CONCEPT FOR LOCALIZING A POSITION ON A PATH

• US 20100097269A1
• Filed: 09/04/2007
• Published: 04/22/2010
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Meyer, Steffen, Hupp, Juergen, Loidl, Karin
• Granted Patent: US 8,174,447 B2
• Time in Patent Office: Days
• US Class Current: 342/378
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 5/0252 Radio frequency fingerprinting

Abstract

An apparatus for localizing a position on a path, radio signals of fixedly positioned radio transmitters being receivable along the path, the apparatus including a determiner for determining properties of the radio signals of the fixedly positioned radio transmitters at the position, and a comparator for comparing the determined electromagnetic properties with previously recorded properties which characterize a reference path, and for determining a relation between the position and the reference path on the basis of a result of the comparison.

Claims

1-43. -43. (canceled)

44. An apparatus for localizing a position or for navigating on a path, radio signals of fixedly positioned radio transmitters being receivable along the path, the apparatus comprising:

a comparator for comparing electromagnetic properties of the radio signals, which unambiguously identify a measurement point, so as to examine several reference paths, on the basis of common features of the electromagnetic properties, for an intersection point characterizing an identical geographic position in different reference paths, and to interconnect the reference paths to form a graph, intersection points and the current positions of terminal devices being regarded as nodes, and portions of paths between the intersection points and/or current positions of the terminal devices being regarded as edges of the graph, and a reference path being distinguished by a temporal succession of previously recorded electromagnetic properties of the radio signals of fixedly positioned radio transmitters;

a determiner for determining a guidance path from the position to the intersection point, the determiner for determining the guidance path being configured to determine the guidance path by means of a routing algorithm on the basis of the graph; and

a determiner for determining properties of the radio signals of the fixedly positioned radio transmitters at the position on the path, the determined properties of the radio signals comprising electromagnetic properties of the radio signals,

the comparator being configured to compare the electromagnetic properties of the radio signals with previously recorded electromagnetic properties of the radio signals which characterize the guidance path, and to determine a relation between the position and the guidance path on the basis of a result of the comparison.

45. The apparatus as claimed in claim 44, wherein the determiner for determining the properties is configured to determine a received field strength, a received power spectrum, and/or a signal/noise power ratio of the radio signals at the position.

46. The apparatus as claimed in claim 44, wherein the determiner for determining the properties is configured to determine, from the properties determined, a transmitter identification identifying a fixedly positioned radio transmitter.

47. The apparatus as claimed in claim 44, configured to learn about the current transmitting power of a fixedly positioned radio transmitter.

48. The apparatus as claimed in claim 44, wherein the apparatus further comprises a processor for processing the determined electromagnetic properties of the radio signals.

49. The apparatus as claimed in claim 48, wherein the processor is configured to associate a predetermined electromagnetic signal property with a radio signal of a stationary radio transmitter if no electromagnetic signal property of the radio transmitter may be determined, so as to acquire an identical number of determined electromagnetic properties per time interval Δ

T for a plurality of radio transmitters at the position, respectively.

50. The apparatus as claimed in claim 48, wherein the processor is configured to set RSSI_k(i+1)=RSSI_k(i) if RSSI_k(i+1)<

(RSSI_k(i)−

Δ

RSSI_k), wherein RSSI_k(i+1)=RSSI_k(i) may only repeat itself twice for two successive measurement values in each case, and wherein RSSI_k(i) is a measure of an electromagnetic field strength, determined at the position at the i^th measurement value, of a radio signal of a k^th stationary radio transmitter.

51. The apparatus as claimed in claim 48, wherein the processor comprises a low-pass filter to be able to determine an average waveform of the electromagnetic properties of the radio signals of the stationary radio transmitters.

52. The apparatus as claimed in claim 51, wherein the processor further comprises an interpolator for interpolating the average waveform, the interpolator being configured to interpolate the average waveform when a maximum between second and third zero crossings of the derivation of the waveform is larger than a value X₁, and when a minimum between a first and the second zero crossings of the derivation of the waveform is smaller than a value X₂, or when the maximum between the second and third zero crossings of the derivation of the waveform is larger than a value X₃, and when the minimum between the first and second zero crossings of the derivation of the waveform is smaller than a value X₄.

