Configuring hybrid precoders and combiners is the main challenge to be solved to operate at millimeter wave (mmWave) frequencies. The use of hybrid architectures imposse hardware constraints on the analog precoder that need to be carefully dealt with. In this paper, we develop hybrid precoders and combiners aiming at minimizing the Euclidean distance with respect to the approximate all-digital precoders and combiners maximizing the spectral efficiency under per-antenna power constraints. Numerical results demonstrate the effectiveness of the proposed design method, whose performance is close to that of the all-digital solution.

JF - IEEE Int. Conf. Acoustics, Speech and Signal Processing (ICASSP) PB - IEEE CY - Brighton, UK ER - TY - CONF T1 - Adjacent Beams Resource Sharing to Serve Hot Spots : A Rate Splitting Approach T2 - 36th International Communications Satellite Systems Conference (ICSSC) Y1 - 2018 A1 - Tomás Ramírez A1 - Carlos Mosquera A1 - Màrius Caus A1 - Adriano Pastore A1 - Nader Alagha A1 - Nele Noels AB -This work addresses the uneven traffic demand scenario in multi-beam satellite systems, in which a hot-spot beam

is surrounded by cold beams. After partitioning the hotspot beam in different sectors, resource pulling from cold

neighbouring beams is allowed following an aggressive frequency-reuse scheme. As a consequence, the level of

the co-channel interference within the hot-spot beam increases. A scheme known as Non-Coherent Rate-Splitting (NCRS)

is employed to cope with this interference, based on the exclusive use of magnitude channel state information at the transmitter (CSIT).

The receiver complexity is increased with respect to full CSIT precoding schemes, which are considered for benchmarking purposes. Different NCRS strategies are analyzed and compared with several partial and full CSIT schemes. The proposed solution not only shows an improvement with respect to partial CSIT benchmarks, but also displays a competitive performance against full CSIT precoders.

JF - 36th International Communications Satellite Systems Conference (ICSSC)
CY - Niagara Falls, Canada
ER -
TY - JOUR
T1 - Distributed Precoding Systems in Multi-Gateway Multibeam Satellites: Regularization and Coarse Beamforming
JF - IEEE Transactions on Wireless Communication
Y1 - 2018
A1 - Carlos Mosquera
A1 - R. López-Valcarce
A1 - Tomás Ramírez
A1 - Vahid Joroughi
ER -
TY - CONF
T1 - Exploratory Analysis of Superposition Coding and Rate Splitting for Multibeam Satellite Systems
T2 - 15th International Symposium on Wireless Communication Systems (ISWCS)
Y1 - 2018
A1 - Màrius Caus
A1 - Adriano Pastore
A1 - Mònica Navarro
A1 - Tomás Ramírez
A1 - Carlos Mosquera
A1 - Nele Noels
A1 - Nader Alagha
A1 - Ana I. Perez-Neira
JF - 15th International Symposium on Wireless Communication Systems (ISWCS)
CY - Lisbon, Portugal
ER -
TY - CONF
T1 - Locally optimal invariant detector for testing equality of two power spectral densities
T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
Y1 - 2018
A1 - David Ramírez
A1 - Daniel Romero
A1 - Javier Vía
A1 - R. López-Valcarce
A1 - Ignacio Santamaría
KW - cognitive radio
KW - winter
AB - This work addresses the problem of determining whether two multivariate random time series have the same power spectral density

(PSD), which has applications, for instance, in physical-layer security and cognitive radio. Remarkably, existing detectors for this

problem do not usually provide any kind of optimality. Thus, we study here the existence under the Gaussian assumption of optimal

invariant detectors for this problem, proving that the uniformly most powerful invariant test (UMPIT) does not exist. Thus, focusing on

close hypotheses, we show that the locally most powerful invariant test (LMPIT) only exists for univariate time series. In the multivariate

case, we prove that the LMPIT does not exist. However, this proof suggests two LMPIT-inspired detectors, one of which outperforms

previously proposed approaches, as computer simulations show.

JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
CY - Calgary, Canada
ER -
TY - CONF
T1 - Message-Splitting for Interference Cancellation in Multibeam Satellite Systems
T2 - 9th Advanced Satellite Multimedia Systems Conference (ASMS) and 15th Signal Processing for Space Communications Workshop (SPSC)
Y1 - 2018
A1 - Tomás Ramírez
A1 - Carlos Mosquera
A1 - Màrius Caus
A1 - Adriano Pastore
A1 - Mònica Navarro
A1 - Nele Noels
JF - 9th Advanced Satellite Multimedia Systems Conference (ASMS) and 15th Signal Processing for Space Communications Workshop (SPSC)
CY - Berlin, Germany
ER -
TY - CONF
T1 - Symbol-Asynchronous Transmission In Multibeam Satellite User Down-Link: Rate Regions For Novel Superposition Coding Schemes
T2 - 6th IEEE Global Conference on Signal and Information Processing
Y1 - 2018
A1 - Nele Noels
A1 - Marc Moeneclaey
A1 - Tomás Ramírez
A1 - Carlos Mosquera
A1 - Màrius Caus
A1 - Adriano Pastore
AB - We consider the forward link of a multibeam satellite system with high spectral reuse and the novel low-complexity transmission and detection strategies from ["“Exploratory analysis of superposition coding and rate splitting for multibeam satellite systems", ISWCS 2018]. More specifically, we study the impact of a time offset between the antenna beams that cooperate to simultaneously serve a given user. Assuming Gaussian signaling, we provide closed-form expressions for the achievable rate region. It is demonstrated that, in the absence of timing information at the gateway, this region is not affected by a time offset. Our numerical results further show that, in case timing is known at the gateway, an offset of half a symbol period at both user terminals is optimal in terms of spectral efficiency.

JF - 6th IEEE Global Conference on Signal and Information Processing ER - TY - JOUR T1 - Testing equality of multiple power spectral density matrices JF - IEEE Trans. Signal Processing Y1 - 2018 A1 - David Ramírez A1 - Daniel Romero A1 - Javier Vía A1 - R. López-Valcarce A1 - Ignacio Santamaría KW - winter VL - 66 IS - 23 ER - TY - CONF T1 - Two-Level Precoding for High Throughput Satellites with non-Cooperative Gateways T2 - 22nd International Workshop on Smart Antennas (WSA) Y1 - 2018 A1 - Tomás Ramírez A1 - Carlos Mosquera A1 - Roberto López-Valcarce JF - 22nd International Workshop on Smart Antennas (WSA) ER - TY - CONF T1 - Defending Surveillance Sensor Networks Against Data-Injection Attacks via Trusted Nodes T2 - European Signal Processing Conference (EUSIPCO) Y1 - 2017 A1 - R. López-Valcarce A1 - Daniel Romero KW - winter KW - wsn AB -By injecting false data through compromised sensors, an adversary can drive the probability of detection in a sensor network-based spatial field surveillance system to arbitrarily low values. As a countermeasure, a small subset of sensors may be secured. Leveraging the theory of Matched Subspace Detection, we propose and evaluate several detectors that add robustness to attacks when such trusted nodes are available. Our results reveal the performance-security tradeoff of these schemes and can be used to determine the number of trusted nodes required for a given performance target.

