%0 Journal Article %J IEEE Transactions on Signal Processing %D 2016 %T Multiantenna GLR detection of rank-one signals with known power spectral shape under spatially uncorrelated noise %A Josep Sala %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A Saeid Sedighi %A Abbas Taherpour %K cognitive radio %K compass %X

We establish the generalized likelihood ratio (GLR) test for a Gaussian signal of known power spectral shape and unknown rank-one spatial signature in additive white Gaussian noise with an unknown diagonal spatial correlation matrix. This is motivated by spectrum sensing problems in dynamic spectrum access (DSA), in which the temporal correlation of the primary signal can be assumed known up to a scaling, and where the noise is due to an uncalibrated receive array. For spatially independent identically distributed (i.i.d.) noise, the corresponding GLR test reduces to a scalar optimization problem, whereas the GLR detector in the general non-i.i.d. case yields a more involved expression, which can be computed via alternating optimization methods. Low signal-to-noise ratio (SNR) approximations to the detectors are given, together with an asymptotic analysis showing the influence on detection performance of the signal power spectrum and SNR distribution across antennas. Under spatial rank-P conditions, we show that the rank-one GLR detectors are consistent with a statistical criterion that maximizes the output energy of a beamformer operating on filtered data. Simulation results support our theoretical findings in that exploiting prior knowledge on the signal power spectrum can result in significant performance improvement.

%B IEEE Transactions on Signal Processing %V 64 %P 6269-6283 %8 12/2016 %G eng %N 23 %& 6269 %R 10.1109/TSP.2016.2601290 %0 Conference Paper %B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %D 2012 %T Design of universal multicoset sampling patterns for compressed sensing of multiband sparse signals %A M. Elena Domínguez-Jiménez %A Nuria González-Prelcic %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %X

Many problems in digital communications involve wideband radio signals. As the most recent example, the impressive advances in Cognitive Radio systems make even more necessary the development of sampling schemes for wideband radio signals with spectral holes. This is equivalent to considering a sparse multiband signal in the framework of Compressive Sampling theory. Starting from previous results on multicoset sampling and recent advances in compressive sampling, we analyze the matrix involved in the corresponding reconstruction equation and define a new method for the design of universal multicoset codes, that is, codes guaranteeing perfect reconstruction of the sparse multiband signal.

%B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %C Kyoto (Japan) %P 3337 - 3340 %8 03/2012 %@ 978-1-4673-0044-5 %G eng %R 10.1109/ICASSP.2012.6288630 %0 Journal Article %J IEEE Trans. on Signal Processing %D 2012 %T Multiantenna GLR detection of rank-one signals with known power spectrum in white noise with unknown spatial correlation %A Josep Sala %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %K cognitive radio %K dynacs %X
Multiple-antenna detection of a Gaussian signal with spatial rank one in temporally white Gaussian noise with arbitrary and  unknown spatial covariance is considered. This is motivated by spectrum sensing problems in the context of Dynamic Spectrum Access in which several secondary networks coexist but do not cooperate, creating a background of spatially correlated broadband interference. When the temporal correlation of the signal of interest is assumed known up to a scale factor, the corresponding Generalized Likelihood Ratio Test is shown to yield a scalar optimization problem. Closed-form expressions of the test are obtained for the general signal spectrum case in the low signal-to-noise ratio (SNR) regime, as well as for signals with binary-valued power spectrum in arbitrary SNR. The two resulting detectors turn out to be equivalent. An asymptotic approximation to the test distribution for the low-SNR regime is derived, closely matching empirical results from spectrum sensing simulation experiments.
