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.

%B IEEE Transactions on Wireless Communications
%V 16
%P 3661 - 3673
%8 06/2017
%G eng
%N 6
%R 10.1109/TWC.2017.2686845
%0 Journal Article
%J Signal Processing
%D 2017
%T Wideband full-duplex MIMO relays with blind adaptive self-interference cancellation
%A Emilio Antonio-Rodríguez
%A Stefan Werner
%A R. López-Valcarce
%A Taneli Riihonen
%A Risto Wichman
%K adaptive signal processing
%K compass
%K full duplex
%K winter
%X 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.

%B Signal Processing
%V 130
%P 74-85
%8 01/2017
%G eng
%& 74
%R 10.1016/j.sigpro.2016.06.010
%0 Conference Paper
%B IEEE WoWMoM 2016 Workshop on Fifth Generation Wireless
%D 2016
%T Wideband self-interference cancellation for better spectrum use
%A Carlos Mosquera
%K adaptive signal processing
%K compass
%K full duplex
%B IEEE WoWMoM 2016 Workshop on Fifth Generation Wireless
%8 06/2016
%G eng
%0 Journal Article
%J IEEE Trans. Signal Processing
%D 2015
%T Cramér-Rao Bounds for SNR Estimation of Oversampled Linearly Modulated Signals
%A R. López-Valcarce
%A J. Villares
%A J. Riba
%A W. Gappmair
%A C. Mosquera
%K adaptive signal processing
%K compass
%K Cramér-Rao bound (CRB)
%K dynacs
%K oversampling
%K Signal-to-noise ratio (SNR)
%X 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) Cramér-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.

%B IEEE Trans. Signal Processing
%V 63
%P 1675-1683
%8 04/2015
%G eng
%N 7
%& 1675
%R 10.1109/TSP.2015.2396013
%0 Conference Paper
%B IEEE 16th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
%D 2015
%T Subspace-constrained SINR optimization in MIMO full-duplex relays under limited dynamic range
%A Emilio Antonio-Rodríguez
%A R. López-Valcarce
%A Taneli Riihonen
%A Stefan Werner
%A Risto Wichman
%K adaptive signal processing
%K compass
%K full duplex
%X 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.

%B IEEE 16th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
%I IEEE
%C Stockholm, Sweden
%8 06/2015
%G eng
%0 Conference Paper
%B Asilomar Conf. on Signals, Systems and Computers
%D 2014
%T Channel estimation in millimeter wave MIMO systems with one-bit quantization
%A Jianhua Mo
%A Phil Schniter
%A Nuria González-Prelcic
%A Robert W. Heath Jr.
%K adaptive signal processing
%K compass
%K mmWave
%B Asilomar Conf. on Signals, Systems and Computers
%G eng
%R 10.1109/ACSSC.2014.7094595
%0 Conference Paper
%B ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM)
%D 2014
%T FER prediction with variable codeword length
%A Alberto Rico-Alvariño
%A Robert W. Heath Jr.
%A Carlos Mosquera
%K adaptive signal processing
%K compass
%K dynacs
%K Effective SNR
%K FER prediction
%K PHY abstraction
%X 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.

%B ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM) %C Florence, Italy %G eng %R 10.1109/ICASSP.2014.6853935 %0 Journal Article %J IEEE Transactions on Wireless Communications %D 2014 %T Learning-Based Adaptive Transmission for Limited Feedback Multiuser MIMO-OFDM %A Alberto Rico-Alvariño %A Robert W. Heath Jr. %K adaptive signal processing %K dynacs %B IEEE Transactions on Wireless Communications %G eng %R 10.1109/TWC.2014.2314104 %0 Journal Article %J IEEE Communications Magazine %D 2014 %T MIMO precoding and combining solutions for millimeter wave systems %A Ahmed Alkhateeb %A Jianhua Mo %A Nuria González-Prelcic %A Robert W. Heath Jr. %K adaptive signal processing %K compass %K mmWave %XMillimeter-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.

%B IEEE Communications Magazine %V 52 %P 122-131 %8 12/2014 %G eng %N 12 %R 10.1109/MCOM.2014.6979963 %0 Conference Paper %B IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) %D 2014 %T SINR Optimization in Wideband Full-Duplex MIMO Relays under Limited Dynamic Range %A Emilio Antonio-Rodríguez %A R. López-Valcarce %A Taneli Riihonen %A Stefan Werner %A Risto Wichman %K adaptive signal processing %K compass %K full duplex %B IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) %C A Coruña, Spain %G eng %R 10.1109/SAM.2014.6882369 %0 Conference Paper %B IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC) %D 2013 %T Adaptive Self-interference Cancellation in Wideband Full-Duplex Decode-and-Forward MIMO Relays %A Emilio Antonio-Rodríguez %A R. López-Valcarce %A Taneli Riihonen %A Stefan Werner %A Risto Wichman %K adaptive signal processing %K dynacs %K full duplex %B IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC) %C Darmstadt, Germany %8 06/2013 %G eng %R 10.1109/SPAWC.2013.6612074 %0 Conference Paper %B Int. Conf. Acoust., Speech, Signal Process. (ICASSP) %D 2013 %T Autocorrelation-based adaptation rule for feedback equalization in Wideband Full-Duplex Amplify-and-Forward MIMO relays %A Emilio Antonio-Rodríguez %A R. López-Valcarce %A Taneli Riihonen %A Stefan Werner %A Risto Wichman %K adaptive signal processing %K dynacs %K full duplex %XSimultaneous 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.

