Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 147 results
  • Cramér-Rao lower bound for breakpoint distance estimation in a path-loss model

     Castro Arvizu, J.M.; Closas Gómez, Pau; Fernandez Rubio, Juan-antonio
    IEEE International Conference on Communications
    p. 176-180
    DOI: 10.1109/ICCW.2014.6881192
    Presentation's date: 2014-06
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper addresses the problem of determining the Cramér-Rao lower bound (CRLB) for the parameters and breakpoint distance in a Path-Loss Channel model for Received Signal Strength (RSS) measurements. The path loss model is usually assumed for corrupted RSS measurements due to the shadow fading channel feature. In this paper the two-slope path loss model is considered, in which RSS measurements are modeled differently for close and far distances. Closed-form expressions for the CRLB parameters are derived for unknown breakpoint distance. For unknown parameters and breakpoint distance value, a Bayesian estimation method is proposed. The CRLB is then compared with the performance of the herein proposed method. The comparison illustrates convergence and efficiency of the Bayesian estimator.

  • Deliverable M43 (project TUCAN3G). Multiple flows control management

     Muñoz Medina, Olga; Pascual Iserte, Antonio; Fernandez Rubio, Juan-antonio; Marques, Antonio G.; Figuera, Carlos; Kilgour, Kit; Ratanov, A.; Tupayachi Calderón, Omar; Ueunten, Antonio
    Date: 2014-01
    Report

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Access to the full text
    Bayesian filtering for nonlinear state-space models in symmetric alpha-stable measurment noise  Open access

     Vila Valls, Jordi; Fernandez Prades, Carles; Closas Gómez, Pau; Fernandez Rubio, Juan-antonio
    European Signal Processing Conference
    p. 674-678
    Presentation's date: 2011-10-02
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Bayesian ltering appears in many signal processing problems,reason why it attracted the attention of many researchers to develop efficient algorithms, yet computationally a ordable. In many real systems, it is appropriate to consider α-stable noise distributions to model possible outliers or impulsive behavior in the measurements. In this paper, we consider a nonlinear state-space model with Gaussian process noise and symmetric α-stable measurement noise. To obtain a robust estimation framework we consider that both process and measurement noise statistics are unknown. Using the product property of α-stable distributions we rewrite the measurement noise in a conditionally Gaussian form. Within this framework, we propose an hybrid sigma-point/Monte Carlo approach to solve the Bayesian ltering problem, what leads to a robust method against both outliers and a weak knowledge of the system.

  • Macrocelulas y Femtocelulas en Sistemas con Técnicas Avanzadas de Coordinación de la Interferencia y Cooperación

     Vidal Manzano, Jose; Rodriguez Fonollosa, Javier; Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio; Pages Zamora, Alba Maria; Agustin de Dios, Adrian; Silva Pereira, Silvana; Garcia Ordoñez, Luis; Vila Valls, Jordi; Muñoz Medina, Olga
    Competitive project

     Share

  • FEMTOCELL-BASED NETWORK ENHANCEMENT BY INTERFERENCE MANAGEMENT AND COORDINATION OF INFORMATION FOR SEAMLESS CONNECTIVITY

     Muñoz Medina, Olga; Rodriguez Fonollosa, Javier; Agustin de Dios, Adrian; Fernandez Rubio, Juan-antonio; Vidal Manzano, Jose
    Competitive project

     Share

  • CramÉr¿Rao Bound Analysis of Positioning Approaches in GNSS Receivers

     Closas Gómez, Pau; Fernandez-Prades, C; Fernandez Rubio, Juan-antonio
    IEEE transactions on signal processing
    Vol. 57, num. 10, p. 3775-3786
    Date of publication: 2009-10
    Journal article

     Share Reference managers Reference managers Open in new window

  • PROCESSAMENT DEL SENYAL EN COMUNICACIONS

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

     Share

  • Bayesian signal processing techniques for GNSS receivers: from multipath mitigation to positioning  Open access

