The Experts below are selected from a list of 18315 Experts worldwide ranked by ideXlab platform
Rui Dinis - One of the best experts on this subject based on the ideXlab platform.
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VTC-Fall - On the Detection of MIMO Signals with Strong Nonlinear Distortion Effects
2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall), 2019Co-Authors: Joao Felix, Joao Guerreiro, Rui DinisAbstract:The pre-processing required at the transmitter side by many MIMO (Multi-Input, Multi-Output) schemes can lead to signals with substantial envelope fluctuations, making them very prone to Nonlinear Distortion effects. These Nonlinear Distortion effects can lead to significant performance degradation and signals with high irreducible error floor when conventional receivers are employed. However, the Nonlinear Distortion has information on the transmitted signals than can be employed to improve the performance, provided that an optimum receiver is employed. Nevertheless, the huge complexity of optimum receivers precludes its use in most practical scenarios. In this paper we consider MIMO schemes with strong Nonlinear effects at the transmitter side and we propose an iterative receiver that is able to cope with Nonlinear effects, allowing excellent performance even with strong Nonlinear Distortion effects. In fact, our results show that MIMO schemes with strong Nonlinear effects can even perform better than linear MIMO system.
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Analytical evaluation of Nonlinear Distortion effects on multicarrier signals
Analytical Evaluation of Nonlinear Distortion Effects on Multicarrier Signals, 2015Co-Authors: Teresa Araújo, Rui DinisAbstract:Due to their ability to support reliable high quality of service as well as spectral and power efficiency, multicarrier modulation systems have found increasing use in modern communications services. However, one of the main drawbacks of these systems is their vulnerability to Nonlinear Distortion effects. Analytical Evaluation of Nonlinear Distortion Effects on Multicarrier Signals details a unified approach to well-known analytical results on memoryless Nonlinearities that takes advantage of the Gaussian behavior of multicarrier signals.Sharing new insights into the behavior of Nonlinearly distorted multicarrier signals, the book begins with a review of the fundamental principles of multicarrier transmission and multicarrier-based systems. Next, it covers well-known results on Nonlinear Distortion of Gaussian signals and examines the accuracy of the use of Gaussian approximation for evaluating Nonlinear effects. It also considers the performance of various multicarrier-based systems in the presence of different types of Nonlinear devices. Describes general clipping and filtering techniques to reduce the envelope fluctuations of multicarrier signals Analyzes quantization effects caused by the numerical accuracy required in the DFT computations Discusses quantization requirements of analog-to-digital converters Redefines loading techniques to take into account Nonlinear Distortion issues on adaptive multicarrier systems Examines the impact of Nonlinear signal processing techniques for reducing the envelope fluctuations of OFDMA signals Presents performance results for all the discussed applications The book covers the essential principles of multicarrier modulations, including OFDM modulations and other multicarrier schemes. It describes multicarrier modulation systems that will be used in next-generation communications systems and also provides new insight into the behavior of Nonlinearly distorted multicarrier signals.Illustrating the application of the Nonlinear Distortion analysis techniques presented, the book provides you with a wide range of analytical tools to assess the effects of Nonlinearities on the performance of multicarrier-based schemes.
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Optimum and Sub-Optimum Receivers for OFDM Signals with Strong Nonlinear Distortion Effects
IEEE Transactions on Communications, 2013Co-Authors: Joao Guerreiro, Rui Dinis, Paulo MontezumaAbstract:In this paper we consider the optimum detection of OFDM (Orthogonal Frequency Division Multiplexing) signals with strong Nonlinear Distortion effects. It is shown that the optimum performance with strong Nonlinear Distortion effects is not as bad as one might expect and can even be better than the performance with conventional, linear transmitters. To achieve these excellent performances we should employ receivers able to take advantage of the information associated to transmitted data symbols that is inherent to the Nonlinear Distortion component, in opposition to traditional OFDM implementations where Nonlinear Distortion effects are regarded as an undesirable noise-like component. We study the achievable gains of the optimum receiver both analytically and by simulation. Since the complexity of optimum receivers is extremely high when we have Nonlinear Distortion effects, even for OFDM signals with a small number of subcarriers, we propose several sub-optimum receivers and evaluate their performance. Our sub-optimal receivers allow remarkable performance improvements, being able to reduce significantly the gap between the optimum performance and the performance of typical OFDM receivers.
