The application of linear precoding at the gateway side enables broadband multibeam satellite systems to use more aggressive frequency reuse patterns increasing the overall capacity of future High Throughput Satellites (HTS). However, although some previous works about precoding consider imperfect CSIT (Chanel State Information at the Transmitter) adding some CSI estimation errors, that is not the main cause of CSI degradation. In practice, receivers can only detect and estimate a few coefficients of the CSI vector being the other nullified, replaced by zeros. This introduces errors in the SINR calculation by the gateway that lead to the assignment of Modulation and Coding Schemes (MCS) over the decoding possibilities of the users, increasing the rate of erroneous frames. In this work, the errors in the SINR calculation caused by the nullification of the CSI are analyzing statistically and geographically using a radiation diagram of 245 beams over Europe. Furthermore, a solution based on a link adaptation algorithm with a per user adaptive margin is proposed, helping to achieve the QEF (Quasi-error Free) target of DVB-S2X systems.

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.

%B IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
%C Calgary, Canada
%G eng
%0 Journal Article
%J IEEE Transactions on Signal Processing
%D 2017
%T Learning Power Spectrum Maps from Quantized Power Measurements
%A Daniel Romero
%A Seung-Jun Kim
%A Georgios Giannakis
%A R. López-Valcarce
%K cognitive radio
%K compass
%K compressed sensing
%K spectrum sensing
%K winter
%K wsn
%X 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.

%B IEEE Transactions on Signal Processing
%V 65
%P 2547-2560
%8 05/2017
%G eng
%N 10
%R 10.1109/TSP.2017.2666775
%0 Conference Proceedings
%B 9th EAI International Conference on Wireless and Satellite Systems, WISATS
%D 2017
%T Link Adaptation Algorithms for Dual Polarization Mobile Satellite Systems
%A Anxo Tato
%A Pol Henarejos
%A Carlos Mosquera
%A Ana Pérez-Neira
%X The use of dual polarization in mobile satellite systems is

very promising as a means for increasing the transmission capacity. In this paper a system which uses simultaneously two orthogonal polarizations in order to communicate with the users is studied. The application of MIMO signal processing techniques along with Adaptive Coding and Modulation in the forward link can provide remarkable throughput gains up to 100 % when compared with the single polarization system. The gateway is allowed to vary the MIMO and Modulation and Coding Schemes for each frame. The selection is done by means of a link adaptation algorithm which uses a tunable margin to achieve a predefined target Frame Error Rate.

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.

%B IEEE Trans. Wireless Communications %V 15 %P 8380 - 8393 %8 12/2016 %G eng %N 12 %R 10.1109/TWC.2016.2614495 %0 Conference Paper %B IEEE Int. Conference on Communications (ICC) %D 2015 %T Low Complexity Hybrid Sparse Precoding and Combining in Millimeter Wave MIMO Systems %A Cristian Rusu %A Roi Méndez-Rial %A Nuria González-Prelcic %A Robert W. Heath Jr. %K compass %K mmWave %B IEEE Int. Conference on Communications (ICC) %I IEEE %C London, UK %8 06/2015 %G eng %0 Conference Paper %B Asilomar Conf. on Signals, Systems, and Computers %D 2015 %T Low Resolution Adaptive Compressed Sensing for mmWave MIMO receivers %A C. Rusu %A Nuria González-Prelcic %A R.W. Heath Jr. %K compass %K mmWave %B Asilomar Conf. on Signals, Systems, and Computers %8 November, 2015 %G eng %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 Transactions on Information Forensics and Security %D 2014 %T A Least Squares Approach to the Static Traffic Analysis of High-Latency Anonymous Communication Systems %A Fernando Pérez-González %A Carmela Troncoso %A Simon Oya %B IEEE Transactions on Information Forensics and Security %G eng %R 10.1109/TIFS.2014.2330696 %0 Conference Paper %B European Signal Processing Conference (EUSIPCO) %D 2014 %T Low-Power Active Interference Cancellation for OFDM Spectrum Sculpting %A Schmidt, J.F. %A Daniel Romero %A R. López-Valcarce %XWe 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.

%B European Signal Processing Conference (EUSIPCO)
%8 09/2014
%G eng
%U http://www.eurasip.org/Proceedings/Eusipco/Eusipco2014/HTML/papers/1569912103.pdf
%0 Journal Article
%J EURASIP Journal on Advances in Signal Processing
%D 2013
%T Lattice implementation of adaptive channel shortening in multicarrier transmission over IIR channels
%A E. Ben Salem
%A S. Cherif
%A H. Besbes
%A R. López-Valcarce
%B EURASIP Journal on Advances in Signal Processing
%V 2013:174
%8 11/2013
%G eng
%U http://asp.eurasipjournals.com/content/2013/1/174
%R 10.1186/1687-6180-2013-174
%0 Conference Paper
%B 21st European Signal Processing Conference 2013 (EUSIPCO 2013)
%D 2013
%T Learning Based Link Adaptation in Multiuser MIMO-OFDM
%A Alberto Rico-Alvariño
%A Robert W. Heath Jr.
%K dynacs
%K link adaptation
%K Machine Learning
%K Multiuser MIMO-OFDM
%X 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.

%B 21st European Signal Processing Conference 2013 (EUSIPCO 2013) %C Marrakech, Morocco %G eng %0 Report %D 2013 %T Least Squares Disclosure Attacks: User Profiling for Mix-based Anonymous Communication Systems %A Fernando Pérez-González %A Carmela Troncoso %I University of Vigo %C Vigo %8 01/2013 %G eng %0 Conference Paper %B Asilomar Conference on Signals Systems and Computers %D 2013 %T Link Adaptation in MIMO-OFDM with Practical Impairments %A Alberto Rico-Alvariño %A Robert W. Heath Jr. %K dynacs %K link adaptation %K MIMO-OFDM %B Asilomar Conference on Signals Systems and Computers %G eng %R 10.1109/ACSSC.2013.6810579 %0 Conference Paper %B IEEE International Workshop on Multimedia Signal Processing (MMSP) %D 2013 %T Localization of Forgeries in MPEG-2 Video through GOP Size and DQ analysis %A Daniele Labartino %A Tiziano Bianchi %A Alessia De Rosa %A Marco Fontani %A David Vázquez-Padín %A Alessandro Piva %A Mauro Barni %XThis work addresses forgery localization in MPEG-2 compressed videos. The proposed method is based on the analysis of Double Quantization (DQ) traces in frames that were encoded twice as intra (i.e., I-frames). Employing a state-of-the-art method, such frames are located in the video under analysis by estimating the size of the Group Of Pictures (GOP) that was used in the first compression; then, the DQ analysis is devised for the MPEG-2 encoding scheme and applied to frames that were intra-coded in both the first and second compression. In such a way, regions that were manipulated between the two encodings are detected. Compared to existing methods based on double quantization analysis, the proposed scheme makes forgery localization possible on a wider range of settings.

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