A novel PN-code acquisition method based on local frequency folding for BeiDou system

Large Doppler offset that exists in high dynamic environment could cause serious problem to the acquisition of navigation satellite signals. To ensure acceptable detection probabilities, frequency space has to be divided, which would result in complicated acquisition structure and long acquisition time, especially in low SNR. In addition, Chinese BeiDou system is currently under development for global operation. Therefore, the research on acquisition methods for BeiDou system has been experiencing a new upsurge. This paper proposes a new local frequency folding method (LFF) by folding all frequency cells together, to reduce the frequency search procedure and ease the acquisition burden. Also, by analyzing the performance of LFF, it is obtained that the degradation of detection performance could be compensated by coherent integration. Preliminary results show that the proposed algorithm could performance obviously better than other unfolding methods, with respect to the detection probability and mean acquisition time. Furthermore, the advantage could become large when the folding number increases.