Abstract: The mathematical models of intermediate frequency and zero intermediate global navigation satellite system (GNSS) signal are deduced. The pre-detection GNSS signal model is further proposed. A unified method is proposed to add noise for the three signal models. The theoretical analysis and simulation results show that the simulation platforms based on the three model are equivalent. The pre-detection simulation platform reduces the data sampling rate to about 1 000 Hz and reduces the amount of computation, and the simulation efficiency is improved. A frequency tracking scheme based on Viterbi algorithm is proposed, in which the frequency is estimated by traceback approach. This tracking scheme is verified on the pre-detection simulation platform and the results show that the proposed method can track GNSS signal for a carrier-to-noise ratio of 10 dBHz in static scene.

Key words: global navigation satellite system , signal simulation, pre-detection, Viterbi , frequency tracking