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  • Frequency-domain GLR detection of a second-order cyclostationary signal over fading channels

     Riba Sagarra, Jaume; Font Segura, Josep; Villares Piera, N. Javier; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2014-04-01
    Journal article

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    Cyclostationary processes exhibit a form of frequency diversity. Based on that, we show that a digital waveform with symbol period T can be asymptotically represented as a rank-1 frequency-domain vector process which exhibits uncorrelation at different frequencies inside the Nyquist spectral support of 1/T. By resorting to the fast Fourier transform (FFT), this formulation obviates the need of estimating a cumbersome covariance matrix to characterize the likelihood function. We then derive the generalized likelihood ratio test (GLRT) for the detection of a cyclostationary signal in unknown white noise without the need of a assuming a synchronized receiver. This provides a sound theoretical basis for the exploitation of the cyclostationary feature and highlights an explicit link with classical square timing recovery schemes, which appear implicitly in the core of the GLRT. Moreover, to avoid the well-known sensitivity of cyclostationary-based detection schemes to frequency-selective fading channels, a parametric channel model based on a lower bound on the coherence bandwidth is adopted and incorporated into the GLRT. By exploiting the rank-1 structure of small spectral covariance matrices, the obtained detector outperforms the classical spectral correlation magnitude detector.

    Cyclostationary processes exhibit a form of frequency diversity. Based on that, we show that a digital waveform with symbol period T can be asymptotically represented as a rank-1 frequency-domain vector process which exhibits uncorrelation at different frequencies inside the Nyquist spectral support of 1/T. By resorting to the fast Fourier transform (FFT), this formulation obviates the need of estimating a cumbersome covariance matrix to characterize the likelihood function. We then derive the generalized likelihood ratio test (GLRT) for the detection of a cyclostationary signal in unknown white noise without the need of a assuming a synchronized receiver. This provides a sound theoretical basis for the exploitation of the cyclostationary feature and highlights an explicit link with classical square timing recovery schemes, which appear implicitly in the core of the GLRT. Moreover, to avoid the well-known sensitivity of cyclostationary-based detection schemes to frequency-selective fading channels, a parametric channel model based on a lower bound on the coherence bandwidth is adopted and incorporated into the GLRT. By exploiting the rank-1 structure of small spectral covariance matrices, the obtained detector outperforms the classical spectral correlation magnitude detector.

  • ANTARES Project (Phase B2). Global beam payload synchronization: algorithms and simulations

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2013-01-15
    Report

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  • Quadratic sphericity test for blind detection over time-varying frequency-selective fading channels

     Font Segura, Josep; Riba Sagarra, Jaume; Villares Piera, N. Javier; Vazquez Grau, Gregorio
    IEEE International Conference on Acoustics, Speech, and Signal Processing
    Presentation's date: 2013-05-26
    Presentation of work at congresses

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    This paper addresses the problem of blind detection of a wide-sense stationary (WSS) signal over fading channels. We propose a test statistic which is optimal from a correlation- matching perspective that shows invariance with respect to the noise power and the channel gain. In the blind scenario, we derive the quadratic sphericity test (QST) which exploits the structure of the fading channel as a squared mean to arith- metic mean ratio of the eigenvalues of the autocorrelation matrix of the observations. We provide numerical results to assess the performance of the QST in several fading scenar- ios, as well as the benchmarking to other blind and non-blind detectors.

    This paper addresses the problem of blind detection of a wide-sense stationary (WSS) signal over fading channels. We propose a test statistic which is optimal from a correlation-matching perspective that shows invariance with respect to the noise power and the channel gain. In the blind scenario, we derive the quadratic sphericity test (QST) which exploits the structure of the fading channel as a squared mean to arithmetic mean ratio of the eigenvalues of the autocorrelation matrix of the observations. We provide numerical results to assess the performance of the QST in several fading scenarios, as well as the benchmarking to other blind and non-blind detectors.

