Error estimate concerning a target device's location operable to move in a wireless environment

• US 7,209,752 B2
• Filed: 11/30/2004
• Issued: 04/24/2007
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: AiRISTA Flow, Inc. (AiRISTA, LLC), AiRISTA International Oy (AiRISTA, LLC)
• Original Assignee: Ekahau Oy
• Inventors: Myllymaki, Petri, Tuominen, Antti, Valtonen, Kimmo, Tirri, Henry, Roos, Teemu, Kontkanen, Petri, Wettig, Hannes, Lahtinen, Jussi
• Primary Examiner(s): Nguyen; Duc
• Assistant Examiner(s): LEE, JUSTIN YE
• Application Number:
  US10/999,220
• Publication Number:
  US 20050131635A1
• Time in Patent Office: 875 Days
• Field of Search: 4554561-457, 701/205, 701/217, 382/158
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0252 Radio frequency fingerprinting
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method for determining an error estimate concerning a target device'"'"'s location. The target device moves and communicates in a wireless environment using signals having at least one measurable signal value. A probabilistic model of the wireless environment indicates a probability distribution for signal values at several sample points in the wireless environment. A set of observations of signal values is made and the target device'"'"'s location is estimated based on the probabilistic model and the set of observations. The error estimate is determined as a combination of products over several sample points. Each product comprises a probability distribution for the sample point in question being the target device'"'"'s location and a distance function between the sample point in question and the target device'"'"'s estimated location.

Claims

1. A method for determining an error estimate concerning a target device'"'"'s location, wherein the target device is operable to move in a wireless environment and to communicate with the wireless environment using signals each of which has at least one measurable signal value;

the method comprising;

maintaining a probabilistic model of the wireless environment, the probabilistic model indicating a probability distribution for signal values at several sample points in the wireless environment;

making a set of observations of signal values in the wireless environment at the target device'"'"'s location;

estimating the target device'"'"'s location based on the probabilistic model and the set of observations;

determining the error estimate as a combination of products over several sample points, each product comprising;

a probability for the sample point in question being the target device'"'"'s location; and

a distance function between the sample point in question and the target device'"'"'s estimated location.

2. A method according to claim 1, further comprising using the error estimate to produce a visual indicator to a user.

3. A method according to claim 2, further comprising superimposing the visual indicator on a map.

4. A method according to claim 3, wherein the visual indicator is a set of discrete indicators, each discrete indicator having at least one location-dependent visual attribute.

5. A method according to claim 3, wherein the visual indicator is a set of locations such that the set comprises the target device'"'"'s location at least with a predetermined probability.

6. A method according to claim 3, wherein the visual indicator is an area such that the area comprises the target device'"'"'s location at least with a predetermined probability.

7. A method according to claim 6, further comprising estimating the smallest area that comprises the target device'"'"'s location at least with the predetermined probability.

8. A method according to claim 7, wherein the smallest area is an ellipse.

9. A method according to claim 7, wherein the smallest area is irregularly-shaped.

10. A method according to claim 1, further comprising using the error estimate in updating the probabilistic model.

11. A method according to claim 10, wherein the updating of the probabilistic model comprises adding new sample points at or near locations where the error estimate is higher than average.

12. A method according to claim 10 or 11, wherein the updating of the probabilistic model comprises re-calibrating existing sample points.

13. A method according to claim 1, further comprising performing the combination of products over several sample points only for a sampled subset of the sample points in the probabilistic model.

14. A location-estimating apparatus for estimating a target device'"'"'s location, wherein the target device is operable to move in a wireless environment and to communicate with the wireless environment using signals each of which has at least one measurable signal value;

the location-estimating apparatus comprising;

a probabilistic model of the wireless environment, the probabilistic model indicating a probability distribution for signal values at several sample points in the wireless environment;

means for making or receiving a set of observations of signal values in the wireless environment at the target device'"'"'s location;

means for estimating the target device'"'"'s location based on the probabilistic model and the set of observations;

means for determining an error estimate of the target device'"'"'s estimated location as a combination of products over several sample points, each product comprising;

a probability for the sample point in question being the target device'"'"'s location; and

a distance function between the sample point in question and the target device'"'"'s estimated location.

15. A location-estimating apparatus according to claim 14, further comprising means for producing a visual indicator of the error estimate.

16. A location-estimating apparatus according to claim 15, further comprising means for superimposing the visual indicator on a map.

17. A location-estimating apparatus according to claim 15, wherein the visual indicator is a set of discrete indicators, each discrete indicator having at least one location-dependent visual attribute.

18. A location-estimating apparatus according to claim 15, wherein the visual indicator is a set of locations such that the set comprises the target device'"'"'s location at least with a predetermined probability.

19. A location-estimating apparatus according to claim 15, wherein the visual indicator is an area such that the area comprises the target device'"'"'s location at least with a predetermined probability.

20. A location-estimating apparatus according to claim 15, further comprising means for estimating the smallest area that comprises the target device'"'"'s location at least with the predetermined probability.