Method for predicting the location of a mobile station in a mobile communications network

• US 6,052,598 A
• Filed: 09/30/1997
• Issued: 04/18/2000
• Est. Priority Date: 09/30/1997
• Status: Expired due to Term

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Rudrapatna, Ashok N., Agrawal, Prathima, Agrawal, Dharma P.
• Primary Examiner(s): Bost, Dwayne D.
• Assistant Examiner(s): GELIN, JEAN ALLAND
• Application Number:
  US08/941,231
• Time in Patent Office: 931 Days
• Field of Search: 455/429, 455/432, 455/436, 455/438, 455/437, 455/439, 455/440, 455/441, 455/442, 455/443, 455/422, 455/456, 455/525, 455/38.3, 455/524, 455/435, 455/FOR 101 , 455/FOR 102, 455/FOR 103, 379/FOR 105
• US Class Current: 455/456.1
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The approximate position of a mobile station in a cell can be predicted by measuring the signal strength between the mobile station and the base station of the cell in which it is located and the base stations of the neighboring cells. After a series of instantaneous signal strength measurements have been collected, the velocity and direction of the mobile unit can be determined. Based on the velocity and direction of the mobile unit, future locations of the mobile unit can be predicted including the projected signal strength between the mobile station and the base stations of the cell in which it is located and neighboring cells. Analyzing the projected signal strength values, the time when the mobile unit will require handover to a neighboring cell can be determined and if desired, resources in a neighboring cell can be allocated in anticipation of the mobile unit being handed over to that cell. New signal strength measurements are periodically collected and new projections are made to increase the accuracy of the estimate of when handover will occur and to what neighboring cell.

Claims

1. A method for predicting a location of a mobile unit in a mobile communications network including a plurality of cells, each of the cells having a base station, said method comprising the steps of:

measuring a first series of instantaneous signal strength values over time between a mobile unit and a base station in a current cell where the mobile unit is located;

measuring a second series of instantaneous signal strength values over time between the mobile unit and base stations in neighboring cells;

projecting signal strength values between the mobile station and the base station of the current cell and the mobile station and the base stations of the neighboring cells for a future time based on the first and second series of instantaneous signal values;

determining a handover time when the projected signal strength value between the mobile station and the base station of the current cell is not less than an outgoing handover threshold; and

selecting a neighboring cell in which the projected signal strength value between the mobile station and the base station in the neighboring cell is greater than an incoming handover threshold at the handover time, wherein a predicted location of the mobile station after the handover time is in the selected neighboring cell and the predicted location of the mobile station before the handover time is in the current cell.

2. The method according to claim 1, wherein the step of selecting includes the steps of:

identifying the neighboring cells in which the projected signal strength value between the mobile station and the base station of the neighboring cell is greater than an incoming handover threshold at the handover time; and

comparing the projected signal strength values between the mobile station and the base stations of the identified neighboring cells.

3. The method according to claim 2, wherein said step of comparing includes finding the neighboring cell having the highest projected signal strength value over the longest projected duration.

4. The method according to claim 1, wherein said step of measuring the first series of instantaneous signal strength values includes measuring the first series of instaneous signal strength values in the forward direction and wherein said step of measuring the second series of instantaneous signal strength values includes measuring the second series of instantaneous signal strength values in the forward direction.

5. The method according to claim 1, wherein said step of measuring the first series of instantaneous signal strength values includes measuring the first series of instantaneous signal strength values in the reverse direction and wherein said step of measuring the second series of instantaneous signal strength values includes measuring the second series of instantaneous signal strength values in the reverse direction.

6. The method according to claim 1, wherein said step of projecting includes extrapolating the signal strength values between the mobile station and the base station of the current cell and the mobile station and the base stations of the neighboring cells for the future time using velocity and direction of the mobile unit determined from the first series and second series of instantaneous signal strength values.

7. The method according to claim 1, wherein said step of projecting includes extrapolating the signal strength values between the mobile station and the base station of the current cell and the mobile station and the base stations of the neighboring cells for the future time using a propagation model.

8. The method according to claim 1, wherein instantaneous signal strength values are measured at periodic intervals.

9. The method according to claim 8, wherein the periodic intervals are preset based on size of the current cell.

10. The method according to claim 8, wherein the periodic intervals are set based on estimated velocity of the mobile unit in the current cell.

11. The method according to claim 8, wherein the periodic intervals are set based on a time-of-day.

12. The method according to claim 1, wherein wireless resource needs of the mobile unit are anticipated based on the predicted location of the mobile unit.

13. The method according to claim 1, wherein wireless resources for the mobile unit are allocated in the selected neighboring cell based on the predicted location of the mobile unit.

14. The method of claim 1, wherein said outgoing handover threshold is less than said incoming handover threshold.

15. A mobile communication system method, comprising the steps of:

setting values of an incoming threshold and an outgoing threshold;

measuring a plurality of instantaneous signal strength values of signals between a mobile unit and a plurality of base stations;

extrapolating signal strengths (i) between said mobile unit and a current base station, and (ii) between said mobile unit and a neighboring base station, for a future period of time; and

determining a handover time wherein, at said handover time, an extrapolated signal strength between said mobile unit and said current base station is not less than said outgoing threshold, and an extrapolated signal strength between said mobile unit and said neighboring base station is greater than said incoming threshold.