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  • Wideband Cognitive Radio: Monitoring, Detection and Sparse Noise Subspace Communication

     Font Segura, Josep
    Defense's date: 2014-07-24
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    Estem envoltats de dispositius electrònics que utilitzen tecnologia sense fils, des del ratolí de l'ordinador que requereix petites quantitats d'informació, fins als nostres telèfons mòbil que demanen cada vegada més velocitat de dades. Fins avui, la coexistència de tants serveis ha estat garantida per una assignació fixa dels recursos freqüencials per part de les agències de regulació. Això ens ha portat a un atzucac, ja que l'espectre actual ha esdevingut un recurs car i escàs. Tanmateix, mesures recents dibuixen una situació molt diferent: de fet hi ha una utilització molt baixa de l'espectre per part dels sistemes amb llicència.La tecnologia de ràdio cognitiva promet millorar l'eficiència espectral dels futurs sistemes de comunicació sense fils. En teoria, un usuari secundari coneix perfectament la utilització de l'espectre, i és capaç de transmetre de manera oportuna sense degradar els sistemes primaris. A la pràctica, però, monitoritzar els recursos freqüencials, detectar-los i transmetre-hi són tasques difícils. Aquesta tesi tracta aquestes tres tasques en escenaris complicats com senyals de banda ampla, mostreig no uniforme, informació lateral imprecisa i canals selectius en freqüència.En la primera tasca de monitoritzar els recursos freqüencials, aquesta tesi desenvolupa els estimadors espectrals de periodograma i Capon en mostreig no uniforme a partir d'un ajust per correlació de les observacions linealment projectades. Es demostra que el mostreig no uniforme genera el fenomen d'increment de soroll, el qual és solucionat pels estimadors espectrals proposats, i a més a més és caracteritzat teòricament pel cas de Bernoulli, establint una equivalència entre el mostreig no uniforme i la relació senyal soroll (SNR).En la segona tasca de detectar els recursos disponibles, la tesi considera els problemes de detecció de senyals multifreqüència, avaluació de les prestacions asimptòtiques, i detecció de senyals cicloestacionàries. En detecció multifreqüència, es proposa una formulació unificada basada en el test generalitzat de màxima versemblança (GLRT), considerant diferents graus d'informació lateral, i efectuant estimació de màxima versemblança (ML) i d'ajust per correlació dels paràmetres desconeguts en mostreig uniforme i mostreig no uniforme, respectivament. Les prestacions asimptòtiques dels detectors són avaluades des de dues perspectives: el lema d'Stein, que permet descobrir la influència dels diferents paràmetres sobre els exponents de les probabilitats d'error; i la caracterització estadística asimptòtica del GLRT en mostreig no uniforme de Bernoulli, que permet derivar les parets de mostreig en incertesa de soroll, és a dir, aquelles densitats de mostreig per sota de les quals les probabilitats de detecció objectiu no són garantides. Finalment, la tesi explota les propietats cicloestacionàries dels senyals primaris: es deriva el test d'esfericitat quadràtica (QST), que és la divisió entre la mitjana quadràtica i la mitjana aritmètica dels autovalors de la matriu de correlació de les observacions; i també es deriva el GLRT en un model parametritzat del canal selectiu en freqüència, que explota l'estructura rang deficient de petites matrius de covariància espectral.En l'última tasca de transmetre en els recursos disponibles, es proposa en primer lloc un esquema de forma d'ona cicloestacionària per reduir la interferència que un usuari cognitiu pot causar a un altre usuari cognitiu inactiu que fa sensat de l'espectre, projectant les observacions sobremostrejades en un subespai reduït. En segon lloc, aquesta tesi deriva i caracteritza estadísticament la llargària mínima de descripció (MDL) d'esfericitat per estimar el subespai de senyal primària. I en tercer lloc, la tesi considera el problema d'optimització de forma d'ona de norma mínima amb informació lateral imperfecta, els beneficis del qual són els dels predictors lineals: resposta freqüencial plana i invariància a la rotació.

  • Nonuniform sampling walls in wideband signal detection

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

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    This work shows the existence of sampling walls in detection of wideband signals from Bernoulli nonuniform sampling (BNS) in the presence of noise uncertainty. A sampling wall is defined as the sampling density below which the target error probabilities, i.e., the missed detection and false alarm probabilities, cannot be guaranteed at a given signal to noise ratio (SNR) regardless the number of acquired samples. The BNS is adopted because it exhibits good tradeoff properties between complexity and performance. It is shown that BNS suffers from noise enhancement, which translates into a whitening effect in the correlation of the legacy signal. Contrarily to the existing literature, the signal detection problem is addressed without having to reconstruct neither the signal nor its spectrum. More specifically, the optimal low SNR detector is formulated as a generalized likelihood ratio test (GLRT) to exploit the available side information of the problem, i.e., the noise variance, the sampling density and the legacy signal autocorrelation. By deriving the asymptotic performance of the GLRT in the presence of noise uncertainty, explicit expressions for sampling walls are obtained as a function of the legacy signal occupancy, the SNR and the noise uncertainty. Further, numerical results are provided to assess the behavior of the sampling walls and signal detection performance.

