METHODS AND APPARATUS FOR OBTAINING GNSS TIME IN A GNSS RECEIVER

• US 20110163915A1
• Filed: 03/18/2011
• Published: 07/07/2011
• Est. Priority Date: 09/06/2007
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Liu, Hsien-Chang, Chen, An-Bang, Huang, Kung-Shuan
• Granted Patent: US 8,077,086 B2
• Time in Patent Office: Days
• US Class Current: 342/357.49
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/39 the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
• CPC Class Codes: G04R 20/04 Tuning or receiving; Circuits therefor

Abstract

A method and apparatus for obtaining Global navigation Satellite System (GNSS) time in a GNSS receiver are provided. The following steps are included: obtaining a time relationship between a first clock signal and the received GNSS time; obtaining a first clock value of a second clock signal and an first associated clock value of the first clock signal at a first time point; calculating a first GNSS time corresponding to the first clock value of the second clock signal according to the first associated clock value and the time relationship; obtaining a second clock value of the second clock signal and an second associated clock value of the first clock signal at a second time point; and calculating a second GNSS time corresponding to the second associated clock value, according to the first GNSS time, the first clock value and the second clock value of the second clock signal.

Claims

1. A method for obtaining Global navigation Satellite System (GNSS) time in a GNSS receiver, the method comprising:

obtaining a time relationship between a first clock signal and the received GNSS time;

obtaining a first clock value of a second clock signal and further obtaining an first associated clock value of the first clock signal at a first time point;

calculating a first GNSS time corresponding to the first clock value of the second clock signal according to the first associated clock value of the first clock signal and the time relationship;

obtaining a second clock value of the second clock signal and further obtaining an second associated clock value of the first clock signal at a second time point; and

calculating a second GNSS time corresponding to the second associated clock value of the first clock signal at the second time point, according to the first GNSS time, the first clock value of the second clock signal, and second clock value of the second clock signal.

2. The method of claim 1 further comprising:

controlling at least a portion of the GNSS receiver to enter a power saving mode during a time period between the first time point and the second time point.

3. The method of claim 1, wherein the time relationship between the first clock signal and the GNSS time represents value mapping between the clock value of the first clock signal and the GNSS time.

4. The method of claim 1, further comprising:

performing synchronization measurement at the first time point to obtain the first associated clock value of the first clock signal and the first clock value of the second clock signal;

performing synchronization measurement at the second time point to obtain the second associated clock value of the first clock signal and the second clock value of the second clock signal.

5. The method of claim 4, wherein the second clock signal is synchronized with a frame time clock of a cellular network;

the synchronization measurement performed at the first time point represents frame synchronization measurement, and first clock value of the second clock represents a frame number FN1; and

the synchronization measurement performed at the second time point represents frame synchronization measurement, and the second clock value of the second clock represents a frame number FN2.

6. The method of claim 5, further comprising:

calculating the second GNSS time by the following equation;

C2=C1+(FN2−

FN1)*T_Frame*(1−

D_Frame);

wherein C1 represents the first GNSS time, C2 represents the second GNSS time, the T_Frame represents a length of a frame cycle of the frame time clock, and the D_Frame represents a frame time clock drift of the frame time clock.

7. The method of claim 6, further comprising:

before the step of calculating the second GNSS time, updating D_Frame, wherein D_Frame represents a frame time clock drift of the frame time clock.

8. The method of claim 5, further comprising:

calculating the second GNSS time according to a frame time clock drift of the frame time clock, the first GNSS time, the frame number FN1, and the frame number FN2.

9. The method of claim 4, wherein the second clock signal is derived from a clock source representing a system clock;

the synchronization measurement performed at the first time point represents clock synchronization measurement; and

the synchronization measurement performed at the second time point represents clock synchronization measurement.

10. The method of claim 1, wherein the step of obtaining the first clock value of the second clock signal and further obtaining the first associated clock value of the first clock signal comprises:

utilizing the first clock signal to measure arrival time of a pulse corresponding to the second clock value of the second clock time in order to obtain the first associated clock value;

wherein the step of obtaining the second clock value of the second clock signal and further obtaining the second associated clock value of the first clock signal further comprises;

Utilizing the first clock signal to measure arrival time of a pulse corresponding to second clock value of the second clock time in order to obtain the second associated clock value.

12. The method of claim 1 further comprising:

controlling at least a portion of the GNSS receiver to enter a power saving mode during a time period between the first time point and the second time point.

11. A method for obtaining Global navigation Satellite System (GNSS) time in a GNSS receiver, the method comprising:

receiving a first frame number of a frame time clock of a cellular network at a first time point;

obtaining a first GNSS time corresponding to the first frame number;

receiving a second frame number of the frame time clock at a second time point; and

obtaining a second GNSS time corresponding to an associated clock value of a clock signal of the GNSS receiver, according to the first GNSS time, the first frame number, and the second frame number.

13. The method of claim 11, further comprising:

calculating the second GNSS time by the following equation;

C2=C1+(FN2−

FN1)*T_Frame*(1−

D_Frame);

wherein C1 represents the first GNSS time, C2 represents the second GNSS time, FN1 represents the first frame number, the FN2 represents the second frame number, the T_Frame represents a length of a frame cycle of the frame time clock, and the D_Frame represents a frame time clock drift of the frame time clock.

14. The method of claim 13, further comprising:

before the step of calculating the second GNSS time, updating the value of D_Frame.

15. The method of claim 11, further comprising:

calculating the second GNSS time according to a frame time clock drift of the frame time clock, the first GNSS time, the frame number FN1, and the frame number FN2.

16. A apparatus for obtaining Global navigation Satellite System (GNSS) time in a GNSS receiver, the apparatus comprising:

at least one processing module arranged to receive a first frame number of a frame time clock of a cellular network at a first time point, obtain a first GNSS time corresponding to the first frame number, receive a second frame number of the frame time clock at a second time point, and obtain a second GNSS time corresponding to an associated clock value of a clock signal of the GNSS receiver according to the first GNSS time, the first frame number, and the second frame number.

17. The apparatus of claim 16, wherein one of the at least one processing module controls at least a portion of the GNSS receiver to enter a power saving mode during a time period between the first time point and the second time point.

18. The apparatus of claim 16, wherein one of the at least one processing module calculates the second GNSS time by the following equation:

C2=C1+(FN2−

FN1)*T_Frame*(1−

D_Frame);

wherein C1 represents the first GNSS time, C2 represents the second GNSS time, FN1 represents the first frame number, the FN2 represents the second frame number, the T_Frame represents a length of a frame cycle of the frame time clock, and the D_Frame represents a frame time clock drift of the frame time clock.

19. The apparatus of claim 18, before calculating the second GNSS time, one of the at least one processing module updates the value of D_Frame.

20. The apparatus of claim 16, wherein one of the at least one processing modules calculates the second GNSS time according to a frame time clock drift of the frame time clock, the first GNSS time, the frame number FN1, and the frame number FN2.