     Closas Gomez, Pau
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Aquesta tesi gira al voltant del disseny de receptors per a sistemes globals de navegació per satèl·lit (Global Navigation Satellite Systems, GNSS). El terme GNSS fa referència a tots aquells sistemes de navegació basats en una constel·lació de satèl·lits que emeten senyals de navegació útils per a posicionament. El més popular és l'americà GPS, emprat globalment. Els esforços d'Europa per a tenir un sistema similar veuran el seu fruit en un futur proper, el sistema s'anomena Galileo. Altres sistemes globals i regionals existeixen dissenyats per al mateix objectiu: calcular la posició dels receptors. Inicialment la tesi presenta l'estat de l'art en GNSS, a nivell de l'estructura dels actuals senyals de navegació i pel que fa a l'arquitectura dels receptors.El disseny d'un receptor per a GNSS consta d'un seguit de blocs funcionals. Començant per l'antena receptora fins al càlcul final de la posició del receptor, el disseny proporciona una gran motivació per a la recerca en diversos àmbits. Tot i que la cadena de Radiofreqüència del receptor també és comentada a la tesis, l'objectiu principal de la recerca realitzada recau en els algorismes de processament de senyal emprats un cop realitzada la digitalització del senyal rebut. En un receptor per a GNSS, aquests algorismes es poden dividir en dues classes: els de sincronisme i els de posicionament. Aquesta classificació correspon als dos grans processos que típicament realitza el receptor. Primer, s'estima la distancia relativa entre el receptor i el conjunt de satèl·lits visibles. Aquestes distancies es calculen estimant el retard patit pel senyal des de que és emès pel corresponent satèl·lit fins que és rebut pel receptor. De l'estimació i seguiment del retard se n'encarrega l'algorisme de sincronisme. Un cop calculades la distancies relatives als satèl·lits, multiplicant per la velocitat de la llum el retards estimats, l'algorisme de posicionament pot operar. El posicionament es realitza típicament pel procés de trilateralització: intersecció del conjunt d'esferes centrades als satèl·lits visibles i de radi les distancies estimades relatives al receptor GNSS. Així doncs, sincronització i posicionament es realitzen de forma seqüencial i ininterrompudament. La tesi fa contribucions a ambdues parts, com explicita el subtítol del document.Per una banda, la tesi investiga l'ús del filtrat Bayesià en el seguiment dels paràmetres de sincronisme (retards, desviaments Doppler i phases de portadora) del senyal rebut. Una de les fonts de degradació de la precisió en receptors GNSS és la presència de repliques del senyal directe, degudes a rebots en obstacles propers. És per això que els algorismes proposats en aquesta part de la tesi tenen com a objectiu la mitigació de l'efecte multicamí. La dissertació realitza una introducció dels fonaments teòrics del filtrat Bayesià, incloent un recull dels algorismes més populars. En particular, el Filtrat de Partícules (Particle Filter, PF) s'estudia com una de les alternatives més interessants actualment per a enfrontar-se a sistemes no-lineals i/o no-Gaussians. Els PF són mètodes basats en el mètode de Monte Carlo que realitzen una caracterització discreta de la funció de probabilitat a posteriori del sistema. Al contrari d'altres mètodes basats en simulacions, els PF tenen resultats de convergència que els fan especialment atractius en casos on la solució òptima no es pot trobar. En aquest sentit es proposa un PF que incorpora un seguit de característiques que el fan assolir millors prestacions i robustesa que altres algorismes, amb un nombre de partícules reduït. Per una banda, es fa un seguiment dels estats lineals del sistema mitjançant un Filtre de Kalman (KF), procediment conegut com a Rao-Blackwellization. Aquest fet provoca que la variància de les partícules decreixi i que un menor nombre d'elles siguin necessàries per a assolir una certa precisió en l'estimació de la distribució a posteriori. D'altra banda, un dels punts crítics en el disseny de PF és el disseny d'una funció d'importància (emprada per a generar les partícules) similar a l'òptima, que resulta ésser el posterior. Aquesta funció òptima no està disponible en general. En aquesta tesi, es proposa una aproximació de la funció d'importància òptima basada en el mètode de Laplace. Paral·lelament es proposen algorismes com l'Extended Kalman Filter (EKF) i l'Unscented Kalman Filter (UKF), comparant-los amb el PF proposat mitjançant simulacions numèriques.Per altra banda, la presentació d'un nou enfocament al problema del posicionament és una de les aportacions originals de la tesi. Si habitualment els receptors operen en dos passos (sincronització i posicionament), la proposta de la tesi rau en l'Estimació Directa de la Posició (Direct Position Estimation, DPE) a partir del senyal digital. Tenint en compte la novetat del mètode, es proporcionen motivacions qualitatives i quantitatives per a l'ús de DPE enfront al mètode convencional de posicionament. Se n'ha estudiat l'estimador de màxima versemblança (Maximum Likelihood, ML) i un algorisme per a la seva implementació pràctica basat en l'algorisme Accelerated Random Search (ARS). Els resultats de les simulacions numèriques mostren la robustesa de DPE a escenaris on el mètode convencional es veu degradat, com per exemple el cas d'escenaris rics en multicamí. Una de les reflexions fruit dels resultats és que l'ús conjunt dels senyals provinents dels satèl·lits visibles proporciona millores en l'estimació de la posició, doncs cada senyal està afectada per un canal de propagació independent. La tesi també presenta l'extensió de DPE dins el marc Bayesià: Bayesian DPE (BDPE). BDPE manté la filosofia de DPE, tot incloent-hi possibles fonts d'informació a priori referents al moviment del receptor. Es comenten algunes de les opcions com l'ús de sistemes de navegació inercials o la inclusió d'informació atmosfèrica. Tot i així, cal tenir en compte que la llista només està limitada per la imaginació i l'aplicació concreta on el marc BDPE s'implementi.Finalment, la tesi els límits teòrics en la precisió dels receptors GNSS. Alguns d'aquests límits teòrics eren ja coneguts, d'altres veuen ara la llum. El límit de Cramér-Rao (Cramér-Rao Bound, CRB) ens prediu la mínima variància que es pot obtenir en estimar un paràmetre mitjançant un estimador no esbiaixat. La tesi recorda el CRB dels paràmetres de sincronisme, resultat ja conegut. Una de les aportacions és la derivació del CRB de l'estimador de la posició pel cas convencional i seguint la metodologia DPE. Aquests resultats proporcionen una comparativa asimptòtica dels dos procediments pel posicionament de receptors GNSS. D'aquesta manera, el CRB de sincronisme pel cas Bayesià (Posterior Cramér-Rao Bound, PCRB) es presenta, com a límit teòric dels filtres Bayesians proposats en la tesi.

