Fabbryccio Cardoso - Academia.edu (original) (raw)

Papers by Fabbryccio Cardoso

RESUMO Investiga-se neste trabalho a aplicação de algoritmos genéticos (AGs) ao problema da otimi... more RESUMO Investiga-se neste trabalho a aplicação de algoritmos genéticos (AGs) ao problema da otimização de filtros não-lineares bidimensionais, baseados em redes neurais, para interpolação de imagens. Aplica-se também os AGs ao problema da decodificação ...

Anais do XXV Simpósio Brasileiro de Telecomunicações, 2007

Resumo-Este trabalho apresenta uma implementação em hardware de um codificador LDPC para um siste... more Resumo-Este trabalho apresenta uma implementação em hardware de um codificador LDPC para um sistema de televisão digital. O codificador implementadoé baseado em uma classe estendida de códigos de repetição e acumulação irregulares, eIRA, com palavra-código de 9792 bits e taxa 3/4. A implementação foi realizada utilizando tecnologias inovadoras de prototipagem rápida para FPGAs, como o System Generator do Design Flow da Xilinx, o qual será brevemente introduzido. Este trabalho inserese em um projeto mais amplo de elaboração de uma tecnologia de modulação inovadora para o Sistema Brasileiro de Televisão Digital (SBTVD).

Anais do XXVI Simpósio Brasileiro de Telecomunicações, 2008

Resumo-Este artigo propõe um algoritmo concorrente para equalização semi-cega no domínio da freqü... more Resumo-Este artigo propõe um algoritmo concorrente para equalização semi-cega no domínio da freqüência para sistemas OFDM. O objetivo é aumentar a vazão dos dados transmitidos sem prejuízo no desempenho do sistema, quando comparado com técnicas convencionais de estimação de canal baseadas em portadoras pilotos. A proposta é aplicar o conceito de equalização concorrente CMA+SDD a um banco de equalizadores no domínio da freqüência (pós FFT). O algoritmo proposto pode ser considerado semi-cego porque utiliza informação de subportadoras pilotos na inicialização, mantendo-se cego durante sua operação. Para suportar a equalização concorrente, o sistema deve prover pilotos apenas no primeiro símbolo de um superquadro, de modo a permitir que o algoritmo se inicialize quando o receptor for ligado ou quando a equalização for perdida. Nos demais símbolos do superquadro as portadoras pilotos são destinadas ao transporte de informação visando o aumento da vazão do sistema. Palavras-Chave-Algoritmo concorrente, Equalização no domínio da freqüência, OFDM.

Anais de XXIX Simpósio Brasileiro de Telecomunicações, 2011

Resumo-Este artigo apresenta uma solução para aumentar a vazão de dados ou o desempenho de BER ve... more Resumo-Este artigo apresenta uma solução para aumentar a vazão de dados ou o desempenho de BER versus S R em sistemas OFDM. O objetivo é realizar esta tarefa empregando um algoritmo de adaptação para os coeficientes do equalizador Pré-FFT, similar à do LMS, porém usando a retro-propagação do gradiente estocástico do erro no domínio da frequência para o domínio do tempo. Essa estratégia possibilita o uso de informações previamente conhecidas sobre a constelação do sinal nas subportadoras, a fim de se minimizar funções de custo como a do CMA e do SDD. Além disso, é proposto um esquema para que os algoritmos CMA e SDD atuem de modo concorrente. Palavras-Chave-Algoritmo de retro-propagação, equalização concorrente, equalização Pré-FFT, OFDM.

In this paper, we identify issues and possible solutions in the key area of large-scale antenna s... more In this paper, we identify issues and possible solutions in the key area of large-scale antenna systems, also know as Massive Multiple Input Multiple Output (MIMO) systems. Additionally, we propose the use of Massive MIMO technology as a means to tackle the uplink mixed-service communication problem. Under the assumption of an available physical narrowband shared channel (PNSCH), the capacity of the MTC network and, in turn, that of the whole system, can be increased by grouping Machine-Type Communication (MTC) devices into clusters and letting each cluster share the same time-frequency physical resource blocks. We study the feasibility of applying sub-optimal linear detection to the problem of detecting a large number of MTC devices sharing the same time-frequency resources at the uplink of a base station (BS) equipped with a large number of antennas, M. In our study, we derive the achievable lower-bound rates for the studied sub-optimal linear detectors and show that the transmitt...

