Method and System for Sharing an Oscillator for Processing Cellular Radio Signals and GNSS Radio Data Signals By Deferring AFC Corrections

• US 20120223858A1
• Filed: 02/06/2012
• Published: 09/06/2012
• Est. Priority Date: 12/31/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Walley, John, Abraham, Charles
• Granted Patent: US 8,681,043 B2
• Time in Patent Office: Days
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/36 relating to the receiver frond end

Abstract

A global navigation satellite system (GNSS) enabled mobile device comprising a crystal oscillator and an automatic frequency correction (AFC) circuit may be operable to share the crystal oscillator between processing of cellular radio signals and processing of GNSS data messages. The GNSS enabled mobile device may be operable to enforce an AFC correction when the crystal oscillator drifts beyond a specific frequency error. The AFC correction may be allowed during time intervals corresponding to GNSS words at which decoding of these words is not required. The GNSS enabled mobile device may be operable to disable the AFC correction during time intervals associated with decoding of words while the crystal oscillator may drift within the specific frequency error range. After the decoding of one or more of words is completed, the AFC correction may be allowed during the time intervals corresponding to these words.

Claims

1. A method for communication, the method comprising:

performing by one or more processors and/or circuits in a global navigation satellite system (GNSS) enabled mobile device, said one or more processors and/or circuits comprising a crystal oscillator and an automatic frequency correction (AFC) circuit;

sharing said crystal oscillator between processing of cellular radio signals and processing of GNSS data messages, wherein said sharing comprises;

determining time intervals within a time period corresponding to a frame of said GNSS data message for AFC; and

controlling said AFC based on said determined time intervals and a clock reference associated with said cellular radio signals.

2. The method according to claim 1, comprising enforcing said AFC when said crystal oscillator drifts beyond a specific frequency error based on said clock reference.

3. The method according to claim 1, wherein said frame of said GNSS data message comprises a plurality of subframes, and each of said plurality of subframes comprises a plurality of words, and said plurality of words comprise a telemetry word, a handover word and a plurality of data words.

4. The method according to claim 3, comprising allowing said AFC during said time intervals when decoding of one or more of said plurality of data words is not required.

5. The method according to claim 4, comprising allowing said AFC during said time intervals when said plurality of data words are associated with almanac data.

6. The method according to claim 3, comprising disabling said AFC during said time intervals associated with decoding of one or more of said plurality of words while said crystal oscillator drifts within a specific frequency error range based on said clock reference.

7. The method according to claim 6, comprising allowing said AFC during said time intervals that occur after completion of said decoding of said one or more of said plurality of words.

8. The method according to claim 7, comprising allowing said AFC during said time intervals corresponding to said telemetry word and said handover word after a GNSS time is decoded.

9. The method according to claim 1, comprising receiving said GNSS data messages from one of global positioning system (GPS) satellites.

10. The method according to claim 1, comprising receiving said GNSS data messages from one of global orbiting navigation satellite system (GLONASS) satellites.

11. A system for communication, the system comprising:

one or more processors and/or circuits for use in a global navigation satellite system (GNSS) enabled mobile device, wherein said one or more processors and/or circuits comprise a crystal oscillator and an automatic frequency correction (AFC) circuit, and said one or more processors and/or circuits are operable to;

share said crystal oscillator between processing of cellular radio signals and processing of GNSS data messages, and said sharing comprises;

determining time intervals within a time period corresponding to a frame of said GNSS data message for AFC; and

controlling said AFC based on said determined time intervals and a clock reference associated with said cellular radio signals.

12. The system according to claim 11, wherein said one or more processors and/or circuits are operable to enforce said AFC when said crystal oscillator drifts beyond a specific frequency error based on said clock reference.

13. The system according to claim 11, wherein said frame of said GNSS data message comprises a plurality of subframes, and each of said plurality of subframes comprises a plurality of words, and said plurality of words comprise a telemetry word, a handover word and a plurality of data words.

14. The system according to claim 13, wherein said one or more processors and/or circuits are operable to allow said AFC during said time intervals when decoding of one or more of said plurality of data words is not required.

15. The system according to claim 14, wherein said one or more processors and/or circuits are operable to allow said AFC during said time intervals when said plurality of data words are associated with almanac data.

16. The system according to claim 13, wherein said one or more processors and/or circuits are operable to disable said AFC during said time intervals associated with decoding of one or more of said plurality of words while said crystal oscillator drifts within a specific frequency error range based on said clock reference.

17. The system according to claim 16, wherein said one or more processors and/or circuits are operable to allow said AFC during said time intervals that occur after completion of said decoding of said one or more of said plurality of words.

18. The system according to claim 17, wherein said one or more processors and/or circuits are operable to allow said AFC during said time intervals corresponding to said telemetry word and said handover word after a GNSS time is decoded.

19. The system according to claim 11, wherein said one or more processors and/or circuits are operable to receive said GNSS data messages from one of global positioning system (GPS) satellites.

20. The system according to claim 11, wherein said one or more processors and/or circuits are operable to receive said GNSS data messages from one of global orbiting navigation satellite system (GLONASS) satellites.