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Papers by Carles Fernández-Prades

Research paper thumbnail of A Receiver-Independent GNSS Smart Antenna for Simultaneous Jamming and Spoofing Protection

Research paper thumbnail of Receiver-independent GNSS Smart Antenna for Interference Mitigation

Research paper thumbnail of Noise Statistics Estimation Techniques for Robust GNSS Carrier Tracking

Zenodo (CERN European Organization for Nuclear Research), Nov 25, 2017

Research paper thumbnail of Multiple sigma-point Kalman smoothers for high-dimensional state-space models

Research paper thumbnail of Implementation of a GNSS Rebroadcaster in an All-Programmable System-On-Chip Platform

Research paper thumbnail of Direct Position Estimation Approach: How Good Can it Get?

Research paper thumbnail of Particle Filtering Strategies for Efficient Multipath Mitigation

Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Sep 19, 2008

This paper deals with the problem of multipath mitigation using a Particle Filtering (PF) approac... more This paper deals with the problem of multipath mitigation using a Particle Filtering (PF) approach. We describe two PF algorithms already proposed by the authors in [1] and [2]. The aim of the present paper is to compare both alternatives in terms of particle efficiency, that is, to study the required number of particles to achieve a certain tracking precision. The efficiency issue is of high importance when a PF implementation is envisaged since reducing the number of samples has a direct impact in the required computational resources.

Research paper thumbnail of GNSS Software Defined Radio: History, Current Developments, and Standardization Efforts

ION GNSS+, The International Technical Meeting of the Satellite Division of The Institute of Navigation

Research paper thumbnail of A Technology-agnostic GNSS/INS Real-time Sensor Fusion Platform with Ultra Wide Band Cooperative Distance Measurements for Terrestrial Vehicle Navigation

Proceedings of the 31st International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2018)

Research paper thumbnail of Implementation of GNSS Receiver Hardware Accelerators in All-programmable System-On-Chip Platforms

Proceedings of the 31st International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2018)

Research paper thumbnail of Implementation of a GNSS Rebroadcaster in an All-Programmable System-On-Chip Platform

2022 10th Workshop on Satellite Navigation Technology (NAVITEC)

Research paper thumbnail of Gestalt: A Testbed For Experimentation And Validation Of Gnss Software Receivers

This paper presents a new platform for the experimentation with GNSS signals. It includes a set o... more This paper presents a new platform for the experimentation with GNSS signals. It includes a set of commercial of-the-shelf hardware and an open source software, constituting a state-of-the-art platform for research and development of next-generation GNSS receivers. The core of the platform is the GNSS-SDR receiver which has been extended to support multi-band and multi-system operations. As a relevant case of use to validate the research facility, we presented a triple band GNSS-SDR customization capable of receiving four GNSS signals in real-time: GPS L1 C/A, GPS L2CM, Galileo E1b, and Galileo E5a. In addition, we provided detailed descriptions of the receiver architecture, identifying the synchronization challenges of the multi-system satellite channels and providing practical and reproducible solutions. The source code developed to produce this paper has been released under the General Public License, and it is freely available on the Internet.

Research paper thumbnail of Fastening Gps And Galileo Tight With A Software Reciever

This paper presents the design, implementation and performance analysis of a hybrid GPS/Galileo s... more This paper presents the design, implementation and performance analysis of a hybrid GPS/Galileo software receiver. The proposed approach exploits the dissemination of Galileo-to-GPS time conversion parameters through Galileo's navigation message to mix pseudoranges of both constellations seamlessly, obtaining position fixes even with four satellites belonging to different systems. The approach is tested both with synthetically generated signals and with real-life signals using the four In-Orbit Validation Galileo satellites. The source code developed to produce this paper has been released under the General Public License, and it is freely available on the Internet.

Research paper thumbnail of On-line model learning for adaptive GNSS ionospheric scintillation estimation and mitigation

2018 IEEE/ION Position, Location and Navigation Symposium (PLANS), 2018

One of the more challenging propagation conditions in Global Navigation Satellite Systems (GNSS),... more One of the more challenging propagation conditions in Global Navigation Satellite Systems (GNSS), clearly affecting high-precision receivers and safety critical applications, is ionospheric scintillation. One of the main disadvantages of standard phase tracking architectures is the estimation vs mitigation tradeoff, that is, it is impossible to distinguish between the line-of-sight (LOS) phase contribution of interest and phase variations induced by the ionosphere. A possible solution is to consider a state-space formulation of the problem, where the scintillation amplitude and phase are estimated together with the LOS phase variations. The current Kalman filter-based techniques exploiting this idea consider an off-line scintillation model fitting, thus not suitable for real-life applications. In this contribution we propose an adaptive model learning strategy to be able to cope with time-varying unknown scintillation conditions. The performance of the new approach is shown using real ionospheric scintillation data recorded over Hanoi in 2015.

