System and method for estimating location of mobile station

• US 6,477,380 B1
• Filed: 01/27/1999
• Issued: 11/05/2002
• Est. Priority Date: 01/29/1998
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Uehara, Junji, Kawasumi, Ikuo, Kato, Toshio, Sekine, Kiyoki
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Moore, James K
• Application Number:
  US09/237,794
• Time in Patent Office: 1,378 Days
• Field of Search: 455/422, 455/440, 455/443, 455/501, 455/517, 455/456, 455/522, 455/524, 455/525, 455/63, 455/69, 455/70, 455/561, 455/560, 455/503, 342/457, 342/387, 342/126, 701/207, 340/825.49, 375/371, 370/509, 370/516, 370/518
• US Class Current: 455/456.1
• 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

Abstract

There has been such a drawback that it is difficult to accurately estimate the location of mobile station MS in a mobile communication system. To solve the problem, according to the mobile communication system of the present invention, a mobile station and several base station cooperate for estimation. First the base stations BS in which the mobile station is laid and other base stations adjacent thereto each measure the receipt levels of the radio wave radiated by the mobile station to notify the position manage center of the receipt levels. Second the position manage center instructs the mobile station to control the radio wave pursuant to the receipt levels in such a fashion the receipt levels are stabilized; finally. Third each base station measure the distance between the base station and the mobile station based upon the propagation time of the radio wave to inform the position manage center of the distance. Finally, the position manage center estimates the location of the mobile station based upon a point or several points given by the circles defined using the distances.

Claims

1. A mobile communication system including a plurality of base stations transmitting and receiving a frame to/from a mobile station, and a manage station managing the plurality of base stations, and wherein:

of the base stations comprises

a distance measuring circuit that measures a distance between a respective base station and the mobile station using a radio wave from the mobile station, and notifies the manage station of the distance, and

a receipt level measuring circuit that measures the receipt level of the radio wave and notifies the manage station of the receipt level;

the manage station comprises

an estimating circuit that estimates the location of the mobile station based upon a plurality of distances measured by the plurality of base stations,

an instructing circuit that instructs the mobile station to control a transmission power of the radio wave so that the plurality of respective receipt levels of the plurality of base stations exceed a threshold, and

a departure time notifying circuit that notifies the plurality of base stations of the departure time of the radio wave; and

the mobile station comprises

a power control circuit that controls the transmission power of the radio wave pursuant to the instructions from the manage circuit received via a base station with a receipt level which exceeds the threshold.

2. A mobile communication system as claimed in claim 1, wherein the estimating circuit prepares a plurality of circles which each have a center indicating the location of one of the plurality of base stations and a radius indicating the corresponding one of the plurality of distances, to estimate the location of mobile station using the plurality of circles.

3. A mobile communication system as claimed in claim 2, wherein the estimating circuit estimates that a point at which the plurality of circles cross represents the location of the mobile station.

4. A mobile communication system as claimed in claim 2, wherein the estimating circuit estimates the location of the mobile station using a plurality of points at which the plurality of circles cross.

5. A mobile communication system as claimed in claim 4, wherein the estimating circuit estimates the location of the mobile station using two or more points close to each other among the plurality of points.

6. A mobile communication system as claimed in claim 5, wherein the estimating circuit estimates that the center of a circumscribed circle with respect to a polygon having the plurality of points represents the location of the mobile station.

7. A mobile communication system as claimed in claim 5, wherein the estimating circuit estimates that the center of an inscribed circle with respect to a polygon having the plurality of points represents the location of the mobile station.

8. A mobile communication system as claimed in claim 5, wherein the estimating circuit estimates that the center of gravity with respect to the polygon having the plurality of points represents the location of the mobile stations.

9. A mobile communication system as claimed in claim 5, wherein the estimating circuit estimates that one of the two or more points represents the location of the mobile station.

10. A mobile communication system as claimed in claim 1, wherein the manage station further comprises a storing circuit which stores locations of the plurality of base stations.