JF - European Signal Processing Conference (EUSIPCO)
CY - Kos Island, Greece
ER -
TY - CONF
T1 - Distributed Precoding Systems in Multi-Gateway Multibeam Satellites
T2 - 35th AIAA International Communications Satellite Systems Conference
Y1 - 2017
A1 - Carlos Mosquera
A1 - R. López-Valcarce
A1 - Tomás Ramírez
KW - precoding
KW - satcom
JF - 35th AIAA International Communications Satellite Systems Conference
CY - Trieste,Italy
ER -
TY - JOUR
T1 - FER Estimation in a Memoryless BSC with Variable Frame Length and Unreliable ACK/NAK Feedback
JF - IEEE Transactions on Wireless Communications
Y1 - 2017
A1 - Alberto Rico-Alvariño
A1 - R. López-Valcarce
A1 - Carlos Mosquera
A1 - Robert W. Heath Jr.
KW - adaptive signal processing
KW - compass
KW - Cramér-Rao bound (CRB)
KW - frame error rate
KW - myrada
KW - winter
AB - 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.

VL - 16
IS - 6
ER -
TY - JOUR
T1 - Learning Power Spectrum Maps from Quantized Power Measurements
JF - IEEE Transactions on Signal Processing
Y1 - 2017
A1 - Daniel Romero
A1 - Seung-Jun Kim
A1 - Georgios Giannakis
A1 - R. López-Valcarce
KW - cognitive radio
KW - compass
KW - compressed sensing
KW - spectrum sensing
KW - winter
KW - wsn
AB - Using power measurements collected by a network of low-cost sensors, power spectral density (PSD) maps are con-

structed to capture the distribution of RF power across space and frequency. Linearly compressed and quantized power measure-

ments enable wideband sensing at affordable implementation complexity using a small number of bits. Strengths of data- and model-

driven approaches are combined to develop estimators capable of incorporating multiple forms of spectral and propagation prior

information while fitting the rapid variations of shadow fading across space. To this end, novel nonparametric and semiparametric

formulations are investigated. It is shown that the desired PSD maps can be obtained using support vector machine-type solvers.

In addition to batch approaches, an online algorithm attuned to real-time operation is developed. Numerical tests assess the performance of the novel algorithms.

VL - 65
IS - 10
ER -
TY - JOUR
T1 - Wideband full-duplex MIMO relays with blind adaptive self-interference cancellation
JF - Signal Processing
Y1 - 2017
A1 - Emilio Antonio-Rodríguez
A1 - Stefan Werner
A1 - R. López-Valcarce
A1 - Taneli Riihonen
A1 - Risto Wichman
KW - adaptive signal processing
KW - compass
KW - full duplex
KW - winter
AB - 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.

VL - 130
ER -
TY - CONF
T1 - Array thinnig for antenna selection in millimeter wave MIMO systems
T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
Y1 - 2016
A1 - C. Rusu
A1 - Nuria González-Prelcic
A1 - R. W. Heath Jr
KW - compass
KW - mmWave
JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
ER -
TY - JOUR
T1 - Compressive Covariance Sensing: Structure-Based Compressive Sensing Beyond Sparsity
JF - IEEE Signal Processing Magazine
Y1 - 2016
A1 - Daniel Romero
A1 - Dyonisius D Ariananda
A1 - Zhi Tian
A1 - Geert Leus
KW - compass
KW - compressed sensing
AB - Compressed sensing deals with the reconstruction of signals

from sub-Nyquist samples by exploiting the sparsity of their

projections onto known subspaces. In contrast, the present

article is concerned with the reconstruction of second-order

statistics, such as covariance and power spectrum, even in

the absence of sparsity priors. The framework described here

leverages the statistical structure of random processes to

enable signal compression and offers an alternative perspective

at sparsity-agnostic inference. Capitalizing on parsimonious

representations, we illustrate how compression and reconstruction

tasks can be addressed in popular applications such

as power spectrum estimation, incoherent imaging, direction

of arrival estimation, frequency estimation, and wideband

spectrum sensing.

VL - 33
IS - 1
ER -
TY - CONF
T1 - Design of data-injection adversarial attacks against spatial field detectors
T2 - IEEE Workshop on Statistical Signal Processing (SSP)
Y1 - 2016
A1 - R. López-Valcarce
A1 - Daniel Romero
KW - adversarial signal processing
KW - compass
KW - wsn
AB - Data-injection attacks on spatial field detection corrupt a subset of measurements to cause erroneous decisions. We consider a centralized decision scheme exploiting spatial field smoothness to overcome lack of knowledge on system parameters such as noise variance. We obtain closed-form expressions for system performance and investigate strategies for an intruder injecting false data in a fraction of the sensors in order to reduce the probability of detection. The problem of determining the most vulnerable subset of sensors is also analyzed.

JF - IEEE Workshop on Statistical Signal Processing (SSP) CY - Palma de Mallorca, Spain ER - TY - JOUR T1 - Designing incoherent frames through convex techniques for optimized compressed sensing JF - IEEE Transactions on Signal Processing Y1 - 2016 A1 - Cristian Rusu A1 - Nuria González-Prelcic KW - compass KW - compressed sensing VL - 64 IS - 9 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 - Fast orthonormal sparsifying transforms based on Householder reflectors
JF - IEEE Transactions on Signal Processing
Y1 - 2016
A1 - C. Rusu
A1 - Nuria González-Prelcic
A1 - R.W. Heath Jr.
KW - compass
KW - compressed sensing
VL - 64
IS - 24
ER -
TY - CONF
T1 - Full-duplex operation in two-way broadcast service for maritime applications
T2 - 8th Advanced Satellite Multimedia Systems Conference and 14th Signal Processing for Space Communications Workshop
Y1 - 2016
A1 - Tomás Ramírez
A1 - Carlos Mosquera
KW - compass
KW - full duplex
KW - satcom
JF - 8th Advanced Satellite Multimedia Systems Conference and 14th Signal Processing for Space Communications Workshop
ER -
TY - JOUR
T1 - Hybrid MIMO Architectures for Millimeter Wave Communications: Phase Shifters or Switches?
JF - IEEE Access
Y1 - 2016
A1 - Mendez-Rial, Roi
A1 - Rusu, Cristian
A1 - Nuria González-Prelcic
A1 - Alkhateeb, A.
A1 - Heath Jr, Robert W.
VL - 4
UR - http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7370753
ER -
TY - CONF
T1 - Hybrid precoders and combiners for mmWave MIMO systems with per-antenna power constraints
T2 - IEEE Global Telecommunications Conf. (GLOBECOM)
Y1 - 2016
A1 - R. López-Valcarce
A1 - Nuria González-Prelcic
A1 - Cristian Rusu
A1 - R. W. Heath, Jr
KW - compass
KW - mmWave
AB - This paper considers the design of hybrid precoders

and combiners for mmWave MIMO systems with per-antenna

power constraints and the additional limitations introduced by

the phase-shifting network in the analog processing stage. Previous

hybrid designs were obtained using a total power constraint,

but in practical implementations per-antenna constraints are

more realistic, specially at mmWave, given the large number of

power amplifiers used in the transmit array. Assuming perfect

channel knowledge, we obtain first an approximation to the alldigital

solution for the precoder and the combiner given the

per-antenna constraints. Then, we develop a new method for the

design of the hybrid precoder and combiner which attempts to

match such all-digital approximation. Simulation results show

the effectiveness of the proposed approach, which performs close

to the all-digital solution.

