A Frequency-Domain Multipath Parameter Estimation and Mitigation Method for BOC-Modulated GNSS Signals

Abstract

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.

An improved BOC signal multi-path suppression method

“…If the output of the discriminator is 0, the tracking error of its horizontal coordinates is 0, there is no hybrid multipath signal in the received signal, at this point, only through the output of the phase detector to adjust the frequency of the NC oscillator can be. However, if there is a multipath signal, the output curve of discriminator will be distorted, the curve will no longer pass the zero point, which brings additional multipath error to the tracking process [7].…”

Modeling Multipath Effects on Frequency Locked Loops

“…In this paper, we consider more general cases, such as multipath cases where both LOS and NLOS signals are present simultaneously. Previous researchers have also focused more on hardware studies analyzing the correlator outputs [19,[21][22][23], by contrast we take a theoretical approach to analyze the whole tracking loop, which is the key enabler for us to analyze tracking of events where LOS and NLOS inputs are superposed.…”