    This dissertation deals with the design of satellite-based navigation receivers. The term Global Navigation Satellite Systems (GNSS) refers to those navigation systems based on a constellation of satellites, which emit ranging signals useful for positioning. Although the american GPS is probably the most popular, the european contribution (Galileo) will be operative soon. Other global and regional systems exist, all with the same objective: aid user's positioning. Initially, the thesis provides the state-of-the-art in GNSS: navigation signals structure and receiver architecture. The design of a GNSS receiver consists of a number of functional blocks. From the antenna to the final position calculation, the design poses challenges in many research areas. Although the Radio Frequency chain of the receiver is commented in the thesis, the main objective of the dissertation is on the signal processing algorithms applied after signal digitation. These algorithms can be divided into two: synchronization and positioning. This classification corresponds to the two main processes typically performed by a GNSS receiver. First, the relative distance between the receiver and the set of visible satellites is estimated. These distances are calculated after estimating the delay suffered by the signal traveling from its emission at the corresponding satellite to its reception at the receiver's antenna. Estimation and tracking of these parameters is performed by the synchronization algorithm. After the relative distances to the satellites are estimated, the positioning algorithm starts its operation. Positioning is typically performed by a process referred to as trilateration: intersection of a set of spheres centered at the visible satellites and with radii the corresponding relative distances. Therefore, synchronization and positioning are processes performed sequentially and in parallel. The thesis contributes to both topics, as expressed by the subtitle of the dissertation.On the one hand, the thesis delves into the use of Bayesian filtering for the tracking of synchronization parameters (time-delays, Doppler-shifts and carrier-phases) of the received signal. One of the main sources of error in high precision GNSS receivers is the presence of multipath replicas apart from the line-of-sight signal (LOSS). Wherefore the algorithms proposed in this part of the thesis aim at mitigating the multipath effect on synchronization estimates. The dissertation provides an introduction to the basics of Bayesian filtering, including a compendium of the most popular algorithms. Particularly, Particle Filters (PF) are studied as one of the promising alternatives to deal with nonlinear/nonGaussian systems. PF are a set of simulation-based algorithms, based on Monte-Carlo methods. PF provide a discrete characterization of the posterior distribution of the system. Conversely to other simulation-based methods, PF are supported by convergence results which make them attractive in cases where the optimal solution cannot be analytically found. In that vein, a PF that incorporates a set of features to enhance its performance and robustness with a reduced number of particles is proposed. First, the linear part of the system is optimally handled by a Kalman Filter (KF), procedure referred to as Rao-Blackwellization. The latter causes a reduction on the variance of the particles and, thus, a reduction on the number of required particles to attain a given accuracy when characterizing the posterior distribution. A second feature is the design of an importance density function (from which particles are generated) close to the optimal, not available in general. The selection of this function is typically a key issue in PF designs. The dissertation proposes an approximation of the optimal importance function using Laplace's method. In parallel, Extended Kalman Filter (EKF) and Unscented Kalman Filter (UKF) algorithms are considered, comparing these algorithms with the proposed PF by computer simulations.On the other hand, a novel point of view in the positioning problem constitutes one of the original contributions of the thesis. Whereas conventional receivers operate in a two-steps procedure (synchronization and positioning), the proposal of the thesis is a Direct Position Estimation (DPE) from the digitized signal. Considering the novelty of the approach, the dissertation provides both qualitative and quantitative motivations for the use of DPE instead of the conventional two-steps approach. DPE is studied following the Maximum Likelihood (ML) principle and an algorithm based on the Accelerated Random Search (ARS) is considered for a practical implementation of the derived estimator. Computer simulation results carried show the robustness of DPE in scenarios where the conventional approach fails, for instance in multipath-rich scenarios. One of the conclusions of the thesis is that joint processing of satellite's signals provides enhance positioning performances, due to the independent propagation channels between satellite links. The dissertation also presents the extension of DPE to the Bayesian framework: Bayesian DPE (BDPE). BDPE maintains DPE's philosophy, including the possibility of accounting for sources of side/prior information. Some examples are given, such as the use of Inertial Measurement Systems and atmospheric models. Nevertheless, we have to keep in mind that the list is only limited by imagination and the particular applications were BDPE is implemented. Finally, the dissertation studied the theoretical lower bounds of accuracy of GNSS receivers. Some of those limits were already known, others see the light as a result of the research reported in the dissertation. The Cramér-Rao Bound (CRB) is the theoretical lower bound of accuracy of any unbiased estimator of a parameter. The dissertation recalls the CRB of synchronization parameters, result already known. A novel contribution ofthe thesis is the derivation of the CRB of the position estimator for either conventional and DPE approaches. These results provide an asymptotical comparison of both GNSS positioning approaches. Similarly, the CRB of synchronization parameters for the Bayesian case (Posterior Cramér-Rao Bound, PCRB) is given, used as a fundamental limit of the Bayesian filters proposed in the thesis.

