Luis Vieira | UTFPR - UNIVERSIDADE TECNOLOGICA FEDERAL DO PARANÁ (original) (raw)

Papers by Luis Vieira

2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP)

Fast-OFDM based intensity-modulation and directdetection (IM/DD) has been proposed for the deploy... more Fast-OFDM based intensity-modulation and directdetection (IM/DD) has been proposed for the deployment of costefficient optical access networks, due to simple implementation and high spectral efficiency. In this work, the generalized memory polynomial (GMP) is firstly applied to model the nonlinear characteristic of IM/DD Fast-OFDM links, including memory effects. After model validation using measured data of a 10km single mode fiber link, the GMP is used for performance investigations of a combined clipping and digital post-distortion approach to optical Fast-OFDM, considering both 4PAM and 8PAM modulation formats and different number of Fast-OFDM subcarriers. This work firstly reports performance results of optical 8PAM-Fast-OFDM systems using 2PAM-based training signals for digital post-distortion and FFT-based channel estimation. Excellent performance improvements are achieved using the proposed distortion compensation scheme, relative to conventional system implementation.

2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), Jul 20, 2022

IET Optoelectronics, 2019

The version in the Kent Academic Repository may differ from the final published version. Users ar... more The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Resumo-Um estudo do comportamento de sinais de RF para sistemas de comunicação de RFID que operam... more Resumo-Um estudo do comportamento de sinais de RF para sistemas de comunicação de RFID que operam em UHF é apresentado, incluindo resultados experimentais e modelados. É apresentada uma generalização do modelo de radiopropagação Dielectric Canyon envolvendo reflexões no solo e/ou outros objetos. O modelo é comparado com medições feitas na prática com leitor RFID e também com um analisador de espectro. Isso explica os pontos "cegos" em que as tags não são ativadas, mesmo em distâncias próximas. O estudo é importante para aplicações em ambientes onde as tags estão próximas do solo, como por exemplo na agricultura.

ABSTRACT 2010 Future Network & Mobile Summit. Florence, Italy, 16-18 June 2010 The concep... more ABSTRACT 2010 Future Network & Mobile Summit. Florence, Italy, 16-18 June 2010 The concept of virtual MIMO (multiple-input multiple output) has been proposed to tackle the challenges arising from high data rate wireless communications. Connecting a central unit (CU) with remote antenna units (RAUs), Radio over Fibre (RoF) links are an essential part of the virtual MIMO systems. This paper considers the adaptive compensation of the nonlinear distortions introduced by a RoF link and power amplifier (PA) connected in series. For the predistorter, we study the effects of the fixed point calculation to the performance. Our simulation results indicate that a fixed point predistorter with reasonably low word lengths gives almost the same performance as a floating point predistorter. Hence, it is possible to implement a feasible, low cost and energy consumption, fixed point predistorter into a field-programmable gate array (FPGA).

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Analytical and experimental investigations considering indoor wave propagation and antenna divers... more Analytical and experimental investigations considering indoor wave propagation and antenna diversity are presented for passive UHF RFID systems. Modelling results are reported for two-ray and three-ray reflection models, with the effect of floor and ceiling relative permittivity discussed. A novel multi-LOS multi-ray reflection model, considering transmit antenna diversity, is proposed with good results reported. From experiments, a receive diversity scheme shown the best performance in comparison with transmit diversity and no diversity cases. A promising performance improvement in the tag readability is also demonstrated (without antenna diversity) by simply placing an aluminium plate on the floor nearby a commercial tag.

Radio over fibre (RoF), an enabling technology for distribution of wireless broadband service sig... more Radio over fibre (RoF), an enabling technology for distribution of wireless broadband service signals through analogue optical links, suffers from non-linear distortion. Digital predistortion has been demonstrated as an effective approach to overcome the RoF non-linearity. However, questions remain as to how the approach performs close to laser resonance, a region of significant dynamic non-linearity, and how resilient the approach is to changes in input signal and link operating conditions. In this work, the performance of a digital predistortion approach is studied for directly modulated orthogonal frequency-division multiplexing RoF links operating from 2.47 to 3.7 GHz. It extends previous works to higher frequencies, and to higher quadrature amplitude modulation (QAM) levels. In addition, the resilience of the predistortion approach to changes in modulation level of QAM schemes, and average power levels are investigated, and a novel predistortion training approach is proposed and demonstrated. Both memoryless and memory polynomial predistorter models, and a simple off-line least-squares-based identification method, are used, with excellent performance improvements demonstrated up to 3.0 GHz.

