Systems and methods for signal acquisition using predicted environmental context
View Patent ↗This disclosure involves methods and systems for a GNSS receiver to ascertain its environmental context and subsequently adjust the signal processing and search algorithms to provide improved acquisition. A rapid pre-scan is performed to determine the presence of relatively strong signals. If no satellites are found in the initial pre-scan, successively more sensitive searches are conducted until at least one satellite is acquired. The information from these pre-scans is used to predict the environmental context of the receiver and correspondingly tailor the parameters for the remaining search operations.
1. A method for acquiring signals with a mobile receiver based on predicted environmental context, the method comprising, with the receiver:
providing a plurality of search steps wherein each search step comprises a correlation operation having a total integration time and is configured to correspond to a distinct signal level ranging from relatively stronger to relatively weaker such that the total integration time of each search step is greater than the total integration time of a preceding search step, wherein the plurality of search steps includes a first search step having less sensitivity than a second search step having less sensitivity than a third search step;
performing a pre-scan search at successive search steps from a first pre-scan search step to a last pre-scan search step within the plurality of search steps until at least one satellite is acquired;
performing a context awareness decision based, at least in part, on how many satellites were acquired and the configuration of the last pre-scan search step;
setting an initial scan search step from the plurality of search steps based, at least in part, on the context awareness decision, wherein setting the initial scan search step comprises setting the initial scan search step to a search step within the plurality of search steps having a sensitivity greater than the last pre-scan search step; and
performing a scan search to identify unacquired satellites using the initial scan search step wherein the initial scan search step has a greater sensitivity than the last pre-scan search step and wherein performing a scan search includes performing the search at successive search steps starting at the initial scan search step.
2. The method of claim 1 , further comprising calculating a navigational solution when at least four satellites have been acquired.
3. The method of claim 1 , wherein the pre-scan search returns a plurality of satellite acquisitions at a search step corresponding to a relatively stronger signal and wherein setting the initial scan search step comprises setting the initial scan search step to the first search step.
4. The method of claim 1 , wherein the pre-scan search returns no satellite acquisitions at a search step corresponding to a relatively stronger signal and wherein setting the initial scan search step comprises setting the initial scan search step to the second search step.
5. The method of claim 1 , wherein the pre-scan search returns only one satellite acquisition at a search step corresponding to a relatively stronger signal and wherein setting the initial scan search step comprises setting the initial scan search step to the third search step.
6. The method of claim 5 , wherein the third search step is a last search step of the plurality of search steps.
7. The method of claim 5 , further comprising performing a supplemental search scan at a fourth search step, wherein the fourth search step has a sensitivity greater than the last pre-scan search step and less than a last search step, acquiring a satellite in the supplemental search scan, decoding bit edge timing information from the satellite acquired in the supplemental search scan, and performing the scan search at the third search step using the bit edge timing information.
8. The method of claim 1 , further comprising increasing the sensitivity of a subsequent search step when fewer than four satellites are acquired during the scan search using the initial scan search step.
9. The method of claim 8 , further comprising determining bit edge timing information when required for the increased sensitivity subsequent search step.
10. A mobile receiver for acquiring signals based on predicted environmental context, wherein the receiver is configured with a plurality of search steps, wherein each search step comprises a correlation operation having a total integration time and is configured to correspond to a distinct signal level ranging from relatively stronger to relatively weaker such that the total integration time for each search step is greater than the total integration time for a preceding search step, wherein the plurality of search steps includes a first search step having less sensitivity than a second search step having less sensitivity than a third search step and wherein the receiver is configured to:
perform a pre-scan search at successive search steps from a first pre-scan search step to a last pre-scan search step within the plurality of search steps until at least one satellite is acquired;
perform a context awareness decision based, at least in part, on how many satellites were acquired and the configuration of the last pre-scan search step;
set an initial scan search step from the plurality of search steps based, at least in part, on the context awareness decision, wherein the receiver is configured to set the initial scan search step by setting the initial scan search step to a search step within the plurality of search steps having a sensitivity greater than the last pre-scan search step; and
perform a scan search to identify unacquired satellites using the initial scan search step wherein the initial scan search step has a greater sensitivity than the last pre-scan search step and wherein the receiver is configured to perform the scan search by performing the search at successive search steps starting at the initial scan search step.
11. The mobile receiver of claim 10 , wherein the receiver is further configured to calculate a navigational solution when at least four satellites have been acquired.
12. The mobile receiver of claim 10 , wherein the receiver is configured to set the initial scan search step to the first search step when the pre-scan search returns a plurality of satellite acquisitions at a search step corresponding to a relatively stronger signal.
13. The mobile receiver of claim 10 , wherein the receiver is configured to set the initial scan search step to the second search step when the pre-scan search returns no satellite acquisitions at a search step corresponding to a relatively stronger signal.
14. The mobile receiver of claim 10 , wherein the receiver is configured to set the initial scan search step to the third search step when the pre-scan search returns only one satellite acquisition at a search step corresponding to a relatively stronger signal.
15. The mobile receiver of claim 14 , wherein the third search step is a last search step of the plurality of search steps.
16. The mobile receiver of claim 14 , wherein the receiver is further configured to:
perform a supplemental search scan at a fourth search step, wherein the fourth search step has a sensitivity greater than the last pre-scan search step and less than a last search step of the plurality of search steps;
acquire a satellite in the supplemental search scan,
decode bit edge timing information from the satellite acquired in the supplemental search scan; and
perform the scan search at the third search step using the bit edge timing information.
17. The mobile receiver of claim 10 , wherein the receiver is further configured to increase the sensitivity of a subsequent search step when fewer than four satellites are acquired during the scan search using the initial scan search step.
18. The mobile receiver of claim 17 , wherein the receiver is further configured to determine bit edge timing information when required for the increased sensitivity subsequent search step.