Patent ID: 8773305

Claim:
A global positioning system (GPS) carrier-tracking method comprising the following steps: acquiring a GPS signal from a satellite with a receiver, wherein the signal acquiring is performed while the receiver is in an acquisition mode and when the signal strength of the GPS signal at the receiver is equal to or above a carrier/noise (C/N 0 ) threshold; tracking the carrier frequency of the GPS signal with the receiver, wherein the tracking is performed while the receiver is in a tracking mode and when the signal strength of the GPS signal at the receiver is above the C/N 0 threshold; recording carrier frequency values while the receiver is in tracking mode; exiting tracking mode and predicting a current Doppler shift based on the recorded values when the signal strength of the GPS signal at the receiver drops below the C/N 0 threshold for a time period t; and resuming, without the receiver re-entering acquisition mode, tracking of the GPS signal with the receiver after time period t and once the signal strength of the GPS signal is again equal to or above the C/N 0 threshold, wherein the resumed tracking is based on the predicted Doppler shift.