http://repositorio.ufc.br/handle/riufc/489 2026-04-14T14:32:14Z 2026-04-14T14:32:14Z Freitas Júnior, Walter da Cruz Cavalcanti, Francisco Rodrigo Porto Lopes, Renato da Rocha http://repositorio.ufc.br/handle/riufc/71043 2023-03-01T18:04:16Z 2006-01-01T00:00:00Z

Título: Hybrid MIMO transceiver scheme with antenna allocation and partial CSI at transmitter side Autor(es): Freitas Júnior, Walter da Cruz; Cavalcanti, Francisco Rodrigo Porto; Lopes, Renato da Rocha Abstract: 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 gains at the same time. Since the spatial multiplexing branches have no protection, they are more susceptible to the fading effect becoming the bottleneck in the performance of the whole transceiver. In this paper, we propose a solution to this bottleneck in the hybrid MIMO transceiver scheme using a partial channel state information at the transmitter side. The idea is to perform an antenna allocation. Thus, the most powerful subchannels are allocated to the most susceptible layers (spatial multiplexing branches). Through this solution we decrease the performance imbalance between the two layers of the HMTS G3+1, increasing the whole transceiver performance with low complexity feedback requirements. Tipo: Artigo de Evento

2006-01-01T00:00:00Z Silva, Adeildo Sombra da Mota, João César Moura Lucena, Antônio Macílio Pereira de http://repositorio.ufc.br/handle/riufc/70738 2023-02-09T17:40:16Z 2011-01-01T00:00:00Z

Título: Amostragem em banda-passante e conversão de frequência em um demodulador OQPSK completamente digital Autor(es): Silva, Adeildo Sombra da; Mota, João César Moura; Lucena, Antônio Macílio Pereira de Abstract: This article presents a method for simultaneously sampling and down convert the intermediate frequency signal to the baseband signal in an all-digital OQPSK demodulator developed for space communications. The proposed system is described, the signals are analyzed at various stages of the converter and showed the statistics of the noises at the converter outputs. Some computational simulation results are presented that evaluate the compromise of the performance of the system caused by the use of the converter. Tipo: Artigo de Evento

2011-01-01T00:00:00Z Ribeiro, Lucas Nogueira Almeida, André Lima Férrer de Mota, João César Moura http://repositorio.ufc.br/handle/riufc/70737 2023-02-09T17:39:43Z 2015-01-01T00:00:00Z

Título: Identification of separable systems using trilinear filtering Autor(es): Ribeiro, Lucas Nogueira; Almeida, André Lima Férrer de; Mota, João César Moura Abstract: Linear filtering methods are well known and have been successfully applied in system identification and equalization problems. However, they become unpractical when the number of parameters to estimate is very large. The recently proposed assumption of system separability allows the development of computationally efficient alternatives to classic adaptive methods in this scenario. In this work, we show that system separability calls for multilinear system representation and filtering. Based on this parallel, the proposed filtering framework consists of a trilinear extension of the classical Wiener-Hopf (WH) solution that exploits the separability property to solve the supervised identification problem. Our numerical results shows the proposed algorithm can provide a better accuracy than the classical WH solution which ignores the multilinear system representation. Tipo: Artigo de Evento

2015-01-01T00:00:00Z Ribeiro, Lucas Nogueira Schwarz, Stefan Rupp, Markus Almeida, André Lima Férrer de Mota, João César Moura http://repositorio.ufc.br/handle/riufc/70736 2023-02-09T17:39:15Z 2017-01-01T00:00:00Z

Título: A low-complexity equalizer for massive MIMO systems based on array separability Autor(es): Ribeiro, Lucas Nogueira; Schwarz, Stefan; Rupp, Markus; Almeida, André Lima Férrer de; Mota, João César Moura Abstract: In this paper, we propose a low-complexity equalizer for multiple-input multiple-output systems with large receive antenna arrays. The computational complexity reduction is achieved by exploiting array separability on a geometric channel model. This property suggests a two-stage receive processing, consisting of (i) sub-array beamforming and (ii) low-dimension minimum mean square error (MMSE) equalization. Simulations indicate that the proposed method outperforms the classical MMSE filter in terms of complexity provided that the number of channel scatterers and the sub-arrays dimensions are not excessively large. Tipo: Artigo de Evento

2017-01-01T00:00:00Z