IEEE Access, 2018

This paper evaluates the feasibility of applying massive multiple-input multiple-output (MIMO) to... more This paper evaluates the feasibility of applying massive multiple-input multiple-output (MIMO) to tackle the uplink mixed-service communication problem. Under the assumption of an available physical narrowband shared channel, devised to exclusively consume data traffic from machine type communications (MTC) devices, the capacity (i.e., number of connected devices) of MTC networks and, in turn, that of the whole system, can be increased by clustering such devices and letting each cluster share the same time-frequency physical resource blocks. Following this research line, we study the possibility of employing sub-optimal linear detectors to the problem and present a simple and practical channel estimator that works without the previous knowledge of the large-scale channel coefficients. Our simulation results suggest that the proposed channel estimator performs asymptotically, as well as the MMSE estimator, with respect to the number of antennas and the uplink transmission power. Furthermore, the results also indicate that, as the number of antennas is made progressively larger, the performance of the sub-optimal linear detection methods approaches the perfect interference-cancellation bound. The findings presented in this paper shed light on and motivate for new and exciting research lines toward a better understanding of the use of massive MIMO in MTC networks. INDEX TERMS Large-scale antenna systems, 5G networks, machine type communications, channel estimation, linear detection.

The present paper deals with an OFDM-based uplink within a multiuser MIMO (MU-MIMO) system where ... more The present paper deals with an OFDM-based uplink within a multiuser MIMO (MU-MIMO) system where a massive MIMO approach is employed. In this context, the linear detectors Minimum Mean-Squared Error (MMSE), Zero Forcing (ZF) and Maximum Ratio Combining (MRC) are considered and assessed. This papers includes Bit Error Rate (BER) results for uncoded QPSK/OFDM transmissions through a flat Rayleigh fading channel under the assumption of perfect power control and channel estimation. BER results are obtained through Monte Carlo simulations. Performance results are discussed in detail and we confirm the achievable "massive MIMO" effects, even for a reduced complexity detection technique, when the number of receive antennas at BS is much larger than the number of transmit antennas.

2015 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC), 2015

This paper presents an FPGA implementation of the front-end of a single-carrier coherent optical ... more This paper presents an FPGA implementation of the front-end of a single-carrier coherent optical receiver for optical networks. The receiver is based on a number of spectral-efficient techniques, such as polarization multiplexing and 16-QAM modulation formats. The FPGA implementation was tested with received traces (time series) obtained from optical simulation for scenarios that operate with channel data rates of 112 Gb/s. Primary emphasis is given to the use of powerful high-level design tools and to efficient testing methodology for FPGA implementation.

2015 Information Theory and Applications Workshop (ITA), 2015

Long Term Evolution (LTE), a standard developed by the 3rd Generation Partnership Project (3GPP),... more Long Term Evolution (LTE), a standard developed by the 3rd Generation Partnership Project (3GPP), is currently the 4G mainstream technology, providing technology convergence for this generation of cellular communication systems. LTE networks promise data transmission rates of 100 Mbps in the downlink channel. For this high throughput it needs to optimize the use of network resources. LTE uses scheduling techniques for radio resource allocation based on communication channel conditions. This paper presents a heuristic customizable algorithm for multi-user data scheduling in the LTE downlink channel that can prioritize selected types of services. The proposed scheduling scheme is a modified version of the proportional fairness scheduler that uses Analytic Hierarchy Process (AHP) techniques. This allows to aggregate performance criteria to improve resource allocation based on general traffic conditions and a set of predefined service priorities. The approach for this customization is to assign weights to certain parameters used in the resource allocation process, thus modifying the relative importance of these parameters and creating a hierarchy of criteria. Criteria for different types of data are added through comparison matrices. A comparison matrix quantifies the judgment of the decision maker with respect to the relative importance of different criteria. Thus the scheduler can be made flexible and adaptive to different traffic scenarios. Examples are given where video traffic is prioritized.

