Method and system for reducing autonomous time to fix a multi-standard GNSS receiver
A multi-standard GNSS receiver, handle different global navigation satellite systems (GNSSs), determines with respect to a current time instant, the earliest broadcast timing based on corresponding satellite broadcast cycles for satellites in the different GNSSs. The multi-standard GNSS receiver acquires broadcast ephemeris at the determined earliest broadcast timing to determine its own first position. A search order is determined based on the corresponding satellite broadcast cycles and the current time instant. The multi-standard GNSS receiver may selectively utilize appropriate satellite receivers such as the GPS receiver and the GLONASS receiver to search for satellite signals based on the determined search order. Channels for different GNSSs are scanned to identify transmitting satellites based on the corresponding satellite broadcast cycles for ephemeris downloading. The satellite search is prioritized by comparing the current time instant with the corresponding satellite broadcast cycles.
1. A method for processing signals in a multi-standard global navigation satellite system (GNSS) receiver associated with a plurality of global navigation satellite systems, the method comprising:
determining a search order for a plurality of satellites included in the plurality of global navigation satellite systems based on a current time instant and satellite broadcast cycles of the plurality of satellites;
searching among the plurality of satellites in accordance with the determined search order to identify a satellite from among the plurality of satellites from which ephemeris data is to be received based on the current time instant and on the satellite broadcast cycles;
acquiring the ephemeris data from the identified satellite; and
determining a position of the GNSS receiver based on the acquired ephemeris data.
2. The method of claim 1 , wherein the determining the search order comprises:
searching for signals from the plurality of satellites based on the satellite broadcast cycles.
3. The method of claim 2 , wherein the searching for the signals from the plurality of satellites comprises:
searching for the signals utilizing another receiver.
4. The method of claim 1 , further comprising:
scanning a plurality of channels associated with the plurality of satellites to enable the searching.
5. The method of claim 1 , wherein the searching comprises:
determining, with respect to the current time instant, an earliest broadcast time when the ephemeris data can be received from the identified satellite.
6. The method of claim 1 , wherein the searching comprises:
providing a guard band time to ensure adequate time for searching the plurality of satellites.
7. The method of claim 6 , wherein the identifying the satellite further comprises:
comparing the current time instant and the guard band time to a time associated with the satellite broadcast cycles to enable the searching.
8. The method of claim 1 , further comprising:
prioritizing a first global navigation satellite system, from among the plurality of global navigation satellite systems, over a second global navigation satellite system, from among the plurality of global navigation satellite systems, based on a determination that a next broadcast cycle associated with a first satellite included in the first global navigation satellite system is closer to the current time instant with respect to a next broadcast cycle associated with a second satellite included in the second global navigation satellite system.
9. The method of claim 1 , further comprising:
determining the current time instant based on navigation data acquired from one of the plurality of satellites or from a clock associated with the GNSS receiver.
10. An apparatus for processing signals in a multi-standard global navigation satellite system (GNSS) receiver associated with a plurality of global navigation satellite systems, the apparatus comprising:
a processor configured to:
determine a search order for a plurality of satellites included in the plurality of global navigation satellite systems based on a current time instant and satellite broadcast cycles of the plurality of satellites;
search among the plurality of satellites in accordance with the determined search order to identify a satellite from among the plurality of satellites from which ephemeris data is to be received based on the current time instant and on the satellite broadcast cycles;
acquire the ephemeris data from the identified satellite; and
determine a position of the GNSS receiver based on the acquired ephemeris data.
11. The apparatus of claim 10 , wherein the processor is configured to search for signals from the plurality of satellites based on the satellite broadcast cycles to determine the search order.
12. The apparatus of claim 11 , wherein the processor is configured to utilize another receiver to search for the signals.
13. The apparatus of claim 10 , wherein the processor is further configured to:
scan a plurality of channels associated with the plurality of satellites to enable the processor to search from among the plurality of satellites.
14. The apparatus of claim 10 , wherein the processor is further configured to determine, with respect to the current time instant, an earliest broadcast time when the ephemeris data can be received from the identified satellite.
15. The apparatus of claim 10 , wherein the processor is further configured to provide a guard band time to ensure adequate time to search the plurality of satellites.
16. The apparatus of claim 15 , wherein the processor is configured to compare the current time instant and the guard band time to a time associated with the satellite broadcast cycles to enable the processor to search the plurality of satellites.
17. The apparatus of claim 10 , wherein the processor is configured to prioritize a first global navigation satellite system, from among the plurality of global navigation satellite systems, over a second global navigation satellite system, from among the plurality of global navigation satellite systems, based on a determination that a next broadcast cycle associated with a first satellite included in the first global navigation satellite system is closer to the current time instant with respect to a next broadcast cycle associated with a second satellite included in the second global navigation satellite system.
18. The apparatus of claim 10 , wherein the processor is further configured to determine the current time instant based on navigation data acquired from one of the plurality of satellites or from a clock associated with the GNSS receiver.
19. The method of claim I, wherein the acquiring comprises:
synchronizing or locking onto the identified satellite to acquire the ephemeris data from the identified satellite.
20. The apparatus of claim 10 , wherein the processor is further configured to synchronize or lock onto the identified satellite to acquire the ephemeris data from the identified satellite.