  • Access to the full text
    A game theoretical algorithm for joint power and topology control in distributed WSN  Open access

     Closas Gomez, Pau; Pages Zamora, Alba Maria; Fernandez Rubio, Juan-antonio
    IEEE International Conference on Acoustics, Speech and Signal Processing
    p. 2765-2768
    DOI: 10.1109/ICASSP.2009.4960196
    Presentation's date: 2009-04-20
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    In this paper, the issue of network topology control in wireless networks using a fully distributed algorithm is considered. Whereas the proposed distributed algorithm is designed applying game theory concepts to design a non-cooperative game, network connectivity is guaranteed based on asymptotic results of network connectivity. Simulations show that for a relatively low node density, the probability that the proposed algorithm leads to a connected network is close to one.

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

     Rodriguez Fonollosa, Javier; Pages Zamora, Alba Maria; 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
    Competitive project

     Share

  • D4.2. Report on the analysis of modulation techniques and radio technologies

     MENGONI, F; CALABRO, F; BARTOLI, F; PIERROT, J; DANIELE, N; HASLER, M; AJDARI, A RAD; Pages Zamora, Alba Maria; Closas Gomez, Pau; ESTELLERS, Virginia; Silva Pereira, Silvana; Fernandez Rubio, Juan-antonio; BARBAROSSA, S et al
    Date: 2007-08
    Report

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • METODOS SUB-BANDA PARA CONFORMACIÓN DE HAZ CON SEÑALES ACÚSTICAS.