2015 IEEE 6th Latin American Symposium on Circuits & Systems (LASCAS), 2015

This paper presents the hardware architecture and the corresponding implementation details of a c... more This paper presents the hardware architecture and the corresponding implementation details of a configurable and optimized FPGA-based time-domain frequency shifter with application to Long Term Evolution (LTE) and Long Term Evolution-Advanced (LTE-A) systems. The architecture is mainly based on a customized Numerically Controlled Oscillator (NCO) that is used for generating complex exponentials employing only adders, a Look-Up Table (LUT) and plain logic resources.

International Conference on Acoustics, Speech, and Signal Processing, 2000

This paper proposes an image interpolation model based on a multiresolution scheme. The method us... more This paper proposes an image interpolation model based on a multiresolution scheme. The method uses two different known image resolutions to establish a mapping between them. The mapping is then used to extrapolate the unknown resolution to produce an expanded image with increased definition and with a mean square reconstruction error lower than for the conventional methods. In other words,

2015 International Workshop on Telecommunications (IWT), 2015

Long Term Evolution (LTE) is the standard developed by the 3rd Generation Partnership Project (3G... more Long Term Evolution (LTE) is the standard developed by the 3rd Generation Partnership Project (3GPP) to address the ITU's 4G requirements. For the first time, we have technology convergence in a generation of cellular communication systems. LTE promises data transmission of about 100 Mbps and its advanced version (LTE-A) goes even further with more than 1 Gbps in the downlink channel. Such very high data rates will only be achievable with appropriate network resource optimizations. Accordingly, this paper presents a flexible and adaptive scheme of multi-user scheduling considering data traffic prioritization in the LTE downlink channel. The proposed scheduling algorithm uses Proportional Fairness and Analytic Hierarchy Process (AHP) that allows to aggregate performance criteria and to improve resource allocation for users based on the general traffic.

2015 International Workshop on Telecommunications (IWT), 2015

ABSTRACT

Journal of the Brazilian Computer Society

2014 International Conference on ReConFigurable Computing and FPGAs (ReConFig14), 2014

This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (... more This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (ZC) complex sequences in the frequency domain. It is a hardware-efficient and accurate architecture for computing ZC sequences in realtime. The architecture is mainly based on the CORDIC algorithm for computing complex exponentials using only shift and add operations. Due to transformations applied to the Zadoff-Chu equation it is possible to eliminate the use of multipliers with non-constant terms. This hardware architecture is employed by the Physical Random Access Channel (PRACH) in LTE and LTE-A systems during the reception and detection of random access preambles. Its main advantage is that it eliminates the need for storing a large number of long complex ZC sequences. Simulation results show that the proposed architecture is accurate, efficient and renders the resulting PRACH receiver fully compliant with 3GPP's detection requirements.

2014 IEEE Latin-America Conference on Communications (LATINCOM), 2014

This paper presents a case study of the integration of the Long Term Evolution (LTE) physical lay... more This paper presents a case study of the integration of the Long Term Evolution (LTE) physical layer into the radio protocol subsystem of a macrocell base station. We conduct tests in the laboratory using a modular experimental setup aimed at validating this protocol stack integration. Measurements and analysis are carried out with the aid of Wireshark, a well-known protocol analyzer tool. This choice allows the inspection of data packets at the application program interface between PHY and MAC subsystems. Our results suggest that the LTE protocol stack can operate synchronously, thus supporting message sequences conveyed within both random access and radio-resource-control connection procedures. The proposed experimental setup and test methodology make it possible to validate the control plane operation of the protocol stack without the need of a core network interface.

