Position calculation method and position calculation apparatus

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 delay profile analysis results, produced by said delay profile analysis apparatus, to calculate a position of said position calculation apparatus, wherein

• said calculation apparatus comprises:
• first range calculation means for calculating, for each of said plurality of antennas, a first range that is a difference between a range from said terminal to each of said plurality of antennas, said range being calculated based on a wireless signal delay time, and a range from said terminal to the base antenna, said range being calculated based on a wireless signal delay time;
• second range calculation means for calculating, for each of said plurality of antennas, a second range that is a difference between a range from an assumed terminal position for calculation purposes to each of said plurality of antennas and a range from the assumed terminal position for calculation purposes 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 and the second range;
• likelihood calculation means for calculating, assuming that the errors calculated by said error calculation means have a distribution asymmetric for positive and negative values, a likelihood of the assumed terminal position using the distribution and the errors each calculated for each of said plurality of antennas;
• and
• terminal position search means for obtaining a point where the likelihood of the assumed terminal position is maximized and for determining an obtained most likely solution as the position of said terminal.

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
• a 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 calculation means for calculating, for each of said plurality of antennas, a first range that is a difference between a range from said terminal to each of said plurality of antennas, said range being calculated based on a wireless signal delay time, and a range from said terminal to the base antenna, said range being calculated based on a wireless signal delay time;
• second range calculation means for calculating, for each of said plurality of antennas, a second range that is a difference between a range from an assumed terminal position for calculation purposes to each of said plurality of antennas and a range from the assumed terminal position for calculation purposes 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 and the second range;
• likelihood calculation means for calculating, assuming that the errors calculated by said error calculation means have a distribution asymmetric for positive and negative values, a likelihood of the assumed terminal position using the distribution and the errors each calculated for each of said plurality of antennas;
• and
• terminal position search means for obtaining a point where the likelihood of the assumed terminal position is maximized and for determining an obtained most likely solution as the position of said terminal.

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 antenna, and a calculation apparatus that uses wireless signal delay times included in delay profile analysis results, produced by said delay profile analysis apparatus, to calculate a position of said terminal, wherein

• said calculation apparatus comprises:
• first range calculation means for calculating, for each of said plurality of antennas, a first range that is a difference between a range from said terminal to each of said plurality of antennas, said range being calculated based on a wireless signal delay time, and a range from said terminal to the base antenna, said range being calculated based on a wireless signal delay time;
• second range calculation means for calculating, for each of said plurality of antennas, a second range that is a difference between a range from an assumed terminal position for calculation purposes to each of said plurality of antennas and a range from the assumed terminal position for calculation purposes 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 and the second range;
• likelihood calculation means for calculating, assuming that the errors calculated by said error calculation means have a distribution asymmetric for positive and negative values, a likelihood of the assumed terminal position using the distribution and the errors each calculated for each of said plurality of antennas;
• and
• terminal position search means for obtaining a point where the likelihood of the assumed terminal position is maximized and for determining an obtained most likely solution as the position of said terminal.

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 the candidate terminal positions, using one base station 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 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
• the pseudo range is a calculated range between the candidate terminal position and the base station.

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 the calculation apparatus provides a plurality of candidate terminal positions,
• evaluates a likelihood of each of the candidate terminal positions, using one base station 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, 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;
• and
• the pseudo range is a calculated range between the candidate terminal position and the base station.

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 which includes
• 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.