@article {1066, title = {Sidelobe Suppression for Multicarrier Signals via Structured Spectral Precoding}, journal = {IEEE Transactions on Communications}, volume = {72}, year = {2024}, month = {06/2024}, pages = {3155-3168}, abstract = {
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.
}, keywords = {mayte, multicarrier communications, OFDM, spectrum shaping}, doi = {10.1109/TCOMM.2024.3357429}, author = {Khawar Hussain and R. L{\'o}pez-Valcarce and Francesc Rey and Josep Sala and Javier Villares} } @conference {990, title = {Energy-efficient analog beamforming with short packets in millimeter-wave MIMO systems}, booktitle = {2020 54th Asilomar Conference on Signals, Systems, and Computers, California, 2020}, year = {2020}, address = {Virtual event}, abstract = {
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.
}, keywords = {mmWave, rodin}, author = {Jordi Borr{\`a}s and Francesc Molina and R. L{\'o}pez-Valcarce and Josep Sala} } @conference {960, title = {Low-rank data matrix recovery with missing values and faulty sensors}, booktitle = {European Signal Processing Conference (EUSIPCO)}, year = {2019}, month = {09/2019}, address = {A Coru{\~n}a, Spain}, abstract = {

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.

}, keywords = {winter, wsn}, author = {R. L{\'o}pez-Valcarce and Josep Sala} } @conference {845, title = {Distributed multivariate regression with unknown noise covariance in the presence of outliers: a minimum description length approach}, booktitle = {IEEE Workshop on Statistical Signal Processing (SSP)}, year = {2016}, address = {Palma de Mallorca, Spain}, abstract = {
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.
}, keywords = {compass, wsn}, author = {R. L{\'o}pez-Valcarce and Daniel Romero and Josep Sala and Alba Pag{\`e}s-Zamora} } @article {866, title = {Multiantenna GLR detection of rank-one signals with known power spectral shape under spatially uncorrelated noise}, journal = {IEEE Transactions on Signal Processing}, volume = {64}, year = {2016}, month = {12/2016}, pages = {6269-6283}, chapter = {6269}, abstract = {

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.

}, keywords = {cognitive radio, compass}, issn = {1053-587X}, doi = {10.1109/TSP.2016.2601290}, author = {Josep Sala and Gonzalo V{\'a}zquez-Vilar and R. L{\'o}pez-Valcarce and Saeid Sedighi and Abbas Taherpour} } @article {648, title = {Multiantenna GLR detection of rank-one signals with known power spectrum in white noise with unknown spatial correlation}, journal = {IEEE Trans. on Signal Processing}, volume = {60}, year = {2012}, month = {06/2012}, pages = {3065 - 3078}, abstract = {
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.
}, keywords = {cognitive radio, dynacs}, doi = {10.1109/TSP.2012.2189767}, author = {Josep Sala and Gonzalo V{\'a}zquez-Vilar and R. L{\'o}pez-Valcarce} } @article {649, title = {Multiantenna Spectrum Sensing Exploiting Spectral a priori Information}, journal = {IEEE Trans. on Wireless Communications}, volume = {10}, year = {2011}, month = {12/2011}, pages = {4345 - 4355}, keywords = {cognitive radio, dynacs, spectrum sensing}, doi = {10.1109/TWC.2011.101211.110665}, author = {Gonzalo V{\'a}zquez-Vilar and R. L{\'o}pez-Valcarce and Josep Sala} } @conference {ValcarceVazquez10, title = {Multiantenna spectrum sensing for Cognitive Radio: overcoming noise uncertainty}, booktitle = {International Workshop on Cognitive Information Processing (CIP)}, year = {2010}, address = {Elba Island, Italy}, author = {R. L{\'o}pez-Valcarce and Gonzalo V{\'a}zquez-Vilar and Josep Sala} }