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Seokho Yoon - One of the best experts on this subject based on the ideXlab platform.

Bernd Eissfeller - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of Kalman Filters for GNSS Signal Tracking Loop
    IEEE Transactions on Aerospace and Electronic Systems, 2012
    Co-Authors: Thomas Pany, Bernd Eissfeller
    Abstract:

    Characteristics of Signal Tracking Kalman filter (KF) approaches for a Global Navigation Satellite System (GNSS) receiver are presented. In particular the direct-state KF is designed by using a state vector for Signal parameters not for Signal parameter errors, so as to directly utilize the discriminator output as a measurement residual. This enables the reuse of the existing Signal Tracking loop structure by simply adjusting the filter coefficients based on a time-varying optimal Kalman gain. The characteristics of the direct-state KF together with the error-state KF are analyzed by comparing their noise bandwidth and open- and closed-loop transfer functions with those of a traditional method. These KF approaches are mathematically equivalent to the traditional method except for the use of time-varying gains. This fact provides an insight how to tune the designed KFs based on their expected performances.

  • Iterative Maximum Likelihood Estimators for High-Dynamic GNSS Signal Tracking
    IEEE Transactions on Aerospace and Electronic Systems, 2012
    Co-Authors: Thomas Pany, Bernd Eissfeller
    Abstract:

    This paper presents novel Signal-Tracking algorithms for global navigation satellite system (GNSS) receivers using a maximum likelihood estimation (MLE) technique to carry out robust Signal Tracking under severe Signal environments, such as high dynamics for maneuvering users. The cost function of the MLE of Signal parameters such as code delay, carrier phase, and Doppler frequency is used to derive a discriminator function and thus generate error Signals based on incoming and reference Signals. Two distinct forms of algorithms are derived by means of mathematical programming using an iterative approach, which is based on the log-likelihood MLE cost function that assumes various Signal parameters as unknown constants over an observation interval. First, the Levenberg-Marquardt method is employed using gradient and Hessian matrices. Second, a conventional nonlinear least-square estimation method is applied to determine the MLE cost function, assuming additive white Gaussian noise. An efficient and practical approach to Doppler frequency Tracking is also derived based on the assumption of a code-free Signal (i.e., a Signal from which the code has been wipe off). The use of MLE for carrier Tracking makes it possible to generalize the MLE equation for arbitrary codes and modulation schemes. This is ideally suited to various GNSS Signals that have the same Tracking module structure. Finally, performance of the receivers, in terms of robustness under dynamic stress, computational efficiency, accuracy, computational burden, and response speed, is assessed using analytical and/or numerical techniques.

  • Noniterative Filter-Based Maximum Likelihood Estimators for GNSS Signal Tracking
    IEEE Transactions on Aerospace and Electronic Systems, 2012
    Co-Authors: Thomas Pany, Bernd Eissfeller
    Abstract:

    This paper presents alternate forms of a Signal Tracking algorithm for Global Navigation Satellite System (GNSS) receivers that use a maximum likelihood estimation (MLE) technique. The cost function of the MLE for estimating Signal parameters such as code delay, carrier phase, and Doppler frequency is used to derive discriminator functions to create error Signals from incoming and reference Signals. Assuming a code-free Signal and an additive white Gaussian noise, we derive an efficient, practical form of general purpose Signal Tracking algorithms by using a noniterative MLE approach for arbitrary spreading codes and modulation schemes in accordance with computational efficiency. Two versions of an MLE algorithm are derived. The first is a coherent MLE algorithm derived from the gradient of the log-likelihood cost function for Signal parameters. The second is a noncoherent MLE algorithm derived on the basis of complex domain Signal that is insensitive to carrier phase error and data bits, thereby eliminating the coupling effect between the carrier phase and Doppler frequency. Analytical test results demonstrate the performance of the proposed algorithms in comparison with those from conventional approaches in terms of pull-in-range, coupling effect, and computational efficiency.

  • performance comparison of different forms of kalman filter approaches for a vector based gnss Signal Tracking loop
    Annual of Navigation, 2010
    Co-Authors: Jong-hoon Won, Dominik Dötterböck, Bernd Eissfeller
    Abstract:

    In this paper we discuss several different Kalman filter methods to estimate Signal parameters in a GNSS receiver's Signal Tracking loop with a special emphasis given on how to construct the measurement residuals and the relevant design matrix. There are three variations of error state Kalman filters for a loop filter, and a direct state Kalman filter for the entire Signal Tracking loop. Based on detailed Signal models for a Signal Tracking loop, four different Kalman filters for Signal Tracking are compared with the traditional one. Block diagram implementation of the direct state Kalman filter for the entire Signal Tracking loop is proposed by using the analogy relationship with the traditional method in a scalar Tracking mode and a vector Tracking mode. Numerical simulation results show that the Kalman filter methods provide 2 to 3 dB carrier-to-noise ratio gain in carrier phase and Doppler Tracking compared to the traditional method.

