METHOD FOR IMPROVING CLOCK ACCURACY IN A WIDE AREA POSITIONING PSEUDOLITE RECEIVER SYSTEM ARCHITECTURE

• US 20150177360A1
• Filed: 12/20/2013
• Published: 06/25/2015
• Est. Priority Date: 12/20/2013
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Bani Hani, Mohammad Shafiq, Bernhardt, Bruce Allen, Sheynman, Arnold
• Granted Patent: US 9,507,010 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/235 Calibration of receiver components

Abstract

A method, apparatus and computer-readable medium for determining a frequency drift of clock of a mobile communication device is disclosed. A first positioning signal, such as M-LMS signals, is received at a first positioning engine of the mobile communication device controlled by the clock. A second positioning signal, such as GNSS signals, is received at a second positioning engine of the mobile communication device controlled by the clock. A first position is determined from the first positioning signal, and a second position is determined from the second positioning signal. A difference between the first position and the second position is determined, and the frequency drift of the clock is determined from the difference between the first position and the second position. The frequency drift determined may be subsequently applied to the clock, and thus enhance the accuracy of M-LMS positioning when GNSS signals are unreliable.

Claims

1. A computer-implemented method of determining a frequency drift of clock of a mobile communication device, comprising:

receiving a first positioning signal at a first positioning engine of the mobile communication device controlled by the clock;

receiving a second positioning signal at a second positioning engine of the mobile communication device controlled by the clock;

determining a first position from the first positioning signal;

determining a second position from the second positioning signal;

determining a difference between the first position and the second position; and

determining the frequency drift from the difference between the first position and the second position.

2. The method of claim 1, further comprising using the determined frequency drift to alter a polynomial curve representing frequency drift of the clock over time.

3. The method of claim 2, further comprising determining the position of the mobile communication device using a frequency drift selected from the altered polynomial curve.

4. The method of claim 2, further comprising:

determining a third position using a third positioning signal received at the first positioning engine and a frequency drift selected from the altered polynomial curve;

determining a fourth position using a fourth positioning signal received at the second position measurement engine and the selected frequency drift;

determining a difference between the third position and the fourth position;

determining a second frequency drift from the difference between the third position and the fourth position; and

altering the polynomial curve using the second frequency drift.

5. The method of claim 1, wherein the first positioning signal comprises a terrestrial-based positioning signal, the first positioning engine comprises a pseudolites positioning engine, the second signal is a Global Navigation Satellite System (GNSS) positioning signal and the second positioning engine comprises a GNSS positioning engine.

6. The method of claim 1, wherein the clock further comprises a temperature-controlled crystal oscillator.

7. The method of claim 1, further comprising obtaining the first signal and the second signal when an environmental parameter measurement indicates that signals having signal strengths suitable for obtaining the first signal and the second signal are available.

8. An apparatus for determining a frequency drift of clock of a mobile communication device, comprising:

a first positioning engine of the mobile communication device configured to determine a first position of the mobile communication device using a terrestrial-based positioning signal received at the mobile communication device;

a second positioning engine of the mobile communication device configured to determine a second position of the mobile communication device using a Global Navigation Satellite System (GNSS) positioning signal received at the mobile communication device;

a clock configured to control the first positioning engine and the second positioning engine; and

a processor configured to;

determine a difference between the first position and the second position, and determine a frequency drift of the clock from the difference between the first position and the second position.

9. The apparatus of claim 8, wherein the processor is further configured to use the determined frequency drift to alter a polynomial curve of frequency drift of the clock over time.

10. The apparatus of claim 9, wherein the processor is further configured to determine a position of the mobile communication device using a frequency drift selected from the altered polynomial curve.

11. The apparatus of claim 9, wherein the processor is further configured to:

receive a third position calculated using a third positioning signal received at the first positioning engine and a frequency drift selected from the altered polynomial curve;

receive a fourth position calculated using a fourth positioning signal received at the second position measurement engine and the selected frequency drift;

determine a difference between the third position and the fourth position;

determining a second frequency drift of the clock from the determined difference between the third position and the fourth position; and

alter the polynomial curve using the second frequency drift.

12. The apparatus of claim 8, wherein the clock further comprises a temperature-controlled crystal oscillator.

13. The apparatus of claim 8, wherein the processor is further configured to obtain the first signal and the second signal when an environmental parameter measurement indicates that suitable signals for obtaining the first signal and the second signal are available.

14. A non-transitory computer-readable medium having stored thereon a set of instructions that when accessed by a processor enable the processor to perform a method for determining a frequency drift of clock in a mobile communication device, the method comprising:

receiving a first positioning signal at a first positioning engine of the mobile communication device controlled by the clock;

receiving a second positioning signal at a second positioning engine of the mobile communication device controlled by the clock;

determining a first position from the first positioning signal;

determining a second position from the second positioning signal;

determining a difference between the first position and the second position;

determining the frequency drift from the difference between the first position and the second position.

15. The computer-readable medium of claim 14, wherein the method further comprises using the determined frequency drift to alter a polynomial curve representing frequency drift of the clock over time.

16. The computer-readable medium of claim 15, wherein the method further comprises determining the position of the mobile communication device using a frequency drift selected from the altered polynomial curve.

17. The computer-readable medium of claim 15, wherein the method further comprises:

determining a third position using a third positioning signal received at the first positioning engine and a frequency drift selected from the altered polynomial curve;

determining a fourth position using a fourth positioning signal received at the second positioning engine and the selected frequency drift;

determining a difference between the third position and the fourth position;

determining a second frequency drift from the difference between the third position and the fourth position; and

altering the polynomial curve using the second frequency drift.

18. The computer-readable medium of claim 14, wherein the first positioning signal comprises a terrestrial-based positioning signal, the first positioning engine comprises a pseudolites positioning engine, the second signal is a Global Navigation Satellite System (GNSS) positioning signal and the second positioning engine comprises a GNSS positioning engine.

19. The computer-readable medium of claim 14, wherein the clock further comprises a temperature-controlled crystal oscillator.

20. The computer-readable medium of claim 14, further comprising obtaining the first signal and the second signal when a received environmental parameter measurement indicates that signals having suitable strengths for obtaining the first signal and the second signal are available.