Renato R. Lopes

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Hybrid multiple-input multiple-output (MIMO) transceiver scheme (HMTS) combines transmit diversity and spatial multiplexing, thus achieving at the same time the two possible spatial gains offered by MIMO channels. In the design of HMTS spatial diversity and spatial multiplexing branches are disposed in parallel in order to achieve diversity and multiplexing(More)
In this paper, we propose an adaptive radio interface scheme for systems that employ multiple antennas. This is in contrast to the adaptive interface of single-antenna systems like in current packet data cellular systems. We propose groups of transmission parameters called Modulation, Coding and Antenna Schemes (MCAS) that are chosen according to the(More)
In this paper we propose low-complexity algorithms for estimating flat, time-varying and spatially correlated MIMO channels. The proposed estimators employ Kalman filters to track the channel in orthogonal space-time block coded systems. After developing a state-space model for spatially correlated MIMO channels, we show that the proposed estimators can be(More)
Crosstalk is one of the main limiting factors in the data rates achievable by digital subscriber line (DSL) systems, and several algorithms have been proposed to mitigate this impairment. In this paper, we compare the capacity of binders under different crosstalk-mitigating techniques. When computing capacity, we also compare two different power(More)
This article reviews some key aspects of two important branches in unsupervised signal processing: blind deconvolution and blind source separation (BSS). It also gives an overview of their potential application in seismic processing, with an emphasis on seismic deconvolution. Finally, it presents illustrative results of the application, on both synthetic(More)
We derive and analyze two modified Kalman channel estimators (KCE) for time-varying, flat, spatially correlated MIMO channels in systems employing orthogonal space-time block codes: the steady-state KCE, which is less complex than the KCE, and the fading memory KCE, which is more robust to model mismatch.
Recent work has shown that, besides providing a conventional stacked section in which reflections are enhanced, the Common-Reflection-Surface (CRS) stacking method may be used to obtain a stacked section mainly composed of diffraction events. Therefore, CRS can be applied to separate reflection and diffraction events in the resulting zero-offset (ZO)(More)
Resumo— Este trabalho analisa o impacto da restrição de alocações discretas de bits na convergência de um algoritmo iterativo para gerenciamento espectral distribuı́do em sistemas DSL. O problema de controle de potência é formulado como um jogo não-cooperativo no qual os usuários otimizam unilateralmente suas alocações de bits e de potência de transmissão(More)
This paper introduces a modified version of the discrete multi–tone transceiver (DMT) to increase the data rate in broadband power-line communications (PLC). Basically, a computational-intelligence technique trained by a second-order optimization method is applied to mitigate the high-power impulse noise, while the DMT copes with the severe intersymbol(More)