the computer system to further divide the at least one section according to at least one distance from the WLAN access point.

12. The system of claim 11, wherein the number of distances is one.

13. The system of claim 9, the computer readable medium further comprising instructions that when executed cause the computer system to divide 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.

14. The system of claim 9, the computer readable medium further comprising instructions that when executed cause the computer system to determining radio propagation characteristics for each section.

15. The system of claim 14, wherein the radio propagation characteristics include a signal power-distance gradient.

16. The system of claim 9, the computer readable medium further comprising instructions that when executed cause the computer system to receive an estimated geographic location of at least one WLAN access point.