A Method for GNSS Real-time Multipath Mitigation Based on CEEMD-HT Algorithm

Abstract

With the continuous development of the application of satellite positioning and navigation, the demand for high precision positioning is constantly enhanced. The multipath effect is a major error source of the Global Navigation Satellite Systems (GNSS). The measurement errors of the pseudo range and carrier phase caused by the multipath signal affect the positioning accuracy of the receiver seriously. Aiming at multipath suppression, a new method based on the Complementary Ensemble Empirical Mode Decomposition (CEEMD) and Hilbert Transform (HT) is proposed in this paper. In the first step, dynamic real-time multipath model was established. According to the characteristics of the received signal, the dynamic real-time multipath model accords with the two conditions that must be met in the CEEMD algorithm. In the second step, the received signal is decomposed to obtain the Intrinsic Mode Functions (IMF) by CEEMD which has the advantage of improving the prediction accuracy greatly. After that, each IMF is transformed by HT which can automatically complete multiple test of channel delay and calculate the uncertainty of measurement through high speed oscilloscope. In order to determine the exact location of the turning point, the system processes the signal by using the envelope detection method based on Hilbert Transform. Then, the channel delay of the simulator is finally obtained since that the instantaneous frequency, phase and amplitude of each multipath signal can be detected by using the CEEMD-HT algorithm. Finally, the tracking loop is improved by choosing the appropriate IMF as the direct signal. The preliminary simulation results obtained by MATLAB demonstrate that this method can strengthen the performance of GNSS multipath real-time suppression effectively. On the one hand, the new method in this paper can achieve the purpose of real-time suppression of multipath effects. On the other hand, it is capable to raise the channel delay measurement accuracy. Compared with the traditional method, the positioning accuracy is improved by 38.59%.