  • Asymptotically optimum energy profile for successive interference cancellation in DS-CDMA under a power unbalance constraint

     Sala Alvarez, Jose; Rey Micolau, Francesc; Villares Piera, N. Javier
    IEEE communications letters
    Date of publication: 2012-02
    Journal article

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  • ANTARES Project (Phase B2). Forward Link Payload Synchronization and Equalization: Algorithms and Simulations

     Villares Piera, N. Javier; Rey Micolau, Francesc; Sala Alvarez, Jose; Lamarca Orozco, M. Meritxell; Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Ramirez Javega, Francisco; Font Segura, Josep; Matas Navarro, David
    Date: 2012-10-05
    Report

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  • Binary graphs and message passing strategies for compressed sensing in the noiseless setting

     Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Villares Piera, N. Javier
    IEEE International Symposium on Information Theory
    Presentation's date: 2012-07-04
    Presentation of work at congresses

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    We propose a scheme for Compressed Sensing in the noiseless setting that reconstructs the original signal operating on a binary graph where the samples are obtained sequentially. The proposed scheme has an affordable computational complexity and a large performance enhancement with respect to similar schemes in the literature, thanks to the proposed measurement matrix structure and enhanced decoding based on a message passing algorithm.

  • Asymptotic and finite user PER analysis of successive interference cancellation in DS-CDMA

     Sala Alvarez, Jose; Villares Piera, N. Javier; Rey Micolau, Francesc
    IEEE communications letters
    Date of publication: 2011-11
    Journal article

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    An expression is derived for the average Packet Error Rate (PER) of a Successive Interference Canceller (SIC) for DS-CDMA when the number of users asymptotically tends to infinity. The asymptotic probability density function of the interference power is governed by a Fokker-Planck differential equation with drift and (asymptotically vanishing) diffusion depending on the PER function of the adopted forward error-correcting code (FEC). In addition to the asymptotic solution for the PER, a particle-based algorithm is also developed for computing efficiently the PER in the finite user case.

  • ANTARES Project (Bridging Phase). Payload carrier synchronization : algorithms and simulations

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2011-11-23
    Report

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    Informe final Bridging Phase. Versió 3.2

  • A Nondata-Aided SNR Estimation Technique for Multilevel Modulations Exploiting Signal Cyclostationarity

     Riba Sagarra, Jaume; Villares Piera, N. Javier; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2010-11-01
    Journal article

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    Signal-to-noise ratio (SNR) estimators of linear modulation schemes usually operate at one sample per symbol at the matched filter output. In this paper we propose a new method for estimating the SNR in the complex additive white Gaussian noise (AWGN) channel that operates directly on the oversampled cyclostationary signal at the matched filter input. Exploiting cyclostationarity proves to be advantageous due to the fact that a signal-free Euclidean noise subspace can be identified such that only second order moments of the received waveform need to be computed. The proposed method is nondata-aided (NDA), as well as constellation and phase independent, and only requires prior timing synchronization to fully exploit the cyclostationarity property. The estimator can also be applied to nonconstant modulus constellations without requiring any tuning, which is a feature not found in existing approaches. Implementation aspects and simpler suboptimal solutions are also provided.

  • Proyecto AVANT. Estudio de técnicas de sincronización para relaciones señal a ruido muy bajas. D12. Disseny i simulació dels algorismes de sincronització

     Lamarca Orozco, M. Meritxell; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-07-16
    Report

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    In this document, the synchronization algorithms developed during the project are presented and simulated. The studied algorithms are designed for a QS-CDMA system operating in the low SNR regime, i.e., at low Es/No values and/or with severe multiple access interference. Moreover, the proposed synchronization techniques must work correctly in the difficult mobility scenarios considered in the project (i.e., aeronautical, railroad and nautical scenarios).