%B IEEE Trans. on Signal Processing %V 60 %P 3065 - 3078 %8 06/2012 %G eng %N 6 %R 10.1109/TSP.2012.2189767 %0 Conference Paper %B IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP 2011) %D 2011 %T Detection diversity of multiantenna spectrum sensors %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A Ashish Pandharipande %K cognitive radio %K detection diversity %K spectrum sensing %X
In the context of spectrum sensing, we investigate the performance of detectors equipped with M antennas (co-located or distributed) under Rayleigh fading, in terms of detection diversity. Rather than the high-SNR concept of diversity order common in the communications literature, we adopt the notion recently advocated by Daher and Adve in the radar community: the slope of the average probability of detection (\bar{P}_D) vs. SNR curve at \bar{P}_D = 0.5. This definition is well suited to spectrum sensing, which invariably deals with low SNR levels. It is shown that the diversity order grows as M for an optimal centralized detector having access to all observations, whereas for the two distributed schemes considered (the multiantenna energy detector and the OR detector) it grows no faster than √M.
%B IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP 2011) %I IEEE %C Prague, Czech Republic %P 2936-2939 %8 05/2011 %G eng %0 Journal Article %J IEEE Trans. on Signal Processing %D 2011 %T Detection of Rank-P Signals in Cognitive Radio Networks With Uncalibrated Multiple Antennas %A David Ramírez %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A Javier Vía %A Ignacio Santamaría %K cognitive radio %K dynacs %K spectrum sensing %X
Spectrum sensing is a key component of the Cognitive Radio paradigm. Typically, primary signals have to be detected with uncalibrated receivers at signal-to-noise ratios (SNRs) well below decodability levels. Multiantenna detectors exploit spatial independence of receiver thermal noise to boost detection performance and robustness. We study the problem
of detecting a Gaussian signal with rank-P unknown spatial
covariance matrix in spatially uncorrelated Gaussian noise with
unknown covariance using multiple antennas. The generalized
likelihood ratio test (GLRT) is derived for two scenarios. In the
first one, the noises at all antennas are assumed to have the same (unknown) variance, whereas in the second, a generic diagonal noise covariance matrix is allowed in order to accommodate calibration uncertainties in the different antenna frontends. In the latter case, the GLRT statistic must be obtained numerically, for which an efficient method is presented. Furthermore, for asymptotically low SNR, it is shown that the GLRT does admit a closed form, and the resulting detector performs well in practice. Extensions are presented in order to account for unknown temporal correlation in both signal and noise, as well as frequency-selective channels.
%B IEEE Trans. on Signal Processing %V 59 %P 3764-3774 %8 08/2012 %G eng %N 8 %R 10.1109/TSP.2011.2146779 %0 Thesis %D 2011 %T Interference and Network Management in Cognitive Communication Systems %A Gonzalo Vázquez-Vilar %K cognitive radio %K spectrum sensing %I University of Vigo %C Vigo, Spain %V Ph.D. %8 06/2011 %G eng %9 Ph.D. thesis %0 Conference Paper %B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %D 2011 %T Multiantenna detection under noise uncertainty and primary user's spatial structure %A David Ramírez %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A Javier Vía %A Ignacio Santamaría %K cognitive radio %K generalized likelihood ratio test (GLRT) %K spectrum sensing %B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %I IEEE %C Prage, Czech Republic %P 2948-2951 %8 May %G eng %0 Journal Article %J IEEE Trans. on Wireless Communications %D 2011 %T Multiantenna Spectrum Sensing Exploiting Spectral a priori Information %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A Josep Sala %K cognitive radio %K dynacs %K spectrum sensing %B IEEE Trans. on Wireless Communications %V 10 %P 4345 - 4355 %8 12/2011 %G eng %N 12 %R 10.1109/TWC.2011.101211.110665 %0 Journal Article %J IEEE Trans. on Signal Processing %D 2011 %T Spectrum Sensing Exploiting Guard Bands and Weak Channels %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %K cognitive radio %K dynacs %K spectrum sensing %X
We address the problem of primary user detection in Cognitive Radio from a wideband signal comprising multiple primary channels, exploiting a priori knowledge about the primary network: channelization and spectral shape of primary transmissions. Using this second-order statistical information, a multichannel Gaussian model is formulated. In order to obtain a Generalized Likelihood Ratio Test, we first address Maximum Likelihood (ML) estimation of the power levels at the different channels, as well as of the noise variance. The ML conditions suggest a suboptimal closed-form estimate, which takes the form of a constrained Least Squares estimator whose asymptotic efficiency is shown for flat bandpass spectra in white noise, a case of practical importance. The resulting detectors exploit those frequency bins corresponding to guard bands and to primary channels perceived as weak to improve noise variance estimation. Analytical expressions for the probabilities of detection and false alarm are presented. Performance is evaluated via simulations in the setting of a terrestrial TV primary network with realistic channelization parameters.
