Position calculation method and position calculation apparatus

• US 6,671,649 B2
• Filed: 03/19/2003
• Issued: 12/30/2003
• Est. Priority Date: 02/07/2001
• Status: Expired due to Fees

• 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:
  US10/390,721
• Publication Number:
  US 20030191604A1
• Time in Patent Office: 286 Days
• Field of Search: 702/85-87, 702/92, 702/94, 702/95, 702/150-151, 342/357.06, 342/357.09, 342/457, 342/458, 370/328, 370/335, 375/141, 375/356, 455/456.1, 455/456.2, 455/456.3, 455/456.4, 455/436, 455/404.2, 701/200, 701/213-214
• 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 method of determining a position of a terminal, using reception timings of signals transmitted between the terminal and a plurality of base stations, comprising the steps of:

providing a plurality of candidate terminal positions;

evaluating a likelihood of each of said plurality of candidate terminal positions using one of plurality of base stations as a reference for which a range error between a pseudo measured range and a pseudo range is less than for the remaining base stations,

wherein said likelihood of each of said plurality of candidate terminal positions is evaluated according to a probability density of a reception timing error which is asymmetric for positive and negative values, and

determining a candidate terminal position with a highest likelihood as the position of the terminal,

wherein the pseudo measured range is a range between the terminal and a base station according to the reception timings of signals, and

wherein said pseudo range is a calculated range between the candidate terminal position and the base station.

2. A method of determining a position of a terminal, using reception timings of signals transmitted between the terminal and a plurality of base stations, comprising the steps of:

providing a plurality of candidate terminal positions;

evaluating a likelihood of each of said plurality of candidate terminal positions using one of plurality of base stations as a reference for which a range error between a pseudo measured range and a pseudo range is less than for the remaining base stations,

wherein said likelihood of each of said plurality of candidate terminal positions is evaluated according to a probability density of a range error which is a monotone decreasing function for values that are greater than the range error of the reference candidate terminal position, and

determining a candidate terminal position with a highest likelihood as the position of the terminal,

wherein the pseudo measured range is a range between the terminal and a base station according to the reception timings of signals, and

wherein said pseudo range is a calculated range between the candidate terminal position and the base station.

3. A terminal for a system having a plurality of base stations for determining a position of the terminal, comprising:

a receiver for receiving signals from the plurality of base stations;

a delay profile analysis apparatus for determining reception timings of the received signals; and

a calculation apparatus for determining the position of the terminal,

wherein said calculation apparatus provides a plurality of candidate terminal positions;

wherein the calculation apparatus evaluates a likelihood of each of said plurality of candidate terminal positions, using a base station from said plurality of base stations as a reference for which a range error between a pseudo measured range and a pseudo range is less than for the other base stations,

wherein said likelihood of each of said plurality of the candidate terminal positions is evaluated according to a probability density of a reception timing error which is asymmetric for positive and negative values;

wherein said calculation apparatus determines a candidate terminal position with a highest likelihood as the position of the terminal;

wherein said pseudo measured range is a range between the terminal and a base station according to the reception timings of signals; and

wherein said pseudo range is a calculated range between the candidate terminal position and said base station.

4. A terminal for a system having a plurality of base stations for determining a position of the terminal, comprising:

a receiver for receiving signals from the plurality of base stations;

a delay profile analysis apparatus for determining reception timings of the received signals; and

a calculation apparatus for determining the position of the terminal,

wherein said calculation apparatus provides a plurality of candidate terminal positions;

wherein the calculation apparatus evaluates a likelihood of each of said plurality of candidate terminal positions, using a base station from said plurality of base stations as a reference for which a range error between a pseudo measured range and a pseudo range is less than for the other base stations,

wherein said likelihood of each of said plurality of the candidate terminal positions is evaluated according to a probability density of a reception timing error which is asymmetric for positive and negative values;

wherein said calculation apparatus determines a candidate terminal position with a highest likelihood as the position of the terminal;

wherein said likelihood of candidate terminal positions are evaluated according to a probability density of a range error which is a monotone decreasing function for values that are greater than the range error of the reference candidate terminal position, and

determines a candidate terminal position with a highest likelihood as the position of the terminal,

wherein the pseudo measured range is a range between the terminal and a base station according to the reception timings of signals,

wherein the pseudo range is a calculated range between the candidate terminal position and the base station, and

wherein a likelihood of the candidate terminal positions are evaluated according to a probability density of a range error which is a monotone decreasing function for values that are greater than the range error of the reference candidate terminal position.

5. A medium for storing a program that causes a computer to execute a position calculation method, comprising the steps of:

receiving information of reception timings of signals transmitted between a plurality of antennas and a terminal, and

calculating a position of the terminal using wireless signal delay times, comprising;

a first procedure for calculating a delay time difference between signals transmitted between the terminal and the plurality of antennas;

a second procedure for providing a plurality of candidate terminal positions;

a third procedure for calculating a pseudo range between each of the candidate terminal positions and each of the plurality of base stations;

a fourth procedure for calculating a likelihood of each of the plurality of candidate terminal positions based on the delay time difference and the pseudo ranges and determining a candidate terminal position with a highest likelihood as the position of the terminal,

wherein the likelihood of the candidate terminal positions are evaluated according to a probability density of a reception timing error which is asymmetric for positive and negative values.

6. A medium for storing a program that causes a computer to execute a position calculation method for a terminal, comprising the steps of:

receiving information of reception timings of signals transmitted between a plurality of antennas and a terminal, and

calculating a position of the terminal using wireless signal delay times, comprising;

a first procedure for calculating a delay time difference between signals transmitted between the terminal and the plurality of antennas;

a second procedure for providing a plurality of candidate terminal positions;

a third procedure for calculating a pseudo range between each of the candidate terminal positions and each of the plurality of base stations;

a fourth procedure for calculating a likelihood of each of the plurality of candidate terminal positions based on the delay time difference and the pseudo ranges and determining a candidate terminal position with a highest likelihood as the position of the terminal,

wherein the likelihood of the candidate terminal positions are evaluated using one base station as a reference for which a range error between a pseudo measured range and the pseudo range is less than for the other base stations, according to a probability density of a reception timing error which is asymmetric for positive and negative values, wherein the pseudo measured range is a range between the terminal and a base station according to the reception timings of signals.