  • Proyecto AVANT. Estudio de técnicas de sincronización para relaciones señal a ruido muy bajas. D11: Disseny del codificador i descodificador del turbo-codi de l'estàndard DVB-RCS

     Lamarca Orozco, M. Meritxell; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-07-16
    Report

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    This document contains the instructions for the design of the DVB-RCS turbo-code. Both the algorithmic and implementation issues are addressed in the document.

  • ANTARES Project (Phase B). Multiple acces scheme definition. Successive interference cancellation for A-CDMA

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-05-01
    Report

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  • ANTARES Project (Phase B). Physical layer definition. Equalization detailed design

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-08-01
    Report

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  • ANTARES Project (Phase B). Multiple access scheme definition. Impact of the aeronautical channel on the MAC techniques considered for the Antares forward and return links

     Font Segura, Josep; Lamarca Orozco, M. Meritxell; Matas Navarro, David; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-03-01
    Report

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  • LDPC performance in presence of impulse noise

     Lamarca Orozco, M. Meritxell; Ramirez Javega, Francisco; Matas Navarro, David; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-11-02
    Report

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  • ANTARES Project (Phase B). Physical layer definition. Payload carrier synchronization for the Antares TDMA return link

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-08-01
    Report

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  • ANTARES Project (Phase B). Multiple acces scheme definition. Spectral efficiency analysis of the MAC techniques considered for the Antares forward and return links

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-07-01
    Report

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  • ANTARES Project (Phase B). Multiple acces scheme definition. Diverse trade-offs analysis for TDMA and CDMA

     Font Segura, Josep; Matas Navarro, David; Ramirez Javega, Francisco; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2010-03-01
    Report

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  • Access to the full text
    Multipolling and OFDMA Reservation Protocol for IEEE 802.11 Networks  Open access

     Pérez Diaz de Cerio, David; Valenzuela Gonzalez, Jose Luis; Villares Piera, N. Javier
    IEEE International Symposium on Wireless Communication Systems
    Presentation's date: 2009-09-01
    Presentation of work at congresses

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    This paper presents an efficient multipolling scheme that improves the IEEE 802.11 MAC protocol efficiency and does not suffer from the hidden terminal problem or inefficient channel usage problems. To design an efficient polling scheme, the access point (AP) needs to obtain information about the current transmission status and channel state for each station. In this new scheme, we propose the use of multipolling frames in the downlink and Orthogonal Frequency Division Multiple Access (OFDMA) for the uplink reservation frames in order to reduce signaling overhead.

  • PROCESSAMENT DEL SENYAL EN COMUNICACIONS

     Rey Micolau, Francesc; Agustin de Dios, Adrian; Villares Piera, N. Javier; Vazquez Grau, Gregorio; Cabrera Bean, Margarita Asuncion; Riba Sagarra, Jaume; Vidal Manzano, Jose; Rodriguez Fonollosa, Javier; Garcia Ordoñez, Luis; Ramirez Javega, Francisco; Muñoz Medina, Olga; Matas Navarro, David; Font Segura, Josep; Silva Pereira, Silvana; Fernandez Rubio, Juan-antonio; Lamarca Orozco, M. Meritxell; Pages Zamora, Alba Maria; Sala Alvarez, Jose
    Participation in a competitive project

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  • DA-GLRT burst detection and synchronization based on a chirp-like preamble

     Lamarca Orozco, M. Meritxell; Lopez Salcedo, Jose Antonio; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier; Jalón, A; Rodríguez, E
    International Workshop on Signal Processing for Space Communications
    Presentation's date: 2008-10-08
    Presentation of work at congresses

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    A specific preamble for the tasks of signal detection and synchronization in burst digital communications is presented. The preamble resembles a chirp signal used in RADAR applications. Its main benefit is that it allows the application of the Generalized Likelihood Ratio Test in an efficient manner, as well as the derivation of closed-form estimators for the synchronization parameters, as shown in the paper. The proposal can be an alternative to turbo-synchronization in very low Eb/N0 scenarios.

