@article {947, title = {MMSE filter design for Full-Duplex filter-and-forward MIMO relays under limited dynamic range}, journal = {Signal Processing}, volume = {156}, year = {2019}, month = {03/2019}, pages = {208-219}, abstract = {
We study the problem of optimizing the end-to-end performance of a full-duplex filter-and-forward MIMO relay link, consisting
of a source, a relay, and a destination node, by employing linear filtering at each node. The system model accounts for multipath
propagation and self-interference at the relay, as well as transmitter impairments and limited dynamic range at every node. The
design accommodates signals with arbitrary spectra and includes the direct link between the source and destination nodes. Under
the minimum mean square error criterion, the resulting non-convex problem is approximated by a sequence of convex problems
and solved by means of an alternating minimization method. Linear constraints allocate some of the degrees of freedom in the relay
to guarantee a sufficiently small residual self-interference. Simulations quantify the impact of degrees of freedom, the dynamic
range, and the balance between direct and relay paths on the link performance.
}, keywords = {adaptive signal processing, full-duplex, winter}, doi = {doi.org/10.1016/j.sigpro.2018.11.001}, author = {Emilio Antonio-Rodr{\'\i}guez and Stefan Werner and R. L{\'o}pez-Valcarce and Risto Wichman} } @proceedings {968, title = {Solving self-interference issues in a Full-Duplex radio transceiver}, journal = {2nd XoveTIC Conference}, year = {2019}, month = {09/2019}, address = {A Coru{\~n}a (Spain)}, abstract = {
Most wireless devices transmit and receive at different spectrum frequency bands. This
approach is no longer optimal due to increasing electromagnetic exhaustion. Besides, interference
among all present and future working services should be negligible. A full-duplex scheme using
the same band for simultaneous uplink and downlink is a huge step towards solving this issue.
However, sharing the same frequency band involves a large interference of transmitted signal over
received signal. To fix this problem, we propose the usage of a hybrid multistage cancellation system,
consisting of an analog cancellation setup at RF frequencies and a baseband digital cancellation stage.
}, keywords = {adaptive signal processing, full-duplex, winter}, doi = {10.3390/proceedings2019021035}, author = {Miguel Franco-Martinez and Francisco-Javier Martinez-Alonso and R. L{\'o}pez-Valcarce} } @article {880, title = {FER Estimation in a Memoryless BSC with Variable Frame Length and Unreliable ACK/NAK Feedback}, journal = {IEEE Transactions on Wireless Communications}, volume = {16}, year = {2017}, month = {06/2017}, pages = {3661 - 3673}, abstract = {
We consider the problem of estimating the frame error rate (FER) of a given memoryless binary symmetric channel by observing the success or failure of transmitted packets. Whereas FER estimation is relatively straightforward if all observations correspond to packets with equal length, the problem becomes considerably more complex when this is not the case. We develop FER estimators when
transmissions of different lengths are observed, together with the Cramer-Rao Lower Bound (CRLB). Although the main focus is on Maximum Likelihood (ML) estimation, we also obtain low complexity schemes performing close to optimal in some scenarios. In a second stage, we consider the case in which FER estimation is performed at a node different from the receiver, and incorporate the impairment of unreliable observations by considering noisy ACK/NAK feedback links. The impact of unreliable feedback is analyzed by means of the corresponding CRLB. In this setting, the ML estimator is obtained by applying the Expectation-Maximization algorithm to jointly estimate the error probabilities of the data and feedback links. Simulation results illustrate the benefits of the proposed estimators.
