Multipath Mitigation Method Research Articles

Channel modelling in complex urban environments for testing multipath mitigation methods enhanced by antenna array

Multipaths are one of the major sources of errors for satellite navigation systems. The goal of this article is to present some advances on propagation channel modelling for GNSS mobile users and to show how GNSS receiving algorithms are sensitive to the modelling of the channel. Two channel characteristics are analysed in the paper: the resolution of the environment level of detail, and the resolution of the channel, meaning the number of significant echoes in the tapped-delay line. Particular focus is made on mitigation techniques using antenna arrays to reject multipath. The influence of the channel model will be then interpreted considering three different types of GNSS receiver algorithms, namely conventional DLL/PLL, beam forming and SAGE/STAP algorithm.

A New Multipath Mitigation Method for GNSS Receivers Based on an Antenna Array

The well-known Space-Alternating Generalized Expectation Maximisation (SAGE) algorithm has been recently considered for multipath mitigation in Global Navigation Satellite System (GNSS) receivers. However, the implementation of SAGE in a GNSS receiver is a challenging issue due to the numerous number or parameters to be estimated and the important size of the data to be processed. A new implementation of the SAGE algorithm is proposed in this paper in order to reach the same efficiency with a reduced complexity. This paper focuses on the trade-off between complexity and performance thanks to the Cramer Rao bound derivation. Moreover, this paper shows how the proposed algorithm can be integrated with a classical GNSS tracking loop. This solution is thus a very promising approach for multipath mitigation.

Antenna array multipath mitigation method in navigation augmentation system

This paper presents the antenna array multipath mitigation method in the satellite navigation augmentation system. The digital receiver with multiple correlators is proposed. The antenna elements of the array each output the raw sampled digital data to every internal receiver channel. The carrier phase of the satellite is correlated out in the channel, and the direction of arrival is estimated, then the digital beamforming is operated to mitigate the multipath. The direction of arrival estimation and the decorrelation method of the correlated signal of the three dimensional array are researched in the paper. A three dimensional spheriform array with current dipoles is proposed, receiving the correlated signals. The three dimensional array proposed is compact with small volume. The linear arrays on X axis, Y axis and Z axis adopt the forward-backward spatial smoothing technique to decorrelate the signals respectively. The direction of arrival is estimated by MUSIC, and there is no matching needed. Distinguish the direct satellite signal by the result of demodulated navigation message. In the simulation, the direction of the direct satellite signal and the multipath signals estimated are used to optimize the weights to apply the beamforming to the desired satellite, and place a null on the estimated multipath direction.

A multi-technique approach for characterizing the SVN49 signal anomaly, part 1: receiver tracking and IQ constellation

A characterization of the signal anomaly of SVN49 is presented. A mathematical model is developed to relate the observed multipath to the internal signal reflection. The analyses provided are based on measurements, which have been collected during a dedicated tracking campaign with a 30-m dish antenna. Data on the L1 and L2 frequency have been collected with four different receivers. In addition, IQ samples have been recorded directly with a spectrum analyzer. The multipath combination of the receiver measurements on L1 and L2 is analyzed to demonstrate the effect of the signal reflections on different correlator spacing. The capability to suppress the signal reflection with receiver multipath mitigation methods is demonstrated. Finally, preliminary estimates of the attenuation, delay, and phase shift over elevation are obtained from an IQ sample analysis.

상관함수의 비대칭성 추정을 통한 다중 경로 오차 제거 기법

Since the muiltipath signal arrives at the GPS receiver later than the line-of-sight signal, the multipath signal makes the shape of the correlation function asymmetric. This paper proposes a multipath mitigation method through asymmetry estimation of the correlation function, in which multiple correlators are utilized. The asymmetry is estimated from correlation values of correlators which have different chip spacings. Based on the estimated asymmetry, the correlation function is modified in order to get a better code tracking performance. Even through the proposed method uses multiple correlators including the narrow correlator, the acquisition performance is not degraded since the number of search cell of the narrow correlator part can be reduced in the algorithm of the proposed method. The simulation results show that the proposed method gives better performance than the generic correlator in multipath environment.