  • Performance Comparison of Different Forms of Kalman Filter Approaches for a Vector‐Based GNSS Signal Tracking Loop
    Navigation, 2010
    Co-Authors: Jong-hoon Won, Dominik Dötterböck, Bernd Eissfeller
    Abstract:

    In this paper we discuss several different Kalman filter methods to estimate Signal parameters in a GNSS receiver's Signal Tracking loop with a special emphasis given on how to construct the measurement residuals and the relevant design matrix. There are three variations of error state Kalman filters for a loop filter, and a direct state Kalman filter for the entire Signal Tracking loop. Based on detailed Signal models for a Signal Tracking loop, four different Kalman filters for Signal Tracking are compared with the traditional one. Block diagram implementation of the direct state Kalman filter for the entire Signal Tracking loop is proposed by using the analogy relationship with the traditional method in a scalar Tracking mode and a vector Tracking mode. Numerical simulation results show that the Kalman filter methods provide 2 to 3 dB carrier-to-noise ratio gain in carrier phase and Doppler Tracking compared to the traditional method.

Eduard Alarcon - One of the best experts on this subject based on the ideXlab platform.

  • A Study on Multi-Level PWM and Asynchronous /spl Sigma/ /spl Delta/ Modulations for Enhanced Bandlimited Signal Tracking in Switching Power Amplifiers
    IEEE Transactions on Circuits and Systems I-regular Papers, 2013
    Co-Authors: Albert Garcia I Tormo, Alberto Poveda, Eduard Alarcon, Francesc Guinjoan
    Abstract:

    This work deals with multi-level switching amplifiers, in the context of high-efficiency power amplification for Signal Tracking applications. In particular, this paper evaluates the reduction in the error Signal's power due to multi-level power amplification (compared to conventional two-level amplifiers) and compares the performance of two multi-level pulse modulations: PWM and Asynchronous ΣΔ Modulation. First the intrinsic bandwidth limits of multi-level switching amplifiers are inferred, to clearly state the advantages and limitations of multi-level power amplification. From the existing analyses of Pulse Width Modulation already reported in the literature, PWM is herein extended to multiple levels based on an equivalent representation, which allows to derive a closed expression for the power spectrum of multi-level PWM in bandlimited Signal Tracking. The Asynchronous ΣΔ Modulation is extended to multiple levels and the resulting multi-level encoding algorithm is analyzed in both time and frequency domains. The performance of both modulations is characterized and compared at different operating frequencies and using different number of levels. The main outcomes of this in-depth characterization show that, if the switching frequency is high enough, the Tracking error is independent of the modulation and the switching frequency, i.e., it only depends upon the number of levels, which points out the suitability of asynchronous modulations for relatively low switching frequencies (compared to the number of levels).

  • Derivation of the sliding domain for a buck-based switching amplifier in wideband Signal Tracking applications
    2007 18th European Conference on Circuit Theory and Design, 2007
    Co-Authors: L. Marco, Eduard Alarcon
    Abstract:

    One of the major drawbacks that precludes the use of sliding-mode control wideband Signal Tracking in buck-based switching power amplifiers is the lack of a design-oriented analysis of Tracking bandwidth limits. In this paper the Tracking limits for a linear-surface sliding-mode controlled ideal buck converter are addressed for different representative cases, namely, for a single tone, two tones, multiple tone, and a generalization to an arbitrary wideband Signal. Analytical design-oriented equations are matched with simulations both for synthetic single-tone and arbitrary wideband noise Signal as well as for the envelope Signal corresponding to the EDGE standard in an envelope elimination and restoration technique polar RF transmitter architecture.