JF - IEEE Global Telecommunications Conf. (GLOBECOM)
ER -
TY - JOUR
T1 - Link adaptation in mobile satellite links: schemes for different degrees of CSI knowledge
JF - International Journal of Satellite Communications and Networking
Y1 - 2016
A1 - Alberto Rico-Alvariño
A1 - Jesus Arnau
A1 - Carlos Mosquera
KW - compass
KW - satcom
VL - 34
IS - 5
ER -
TY - JOUR
T1 - Low complexity hybrid precoding strategies for millimeter wave communication systems
JF - IEEE Trans. Wireless Communications
Y1 - 2016
A1 - Cristian Rusu
A1 - Roi Méndez-Rial
A1 - Nuria González-Prelcic
A1 - Robert W. Heath Jr.
KW - compass
KW - mmWave
AB - Millimeter communication systems use large antenna arrays to provide good average received power and to take advantage of multi-stream MIMO communication. Unfortunately, due to power consumption in the analog front-end, it is impractical to perform beamforming and fully digital precoding at baseband. Hybrid precoding/combining architectures have been proposed to overcome this limitation. The hybrid structure splits the MIMO processing between the digital and analog domains, while keeping the performance close to that of the fully digital solution. In this paper, we introduce and analyze several algorithms that efficiently design hybrid precoders and combiners starting from the known optimum digital precoder/combiner, which can be computed when perfect channel state information is available. We propose several low complexity solutions which provide different trade-offs between performance and complexity. We show that the proposed iterative solutions perform better in terms of spectral efficiency and/or are faster than previous methods in the literature. All of them provide designs which perform close to the known optimal digital solution. Finally, we study the effects of quantizing the analog component of the hybrid design and show that even with coarse quantization, the average rate performance is good.

VL - 15 IS - 12 ER - TY - JOUR T1 - An overview of signal processing techniques for millimeter wave MIMO systems JF - IEEE J. Selected Topics in Signal Processing. Special issue on Signal Processing for Millimeter Wave Wireless Communications Y1 - 2016 A1 - Robert W. Heath Jr. A1 - Nuria González-Prelcic A1 - Sundeep Rangan A1 - Wonil Roh A1 - Akbar M. Sayeed KW - compass KW - mmWave AB -Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

VL - 10 IS - 3 ER - TY - JOUR T1 - Properties of real and complex ETFs and their application to the design of low coherence frames JF - Linear Algebra and its Applications Y1 - 2016 A1 - Cristian Rusu A1 - Nuria González-Prelcic A1 - Robert W. Heath Jr. VL - 508 UR - http://www.sciencedirect.com/science/article/pii/S0024379516302555 ER - TY - CONF T1 - The use of unit norm tight measurement matrices for one-bit compressed sensing T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) Y1 - 2016 A1 - C. Rusu A1 - Nuria González-Prelcic A1 - R. W. Heath Jr. KW - compass KW - compressed sensing AB -In this paper we analyze the mean squared error (MSE) for one-bit compressed sensing schemes based on measurement matrices that correspond to unit norm tight frames. We show that, as in the unquantized case, sensing with unit norm tight frames improves the MSE in the reconstruction of sparse vectors from one-bit measurements using l1 and thresholding algorithms. From our analytical and experimental results we conclude that when implementing one-bit compressed sensing schemes with fixed measurement matrices unit norm tight frames are the measurements of choice

JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) ER - TY - CONF T1 - Adaptive one-bit compressive sensing with application to low-precision receivers at mmWave T2 - IEEE Global Telecommunications Conf. (GLOBECOM), Y1 - 2015 A1 - C. Rusu A1 - R. Méndez-Rial A1 - Nuria González-Prelcic A1 - R. W. Heath, Jr KW - compass KW - mmWave JF - IEEE Global Telecommunications Conf. (GLOBECOM), ER - TY - CONF T1 - Attack detectors for data aggregation in clustered sensor networks T2 - European Signal Processing Conf. (EUSIPCO) Y1 - 2015 A1 - R. López-Valcarce A1 - Daniel Romero KW - adversarial signal processing KW - compass KW - wsn AB -Among many security threats to sensor networks, compromised sensing is particularly challenging due to the fact that it cannot be addressed by standard authentication approaches. We consider a clustered scenario for data aggregation in which an attacker injects a disturbance in sensor readings. Casting the problem in an estimation framework, we systematically apply the Generalized Likelihood Ratio approach to derive attack detectors. The analysis under different attacks reveals that detectors based on similarity of means across

clusters are suboptimal, with Bartlett’s test for homoscedasticity constituting a good candidate when lacking a priori knowledge of the variance of the underlying distribution.

JF - European Signal Processing Conf. (EUSIPCO)
PB - EURASIP
CY - Nice, France
ER -
TY - CONF
T1 - An attack on antenna subset modulation for millimeter-wave communication
T2 - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
Y1 - 2015
A1 - Cristian Rusu
A1 - Nuria González-Prelcic
A1 - Robert W. Heath Jr.
KW - adversarial signal processing
KW - compass
KW - mmWave
AB - Antenna subset modulation (ASM) is a physical layer security technique that is well suited for millimeter wave communication systems. The key idea is to vary the radiation pattern at the symbol rate by selecting one from a subset of patterns with a similar main lobe and different side lobes. This paper shows that ASM is not robust to an eavesdropper that makes multiple simultaneous measurements at multiple angles. The measurements are combined and used to formulate an estimation problem to undo the effects of the side lobe randomization. Simulations show the performance of the estimation algorithms and how the eavesdropper can effectively recover the information if the signal-to-noise ratio exceeds a certain threshold. Using fewer active radio frequency chains makes it harder for the attacker to recover the transmit symbol, at the expense of more grating lobes.

JF - IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) PB - IEEE CY - Brisbane, Australia ER - TY - JOUR T1 - Compression Limits for Random Vectors with Linearly Parameterized Second-Order Statistics JF - IEEE Trans. Information Theory Y1 - 2015 A1 - Daniel Romero A1 - R. López-Valcarce A1 - Geert Leus KW - compass KW - compressed sensing AB -The class of complex random vectors whose covariance

matrix is linearly parameterized by a basis of Hermitian

Toeplitz (HT) matrices is considered, and the maximum

compression ratios that preserve all second-order information

are derived — the statistics of the uncompressed vector must

be recoverable from a set of linearly compressed observations.

This kind of vectors arises naturally when sampling widesense

stationary random processes and features a number of

applications in signal and array processing.

Explicit guidelines to design optimal and nearly optimal

schemes operating both in a periodic and non-periodic fashion

are provided by considering two of the most common linear

compression schemes, which we classify as dense or sparse. It

is seen that the maximum compression ratios depend on the

structure of the HT subspace containing the covariance matrix of

the uncompressed observations. Compression patterns attaining

these maximum ratios are found for the case without structure as

well as for the cases with circulant or banded structure. Universal

samplers are also proposed to compress unknown HT subspaces.

VL - 61
IS - 3
ER -
TY - JOUR
T1 - Cramér-Rao Bounds for SNR Estimation of Oversampled Linearly Modulated Signals
JF - IEEE Trans. Signal Processing
Y1 - 2015
A1 - R. López-Valcarce
A1 - J. Villares
A1 - J. Riba
A1 - W. Gappmair
A1 - C. Mosquera
KW - adaptive signal processing
KW - compass
KW - Cramér-Rao bound (CRB)
KW - dynacs
KW - oversampling
KW - Signal-to-noise ratio (SNR)
AB - 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.

