Real-Time Gnss Software Receiver

A satellite navigation system (like GPS) allows an user to determine its own position everywhere and anytime on Earth. The main issue is to obtain and decode the transmitted information and to estimate accurately the TOA of the signals as they lie below the thermal noise floor. A technique called spread-spectrum has been applied for the transmission of these signals that distributes a narrow-band signal over a large bandwidth with the help of spreading codes. In the receiver, these known sequences (one for every satellite) are re-generated and correlated with the incoming signal. As the satellites are moving, the signals undergo additionally a Doppler frequency shift that also has to be compensated in the receiver. These correlation processes require a huge number of operations which make them difficult to be executed in software. The aim of this thesis is to develop and implement a real-time software receiver on a general purpose microprocessor. This includes the development and the implementation of a new signal processing baseband architecture. The requirements and the performance are finally evaluated with simulated and real signals.