}, keywords = {adaptive signal processing, compass, Cram{\'e}r-Rao bound (CRB), frame error rate, myrada, winter}, doi = {10.1109/TWC.2017.2686845}, author = {Alberto Rico-Alvari{\~n}o and R. L{\'o}pez-Valcarce and Carlos Mosquera and Robert W. Heath Jr.} } @article {838, title = {Wideband full-duplex MIMO relays with blind adaptive self-interference cancellation}, journal = {Signal Processing}, volume = {130}, year = {2017}, month = {01/2017}, pages = {74-85}, chapter = {74}, abstract = {
We develop adaptive self-interference cancellation algorithms for both filter-and-forward and decode-and-forward
multiple-input multiple-output relays. The algorithms are blind in the sense that they only exploit the spectral properties
of the transmitted signal to identify the self-interference channel, while dealing with frequency-selective channels and
arbitrary signal spectra. Our approach is non-intrusive in the sense that the algorithms can successfully identify, track,
and cancel the self-interference distortion while the relay is operating in its normal mode. We study the stationary
points of the algorithms and analyze under which conditions they achieve perfect cancellation of the self-interference.
Simulation results show that the algorithms provide residual self-interference levels below the noise floor by using
the time samples of only a few OFDM symbols.
}, keywords = {adaptive signal processing, compass, full duplex, winter}, issn = {0165-1684}, doi = {10.1016/j.sigpro.2016.06.010}, author = {Emilio Antonio-Rodr{\'\i}guez and Stefan Werner and R. L{\'o}pez-Valcarce and Taneli Riihonen and Risto Wichman} } @conference {839, title = {Wideband self-interference cancellation for better spectrum use}, booktitle = {IEEE WoWMoM 2016 Workshop on Fifth Generation Wireless}, year = {2016}, month = {06/2016}, keywords = {adaptive signal processing, compass, full duplex}, author = {Carlos Mosquera} } @article {769, title = {Cram{\'e}r-Rao Bounds for SNR Estimation of Oversampled Linearly Modulated Signals}, journal = {IEEE Trans. Signal Processing}, volume = {63}, year = {2015}, month = {04/2015}, pages = {1675-1683}, chapter = {1675}, abstract = {
Most Signal-to-noise ratio (SNR) estimators use the
receiver matched filter output sampled at the symbol rate, an
approach which does not preserve all information in the analog
waveform due to aliasing. Thus, it is relevant to ask whether
avoiding aliasing could improve SNR estimation. To this end, we
compute the corresponding data-aided (DA) and non-data-aided
(NDA) Cram{\'e}r-Rao bounds (CRBs). We adopt a novel dual filter
framework, which is shown to be information-preserving under
suitable conditions and considerably simplifies the analysis. It is
shown that the CRB can be substantially reduced by exploiting
any available excess bandwidth, depending on the modulation
scheme, the SNR range, and the estimator (DA or NDA) type.
}, keywords = {adaptive signal processing, compass, Cram{\'e}r-Rao bound (CRB), dynacs, oversampling, Signal-to-noise ratio (SNR)}, doi = {10.1109/TSP.2015.2396013}, author = {R. L{\'o}pez-Valcarce and J. Villares and J. Riba and W. Gappmair and C. Mosquera} } @conference {808, title = {Subspace-constrained SINR optimization in MIMO full-duplex relays under limited dynamic range}, booktitle = {IEEE 16th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)}, year = {2015}, month = {06/2015}, publisher = {IEEE}, organization = {IEEE}, address = {Stockholm, Sweden}, abstract = {
We propose a method for maximizing the signal-to-interference-plus-noise ratio (SINR) in a wideband full-duplex MIMO regenerative relay that accounts limited dynamic range of the receiver and transmitter impairments. Transmit and receive filters are designed at the relay, by means of an alternating minimization algorithm, to minimize the interference at the decoder input in the destination node. We impose channel shortening and subspace constraints to ensure that the received signal at the destination is not compromised. Simulation results show that the presented method significantly outperforms other constrained approaches.
