Erico Lopes - Academia.edu (original) (raw)

Papers by Erico Lopes

Research paper thumbnail of Discrete MMSE Precoding for Multiuser MIMO Systems with PSK Modulation

ArXiv, 2021

We propose an optimal MMSE precoding technique using quantized signals with constant envelope. Un... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope. Unlike the existing MMSE design that relies on 1-bit resolution, the proposed approach employs uniform phase quantization and the bounding step in the branch-and-bound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Moreover, unlike prior studies, we propose three different soft detection methods and an iterative detection and decoding scheme that allow the utilization of channel coding in conjunction with low-resolution precoding. Besides an exact approach for computing the extrinsic information, we propose two approximations with reduced computational complexity. Numerical simulations show that utilizing the MMSE criterion instead of the established maximum-minimum distance to the decision threshold yields a lower bit-error-rate in many scenarios. Furthermore, when using the MMSE cr...

Research paper thumbnail of Multiuser MIMO Systems with Discrete Precoding and Adjusted Soft Receiver Design with PSK Modulation

ArXiv, 2020

Low-resolution precoding techniques gained considerable attention in the wireless communications ... more Low-resolution precoding techniques gained considerable attention in the wireless communications area recently. Unlike prior studies, the proposed work considers a coded transmission with a soft detection process. Based on the assumption that the distortion brought by the discrete precoding is Gaussian distributed, different approaches about the computation of effective log-likelihood-ratios are presented in the study. Numerical results based on PSK modulation and an LDPC block code indicate a superior performance as compared to state-of-the-art system designs in terms of bit-error-rate.

Research paper thumbnail of Minimum Symbol Error Probability Low-Resolution Precoding for MU-MIMO Systems With PSK Modulation

ArXiv, 2021

We propose an optimal low-resolution precoding technique that minimizes the symbol error probabil... more We propose an optimal low-resolution precoding technique that minimizes the symbol error probability of the users. Unlike existing approaches that rely on QPSK modulation, for the derivation of the minimum symbol error probability objective function the current approach allows for any PSK modulation order. Moreover, the proposed method solves the corresponding discrete optimization problem optimally via a sophisticated branch-and-bound method. Moreover, we propose different approaches based on the greedy search method to compute practical solutions. Numerical simulations confirm the superiority of the proposed minimum symbol error probability criteria in terms of symbol error rate when compared with the established MMDDT and MMSE approaches.

Research paper thumbnail of Optimal and Suboptimal MMSE Precoding for Multiuser MIMO Systems Using Constant Envelope Signals with Phase Quantization at the Transmitter and PSK

We propose an optimal MMSE precoding technique using quantized signals with constant envelope and... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope and PSK modulation. Unlike the existing MMSE design for 1-bit resolution, the proposed method employs uniform phase quantization and the bounding step in the branch-andbound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Numerical simulations show that using the MMSE criterion instead of the established maximum distance to decision threshold yields a lower BER in many scenarios and a smaller average number of bound evaluations for low and medium SNR.

Research paper thumbnail of Optimal and Suboptimal Mmse Precoding for Multiuser Mimo Systems Using Constant Envelope Signals with Phase Quantization at the Transmitter and PSK Modulation

We propose an optimal MMSE precoding technique using quantized signals with constant envelope and... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope and PSK modulation. Unlike the existing MMSE design for 1-bit resolution, the proposed method employs uniform phase quantization and the bounding step in the branch-andbound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Numerical simulations show that using the MMSE criterion instead of the established maximum distance to decision threshold yields a lower BER in many scenarios and a smaller average number of bound evaluations for low and medium SNR.

Research paper thumbnail of Iterative Detection and Decoding for Multiuser MIMO Systems with Low Resolution Precoding and PSK Modulation

2021 IEEE Statistical Signal Processing Workshop (SSP)

Low-resolution precoding techniques have gained considerable attention in the wireless communicat... more Low-resolution precoding techniques have gained considerable attention in the wireless communications area recently. Vital but hardly discussed in literature, discrete precoding in conjunction with channel coding is the subject of this study. Unlike prior studies, we propose three different soft detection methods and an iterative detection and decoding scheme that allow the utilization of channel coding in conjunction with low-resolution precoding. Besides an exact approach for computing the extrinsic information, we propose two approximations with reduced computational complexity. Numerical results based on PSK modulation and an LDPC block code indicate a superior performance as compared to the system design based on the common AWGN channel model in terms of bit-error-rate.

Research paper thumbnail of Discrete Precoding and Adjusted Detection for Multiuser Mimo Systems with PSK Modulation

Research paper thumbnail of Estudo, Simulação e Construção De Filtros Para Faixa De Wi-Fi

Research paper thumbnail of Optimal Precoding for Multiuser MIMO Systems With Phase Quantization and PSK Modulation via Branch-and-Bound

IEEE Wireless Communications Letters

MIMO systems are considered as most promising for wireless communications. However, with an incre... more MIMO systems are considered as most promising for wireless communications. However, with an increasing number of radio front ends the corresponding energy consumption and costs become an issue, which can be relieved by the utilization of low-resolution quantizers. In this study we propose an optimal precoding algorithm constrained to constant envelope signals and phase quantization that maximizes the minimum distance to the decision threshold at the receivers using a branch-andbound strategy. The proposed algorithm is superior to the existing methods in terms of bit error rate. Numerical results show that the proposed approach has significantly lower complexity than exhaustive search.