     SATUE VILLAR, ANTONIO
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • Maximum likelihood estimation of position in GNSS

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio; Fernandez Prades, Carlos; Fernandez-Prades, C
    IEEE signal processing letters
    Vol. 14, num. 5, p. 359-362
    Date of publication: 2007-05
    Journal article

     Share Reference managers Reference managers Open in new window

  • D3.1. Intermediate report on algorithms development

     Barbarossa, S; Scutari, G; Pescosolido, L; Sardellitti, S; Battisti, T; Pages Zamora, Alba Maria; Closas Gomez, Pau; Silva Pereira, Silvana; Maribel, Madueño; Vidal Manzano, Jose; Fernandez Rubio, Juan-antonio
    Date: 2007-03
    Report

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Coupling noise effect in self¿synchronizing wireless sensor networks

     Closas Gomez, Pau; Calvo Page, Eduardo; Fernández Rubio, Juan A; Fernandez Rubio, Juan-antonio; Pages Zamora, Alba Maria
    8th IEEE Workshop on Signal Processing Advances in Wireless Communications
    p. 1-5
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • TEC2006-06481 LÍMITES FUNDAMENTALES DE LA TEORÍA DE LA INFORMACIÓN DE REDES

     Pages Zamora, Alba Maria; Rodriguez Fonollosa, Javier; Muñoz Medina, Olga; Vidal Manzano, Jose; Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio
    Competitive project

     Share

  • On the Maximum Likelihood Estimation of Position

     Fernandez Rubio, Juan-antonio
    The Institute of Navigation International Technical Meeting
    Presentation's date: 2006-09-26
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Wireless Sensor Networks with Self-Organization Capabilities for Critical and Emergency Applications (WINSOC)

     Closas Gomez, Pau; Pages Zamora, Alba Maria; Vidal Manzano, Jose; Fernandez Rubio, Juan-antonio
    Competitive project

     Share

  • Advanced signal processing techniques for global navigation satellite systems receivers

     Fernandez Prades, Carlos
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • Particle Filtering applied to Robust Multivariate Likelihood Optimization in the absence of a closed-form solution

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio
    Nonlinear Statistical Signal Processing Workshop
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Multipath Mitigation using Particle Filtering

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio; Ramirez Bellido, Alejandro
    The Institute of Navigation International Technical Meeting
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • LaViCAD: UN PUENTE ENTRE LA INSTRUMENTACIÓN Y EL ESTUDIO DE TEORÍA MATEMÁTICA DE COMUNICACIONES ANALÓGICAS Y DIGITALES

     Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio; Berzosa, Carlos Vargas; Francisco, Vargas Berzosa
    Congreso de Tecnologías Aplicadas a la Enseñanza de la Electrónica
    p. 1-10
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Bayesian DLL for Multipath Mitigation in Navigation Systems using Particle Filters

     Clos Costa, Daniel; Fernandez Rubio, Juan-antonio
    IEEE International Conference on Acoustics, Speech, and Signal Processing
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • On the Maximum Likelihood Estimation of Position

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio; Ramirez Bellido, Alejandro
    The Institute of Navigation International Technical Meeting
    p. 1800-1810
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Sequential Monte-Carlo approximation to the ML Time-delay Estimator in a Multipath Channel

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio
    IEEE Workshop on Signal Processing Advances in Wireless Communications
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Optimizing the Likelihood with Sequential Monte-Carlo methods

     Closas Gomez, Pau; Fernandez Rubio, Juan-antonio
    Simposium Nacional de la Unión Científica Internacional de Radio
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Nuevas estrategias para las telecomunicaciones a bordo de los buques

     MIRAVALLES ORTEGA, GERARDO
    Department of Nautical Sciences and Engineering, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • Comunicaciones ii, ejercicios resueltos

     Cabrera Bean, Margarita Asuncion; Rodriguez Fonollosa, Javier; Fonollosa, J; Fernandez Rubio, Juan-antonio; Riba Sagarra, Jaume
    Date of publication: 2005-09-30
    Book

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • ML estimator and hybrid beamformer for multipath and interference mitigation in GNSS receivers

     Seco Granados, Gonzalo; Fernandez Rubio, Juan-antonio; Fernandez Prades, Carlos
    IEEE transactions on signal processing
    Vol. 53, num. 3, p. 1194-1208
    Date of publication: 2005-05
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Time-Frequency Estimation in the COSPAS/SARSAT System Using Antenna Arrays: Variance Bounds and Algorithms

