Method and a system for location estimation using location estimated

Abstract

In a system for location estimation, information necessary for location estimation is acquired from a wireless signal. The first estimated location of each of target terminals is found out on the basis of the acquired information necessary for location estimation, and the locations of reference terminals. The second estimated location of each target terminal is found out on the basis of the information necessary for location estimation, the first estimated locations of the target terminals other than that target terminal of which the location estimation is being carried out, and on the locations of the reference terminals. Thus, the system for location estimation avoids the problem associated with an increased sphere of location estimation and with an increased communication traffic attendant on an increased number of target terminals, and achieves location estimation of high accuracy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram showing the constitution of an embodiment of a system for location estimation according to the present invention;

FIG. 2 is a schematic block diagram for illustrating a target terminal and a reference terminal in the system shown in FIG. 1;

FIG. 3 is a schematic block diagram for illustrating a location estimator in the system;

FIG. 4 is a flowchart useful for understanding the operation of location estimation by the location estimator in the system;

FIG. 5 is a schematic diagram showing the constitution of an alternative embodiment of a system for location estimation according to the present invention;

FIGS. 6 and 7 are schematic diagrams showing a reference terminal and a target terminal in the system of FIG. 5, respectively;

FIG. 8 is a flowchart useful for understanding the operation of location estimation by the location estimator in the system of FIG. 5; and

FIG. 9 is a schematic diagram showing a further alternative embodiment of a target terminal according to the present invention.

Claims

1. A method for estimating a location of a target terminal, wherein a plurality of target terminals and a plurality of reference terminals transmit and receive a wireless signal to and from each other to estimate the location of the target terminal on a basis of the wireless signal and the location of the plurality of reference terminals, each of the plurality of reference terminals being arranged at a known location, said method comprising the steps of: acquiring information necessary for location estimation from the wireless signal;finding out a first estimated location of each of the plurality of target terminals on the basis of the acquired information necessary for location estimation, and on the location of the plurality of reference terminals; andfinding out a second estimated location of each of the plurality of target terminals on the basis of the information necessary for location estimation, acquired from the wireless signal, the first estimated location of ones of the plurality of target terminals other than the target terminal of which the estimated location is being found out, and the location of the plurality of reference terminals.

2. A system for location estimation comprising: a plurality of target terminals for transmitting and receiving a wireless signal;a plurality of reference terminals each arranged at a known location for transmitting and receiving the wireless signal; anda location estimator for receiving the wireless signal transmitted by said plurality of target terminals and said plurality of reference terminals;said location estimator acquiring information necessary for location estimation from the wireless signal received from said plurality of reference terminals, and finding out a first estimated location for each of said plurality of target terminals on a basis of the acquired information necessary for the location estimation and the location of said plurality of reference terminals;said location estimator acquiring information necessary for location estimation from the wireless signal received from said plurality of reference terminals and said plurality of target terminals, and finding out a second estimated location for each of said plurality of target terminals on the basis of the information necessary for the acquired location estimation, the first estimated location of ones of said plurality of target terminals other than the target terminal of which the estimated location is being found out, and the location of said plurality of reference terminals.

3. The system in accordance with claim 2, wherein each of said plurality of target terminals transmits a location estimation request signal including information of an identification code allotted to the target terminal as a transmitting terminal code; each of said plurality of target terminals, when having received the location estimation request signal transmitted from ones of said plurality of target terminals other than the target terminal receiving, measuring the information necessary for location estimation from the location estimation request signal received, and transmitting a location estimation information signal including the measured information necessary for location estimation, the information on transmitting terminal code included in the location estimation request signal received and the information of the identification code allotted to the target terminal receiving as a relay terminal code;each of said plurality of reference terminals receiving the location estimation request signal transmitted from said plurality of target terminals, measuring the information necessary for location estimation from the location estimation request signal received, and transmitting a location estimation information signal including the information necessary for location estimation measured, the information of the transmitting terminal code included in the location estimation request signal received and information including an identification code allotted to the reference terminal as a relay terminal code;said location estimator receiving the location estimation information signals transmitted from said plurality of target terminals and said plurality of reference terminals, and finding out the first estimated location of said plurality of target terminals on the basis of the information necessary for location estimation included in one of the received location estimation information signals which is of the reference terminal specified by the relay terminal code, and the location of said plurality of reference terminals;said location estimator finding out the second estimated location of said plurality of target terminals on the basis of the information necessary for location estimation included in the location estimation information signals received from said plurality of target terminals and said plurality of reference terminals, the first estimated location of said target terminals other than said target terminal of which the location is to be estimated, and the location of said plurality of reference terminals.

4. The system in accordance with claim 2, wherein, after finding out the second estimated location of each of said plurality of target terminals, said location estimator again finds out the second estimated location of said target terminals other than the target terminal with the second estimated location of the target terminal taken as the first estimated location.

5. The system in accordance with claim 2, wherein said plurality of target terminals or said plurality of reference terminals measure a received power of the wireless signal and have information on the measured power as the information necessary for location estimation.

6. The system in accordance with claim 2, wherein each of said plurality of target terminals has a movement detector for detecting movement thereof, and including information pertinent to the movement of said target terminal into the location estimation information signal;said location estimator storing, each time the location estimation information signal is received, information contained in the location estimation information signal, selecting the stored information on the basis of the information pertinent to the movement of said target terminal, and using the selected information to find out the second estimated location of said target terminal.

7. The system in accordance with claim 6, wherein said location estimator selects the stored information responsive to time elapsed as from receipt of the location estimation information signal, and uses the selected information to find out the second estimated location of said target terminal.

8. The system in accordance with claim 2, wherein in case a distance between the first and second estimated locations of said target terminal is not less than a predetermined value, said location estimator selects a location between the first and second estimated locations as the second estimated location.

9. A system for location estimation comprising: a plurality of target terminals for transmitting and receiving a wireless signal; anda plurality of reference terminals arranged at known locations for transmitting and receiving a wireless signal;each of said plurality of target terminals having a location estimator enclosed therein for receiving a location estimation information signal transmitted from said plurality of reference terminals, measuring information necessary for location estimation from the location estimation information signal received, and finding out a first estimated location of the target terminal in question on a basis of the measured information necessary for location estimation, and a location of said plurality of reference terminals;said location estimator transmitting the location estimation information signal including information on the first estimated location;said location estimator measuring, on receipt of the location estimation information signal transmitted from ones of said plurality of target terminals other than said target terminal in question, the information necessary for location estimation from the location estimation information signal received;said location estimator finding out a second estimated location of said target terminal in question on the basis of the information necessary for location estimation measured from the location estimation information signal transmitted from said target terminals other than said target terminal in question, the first estimated location of said target terminals other than said target terminal in question contained in the location estimation information signal received, the information necessary for location estimation measured from the location estimation information signal transmitted from said plurality of reference terminals, and the location of said plurality of reference terminals.

10. The system in accordance with claim 9, wherein said location estimator transmits, after finding out the second estimated location of said target terminal in question, the location estimation information signal including information of the second estimated location; said location estimator rendering, on receipt of the location estimation information signal inclusive of information on the second estimated location from said target terminals other than the target terminal in question, the second estimated location of said target terminals other than said target terminal in question as the first estimated location, and again finding out the second estimated location of said target terminal in question.

11. The system in accordance with claim 9, wherein said location estimator measures a received power value of the wireless signal, and sets information on the measured value of the received power as the information necessary for location estimation.