}, keywords = {adaptive signal processing, compass, full duplex}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce and Taneli Riihonen and Stefan Werner and Risto Wichman} } @conference {771, title = {Channel estimation in millimeter wave MIMO systems with one-bit quantization}, booktitle = {Asilomar Conf. on Signals, Systems and Computers}, year = {2014}, keywords = {adaptive signal processing, compass, mmWave}, doi = {10.1109/ACSSC.2014.7094595}, author = {Jianhua Mo and Phil Schniter and Nuria Gonz{\'a}lez-Prelcic and Robert W. Heath Jr.} } @conference {726, title = {FER prediction with variable codeword length}, booktitle = {ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM)}, year = {2014}, address = {Florence, Italy}, abstract = {

Frame error rate (FER) prediction in wireless communication systems is an important tool with applications to system level simulations and link adaptation, among others. Although in realistic communication scenarios it is expected to have codewords of different lengths, previous work on FER prediction marginally treated the dependency of the FER on the codeword length. In this paper, we present a method to estimate the FER using codewords of different length. We derive a low complexity FER estimator for frames of different length transmitted over a binary symmetric channel of unknown error probability. We extend this technique to coded systems by the use of effective SNR FER predictors. The proposed estimation scheme is shown to outperform other simpler estimation methods.

}, keywords = {adaptive signal processing, compass, dynacs, Effective SNR, FER prediction, PHY abstraction}, doi = {10.1109/ICASSP.2014.6853935}, author = {Alberto Rico-Alvari{\~n}o and Robert W. Heath Jr. and Carlos Mosquera} } @article {739, title = {Learning-Based Adaptive Transmission for Limited Feedback Multiuser MIMO-OFDM}, journal = {IEEE Transactions on Wireless Communications}, year = {2014}, keywords = {adaptive signal processing, dynacs}, doi = {10.1109/TWC.2014.2314104}, author = {Alberto Rico-Alvari{\~n}o and Robert W. Heath Jr.} } @article {766, title = {MIMO precoding and combining solutions for millimeter wave systems}, journal = {IEEE Communications Magazine}, volume = {52}, year = {2014}, month = {12/2014}, pages = {122-131}, abstract = {

Millimeter-wave communication is one way to alleviate the spectrum gridlock at lower frequencies while simultaneously providing high-bandwidth communication channels. MmWave makes use of MIMO through large antenna arrays at both the base station and the mobile station to provide sufficient received signal power. This article explains how beamforming and precoding are different in MIMO mmWave systems than in their lower-frequency counterparts, due to different hardware constraints and channel characteristics. Two potential architectures are reviewed: hybrid analog/digital precoding/combining and combining with low-resolution analog- to-digital converters. The potential gains and design challenges for these strategies are discussed, and future research directions are highlighted.

}, keywords = {adaptive signal processing, compass, mmWave}, doi = {10.1109/MCOM.2014.6979963}, author = {Ahmed Alkhateeb and Jianhua Mo and Nuria Gonz{\'a}lez-Prelcic and Robert W. Heath Jr.} } @conference {732, title = {SINR Optimization in Wideband Full-Duplex MIMO Relays under Limited Dynamic Range}, booktitle = {IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM)}, year = {2014}, address = {A Coru{\~n}a, Spain}, keywords = {adaptive signal processing, compass, full duplex}, doi = {10.1109/SAM.2014.6882369}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce and Taneli Riihonen and Stefan Werner and Risto Wichman} } @conference {693, title = {Adaptive Self-interference Cancellation in Wideband Full-Duplex Decode-and-Forward MIMO Relays}, booktitle = {IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)}, year = {2013}, month = {06/2013}, address = {Darmstadt, Germany}, keywords = {adaptive signal processing, dynacs, full duplex}, doi = {10.1109/SPAWC.2013.6612074}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce and Taneli Riihonen and Stefan Werner and Risto Wichman} } @conference {687, title = {Autocorrelation-based adaptation rule for feedback equalization in Wideband Full-Duplex Amplify-and-Forward MIMO relays}, booktitle = {Int. Conf. Acoust., Speech, Signal Process. (ICASSP)}, year = {2013}, abstract = {
Simultaneous reception and transmission in the same frequency, so-called full-duplex operation, causes an infinite feedback loop in an amplify-and-forward relay. The unwanted echoes may result in oscillation at the relay, making it unstable, and distorting the spectrum. This paper presents an adaptive MIMO filtering method for full-duplex amplify-and-forward relays that aims at solving the joint problem of self-interference mitigation and equalization of the source-relay channel. The scheme exploits knowledge of the autocorrelation of the transmitted signal as the only side information while allowing the relay, in the best case, to implement precoding as if there was not any self-interference or frequency selectivity in the source-relay channel. Finally, the proposed adaptation algorithm is investigated by determining its stationary points and by performing simulations in a MIMO-OFDM framework.