VL - 63
IS - 7
ER -
TY - CONF
T1 - Dictionary-free Hybrid Precoders and Combiners for mmWave MIMO Systems
T2 - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Y1 - 2015
A1 - Roi Méndez-Rial
A1 - Cristian Rusu
A1 - Nuria González-Prelcic
A1 - Robert W. Heath Jr.
KW - compass
KW - mmWave
JF - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
PB - IEEE
CY - Stockholm, Sweden
ER -
TY - THES
T1 - Estimation, Detection, and Learning for Dynamic Spectrum Access
Y1 - 2015
A1 - Daniel Romero
KW - cognitive radio
KW - compass
KW - dynacs
KW - wsn
PB - University of Vigo
CY - Vigo, Spain
VL - Ph.D.
ER -
TY - CONF
T1 - Low Complexity Hybrid Sparse Precoding and Combining in Millimeter Wave MIMO Systems
T2 - IEEE Int. Conference on Communications (ICC)
Y1 - 2015
A1 - Cristian Rusu
A1 - Roi Méndez-Rial
A1 - Nuria González-Prelcic
A1 - Robert W. Heath Jr.
KW - compass
KW - mmWave
JF - IEEE Int. Conference on Communications (ICC)
PB - IEEE
CY - London, UK
ER -
TY - CONF
T1 - Low Resolution Adaptive Compressed Sensing for mmWave MIMO receivers
T2 - Asilomar Conf. on Signals, Systems, and Computers
Y1 - 2015
A1 - C. Rusu
A1 - Nuria González-Prelcic
A1 - R.W. Heath Jr.
KW - compass
KW - mmWave
JF - Asilomar Conf. on Signals, Systems, and Computers
ER -
TY - CONF
T1 - Robust Adaptive Coding and Modulation Scheme for the Mobile Satellite Forward Link
T2 - IEEE International Workshop on Signal Processing Advances in Wireless Communications, SPAWC
Y1 - 2015
A1 - Alberto Rico-Alvariño
A1 - Anxo Tato
A1 - Carlos Mosquera
KW - compass
KW - satcom
JF - IEEE International Workshop on Signal Processing Advances in Wireless Communications, SPAWC
ER -
TY - CONF
T1 - Spectrum Cartography using quantized observations
T2 - IEEE Int. Conference on Acoustics, Speech and Signal Processing (ICASSP)
Y1 - 2015
A1 - Daniel Romero
A1 - Seung-Jun Kim
A1 - R. López-Valcarce
A1 - Georgios Giannakis
KW - cognitive radio
KW - compass
KW - compressed sensing
KW - spectrum sensing
AB - This work proposes a spectrum cartography algorithm used for learning the power spectrum distribution over a wide frequency band across a given geographic area. Motivated by low-complexity sensing hardware and stringent communication constraints, compressed and quantized measurements are considered. Setting out from a nonparametric regression framework, it is shown that a sensible approach leads to a support vector machine formulation. The simulated tests verify that accurate spectrum maps can be constructed using a simple sensing architecture with significant savings in the feedback.

JF - IEEE Int. Conference on Acoustics, Speech and Signal Processing (ICASSP)
PB - IEEE
CY - Brisbane, Australia
ER -
TY - CONF
T1 - Subspace-constrained SINR optimization in MIMO full-duplex relays under limited dynamic range
T2 - IEEE 16th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Y1 - 2015
A1 - Emilio Antonio-Rodríguez
A1 - R. López-Valcarce
A1 - Taneli Riihonen
A1 - Stefan Werner
A1 - Risto Wichman
KW - adaptive signal processing
KW - compass
KW - full duplex
AB - 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.

JF - IEEE 16th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
PB - IEEE
CY - Stockholm, Sweden
ER -
TY - JOUR
T1 - Active Interference Cancellation for OFDM Spectrum Sculpting: Linear Processing is Optimal
JF - IEEE Communications Letters
Y1 - 2014
A1 - Schmidt, J.F.
A1 - Daniel Romero
A1 - R. López-Valcarce
KW - cognitive radio
KW - compass
KW - dynacs
KW - spectrum shaping
AB - Active interference cancellation (AIC) is a multicarrier spectrum sculpting technique which reduces the power of undesired out-of-band emissions by adequately modulating a subset of reserved cancellation subcarriers. In most schemes online complexity is a concern, and thus cancellation subcarriers have traditionally been constrained to linear combinations of the data subcarriers. Recent AIC designs truly minimizing out-of-band emission shift complexity to the offline design stage, motivating the consideration of more general mappings to improve performance. We show that there is no loss in optimality incurred by constraining these mappings to the set of linear functions.

VL - 18 IS - 9 ER - TY - CONF T1 - Balancing Closed and Open Loop CSI in Mobile Satellite Link Adaptation T2 - Proc. ASMS & SPSC Y1 - 2014 A1 - Alberto Rico-Alvariño A1 - Arnau, Jesus A1 - Carlos Mosquera KW - dynacs KW - satcom JF - Proc. ASMS & SPSC CY - Livorno, Italy U1 -

**Best paper award**

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.

JF - ICASSP2014 - Signal Processing for Communications and Networking (ICASSP2014 - SPCOM) CY - Florence, Italy ER - TY - CONF T1 - How to Implement Doubly-Stochastic Matrices for Consensus-Based Distributed Algorithms T2 - IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM) Y1 - 2014 A1 - S. Valcárcel-Macua A1 - C. Moreno-León A1 - J. S. Romero A1 - Silvana Silva Pereira A1 - Javier Zazo A1 - Alba Pagès-Zamora A1 - R. López-Valcarce A1 - S. Zazo KW - compass KW - dynacs KW - wsn AB -Doubly-stochastic matrices are usually required by

consensus-based distributed algorithms. We propose a simple

and efficient protocol and present some guidelines for implementing

doubly-stochastic combination matrices even in noisy,

asynchronous and changing topology scenarios. The proposed

ideas are validated with the deployment of a wireless sensor

network, in which nodes run a distributed algorithm for robust

estimation in the presence of nodes with faulty sensors.

JF - IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM)
CY - A Coruña, Spain
ER -
TY - JOUR
T1 - Learning-Based Adaptive Transmission for Limited Feedback Multiuser MIMO-OFDM
JF - IEEE Transactions on Wireless Communications
Y1 - 2014
A1 - Alberto Rico-Alvariño
A1 - Robert W. Heath Jr.
KW - adaptive signal processing
KW - dynacs
ER -
TY - CONF
T1 - Low-Power Active Interference Cancellation for OFDM Spectrum Sculpting
T2 - European Signal Processing Conference (EUSIPCO)
Y1 - 2014
A1 - Schmidt, J.F.
A1 - Daniel Romero
A1 - R. López-Valcarce
AB - We present a low-power design for Active Interference

Cancellation (AIC) sculpting of the OFDM spectrum, based

on sparse design concepts. Optimal AIC designs compute

cancellation weights based on contributions from all data subcarriers.

