Terminal location system and positioning method

• US 20070217379A1
• Filed: 01/09/2007
• Published: 09/20/2007
• Est. Priority Date: 03/17/2006
• Status: Abandoned Application

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Miyazaki, Masayuki, Mizugaki, Kenichi, Fujiwara, Ryosuke
• Application Number:
  US11/651,083
• Publication Number:
  US 20070217379A1
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• 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
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A location system of a configuration that facilitates initial introduction, maintenance, and system expansion. A terminal location system basically has at least (N+1) base station (here, N=1 to 3) and a location server and finds a position of a terminal performing wireless communication in N-dimensional coordinates. Further, the terminal location system calculates distances among the at least (N+1) base stations, finds relative coordinates of the base stations, evaluates the obtained relative coordinates, determines switching to terminal location processing of finding the position of the terminal, and finds the position of the terminal using propagation times of radio signals transmitted/received among the terminal and the base stations and the obtained relative coordinates of the base stations.

Claims

1. A terminal location system having at least (N+1) base stations, wherein N is in the range of 1 to 3, wherein a terminal location server finds a position of a terminal performing wireless communication in N-dimensional coordinates, and wherein relative coordinates among the at least (N+1) base station are calculated, comprising:

a calculation of relative coordinates among the base stations;

an evaluation of the obtained relative coordinates; and

a switch to terminal location processing for determining the position of the terminal;

wherein the determining of the position of the terminal comprises using propagation times of radio signals transmitted and received between the terminal and the base stations in accordance with the evaluated, obtained relative coordinates of the base stations.

2. The terminal location system according to claim 1,

wherein the at least (N+1) base stations obtain distances among the base stations by measuring propagation times of radio signals among the base stations, and

wherein the relative coordinates of the base stations are measured based on the measured distances among the base stations.

3. The terminal location system according to claim 2,

wherein each of the at least (N+1) base stations measures a first propagation time of the radio signal between itself and the terminal, and measures a second propagation time between itself and at least one other of the base stations, and wherein the position of the terminal is obtained using a difference between the first propagation time and the second propagation time.

4. The terminal location system according to claim 1,

wherein the at least (N+1) base stations include a first base station and at least one second base station, and wherein, if the first base station receives a ranging standby direction from the terminal location server, the first base station transmits a ranging standby direction to the at least one second base station and shifts to a ranging standby state;

and wherein, if the second base station receives the ranging standby direction from the first base station, the second base station shifts to the ranging standby state and transmits an acknowledge signal of being in the ranging standby state;

and wherein, if the first base station receives the acknowledge signals from each of the second base stations having transmitted ranging standby directions, the first base station transmits a signal of completion of the ranging standby states to the terminal location server.

5. The terminal location system according to claim 1,

wherein the radio signals comprise ultra wideband impulse radio signals that send an impulse signal.

6. The terminal location system according to claim 5,

wherein the impulse signal has a pulse width of 3 ns or less.

7. The terminal location system according to claim 1,

wherein the evaluation of the relative coordinates of the base stations comprises outputting an error of the relative coordinates of the base stations, and wherein the calculation of the relative coordinates is obtained by searching a group of the coordinates that minimizes the outputted error.

8. The terminal location system according to claim 7,

wherein the evaluation uses the least squares method.

9. The terminal location system according to claim 7,

wherein the evaluation comprises comparing the obtained error outputted from the evaluating and a previously specified threshold.

10. The terminal location system according to claim 1,

further comprising a display for displaying the obtained relative coordinates among the base stations superimposed on a map of the base stations, and an obtaining of absolute positions of the base stations by altering a spatial relationship of the relative coordinates on the map through image mirroring and rotation.

11. The terminal location system according to claim 1,

wherein the location system selects any one of the at least (N+1) base stations as a reference base station,

and wherein the selected reference base station transmits a reference signal to synchronize the other base stations,

and wherein each of the base stations that does not serve as the reference station measures a first propagation time of a radio signal between itself and the terminal, and measures a second propagation time between itself and the reference base station, and

and wherein the terminal location system obtains the position of the terminal using the first propagation time and the second propagation time.

12. A terminal location system having at least (N+1) base station, wherein N=1 to 3, and a location server, that finds a position of a terminal performing wireless communication in N-dimensional coordinates, the terminal location system comprising:

a relative coordinate detection unit that calculates distances among the at least (N+1) base stations and finds relative coordinates of the base stations;

a determination unit that evaluates the obtained relative coordinates and determines a switching to terminal location processing for finding the position of the terminal; and

a terminal location unit that finds the position of the terminal using propagation times of radio signals transmitted and received among the terminal and the base stations at the obtained relative coordinates of the base stations.