%B IEEE Trans. on Signal Processing %V 59 %P 6045-6057 %8 12/2011 %G eng %N 12 %R 10.1109/TSP.2011.2167615 %0 Journal Article %J IEEE Transactions on Vehicular Technology %D 2010 %T Dynamic spectrum leasing (DSL): A new paradigm for spectrum sharing in cognitive radio networks %A Sudhaman K. Jayaweera %A Gonzalo Vázquez-Vilar %A C. Mosquera %K cognitive radio %K DSL %K dynamic spectrum access %K dynamic spectrum leasing %K dynamic spectrum sharing %K game theory %K power control %B IEEE Transactions on Vehicular Technology %V 59 %P 2328-2339 %G eng %0 Conference Paper %B ICC Workshop on Cognitive Radio Interfaces and Signal Processing (ICC CRISP) %D 2010 %T Dynamic Spectrum Leasing (DSL) in Dynamic Channels %A Georges El-Howayek %A Sudhaman K. Jayaweera %A Kamrul Hakim %A Gonzalo Vázquez-Vilar %A C. Mosquera %K cognitive radio %K DSL %K dynamic spectrum leasing %K game theory %K Rayleigh fading %K time-varying channels %K time-varying secondary system %B ICC Workshop on Cognitive Radio Interfaces and Signal Processing (ICC CRISP) %C Cape Town, South Africa %8 May 23 %G eng %0 Conference Paper %B International Workshop on Cognitive Information Processing (CIP) %D 2010 %T Multiantenna spectrum sensing for Cognitive Radio: overcoming noise uncertainty %A R. López-Valcarce %A Gonzalo Vázquez-Vilar %A Josep Sala %B International Workshop on Cognitive Information Processing (CIP) %C Elba Island, Italy %G eng %0 Journal Article %J IEEE Transactions on Wireless Communications %D 2010 %T Primary User Enters the Game: Performance of Dynamic Spectrum Leasing in Cognitive Radio Networks %A Gonzalo Vázquez-Vilar %A C. Mosquera %A Sudhaman K. Jayaweera %B IEEE Transactions on Wireless Communications %G eng %0 Conference Paper %B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %D 2010 %T Wideband Spectral Estimation from Compressed Measurements Exploiting Spectral a priori Information in Cognitive Radio Systems %A Gonzalo Vázquez-Vilar %A R. López-Valcarce %A C. Mosquera %A Nuria González-Prelcic %K cognitive radio %K compressive sampling %K Spectral estimation %B IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) %C Dallas, U.S.A. %8 March 14-19 %G eng %0 Conference Paper %B International Conference on Cognitive Radio Oriented Wireless Networks and Communications (Crowncom) %D 2009 %T Multiantenna detection of multicarrier primary signals exploiting spectral a priori information %A R. López-Valcarce %A Gonzalo Vázquez-Vilar %A Marcos Álvarez-Díaz %B International Conference on Cognitive Radio Oriented Wireless Networks and Communications (Crowncom) %C Hannover, Germany %8 June 22-24 %G eng %0 Conference Paper %B IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC) %D 2009 %T Wideband Spectrum Sensing in Cognitive Radio: Joint Estimation of Noise Variance and Multiple Signal Levels %A R. López-Valcarce %A Gonzalo Vázquez-Vilar %B IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC) %C Perugia, Italy %8 June 21-24 %G eng