Satellite Clock Prediction

• US 20080238765A1
• Filed: 03/30/2007
• Published: 10/02/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Inventors: Garin, Lionel J., Zhang, Gengsheng, Wan, Marlene, Phatak, Makarand S.
• Granted Patent: US 7,839,331 B2
• Time in Patent Office: Days
• US Class Current: 342/357.01
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• 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 19/27 creating, predicting or correcting ephemeris or almanac data within the receiver

Abstract

Devices and methods are described for determining position information without broadcast ephemeris data for a spanned time period using predictions of future satellite states. These predictions include predictions of satellite clock bias. During the spanned time period, broadcast ephemeris is received such that a broadcast-ephemeris-derived satellite clock bias may be determined. The predictions of satellite clock bias subsequent to the receipt of the broadcast ephemeris may then be corrected based upon the broadcast-ephemeris-derived satellite clock bias.

Claims

1. A method for determining a position of a client device, comprising:

receiving sets of parameters over a first communication channel, wherein the sets of parameters span a period of time, and wherein each set of parameters is representative of predicted satellite states for a particular sub-period of time within the spanned period of time such that a first set of parameters is representative of the predicted satellite states in a first sub-period of time, a second set of parameters is representative of the predicted satellite states for a subsequent second sub-period of time, and so on, and wherein the sets of parameters include predictions of satellite clock biases;

during the spanned period of time, receiving broadcast ephemeris over a second communication channel at a given time, the broadcast ephemeris including a broadcast ephemeris clock bias, wherein a subset of the parameters correspond to sub-periods of time subsequent to the given time; and

modifying the predictions of satellite clock biases in the subset of parameters based upon the broadcast ephemeris clock bias.

2. The method of claim 1, further comprising:

at a time subsequent to the given time, selectively reconstructing a reconstructed satellite state in the client device using the subset of parameters, wherein the reconstructed satellite state includes the modified prediction of satellite clock bias; and

determining the position of the client device using the reconstructed satellite state.

3. The method of claim 1, further comprising:

based upon the received broadcast ephemeris, calculating a broadcast-ephemeris-derived satellite position; and

comparing the broadcast-ephemeris-derived satellite position to a satellite position derived from the received sets of parameters to determine a validity of the received sets of parameters.

4. The method of claim 3, wherein comparing the broadcast-ephemeris-derived satellite position to a satellite position derived from the received sets of parameters comprises comparing a difference between the broadcast-ephemeris-derived satellite position and the satellite position derived from the received sets-of-parameters to a distance threshold.

5. The method of claim 4, wherein the distance threshold is 100 meters.

6. The method of claim 1, wherein the spanned period of time has a length of at least seven calendar days.

7. The method of claim 1, wherein the received sets of parameters are Kepler parameters.

8. The method of claim 1, wherein the predictions of satellite clock bias are derived from a polynomial model.

9. The method of claim 8, wherein the polynomial model is a quadratic polynomial model.

10. The method of claim 1, further comprising comparing the broadcast ephemeris clock bias to a corresponding predicted satellite clock bias to determine a validity of the received sets of parameters.

11. The method of claim 1, wherein the received sets of parameters are differentially-compressed Kepler parameters.

12. A device, comprising:

a state reconstructor that selectively reconstructs a current satellite state based upon predictions of satellite states, wherein the predictions of satellite states span a period of time and include predictions of satellite clock bias, the state reconstructor being configured to modify the predictions of satellite clock bias based upon received broadcast ephemeris; and

at least one signal processor that uses the at least one reconstructed satellite state to acquire a satellite signal.

13. The device of claim 12, further comprising a satellite state predictor operable to provide the predictions of satellite states using broadcast ephemeris previously received from a plurality of satellites.

14. The device of claim 12, further comprising a communication system operable to receive the predictions of satellite states.

15. The device of claim 14, wherein the predictions of satellite states comprise Kepler parameters.

16. A device, comprising:

a memory for storing predictions of satellite states, wherein the predictions of satellite states comprises sets of predictions spanning a period of time such that a first set of predictions corresponds to satellite states for a first sub-period of time in the spanned period, a second set of predictions corresponds to satellite states for a second subsequent sub-period of time in the spanned period, and so on, and wherein the prediction of satellite states are derived from previously-received broadcast ephemeris;

means for reconstructing satellite states at any given time during the spanned period based upon the stored predictions of satellite states;

means for modifying the stored predictions of satellite states based upon broadcast ephemeris received during the spanned period; and

a location determination system adapted to use the reconstructed satellite states in a determination of a location for the device at the given time if current broadcast ephemeris is unavailable at the given time.

17. The device of claim 16, wherein the means for modifying the stored predictions of satellite states modifies predictions of satellite clock bias based upon a broadcast-ephemeris-derived satellite clock bias from the received broadcast ephemeris.

18. The device of claim 16, wherein the stored predictions comprise parameters derived from predictions of satellite states.

19. The device of claim 18, wherein the parameters are Kepler parameters.

20. The device of claim 18, wherein the parameters are Chebyshev parameters.