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Loading techniques for OFDM systems with Nonlinear Distortion effects
Transactions on Emerging Telecommunications Technologies, 2011Co-Authors: Teresa Araújo, Rui DinisAbstract:In this paper, we study the impact of Nonlinear Distortion effects on adaptive orthogonal frequency division multiplexing systems. An analytical statistical characterisation of the transmitted signals, which is obtained by taking advantage of the Gaussian-like nature of the orthogonal frequency division multiplexing signals when the number of subcarriers is high, is included. This statistical characterisation is used to evaluate loading algorithms in the presence of strong Nonlinear Distortion effects and to redefine loading algorithms taking into account Nonlinear Distortion issues. Copyright © 2011 John Wiley & Sons, Ltd.
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Loading techniques for OFDM systems with Nonlinear Distortion effects
2009 6th International Symposium on Wireless Communication Systems, 2009Co-Authors: Teresa Araújo, Rui DinisAbstract:In this paper we study the impact of Nonlinear Distortion effects on adaptive OFDM (Orthogonal Frequency Division Multiplexing) systems. An analytical statistical characterization of the transmitted signals is included which is obtained taking advantage of the Gaussian-like nature of the OFDM signals when the number of subcarriers is high. This statistical characterization is used to evaluate loading algorithms in the presence of strong Nonlinear Distortion effects and to redefine loading algorithms taking into account Nonlinear Distortion issues.
Harald Haas - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Distortion in spad based optical ofdm systems
Global Communications Conference, 2015Co-Authors: Majid Safari, Robert Henderson, Harald HaasAbstract:In this paper, an optical orthogonal frequency di- vision multiplexing (OFDM) system based on a single-photon avalanche diode (SPAD) receiver with a Nonlinear Distortion is presented. In this study, the methods to calculate the output of passive and active quenching SPAD arrays are given. Nonlinear performances of these two SPAD arrays and their effects on bit-error ratio performances of SPAD-based DC-biased optical OFDM and asymmetrically clipped optical OFDM are simulated in the absence of background light. In the simulation, the maxi- mum optical irradiance and the low error area are given as the metrics of the Nonlinear Distortion. The effects of the Nonlinear Distortion are discussed for different modulation schemes, symbol rates and spectral efficiencies.
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GLOBECOM Workshops - Nonlinear Distortion in SPAD-Based Optical OFDM Systems
2015 IEEE Globecom Workshops (GC Wkshps), 2015Co-Authors: Majid Safari, Robert Henderson, Harald HaasAbstract:In this paper, an optical orthogonal frequency di- vision multiplexing (OFDM) system based on a single-photon avalanche diode (SPAD) receiver with a Nonlinear Distortion is presented. In this study, the methods to calculate the output of passive and active quenching SPAD arrays are given. Nonlinear performances of these two SPAD arrays and their effects on bit-error ratio performances of SPAD-based DC-biased optical OFDM and asymmetrically clipped optical OFDM are simulated in the absence of background light. In the simulation, the maxi- mum optical irradiance and the low error area are given as the metrics of the Nonlinear Distortion. The effects of the Nonlinear Distortion are discussed for different modulation schemes, symbol rates and spectral efficiencies.
Joao Guerreiro - One of the best experts on this subject based on the ideXlab platform.
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VTC-Fall - On the Detection of MIMO Signals with Strong Nonlinear Distortion Effects
2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall), 2019Co-Authors: Joao Felix, Joao Guerreiro, Rui DinisAbstract:The pre-processing required at the transmitter side by many MIMO (Multi-Input, Multi-Output) schemes can lead to signals with substantial envelope fluctuations, making them very prone to Nonlinear Distortion effects. These Nonlinear Distortion effects can lead to significant performance degradation and signals with high irreducible error floor when conventional receivers are employed. However, the Nonlinear Distortion has information on the transmitted signals than can be employed to improve the performance, provided that an optimum receiver is employed. Nevertheless, the huge complexity of optimum receivers precludes its use in most practical scenarios. In this paper we consider MIMO schemes with strong Nonlinear effects at the transmitter side and we propose an iterative receiver that is able to cope with Nonlinear effects, allowing excellent performance even with strong Nonlinear Distortion effects. In fact, our results show that MIMO schemes with strong Nonlinear effects can even perform better than linear MIMO system.
