UTC time offset estimation at a GNSS receiver
Techniques are provided to quickly estimate a temporal shift of a GPS signal based on an analysis of a GLONASS signal. The shift can be a result of applied leap-second adjustments affecting GLONASS signals but not GPS signals. By identifying this shift, GPS and GLONASS signals can be considered together in order to estimate locations. The temporal shift can be determined, e.g., by estimating a separation between a GPS-signal frame feature (e.g., frame onset) and a GLONASS-signal frame feature (e.g., frame onset), or identifying coinciding frame features (e.g., a GPS-signal subframe coinciding with a GLONASS-signal string number). The techniques allow the temporal shift to be estimated based on an analysis of just a portion of the GPS-signal and GLONASS-signal frames, such that a speed of location estimations can be improved.
1. A method for estimating cumulative leap-second adjustments indicating a combined total of implemented leap-second adjustments in a Global Navigation Satellite System (GLONASS) time, the method comprising:
accessing, by an electronic device, a GLONASS signal;
accessing, by the electronic device, a Global Position System (GPS) signal or a GPS time;
determining, by the electronic device, a frame-related feature of the GLONASS signal coinciding in time with a frame related feature of the accessed GPS signal or being associated with the accessed GPS time;
estimating, by the electronic device, the cumulative leap-second adjustments based on analyzing an alignment of the determined frame-related feature of the GLONASS signal with respect to said GPS signal or based on the accessed GPS time corresponding to the determined frame-related feature of the GLONASS signal; and
adjusting a time of the electronic device using the estimated cumulative leap-second adjustments.
2. The method of claim 1 , wherein the frame-related feature of the GLONASS signal comprises a string number of the GLONASS signal temporally coincident with an element of a frame of the GPS signal or a specific subframe in said GPS signal.
3. The method of claim 2 , wherein the frame-related feature of the GLONASS signal comprises a string number and an intra-string location of the GLONASS signal temporally coincident with a preamble of a subframe in the GPS signal.
4. The method of claim 1 , further comprising constraining the estimate of the cumulative leap-second adjustments based on a maximum number.
5. The method of claim 1 further comprising adjusting a time associated with said GPS signal based on the estimated cumulative leap-second adjustments.
6. A non-transitory computer-readable medium comprising processor-executable instructions configured to cause a processor to:
access a GLONASS signal;
access a Global Position System (GPS) signal or a GPS time;
determine a frame-related feature of the GLONASS signal coinciding in time with a frame related feature of the accessed GPS signal or being associated with the accessed GPS time;
estimate the cumulative leap-second adjustments based on analyzing an alignment of the determined frame-related feature of the GLONASS signal with respect to said GPS signal or based on the accessed GPS time corresponding to the determined frame-related feature of the GLONASS signal; and
adjusting a time of an electronic device using the estimated cumulative leap-second adjustments.
7. The non-transitory computer-readable medium of claim 6 , wherein the frame-related feature of the GLONASS signal comprises a string number of the GLONASS signal temporally coincident with an element of a frame of the GPS signal or a specific subframe in said GPS signal.
8. The non-transitory computer-readable medium of claim 7 , wherein the frame-related feature of the GLONASS signal comprises a string number and an intra-string location of the GLONASS signal temporally coincident with a preamble of a subframe in the GPS signal.
9. The non-transitory computer-readable medium of claim 6 , wherein the processor-executable instructions are further configured to cause the processor to constrain the estimate of the cumulative leap-second adjustments based on a maximum number.
10. The non-transitory computer-readable medium of claim 6 , wherein the processor-executable instructions are further configured to cause the processor to adjust a time associated with said GPS signal based on the estimated cumulative leap-second adjustments.
11. A system for estimating cumulative applied leap-second adjustments indicating a combined total of implemented leap-second adjustments in a Global Navigation Satellite System (GLONASS) time, the system comprising:
means for accessing a GLONASS signal;
means for accessing a Global Position System (GPS) signal or a GPS time;
means for determining a frame-related feature of the GLONASS signal coinciding in time with a frame-related feature of the accessed GPS signal or being associated with the accessed GPS time;
means for estimating cumulative leap-second adjustments based on analyzing an alignment of the determined frame-related feature of the GLONASS signal with respect to said GPS signal or based on the accessed GPS time corresponding to the determined frame-related feature of the GLONASS signal; and
means adjusting a time of an electronic device using the estimated cumulative leap-second adjustments.
12. The system of claim 11 , further comprising:
means for accessing said GPS signal;
means for determining said frame-related feature of the GPS signal; and
means for comparing the frame-related feature of the GLONASS signal to the frame-related feature of the GPS signal.
13. The system of claim 12 , wherein the means for comparing the frame-related feature of the GLONASS signal to the frame-related feature of the GPS signal comprises a clock, such that a coincidence between the frame features can be detected.
14. The system of claim 12 , wherein the means for accessing the GLONASS signal and the means for accessing the GPS signal comprises a single receiver configured to receive signals from GLONASS satellites and GPS satellites.
15. The system of claim 11 , wherein the frame-related feature of the GLONASS signal comprises a string number of the GLONASS signal temporally coincident with an element of a frame of the GPS signal or a specific subframe in said GPS signal.
16. The system of claim 15 , wherein the frame-related feature of the GLONASS signal comprises a string number and an intra-string location of the GLONASS signal temporally coincident with a preamble of a subframe in the GPS signal.
17. A device for estimating cumulative leap-second adjustments indicating a combined total of implemented leap-second adjustments in a Global Navigation Satellite System (GLONASS) time comprising:
a clock;
one or more receivers configured to receive a GLONASS signal from a GLONASS satellite and to receive a Global Positioning System (GPS signal from a GPS satellite
a non-transitory computer-readable medium; and
a processor in communication with the non-transitory computer-readable medium, the processor configured to execute processor-executable instructions stored in the non-transitory computer-readable medium, the processor-executable instructions configured to cause a processor to:
access the GLONASS signal;
access the Global Position System (GPS) signal or a GPS time;
determine a frame-related feature of the GLONASS signal coinciding in time with a frame related feature of the accessed GPS signal or being associated with the accessed GPS time;
estimate the cumulative leap-second adjustments based on analyzing an alignment of the determined frame-related feature of the GLONASS signal with respect to said GPS signal or based on the accessed GPS time corresponding to the determined frame-related feature of the GLONASS signal; and
adjust a time of the clock using the estimated cumulative leap-second adjustments.
18. The device of claim 17 , wherein the frame-related feature of the GLONASS signal comprises a string number of the GLONASS signal temporally coincident with an element of a frame of the GPS signal or a specific subframe in said GPS signal.
19. The device of claim 18 , wherein the frame-related feature of the GLONASS signal comprises a string number and an intra-string location of the GLONASS signal temporally coincident with a preamble of a subframe in the GPS signal.
20. The device of claim 17 , wherein the processor-executable instructions are further configured to cause the processor to constrain the estimate of the cumulative leap-second adjustments based on a maximum number.
21. The device of claim 17 , wherein the processor-executable instructions are further configured to cause the processor to adjust a time associated with said GPS signal based on the estimated cumulative leap-second adjustments.