  • Access to the full text
    A rain and scintillation Ka-band channel simulator  Open access

     Sala Alvarez, Jose; Lamarca Orozco, M. Meritxell; López, J. A.; Rey Micolau, Francesc; Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Villares Piera, N. Javier; Jalón, A; Rodríguez, E
    International Workshop on Signal Processing for Space Communications
    Presentation's date: 2008-10-07
    Presentation of work at congresses

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    This paper describes the implementation of a Ka-band satellite channel simulator with emphasis on the synthesis of scintillation processes. The problem becomes one of generating a given probability density function, the Moulsley-Vilar distribution, with a specified power spectral density using aWiener model based on orthogonal Hermite polynomials for the nonlinearity. A numerical procedure is devised to calculate the filter and non-linearity coefficients of the Wiener model. The generation of rain processes conforms to the Maseng-Bakken model.

  • Pulsar Navigation

     Josep, Sala; Sala Alvarez, Jose; Urruela, Andreu; Villares Piera, N. Javier; Romeu Robert, Jordi; Blanch Boris, Sebastian; Estalella Boadella, Robert; Paredes, Josep M
    ACT Workshop on Innovative Concepts 2008
    Presentation of work at congresses

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  • Informe Número 1: Projecte SETRAM

     Sala Alvarez, Jose; Rey Micolau, Francesc; Riba Sagarra, Jaume; Villares Piera, N. Javier; Lamarca Orozco, M. Meritxell; Vazquez Grau, Gregorio
    Date: 2008-10-01
    Report

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  • Pulsar navigation

     Sala Alvarez, Jose; Urruela Planas, Andreu; Villares Piera, N. Javier; Romeu Robert, Jordi; Blanch Boris, Sebastian; Estalella Boadella, Robert; Paredes, J. M.
    Acta Futura
    Date of publication: 2008-12-31
    Journal article

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    This paper evaluates the fundamental performance bounds, signal processing and technological complexity associated with the synchronization to radio and X-ray pulsars as well as its impact on the positioning accuracy of an autonomous spacecraft navigation system. Performance analysis of synchronization and location algorithms builds on Maximum Likelihood (ML) estimation which provides, asymptotically, unbiased minimum variance estimates with mean square error strictly approaching the Cramer-Rao Lower Bound (CRLB).

  • Nota tècnica 1: projecte SETRAM

     Sala Alvarez, Jose; Riba Sagarra, Jaume; Rey Micolau, Francesc; Villares Piera, N. Javier; Vazquez Grau, Gregorio; Lamarca Orozco, M. Meritxell
    Date: 2008-02-26
    Report

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    Un dels aspectes més crítics per assolir una definició avançada i realista del sistema SETRAM és la identificació de les tecnologies més adequades per a la localització d’usuaris mòbils, des de les ja existents (aplicables tant a la localització individual com agregada) fins a les més el.laborades per a la seva aplicació específica i exclusiva en aquest sistema.

    Nota tècnica inici de projecte SETRAM (CIDEM)

  • D2. Estructuras de detector multiusuario para CDMA síncrono y asíncrono

     Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2008-11-10
    Report

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  • D3. Sincronización robusta de frecuencia y fase para M-PSK sobre CDMA

     Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2008-11-10
    Report

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  • D1. Estudio de códigos PN para mejorar el ensanchado y la eficiencia espectral del sistema CDMA síncrono y asíncrono

     Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2008-11-10
    Report

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  • Foundations and Methodologies for Future Communication and Sensor Networks (COMONSENS)

     Pages Zamora, Alba Maria; Rodriguez Fonollosa, Javier; Muñoz Medina, Olga; Vidal Manzano, Jose; Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio; Rey Micolau, Francesc; Villares Piera, N. Javier; Vazquez Grau, Gregorio; Lamarca Orozco, M. Meritxell; Sala Alvarez, Jose; Riba Sagarra, Jaume
    Participation in a competitive project

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  • Diccionari de Telecomunicacions

