Method for positioning by Wi-Fi signals

• US 8,983,489 B2
• Filed: 04/28/2010
• Issued: 03/17/2015
• Est. Priority Date: 04/30/2009
• Status: Active Grant

• Current Assignee: Pole Star SA
• Original Assignee: Pole Star SA
• Inventors: Prost, Jean-Baptiste, Terrenoir, Stphane, Godefroy, Baptiste
• Primary Examiner(s): Nealon, William
• Application Number:
  US13/318,125
• Publication Number:
  US 20120100870A1
• Time in Patent Office: 1,784 Days
• Field of Search: 4554561- 6
• 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 information for the access points based on their respective identifiers, the geographical information enabling a prediction of power values of the received signals on a meshing of a space;

estimating position information of the terminal within the space, based at least in part on the geographical 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;

retrieving, from a second database (SIG), topographical information corresponding to a zone around the estimated position, or the estimated positioning zone, the second database further defining a space of authorized positions as well as a space of prohibited positions for terminals; and

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

wherein the positioning method is carried out for a plurality of terminals and further comprises;

storing traces of the plurality of terminals in a centralized memory, where a trace of a terminal is defined as a set of identifiers retrieved for estimated positions of the terminal during a particular period; and

optimizing geographical information of the access points, by minimizing on average a cost function over all of the traces of the plurality of terminals.

2. The positioning method according to claim 1, wherein geographical information, of the access points includes zones of uncertainty around respective positions of the access points.

3. The positioning method according to claim 2, wherein

the optimizing geographical information, of the access points

comprises optimizing the positions of the access points within their respective zones of uncertainty.

4. The positioning method according to claim 3, wherein the cost function measures, for each trace, the deviation with respect to the space of the authorized positions for terminals.

5. The positioning method according to claim 4, wherein the deviation thus measured by the cost function depends on a selected travel mode.

6. The positioning method according to claim 1, wherein for each trace of a terminal the date of the trace is recorded in the centralized memory.

7. The positioning method according claim 1, wherein, for each trace of a terminal, measurement of strengths of signals received from the access points are stored.

8. 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 the meshing, and deduces therefrom, for each of the plurality of points, predicted power at each of the plurality of points.

9. The positioning method according to claim 8, wherein the estimating the position of the terminal estimates the position of the terminal by searching, among the plurality of points, for one point that minimizes a second cost function depending on the gap between the predicted power at one point and the powers of the signals received from the access points.

10. The positioning method according to claim 2, wherein the position of the terminal is determined from weighting of the respective 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 detected access points and a decreasing function of the surfaces of the respective zones of uncertainty corresponding to the detected access points.

11. The positioning method according to claim 1, wherein the first database is 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 in the first database.