  • 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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  • Sampling walls in signal detection of Bernoulli nonuniformly sampled signals

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    In this work, we show the existence of sampling walls in signal detection of nonuniformly sampling wideband signals in the presence of noise uncertainty. A sampling wall is the sampling rate below which the target error probabilities (namely the missed detection and false alarm probabilities) cannot be achieved at a given signal to noise ratio (SNR) regardless the number of acquired samples. Contrary to existing works, we address the signal detection as a binary hypotheses testing problem without having to reconstruct neither the signal nor the spectrum from the observations. Specifically, we adopt a Bernoulli distributed sampler as it exhibits good tradeoff properties between complexity and performance. We show that Bernoulli nonuniform sampling suffers from noise enhancement, which translates into a whitening effect in the correlation of the legacy signal. Therefore, in the presence of noise uncertainty, we derive explicit expressions for sampling walls as a function of the legacy signal occupation, the SNR and the noise uncertainty level. Finally, numerical results are further provided to assess the behavior of the sampling walls and signal detection performance.

    In this work, we show the existence of sampling walls in signal detection of nonuniformly sampling wideband signals in the presence of noise uncertainty. A sampling wall is the sampling rate below which the target error probabilities (namely the missed detection and false alarm probabilities) cannot be achieved at a given signal to noise ratio (SNR) regardless the number of acquired samples. Contrary to existing works, we address the signal detection as a binary hypotheses testing problem without having to reconstruct neither the signal nor the spectrum from the observations. Specifically, we adopt a Bernoulli distributed sampler as it exhibits good tradeoff properties between complexity and performance. We show that Bernoulli nonuniform sampling suffers from noise enhancement, which translates into a whitening effect in the correlation of the legacy signal. Therefore, in the presence of noise uncertainty, we derive explicit expressions for sampling walls as a function of the legacy signal occupation, the SNR and the noise uncertainty level. Finally, numerical results are further provided to assess the behavior of the sampling walls and signal detection performance.

  • 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.

  • Exploiting cognitive cyclostationary noise subspace for noncognitive spectrum sensing

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE International Workshop on Signal Processing Advances in Wireless Communications
    Presentation's date: 2013-06
    Presentation of work at congresses

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    This paper addresses the problem of spectrum sensing performed by a silent non intended cognitive receiver in the presence of an active cognitive transmitter. Because the silent receiver does not decode the information, the transmitted signal acts as strong interference to the spectrum sensing process. We propose a method that exploits the statistical features of cyclostationarity manifested in the cognitive signal. The silent cognitive user is able to identify a noise subspace where the noncognitive spectrum sensing is performed free of interference. We employ deflection as a theoretical performance indicator, while numerical results are employed as benchmarking and to corroborate the theoretical results.

  • 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
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  • Asymptotic error exponents in energy-detector and estimator-correlator signal detection

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE International Conference on Communications
    Presentation's date: 2012-06
    Presentation of work at congresses

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    The performance in signal detection is evaluated by the error (false-alarm and missed-detection) probabilities. However, calculating these probabilities is a difficult task in practice. This paper studies the asymptotic behavior of the energy-detector and the estimator-correlator by means of the Stein's lemma. The Stein's lemma is an information-theory result that provides the best achievable error exponent in the error probabilities when the number of observations goes to infinity. The derived closed-form expressions explain how detection performance is driven by the detector parameters and the second-order statistics of the problem. More specifically, it is shown that the error exponents depend on the signal-to-noise ratio (SNR) and the observation size. The prime focus is to establish a link between the required observation size for a fixed error probability as a function of the SNR. Numerical results show the tightness of the lemma.

  • 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

  • Multi-frequency GLRT spectrum sensing for wideband cognitive radio

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE International Conference on Communications
    Presentation's date: 2011-06
    Presentation of work at congresses

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    The problem of spectrum sensing in multi-frequency cognitive radio systems is addressed. We show that as the sensed bandwidth increases, the primary user detection is governed by a low signal-to-noise ratio (low-SNR) regime. By means of low-SNR approximations, we show that the optimal generalized likelihood ratio test (GLRT) only depends on the second order statistics of the observations and on a shaping kernel that highlights the relevant parameters required for detection. Furthermore, the ML estimates of the unknown model parameters are derived for multi-frequency systems, which allow closed-form expressions for the GLRT statistic. The detection performance and the kernel interpretation are supported with simulation results.

  • Compressed correlation-matching for spectrum sensing in sparse wideband regimes

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE International Conference on Communications
    Presentation's date: 2011-06
    Presentation of work at congresses

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    In this paper, we consider a novel compressed correlation-matching (CCM) approach for spectrum sensing of wideband sparse signals. We derive a general closed-form estimate of the wideband sparse signal level from compressed observations, while providing physical interpretation of the problem. The formulation allows straightforward application to signal processing problems of interest, such as generalized likelihood ratio test (GLRT) spectrum sensing for wideband cognitive radio. Simulation results are reported to assess the behavior of the CCM method.