Research paper thumbnail of A Cloud Optical Access Network for Virtualized GNSS Receivers

Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017), 2017

Research paper thumbnail of Spoofing Detection by a Reduced Acquisition Process

Research paper thumbnail of Evaluation of GNSS Direct Position Estimation in Realistic Multipath Channels

Research paper thumbnail of A Software-Defined Spaceborne GNSS Receiver

2018 9th ESA Workshop on Satellite NavigationTechnologies and European Workshop on GNSS Signals and Signal Processing (NAVITEC), 2018

Research paper thumbnail of Low-cost GNSS/INS/Odometric Sensor Fusion Platform for Ground Intelligent Transportation Systems

Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017), 2017

For many applications in Intelligent Transport Systems (ITS), the position and heading informatio... more For many applications in Intelligent Transport Systems (ITS), the position and heading information of vehicles and Vulnerable Road Users (VRU) cannot generally rely on the performance of the Global Navigation Satellite System (GNSS) as a standalone technology. Even with the use of precise positioning techniques and augmentation systems for GNSS, such as Space-based<br> Augmentation System (SBAS) or Differential-GNSS, its performance and its availability still depends on the signal propagation¡ conditions (e.g. multipath, unintentional or intentional (jamming) interferences, or visibility of satellites). The urban canyon represents one of the most challenging scenarios for GNSS standalone positioning, being an scenario where ITS users usually<br> require the highest performance.<br> This paper discusses the design, implementation and performance validation of multisensor positioning based on GNSS, Inertial Measurement Units (IMU), and Odometric information for ground ITS applications. Bayesian sensor fusion algorithms are discussed and loose and tight GNSS/INS coupling compared. Additionally, these algorithms are enhanced by exploring the application of dynamic noise covariance matrices, including non-holonomic constraints to the vehicle's movement, and by adding a zero velocity update IMU calibration algorithm using the vehicle's speedometer measurements. The algorithms performance was extensively evaluated in both simulation and in real-life experiments.<br> The algorithms are validated in a low-cost prototype implementation. The prototype receiver, operating in real-time, is based on the popular Raspberry PI3 platform, a dual-IMU MEMS peripheral and a consumer-grade GNSS receiver. The paper includes a discussion of the implementation trade-offs, challenges, and adopted solutions. A measurement campaign where the<br> developed prototype was mounted on a vehicle is discussed, showing the potential of this approach.

Research paper thumbnail of Joint maximum likelihood estimation of time delays and Doppler shifts

Seventh International Symposium on Signal Processing and Its Applications, 2003. Proceedings., 2003

This paper deals with the problem of estimating the am-plitudes, time delays and Doppler shifts o... more This paper deals with the problem of estimating the am-plitudes, time delays and Doppler shifts of a set of known signals received by an array of antennas in temporally white but spatially colored noise. Applying the Maximum Likeli-hood approach, the estimation reduces to an ...

Research paper thumbnail of A Receiver-Independent GNSS Smart Antenna for Simultaneous Jamming and Spoofing Protection

Research paper thumbnail of Receiver-independent GNSS Smart Antenna for Interference Mitigation

Research paper thumbnail of Noise Statistics Estimation Techniques for Robust GNSS Carrier Tracking

Zenodo (CERN European Organization for Nuclear Research), Nov 25, 2017

Research paper thumbnail of Multiple sigma-point Kalman smoothers for high-dimensional state-space models

Research paper thumbnail of Implementation of a GNSS Rebroadcaster in an All-Programmable System-On-Chip Platform

Research paper thumbnail of Direct Position Estimation Approach: How Good Can it Get?

Research paper thumbnail of Particle Filtering Strategies for Efficient Multipath Mitigation

Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Sep 19, 2008

This paper deals with the problem of multipath mitigation using a Particle Filtering (PF) approac... more This paper deals with the problem of multipath mitigation using a Particle Filtering (PF) approach. We describe two PF algorithms already proposed by the authors in [1] and [2]. The aim of the present paper is to compare both alternatives in terms of particle efficiency, that is, to study the required number of particles to achieve a certain tracking precision. The efficiency issue is of high importance when a PF implementation is envisaged since reducing the number of samples has a direct impact in the required computational resources.

Research paper thumbnail of GNSS Software Defined Radio: History, Current Developments, and Standardization Efforts

ION GNSS+, The International Technical Meeting of the Satellite Division of The Institute of Navigation

Research paper thumbnail of A Technology-agnostic GNSS/INS Real-time Sensor Fusion Platform with Ultra Wide Band Cooperative Distance Measurements for Terrestrial Vehicle Navigation

Proceedings of the 31st International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2018)

Research paper thumbnail of Implementation of GNSS Receiver Hardware Accelerators in All-programmable System-On-Chip Platforms

Proceedings of the 31st International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2018)

Research paper thumbnail of Implementation of a GNSS Rebroadcaster in an All-Programmable System-On-Chip Platform

2022 10th Workshop on Satellite Navigation Technology (NAVITEC)

Research paper thumbnail of Gestalt: A Testbed For Experimentation And Validation Of Gnss Software Receivers

This paper presents a new platform for the experimentation with GNSS signals. It includes a set o... more This paper presents a new platform for the experimentation with GNSS signals. It includes a set of commercial of-the-shelf hardware and an open source software, constituting a state-of-the-art platform for research and development of next-generation GNSS receivers. The core of the platform is the GNSS-SDR receiver which has been extended to support multi-band and multi-system operations. As a relevant case of use to validate the research facility, we presented a triple band GNSS-SDR customization capable of receiving four GNSS signals in real-time: GPS L1 C/A, GPS L2CM, Galileo E1b, and Galileo E5a. In addition, we provided detailed descriptions of the receiver architecture, identifying the synchronization challenges of the multi-system satellite channels and providing practical and reproducible solutions. The source code developed to produce this paper has been released under the General Public License, and it is freely available on the Internet.

