Efficient location of mobile radiotelephones using cellular and GPS information

• US 20020102992A1
• Filed: 01/31/2001
• Published: 08/01/2002
• Est. Priority Date: 01/31/2001
• Status: Active Grant

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Koorapaty, Havish, Bloebaum, L. Scott
• Granted Patent: US 6,801,778 B2
• Time in Patent Office: Days
• US Class Current: 455/456.5
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

The invention specifies various methods for the provision or calculation of a reference location for GPS-equipped mobile communications devices, specifically, GPS-equipped cellular phones. This is accomplished by providing certain GPS-related information over the cellular network, and by calculating reference locations based on various criteria, aided by actual position fixes provided by the built-in GPS receiver.

Claims

1. A method for computing a reference location for a mobile communications device having a GPS receiver and connected to a communications network comprising the steps of:

identifying a point of connection to said communications network;

obtaining, over time, a plurality of actual position readings from said GPS receiver and correlating said position readings to said identified point of connection; and

processing said plurality of correlated position readings to obtain a reference location when connected to said communications network at said identified point of connection.

2. The method of claim 1 wherein said step of processing said plurality of position readings includes the step of averaging said plurality of position readings.

3. The method of claim 1 wherein said step of processing said plurality of position readings includes the step of choosing one of said plurality of position readings as said reference location.

4. The method of claim 1 further comprising the step of applying a qualifying criteria to each of said actual position readings prior to including each of said position readings in said processing.

5. The method of claim 1 wherein said communications network is a cellular telephone network and wherein said mobile communications device is a GPS-equipped cellular telephone.

6. The method of claim 4 wherein said step of applying qualifying criteria includes the steps of:

monitoring said identified point of connection for a predetermined period of time;

determining the percentage of said predetermined time period that said mobile communications device was connected to said communications network at said identified point of connection; and

discarding any positions recorded from said GPS receiver during said pre-determined time period if said percentage is below a set threshold value.

7. The method of claim 1 further comprising the step of providing said reference location in response to a position request from an application.

8. The method of claim 1 further comprising the step of using said reference location as an aid for computing a final position using said GPS receiver in response to a position request from an application.

9. The method of claim 4 wherein said step of applying qualifying criteria includes the steps of:

accessing a doppler estimator when said position readings from said GPS receiver are recorded; and

discarding position readings obtained when said doppler estimator indicates a speed above a set threshold.

10. A method of refining a reference location for a mobile communications device having a GPS receiver and connected to a communications network comprising the steps of:

receiving a plurality of signals, each of said signals having an associated signal strength, from a plurality of identified connection points to said communications network;

recalling, from a data storage media, one or more positions corresponding to each of said identified connection points from which a signal is being received; and

processing said recalled positions to obtain said refined reference location.

11. The method of claim 10 wherein said step of processing said recalled position readings includes the step of averaging said recalled position readings.

12. The method of claim 10 wherein said step of processing said recalled position readings includes the step of choosing one of said recalled position readings as said reference location.

13. The method of claim 11 wherein said step of averaging said recalled positions includes the step of taking a weighted average of said recalled positions, wherein said recalled positions are weighted by said signal strength associated with each of said identified connection points.

14. The method of claim 13 wherein said step of recalling positions includes the step of recalling only positions which correspond to identified connection points from which a signal is being received having a signal strength above a predetermined threshold.

15. The method of claim 10 wherein said step of recalling positions includes the step of recalling only a predetermined number of positions corresponding to the to identified connection points from which signals having the highest signal strengths are being received.

16. The method of claim 10 wherein said step of recalling positions includes the step of recalling only positions corresponding to the to identified connection points from which signals within a predetermined signal strength range are being received.

17. The method of claim 10 further comprising the step of providing said reference location in response to a position request from an application.

18. The method of claim 10 further comprising the step of using said reference location as an aid for computing a final position using said GPS receiver in response to a position request from an application.

19. The method of claim 10 further comprising the step of categorizing said received signals based on said received signal strengths.

20. A method of refining a reference location for a mobile communications device having a GPS receiver and connected to a communications network comprising the steps of:

previously storing in a data storage media a plurality of positions provided by said GPS receiver;

previously storing in a data storage media a plurality of signal strength readings from various identified connection points to said communications network for each of said positions provided by said GPS receiver;

receiving signals from a plurality of identified connection points;

profiling said signals based on the strength of said received signals;

recalling from said data storage media one or more positions having received signal strength profiles similar to the signal strength profiles of the currently received signals; and

processing said recalled positions to obtain said refined reference location.

21. The method of claim 20 wherein said step of processing said recalled position readings includes the step of averaging said recalled position readings.

22. The method of claim 20 wherein said step of processing said recalled position readings includes the step of choosing one of said recalled position readings as said reference location.

23. The method of claim 22 further comprising the step of providing said reference location in response to a position request from an application.

24. The method of claim 22 further comprising the step of using said reference location as an aid for computing a final position using said GPS receiver in response to a position request from an application.

26. The method of claim 25 wherein said step of computing said reference location includes the step of taking a weighted average of said estimated distances, wherein said distances are weighted by said signal strength associated with each of said identified connection points.

27. The method of claim 25 further comprising the step of providing said reference location in response to a position request from an application.

28. The method of claim 25 further comprising the step of using said reference location as an aid for computing a final position using said GPS receiver in response to a position request from an application.

30. The method of claim 29 further comprising the step of obtaining an actual position fix from said GPS receiver if said quality of said computed position is insufficient.

25. A method for computing a reference location for a mobile communications device having a GPS receiver and connected to a communications network comprising the steps of:

receiving signals from a plurality of identified connection points to a communications network, each of said received signals having an associated signal strength;

estimating the distance from said mobile communications device to each of said identified connection points based on said aid signal strengths; and

computing said reference location using said estimated distances.

29. A method for determining the quality of a computed reference location for a mobile comminations device equipped with a GPS receiver comprising the steps of:

recording, over a period of time, a plurality of positions when connected to a particular identified connection point to a comminations network;

estimating, based on the variance of said positions, the size of the geographic area associated with said particular identified connection point; and

determining, when a request for position is received, if the quality of a computed reference location is sufficient, based on the possible deviation of said computed reference location from the actual location based on said estimated size of said geographic area associated with said particular identified connection point.

31. A method of computing a reference location for a mobile communications device equipped with a GPS receiver when connected to a private communication network comprising the steps of:

repeatedly obtaining an actual position fix from said GPS receiver until contact with GPS satellites is lost; and

using the last position recorded by said GPS receiver as said reference location when connected to any identified connection point to said private communication network, until contact with said GPS satellites is re-gained.

32. The method of claim 31 further comprising the step of providing said last recorded position in response to a position request from an application.