  • Noise enhancement and SNR equivalence in Bernoulli nonuniform sampling

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    International Conference on Cognitive Radio and Advanced Spectrum Management
    Presentation's date: 2011-10
    Presentation of work at congresses

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    This paper addresses the problem of nonuniform spectral analysis and spectrum sensing by means of Bernoulli sampling. The statistical treatment of sampling shows that nonuniformly sampling below the Nyquist rate produces in average the e ects of noise enhancement and power loss on the second-order statistics of the signal (correlation and spectrum). The main focus of the paper is to obtain an equivalence in terms of signal-to-noise ratio (SNR) to model the noise enhancement and power loss effects. The Bernoulli nonuniform sampling is further extended to matrix formulation, which allows the application of spectrum sensing for cognitive radio signal detection. Numerical results assess the noise enhancement eff ect and SNR equivalence in spectral analysis and spectrum sensing.

  • Novel periodogram and Capon spectral analysis based on nonuniform sampling

     Font Segura, Josep; Vazquez Grau, Gregorio; Riba Sagarra, Jaume
    IEEE Global Communications Conference
    Presentation's date: 2011-12
    Presentation of work at congresses

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    The spectrum analysis problem based on the periodogram and Capon estimates from a nonuniformly sampled signal is addressed. The nonuniform sampling process is cast as a linear projection matrix which encompasses several recent sampling strategies such as compressive sampling. A rank-1 correlation-matching approach is proposed to derive a general filter-bank framework that allows the formulation of the nonuniform periodogram and Capon estimates as particular cases. The performance of the novel periodogram and Capon estimates is analyzed in a cognitive radio scenario where the primary system is a multiband signal with sparse spectrum. Both theoretical and numerical results show that the denoising process required by correlation-matching plays an important role in spectral analysis based on nonuniform sampling.

  • 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.

  • Linear Precoder Design Through Cut-Off Rate Maximization in MIMO-OFDM Coded Systems With Imperfect CSIT

     Rey Micolau, Francesc; Lamarca Orozco, M. Meritxell; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2010-03
    Journal article

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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). 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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  • 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). 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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  • Adaptive Interleaver Based on Rate-Compatible Punctured Convolutional Codes

     Rey Micolau, Francesc; Lamarca Orozco, M. Meritxell; Vazquez Grau, Gregorio
    IEEE transactions on communications
    Date of publication: 2009-06
    Journal article

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  • PROCESSAMENT DEL SENYAL EN COMUNICACIONS

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

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  • Detection of PPM-UWB Random Signals

     Lopez-Salcedo, Ja; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2008-05
    Journal article

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  • 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
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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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  • 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.

  • 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.

  • 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
    Participation in a competitive project

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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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  • COHERENT AND NON-COHERENT ULTRAWIDEBAND COMMUNICATIONS

     Lopez Salcedo, Jose Antonio
    Defense's date: 2007-03-28
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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  • Waveform-independent frame-timing acquisition for UWB signals

     Lopez Salcedo, Jose Antonio; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2007-01
    Journal article

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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.

  • NDA Waveform Estimation in the Low-SNR Regime

     López-Salcedo, José A (Uab); Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2007-12
    Journal article

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  • 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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  • D1.1. Análisis de Complejidad. WP2310. Fase de Estudio Preliminar. Análisis de Complejidad

     Lamarca Orozco, M. Meritxell; López-Salcedo, José A; Riba Sagarra, Jaume; Vazquez Grau, Gregorio
    Date: 2007-01
    Report

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  • Hybridization Algorithms Specification

     Riba Sagarra, Jaume; Vazquez Grau, Gregorio
    Date: 2007-01
    Report

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  • State-of-the-art techniques in mobile positioning using GNSS

     Enric, Calvo; Muntane Calvo, Enrique; Riba Sagarra, Jaume; Vazquez Grau, Gregorio
    Date: 2007-01
    Report

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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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  • Access to the full text
    Asymptotic equivalence between the unconditional maximum likelihood and the square-law nonlinearity symbol timing estimation  Open access

     Lopez Salcedo, Jose Antonio; Vazquez Grau, Gregorio
    IEEE transactions on signal processing
    Date of publication: 2006-01
    Journal article

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    This paper provides a systematic approach to the problem of nondata aided symbol-timing estimation for linear modulations. The study is performed under the unconditional maximum likelihood framework where the carrier-frequency error is included as a nuisance parameter in the mathematical derivation. The second-order moments of the received signal are found to be the sufficient statistics for the problem at hand and they allow the provision of a robust performance in the presence of a carrier-frequency error uncertainty. We particularly focus on the exploitation of the cyclostationary property of linear modulations. This enables us to derive simple and closed-form symbol-timing estimators which are found to be based on the well-known square timing recovery method by Oerder and Meyr. Finally, we generalize the OM method to the case of linear modulations with offset formats. In this case, the square-law nonlinearity is found to provide not only the symbol-timing but also the carrier-phase error.

  • IEEE MTT-S: international microwave symposium digest

     Vazquez Grau, Gregorio
    Collaboration in journals

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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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