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Optimum and Sub-Optimum Receivers for OFDM Signals with Strong Nonlinear Distortion Effects
IEEE Transactions on Communications, 2013Co-Authors: Joao Guerreiro, Rui Dinis, Paulo MontezumaAbstract:In this paper we consider the optimum detection of OFDM (Orthogonal Frequency Division Multiplexing) signals with strong Nonlinear Distortion effects. It is shown that the optimum performance with strong Nonlinear Distortion effects is not as bad as one might expect and can even be better than the performance with conventional, linear transmitters. To achieve these excellent performances we should employ receivers able to take advantage of the information associated to transmitted data symbols that is inherent to the Nonlinear Distortion component, in opposition to traditional OFDM implementations where Nonlinear Distortion effects are regarded as an undesirable noise-like component. We study the achievable gains of the optimum receiver both analytically and by simulation. Since the complexity of optimum receivers is extremely high when we have Nonlinear Distortion effects, even for OFDM signals with a small number of subcarriers, we propose several sub-optimum receivers and evaluate their performance. Our sub-optimal receivers allow remarkable performance improvements, being able to reduce significantly the gap between the optimum performance and the performance of typical OFDM receivers.
Majid Safari - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Distortion in spad based optical ofdm systems
Global Communications Conference, 2015Co-Authors: Majid Safari, Robert Henderson, Harald HaasAbstract:In this paper, an optical orthogonal frequency di- vision multiplexing (OFDM) system based on a single-photon avalanche diode (SPAD) receiver with a Nonlinear Distortion is presented. In this study, the methods to calculate the output of passive and active quenching SPAD arrays are given. Nonlinear performances of these two SPAD arrays and their effects on bit-error ratio performances of SPAD-based DC-biased optical OFDM and asymmetrically clipped optical OFDM are simulated in the absence of background light. In the simulation, the maxi- mum optical irradiance and the low error area are given as the metrics of the Nonlinear Distortion. The effects of the Nonlinear Distortion are discussed for different modulation schemes, symbol rates and spectral efficiencies.
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GLOBECOM Workshops - Nonlinear Distortion in SPAD-Based Optical OFDM Systems
2015 IEEE Globecom Workshops (GC Wkshps), 2015Co-Authors: Majid Safari, Robert Henderson, Harald HaasAbstract:In this paper, an optical orthogonal frequency di- vision multiplexing (OFDM) system based on a single-photon avalanche diode (SPAD) receiver with a Nonlinear Distortion is presented. In this study, the methods to calculate the output of passive and active quenching SPAD arrays are given. Nonlinear performances of these two SPAD arrays and their effects on bit-error ratio performances of SPAD-based DC-biased optical OFDM and asymmetrically clipped optical OFDM are simulated in the absence of background light. In the simulation, the maxi- mum optical irradiance and the low error area are given as the metrics of the Nonlinear Distortion. The effects of the Nonlinear Distortion are discussed for different modulation schemes, symbol rates and spectral efficiencies.
Paulo Montezuma - One of the best experts on this subject based on the ideXlab platform.
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Optimum and Sub-Optimum Receivers for OFDM Signals with Strong Nonlinear Distortion Effects
IEEE Transactions on Communications, 2013Co-Authors: Joao Guerreiro, Rui Dinis, Paulo MontezumaAbstract:In this paper we consider the optimum detection of OFDM (Orthogonal Frequency Division Multiplexing) signals with strong Nonlinear Distortion effects. It is shown that the optimum performance with strong Nonlinear Distortion effects is not as bad as one might expect and can even be better than the performance with conventional, linear transmitters. To achieve these excellent performances we should employ receivers able to take advantage of the information associated to transmitted data symbols that is inherent to the Nonlinear Distortion component, in opposition to traditional OFDM implementations where Nonlinear Distortion effects are regarded as an undesirable noise-like component. We study the achievable gains of the optimum receiver both analytically and by simulation. Since the complexity of optimum receivers is extremely high when we have Nonlinear Distortion effects, even for OFDM signals with a small number of subcarriers, we propose several sub-optimum receivers and evaluate their performance. Our sub-optimal receivers allow remarkable performance improvements, being able to reduce significantly the gap between the optimum performance and the performance of typical OFDM receivers.