53. The apparatus as claimed in claim 44, wherein the comparator is configured to associate, with a sought-for measurement package of field strengths which corresponds to the position on the path, those N stationary radio transmitters which at the position comprise the highest N field strengths, and to place them into an order in accordance with the field strengths, and to then compare the sought-for measurement package with a measurement package, which was previously determined accordingly, of the reference path.

54. The apparatus as claimed in claim 53, wherein the comparator identifies, by means of a first comparison stage, a similarity between the sought-for measurement package and the reference measurement package precisely when at least N-1 radio transmitters of the sought-for measurement package are comprised within the reference measurement package, and when the strongest radio transmitter from the sought-for measurement package is among the two strongest radio transmitters of the reference measurement package, and when the N^th strongest radio transmitter of the sought-for measurement package is not among the two strongest radio transmitters from the reference measurement package, and when the second strongest radio transmitter from the sought-for measurement package is among the N-1 strongest radio transmitters from the reference measurement package, wherein with a similarity found the respective reference measurement package is taken into account in a result quantity of the first comparison stage.

55. The apparatus as claimed in claim 54, wherein the comparator further comprises a second comparison stage configured to determine, with the result quantity of the first comparison stage, a standard deviation between the results of the result quantity and the sought-for measurement package in accordance with

$\sigma$

= 1 N - 1 

∑

x = 1 N 

( d x - d m ) 2 ,

wherein d_x signifies a magnitude of the difference between RSSI values of two identical stationary radio transmitters from the sought-for measurement package and a reference measurement package from the result quantity of the first comparison stage, and dm signifies an average value of the differences d_x.

56. The apparatus as claimed in claim 44, wherein the comparator is configured to check the previously recorded electromagnetic properties charactering the reference path for a loop and/or a standstill within the reference path, and to remove these electromagnetic properties which correspond to the loop and/or the standstill, if need be.

57. A method of localizing a position or for navigating on a path, radio signals of fixedly positioned radio transmitters being receivable along the path, the method comprising:

comparing electromagnetic properties of the radio signals, which unambiguously identify a measurement point, of several reference paths so as to search, on the basis of common features of the electromagnetic properties, for an intersection point characterizing an identical geographic position in different reference paths, a reference path being distinguished by a temporal succession of previously recorded electromagnetic properties of the radio signals of fixedly positioned radio transmitters;

interconnecting the reference paths to form a graph, intersection points and current positions of terminal devices being regarded as nodes, and portions of paths between the intersection points and/or current positions of the terminal devices being regarded as edges of the graph;

determining a guidance path from the position to the intersection point by means of a routing algorithm on the basis of the graph; and

receiving the radio signals of the fixedly positioned radio transmitters at the position on the path;

determining properties of the radio signals of the fixedly positioned radio transmitters at the position on the guidance path, the determined properties of the radio signals comprising electromagnetic properties of the radio signals; and

comparing the determined electromagnetic properties with previously recorded electromagnetic properties which characterize the guidance path; and

determining a relation between the position and the guidance path on the basis of a result of the comparison.

58. A computer readable medium storing a computer program comprising program code for performing, when the computer program runs on a computer, the method of localizing a position or for navigating on a path, radio signals of fixedly positioned radio transmitters being receivable along the path, the method comprising:

comparing electromagnetic properties of the radio signals, which unambiguously identify a measurement point, of several reference paths so as to search, on the basis of common features of the electromagnetic properties, for an intersection point characterizing an identical geographic position in different reference paths, a reference path being distinguished by a temporal succession of previously recorded electromagnetic properties of the radio signals of fixedly positioned radio transmitters;

interconnecting the reference paths to form a graph, intersection points and current positions of terminal devices being regarded as nodes, and portions of paths between the intersection points and/or current positions of the terminal devices being regarded as edges of the graph;

determining a guidance path from the position to the intersection point by means of a routing algorithm on the basis of the graph; and

receiving the radio signals of the fixedly positioned radio transmitters at the position on the path;

determining properties of the radio signals of the fixedly positioned radio transmitters at the position on the guidance path, the determined properties of the radio signals comprising electromagnetic properties of the radio signals; and

comparing the determined electromagnetic properties with previously recorded electromagnetic properties which characterize the guidance path; and

determining a relation between the position and the guidance path on the basis of a result of the comparison.