     Fernandez Rubio, Juan-antonio; Closas Gomez, Pau
    European Signal Processing Conference
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • A new approach to multichannel audio signal acquisition and subband processing

     Satué-Villar, Antonio; Fernandez Rubio, Juan-antonio
    European Signal Processing Conference
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • COMalaWEB Plataforma basada en noves tecnologies aplicades a la docéncia

     Fernandez Rubio, Juan-antonio; Ramirez Bellido, Alejandro; Cabrera Bean, Margarita Asuncion
    Jornada d'Innovació Docent UPC
    p. 1-6
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • New Trends In Global Navigation Systems: Implementation of a GPS Antenna Array Receiver

     Fernandez Prades, Carlos; Closas Gomez, Pau; Fernandez Rubio, Juan-antonio
    The Eighth International Symposium on Signal Processing and its Applications
    p. 1-4
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Advanced Signal Processing Techniques in Local User Terminals for Search and Rescue Systems Based on MEO Satellites

     Fernandez Prades, Carlos; Closas Gomez, Pau; Fernandez Rubio, Juan-antonio
    ION-GNSS 2005
    p. 1-5
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Environment Simulator for Audio Signals

     Satué-Villar, Antonio; Fernandez Rubio, Juan-antonio
    European Signal Processing Conference
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • TEC2004-04526 TRANSMISION COOPERATIVA PARA SISTEMAS DE COMUNICACION INALAMBRICOS DE BANDA ANCHA

     Vidal Manzano, Jose; Fernandez Rubio, Juan-antonio; Sala Alvarez, Jose; Riba Sagarra, Jaume; Muñoz Medina, Olga; Villares Piera, N. Javier; madueño ruiz, maria isabel; Agustin de Dios, Adrian; Garcia Ordoñez, Luis; Huerta Guillén, Jose Manuel
    Competitive project

     Share

  • Robust Space-Time Beamforming in GNSS by means of Second-Order Cone Programming

     Fernandez Prades, Carlos; Fernandez Rubio, Juan-antonio
    IEEE International Conference on Acoustics, Speech, and Signal Processing
    p. 1-4
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Multi-Frequency GPS/Galileo Receiver Design using Direct RF Sampling and Antenna Arrays

     Fernandez Prades, Carlos; Fernandez Rubio, Juan-antonio
    Third IEEE Sensor Array and Multichannel Signal Processing Workshop
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • LaViCAD: LABORATORIO VIRTUAL DE COMUNICACIONES ANALÓGICAS Y DIGITALES

     Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio; Berzosa, Carlos Vargas; Francisco, Vargas Berzosa; Gasull Llampallas, Antoni
    Congrés Internacional de Docència Universitària i Innovació
    p. 1-20
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Antenna Array Receiver for GNSS

     Fernandez Rubio, Juan-antonio; Ramirez González, Alejandro; Closas Gomez, Pau
    8th European Symposium on Global Navigation Satellite System
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • COMalaWEB: DESARROLLO DE HERRAMIENTAS DOCENTES MEDIANTE TECNOLOGÍAS WEB

     Fernandez Rubio, Juan-antonio; Cabrera Bean, Margarita Asuncion
    Congrés Internacional de Docència Universitària i Innovació
    p. 1-20
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Design of Local User Terminals for Search and Rescue Systems with MEO Satellites

     Fernandez Prades, Carlos; Closas Gomez, Pau; Fernandez Rubio, Juan-antonio; Seco Granados, Gonzalo; Stojkovic, Igor
    ESA Workshop on Satellite Navigation Technologies
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Plataforma basada en Noves Tecnologies Aplicades a la Docència

     Fernandez Rubio, Juan-antonio
    Competitive project

     Share

  • A Maximum Likelihood Approach to GNSS Synchronization Using Antenna Arrays

     Fernandez Prades, Carlos; Fernandez Rubio, Juan-antonio; Gonzalo, Seco
    Satellite Division Technical Meeting, ION GPS/GNSS
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • A Maximum Likelihood Approach to GNSS Synchronization Using Antenna Arrays

     Fernandez Prades, Carlos; Fernandez Rubio, Juan-antonio
    The Institute of Navigation International Technical Meeting
    p. 1-10
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Code-Timing Synchronization in DS-CDMA Systems Using Space-Time Diversity