2009 Fifth International Conference on Wireless and Mobile Communications, 2009

This paper proposes a semi-blind algorithm for frequency-domain (post-FFT) soft-decision concurre... more This paper proposes a semi-blind algorithm for frequency-domain (post-FFT) soft-decision concurrent equalization in OFDM systems. The objective is to improve system performance by increasing data throughput or decreasing power requirements, when compared with pilot based conventional channel estimation techniques. The Constant Modulus Algorithm and the Soft Decision-Directed technique were concurrently employed to adjust the coefficients of a post-FFT equalizer bank. The algorithm works in a semi-blind mode because it uses channel information, obtained from pilot subcarriers, to initialize and to supervise the equalizer bank when pilots are present, otherwise remaining blind in the equalization process. To support such a concurrent equalization, the system should provide pilot subcarriers only in the first symbol of each OFDM super-frame, allowing algorithm initialization when the receiver is turned on. In the remaining super-frame symbols, pilot subcarriers can be suppressed to increase the overall system throughput.

2014 Euro Med Telco Conference (EMTC), 2014

This paper deals with architectural and practical design aspects to estimate the frame misalignme... more This paper deals with architectural and practical design aspects to estimate the frame misalignment of LTE uplink transmissions on field programmable gate array devices. Timing adjustments are calculated and delivered to the User Equipment in conformance to Long Term Evolution specifications. Performance results as well as amount of resources necessary for the implementation of the proposed method are assessed. Moreover, the issue regarding the resulting digital circuitry is also considered. Results indicate that the proposed architecture is capable of calculating timing adjustments for SNR as low as -10dB with no constraints on the number of users multiplexed within a time transmission interval.

2014 International Telecommunications Symposium (ITS), 2014

This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (... more This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (ZC) complex sequences in the Frequency Domain (FD). It is a hardware-efficient and accurate architecture for computing ZC sequences in real-time. The architecture is mainly based on the CORDIC algorithm for computing complex exponentials using only shift and add operations. Due to transformations applied to the Zadoff-Chu equation it is possible to eliminate the use of multipliers with non-constant terms. This hardware architecture is employed by the Physical Random Access Channel (PRACH) in LTE and LTE-A systems during the reception and detection of random access preambles. Its main advantage is that it eliminates the need for storing a large number of long complex ZC sequences.

Anais do XXV Simpósio Brasileiro de Telecomunicações, 2007

Anais do XXVI Simpósio Brasileiro de Telecomunicações, 2008

Anais de XXIX Simpósio Brasileiro de Telecomunicações, 2011

IEEE Access, 2018

2015 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference (IMOC), 2015

2015 Information Theory and Applications Workshop (ITA), 2015

2015 IEEE 6th Latin American Symposium on Circuits & Systems (LASCAS), 2015

International Conference on Acoustics, Speech, and Signal Processing, 2000

2015 International Workshop on Telecommunications (IWT), 2015

ABSTRACT

Journal of the Brazilian Computer Society

2014 International Conference on ReConFigurable Computing and FPGAs (ReConFig14), 2014

2014 IEEE Latin-America Conference on Communications (LATINCOM), 2014

2009 Fifth International Conference on Wireless and Mobile Communications, 2009

2014 Euro Med Telco Conference (EMTC), 2014

2014 International Telecommunications Symposium (ITS), 2014

This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (... more This paper presents a configurable and optimized hardware architecture for computing Zadoff-Chu (ZC) complex sequences in the Frequency Domain (FD). It is a hardware-efficient and accurate architecture for computing ZC sequences in real-time. The architecture is mainly based on the CORDIC algorithm for computing complex exponentials using only shift and add operations. Due to transformations applied to the Zadoff-Chu equation it is possible to eliminate the use of multipliers with non-constant terms. This hardware architecture is employed by the Physical Random Access Channel (PRACH) in LTE and LTE-A systems during the reception and detection of random access preambles. Its main advantage is that it eliminates the need for storing a large number of long complex ZC sequences.