     Aguilar Igartua, Mónica; Alcober Segura, Jesus Angel; Altes Bosch, Jorge; Aragones Cervera, Xavier; Artigas Garcia, David; Bardes Llorensi, Daniel; Barlabe Dalmau, Antoni; Bragos Bardia, Ramon; Calderer Cardona, Josep; Cardama Aznar, Angel; Casademont Serra, Jordi; Casals Ibañez, Lluis; Comeron Tejero, Adolfo; Cotrina Navau, Josep; Cruz Llopis, Luis Javier de La; Dios Otin, Victor Federico; Duxans Barrobes, Helena; Esparza Martin, Oscar; Esquerra Llucià, Ignasi; Garcia Vizcaino, David; Garcies Salva, Pau; Gomez Montenegro, Carlos; Gorricho Moreno, Juan Luis; Guinjoan Gispert, Francisco; Hesselbach Serra, Xavier; Liria Righetti, Antoni; Lopez Salcedo, Jose Antonio; Madrenas Boadas, Jordi; Madueño Ruiz, María Isabel; Mestre Pons, Francesc Xavier; Monte Moreno, Enrique; Morros Rubió, Josep Ramon; Muñoz Tapia, Jose Luis; Pallares Segarra, Esteve; Pons Nin, Joan; Recolons Martos, Jaume; Rincon Rivera, David; Riu Costa, Pere Joan; Ruiz Vela, Inmaculada; Pradell Cara, Lluis; Pascual Iserte, Antonio; Prat Viñas, Luis; Rey Micolau, Francesc; Villares Piera, N. Javier
    Date of publication: 2007-03
    Book

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  • Symbol-rate second-order blind channel estimation in coded transmissions

     Villares Piera, N. Javier
    IEEE International Conference on Acoustics, Speech, and Signal Processing
    Presentation of work at congresses

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  • ADAPTIVE MULTICARRIER DEMODULATOR & DECODER DVB-RCS1 DESIGN DOCUMENT

     Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Riba Sagarra, Jaume; Josep, Sala; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2007-02
    Report

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  • The Gaussian assumption in second-order estimation problems in digital communications

     Villares Piera, N. Javier; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2007-10
    Journal article

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    This paper deals with the goodness of the Gaussian assumption when designing second-order blind estimation methods in the context of digital communications. The low- and high-signal-to-noise ratio (SNR) asymptotic performance of the maximum likelihood estimator - derived assuming Gaussian transmitted symbols - is compared with the performance of the optimal second-order estimator, which exploits the actual distribution of the discrete constellation. The asymptotic study concludes that the Gaussian assumption leads to the optimal second-order solution if the SNR is very low or if the symbols belong to a multilevel constellation such as quadrature-amplitude modulation (QAM) or amplitude-phase-shift keying (APSK). On the other hand, the Gaussian assumption can yield important losses at high SNR if the transmitted symbols are drawn from a constant modulus constellation such as phase-shift keying (PSK) or continuous-phase modulations (CPM). These conclusions are illustrated for the problem of direction-of-arrival (DOA) estimation of multiple digitally-modulated signals.

  • Informe final. Demostrador de serveis Galileo per Catalunya

     Calvo Muntaner, Eduard; Carlavilla Márquez, Màxim; Lamarca Orozco, M. Meritxell; Lopez Salcedo, Jose Antonio; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2007-09-25
    Report

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  • Seguiment predictiu de tràfic amb localització de dispositius mòbils (SETRAM)

     Sala Alvarez, Jose; Rey Micolau, Francesc; Villares Piera, N. Javier; Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Lamarca Orozco, M. Meritxell
    Participation in a competitive project

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  • SPROACTIVE: Signal Processing Advanced techniques for CogniTIVE radio systems. Técnicas avanzadas de procesado de señal para sistemas de radio cognitive - II

     Villares Piera, N. Javier; Font Segura, Josep; Lamarca Orozco, M. Meritxell; Matas Navarro, David; Ramirez Javega, Francisco; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio
    Participation in a competitive project