  • ECCTD - Derivation of the sliding domain for a buck-based switching amplifier in wideband Signal Tracking applications
    2007 18th European Conference on Circuit Theory and Design, 2007
    Co-Authors: L. Marco, Eduard Alarcon
    Abstract:

    One of the major drawbacks that precludes the use of sliding-mode control wideband Signal Tracking in buck-based switching power amplifiers is the lack of a design-oriented analysis of Tracking bandwidth limits. In this paper the Tracking limits for a linear-surface sliding-mode controlled ideal buck converter are addressed for different representative cases, namely, for a single tone, two tones, multiple tone, and a generalization to an arbitrary wideband Signal. Analytical design-oriented equations are matched with simulations both for synthetic single-tone and arbitrary wideband noise Signal as well as for the envelope Signal corresponding to the EDGE standard in an envelope elimination and restoration technique polar RF transmitter architecture.

Christophe Macabiau - One of the best experts on this subject based on the ideXlab platform.

  • Pseudorange Measurements with LTE Physical Channels
    2020
    Co-Authors: Auryn Soderini, Christophe Macabiau, Paul Thevenon, Laurent Borgagni, John Fischer
    Abstract:

    The long-term evolution (LTE) reference Signals, such as the primary synchronization Signal (PSS), secondary synchronization Signal (SSS) and cell-specific reference Signal (CRS), have been studied for navigation.The Signal structure including its influence on Signal Tracking has been previously discussed. However, there are non-reference Signals such as the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid automatic repeat request (HARQ) indicator channel (PHICH) and physical downlink control channel (PDCCH) that can also be used for navigation. To the authors’ knowledge, pseudorange estimates with LTE physical channels have been almost not considered in the literature. This paper makes two contributions. First, the LTE physical channels properties which are relevant for Signal Tracking are discussed. Second, the expected Tracking performance with LTE physical channels used in a standalone fashion are evaluated.

  • 5G-microwave Tracking Performance Characterization
    2019
    Co-Authors: Auryn Soderini, Christophe Macabiau, Paul Thevenon, Laurent Borgagni, John Fischer
    Abstract:

    This paper evaluates the theoretical performance of Signal Tracking in a noisy single-path environment using 5G-microwave and LTE Signals. Such OFDM Signals suit navigation applications thanks to build-in symbol sequences which despite being designed for communication services since are known at the receiver can be exploited for pseudorange computation. By using multiple numerologies, 5G is putting into place an important degree of flexibility which was not explored before. It turns out, the numerology counts towards the Signal Tracking performance. However, the nominal Tracking capacity expressed by 5G-microwave Signals at the highest sampling frequency is reduced due to the lack of full bandwidth useful Signals. Top-ranked LTE-CRS performance can hypothetically improve by aggregating multiple carrier components.

  • Kalman filter based robust GNSS Signal Tracking algorithm in presence of ionospheric scintillations
    2012
    Co-Authors: Christophe Macabiau, Lina Deambrogio, Valentin Barreau, Willy Vigneau, Jean-jacques Valette, Géraldine Artaud, Paul Thevenon, Lionel Ries
    Abstract:

    Ionospheric scintillations are created by diffraction when the transmitted propagating waves encounter a medium made of irregular structures with variable refraction indexes. The recombination of the waves after propagation can be constructive or destructive and the resulting Signal at output of the receiver antenna may present rapid variations of phase and amplitude. Scintillations are essentially observed in the regions located under the geomagnetic equator, where irregularities in the ionosphere like plasma bubbles occur more frequently. They also happen over Polar Regions and are associated with the penetration of charged particles along the magnetic field lines. Under the auroral oval region, scintillations can be local or spread over a great part of the oval. According to past observations scintillations occur mainly at the period of the equinox and the solstice. During the rest of the time there are almost no observations. After sunset, the modification in the ionosphere layers generates such variations. Scintillations cause very brutal and fast fades of the received Signal, and once these phenomena occur they can last from 30 minutes up to several hours. However, continuous GNSS Carrier Phase Measurements are important observations needed for data demodulation and are increasingly used in GNSS receivers, both at user side (e.g. for precise positioning), and for ground segments to compute the navigation and integrity data. The carrier phase is traditionally tracked in the GNSS receivers using PLL, potentially aided by FLL. Carrier Tracking loops may be optimized, depending on the application and environment, by selecting the appropriated loop order, integration time, and bandwidth (trade-off between accuracy and robustness). Phase Loops are however known to be less robust than code Tracking loops, and the GNSS receivers may thus suffer from phase Tracking loss, for example when Tracking low C/N0 Signals (attenuations), or fast varying Signals such as Signals affected by scintillations. This strongly impacts the positioning service availability, as well as the capability to demodulate the navigation message data, in situations where ionospheric scintillations affect the received Signal. One thus has to implement innovative techniques and receiver architectures to provide robust carrier phase Tracking, either by improving or optimizing the classical Tracking loops (optimized parameters of the PLL, potentially dynamically) or by defining different architectures such as Kalman filter-based Tracking loops (either scalar or vector architectures, taking benefits of the different Tracking channels, constellations and frequencies which may be differently affected by the disturbance). Other techniques coming, for example, from the telecommunication domain can also be interesting to estimate the propagation channel parameters. It can also be taken advantage of the improved structure of the modern GNSS Signals, providing in particular a pilot Signal component. The improvement technique investigated in this paper consists in replacing the conventional phase lock loop filter by a Kalman Filter PLL (KFP), as inspired by the technique proposed by Psiaki et al.. Kalman loop filters provide the optimal filter gain when the statistical levels of uncertainty of the state and observation vectors are well known. So the Kalman filter is continuously adapting the filter bandwidth to the noise level. KFP Tracking loop indeed show a better resistance to weak GNSS Signal Tracking compared to classical loop filters. We were therefore interested in analyzing the potential of such KFP variants for Tracking the GPS L1 carrier phase in presence of scintillations, adapting in particular the feedback control Signal. This was conducted during a project financed by CNES. The aim of this paper is therefore to present the development of a GPS L1 phase Tracking technique based on a Kalman Filter improving the Tracking robustness in presence of ionospheric scintillations, and to present results of its performance using simulations. The paper starts with a description of the phenomenon of ionospheric scintillation, including the possible models for Signals affected by ionospheric scintillations, focusing on the model selected for this study which is GISM (Global Ionospheric Scintillation Model) developed by IEEA. The second section presents a review of the state of the art of ionospheric mitigation Tracking techniques. In a third part, the proposed robust GPS L1 Tracking technique proposed is described. Then the simulation environment is described, and simulations results are presented, showing improved performance of the proposed Tracking technique.

  • EFFECT OF SAMPLING JITTER ON Signal Tracking IN A DIRECT SAMPLING DUAL BAND GNSS RECEIVER FOR CIVIL AVIATION
    2012
    Co-Authors: Antoine Blais, Christophe Macabiau, Olivier Julien
    Abstract:

    This paper studies the impact of clock sampling jitter on Signal Tracking in a dual band L5/E5 and L1/E1 Direct Sampling GNSS receiver designed for Civil Aviation. A model of the sampling clock jitter due to thermal noise is established and related simulation results about the phase Tracking error standard deviation at the output of the PLL are presented.

  • a new unambiguous boc n n Signal Tracking technique
    2004
    Co-Authors: Olivier Julien, Gérard Lachapelle, Elizabeth M Cannon, C Mongredien, Christophe Macabiau
    Abstract:

    GALILEO, the major contribution of the European Union to the Global Navigation Satellite System (GNSS), will be both independent and complementary to the current GPS. It is still in its design phase, and while the Signals have to be finalized, the main specifications have already been confirmed. The Binary Offset Carrier (BOC) modulation is part of the current GALILEO Signal plan. A BOC modulation multiplies a spreading code with a square wave sub-carrier that has a frequency multiple of the code rate. It creates a split spectrum with two main lobes shifted from the center frequency by the frequency of the sub-carrier. This modulated Signal induces better Tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and Tracking potentially ambiguous due to its multiple peak autocorrelation function. As a result, an evaluation of its performance under different conditions and research on advanced Tracking techniques are necessary to assess its robustness and advantages before final selection. This paper focuses on a specific BOC Signal: the BOC(1,1). Working on a given Signal, instead of trying to find a generic solution, offers the possibility to fully exploit this Signal's characteristics to find a more relevant way to improve its performance and cancel its bias threat. A new innovative Tracking technique dedicated to BOC(n,n) Signals has therefore been developed using a synthesized local correlation function. It completely removes the sidepeak threat and allows clean acquisition and Tracking of any BOC(n,n) Signal while keeping the same sharp correlation main peak. Consequently, it does not need to check if Tracking is done on the main peak. It also offers a good resistance to long-delay multipath. The particular case of BOC(1,1) is taken as an example throughout the paper due to the strong probability that it will be used by the L1 GALILEO civil Signal. Both acquisition and Tracking are studied and compared with the standard Tracking algorithm, first theoretically and then using simulations.

Keunhong Chae - One of the best experts on this subject based on the ideXlab platform.