Research paper thumbnail of Discrete MMSE Precoding for Multiuser MIMO Systems with PSK Modulation

ArXiv, 2021

We propose an optimal MMSE precoding technique using quantized signals with constant envelope. Un... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope. Unlike the existing MMSE design that relies on 1-bit resolution, the proposed approach employs uniform phase quantization and the bounding step in the branch-and-bound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Moreover, unlike prior studies, we propose three different soft detection methods and an iterative detection and decoding scheme that allow the utilization of channel coding in conjunction with low-resolution precoding. Besides an exact approach for computing the extrinsic information, we propose two approximations with reduced computational complexity. Numerical simulations show that utilizing the MMSE criterion instead of the established maximum-minimum distance to the decision threshold yields a lower bit-error-rate in many scenarios. Furthermore, when using the MMSE cr...

Research paper thumbnail of Multiuser MIMO Systems with Discrete Precoding and Adjusted Soft Receiver Design with PSK Modulation

ArXiv, 2020

Low-resolution precoding techniques gained considerable attention in the wireless communications ... more Low-resolution precoding techniques gained considerable attention in the wireless communications area recently. Unlike prior studies, the proposed work considers a coded transmission with a soft detection process. Based on the assumption that the distortion brought by the discrete precoding is Gaussian distributed, different approaches about the computation of effective log-likelihood-ratios are presented in the study. Numerical results based on PSK modulation and an LDPC block code indicate a superior performance as compared to state-of-the-art system designs in terms of bit-error-rate.

Research paper thumbnail of Minimum Symbol Error Probability Low-Resolution Precoding for MU-MIMO Systems With PSK Modulation

ArXiv, 2021

We propose an optimal low-resolution precoding technique that minimizes the symbol error probabil... more We propose an optimal low-resolution precoding technique that minimizes the symbol error probability of the users. Unlike existing approaches that rely on QPSK modulation, for the derivation of the minimum symbol error probability objective function the current approach allows for any PSK modulation order. Moreover, the proposed method solves the corresponding discrete optimization problem optimally via a sophisticated branch-and-bound method. Moreover, we propose different approaches based on the greedy search method to compute practical solutions. Numerical simulations confirm the superiority of the proposed minimum symbol error probability criteria in terms of symbol error rate when compared with the established MMDDT and MMSE approaches.

Research paper thumbnail of Optimal and Suboptimal MMSE Precoding for Multiuser MIMO Systems Using Constant Envelope Signals with Phase Quantization at the Transmitter and PSK

We propose an optimal MMSE precoding technique using quantized signals with constant envelope and... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope and PSK modulation. Unlike the existing MMSE design for 1-bit resolution, the proposed method employs uniform phase quantization and the bounding step in the branch-andbound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Numerical simulations show that using the MMSE criterion instead of the established maximum distance to decision threshold yields a lower BER in many scenarios and a smaller average number of bound evaluations for low and medium SNR.

Research paper thumbnail of Optimal and Suboptimal Mmse Precoding for Multiuser Mimo Systems Using Constant Envelope Signals with Phase Quantization at the Transmitter and PSK Modulation

We propose an optimal MMSE precoding technique using quantized signals with constant envelope and... more We propose an optimal MMSE precoding technique using quantized signals with constant envelope and PSK modulation. Unlike the existing MMSE design for 1-bit resolution, the proposed method employs uniform phase quantization and the bounding step in the branch-andbound method is different in terms of considering the most restrictive relaxation of the nonconvex problem, which is then utilized for a suboptimal design also. Numerical simulations show that using the MMSE criterion instead of the established maximum distance to decision threshold yields a lower BER in many scenarios and a smaller average number of bound evaluations for low and medium SNR.

Research paper thumbnail of Iterative Detection and Decoding for Multiuser MIMO Systems with Low Resolution Precoding and PSK Modulation

2021 IEEE Statistical Signal Processing Workshop (SSP)

Low-resolution precoding techniques have gained considerable attention in the wireless communicat... more Low-resolution precoding techniques have gained considerable attention in the wireless communications area recently. Vital but hardly discussed in literature, discrete precoding in conjunction with channel coding is the subject of this study. Unlike prior studies, we propose three different soft detection methods and an iterative detection and decoding scheme that allow the utilization of channel coding in conjunction with low-resolution precoding. Besides an exact approach for computing the extrinsic information, we propose two approximations with reduced computational complexity. Numerical results based on PSK modulation and an LDPC block code indicate a superior performance as compared to the system design based on the common AWGN channel model in terms of bit-error-rate.

Research paper thumbnail of Discrete Precoding and Adjusted Detection for Multiuser Mimo Systems with PSK Modulation

Research paper thumbnail of Estudo, Simulação e Construção De Filtros Para Faixa De Wi-Fi

Research paper thumbnail of Optimal Precoding for Multiuser MIMO Systems With Phase Quantization and PSK Modulation via Branch-and-Bound

IEEE Wireless Communications Letters

MIMO systems are considered as most promising for wireless communications. However, with an incre... more MIMO systems are considered as most promising for wireless communications. However, with an increasing number of radio front ends the corresponding energy consumption and costs become an issue, which can be relieved by the utilization of low-resolution quantizers. In this study we propose an optimal precoding algorithm constrained to constant envelope signals and phase quantization that maximizes the minimum distance to the decision threshold at the receivers using a branch-andbound strategy. The proposed algorithm is superior to the existing methods in terms of bit error rate. Numerical results show that the proposed approach has significantly lower complexity than exhaustive search.