Thus, as the number of subcarriers grows, power

consumption becomes a concern, and suboptimal solutions

that avoid involving all subcarriers are of interest. In this context,

we present novel sparse AIC designs based on a zeronorm

minimization of the matrix defining the cancellation

weights. These designs drastically reduce the number of operations

per symbol, and thus the power consumption, while allowing

to tune the loss with respect the optimal design. They

can be efficiently obtained and significantly outperform usual

thresholding or sparsity-inducing l_1-norm minimization approaches.

JF - European Signal Processing Conference (EUSIPCO)
UR - http://www.eurasip.org/Proceedings/Eusipco/Eusipco2014/HTML/papers/1569912103.pdf
ER -
TY - CONF
T1 - Nearly-Optimal Compression Matrices for Signal Power Estimation
T2 - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Y1 - 2014
A1 - Daniel Romero
A1 - R. López-Valcarce
KW - cognitive radio
KW - dynacs
JF - IEEE Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
CY - Toronto, Canada
ER -
TY - CONF
T1 - SINR Optimization in Wideband Full-Duplex MIMO Relays under Limited Dynamic Range
T2 - IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM)
Y1 - 2014
A1 - Emilio Antonio-Rodríguez
A1 - R. López-Valcarce
A1 - Taneli Riihonen
A1 - Stefan Werner
A1 - Risto Wichman
KW - adaptive signal processing
KW - compass
KW - full duplex
JF - IEEE Sensor Array and Multichannel Signal Processing Workshop (SAM)
CY - A Coruña, Spain
ER -
TY - JOUR
T1 - Spectrum Sensing for Wireless Microphone Signals using Multiple Antennas
JF - IEEE Trans. on Vehicular Technology
Y1 - 2014
A1 - Daniel Romero
A1 - R. López-Valcarce
KW - cognitive radio
KW - dynacs
AB - Spectrum sensors for cognitive radio are expected to deploy multiple antennas in order to overcome the noise uncertainty problem and minimize the effects of small-scale fading. Despite the requirement that these sensors must detect wireless microphone (WM) signals, works in the literature have focused either on general purpose multiantenna detectors, or single antenna WM detectors. We exploit the spatial structure and particular properties of WM waveforms to derive four multiantenna detectors for WM signals with different performance/ complexity tradeoffs. These detectors are based on the generalized likelihood ratio test, which is derived under several signal models exploiting either the fact that the bandwidth of a WM signal never exceeds 200 kHz, the property that these signals have a constant magnitude, or both. The proposed detectors do not require synchronization with the WM signal and are robust to the noise uncertainty problem as well as to small-scale fading. Using the simulation guidelines from the IEEE 802.22 standard, the novel multiantenna WM detectors are shown to outperform previous schemes, thus demonstrating the advantages of exploiting spatial correlation along with WM signal structure.
VL - 63
IS - 9
ER -
TY - CONF
T1 - Adaptive Self-interference Cancellation in Wideband Full-Duplex Decode-and-Forward MIMO Relays
T2 - IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Y1 - 2013
A1 - Emilio Antonio-Rodríguez
A1 - R. López-Valcarce
A1 - Taneli Riihonen
A1 - Stefan Werner
A1 - Risto Wichman
KW - adaptive signal processing
KW - dynacs
KW - full duplex
JF - IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
CY - Darmstadt, Germany
ER -
TY - CONF
T1 - Analytical Characterization of the Single Frequency Network Gain Using Effective SNR Metrics
T2 - The Tenth International Symposium on Wireless Communication Systems 2013 (ISWCS 2013)
Y1 - 2013
A1 - Alberto Rico-Alvariño
A1 - C. Mosquera
KW - broadcasting
KW - dynacs
KW - Effective SNR metrics
KW - Single Frequency Network
AB - The design of broadcasting networks operating in a single frequency way is challenging due to the difficulty of predicting the performance in a frequency selective channel, caused by natural multipath and echoes coming from different transmitters. In this paper we resort to the use of frame error rate prediction metrics (also known as effective SNR metrics) to characterize the performance gain (or loss) under different multipath and SNR regimes in a simplified scenario with two transmitters. The analysis shows clearly that receivers with a dominant line of sight reception and high SNR are more sensitive to the presence of echoes, while those users in low SNR or strong multipath conditions are easily enforced by the insertion of a second transmitter.

JF - The Tenth International Symposium on Wireless Communication Systems 2013 (ISWCS 2013) CY - Ilmenau, Germany ER - TY - CONF T1 - Autocorrelation-based adaptation rule for feedback equalization in Wideband Full-Duplex Amplify-and-Forward MIMO relays T2 - Int. Conf. Acoust., Speech, Signal Process. (ICASSP) Y1 - 2013 A1 - Emilio Antonio-Rodríguez A1 - R. López-Valcarce A1 - Taneli Riihonen A1 - Stefan Werner A1 - Risto Wichman KW - adaptive signal processing KW - dynacs KW - full duplex AB -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.

JF - Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
ER -
TY - CONF
T1 - Compressive Angular and Frequency Periodogram Reconstruction for Multiband Signals
T2 - IEEE Int. Workshop Comput. Advances Multi-Sensor Adaptive Process (CAMSAP)
Y1 - 2013
A1 - Ariananda, D. D.
A1 - Daniel Romero
A1 - Geert Leus
KW - cognitive radio
KW - dynacs
JF - IEEE Int. Workshop Comput. Advances Multi-Sensor Adaptive Process (CAMSAP)
CY - San Martin
ER -
TY - CONF
T1 - Compressive Covariance Sampling
T2 - Inform. Theory Appl. Workshop
Y1 - 2013
A1 - Daniel Romero
A1 - Geert Leus
KW - cognitive radio
KW - dynacs
JF - Inform. Theory Appl. Workshop
ER -
TY - CONF
T1 - Compressive wideband spectrum sensing with spectral prior information
T2 - Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
Y1 - 2013
A1 - Daniel Romero
A1 - R. López-Valcarce
A1 - Geert Leus
KW - cognitive radio
KW - dynacs
KW - spectrum sensing
AB - Wideband spectrum sensing provides a means to determine

the occupancy of channels spanning a broad range of frequencies.

Practical limitations impose that the acquisition should

be accomplished at a low rate, much below the Nyquist lower

bound. Dramatic rate reductions can be obtained by the observation

that only a few parameters need to be estimated in

typical spectrum sensing applications. This paper discusses

the joint estimation of the power of a number of channels,

whose power spectral density (PSD) is known up to a scale

factor, using compressive measurements. First, relying on

a Gaussian assumption, an efficient approximate maximum

likelihood (ML) technique is presented. Next, a least-squares

estimator is applied for the general non-Gaussian case.

