TY - JOUR T1 - Sidelobe Suppression for Multicarrier Signals via Structured Spectral Precoding JF - IEEE Transactions on Communications Y1 - 2024 A1 - Khawar Hussain A1 - R. López-Valcarce A1 - Francesc Rey A1 - Josep Sala A1 - Javier Villares KW - mayte KW - multicarrier communications KW - OFDM KW - spectrum shaping AB -
Reducing the large sidelobes of multicarrier signals
is crucial to prevent adjacent channel interference. Spectral
precoding is an effective approach toward this goal, at the
expense of throughput loss due to precoder redundancy; thus,
it is of interest to explore alternative precoder designs with
improved performance at lower redundancies. We present a
novel precoder which minimizes radiated power within a userselectable
frequency region. The structure of the precoding
matrix is chosen to allow efficient mitigation of in-band distortion
at the receiver by means of iterative and successive interference
cancellation, while completely avoiding distortion to protected
and pilot subcarriers. By exploiting the low-rank properties of
constituent blocks, computational complexity can be significantly
reduced with little impact on sidelobe reduction. Simulation
results show the benefits of the proposed design, which is
particularly effective in redundancy-limited settings targeting
high spectral efficiency.
ER - TY - CONF T1 - Energy-efficient analog beamforming with short packets in millimeter-wave MIMO systems T2 - 2020 54th Asilomar Conference on Signals, Systems, and Computers, California, 2020 Y1 - 2020 A1 - Jordi Borràs A1 - Francesc Molina A1 - R. López-Valcarce A1 - Josep Sala KW - mmWave KW - rodin AB -
The energy-aware design of fully analog precoders and combiners is investigated in this paper. To that aim, we consider a millimeter-wave short-packet communication scenario where power consumption and hardware complexity constitute relevant factors. User terminals employ a single channel encoder and, at hardware level, they implement analog architectures that combine phase shifters and switches. Additionally, transmitting terminals also leverage a power control system. An energy efficiency figure of merit is considered, and its optimization subject to finite packet-length constraints is tackled cyclically over disconnected feasible sets. Numerical results are reported
firstly, to illustrate the advantages of the proposed short-packet fully analog design, secondly, to compare its performance to that of on-off beamforming, and finally, to discuss the optimality of the proposed optimization algorithm.
JF - 2020 54th Asilomar Conference on Signals, Systems, and Computers, California, 2020 CY - Virtual event ER - TY - CONF T1 - Low-rank data matrix recovery with missing values and faulty sensors T2 - European Signal Processing Conference (EUSIPCO) Y1 - 2019 A1 - R. López-Valcarce A1 - Josep Sala KW - winter KW - wsn AB -

In practice, data gathered by wireless sensor networks often belongs in a low-dimensional subspace, but it can present missing as well as corrupted values due to sensor malfunctioning and/or malicious attacks. We study the problem of Maximum Likelihood estimation of the low-rank factors of the underlying structure in such situation, and develop an Expectation-Maximization algorithm to this purpose, together with an effective initialization scheme. The proposed method outperforms previous schemes based on an initial faulty sensor identification stage, and is competitive in terms of complexity and performance with convex optimization-based matrix completion approaches.

JF - European Signal Processing Conference (EUSIPCO) CY - A Coruña, Spain ER - TY - CONF T1 - Distributed multivariate regression with unknown noise covariance in the presence of outliers: a minimum description length approach T2 - IEEE Workshop on Statistical Signal Processing (SSP) Y1 - 2016 A1 - R. López-Valcarce A1 - Daniel Romero A1 - Josep Sala A1 - Alba Pagès-Zamora KW - compass KW - wsn AB -
We consider the problem of estimating the coefficients in a multivariable linear model by means of a wireless sensor network
which may be affected by anomalous measurements. The noise covariance matrices at the different sensors are assumed
unknown. Treating outlying samples, and their support, as additional nuisance parameters, the Maximum Likelihood
estimate is investigated, with the number of outliers being estimated according to the Minimum Description Length
principle. A distributed implementation based on iterative consensus techniques is then proposed, and it is shown effective
for managing outliers in the data.
JF - IEEE Workshop on Statistical Signal Processing (SSP) CY - Palma de Mallorca, Spain ER - TY - JOUR T1 - Multiantenna GLR detection of rank-one signals with known power spectral shape under spatially uncorrelated noise JF - IEEE Transactions on Signal Processing Y1 - 2016 A1 - Josep Sala A1 - Gonzalo Vázquez-Vilar A1 - R. López-Valcarce A1 - Saeid Sedighi A1 - Abbas Taherpour KW - cognitive radio KW - compass AB -

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.

VL - 64 IS - 23 ER - TY - JOUR T1 - Multiantenna GLR detection of rank-one signals with known power spectrum in white noise with unknown spatial correlation JF - IEEE Trans. on Signal Processing Y1 - 2012 A1 - Josep Sala A1 - Gonzalo Vázquez-Vilar A1 - R. López-Valcarce KW - cognitive radio KW - dynacs AB -
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.
VL - 60 IS - 6 ER - TY - JOUR T1 - Multiantenna Spectrum Sensing Exploiting Spectral a priori Information JF - IEEE Trans. on Wireless Communications Y1 - 2011 A1 - Gonzalo Vázquez-Vilar A1 - R. López-Valcarce A1 - Josep Sala KW - cognitive radio KW - dynacs KW - spectrum sensing VL - 10 IS - 12 ER - TY - CONF T1 - Multiantenna spectrum sensing for Cognitive Radio: overcoming noise uncertainty T2 - International Workshop on Cognitive Information Processing (CIP) Y1 - 2010 A1 - R. López-Valcarce A1 - Gonzalo Vázquez-Vilar A1 - Josep Sala JF - International Workshop on Cognitive Information Processing (CIP) CY - Elba Island, Italy ER -