Method and apparatus for initializing an approximate position in a GPS receiver

• US 20050055160A1
• Filed: 08/28/2003
• Published: 03/10/2005
• Est. Priority Date: 08/28/2003
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: King, Thomas M.
• Granted Patent: US 7,463,979 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 5/0063 of measured values, i.e. measurement on base station and position calculation on mobile

Abstract

A method (200, 600) and an apparatus (700) for a wireless portable communication device (102) for determining coarse position information are provided. The wireless portable communication device (102) receives information about a plurality of visible satellites (106, 108, 110), and determines a coarse position of the wireless portable communication device (102) and uncertainty parameters expected at the coarse position, using the determined coarse position and uncertainties to acquire satellites.

Claims

1. A method in a wireless portable communication device for determining an approximate position of the wireless communication device, the method comprising steps of:

receiving information about a plurality of satellites; and

calculating an initial position estimate for determining the approximate position of the wireless portable communication device based upon the information about the plurality of satellites.

2. The method of claim 1, wherein the received information about the plurality of satellites comprises at least one of Doppler assist data, rate-of-change of Doppler data, code phase assist data, elevation angle data, azimuth angle data, integer code phase, and global positioning system bit number, associated with visible satellites of the plurality of satellites.

3. The method of claim 2, wherein the visible satellites comprise at least three visible satellites.

4. The method of claim 2, wherein the wireless portable communication device has orbital information of the plurality of satellites.

5. The method of claim 4, wherein the orbital information of the plurality of satellites comprises at least one of ephemeris data and almanac data of the plurality of satellites.

6. The method of claim 5, wherein the step of calculating the initial position estimate for determining the approximate position of the wireless portable communication device further comprises steps of:

determining current time;

calculating position and velocity vectors of the visible satellites based upon the current time and the orbital information of the plurality of satellites;

calculating a weighted sum of positions of the visible satellites based upon the calculated position vectors of the visible satellites; and

estimating the coarse position of the wireless portable communication device based upon the weighted sum of positions of the visible satellites.

7. The method of claim 6, wherein the step of determining current time is based upon at least one of an internal real time clock of the wireless communication device and an over-the-air message.

8. The method of claim 6, wherein a weight applied to each calculated position vector in calculating the weighted sum of positions of the visible satellites is based upon an elevation angle of the visible satellite associated with the calculated position vector.

9. The method of claim 6, further comprising steps of:

calculating an estimate value consistent with the received information for each of the visible satellites based upon the estimated coarse position of the wireless portable communication device and at least one of the calculated velocity vectors and the calculated position vectors;

calculating a residual based upon a difference between the estimated value and corresponding value in the received information for each of the visible satellites; and

minimizing the residuals.

10. The method of claim 9, wherein minimizing the residuals further comprises steps of:

selecting a plurality of candidate coarse positions by varying the estimated coarse position according to a predetermined condition;

for each of the plurality of candidate coarse positions,

re-calculating an estimate value consistent with the received information for each of the visible satellites based upon the candidate coarse position of the wireless portable communication device and at least one of the calculated velocity vectors and the calculated position vectors;

re-calculating a residual based upon a difference between the estimated value and corresponding value in the received information for each of the visible satellites; and

selecting the candidate coarse position having minimum residuals.

11. A method in a wireless portable communication device for determining uncertainty parameters for the wireless communication device, the method comprising steps of:

receiving information about a plurality of satellites; and

calculating uncertainty parameters based upon the information about the plurality of satellites.

12. The method of claim 11, wherein the calculated uncertainty parameters are at least one of Doppler uncertainties and code phase uncertainties for the wireless portable communication device.

13. The method of claim 12, wherein the received information for the plurality of satellites comprises at least one of Doppler assist data, rate-of-change of Doppler data, code phase assist data, elevation angle data, azimuth angle data, integer code phase, and global positioning system bit number, associated with visible satellites.

14. The method of claim 13, wherein the visible satellites comprise at least three visible satellites.

15. The method of claim 13, wherein the wireless portable communication device has orbital information of the plurality of satellites.

16. The method of claim 15, wherein the orbital information of the plurality of satellites comprises at least one of ephemeris data and almanac data of the plurality of satellites.

17. The method of claim 16, wherein the step of calculating uncertainty parameters based upon the information about the plurality of satellites further comprises steps of:

determining current time;

calculating position and velocity vectors of the visible satellites based upon the current time and the orbital information of the plurality of satellites;

calculating a weighted sum of positions of the visible satellites based upon the calculated position vectors of the visible satellites; and

estimating the coarse position of the wireless portable communication device based upon the weighted sum of positions of the visible satellites.