%B Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
%G eng
%R 10.1109/ICASSP.2013.6638606
%0 Conference Paper
%B Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
%D 2013
%T Cancelling self-interference in full-duplex relays without Angle-of-Arrival information
%A Emilio Antonio-Rodríguez
%A R. López-Valcarce
%K adaptive signal processing
%K dynacs
%K full duplex
%X 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.

%B Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
%G eng
%R 10.1109/ICASSP.2013.6638558
%0 Journal Article
%J IEEE J. Selected Areas in Communications
%D 2012
%T An Adaptive Feedback Canceller for Full-Duplex Relays Based on Spectrum Shaping
%A R. López-Valcarce
%A Emilio Antonio-Rodríguez
%A C. Mosquera
%A Fernando Pérez-González
%K adaptive signal processing
%K dynacs
%K full duplex
%X 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.

%B IEEE J. Selected Areas in Communications
%V 30
%P 1566 - 1577
%8 08/2012
%G eng
%N 8
%R 10.1109/JSAC.2012.120923
%0 Conference Paper
%B IEEE 13th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012)
%D 2012
%T Adaptive self-interference suppression for full-duplex relays with multiple receive antennas
%A Emilio Antonio-Rodríguez
%A R. López-Valcarce
%K adaptive signal processing
%K dynacs
%K full duplex
%X 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.

%B IEEE 13th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012)
%I IEEE
%C Çesme, Turkey
%8 07/2012
%G eng
%R 10.1109/SPAWC.2012.6292948
%0 Conference Paper
%B Asilomar Conference on Signals, Systems, and Computers
%D 2012
%T Optimum Training for CSI Acquisition in Cognitive Radio Channels
%A Alberto Rico-Alvariño
%A C. Mosquera
%K adaptive signal processing
%K cognitive radio
%K dynacs
%B Asilomar Conference on Signals, Systems, and Computers
%C Pacific Grove, CA
%G eng
%R 10.1109/ACSSC.2012.6488973
%0 Journal Article
%J IEEE Transactions on Information Forensics and Security
%D 2011
%T Secure Adaptive Filtering
%A Juan Ramón Troncoso-Pastoriza
%A Fernando Pérez-González
%K adaptive signal processing
%K computational complexity
%K cryptography
%K digital data protection
%K encrypted domain
%K homomorphic encryption systems
%K least mean squares algorithm
%K least mean squares methods
%K privacy
%K secure adaptive filtering
%K security
%K signal privacy preservation
%K SPED techniques
%K watermarking
%B IEEE Transactions on Information Forensics and Security
%V 6
%P 469 -485
%8 June
%G eng
%R 10.1109/TIFS.2011.2109385
%0 Thesis
%D 2010
%T Design of Nonlinear Precoding and Estimation Schemes for Advanced Communication Systems
%A Marcos Álvarez-Díaz
%K adaptive signal processing
%K satcom
%V Ph.D.
%8 04/2010
%G eng
%9 Ph.D. thesis
%0 Conference Paper
%B IEEE Conference on Decision and Control / European Control Conference (CDC/ECC)
%D 2005
%T Analysis of a first-order adaptive recursive predictor
%A R. López-Valcarce
%K adaptive signal processing
%K equalization
%K second-order statistics
%B IEEE Conference on Decision and Control / European Control Conference (CDC/ECC)
%C Seville, Spain
%G eng
%R 10.1109/CDC.2005.1582919
%0 Conference Paper
%B IEEE Workshop on Statistical Signal Processing (SSP)
%D 2005
%T Diamond contour-based phase recovery for (cross-)QAM constellations
%A Marcos Álvarez-Díaz
%A R. López-Valcarce
%K adaptive signal processing
%K synchronization
%B IEEE Workshop on Statistical Signal Processing (SSP)
%C Bordeaux, France
%G eng
%R 10.1109/SSP.2005.1628678
%0 Journal Article
%J IEEE Transactions on Signal Processing
%D 2005
%T Realizable minimum mean-squared error channel shorteners
%A R. López-Valcarce
%K adaptive signal processing
%K Channel shortening
%B IEEE Transactions on Signal Processing
%V 53
%P 4354–4362
%8 November
%G eng
%R 10.1109/TSP.2005.857050
%0 Journal Article
%J IEEE Transactions on Signal Processing
%D 2004
%T Realizable linear and decision feedback equalizers: properties and connections
%A R. López-Valcarce
%K adaptive signal processing
%K channel equalization
%B IEEE Transactions on Signal Processing
%V 52
%P 757–773
%8 March
%G eng
%1 **Best Paper Award** of the IEEE Signal Processing Society (Signal Processing for Communications), 2005