11. A mobile communication system as claimed in claim 10, wherein the mobile station comprises

a radiating circuit which radiates a radio wave toward the plurality of base stations, and

wherein the distance measuring circuit comprises

a receiving circuit which receives the radio wave from the mobile station; and a time measuring circuit which measures the period of time for the radio wave to travel from the mobile station to each base station, and wherein the distance measuring circuit computes the distance using the period of time and the propagation velocity of the radio wave.

12. A mobile communication system as claimed in claim 11, wherein the time measuring circuit measures the period of time using the notified departure time of the radio wave and the arrival thereof.

13. A mobile communication system as claimed in claim 11, wherein the instructing circuit instructs the mobile station to increase the transmission power of the radio wave, upon judging that the plurality of receipt levels are insufficient for estimation.

14. A mobile communication system as claimed in claim 11, wherein the power control circuit increases the transmission power of the radio wave so as allow the plurality of base stations to reproduce the frame.

15. A mobile communication system as claimed in claim 14, wherein the time measuring circuit measures the period of time using the departure time of the frame and the arrival time thereof.

16. A mobile communication system as claimed in claim 11, wherein the power control circuit increases the transmission power of the radio wave so as not to cause an interference to another mobile station.

17. A mobile communication system as claimed in claim 16, wherein the power control circuit increases the transmission power of the radio wave stepwise.

18. A mobile communication system as claimed in claim 11, wherein the manage station further comprises a selecting circuit which selects two or more base stations used for estimation among the plurality of base stations.

19. A mobile communication system as claimed in claim 18, wherein the selecting circuit selects a base station involving the mobile station and base stations adjacent to the base station.

20. A mobile communication system as claimed in claim 18, wherein the power control circuit controls the transmission power of the radio so as to allow at least two or more arbitrary base stations to receive a radio wave sufficient for estimation, and wherein the selecting circuit selects the two or more arbitrary base stations.

21. A mobile communication system as claimed in claim 18, wherein the selecting circuit replaces one of the two or more base stations with another base station according to the receipt levels of the two or more base stations.

22. A mobile communication system as claimed in claim 1, wherein the control circuit of the mobile station controls the transmission power of the radio wave pursuant to the instructions via the base station positioned in a cell in which the mobile station exists.

23. A mobile communication system as claimed in claim 1, wherein said transmission power level is increased to a level less than a maximum possible transmission power level of said mobile station.

24. A method of estimating the location of a mobile station in a mobile communication system in which the mobile station and a plurality of base stations communicate with each other, the method comprising:

selecting the base stations for measuring distances between the base station and the mobile station;

checking a receipt level of a radio wave radiated from the mobile station and received by the base stations;

controlling a transmission power of the radio wave radiated from the mobile station by comparing the receipt level at the base station with a given threshold and increasing the transmission power of the radio wave until the given threshold value is exceeded;

notifying the plurality of base stations of the departure time of the radio wave;

ordering the base stations to receive the increased power radio wave radiated from the mobile station;

measuring with each base station distances between each base station and the mobile station based on receipt of the increased power radio wave; and

estimating the location of the mobile station based upon the respective distances measured by the base stations.

25. The method of claim 24, wherein the controlling of the transmission power gradually increases the transmission power of an upward frame, which is sent from the mobile station to the base stations based on the comparison.

26. The method of claim 24, wherein the controlling the transmission power decreases the transmission power of an upward frame sent from the mobile station to the base station upon either a co-channel interference or an adjacent channel interference in one of the selected base stations.

27. The method of claim 24, further comprising:

generating a frame clock at both the base stations and the mobile station and transmitting the frame clock between the base stations and the mobile station with the radio wave;

detecting a phase difference between the receipt of the frame clock and the generated frame clock at both of the base station and the mobile station, respectively; and

correcting the phase difference at both the base stations and the mobile station, respectively.