Expedited location determination in analog service areas

• US 6,438,382 B1
• Filed: 02/14/2001
• Issued: 08/20/2002
• Est. Priority Date: 02/14/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bloebaum, Leland S., Koorapaty, Havish, Boesch, Ronald D.
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): Gantt, Alan T.
• Application Number:
  US09/782,844
• Publication Number:
  US 20020111171A1
• Time in Patent Office: 552 Days
• Field of Search: 342/357.1, 455/456
• US Class Current: 455/456.6
• CPC Class Codes: G01S 19/17 Emergency applications
• 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 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A mobile terminal uses stored GPS data to expedite position determination when placing emergency calls. The mobile terminal receives supporting GPS data such as almanac and ephemeris information from a supporting digital wireless network when digital service is available. When operating in an analog service area where GPS data is not available from the analog wireless network, the mobile terminal uses GPS data previously received in a digital service area, unless that data is too old to be useful. Additionally, the mobile terminal can periodically update its stored GPS data while in standby in an analog service area, based on receiving the needed data directly from available GPS satellites. The mobile terminal or digital wireless network may automatically update GPS data stored in the mobile terminal based on the age of stored data, or based on the probability of moving into an analog service area.

Claims

1. A method of expediting position determination in a dual-mode mobile terminal, the method comprising:

storing position assistance data in said mobile terminal to expedite position determination;

updating said stored position assistance data when operating in a digital service area by acquiring updated assistance information from a supporting communication network; and

updating said stored position assistance data when operating in an analog service area by acquiring updated assistance information from supporting GPS satellites.

2. The method of claim 1 wherein updating said stored position assistance data when operating in said digital service area by acquiring said updated assistance information from said supporting communication network comprises:

predicting when said mobile terminal operating in a digital service area is likely to move into an analog service area; and

updating said stored position assistance data based on said prediction.

3. The method of claim 2 wherein predicting when said mobile terminal operating in said digital service area is likely to move into said analog service area comprises recognizing in the supporting mobile network when said mobile terminal is operating in a fringe area of said digital service area bordering said analog service area.

4. The method of claim 2 wherein predicting when said mobile terminal operating in said current digital service area is likely to move into said analog service area comprises recognizing in said mobile terminal when said mobile terminal is operating in a fringe area of said current digital service area bordering said analog service area.

5. The method of claim 4 wherein recognizing in said mobile terminal when said mobile terminal is operating in a fringe area of said current digital service comprises identifying when at least one analog control channel becomes available.

6. The method of claim 5 wherein identifying when at least one analog control channel becomes available comprises identifying when said at least one analog control channel appears in a neighbor list of nearby base stations maintained in said mobile terminal.

7. The method of claim 1 wherein said updating said stored position assistance data when operating in said digital service area by acquiring updated assistance information from said supporting communication network comprises:

maintaining aging values for individual components comprising said stored position assistance data; and

updating selected ones of said individual components of said stored position assistance data based on said aging values.

8. The method of claim 7 wherein said maintaining said aging values for individual components comprising said stored position assistance data comprises:

monitoring a time since a last download of a selected one of said individual components of said stored position assistance data; and

downloading updated information for said selected one of said individual components of said stored position assistance data based on said time since last download.

9. The method of claim 1 further comprising periodically updating a reference location value of said mobile terminal based on said updated assistance information.

10. The method of claim 1 further comprising periodically updating a reference time value of said mobile terminal based on said updated assistance information.

11. The method of claim 1 further comprising determining a current location of said mobile terminal using said stored position assistance information to expedite satellite signal acquisition at an outset of an emergency call.

12. The method of claim 11 further comprising delaying activation of a transmitter in said mobile terminal at said outset of said emergency call while said mobile terminal is processing satellite signals from relevant ones of said supporting GPS satellites to determine said current position.

13. The method of claim 1 wherein updating said stored position assistance data when operating in said analog service area by acquiring said updated assistance information from said supporting GPS satellites comprises:

identifying at least one GPS satellite expected to be available sometime within a defined window of time;

monitoring for a signal from said at least one GPS satellite during said defined window of time;

downloading satellite information from each of said at least one GPS satellites when said signal becomes available; and

updating said stored position assistance data based on said downloaded satellite information.

14. The method of claim 13 wherein downloading satellite information from each of said at least one GPS satellites when said signal becomes available comprises downloading at least one of two data items, said two data items comprising, for each said GPS satellite that becomes available, clock correction data and ephemeris data.

15. The method of claim 1 wherein said updated assistance information comprises new information for at least some of the data comprising said stored position assistance data, and wherein updating said stored position assistance data when operating in a digital service area by acquiring updated assistance information from a supporting communication network comprises periodically receiving said updated assistance information from said supporting communication network.

16. The method of claim 1 wherein updating said stored position assistance data when operating in an analog service area by acquiring updated assistance information from supporting GPS satellites comprises periodically receiving satellite information from at least one currently available GPS satellite.

17. A mobile terminal comprising:

a user interface to generate output information for a user, and to receive input information from the user;

a transmitter to transmit a transmit signal to a remote base station, said transmit signal containing data derived from said input information;

a receiver to receive a received signal from said remote base station, said received signal containing data used to generate said output information; and

a position detector comprising;

a satellite signal receiver to receive at least one satellite signal from a supporting position assistance satellite; and

processing logic to;

store position assistance data in said mobile terminal to expedite position determination;

update said stored position assistance data when operating in a digital service area by acquiring updated assistance information from a supporting communication network via said transmitter; and

update said stored position assistance data when operating in an analog service area by acquiring updated assistance information from supporting GPS satellites via said satellite signal receiver.

18. The mobile terminal of claim 17 further comprising memory associated with said processing logic to hold said stored position assistance data.

19. The mobile terminal of claim 17 further comprising a system processor to coordinate operations of said mobile terminal, including coordinating operation of said user interface, said transmitter, said receiver, and said position detector.

20. The mobile terminal of claim 17 further comprising a signal processor to process said at least one satellite signal.

21. The mobile terminal of claim 17 wherein at least a portion of said processing logic comprises a system processor.

22. The mobile terminal of claim 21 wherein said system processor comprises logic to predict when said mobile terminal is likely to leave a digital service area and enter an analog service area.

23. The mobile terminal of claim 22 wherein said system processor further comprises logic to request said updated assistance information from said supporting communication network based on said predicting when said mobile terminal is likely to leave said digital service area.

24. The mobile terminal of claim 21 wherein said system processor comprises logic to maintain aging values for selected portions of said stored position assistance data.

25. The mobile terminal of claim 24 wherein said system processor further comprises logic to selectively update portions of said stored position assistance data based on corresponding ones of said aging values.

26. The mobile terminal of claim 25 wherein said system processor further comprises logic to selectively reset said aging values based on updating corresponding portion of said stored position assistance data.

27. The mobile terminal of claim 17 further comprising a system processor to periodically update selected portions of said stored position assistance data based on periodically receiving said at least one satellite signal via said position detector.

28. The mobile terminal of claim 17 wherein said position detector comprises a GPS receiver.

29. The mobile terminal of claim 17 wherein said input information is input speech signals from the user and said output information is output speech signals recovered from said received signal, and wherein said user interface comprises:

a microphone to generate the input speech signals based on voice input from the user; and

a speaker to output an audio signal corresponding to the output speech signals recovered from said received signal.