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  • Simulations Results Document

     Lamarca Orozco, M. Meritxell; López-Salcedo, J A; Lopez Salcedo, Jose Antonio; Riba Sagarra, Jaume; Rey Micolau, Francesc; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2006-04
    Report

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  • Requirements Revision and Design Inputs

     Lamarca Orozco, M. Meritxell; López-Salcedo, J A; Lopez Salcedo, Jose Antonio; Riba Sagarra, Jaume; Rey Micolau, Francesc; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2006-03
    Report

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  • Simulation Results with Propagation, Non Linear and SS Modem Impairment Effects

     Lamarca Orozco, M. Meritxell; López-Salcedo, J A; Lopez Salcedo, Jose Antonio; Riba Sagarra, Jaume; Rey Micolau, Francesc; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2006-06
    Report

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  • Channel Simulator Interface Document

     Sala Alvarez, Jose; Lamarca Orozco, M. Meritxell; Lopez Salcedo, Jose Antonio; Muntaner, Enric; Rey Micolau, Francesc; Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Villares Piera, N. Javier; Bonet Domènech, Josep; Muntane Calvo, Enrique
    Date: 2005-09
    Report

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  • Development of a satellite railroad channel simulator

     Bonet Domènech, Josep; Muntane Calvo, Enrique; Lamarca Orozco, M. Meritxell; Rey Micolau, Francesc; Villares Piera, N. Javier
    Date: 2005-05
    Report

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  • UPC contrinution to ESA proposal Study of enhanced digital transmisión techniques for broadband satellite digital transmissions

     Sala Alvarez, Jose; Vazquez Grau, Gregorio; Lamarca Orozco, M. Meritxell; Lopez Salcedo, Jose Antonio; Riba Sagarra, Jaume; Villares Piera, N. Javier; Rey Micolau, Francesc; Muntaner, Enric; Bonet Domènech, Josep; Muntane Calvo, Enrique
    Date: 2005-07
    Report

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  • Adaptive Multicarrier Demodulator & Decoder DVB-RCS1 Definition

     Lamarca Orozco, M. Meritxell; López-Salcedo, J A; Lopez Salcedo, Jose Antonio; Muntaner, E; Rey Micolau, Francesc; Riba Sagarra, Jaume; Sala Alvarez, Jose; Vazquez Grau, Gregorio; Villares Piera, N. Javier; Muntane Calvo, Enrique
    Date: 2005-12
    Report

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  • SAMPLE COVARIANCE BASED PARAMETER ESTIMATION FOR DIGITAL COMMUNICATIONS  Open access

