Algorithm design and simulation test for software GNSS receiver

The GNSS software receiver principle is introduced based on its architecture. Signal correlator and its work flow are designed firstly in this paper. Parallel code searching strategy using FFT (fast Fourier transform) is discussed in detail, and the phase discriminator, frequency discriminator in the carrier loop for signal tracking are also analyzed. Various error sources are discussed such as the clock error, tropospheric error model, where a simple equivalent model for the later one is proposed for the software receiver. The implementation steps based on least square method is also proposed. Simulation result shows that the proposed signal acquisition strategy and the tracking method work well, including the parallel code searching and the PLL (phase lock loop) algorithm supported by DLL (delay lock loop) and FLL (frequency lock loop). In addition, the single point positioning result meets the demand using the least square method with the considerations of clock error, tropospheric error, ionospheric error and the earth rotation introduced error.