Position estimating system

• US 20070060170A1
• Filed: 08/31/2006
• Published: 03/15/2007
• Est. Priority Date: 09/09/2005
• Status: Active Grant

• Current Assignee: OKI Electric Industry Company Limited
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Fukui, Kiyoshi
• Granted Patent: US 7,920,874 B2
• Time in Patent Office: Days
• US Class Current: 455/456.100
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A position estimating system capable of accurately estimating the position assumed by a target terminal user based upon measurement of wireless reception signal levels of signals from a target terminal is provided. The position estimating system includes a target terminal that wirelessly transmits a position estimation request, a plurality of reference terminals disposed at specific positions which, measure the signal strength of wireless signals from the target terminal and a position estimating server that estimates the position of the target terminal based upon the reception signal levels measured in correspondence to each of the reference terminals. The reference terminals each include a reception signal level utilization OK/NG judgment unit that makes a judgment as to whether or not the reception signal level value having been measured is to be used in position estimation based upon an index indicating the level of reliability of the reception signal.

Claims

1. A position estimating system comprising:

a target terminal that wirelessly transmits a position estimation request;

a plurality of reference terminals disposed at specific positions to measure reception signal levels of wirelessly transmitted signals from the target terminal; and

a position estimating server that estimates the position of the target terminal based upon the reception signal levels measured in correspondence to each of the reference terminals, wherein;

the plurality of reference terminals each include a reception signal level utilization OK/NG judgment unit that makes a judgment as to whether or not the reception signal level having been measured is to be used in position estimation based upon an index indicating the level of reliability of the reception signal.

3. A position estimating system according to claim 1, wherein:

the reception signal level utilization OK/NG judgment unit compares the index with a predetermined threshold value and determines that the reception signal level value having been measured can be utilized for position estimation if the index is greater than the threshold value.

5. A position estimating system according to claim 1, wherein:

the reception signal level utilization OK/NG judgment unit selects a specific threshold value based upon the reception signal level value having been measured from various threshold values set in advance each in correspondence to a given reception signal level value, compares the index with the selected threshold value and determines that the reception signal level value can be utilized for position estimation if the index is greater than the threshold value.

7. A position estimating system according to claim 1, wherein:

at the reception signal level utilization OK/NG judgment unit, various threshold values are set in advance each in correspondence to a specific distance to the target terminal; and

when information indicating a previously estimated position of the target terminal is obtained, the reception signal level utilization OK/NG judgment unit calculates the distance to the target terminal selects a threshold value based upon the distance thus calculated, compares the index with the selected threshold value and determines that the reception signal level value having been measured can be utilized for position estimation if the index is greater than the threshold value.

9. A position estimating system according to claim 1, wherein:

the index is a correlational value output by a correlation detector engaged in operation when demodulating data exchanged through spread spectrum communication.

2. A position estimating system comprising:

a target terminal that wirelessly transmits a position estimation request;

a plurality of reference terminals disposed at specific positions to measure reception signal levels of wirelessly transmitted signals from the target terminal; and

a position estimating server that determines distances between the target terminal and individual reference terminals based upon the reception signal levels each measured at one of the reference terminals and estimates the position of the target terminal based upon the distances thus determined, wherein;

the plurality of reference terminals each include a reception signal level utilization OK/NG judgment unit that makes a judgment as to whether or not the reception signal level value having been measured is to be used in position estimation based upon an index indicating the level of reliability of the reception signal.

4. A position estimating system according to claim 2, wherein:

the reception signal level utilization OK/NG judgment unit compares the index with a predetermined threshold value and determines that the reception signal level value having been measured can be utilized for position estimation if the index is greater than the threshold value.

6. A position estimating system according to claim 2, wherein:

the reception signal level utilization OK/NG judgment unit selects a specific threshold value based upon the reception signal level value having been measured from various threshold values set in advance each in correspondence to a given reception signal level value, compares the index with the selected threshold value and determines that the reception signal level value can be utilized for position estimation if the index is greater than the threshold value.

8. A position estimating system according to claim 2, wherein:

at the reception signal level utilization OK/NG judgment unit, various threshold values are set in advance each in correspondence to a specific distance to the target terminal; and

when information indicating a previously estimated position of the target terminal is obtained, the reception signal level utilization OK/NG judgment unit calculates the distance to the target terminal selects a threshold value based upon the distance thus calculated, compares the index with the selected threshold value and determines that the reception signal level value having been measured can be utilized for position estimation if the index is greater than the threshold value.

10. A position estimating system according to claim 2, wherein:

the index is a correlational value output by a correlation detector engaged in operation when demodulating data exchanged through spread spectrum communication.