Search

早大学位記番号:新8232

As multipath is one of the dominating error sources for high accuracy Global Navigation Satellite System (GNSS) applications, multipath mitigation approaches are employed to minimize this hazardous error in receivers. Binary offset carrier modulation (BOC), as a modernized signal structure, is adopted to achieve significant enhancement. However, because of its multi-peak autocorrelation function, conventional multipath mitigation techniques for binary phase shift keying (BPSK) signal would not be optimal. Currently, non-parametric and parametric approaches have been studied specifically aiming at multipath mitigation for BOC signals. Non-parametric techniques, such as Code Correlation Reference Waveforms (CCRW), usually have good feasibility with simple structures, but suffer from low universal applicability for different BOC signals. Parametric approaches can thoroughly eliminate multipath error by estimating multipath parameters. The problems with this category are at the high computation complexity and vulnerability to the noise. To tackle the problem, we present a practical parametric multipath estimation method in the frequency domain for BOC signals. The received signal is transferred to the frequency domain to separate out the multipath channel transfer function for multipath parameter estimation. During this process, we take the operations of segmentation and averaging to reduce both noise effect and computational load. The performance of the proposed method is evaluated and compared with the previous work in three scenarios. Results indicate that the proposed averaging-Fast Fourier Transform (averaging-FFT) method achieves good robustness in severe multipath environments with lower computational load for both low-order and high-order BOC signals.

Along with the advancement of the process of GNSS modernization, BOC modulation has been widely used. Tough it has a certain anti-multipath capability, reflected BOC signals with the large amplitude and short delay cannot be suppressed. Additionally, some of the traditional multipath suppression algorithms are no longer applicable for the BOC signals, so the multipath mitigation algorithms for BOC signals need to be studied further. CCRW is a kind of anti-multipath algorithm for BOC modulation, but it unsuitable for BOC signals with odd coefficient. In order to overcome its shortcoming, this paper proposes an improved CCRW algorithm for BOC signals with odd modulation coefficient, and simulation results prove the effectiveness of the proposed algorithm.