Positioning system and method based on time difference of arrival

• US 20040157621A1
• Filed: 01/09/2004
• Published: 08/12/2004
• Est. Priority Date: 02/07/2003
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Shida, Masaaki, Ogino, Atsushi, Yamasaki, Ryota
• Granted Patent: US 7,139,583 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

In a positioning system using the time difference of arrival of signals between a station and a plurality of access points, each of the access points repeatedly measures a signal for calculating a position from the station, while changing any of time, the position of the station, and a frequency in use, and accumulates a plurality of measurement data. A position calculation server determines a given timing on each of a plurality of delay profiles created based on the measurement data obtained from the access points as a reception timing sample for the signal, performs a combination process with respect to the plurality of reception timing samples, and determines one reception timing for each of the access points. The position calculation server calculates the time difference of arrival of signals between the station and the access points based on the reception timings and calculates the coordinates of the position of the station.

Claims

1. A positioning method, in a wireless communication system including a station and a plurality of access points, for calculating a position of said station based on reception timings of signals transmitted between said station and each of said plurality of access points, said positioning method comprising the steps of:

measuring, for each of the access points, a plurality of reception timing samples for a signal transmitted between the access point and the station; and

determining a reception timing to be used for positioning calculation based on said plurality of reception timing samples.

2. A positioning method according to claim 1, wherein said plurality of reception timing samples are measured at different times.

3. A positioning method according to claim 1, wherein said plurality of reception timing samples are measured by transmitting signals at different frequencies between said station and each of said access points.

4. A positioning method according to claim 1, wherein said plurality of reception timing samples are measured at a plurality of different positions by varying a signal transmission position or a signal receiving position at said station or at each of said access points.

5. A positioning method according to claim 4, wherein two of the plurality of different positions are apart at a distance equal to or more than ½

of a wavelength of a signal used for measurement.

6. A positioning method according to claim 4, wherein each of said access points has a plurality of antennas which are apart at a specified distance or more and transmits or receives a signal for measuring said plurality of reception timing samples by using said plurality of antennas.

7. A positioning method according to claim 1, further comprising the step of:

averaging results of measuring said plurality of reception timing samples to determine the reception timing to be used for said positioning calculation.

8. A positioning method according to claim 1, wherein the reception timing to be used for said positioning calculation is determined by weight averaging each of results of measuring said plurality of reception timing samples in accordance with a reception level of the signal.

9. A positioning method according to claim 1, further comprising the step of:

evaluating an error in each of the reception timing samples that have been measured and excluding the reception timing sample having the error exceeding a specified range, wherein

the reception timing to be used for said positioning calculation is determined based on the reception timing sample having the error within the specified range.

10. An access point in a positioning system in which a position calculation server calculates a position of a station based on reception timings of signals transmitted from the station to each of a plurality of access points, said access point comprising:

an antenna for receiving a signal transmitted from said station;

a radio frequency processing unit for converting said received signal to a base band signal;

a memory for recording the received signal having been converted to said base band signal; and

a signal measurement unit for measuring the signal transmitted from said station for determining said reception timing a plurality of times and transmitting results of measurement to said calculation server.

11. An access point according to claim 10, wherein said signal measurement unit measures the signal from said station a plurality of times at different measurement times.

12. An access point according to claim 10, further comprising:

first and second antennas disposed apart at a distance equal to or more than ½

a wavelength of the signal from said station, the first and second antennas being used to receive the signal for determining said reception timing from said station.

13. An access point according to claim 10, further comprising:

a correlation unit for performing correlation calculation between the plurality of received signals each converted to said base band signal and a predetermined signal sequence, wherein a plurality of results of the correlation calculation outputted from said correlation unit are accumulated in said memory.

14. An access point according to claim 13, wherein said signal measurement unit detects a plurality of reception timing samples from said plurality of results of the correlation calculation, determines a reception timing to be applied to the calculation of the position of said station based on the plurality of reception timing samples, and transmits said reception timing to said calculation server.

15. A program for causing a position calculation server, in a positioning system for measuring a position of a station based on reception timings of signals transmitted from said station to each of a plurality of access points, to perform:

a first procedure for instructing said station via any of said plurality of access points to transmit a plurality of signals to be used for the measurement of the position;

a second procedure for receiving plural sets of reception timing information from each of said plurality of access points having received the plurality of position measurement signals from said station; and

a third procedure for determining, from said plural sets of reception timing information received from said plurality of access points, the reception timing corresponding to each of the access points which is used to calculate the position of said station and calculating the position of said station by using the determined reception timing.

16. A program according to claim 15, wherein said third procedure includes:

a fourth procedure for performing, for each of the access points, correlation calculation between a predetermined signal sequence and received signal information corresponding to said plurality of signals which is included in said sets of reception timing information; and

a fifth procedure for detecting a plurality of reception timing samples from a plurality of results of said correlation calculation, wherein

said reception timing is determined based on the plurality of reception timing samples.

17. A program according to claim 15, wherein said first procedure includes issuing an instruction to said station to transmit said plurality of signals at different times or at different frequencies.

18. A program according to claim 15, wherein each of said access points has a plurality of antennas disposed apart at a distance equal to or more than ½

a wavelength of each of the signals transmitted from said station, said program further comprising;

a sixth procedure for instructing to each of said access points to receive the plurality of signals transmitted from said station by using the different antennas.