     Villares Piera, N. Javier
    Defense's date: 2005-09-21
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    En aquesta tesi s'estudia el problema d'estimació cega de segon ordre en comunicacions digitals. En aquest camp, els símbols transmesos esdevenen paràmetres no desitjats (nuisance parameters) d'estadística no gaussiana que degraden les prestacions de l'estimador. En aquest context, l'estimador de màxima versemblança (ML) és normalment desconegut excepte si la relació senyal-soroll (SNR) és prou baixa. En aquest cas particular, l'estimador ML és una funció quadràtica del vector de dades rebudes o, equivalentment, una transformació lineal de la matriu de covariància mostral. Aquesta característica es compartida per altres estimadors importants basats en el principi de màxima versemblança com ara l'estimador ML gaussià (GML) i l'estimador ML condicional (CML). Així mateix, l'estimador MUSIC, i altres mètodes de subespai relacionats amb ell, es basen en la diagonalització de la matriu de covariància mostral. En aquest marc, l'aportació principal d'aquesta tesi és la deducció i avaluació de l'estimador òptim de segon ordre per qualsevol SNR i qualsevol distribució dels nuisance parameters.El disseny d'estimadors quadràtics en llaç obert i llaç tancat s'ha plantejat de forma unificada. Pel que fa als estimadors en llaç obert, s'han derivat els estimadors de mínim error quadràtic mig i mínima variància considerant que els paràmetres d'interès són variables aleatòries amb una distribució estadística coneguda a priori però, altrament, arbitrària. A partir d'aquest plantejament Bayesià, els estimadors en llaç tancat es poden obtenir suposant que la distribució a priori dels paràmetres és altament informativa. En aquest model de petit error, el millor estimador quadràtic no esbiaixat, anomenat BQUE, s'ha formulat sense convenir cap estadística particular pels nuisance parameters. Afegit a això, l'anàlisi de l'estimador BQUE ha permès calcular quina és la fita inferior que no pot millorar cap estimador cec que utilitzi la matriu de covariància mostral. Probablement, el resultat principal de la tesi és la demostració de què els estimadors quadràtics són capaços d'utilitzar la informació estadística de quart ordre dels nuisance parameters. Més en concret, s'ha demostrat que tota la informació no gaussiana de les dades que els mètodes de segon ordre són capaços d'aprofitar apareix reflectida en els cumulants de quart ordre dels nuisance parameters. De fet, aquesta informació de quart ordre esdevé rellevant si el mòdul dels nuisance parameters és constant i la SNR és moderada o alta. En aquestes condicions, es demostra que la suposició gaussiana dels nuisance parameters dóna lloc a estimadors quadràtics no eficients. Un altre resultat original que es presenta en aquesta memòria és la deducció del filtre de Kalman estès de segon ordre, anomenat QEKF. L'estudi del QEKF assenyala que els algoritmes de seguiment (trackers) de segon ordre poden millorar simultàniament les seves prestacions d'adquisició i seguiment si la informació estadística de quart ordre dels nuisance parameters es té en compte. Una vegada més, aquesta millora és significativa si els nuisance parameters tenen mòdul constant i la SNR és prou alta. Finalment, la teoria dels estimadors quadràtics plantejada s'ha aplicat en alguns problemes d'estimació clàssics en l'àmbit de les comunicacions digitals com ara la sincronització digital no assistida per dades, el problema de l'estimació del temps d'arribada en entorns amb propagació multicamí, la identificació cega de la resposta impulsional del canal i, per últim, l'estimació de l'angle d'arribada en sistemes de comunicacions mòbils amb múltiples antenes. Per cadascuna d'aquestes aplicacions, s'ha realitzat un anàlisi intensiu, tant numèric com asimptòtic, de les prestacions que es poden aconseguir amb mètodes d'estimació de segon ordre.

    This thesis deals with the problem of blind second-order estimation in digital communications. In this field, the transmitted symbols appear as non-Gaussian nuisance parameters degrading the estimator performance. In this context, the Maximum Likelihood (ML) estimator is generally unknown unless the signal-to-noise (SNR) is very low. In this particular case, if the SNR is asymptotically low, the ML solution is quadratic in the received data or, equivalently, linear in the sample covariance matrix. This significant feature is shared by other important ML-based estimators such as, for example, the Gaussian and Conditional ML estimators. Likewise, MUSIC and other related subspace methods are based on the eigendecomposition of the sample covariance matrix. From this background, the main contribution of this thesis is the deduction and evaluation of the optimal second-order parameter estimator for any SNR and any distribution of the nuisance parameters.A unified framework is provided for the design of open- and closed-loop second-order estimators. In the first case, the minimum mean square error and minimum variance second-order estimators are deduced considering that the wanted parameters are random variables of known but arbitrary prior distribution. From this Bayesian approach, closed-loop estimators are derived by imposing an asymptotically informative prior. In this small-error scenario, the best quadratic unbiased estimator (BQUE) is obtained without adopting any assumption about the statistics of the nuisance parameters. In addition, the BQUE analysis yields the lower bound on the performance of any blind estimator based on the sample covariance matrix.Probably, the main result in this thesis is the proof that quadratic estimators are able to exploit the fourth-order statistical information about the nuisance parameters. Specifically, the nuisance parameters fourth-order cumulants are shown to provide all the non-Gaussian information that is utilizable for second-order estimation. This fourth-order information becomes relevant in case of constant modulus nuisance parameters and medium-to-high SNRs. In this situation, the Gaussian assumption is proved to yield inefficient second-order estimates.Another original result in this thesis is the deduction of the quadratic extended Kalman filter (QEKF). The QEKF study concludes that second-order trackers can improve simultaneously the acquisition and steady-state performance if the fourth-order statistical information about the nuisance parameters is taken into account. Once again, this improvement is significant in case of constant modulus nuisance parameters and medium-to-high SNRs.Finally, the proposed second-order estimation theory is applied to some classical estimation problems in the field of digital communications such as non-data-aided digital synchronization, the related problem of time-of-arrival estimation in multipath channels, blind channel impulse response identification, and direction-of-arrival estimation in mobile multi-antenna communication systems. In these applications, an intensive asymptotic and numerical analysis is carried out in order to evaluate the ultimate limits of second-order estimation.