}, keywords = {adaptive signal processing, dynacs, full duplex}, doi = {10.1109/ICASSP.2013.6638606}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce and Taneli Riihonen and Stefan Werner and Risto Wichman} } @conference {686, title = {Cancelling self-interference in full-duplex relays without Angle-of-Arrival information}, booktitle = {Int. Conf. Acoust., Speech, Signal Process. (ICASSP)}, year = {2013}, abstract = {
With full-duplex relays, simultaneous reception and transmission in
the same frequency produce self-interference distortion and relay oscillation,
hampering reception at the receiver end unless properly
mitigated. Previous adaptive methods for self-interference cancellation
using multiple receive antennas require knowledge of the direction
of arrival of the source signal. We present a novel architecture
and adaptive scheme for Amplify-and-Forward relays allowing cancellation
without such knowledge. The temporal filter is updated
under the property restoral paradigm in order to match the power
spectrum of the retransmitted signal to that of the source signal.
}, keywords = {adaptive signal processing, dynacs, full duplex}, doi = {10.1109/ICASSP.2013.6638558}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce} } @article {651, title = {An Adaptive Feedback Canceller for Full-Duplex Relays Based on Spectrum Shaping}, journal = {IEEE J. Selected Areas in Communications}, volume = {30}, year = {2012}, month = {08/2012}, pages = {1566 - 1577}, abstract = {
Although full-duplex relaying schemes are appealing\ in order to improve spectral efficiency, simultaneous reception\ and transmission in the same frequency results in selfinterference,
distorting the retransmitted signal and making\ the relay prone to oscillation. Current feedback cancellation\ techniques by means of adaptive filters are hampered by the fact\ that the useful and interference signals are highly correlated. We\ present a new adaptive algorithm which effectively and blindly
restores the spectral shape of the desired signal. In contrast
with previous schemes, the novel adaptive feedback canceller has\ low complexity, does not introduce additional delay in the relay\ station, and partly compensates for multipath propagation.
}, keywords = {adaptive signal processing, dynacs, full duplex}, doi = {10.1109/JSAC.2012.120923}, author = {R. L{\'o}pez-Valcarce and Emilio Antonio-Rodr{\'\i}guez and C. Mosquera and Fernando P{\'e}rez-Gonz{\'a}lez} } @conference {652, title = {Adaptive self-interference suppression for full-duplex relays with multiple receive antennas}, booktitle = {IEEE 13th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012)}, year = {2012}, month = {07/2012}, publisher = {IEEE}, organization = {IEEE}, address = {{\c C}esme, Turkey}, abstract = {
In full-duplex relays, simultaneous reception and transmission
in the same frequency results in self-interference which\ distorts the retransmitted signal and makes the relay prone\ to oscillation. We present an adaptive feedback canceller for\ multiple-input single-output (MISO) relays, efficiently combining\ spatial and temporal processing. The receive array is\ adaptively steered towards the minimum variance distortionless\ response (MVDR), whereas the temporal filter update is\ based on a novel low-complexity spectrum shaping scheme\ which avoids introducing additional delay in the relay station.