JF - Int. Conf. Acoust., Speech, Signal Process. (ICASSP)
ER -
TY - Generic
T1 - Cross Layer Link Adaptation in Time Varying Mobile Satellite Channels with Statistical and Outdated CSIT
T2 - Asilomar Conference on Signals Systems and Computers
Y1 - 2013
A1 - Alberto Rico-Alvariño
A1 - J. Arnau
A1 - Carlos Mosquera
KW - dynacs
KW - satcom
JF - Asilomar Conference on Signals Systems and Computers
ER -
TY - CONF
T1 - Learning Based Link Adaptation in Multiuser MIMO-OFDM
T2 - 21st European Signal Processing Conference 2013 (EUSIPCO 2013)
Y1 - 2013
A1 - Alberto Rico-Alvariño
A1 - Robert W. Heath Jr.
KW - dynacs
KW - link adaptation
KW - Machine Learning
KW - Multiuser MIMO-OFDM
AB - Link adaptation in multiple user multiple-input multiple-output orthogonal frequency division multiplexing communication systems is challenging because of the coupling between user selection, mode selection, precoding, and equalization. In this paper, we present a methodology to perform link adaptation under this multiuser setting, focusing on the capabilities of IEEE 802.11ac. We propose to use a machine learning classifier to solve the problem of selecting a proper modulation and coding scheme, combined with a greedy algorithm that performs user and spatial mode selection. We observe that our solution offers good performance in the case of perfect channel state information or high feedback rate, while those scenarios with less feedback suffer some degradation due to inter-user interference.

JF - 21st European Signal Processing Conference 2013 (EUSIPCO 2013) CY - Marrakech, Morocco ER - TY - CONF T1 - Link Adaptation in MIMO-OFDM with Practical Impairments T2 - Asilomar Conference on Signals Systems and Computers Y1 - 2013 A1 - Alberto Rico-Alvariño A1 - Robert W. Heath Jr. KW - dynacs KW - link adaptation KW - MIMO-OFDM JF - Asilomar Conference on Signals Systems and Computers ER - TY - CONF T1 - Spectrum Sensing in Time-Varying Channels Using Multiple Antennas T2 - IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Darmstadt (Germany) Y1 - 2013 A1 - Daniel Romero A1 - R. López-Valcarce KW - cognitive radio KW - dynacs KW - spectrum sensing JF - IEEE 14th Int. Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Darmstadt (Germany) ER - TY - CONF T1 - Statistical Cross Layer Adaptation in Fast Fading Mobile Satellite Channels T2 - Globecom 2013 - Symposium on Selected Areas in Communications (GC13 SAC) Y1 - 2013 A1 - Alberto Rico-Alvariño A1 - J. Arnau A1 - C. Mosquera KW - dynacs KW - fast fading channels KW - link adaptation KW - mobile satellite KW - satcom AB -Link adaptation in mobile satellite channels is difficult because of the large propagation delays, the frequent signal blockage and the variation of the channel statistics. In this paper, we propose a cross-layer link adaptation strategy that exploits statistical, long-term CSI to increase the throughput when some retransmissions are available; this increase is obtained while meeting a target outage probability constraint. Our strategy takes as inputs the estimated packet error rates of the available modulation and coding schemes (MCS) and their rates; as an output, it returns the optimum sequence of MCS to be used. Results will also show that simple information acquisition strategies can still provide very good results.

JF - Globecom 2013 - Symposium on Selected Areas in Communications (GC13 SAC) CY - Atlanta, USA ER - TY - JOUR T1 - Wideband Spectrum Sensing From Compressed Measurements Using Spectral Prior Information JF - IEEE Trans. Signal Process. Y1 - 2013 A1 - Daniel Romero A1 - Geert Leus KW - cognitive radio KW - compressed sensing KW - dynacs KW - spectrum sensing VL - 61 ER - TY - CONF T1 - Adaptive Transmission Techniques for Mobile Satellite Links T2 - 30th AIAA International Communications Satellite Systems Conference (ICSSC) Y1 - 2012 A1 - Arnau, Jesus A1 - Alberto Rico-Alvariño A1 - C. Mosquera KW - dynacs KW - satcom JF - 30th AIAA International Communications Satellite Systems Conference (ICSSC) CY - Ottawa, Canada U1 -Detecting the presence of a white Gaussian signal distorted by a noisy time-varying channel is addressed by means of three different detectors. First, the generalized likelihood ratio test (GLRT) is found for the case where the channel has no temporal structure, resulting in the well-known Bartlett’s test. Then it is shown that, under the transformation group given by scaling factors, a locally most powerful invariant test (LMPIT) does not exist. Two alternative approaches are explored in the low signal-to-noise ratio (SNR) regime: the first assigns a prior probability density function (pdf) to the channel (hence modeled as random), whereas the second assumes an underlying basis expansion model (BEM) for the (now deterministic) channel and obtains the maximum likelihood (ML) estimates of the parameters relevant for the detection problem. The performance of these detectors is evaluated via Monte Carlo simulation.

JF - IEEE Statistical Signal Processing Workshop (SSP 2012)
PB - IEEE
CY - Ann Arbor, MI
ER -
TY - CONF
T1 - Detection of unknown constant magnitude signals in time-varying channels
T2 - 3rd Int. Workshop on Cognitive Information Processing (CIP 2012)
Y1 - 2012
A1 - Daniel Romero
A1 - R. López-Valcarce
KW - cognitive radio
KW - dynacs
KW - spectrum sensing
AB - Spectrum sensing constitutes a key ingredient in many cognitive radio paradigms in order to detect and protect primary transmissions. Most sensing schemes in the literature assume a time-invariant channel. However, when operating in low Signal-to-Noise Ratio (SNR) conditions, observation times are necessarily long and may become larger than the coherence time of the channel. In this paper the problem of detecting an unknown constant-magnitude waveform in frequency-flat time-varying channels with noise background of unknown variance is considered. The channel is modeled using a basis expansion model (BEM) with random coefficients. Adopting a generalized likelihood ratio (GLR) approach in order to deal with nuisance parameters, a non-convex optimization problem results. We discuss different possibilities to circumvent this problem, including several low complexity approximations to the GLR test as well as an efficient fixed-point iterative method to obtain the true GLR statistic. The approximations exhibit a performance ceiling in terms of probability of detection as the SNR increases, whereas the true GLR test does not. Thus, the proposed fixed-point iteration constitutes the preferred choice in applications requiring a high probability of detection.

JF - 3rd Int. Workshop on Cognitive Information Processing (CIP 2012) CY - Baiona, Spain ER - TY - CONF T1 - On the Effect of Echoes in Hybrid Terrestrial-Satellite Single Frequency Networks: Analysis and Countermeasures T2 - 2012 6th Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space Communications Workshop (SPSC) (ASMS/SPSC 2012) Y1 - 2012 A1 - Alberto Rico-Alvariño A1 - C. Mosquera KW - dynacs KW - Effective SNR KW - Hybrid Terrestrial- Satellite KW - satcom KW - Satellite OFDM KW - Single Frequency Network KW - Space-Time Coding AB -Hybrid Terrestrial Satellite Single Frequency Networks achieve large spectral efficiencies due to a higher frequency reuse, which is attained by transmitting the same waveform in the same frequency band from satellite and terrestrial transmitters. However, the presence of multiple transmitters propitiates the existence of the so-called SFN echoes, which can degrade the system performance even if they arrive within the OFDM guard interval. In this paper we characterize this effect by resorting to PER prediction metrics (or effective SNR metrics), and analyze two simple preprocessing schemes that mitigate this degradation: the use of Alamouti space-time codes, and a convenient prefiltering at the terrestrial transmitter.

