Autonomous data aided GPS signal acquisition method and system

A method of GPS signal acquisition from a plurality of broadcasted GPS signals comprising the steps of:

• receiving the plurality of broadcasted GPS signals and providing a digitized signal dependent thereon;
• correlating a first portion of the digitized signal to a code replica and determining a real-time code phase delay;
• determining a Time Of Arrival (TOA) of a deterministic portion of the digitized signal, dependent on the determined real-time code phase delay;
• determining a capture start time dependent on the determined TOA;
• deriving a real-time code phase delay prediction dependent on the determined real-time code phase delay and Time Of Arrival (TOA) and identifying a reduced code replica search space dependent thereon;
• capturing a second portion of the digitized signal into a memory commencing coincident with the determined capture start time;
• and
• extracting the second portion of the digitized signal from the memory and, correlating the extracted signal to the reduced code replica search space and determining an off-line code phase delay dependent thereon.

A Global Positioning System (GPS) receiver comprising:

• a GPS front-end for receiving a plurality of broadcasted GPS signals and providing a digitized signal dependent thereon;
• a first correlator operatively couplable to the front-end for correlating a first portion of the digitized signal to a code replica and determining a real-time code phase delay, then determining a capture start time dependent on the determined real-time code phase delay;
• and
• a memory operably coupled to the front-end for capturing a second portion of the digitized signal into a memory commencing coincident with the determined capture start time, and wherein the first correlator is operably couplable to the memory for extracting the second portion of the digitized signal from the memory and correlating the extracted signal to the code replica and determining an off-line code phase delay.

A method of GPS signal acquisition from a plurality of broadcasted GPS signals in a GPS receiver with a receiver front-end and a computational back-end, the method comprising the steps of:

• powering on the GPS receiver front-end;
• receiving the plurality of broadcasted GPS signals and providing a digitized signal dependent thereon;
• correlating a first portion of the digitized signal to a code replica and Doppler replica and determining code phase delays from at least three satellites comprising at least one real-time code phase delay;
• determining a first position fix dependent on each of the code phase delays and satellite broadcast ephemeris data extracted from the first portion of the digitized signal;
• determining a local precise time dependent on the determined first position fix;
• determining a satellite signal propagation time for at least one satellite of the at least three satellites;
• determining a capture start time dependent on the determined local precise time and the satellite signal propagation time;
• determining loss of correlation lock;
• powering off the GPS receiver front-end for a period of time until the determined capture start time;
• powering on the GPS receiver front-end and capturing a second portion of the digitized signal into memory commencing coincident with the determined capture start time;
• powering off the GPS receiver front-end;
• extracting the second portion of the digitized signal from the memory and correlating the extracted signal to the code replica, Doppler replica, and a predicted 50 BPS navigation data replica and determining an off-line code phase delay dependent thereon for each satellite signal contained in the second portion of the digitized signal in memory;
• and
• computing a second position fix dependent on at least three code phase delays including the determined off-line code phase delay.

A method of GPS signal acquisition from a plurality of broadcasted GPS signals in a GPS receiver with a receiver front-end and a computational back-end, the method comprising the steps of:

• receiving the plurality of broadcasted GPS signals and providing a digitized signal dependent thereon;
• correlating a first portion of the digitized signal to a code replica and determining a real-time code phase delay;
• determining a Time Of Arrival (TOA) of a deterministic portion of the digitized signal, dependent on the determined real-time code phase delay;
• determining a capture start time dependent on the determined TOA;
• capturing a second portion of the digitized signal into a memory;
• powering off the GPS receiver front-end for a period of time until the determined capture start time;
• extracting the second portion of the digitized signal from the memory and correlating the extracted signal to a code replica and determining a first off-line code phase delay estimate dependent thereon using a non-coherent integration method;
• identifying a reduced code replica search space dependent on the first off-line code phase delay estimate;
• powering on the GPS receiver front-end and capturing a third portion of the digitized signal into memory commencing coincident with the determined capture start time;
• and
• extracting the third portion of the digitized signal from the memory and correlating the extracted signal to the reduced code replica search space and determining a second off-line code phase delay dependent thereon.