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1 to 19 of 19 results
  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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

  • 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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  • 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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  • 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. 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. 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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  • GLRT-Based Spectrum Sensing for Cognitive Radio with Prior Information

     Font Segura, Josep; Wang, Xiaodong
    IEEE transactions on communications
    Date of publication: 2010-07
    Journal article

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  • PROCESSAMENT DEL SENYAL EN COMUNICACIONS

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