Method and apparatus for determining the location of a mobile object

• US 8,102,314 B2
• Filed: 12/12/2006
• Issued: 01/24/2012
• Est. Priority Date: 03/31/2006
• Status: Expired due to Fees

• Current Assignee: Unify GmbH & Co. KG (Atos SE)
• Original Assignee: Unify GmbH & Co. KG (Atos SE)
• Inventors: Bamberger, Joachim, Parodi, Bruno Betoni, Horn, Joachim, Lenz, Henning, Szabo, Andrei
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): MCGUE, FRANK J
• Application Number:
  US11/991,588
• Publication Number:
  US 20100103048A1
• Time in Patent Office: 1,869 Days
• Field of Search: 342/451
• US Class Current: 342/451
• CPC Class Codes: G01S 5/02524 Creating or updating the radio-map
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The invention relates to a position-finding method for determing the location of a mobile object. The features, for example received field strengths, of a plurality of base stations are measured, and the object position is located from these features, using a reference map. During an initialization process, a reference map is created which comprises a multiplicity of positions and the associated feature-dependent values. During use of the method, a plurality of position-finding processes are carried out, by means of each of which a measured feature-dependent value and from this, a located position of the object, are determined using the predetermined reference map. The predetermined reference map is in each case updated for at least some of the positions found, during which updates, the feature-dependent values are each corrected by a correction term at the support points of the reference map in a predetermined area surrounding an object position.

Claims

1. A method for a computer-aided localization of a mobile object aided by a feature-based position-finding method where features of a plurality of base stations are measured, and a position of the object is located from the features using a reference map, the feature of a base station characterizing a field emitted by the base station at the object or a field emitted by the object at the base station, comprising:

predetermining, during initialization of the method, a reference map by calculating the reference map using a wave propagation model, the reference map comprising a multiplicity of support points, which are each represented by a position and a feature-dependent value assigned to the position;

carrying-out a plurality of position-finding processes during use of the method wherein a measured feature-dependent value and from the measured feature-dependent value a located position of the object are determined via the feature-based position-finding method using the predetermined reference map calculated using the wave propagation model; and

carrying-out, in each case, for at least some of locations, an update of the predetermined reference map where the feature-dependent values are each corrected by a correction term at the support points of the reference map in a predetermined area surrounding an object position, the correction term depending on a difference between the measured feature-dependent value for the respective location and the feature-dependent value at a support point in the predetermined surrounding area; and

wherein the features of the plurality of base stations are radio signal strengths of the base stations and the radio signal strengths are measured by the base stations such that each of the base stations self measures the radio signal strength of that base station and wherein the self measurements are the only source of measurements used to determine the reference map during the initialization of the method, the reference map being a field-strength map.

2. The method as claimed in claim 1, wherein the object position is previously known or is a position located via the respective position-finding process.

3. The method as claimed in claim 2, wherein the step of up-dating the predetermined reference map is carried out at a time of the respective position-finding process or after a predetermined number of position-finding processes has been carried out.

4. The method of claim 1 wherein the correction term depends on a Gaussian function and the predetermined area surrounding the object position depends on a standard deviation of the Gaussian function.

5. The method of claim 3 wherein the wave propagation model is a multi wall model propagation model, a dominant path model propagation model, or a radial propagation model.

6. The method of claim 4 wherein the predetermined surrounding area being formed by a shape being formed about a center of the Gaussian function that has a width or radius greater than or equal to the standard deviation and wherein the standard deviation of the Gaussian function depends on spacing between the support points on the reference map.

7. The method of claim 1 wherein parameters of the wave propagation model are determined at least partially by a self-measurement by the base stations.

8. The method as claimed in claim 7, wherein each of the plurality of position-finding processes is carried out with the aid of a fingerprinting method and/or with the aid of a probabilistic method.

9. The method as claimed in claim 8, wherein a size of the correction term decreases in magnitude with increasing distance from the object position.

10. The method as claimed in claim 9, wherein the correction term depends on a Gaussian function with a center of the function being the object position.

11. The method as claimed in claim 10, wherein the predetermined area surrounding the object position depends on a standard deviation of the Gaussian function.

12. The method as claimed in claim 11, wherein the predetermined surrounding area is formed by a circle about the center of the Gaussian function having a radius which is greater than or equal to the standard deviation.

13. A method for a computer-aided localization of a mobile object aided by a feature-based position-finding method where features of a plurality of base stations are measured, and a position of the object is located from the features using a reference map, the feature of a base station characterizing a field emitted by the base station at the object or a field emitted by the object at the base station, comprising:

predetermining, during initialization of the method, a reference map comprising a multiplicity of support points, which are each represented by a position and a feature-dependent value assigned to the position;

carrying-out a plurality of position-finding processes during use of the method wherein a measured feature-dependent value and from the measured feature-dependent value a located position of the object are determined via the feature-based position-finding method using the predetermined reference map; and

carrying-out, in each case, for at least some locations, an update of the predetermined reference map where the feature-dependent values are each corrected by a correction term at the support points of the reference map in a predetermined area surrounding an object position, the correction term depending on a difference between the measured feature-dependent value for a respective location and the feature-dependent value at a support point in the predetermined surrounding area; and

wherein the object position is previously known or is the position located via the respective position-finding process;

wherein the step of up-dating the predetermined reference map is carried out at the time of the respective position-finding process or after a predetermined number of position-finding processes has been carried out;

wherein the predetermined reference map is computed via a wave propagation model;

wherein the wave propagation model is an multi wall model propagation model or a dominant path model propagation model;

wherein parameters of the propagation model are determined at least partially by a self-measurement by the base stations;

wherein each of the plurality of position-finding processes is carried out with the aid of a fingerprinting method and/or with the aid of a probabilistic method;

wherein a size of the correction term decreases in magnitude with increasing distance from the object position;

wherein the correction term depends on a Gaussian function with a center of the Gaussian function being in the object position;

wherein the predetermined area surrounding the object position depends on a standard deviation of the Gaussian function;

wherein the predetermined surrounding area is formed by a circle about the center of the Gaussian function having a radius which is greater than or equal to the standard deviation; and

wherein the standard deviation of the Gaussian function depends on a spacing of the support points on the reference map and lies between the support-point spacing and five times the support-point spacing.

14. The method as claimed in claim 13, wherein the Gaussian function is approximated by a function that decreases to zero with increasing distance from the center.

15. The method as claimed in claim 14, wherein the measured feature-dependent value is a field-strength vector, measured at the object or at the base stations at a time of the position-finding process and where the predetermined reference map is a location feature map in which the feature-dependent values are feature vectors for the positions of the support points, a feature vector comprising as entries the features of the base stations for a corresponding position.

16. The method as claimed in claim 15, wherein the correction term SUPD for a support point k inside the predetermined surrounding area is given by the following function or depends on the following function:

S_UPD−

^kΔ

p·

f(r)

where f(r) is a Gaussian Function defined as follows;

17. The method as claimed in claim 16, wherein a path of the mobile object is predetermined and the object position at a time of a respective position-finding process is a previously known position.

18. The method as claimed in claim 17, wherein the object moves on one or more predetermined path sections between, in each case, two base stations, and object positions on the respective path section Q being known in advance and a position-finding process being carried out at each of these object positions.

19. The method as claimed in claim 18, wherein,

at object position q (q=1, . . . , Q) of the Q object positions on a path section, the correction term SUPD(r,q) is defined as follows:

20. The method as claimed in claim 19, wherein a distance between consecutive object positions on a predetermined path section is constant and the standard deviation depends on the constant distance and is directly proportional to the constant distance.