}, keywords = {adaptive signal processing, dynacs, full duplex}, doi = {10.1109/SPAWC.2012.6292948}, author = {Emilio Antonio-Rodr{\'\i}guez and R. L{\'o}pez-Valcarce} } @conference {639, title = {Optimum Training for CSI Acquisition in Cognitive Radio Channels}, booktitle = {Asilomar Conference on Signals, Systems, and Computers}, year = {2012}, address = {Pacific Grove, CA}, keywords = {adaptive signal processing, cognitive radio, dynacs}, doi = {10.1109/ACSSC.2012.6488973}, author = {Alberto Rico-Alvari{\~n}o and C. Mosquera} } @article {troncosoTIFS2011, title = {Secure Adaptive Filtering}, journal = {IEEE Transactions on Information Forensics and Security}, volume = {6}, number = {2}, year = {2011}, month = {June}, pages = {469 -485}, keywords = {adaptive signal processing, computational complexity, cryptography, digital data protection, encrypted domain, homomorphic encryption systems, least mean squares algorithm, least mean squares methods, privacy, secure adaptive filtering, security, signal privacy preservation, SPED techniques, watermarking}, doi = {10.1109/TIFS.2011.2109385}, author = {Juan Ram{\'o}n Troncoso-Pastoriza and Fernando P{\'e}rez-Gonz{\'a}lez} } @mastersthesis {799, title = {Design of Nonlinear Precoding and Estimation Schemes for Advanced Communication Systems}, volume = {Ph.D.}, year = {2010}, month = {04/2010}, type = {Ph.D. thesis}, keywords = {adaptive signal processing, satcom}, author = {Marcos {\'A}lvarez-D{\'\i}az} } @conference {uvigo:firstorder, title = {Analysis of a first-order adaptive recursive predictor}, booktitle = {IEEE Conference on Decision and Control / European Control Conference (CDC/ECC)}, year = {2005}, address = {Seville, Spain}, keywords = {adaptive signal processing, equalization, second-order statistics}, doi = {10.1109/CDC.2005.1582919}, author = {R. L{\'o}pez-Valcarce} } @conference {uvigo:diamond, title = {Diamond contour-based phase recovery for (cross-)QAM constellations}, booktitle = {IEEE Workshop on Statistical Signal Processing (SSP)}, year = {2005}, address = {Bordeaux, France}, keywords = {adaptive signal processing, synchronization}, doi = {10.1109/SSP.2005.1628678}, author = {Marcos {\'A}lvarez-D{\'\i}az and R. L{\'o}pez-Valcarce} } @article {uvigo:shorteners, title = {Realizable minimum mean-squared error channel shorteners}, journal = {IEEE Transactions on Signal Processing}, volume = {53}, number = {11}, year = {2005}, month = {November}, pages = {4354{\textendash}4362}, keywords = {adaptive signal processing, Channel shortening}, doi = {10.1109/TSP.2005.857050}, author = {R. L{\'o}pez-Valcarce} } @article {uvigo:realizable, title = {Realizable linear and decision feedback equalizers: properties and connections}, journal = {IEEE Transactions on Signal Processing}, volume = {52}, number = {3}, year = {2004}, note = {Recipient of a 2005 Best Paper Award of the IEEE Signal Processing Society}, month = {March}, pages = {757{\textendash}773}, keywords = {adaptive signal processing, channel equalization}, doi = {10.1109/TSP.2003.822360}, author = {R. L{\'o}pez-Valcarce} } @mastersthesis {801, title = {Adaptive algorithms for identification and equalization using recursive filters}, volume = {Ph.D.}, year = {2001}, month = {11/2001}, school = {University of Vigo}, type = {Ph.D. thesis}, address = {Vigo, Spain}, keywords = {adaptive signal processing}, author = {R. L{\'o}pez-Valcarce} } @mastersthesis {802, title = {Blind equalization of linear and nonlinear digital communication channels from second-order statistics}, volume = {Ph.D.}, year = {2000}, month = {12/2000}, school = {University of Iowa}, type = {Ph.D. thesis}, address = {Iowa City, USA}, keywords = {adaptive signal processing, channel equalization}, author = {R. L{\'o}pez-Valcarce} }