18. The method of claim 16, wherein the step of determining current time is based upon at least one of an internal real time clock of the wireless communication device and an over-the-air message.

19. The method of claim 17, further comprising steps of:

calculating an estimate value consistent with the received information for each of the visible satellites based upon the estimated coarse position of the wireless portable communication device and at least one of the calculated velocity vectors and the calculated position vectors;

calculating a residual based upon a difference between the estimated value and corresponding value in the received information for each of the visible satellites; and

minimizing the residuals.

20. The method of claim 19, wherein minimizing the residuals further comprises steps of:

selecting a plurality of candidate coarse positions by varying the estimated coarse position according to a predetermined condition;

for each of the plurality of candidate coarse positions,

re-calculating an estimate value consistent with the received information for each of the visible satellites based upon the candidate coarse position of the wireless portable communication device and at least one of the calculated velocity vectors and the calculated position vectors;

re-calculating a residual based upon a difference between the estimated value and corresponding value in the received information for each of the visible satellites; and

selecting the candidate coarse position having minimum residuals.

21. The method claim 20, further comprising a step of calculating the uncertainty parameters for the candidate coarse position having the minimum residuals.

22. A wireless portable communication device comprising:

a receiver configured to receive information about a plurality of satellites; and

a processor coupled to the receiver, the processor configured to calculate coarse position information of the wireless portable communication device based upon the information for the plurality of satellites.

23. The wireless portable communication device of claim 22, wherein the received information for the plurality of satellites comprises at least one of Doppler assist data, rate-of-change of Doppler data, code phase assist data, elevation angle data, azimuth angle data, integer code phase, and global positioning system bit number, associated with visible satellites.

24. The wireless portable communication device of claim 23, wherein the visible satellites comprise at least three visible satellites.

25. The wireless portable communication device of claim 23, further comprising a memory coupled to the processor, the memory configured to store orbital information of the plurality of satellites comprising at least one of ephemeris data and almanac data of the plurality of satellites.

26. The wireless portable communication device of claim 25, wherein the processor further comprises:

a clock configured to determine current time;

a vector calculator coupled to the clock, the receiver, and the memory, the vector calculator configured to calculate position and velocity vectors of the visible satellites based upon the current time and the orbital information of the plurality of satellites;

an average position calculator coupled to the vector calculator, the average position calculator configured to calculate a weighted sum of an average positions of the visible satellites based upon the calculated position vectors of the visible satellites; and

a coarse position estimator coupled to the average position calculator, the coarse position estimator configured to calculate an estimated coarse position of the wireless portable communication device based upon the weighted sum of positions of the visible satellites.

27. The wireless portable communication device of claim 26, wherein the clock further comprises at least one of an internal real time clock configured to provide the current time based upon internal tracked time and an external timer coupled to the receiver, the external timer configured to provide the current time from an over-the-air message received by the receiver.

28. The wireless portable communication device of claim 27, wherein the processor further comprises:

a value estimator coupled to the coarse position estimator, one of the vector calculator and the receiver, and the clock, the value estimator configured to calculate an estimate value consistent with the received information for each of the visible satellites based upon the estimated coarse position of the wireless portable communication device and at least one of the calculated velocity vectors and the calculated position vectors;

a residual calculator coupled to the value estimator and the receiver, the residual calculator configured to calculate residuals based upon differences between the estimated values and corresponding values in the received information about the visible satellites; and

a residual minimizer coupled to the coarse position estimator and the residual calculator,

wherein the residual minimizer varies the estimated coarse position according to a predetermined condition, feeds the varied estimated value to the value estimator; and

selects the varied estimated coarse position having minimum residuals as a coarse position.

29. The wireless portable communication device of claim 28, wherein the processor further comprises an uncertainty parameter calculator coupled to the residual minimizer, the uncertainty parameter calculator configured to calculate at least one of Doppler uncertainties and code phase uncertainties based upon the coarse position.

30. The wireless portable communication device of claim 29, further comprising a satellite signal acquisition module coupled to the vector calculator, the coarse position estimator, and the uncertainty parameter calculator, the satellite signal acquisition module configured to acquire measurements of code phase and Doppler using the determined coarse position and the stored orbital information of the plurality of satellites.

31. The wireless portable communication device of claim 30, further comprising a high accuracy position computation module coupled to the satellite signal acquisition module and the vector calculator, the high accuracy position computation module configured to compute an accurate position of the wireless portable communication device based upon the measurements acquired by the satellite signal acquisition module.