Research paper thumbnail of Fastening Gps And Galileo Tight With A Software Reciever

This paper presents the design, implementation and performance analysis of a hybrid GPS/Galileo s... more This paper presents the design, implementation and performance analysis of a hybrid GPS/Galileo software receiver. The proposed approach exploits the dissemination of Galileo-to-GPS time conversion parameters through Galileo's navigation message to mix pseudoranges of both constellations seamlessly, obtaining position fixes even with four satellites belonging to different systems. The approach is tested both with synthetically generated signals and with real-life signals using the four In-Orbit Validation Galileo satellites. The source code developed to produce this paper has been released under the General Public License, and it is freely available on the Internet.

Research paper thumbnail of On-line model learning for adaptive GNSS ionospheric scintillation estimation and mitigation

2018 IEEE/ION Position, Location and Navigation Symposium (PLANS), 2018

One of the more challenging propagation conditions in Global Navigation Satellite Systems (GNSS),... more One of the more challenging propagation conditions in Global Navigation Satellite Systems (GNSS), clearly affecting high-precision receivers and safety critical applications, is ionospheric scintillation. One of the main disadvantages of standard phase tracking architectures is the estimation vs mitigation tradeoff, that is, it is impossible to distinguish between the line-of-sight (LOS) phase contribution of interest and phase variations induced by the ionosphere. A possible solution is to consider a state-space formulation of the problem, where the scintillation amplitude and phase are estimated together with the LOS phase variations. The current Kalman filter-based techniques exploiting this idea consider an off-line scintillation model fitting, thus not suitable for real-life applications. In this contribution we propose an adaptive model learning strategy to be able to cope with time-varying unknown scintillation conditions. The performance of the new approach is shown using real ionospheric scintillation data recorded over Hanoi in 2015.

Research paper thumbnail of A Cloud Optical Access Network for Virtualized GNSS Receivers

Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017), 2017

Research paper thumbnail of Spoofing Detection by a Reduced Acquisition Process

Research paper thumbnail of Evaluation of GNSS Direct Position Estimation in Realistic Multipath Channels

Research paper thumbnail of A Software-Defined Spaceborne GNSS Receiver

2018 9th ESA Workshop on Satellite NavigationTechnologies and European Workshop on GNSS Signals and Signal Processing (NAVITEC), 2018

Research paper thumbnail of Low-cost GNSS/INS/Odometric Sensor Fusion Platform for Ground Intelligent Transportation Systems

Proceedings of the 30th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2017), 2017

For many applications in Intelligent Transport Systems (ITS), the position and heading informatio... more For many applications in Intelligent Transport Systems (ITS), the position and heading information of vehicles and Vulnerable Road Users (VRU) cannot generally rely on the performance of the Global Navigation Satellite System (GNSS) as a standalone technology. Even with the use of precise positioning techniques and augmentation systems for GNSS, such as Space-based<br> Augmentation System (SBAS) or Differential-GNSS, its performance and its availability still depends on the signal propagation¡ conditions (e.g. multipath, unintentional or intentional (jamming) interferences, or visibility of satellites). The urban canyon represents one of the most challenging scenarios for GNSS standalone positioning, being an scenario where ITS users usually<br> require the highest performance.<br> This paper discusses the design, implementation and performance validation of multisensor positioning based on GNSS, Inertial Measurement Units (IMU), and Odometric information for ground ITS applications. Bayesian sensor fusion algorithms are discussed and loose and tight GNSS/INS coupling compared. Additionally, these algorithms are enhanced by exploring the application of dynamic noise covariance matrices, including non-holonomic constraints to the vehicle's movement, and by adding a zero velocity update IMU calibration algorithm using the vehicle's speedometer measurements. The algorithms performance was extensively evaluated in both simulation and in real-life experiments.<br> The algorithms are validated in a low-cost prototype implementation. The prototype receiver, operating in real-time, is based on the popular Raspberry PI3 platform, a dual-IMU MEMS peripheral and a consumer-grade GNSS receiver. The paper includes a discussion of the implementation trade-offs, challenges, and adopted solutions. A measurement campaign where the<br> developed prototype was mounted on a vehicle is discussed, showing the potential of this approach.

Research paper thumbnail of Joint maximum likelihood estimation of time delays and Doppler shifts

Seventh International Symposium on Signal Processing and Its Applications, 2003. Proceedings., 2003

This paper deals with the problem of estimating the am-plitudes, time delays and Doppler shifts o... more This paper deals with the problem of estimating the am-plitudes, time delays and Doppler shifts of a set of known signals received by an array of antennas in temporally white but spatially colored noise. Applying the Maximum Likeli-hood approach, the estimation reduces to an ...