Method for locating mobile devices in a common frame of reference

Patent metadata

Field	Value
Publication number	US-10356556-B2
Application number	US-201816150555-A
Country	US
Kind code	B2
Filing date	Oct 3, 2018
Priority date	Oct 6, 2017
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

In a method for locating mobile devices, a trajectory (T 1 , T 2 ) is reconstructed modelling a movement made by each mobile device during which the mobile device carries out measurements of an indicator linked to the distance separating it from access terminals (B 1 -B 5 ) to a communication network. From these measurements, the locations of the terminals are calculated in a frame of reference linked to each mobile device. A procrustean analysis is then performed to determine, for each mobile device, a geometric transformation that transforms the locations of the terminals in the frame of reference linked to the mobile device into locations transformed in a common frame of reference. From this determination, the location of each terminal transformed in the common frame of reference is superimposed with a location of the terminal in the common frame of reference. Finally, the corresponding geometric transformation is applied to the trajectory of each mobile device.

First claim

The invention claimed is:

1. A method for locating mobile devices, including the following steps:
for each mobile device, reconstructing a trajectory modelling a movement made by the mobile device during which the mobile device carries out measurements of an indicator related to the distance separating it from access terminals to a communication network;
for each mobile device, calculating, from the measurements carried out by the mobile device, locations of the access terminals in a frame of reference associated to the mobile device;
determining, for each mobile device, a geometric transformation that transforms the locations of the access terminals in the frame of reference associated to the mobile device into locations transformed in a common frame of reference, said determining being carried out so as to superimpose according to a superimposition validity metric, for each access terminal, the locations of the access terminal transformed in the common frame of reference with a location of the access terminal in the common frame of reference;
for each mobile device, modifying the trajectory of the mobile device by applying the corresponding geometric transformation.

2. The method according to claim 1 , wherein the common frame of reference is one of the frames of reference associated to the mobile devices.

3. The method according to claim 1 , wherein the step of determining, for each mobile device, a geometric transformation is preceded by the following steps:
selecting a reference frame of reference among the frames of reference associated to the mobile devices;
determining, for each mobile device, a first geometric transformation that transforms the locations of the access terminals in the frame of reference associated to the mobile device into locations transformed in the reference frame of reference, said determination being carried out so as to superimpose according to the superimposition validity metric, for each access terminal, the locations of the access terminal transformed in the reference frame of reference with the location of the access terminal in the reference frame of reference;
for each access terminal, determining the location of the access terminal in the common frame of reference as a function of the locations transformed in the reference frame of reference.

4. The method according to claim 3 , wherein, for each access terminal, the location of the access terminal in the common frame of reference is determined by the calculation of a weighted average or the median of the locations transformed in the reference frame of reference.

5. The method according to claim 4 , wherein the weighting applied to each of the locations transformed in the reference frame of reference in the calculation of the weighted average is an uncertainty concerning the corresponding location in the frame of reference associated to the mobile device.

6. The method according to claim 1 , wherein modifying, for each mobile device, the trajectory of the mobile device includes chopping the trajectory into successive sections each constituted of a number of points identical to the number of access terminals, and the application of the corresponding geometric transformation to each of the sections.

7. The method according to claim 1 , wherein reconstructing the trajectory followed by the mobile device includes a pedestrian dead reckoning implementing a detection of steps and change of walking direction during the movement.

8. The method according to claim 1 , wherein the superimposition validity metric is an indicator representative of the distance, for each access terminal, between each of the locations transformed in the reference frame of reference and the location of the access terminal in the reference frame of reference.

9. The method according to claim 1 , wherein determining, for each mobile device, the geometric transformation is carried out by a procrustean analysis.

10. The method according to claim 1 , further including a step of locating, in the reference frame of reference, measurements of a received signal strength indicator carried out by the mobile devices during their movements, and a step of interpolating said measurements to carry out a mapping of the received signal strength.

11. A non-transitory computer program including instructions which, when the program is executed on computer, lead said computer to implement the determining and modifying steps of the method according to claim 1 .

12. A data processing device including a processor configured to implement the determining and modifying steps of the method according to claim 1 .

Assignees

• Commissariat Energie Atomique
• Comissariat A Lenergie Atomique Et Aux Energies Alternatives

Inventors

• Pereira Da Silva Alex
• Leirens Sylvain

Classifications

• G01S5/02525

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• G01C21/206

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• G01C22/006

  Pedometers · CPC title

• H04W4/023 Primary

  using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds · CPC title

• H04W4/029

  Location-based management or tracking services · CPC title