     Seco Granados, Gonzalo; Fernandez Rubio, Juan-antonio; Swinlehurst, A Lee
    IEEE signal processing letters
    Vol. 81, num. 8, p. 1581-1602
    Date of publication: 2001-08
    Journal article

     Share Reference managers Reference managers Open in new window

  • Propagation experiments in the near-infrared along a 150 km path and from stars in the Canarian archipelago

     Comeron Tejero, Adolfo; Fernandez Rubio, Juan-antonio; Belmonte Molina, Aniceto; García, E; Prud'Homme, T; Sodnik, Z; Connor, C
    Eighth International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics
    p. 78-90
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Antenna Arrays for Multipath and Interference Mitigation in GNSS Receivers  Open access  awarded activity

     Seco Granados, Gonzalo
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Esta tesis aborda la sincronización de una o varias réplicas de una señal conocida recibidas en un entorno con propagación multicamino e interferencias direccionales. Uno de los hilos conductores de este trabajo es la aplicación sistemática del principio de máxima verosimilitud (ML) junto con un modelo de señal en el cual las armas espaciales no tienen estructura, y en cual el ruido es Gaussiano y presenta una matriz de correlación desconocida. Esta última suposición es fundamental a la hora de obtener estimadores capaces de atenuar las señales interferentes que presentan algún tipo de estructura, y esto se consigue sin necesidad de recurrir a la estimación de ciertos parámetros de dichas señales. Por otra parte, la suposición de que las armas espaciales carecen de estructura tiene ventajas desde un punto de vista práctico, al mismo tiempo que simplifica la estimación del resto de parámetros ya que las estimaciones de estas firmas se pueden calcular de forma cerrada. Esto constituye un primer paso hacia la eliminación de las búsquedas en múltiples dimensiones, que es otro de los objetivos perseguidos en este trabajo.En la primera parte de la tesis se deduce la solución de máxima verosimilitud para el problema general de estimación de retardos cuando el ruido tiene correlación espacial desconocida. Se demuestra que el criterio resultante para los retardos es consistente y asintóticamente eficiente, pero también es altamente no-lineal debido a la presencia del determinante de una matriz y no permite, por tanto, el uso de procedimientos sencillos de optimización. Asimismo, se demuestra y se argumenta intuitivamente que el criterio _ optimo ML se puede aproximar por una función de coste más sencilla que es asintóticamente equivalente. A diferencia de otros problemas de estimación, en el caso tratado aquí, el primer término del desarrollo de Taylor del estimador ML no conserva la eficiencia asintótica. La característica esencial de la nueva función de coste es que depende linealmente de la matriz de proyección sobre el subespacio de las señales y, por lo tanto, admite ser minimizada mediante el algoritmo IQML, que es eficiente desde el punto de vista computacional. Además, la existencia de métodos de inicialización sencillos y robustos a las interferencias, los cuales se basan en el uso de una matriz de pesos igual a la identidad y posiblemente también en el algoritmo ESPRIT, hace que el esquema de estimación propuesto pueda ser viable para un diseño práctico. La nueva función de coste se puede aplicar de la misma manera a la estimación del retardo en un canal FIR. En este caso, el algoritmo IQML se puede modificar de forma que, en cada iteración, la estimación del retardo se obtiene a partir de las raíces de un polinomio cuyo orden es igual a la longitud del canal.El objetivo perseguido por los estimadores presentados en la segunda parte de la tesis es aprovechar una particularidad de los sistemas GNSS (Global Navigation Satellite Systems), que consiste en que la dirección de llegada de la señal directa puede ser conocida a priori. Basándose en esta información adicional y suponiendo que el array está calibrado, se propone un modelo simplificado, aunque al mismo tiempo aproximado, para la señal recibida. En este modelo todas las señales excepto la señal directa se engloban en un término con correlación espacial desconocida. Se analizan los estimadores ML del retardo y de la fase de portadora de la señal directa. El sesgo producido por las componentes multicamino al utilizar estos estimadores se reduce de forma muy importante con respecto al sesgo que sufren otros métodos. De hecho, el error cuadrático medio de los estimadores propuestos es en muchas ocasiones muy próximo o incluso inferior al mínimo error que se puede alcanzar con modelos más detallados del canal multicamino. Asimismo, se presentan dos algoritmos de estimación del retardo basados en el cálculo de las raíces de un polinomio. Se demuestra también que las estimaciones ML se pueden obtener a partir de la señal de salida de un conformador de haz híbrido. Debido a que el propio conformador depende de las estimaciones del retardo y de la amplitud de la señal directa, el uso de un algoritmo iterativo surge de forma natural. La formulación mediante el conformador híbrido proporciona una interpretación alternativa interesante de la estimación ML, y podrá ser apropiada para una realización práctica. Finalmente, se demuestra analíticamente y numéricamente que el estimador propuesto para el retardo es robusto frente a errores en el valor nominal del vector de enfoque de la señal directa, y se presenta una manera de extender el margen tolerable de errores de apuntamiento.En la última parte de la tesis se trata la sincronización de un usuario deseado que transmite una secuencia de entrenamiento conocida en un sistema de comunicaciones DS-CDMA.El modelo de señal utilizado agrupa el ruido, y la interferencia externa y de acceso múltiple en un término de ruido equivalente que presenta una matriz de correlación espacio-temporal desconocida. Partiendo de este modelo, se deduce un estimador del retardo que es una aproximación para un numero grande de muestras del estimador ML exacto y que es apropiado para canales con desvanecimientos lentos y noselectivos en frecuencia. El estimador propuesto es una técnica de un solo usuario y es resistente al efecto near-far. Su importancia radica en el hecho de que aprovecha la estructura de las señales en el dominio temporal y espacial, lo que contrasta con otros métodos existentes que, a pesar de utilizar un array de antenas, sólo utilizan la estructura de las señales en uno de los dos dominios. En un sistema de comunicaciones móviles, el usuario deseado está interferido por un número generalmente elevado de señales de otros usuarios y por posibles interferencias externas. En concordancia con este hecho, los resultados numéricos han mostrado que el uso conjunto de todos los grados de libertad espacio-temporales es indispensable para la correcta adquisición y seguimiento del retardo en sistemas con una carga elevada de usuarios y/o en presencia de interferencias externas.

