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Analysis of Multipath and CW Interference Effects on GNSS Receivers with EMLP Discriminator  [PDF]
Bo Qu, Jiaolong Wei, Shuangna Zhang, Liang Bi
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2016
Abstract: Multipath and continuous wave (CW) interference may cause severe performance degradation of global navigation satellite system (GNSS) receivers. This paper analyzes the code tracking performance of early-minus-late power (EMLP) discriminator of GNSS receivers in the presence of multipath and CW interference. An analytical expression of the code tracking error is suggested for EMLP discriminator, and it can be used to assess the effect of multipath and CW interference. The derived expression shows that the combined effects include three components: multipath component; CW interference component and the combined component of multipath and CW interference. The effect of these components depends on some factors which can be classified into two categories: the receiving environment and the receiver parameters. Numerical results show how these factors affect the tracking performances. It is shown that the proper receiver parameters can suppress the combined effects of multipath and CW interference.
The Effect of Intermittent Signal on the Performance of Code Tracking Loop in GNSS Receivers  [PDF]
Chung-Liang Chang
Journal of Electrical and Computer Engineering , 2011, DOI: 10.1155/2011/418032
Abstract: This paper analyzes the code tracking performance in the presence of signal blanking in Global Navigation Satellite System (GNSS). The blanking effect is usually caused by buildings that obscure the signal in either a periodic or random manner. In some cases, ideal blanking is used to remove random or periodic interference. Nevertheless, the effect of temporary discontinuity of signal often leads to the tracking and position error. To analyze this problem, three types of blanking model are considered: no blanking, periodic blanking, and random blanking of the signals input into the code tracking loop. The mean time to lose lock (MTLL) is to assess the performance of code tracking system under signal blanking. Finally, the effect of steady-state tracking errors on the performance of tracking loop resulting from blanking environment is also discussed.
Designing the unambiguous discriminator from the one -photon interferometer  [PDF]
Xiaohua Wu,Yu Shaolan,Zhou Tao
Physics , 2008, DOI: 10.1103/PhysRevA.79.052302
Abstract: In this paper, we shall show that the question of quanum state unambiguous discrimination can be solved by reducing it to the known problem of quantum states filtering.
Multipath Estimation in Urban Environments from Joint GNSS Receivers and LiDAR Sensors  [PDF]
Khurram Ali,Xin Chen,Fabio Dovis,David De Castro,Antonio J. Fernández
Sensors , 2012, DOI: 10.3390/s121114592
Abstract: In this paper, multipath error on Global Navigation Satellite System (GNSS) signals in urban environments is characterized with the help of Light Detection and Ranging (LiDAR) measurements. For this purpose, LiDAR equipment and Global Positioning System (GPS) receiver implementing a multipath estimating architecture were used to collect data in an urban environment. This paper demonstrates how GPS and LiDAR measurements can be jointly used to model the environment and obtain robust receivers. Multipath amplitude and delay are estimated by means of LiDAR feature extraction and multipath mitigation architecture. The results show the feasibility of integrating the information provided by LiDAR sensors and GNSS receivers for multipath mitigation.
An Adaptive Multipath Mitigation Filter for GNSS Applications  [cached]
Chung-Liang Chang,Jyh-Ching Juang
EURASIP Journal on Advances in Signal Processing , 2008, DOI: 10.1155/2008/214815
Abstract: Global navigation satellite system (GNSS) is designed to serve both civilian and military applications. However, the GNSS performance suffers from several errors, such as ionosphere delay, troposphere delay, ephemeris error, and receiver noise and multipath. Among these errors, the multipath is one of the most unpredictable error sources in high-accuracy navigation. This paper applies a modified adaptive filter to reduce code and carrier multipath errors in GPS. The filter employs a tap-delay line with an Adaline network to estimate the direction and the delayed-signal parameters. Then, the multipath effect is mitigated by subtracting the estimated multipath effects from the processed correlation function. The hardware complexity of the method is also compared with other existing methods. Simulation results show that the proposed method using field data has a significant reduction in multipath error especially in short-delay multipath scenarios.
A New Multipath Mitigation Method for GNSS Receivers Based on an Antenna Array  [PDF]
Sébastien Rougerie,Guillaume Carrié,Fran?ois Vincent,Lionel Ries,Michel Monnerat
International Journal of Navigation and Observation , 2012, DOI: 10.1155/2012/804732
Abstract: 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. 1. Introduction In Global Navigation Satellite System (GNSS) applications, multipath (MP) errors are still one of the major error sources for conventional receivers. The additional signal replicas due to reflections on the local environment introduce a bias in the delay lock loops (DLLs), which finally leads to a positioning error [1, 2]. Several techniques have been developed for multipath mitigation. One of the most popular approaches is the Narrow Correlator Spacing [3], which reduces the chip spacing between the early and late correlators in order to mitigate the impact of multipath. However, this technique suffers from high sensitivity to noise and cannot perform with short delay multipath (<0.1?chip). Based on the Maximum Likelihood (ML) estimation, the Multipath Estimating Delay-Lock-Loop (MEDLL) [4] algorithm has also been proposed to estimate the delay and the power of all the paths by studying the shape of the cross-correlation function. This approach shows better performances than the Narrow Correlator Spacing technique, but short delay multipath mitigation is still an issue [4]. More recently, Bayesian approaches have been proposed [5–7]. Indeed, most of the time, prior information could be used in order to improve the delays estimations. However in practice, it is difficult to get correct prior information. Measurement campaigns can be used to build a first-order Markov process for a sequential estimation, but the performance will consequently be strongly dependent on the measured environment (design of the city…). Last, the use of array antenna algorithms has been proposed for multipath mitigation [8, 9]. Array antennae enable a spatial sampling that makes it possible to distinguish different sources in the spatial domain. Therefore,
A New Conic Fitting Code Discriminator

Xu Ying Wang Ju Wu Si-liang,

电子与信息学报 , 2009,
Abstract: A new conic fitting code discriminator is proposed for the traditional discriminator gain decreasing in bandwidth-limited environment. According to the correlation property, conic fitting code discriminator gets the conic equation with the early and late integration-dumping results. The code phase estimate can be calculated by solving equation. Simulation results show that the conic fitting code discriminator is not influenced by bandwidth and it has better discriminate performance than traditional discriminator when the system bandwidth is limited.
