Position calculation method and position calculation apparatus

• US 6,556,943 B2
• Filed: 08/01/2001
• Issued: 04/29/2003
• Est. Priority Date: 02/07/2001
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kuwahara, Mikio, Yano, Takashi, Fujishima, Kenzaburo, Ishifuji, Tomoaki
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): LE, JOHN H
• Application Number:
  US09/918,641
• Publication Number:
  US 20020147566A1
• Time in Patent Office: 636 Days
• Field of Search: 342/359, 342/450, 342/458, 342/463, 342/464, 342/465, 455/67.1, 455/226.1, 455/456, 455/457, 455/524, 455/525, 701/200, 701/213-214, 701/300, 702/85-87, 702/92, 702/94, 702/95, 702/150, 702/151
• US Class Current: 702/150
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A position calculation method that calculates the correct position of a terminal even when errors are not distributed symmetrically for positive and negative values, by calculating the position of a terminal using the delay time of received signals. The method calculates a first range that is a difference between a range from the terminal to each of antenna and a range from the terminal to a base antenna, the range being calculated from a wireless signal delay time; calculates a second range that is a difference between a range from an assumed terminal position for calculation to each antenna and a range from the assumed terminal position for calculation to the base antenna; calculates a likelihood of the position of the terminal, repeats these procedures to obtain a point where the likelihood is maximized, and determines an obtained most likely solution as the position of the terminal.

Claims

1. A position calculation method using signals transmitted between a terminal and a plurality of antennas located at known and different positions, and between the terminal and at least one base antenna for calculating a position of said terminal, said method comprising:

a first procedure for calculating, for each of said plurality of antennas, a first range difference between a first range from said terminal to each of said plurality of antennas and a second range from said terminal to the base antenna, each of said first and second ranges being calculated based on a respective wireless signal delay time;

a second procedure for calculating, for each of said plurality of antennas, a second range difference between a third range from one of a plurality of terminal position candidates to each of said plurality of antennas and a fourth range from the candidate to said base antenna;

a third procedure for calculating, for each of said plurality of antennas, an error that is a difference between the first range difference and the second range difference;

a fourth procedure for calculating based upon the errors calculated for each of said plurality of antennas having an asymmetric distribution for positive and negative values, a likelihood of the candidate using the distribution and the errors; and

a fifth procedure for repeating the second to fourth procedures for each of the candidates to obtain a most likely candidate with the maximum likelihood as the position of said terminal.

2. A position calculation method according to claim 1, wherein, in said fourth procedure, the error distribution is a non-negative monotone decreasing function in a range where the errors are positive.

3. A position calculation method according to claim 1, wherein, in said fourth procedure, the error distribution is an exponential function in a range where the errors are positive.

4. A position calculation method according to claim 1, wherein said fourth procedure comprises:

determining a minimum error among the errors;

calculating an error difference between each of the errors and the minimum error; and

calculating the likelihood based on an addition result of the error differences.

5. A position calculation method according to claim 4, whereby the likelihood calculating step comprises raising the corrected errors to the n-th power before the addition.

6. A position calculation method according to claim 1, further comprising a procedure for measuring the first range difference a plurality of times,

wherein said fourth procedure uses the plural measurements of the first range difference to calculate the likelihood of the candidate.

7. A position calculation method according to claim 6, wherein said fourth procedure places a respective weight on the antennas according to a number of times the first range difference is calculated for said some antennas.

8. A position calculation apparatus comprising a receiver that receives signals from a plurality of antennas located at known and different positions and from a base antenna, a delay profile analysis apparatus that performs delay profile analysis for the signals received by said receiver, and a calculation apparatus that uses wireless signal delay times included in the delay profile analysis produced by said delay profile analysis apparatus, to calculate a position of said position calculation apparatus, wherein

said calculation apparatus comprises:

first range difference calculation means for calculating, for each of said plurality of antennas, a first range difference between a first range from said terminal to each of said plurality of antennas and a second range from said terminal to the base antenna, each of said first and second ranges being calculated based on a respective wireless signal delay time;

second range difference calculation means for calculating, for each of said plurality of antennas, a second range difference between a third range from one of a plurality of terminal position candidates to each of said plurality of antennas and a fourth range from the candidate to said base antenna;

error calculation means for calculating, for each of said plurality of antennas, an error that is a difference between the first range difference and the second range difference;

likelihood calculation means for calculating based upon the errors calculated by said error calculation means having an asymmetric distribution for positive and negative values, a likelihood of the candidate using the distribution and the errors; and

terminal position search means for obtaining a most likely candidate with the maximum likelihood as the position of said terminal.

9. A position calculation system comprising:

a terminal comprising;

a receiver that receives signals from a plurality of antennas located at known and different positions and from a base antenna;

a delay profile analysis apparatus that performs delay profile analysis for the signals received by said receiver; and

transmission apparatus that transmits delay profile analysis results produced by said delay profile analysis apparatus;

a wireless apparatus that receives the delay profile analysis results from said terminal; and

a calculation apparatus that uses wireless signal delay times included in the received delay profile analysis results to calculate a position of said terminal, wherein

said calculation apparatus comprises;

first range difference calculation means for calculating, for each of said plurality of antennas, a first range difference between a first range from said terminal to each of said plurality of antennas and a second range from said terminal to the base antenna, each of said first and second ranges being calculated based on a respective wireless signal delay time;

second range difference calculation means for calculating, for each of said plurality of antennas, a second range difference between a third range from one of a plurality of terminal position candidates to each of said plurality of antennas and a fourth range from the candidate to said base antenna;

error calculation means for calculating, for each of said plurality of antennas, an error that is a difference between the first range difference and the second range difference;

likelihood calculation means for calculating based upon the errors calculated by said error calculation means having an asymmetric distribution for positive and negative values, a likelihood of the candidate using the distribution and the errors; and

terminal position search means for obtaining a most likely candidate with the maximum likelihood as the position of said terminal.

10. A position calculation system comprising a plurality of antennas located at known and different positions and a base antenna that receive signals from a terminal, a delay profile analysis apparatus that performs delay profile analysis for the signals received by the base antenna, and a calculation apparatus that uses wireless signal delay times included in the delay profile analysis produced by said delay profile analysis apparatus, to calculate a position of said terminal, wherein

said calculation apparatus comprises:

first range difference calculation means for calculating, for each of said plurality of antennas, a first range difference between a first range from said terminal to each of said plurality of antennas and a second range from said terminal to the base antenna, each of said first and second ranges being calculated based on a respective wireless signal delay time;

second range difference calculation means for calculating, for each of said plurality of antennas, a second range difference between a third range from one of a plurality of terminal position candidates to each of said plurality of antennas and a fourth range from the candidate to said base antenna;

error calculation means for calculating, for each of said plurality of antennas, an error that is a difference between the first range difference and the second range difference;

likelihood calculation means for calculating based upon the errors calculated by said error calculation means having an asymmetric distribution for positive and negative values, a likelihood of the candidate using the distribution and the errors each calculated for each of said plurality of antennas; and

terminal position search means for obtaining a most likely candidate with the maximum likelihood as the position of said terminal.