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Rio de Janeiro, Brazil

De Marca R.,CETUC PUC Rio | Fettweis G.,TU Dresden
2011 IEEE Online Conference on Green Communications, GreenCom'11 | Year: 2011

It is our honor and pleasure to welcome you to the first all online IEEE Online Conference on Green Communications, September 26-29, 2011. © 2011 IEEE. Source


Song N.,TU Ilmenau | Alokozai W.U.,TU Ilmenau | De Lamare R.C.,CETUC PUC Rio | De Lamare R.C.,University of York | Haardt M.,TU Ilmenau
IEEE Signal Processing Letters | Year: 2014

We propose a reduced-rank beamformer based on the rank-$D$ Joint Iterative Optimization (JIO) of the modified Widely Linear Constrained Minimum Variance (WLCMV) problem for non-circular signals. The novel WLCMV-JIO scheme takes advantage of both the Widely Linear (WL) processing and the reduced-rank concept, outperforming its linear counterpart as well as the full-rank WL beamformer. We develop an augmented recursive least squares algorithm and present an improved structured version with a much more efficient implementation. It is shown that the improved adaptive scheme achieves the best convergence performance among all the considered methods with a low computational complexity. © 1994-2012 IEEE. Source


Penchel R.A.,CETUC PUC Rio | Bergmann J.R.,CETUC PUC Rio | Moreira F.J.S.,Federal University of Minas Gerais
SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference Proceedings | Year: 2011

This work presents an extension of the formulation for the synthesis of dual-reflector antennas with omnidirectional coverage and arbitrary radiation pattern in elevation plane. The body-of-revolution subreflector is generated by a single conic section while the shaped main reflector is generated by a series of local conic sections sequentially consecutively concatenated. As case studies, four representative axis-displaced ellipse (ADE) configurations are synthesized to provide a sectoral coverage in the elevation plane. Two different ray structures are considered: with a real or a virtual main reflector caustic. The GO shaping results are validated using method-of-moments analysis. © 2011 IEEE. Source


De Lamare R.C.,University of York | Sampaio-Neto R.,CETUC PUC Rio | Haardt M.,TU Ilmenau
IEEE Transactions on Signal Processing | Year: 2011

This work proposes a blind adaptive reduced-rank scheme and constrained constant-modulus (CCM) adaptive algorithms for interference suppression in wireless communications systems. The proposed scheme and algorithms are based on a two-stage processing framework that consists of a transformation matrix that performs dimensionality reduction followed by a reduced-rank estimator. The complex structure of the transformation matrix of existing methods motivates the development of a blind adaptive reduced-rank constrained (BARC) scheme along with a low-complexity reduced-rank decomposition. The proposed BARC scheme and a reduced-rank decomposition based on the concept of joint interpolation, switched decimation and reduced-rank estimation subject to a set of constraints are then detailed. The proposed set of constraints ensures that the multipath components of the channel are combined prior to dimensionality reduction. We develop low-complexity joint interpolation and decimation techniques, stochastic gradient, and recursive least squares reduced-rank estimation algorithms. A model-order selection algorithm for adjusting the length of the estimators is devised along with techniques for determining the required number of switching branches to attain a predefined performance. An analysis of the convergence properties and issues of the proposed optimization and algorithms is carried out, and the key features of the optimization problem are discussed. We consider the application of the proposed algorithms to interference suppression in DS-CDMA systems. The results show that the proposed algorithms outperform the best known reduced-rank schemes, while requiring lower complexity. © 2006 IEEE. Source


Healy C.,CETUC PUC Rio | De Lamare R.C.,CETUC PUC Rio
2015 IEEE International Conference on Communication Workshop, ICCW 2015 | Year: 2015

Low-density parity-check (LDPC) codes offer excellent performance at competitive levels of complexity. Short block length LDPC codes avoid the large processing latency incurred by the large block lengths classically considered for this class of codes, making them a potential candidate for next generation wireless communications systems. In this paper, a novel informed dynamic scheduling (IDS) approach for decoding LDPC codes is developed based on the use of the current message reliabilities and the residuals of the potential updates to select the messages passed in the graph during iterative Sum Product decoding. An alternative measure of the iteration of the IDS schemes is also proposed which highlights the high cost of those algorithms in terms of processing complexity and motivates the development of the proposed approach. The proposed Rel.-RBP decoding algorithm offers very fast convergence at reduced complexity and gains in error rate performance when compared to the previous schemes. © 2015 IEEE. Source

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