13. The terminal location system according to claim 12,

wherein the at least (N+1) base stations include a first base station connected with the location server by wire and a second base station connected with the first base station by radio signal,

wherein the second base station communicates with the location server by the first base station relaying the radio signal over the wire,

wherein the second base station measures a propagation time of the radio signal between itself and other base stations, and notifies the first base station of the measurement of the propagation time, and

and wherein the first base station notifies the location server by the wire of the measurement of the propagation time transmitted from the second base station.

14. The terminal location system according to claim 12,

wherein at least one of the base stations is connected with the location server by radio signal, and the base station measures a propagation time of a radio signal and notifies the location server of the measurement result of the propagation time by the radio signal.

15. The terminal location system according to claim 12,

wherein the base stations include a first base station connected with the location server by wire, a second base station connected with the first base station by radio, and a third base station connected with the second base station by radio;

wherein the second base station communicates with the location server by relaying through the first base station,

and the third base station communicates with the location server by relaying through the second base station and the first base station;

wherein the third base station measures a propagation time of a radio signal between itself and the other base stations, and notifies the measurement result of the propagation time to the second base station,

and the second base station notifies the first base station of the measurement result of the propagation time transmitted from the third base station, and

the first base station notifies the location server of the measurement result of the propagation time transmitted from the second base station.

16. The terminal location system according to claim 15,

wherein, if the first base station receives a ranging direction from the location server, the first base station transmits a ranging direction to the second base station,

and if the second base station receives the ranging direction from the first base station, the second base station transmits a ranging direction to the third base station,

and if the third base station receives the ranging direction from the second base station, the third base station specifies a fourth base station contained in the received ranging direction, transmits a ranging signal to the specified fourth base station, and shifts to a standby state of an acknowledge signal to the ranging signal, and

if the third base station receives the acknowledge signal from the fourth base station, the third base station measures a propagation time of a radio signal between itself and the fourth base station, and transmits the measured propagation time of the radio signal to the location server via the second base station and the first base station.

17. The terminal location system according to claim 15,

Wherein, if the first base station receives a location standby direction from the location server, the first base station transmits a location standby direction to the second base station,

and if the second base station receives the location standby direction from the first base station, the second base station transmits a location standby direction to the third base station and shifts to a location signal standby state,

and if the third base station receives the location standby direction from the second base station, the third base station shifts to a location signal standby state and transmits an acknowledge signal to the location standby direction, and

if the second base station receives the acknowledge signal from the third base station, the second base station transmits completion of the location standby state to the location server via the second base station and the first base station.

18. The terminal location system according to claim 15,

wherein the second and third base stations each measure a first propagation time of a radio signal between itself and the terminal, measure a second propagation time of a radio signal between itself and the other base station, and the position of the terminal is found using a differencing between the first propagation time and the second propagation time.

19. A positioning method in a terminal location system that has at least (N+1) base stations and a location server, the positioning method comprising the steps of:

calculating distances among the at least (N+1) base stations;

calculating relative coordinates of the base stations;

evaluating the obtained relative coordinates;

determining to switch to terminal location processing for finding a position of a terminal;

measuring a propagation time of a radio signal transmitted and received between the terminal and the base station; and

finding by the location server of the position of the terminal in N-dimensional coordinates using the measured propagation times and the obtained relative coordinates of the base stations.

20. The positioning method in a terminal location system according to claim 19,

wherein the location server transmits a ranging standby direction to the base stations,

and if the base stations each receive the ranging standby direction transmitted from the location server, each base station shifts to a ranging standby state and measures a propagation time of the radio signal among the base stations, and

the location server calculates distances among the base stations based on the propagation times, calculates relative coordinates among the base stations, evaluates the obtained relative coordinates, determines switching to the terminal location processing for finding the position of the terminal, and transmits a location standby direction to the base stations after having done switching to the terminal location processing,

and if the base stations each receive the location standby direction transmitted from the location server, each of them shifts to a location standby state, measures a first propagation time between itself and the terminal, measures a second propagation time between itself and the other base station, and the server calculates the position of the terminal using a differencing between the first propagation time and the second propagation time and the relative coordinates of the base stations.