GPS receiver having a fast time to first fix

A global positioning system (GPS) receiver, comprising:

• a correlator for despreading a GPS signal including a GPS bit stream and providing said GPS bit stream;
• a clock for providing an approximate local clock time;
• a processor including a program memory including an executable code for receiving said GPS bit stream and executing said executable code;
• and
• a Doppler correction code for inclusion in said executable code for improving an accuracy of said local clock time by adjusting said local clock time according to a difference between a calculated Doppler frequency shift and a measured Doppler frequency shift for said GPS signal and providing a Doppler-corrected local time.

A method in a global positioning system (GPS) receiver for receiving a spread spectrum GPS signal including a GPS bit stream including a GPS message synchronized to a GPS time, comprising steps of:

• despreading said GPS signal for providing said GPS bit stream;
• generating an approximate local clock time;
• retrieving information for an expected GPS message from a memory;
• generating a replica bit stream including said expected GPS message having a timing based on said local clock time;
• and
• aligning said local clock time to said GPS time for providing a GPS-based clock time by adjusting said local clock time to synchronize said replica bit stream to said GPS bit stream.

A method in a global positioning system (GPS) receiver for receiving a spread spectrum GPS signal including a GPS bit stream including a GPS message synchronized to a GPS time, comprising steps of:

• despreading said GPS signal for providing said GPS bit stream;
• generating an approximate local clock time;
• and
• improving an accuracy of said local clock time by adjusting said local clock time according to a difference between a calculated Doppler frequency shift and a measured Doppler frequency shift for said GPS signal and providing a Doppler-corrected local time.