JF - 2012 6th Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space Communications Workshop (SPSC) (ASMS/SPSC 2012) CY - Baiona, Spain ER - TY - CONF T1 - Generalized matched filter detector for fast fading channels T2 - IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP 2012) Y1 - 2012 A1 - Daniel Romero A1 - R. López-Valcarce A1 - Geert Leus KW - cognitive radio KW - dynacs KW - spectrum sensing AB -We consider the problem of detecting a known signal with constant magnitude immersed in noise of unknown variance,

when the propagation channel is frequency-flat and randomly

time-varying within the observation window. A Basis Expansion

Model with random coefficients is used for the channel, and a Generalized Likelihood Ratio approach is adopted in order to cope with deterministic nuisance parameters. The resulting scheme can be seen as a generalization of the well-known

Matched Filter detector, to which it reduces for timeinvariant

channels. Closed-form analytical expressions are provided for the distribution of the test statistic under both hypotheses, which allow to assess the detection performance.

JF - IEEE Int. Conf. on Acoustics, Speech and Signal Processing (ICASSP 2012)
PB - IEEE
CY - Kyoto, Japan
ER -
TY - CONF
T1 - Optimum Training for CSI Acquisition in Cognitive Radio Channels
T2 - Asilomar Conference on Signals, Systems, and Computers
Y1 - 2012
A1 - Alberto Rico-Alvariño
A1 - C. Mosquera
KW - adaptive signal processing
KW - cognitive radio
KW - dynacs
JF - Asilomar Conference on Signals, Systems, and Computers
CY - Pacific Grove, CA
ER -
TY - JOUR
T1 - Overlay Cognitive Transmission in a Multicarrier Broadcast Network with Dominant Line of Sight Reception
JF - IEEE Transactions on Wireless Communications
Y1 - 2012
A1 - Alberto Rico-Alvariño
A1 - C. Mosquera
A1 - Fernando Pérez-González
KW - cognitive radio
KW - dynacs
KW - satcom
ER -
TY - CONF
T1 - Overlay cognitive transmission in OFDM point to point systems exploiting primary feedback
T2 - 3rd International Workshop on Cognitive Information Processing (CIP)
Y1 - 2012
A1 - Alberto Rico-Alvariño
A1 - C. Mosquera
KW - cognitive radio
KW - dynacs
AB - A secondary user that tries to reuse the spectrum allocated to a primary user can exploit the knowledge of the primary message to perform this task. In particular, the overlay cognitive radio paradigm postulates the use of a fraction of the available power at the secondary transmitter to convey the primary message, so the spectral efficiency of the primary system is increased, and, therefore, some transmission resources (time slots or frequency bands) can be released to the secondary transmission while the primary user rate is kept constant. The fraction of released resources can be incremented if some channel state information is available at the secondary transmitter. In this paper, we present a scenario where the secondary transmitter maximizes the primary link quality (measured in terms of Effective SNR), and obtains its channel state information by exploiting the primary user SNR-based feedback.

JF - 3rd International Workshop on Cognitive Information Processing (CIP) CY - Baiona, Galicia, Spain ER - TY - Generic T1 - Overlay Spectrum Reuse in a Broadcast Network: Covering the Whole Grayscale of Spaces T2 - IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2012) Y1 - 2012 A1 - Alberto Rico-Alvariño A1 - C. Mosquera KW - cognitive radio KW - dynacs JF - IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2012) CY - Bellevue, WA ER - TY - CONF T1 - Overlay Spectrum Reuse in a Multicarrier Broadcast Network: Coverage Analysis T2 - The 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012) Y1 - 2012 A1 - Alberto Rico-Alvariño A1 - C. Mosquera A1 - Fernando Pérez-González KW - cognitive radio KW - dynacs AB -A secondary cognitive user overlaying its message in a broadcast multicarrier network is studied. The secondary user exploits the primary message knowledge to convey its own information while preserving the primary user coverage area, determined by a bound on the BER, and taking into account the degradation due to the insertion of an echo in a dominant line of sight environment. The results are compared with those obtained when the coverage area is defined in capacity terms, and regardless of the degradation caused by the secondary replica of the primary message.

JF - The 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012) CY - Cesme, Turkey ER - TY - CONF T1 - Overlay Spectrum Reuse in a Multicarrier Broadcast Network: Single Receiver Analysis T2 - The 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012) Y1 - 2012 A1 - Alberto Rico-Alvariño A1 - C. Mosquera A1 - Fernando Pérez-González KW - cognitive radio KW - dynacs AB -The overlay cognitive radio paradigm presents a framework where a secondary user exploits the knowledge of the primary user's message to improve spectrum utilization. A multicarrier broadcast network is one of the scenarios where this knowledge is possible: the secondary user could join a single frequency network and, therefore, gain access to the primary message. However, if the primary signal is received with a strong line of sight component, its relaying from the secondary transmitter does not suffice to ensure the primary user quality of service. In this paper we study the scenario where a secondary transmitter maximizes its own transmission rate, keeping the quality of a primary receiver over a given threshold. The analytical results, based on bit error rate bounds, are verified by means of software simulations and hardware tests.

JF - The 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2012) CY - Cesme, Turkey ER - TY - CONF T1 - Bandlimited or Constant Envelope? Exploiting Waveform Properties in Wireless Microphone Detection T2 - International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP) Y1 - 2011 A1 - Daniel Romero A1 - R. López-Valcarce KW - Bandlimited signals. KW - Constant Magnitude KW - dynamic spectrum access KW - Wireless Microphones JF - International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP) CY - San Juan, Puerto Rico ER - TY - CONF T1 - On the Co-existence of Primary and Secondary Transmitters in a Broadcast Network T2 - International Conference on Cognitive Radio and Advanced Spectrum Management Y1 - 2011 A1 - Alberto Rico-Alvariño A1 - C. Mosquera A1 - Fernando Pérez-González KW - Broadcast KW - cognitive radio KW - Overlay KW - Single Frequency Network JF - International Conference on Cognitive Radio and Advanced Spectrum Management CY - Barcelona, Catalonia, Spain ER - TY - JOUR T1 - Detection of Rank-P Signals in Cognitive Radio Networks With Uncalibrated Multiple Antennas JF - IEEE Trans. on Signal Processing Y1 - 2011 A1 - David Ramírez A1 - Gonzalo Vázquez-Vilar A1 - R. López-Valcarce A1 - Javier Vía A1 - Ignacio Santamaría KW - cognitive radio KW - dynacs KW - spectrum sensing AB -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.

VL - 59
IS - 8
ER -
TY - CONF
T1 - Distributed spectrum sensing with multiantenna sensors under calibration errors
T2 - IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Y1 - 2011
A1 - Daniel Romero
A1 - R. López-Valcarce
KW - ad hoc detectors
KW - antenna arrays
KW - calibration
KW - calibration errors
KW - cognitive radio
KW - energy detector
KW - generalized likelihood ratio
KW - log normal distribution
KW - lognormal shadowing
KW - multiantenna sensors
KW - Ricean fading
KW - spectrum sensing
KW - wireless medium
AB - Spectrum sensing design for Cognitive Radio systems is challenged by the nature of the wireless medium, which makes the detection requirements difficult to achieve by standalone sensors. To combat shadowing and fading, distributed strategies are usually proposed. However, most distributed approaches are based on the energy detector, which is not robust to noise uncertainty. This phenomenon can be overcome by multi-antenna sensors exploiting spatial independence of the noise process. We combine both ideas to develop distributed detectors for multiantenna sensors. Fusion rules are provided for sensors based on the Generalized Likelihood Ratio as well as for ad hoc detectors derived from geometric considerations. Simulation results are provided comparing the performance of the different strategies under lognormal shadowing and Ricean fading.

