Satellite clock prediction
View Patent ↗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.
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 corresponding sub-period of time within the spanned period of time, 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.