METHOD FOR POSITIONING BY WI-FI SIGNALS

• US 20120100870A1
• Filed: 04/28/2010
• Published: 04/26/2012
• Est. Priority Date: 04/30/2009
• Status: Active Grant

• Current Assignee: Pole Star SA
• Original Assignee: Pole Star SA
• Inventors: Prost, Jean-Baptiste, Godefroy, Baptiste, Terrenoir, Stéphane
• Granted Patent: US 8,983,489 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/02529 not involving signal parameters, i.e. only involving identifiers

Abstract

A method for positioning a terminal using signals received from a plurality of access points of at least one wireless telecommunications network is disclosed. According to some aspects, the terminal first retrieves identifiers of the access points from the received signals, then searches in a first database (BDP) for respective geographical position information for the access points. A first estimation of a position of the terminal or a positioning zone of the terminal is obtained from geographical position information of the access points, then topographical information corresponding to the first estimation of the position or the positioning zone is retrieved from a second database (SIG). A second estimation of the position of the terminal is performed using the topographical information thus obtained.

Claims

1. A method for positioning a terminal using signals received from a plurality of access points of at least one wireless telecommunications network, the method comprising:

retrieving identifiers of the access points from the received signals;

searching in a first database (BDP) for geographical position information for the access points based on their respective identifiers;

estimating position information of the terminal based at least in part on the geographical position information of the access points, the estimated position information corresponding to an estimated position of the terminal or information regarding an estimated positioning zone in which the terminal is located;

from a second database (SIG), topographical information corresponding to a zone around the estimated position, or the estimated positioning zone; and

estimating the position of the terminal based on the retrieved topographical information.

2. The positioning method according to claim 1, wherein estimating the position of the terminal comprises weighting, using coefficients obtained from the retrieved topographical information, the estimated position of the terminal and a second position obtained based on satellite positioning, or measurements of signals received from the access points and signal measurements of a satellite positioning system.

3. The positioning method according to claim 1, wherein estimating the position of the terminal comprises:

based on the retrieved topographical information, one of a first positioning method using signals received from the access points, a second positioning method using signals received from a satellite positioning system, and a third hybrid positioning method using both the first and second; and

determining the position of the terminal using the selected method.

4. The positioning method according to claim 3, herein selecting the positioning method further comprises utilizing at least one of time information associated with the terminal and description parameters corresponding to the orbits of the satellites of the positioning system.

5. The positioning method according to claim 3, wherein the second database comprises selection information for selecting the positioning method for a plurality of points of a geographical zone.

6. The positioning method according to claim 4, wherein the second database comprises, for each point of the plurality of points of the geographical zone, the selection information associated with time information.

7. The positioning method according claim 3, wherein if the first positioning method is selected, a first means for implementation of the second positioning method is placed in a standby mode, and if the second positioning method is selected, a second means for implementation of the first positioning method placed in a standby mode.

8. The positioning method according to claim 3, wherein the first positioning method is selected to determine the position of the terminal along a first axis and the second positioning method is selected to determine the position of the terminal along a second axis that is different from the first.

9. The positioning method according to claim 1, wherein the terminal determines, based on the retrieved topographical information, characteristics of the propagation channels between the detected access points and a plurality of points of a geographical zone, and deduces therefrom, for each of the plurality of points, a theoretical power at each of the plurality of points.

10. The positioning method according to claim 9, wherein the second estimating step determines the position of the terminal by searching, among the plurality of points, for one point that minimizes a cost function depending on the gap between the theoretical power at one point and the powers of the signals received from the access points.

11. The positioning method according to claim 1, wherein the first database (BDP) includes, for each access point, geographical position information including its geographical position and data describing a zone of uncertainty around said the geographical position.

12. The positioning method according to claim 1, wherein the position of the terminal is determined from weighting of the respective geographical positions of the access points detected by the terminal using weighting coefficients, the weighting coefficients being obtained based on an increasing function of the transmission powers of the detected access points and a decreasing function of the surfaces of the respective uncertainty zones corresponding to the detected access points.

13. The positioning method according to claim 1, wherein the first database is generated based on a previously received file, wherein the file provides a deployment mailing address for each access point, and wherein each access point is assigned a geographical position from topographical information based on the address stored in the first database.

14. The positioning method according to claim 13, wherein the topographical information corresponding to the address provides a two-dimensional footprint of the building located at that address and the position of the access point is then calculated as the barycenter of the two-dimensional footprint.

15. The positioning method according to claim 13, wherein the topographical information corresponding to the address provides a two-dimensional footprint of the building located at the address and, if the building has plurality of addresses A₁, A₂, . . . , A_K corresponding to respective geographical positions P₁, P₂, . . . , P_K the method further comprising determining a Vorono{umlaut over (l)} diagram of the points located in geographical positions, the geographical position of the access point being calculated as a barycenter of the intersection of the two-dimensional footprint with the Voron{umlaut over (l)} cell of the point associated with the address.

16. The positioning method according to claim 1, wherein the first database can be formed from an initial set of access points, and an access point not belonging to the set can be identified and localized using signals received by at least three access points belonging to the set, the method further comprising storing the identifier and the position of the access point then being in the first database.

17. The positioning method according to claim 1, further comprising, when the first estimate provides a positioning zone of a terminal that is unconnected or has a surface above a certain threshold, the generating an estimation error.

18. The positioning method according to claim 17, further comprising, when an estimation error is generated, searching among the access points taken into account during estimation of the position information for an access point having led to the error to determine an error causing access point;

and removing the error causing access point from the first database.

19. The positioning method according to claim 1, further comprising storing, in a centralized manner, the traces of a plurality of terminals, wherein a trace of a terminal comprises the set of identifiers for points detected in estimating the position information during a particular period.

20. The positioning method according to claim 11, wherein the second database defines a space for authorized positions as well as a space for positions prohibited for the plurality of terminals, the geographical positions of the access points being optimized inside their respective zones of uncertainty, the optimization being done by minimizing on average a cost function over all of the traces, the cost function depending on the deviation of a trace at the authorized positions space.