Unambiguous Multipath Mitigation Technique for BOC(n,n) and MBOC-Modulated GNSS Signals
Khaled Rouabah,Mustapha Flissi,Salim Attia,Djamel Chikouche
International Journal of Antennas and Propagation , 2012, DOI: 10.1155/2012/895390
Abstract: We propose an efficient scheme for side peaks cancelation and multipath (MP) mitigation in binary offset carrier (n,n) (BOC(n,n)) and multiplexed BOC (MBOC) modulated signals. The proposed scheme reduces significantly the band of variation of MP errors in global navigation satellite system (GNSS). It consists of two versions. The first one is based on the use of maximum likelihood estimator (MLE) of MP signals and reference correlation functions (CFs) like that of pseudorandom noise (PRN) code without BOC subcarrier. In the second version, the former (MLE) is used with the reference BOC(n,n) or MBOC CFs. Unlike traditional BOC(n,n) and MBOC, that have CFs containing multiple peaks leading to potential tracking ambiguities, our proposed scheme does not contain any side peaks. In addition, all the MP signals with medium and long delays have no effect on the estimation of the pseudorange. On the other hand, all the methods proposed for mitigating MP in no-BOC scheme are practical for our scheme due to its CF which is similar to that of the PRN code. The computer simulation results show that the proposed scheme has superior performances in the reduction of the errors produced in the process of the delay estimation of line of sight (LOS) and caused by MP propagation. In fact, the performances of the proposed scheme are better with regard to that of the traditional BOC(n,n) and MBOC. Moreover, in the presence of noise, our proposed scheme keeps better performances than the common side peaks cancelation methods.
Zhao hongwei,Lian Baowang,Feng Juan
International Journal of Computer Science & Information Technology , 2011,
Abstract: Antenna arrays with space-time adaptive processing (STAP) have been widely used in Global NavigationSatellite System (GNSS) to suppress interference in spatial domain as well as temporal domain, itsperformance depends on digital beamforming algorithms. In this paper, we propose a joint adaptivebeamforming algorithm which produces nullings in the directions of interference while simultaneouslymaximizing carrier-to-noise ratio (C/N0) of post-correlation signal. Firstly, the interferences arecancelled by using subspace orthogonal projection. Then the maximum C/N0 constraint algorithm isemployed to enhance the post-correlation signal. Meanwhile, a simple estimation approach aboutnumbers of interferences is introduced. Finally, simulations demonstrate that using our adaptivealgorithm, STAP can effectively suppress the strong interference and improve the capturing capability ofGNSS.
Optimized Carrier Tracking Loop Design for Real-Time High-Dynamics GNSS Receivers  [PDF]
Pedro A. Roncagliolo,Javier G. García,Carlos H. Muravchik
International Journal of Navigation and Observation , 2012, DOI: 10.1155/2012/651039
Abstract: Carrier phase estimation in real-time Global Navigation Satellite System (GNSS) receivers is usually performed by tracking loops due to their very low computational complexity. We show that a careful design of these loops allows them to operate properly in high-dynamics environments, that is, accelerations up to 40?g or more. Their phase and frequency discriminators and loop filter are derived considering the digital nature of the loop inputs. Based on these ideas, we propose a new loop structure named Unambiguous Frequency-Aided Phase-Locked Loop (UFA-PLL). In terms of tracking capacity and noise resistance UFA-PLL has the same advantages of frequently used coupled-loop schemes, but it is simpler to design and to implement. Moreover, it can keep phase lock in situations where other loops cannot. The loop design is completed selecting the correlation time and loop bandwidth that minimize the pull-out probability, without relying on typical rules of thumb. Optimal and efficient ways to smooth the phase estimates are also presented. Hence, high-quality phase measurements—usually exploited in offline and quasistatic applications—become practical for real-time and high-dynamics receivers. Experiments with fixed-point implementations of the proposed loops and actual radio signals are also shown. 1. Introduction A fundamental task of every Global Navigation Satellite System receiver is to synchronize with the visible satellite signals. Since Direct Sequence Spread Spectrum (DS-SS) signals are utilized, code and carrier synchronization is required, but a correlation stage is necessary to despread the signals before the synchronization algorithms can be applied. In real-time receivers the required economy of operations usually precludes the use of complex estimation schemes and tracking loops are preferred. Due to the correlation process these loops are necessarily discrete. The typical trade-off in tracking loop design is bandwidth versus dynamic performance: output noise increases with a larger loop bandwidth, while dynamic tracking error decreases with it [1]. Thus, the loop design becomes particularly challenging when the receivers are subject to high dynamics. To overcome this limitation other receiver structures have been proposed in [1], claiming tracking capability up to 150?g of acceleration, in contrast with the 5?g regularly assigned to tracking loops. However, the required computational burden is large since several simultaneous correlations and Fast Fourier Transform (FFT) computations are needed. In this paper we show a careful design of the
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