    The thesis deals with the synchronization of one or several replicas of a known signal received in a scenario with multipath propagation and directional interference. A connecting theme along this work is the systematic application of the maximum likelihood (ML) principle together with a signal model in which the spatial signatures are unstructured and the noise term is Gaussian with an unknown correlation matrix. This last assumption is key in obtaining estimators that are capable of mitigating the disturbing signals that exhibit certain structure. On the other hand, the assumption of unstructured spatial signatures is interesting from a practical standpoint and facilitates the estimation. The elimination of the multidimensional searches required by many estimators is one of the main objectives of the thesis.In the first part of the thesis, the maximum likelihood solution to the general time delay estimation problem for the case of noise with unknown spatial correlation is derived. The resulting criterion for the delays is shown to be consistent and asymptotically efficient; but it is highly non-linear, and does not lead to simple optimization procedures. It is shown that the optimal ML criterion can be approximated by an asymptotically equivalent cost function. The cost function depends linearly on the projection matrix onto the subspace spanned by the signals, and hence it can be minimized using the IQML algorithm. The existence of simple initialization schemes based on identity weightings or ESPRIT makes the approach viable for practical implementation. The proposed cost function can be applied to the estimation of the delay in a FIR channel. In this case, each iteration of IQML comes down to rooting a polynomial.The goal of the estimators presented in the second part of the thesis is to take advantage of one particularity of the GNSS (Global Navigation Satellite Systems) systems, such as GPS and GLONASS, consisting in that the direction-of-arrival of the line-of-sight signal may be known a priori. A simplified and approximate model for the received signal is proposed. The ML estimators of the time delay and carrier phase of the direct signal largely reduce the bias produced by multipath components. Their RMSE is in many situations very close to or even better than the best possible performance attainable with more detailed models of the multipath channel. It is also shown that the ML estimates can be obtained from the output signal of a hybrid beamformer. In the last part of the thesis, the synchronization of a desired user transmitting a known training sequence in a DS-CDMA communication system is addressed. Multiple-access interference, external interference and noise are assumed to have unknown space-time correlation. A large-sample ML code-timing estimator that operates in frequency-nonselective, slowly fading channels is derived. It is a single-user and near-far resistant method. It is shown that the use of all spatial and temporal degrees of freedom is indispensable for the correct acquisition and tracking of the synchronization parameters in heavily loaded systems and/or in the presence of external interference.