JF - IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC) ER - TY - CONF T1 - Encrypted Domain Processing for Cloud Privacy: Concept and Practical Experience T2 - International Conference on Cloud Computing and Services Science (CLOSER) Y1 - 2011 A1 - Daniel A. Rodríguez-Silva A1 - F. Javier González-Castaño A1 - Lilian Adkinson-Orellana A1 - Alexandre Fernández-Cordeiro A1 - Juan Ramón Troncoso-Pastoriza A1 - Daniel González-Martínez KW - cloud KW - privacy KW - security KW - watermarking JF - International Conference on Cloud Computing and Services Science (CLOSER) CY - Noordwijkerhout, The Netherlands ER - TY - CONF T1 - Multiantenna detection of constant-envelope signals in noise of unknown variance T2 - IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC) Y1 - 2011 A1 - Daniel Romero A1 - R. López-Valcarce KW - cognitive radio KW - multiantenna detection KW - spectrum sensing AB -Detection of unknown signals with constant modulus (CM) using multiple antennas in additive white Gaussian noise of unknown variance is considered. The channels from the source to each antenna are assumed frequency-flat and unknown. This problem is of interest for spectrum sensing in cognitive radio systems in which primary signals are known to have the CM property. Examples include analog frequency modulated signals such as those transmitted by wireless microphones in the TV bands and Gaussian Minimum Shift Keying modulated signals as in the GSM cellular standard. The proposed detector, derived from a Generalized Likelihood Ratio (GLR) approach, exploits both the CM property and the spatial independence of noise, outperforming the GLR test for Gaussian signals as shown by simulation.

JF - IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC) ER - TY - CONF T1 - Multiantenna detection under noise uncertainty and primary user's spatial structure T2 - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) Y1 - 2011 A1 - David Ramírez A1 - Gonzalo Vázquez-Vilar A1 - R. López-Valcarce A1 - Javier Vía A1 - Ignacio Santamaría KW - cognitive radio KW - generalized likelihood ratio test (GLRT) KW - spectrum sensing JF - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) PB - IEEE CY - Prage, Czech Republic ER - TY - CONF T1 - A new method for perspective correction of document images T2 - Document Recognition and Retrieval Y1 - 2011 A1 - José Rodríguez-Piñeiro A1 - Pedro Comesaña A1 - Fernando Pérez-González A1 - Alberto Malvido KW - Document image KW - perspective distortion correction KW - watermarking JF - Document Recognition and Retrieval T3 - Proc. of SPIE PB - SPIE CY - San Francisco, CA VL - 7874 ER - TY - CONF T1 - Multiantenna spectrum sensing: detection of spatial correlation among time-series with unknown spectra T2 - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) Y1 - 2010 A1 - David Ramírez A1 - Javier Vía A1 - Ignacio Santamaría A1 - R. López-Valcarce A1 - L. L. Scharf KW - cognitive radio KW - coherence spectrum KW - generalized likelihood ratio test KW - Hadamard ratio KW - multiple-channel signal detection JF - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) CY - Dallas, TX ER - TY - CONF T1 - Performance Analysis of Distributed Tracking with Consensus on Noisy Time-Varying Graphs T2 - Advanced Satellite Multimedia Systems Conference (ASMA) Y1 - 2010 A1 - Yongxiang Ruan A1 - Sudhaman K. Jayaweera A1 - C. Mosquera KW - connectivity graph KW - distributed local Kalman filtering KW - distributed tracking KW - distributed tracking with consensus KW - graph topology KW - network theory (graphs) KW - noisy communications links KW - noisy time-varying graphs KW - performance analysis KW - telecommunication links KW - telecommunication network topology KW - time-varying network topology KW - time-varying systems JF - Advanced Satellite Multimedia Systems Conference (ASMA) CY - Cagliari, Italy ER - TY - CHAP T1 - Digital Satellite Communications Y1 - 2007 A1 - A. A. Rontogiannis A1 - Marcos Álvarez-Díaz A1 - M. Casadei A1 - V. Dalakas A1 - A. Duverdier A1 - F. J. González-Serrano A1 - M. Iubatti A1 - T. Javornik A1 - L. Lapierre A1 - Neri, Massimo A1 - P. Salmi PB - Springer CY - New York ER - TY - CONF T1 - Aeronautical Channel Model for Broadband L-Band Satellite Communication T2 - AIAA International Communications Satellite Systems Conference (ICSSC) Y1 - 2005 A1 - Madhavendra Richharia A1 - Naveen Kaluvala A1 - Panos Fines A1 - Marcos Álvarez-Díaz A1 - Axel Jahn KW - Digital Communications KW - L-Band KW - satellite communications JF - AIAA International Communications Satellite Systems Conference (ICSSC) CY - Rome, Italy ER - TY - CONF T1 - Optimal Data-Hiding Strategies for Games with BER Payoffs T2 - International Workshop on Digital Watermarking (IWDW) Y1 - 2003 A1 - Pedro Comesaña A1 - Fernando Pérez-González A1 - Félix Balado ED - Ton Kalker ED - Ingemar J. Cox ED - Yong Man Ro KW - data-hiding KW - watermarking JF - International Workshop on Digital Watermarking (IWDW) T3 - Lecture Notes in Computer Science PB - Springer-Verlag Heidelberg VL - 2939 / 2004 ER - TY - JOUR T1 - Improving the Performance of Spatial Watermarking of Images Using Channel Coding JF - Signal Processing Y1 - 2000 A1 - Juan R. Hernández A1 - José M. Rodríguez A1 - Fernando Pérez-González KW - data-hiding KW - watermarking VL - 80 ER - TY - CONF T1 - Coding and Synchronization: A Boost and a Bottleneck for the Development of Image Watermarking T2 - COST #254 Int. Workshop on Intelligent Communications Y1 - 1998 A1 - Juan R. Hernández A1 - Fernando Pérez-González A1 - José M. Rodríguez KW - data-hiding KW - watermarking JF - COST #254 Int. Workshop on Intelligent Communications PB - SSGRR CY - L'Aquila, Italy ER - TY - CONF T1 - The Impact of Channel Coding on the Performance of Spatial Watermarking for Copyright Protection T2 - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) Y1 - 1998 A1 - Juan R. Hernández A1 - Fernando Pérez-González A1 - José M. Rodríguez KW - data-hiding KW - watermarking JF - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) CY - Seattle, Washington, USA VL - 5 ER - TY - JOUR T1 - Performance Analysis of a 2D-Multipulse Amplitude Modulation Scheme for Data Hiding and Watermarking of Still Images JF - IEEE Journal on Selected Areas in Communications Y1 - 1998 A1 - Juan R. Hernández A1 - Fernando Pérez-González A1 - José M. Rodríguez A1 - Gustavo Nieto KW - data-hiding KW - watermarking VL - 16 ER - TY - CONF T1 - Data Hiding for Copyright Protection of Still Images T2 - Emerging Techniques for Communication Terminals Y1 - 1997 A1 - Juan R. Hernández A1 - Fernando Pérez-González A1 - José M. Rodríguez KW - data-hiding KW - watermarking JF - Emerging Techniques for Communication Terminals PB - ENSEEIHT CY - Tolouse, France ER -