2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP)

Fast-OFDM based intensity-modulation and directdetection (IM/DD) has been proposed for the deploy... more Fast-OFDM based intensity-modulation and directdetection (IM/DD) has been proposed for the deployment of costefficient optical access networks, due to simple implementation and high spectral efficiency. In this work, the generalized memory polynomial (GMP) is firstly applied to model the nonlinear characteristic of IM/DD Fast-OFDM links, including memory effects. After model validation using measured data of a 10km single mode fiber link, the GMP is used for performance investigations of a combined clipping and digital post-distortion approach to optical Fast-OFDM, considering both 4PAM and 8PAM modulation formats and different number of Fast-OFDM subcarriers. This work firstly reports performance results of optical 8PAM-Fast-OFDM systems using 2PAM-based training signals for digital post-distortion and FFT-based channel estimation. Excellent performance improvements are achieved using the proposed distortion compensation scheme, relative to conventional system implementation.

2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP), Jul 20, 2022

IET Optoelectronics, 2019

The version in the Kent Academic Repository may differ from the final published version. Users ar... more The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Resumo-Um estudo do comportamento de sinais de RF para sistemas de comunicação de RFID que operam... more Resumo-Um estudo do comportamento de sinais de RF para sistemas de comunicação de RFID que operam em UHF é apresentado, incluindo resultados experimentais e modelados. É apresentada uma generalização do modelo de radiopropagação Dielectric Canyon envolvendo reflexões no solo e/ou outros objetos. O modelo é comparado com medições feitas na prática com leitor RFID e também com um analisador de espectro. Isso explica os pontos "cegos" em que as tags não são ativadas, mesmo em distâncias próximas. O estudo é importante para aplicações em ambientes onde as tags estão próximas do solo, como por exemplo na agricultura.

ABSTRACT 2010 Future Network & Mobile Summit. Florence, Italy, 16-18 June 2010 The concep... more ABSTRACT 2010 Future Network & Mobile Summit. Florence, Italy, 16-18 June 2010 The concept of virtual MIMO (multiple-input multiple output) has been proposed to tackle the challenges arising from high data rate wireless communications. Connecting a central unit (CU) with remote antenna units (RAUs), Radio over Fibre (RoF) links are an essential part of the virtual MIMO systems. This paper considers the adaptive compensation of the nonlinear distortions introduced by a RoF link and power amplifier (PA) connected in series. For the predistorter, we study the effects of the fixed point calculation to the performance. Our simulation results indicate that a fixed point predistorter with reasonably low word lengths gives almost the same performance as a floating point predistorter. Hence, it is possible to implement a feasible, low cost and energy consumption, fixed point predistorter into a field-programmable gate array (FPGA).

Anais de XXXVII Simpósio Brasileiro de Telecomunicações e Processamento de Sinais

Analytical and experimental investigations considering indoor wave propagation and antenna divers... more Analytical and experimental investigations considering indoor wave propagation and antenna diversity are presented for passive UHF RFID systems. Modelling results are reported for two-ray and three-ray reflection models, with the effect of floor and ceiling relative permittivity discussed. A novel multi-LOS multi-ray reflection model, considering transmit antenna diversity, is proposed with good results reported. From experiments, a receive diversity scheme shown the best performance in comparison with transmit diversity and no diversity cases. A promising performance improvement in the tag readability is also demonstrated (without antenna diversity) by simply placing an aluminium plate on the floor nearby a commercial tag.

Radio over fibre (RoF), an enabling technology for distribution of wireless broadband service sig... more Radio over fibre (RoF), an enabling technology for distribution of wireless broadband service signals through analogue optical links, suffers from non-linear distortion. Digital predistortion has been demonstrated as an effective approach to overcome the RoF non-linearity. However, questions remain as to how the approach performs close to laser resonance, a region of significant dynamic non-linearity, and how resilient the approach is to changes in input signal and link operating conditions. In this work, the performance of a digital predistortion approach is studied for directly modulated orthogonal frequency-division multiplexing RoF links operating from 2.47 to 3.7 GHz. It extends previous works to higher frequencies, and to higher quadrature amplitude modulation (QAM) levels. In addition, the resilience of the predistortion approach to changes in modulation level of QAM schemes, and average power levels are investigated, and a novel predistortion training approach is proposed and demonstrated. Both memoryless and memory polynomial predistorter models, and a simple off-line least-squares-based identification method, are used, with excellent performance improvements demonstrated up to 3.0 GHz.