  • Access to the full text
    Second-order parameter estimation  Open access

     Villares Piera, N. Javier; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2005-07
    Journal article

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    This work provides a general framework for the design of second-order blind estimators without adopting any approximation about the observation statistics or the a priori distribution of the parameters. The proposed solution is obtained minimizing the estimator variance subject to some constraints on the estimator bias. The resulting optimal estimator is found to depend on the observation fourth-order moments that can be calculated analytically from the known signal model. Unfortunately, in most cases, the performance of this estimator is severely limited by the residual bias inherent to nonlinear estimation problems. To overcome this limitation, the second-order minimum variance unbiased estimator is deduced from the general solution by assuming accurate prior information on the vector of parameters. This small-error approximation is adopted to design iterative estimators or trackers. It is shown that the associated variance constitutes the lower bound for the variance of any unbiased estimator based on the sample covariance matrix. The paper formulation is then applied to track the angle-of-arrival (AoA) of multiple digitally-modulated sources by means of a uniform linear array. The optimal second-order tracker is compared with the classical maximum likelihood (ML) blind methods that are shown to be quadratic in the observed data as well. Simulations have confirmed that the discrete nature of the transmitted symbols can be exploited to improve considerably the discrimination of near sources in medium-to-high SNR scenarios.

    This work provides a general framework for the design of second-order blind estimators without adopting any approximation about the observation statistics or the a priori distribution of the parameters. The proposed solution is obtained minimizing the estimator variance subject to some constraints on the estimator bias. The resulting optimal estimator is found to depend on the observation fourth-order moments that can be calculated analytically from the known signal model. Unfortunately, in most cases, the performance of this estimator is severely limited by the residual bias inherent to nonlinear estimation problems. To overcome this limitation, the second-order minimum variance unbiased estimator is deduced from the general solution by assuming accurate prior information on the vector of parameters. This small-error approximation is adopted to design iterative estimators or trackers. It is shown that the associated variance constitutes the lower bound for the variance of any unbiased estimator based on the sample covariance matrix. The paper formulation is then applied to track the angle-of-arrival (AoA) of multiple digitally-modulated sources by means of a uniform linear array. The optimal second-order tracker is compared with the classical maximum likelihood (ML) blind methods that are shown to be quadratic in the observed data as well. Simulations have confirmed that the discrete nature of the transmitted symbols can be exploited to improve considerably the discrimination of near sources in medium-to-high SNR scenarios.

  • Mesurement Concept Definition

     Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2005-10
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  • Measurement Concept Simulation Results

     Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2005-10
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  • Simulation with FM and dynamic traffic

     Riba Sagarra, Jaume; Vazquez Grau, Gregorio; Villares Piera, N. Javier
    Date: 2005-10
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  • GALILEO ADVANCED CONCEPTS

     Riba Sagarra, Jaume; Villares Piera, N. Javier; Rey Micolau, Francesc
    Participation in a competitive project

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