Programa de Pós-graduação em Engenharia Elétrica e da Computação

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Navegando Programa de Pós-graduação em Engenharia Elétrica e da Computação por Assunto "5G"

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    Escalonamento de recursos em redes LTE utilizando processo envelope de tráfego multifractal e curva de serviço mínima
    (Universidade Federal de Goiás, 2018-12-14) Abrahão, Diego Cruz; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Sousa, Marcos Antônio de; Lemos, Rodrigo Pinto; Lima, Marcos Antônio Cardoso de; Cardoso, Kleber Vieira
    In this work, a variation of the MWM (Multifractal Wavelet Model) model is proposed for network traffic flows, in such a way that its parameters are estimated adaptively. Next, it proposes an envelope process of network traffic based on the parameters' adaptive estimation of this model, whose final objective is to provide quality of service (QoS) in real time. The proposed envelope is compared to the main envelopes processes known in the literature, that are based on traffic models, such as: Brownian Motion (Bm), Fractional Brownian Motion (fBm) and Multifractal Brownian Motion (mBm). This work investigates the use of F-OFDM multi-carrier modulation, which is one of the candidates for 5G networks. It is known that the LTE / LTE-A (Long-Term Evolution) network uses Adaptive Modulation and Coding (AMC) technique that have the function of adjusting the modulation order and code rate based on the user's channel state information, in order to achieve a Block Error Rate (BLER) lesser than 10%. In this work, simulations of the LTE downlink are carried out using OFDM and F-OFDM multicarrier modulation, with the objective of mapping the BLER as a function of SNR (Signal-to-Noise Ratio). This mapping is necessary for the network to adjust the modulation and code scheme appropriate to each user. It's also proposed an adaptive algorithm for resource allocation in the LTE/LTE-A downlink, with admission control of the users. This algorithm aims to improve the performance of some network parameters and to guarantee maximum delay, through of following information: backlog, channel condition and user’s traffic behavior. In order to control the admission of users and to estimate the maximum delay of the network, a minimum adaptive service curve of the LTE / LTE-A network is proposed. The proposed algorithm for resource allocation is compared with several scheduling schemes known in the literature through computational simulations of different LTE network scenarios using OFDM and F-OFDM multi-carrier modulation.
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    Localização em ambiente interno usando a rede celular
    (Universidade Federal de Goiás, 2024-07-15) Conceição, Paulo Francisco da; Rocha, Flávio Geraldo Coelho; http://lattes.cnpq.br/5583470206347446; Rocha, Flávio Geraldo Coelho; Vieira, Robson Domingos; Silva, Hugo Vinícius Leão e; Lemos, Rodrigo Pinto; Vieira, Flávio Henrique Teles
    In this work, we propose an approach for Simultaneous Localization and Mapping (SLAM) of the Mobile Station (MS) and scatterers (SCs) in indoor environments using the cellular network. The approach, named IndoorLoc, employs a Single bounce scattering model and treats signals as rays, representing each radio frequency signal originating from multiple paths in an indoor environment where reflections occur at SCs. The estimation of the MS and SCs positions involves three main stages: (1) channel modeling, employing millimeter waves (mmWave) and a massive number of antennas (massive MIMO - mMIMO) arranged in a rectangular array; (2) parameter estimation, using an adaptive method based on Compressed Sensing (CS), the Distributed Compressed Sensing Simultaneous Orthogonal Matching Pursuit (DCS-SOMP); and (3) localization of the MS and SCs, applying geometric methods to detect Line of Sight (LoS) and Non-Line of Sight (NLoS) conditions and specific algorithms for each of these conditions. For IndoorLoc, two geometric methods are proposed: one for LoS conditions, which uses Time of Arrival (ToA) and Angle of Departure (AoD) parameters to determine the direction of propagation and the distance between the BS and the MS, and another for NLoS conditions, which uses ToA, AoD, and Angle of Arrival (AoA) to determine intersection points of the trajectories. This intersection point serves as the initial estimate of the MS localization and acts as an input for further refinement using a Gauss-Newton-based estimator, which minimizes the localization error using a nonlinear model derived from the ToA, AoD, and AoA parameters. The performance of the localization algorithms is evaluated through comparisons of the Root Mean Square Error (RMSE) values with existing methods in the literature. Additionally, simulations were conducted in an indoor environment configured according to the specifications of the 3rd Generation Partnership Project (3GPP). The results demonstrate that the accuracy of IndoorLoc meets the standards of the Federal Communications Commission (FCC) and 3GPP.
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    Propostas de um modelo para o tráfego de redes de comunicações e de funções de janela para o filtro FIR utilizado na tecnologia f-OFDM
    (Universidade Federal de Goiás, 2019-10-31) Silva, Maykon Renan Pereira da; Rocha, Flávio Geraldo Coelho; http://lattes.cnpq.br/5583470206347446; Vieira, Flávio Henrique Teles; Lemos, Rodrigo Pinto; Santos Junior, Josemar Alves dos
    In this work, in order to model the communication network traffic processes, we propose an efficient multifractal model that takes into account less parameters than other models present in the literature. The MEV (Exponential Modeling for Multiplier Variance) model is based on a multiplicative cascade in the wavelet domain capable of synthesizing traffic samples from communications networks that have characteristics such as self-similarity and wide Multifractal Spectrum Width (MSW). For this purpose, in the MEV model, the energy decay of the wavelet coefficients uses a parametric modeling based on an exponential distribution for the variance of multipliers along the cascade stages. The performance of the MEV model in describing the characteristics of network traffic is compared to other models in the literature. For this, real network traffic traces of communication networks are used. In addition, a class of adjustable Nakagami distribution based window functions is proposed for the construction of the windowed-sinc digital filter used by f-OFDM technology. To this end, the filter performance in terms of spectral efficiency and out-of-band emission (OOBE) is compared by analyzing power spectral density (PSD) results. In addition, the FIR filter processing time is verified using different window functions and the bit error rate (BER) in the data transmission process. The results obtained using f-OFDM are compared with those obtained through the unfiltered OFDM technology and also with the FBMC and UFMC technologies. The results obtained show that f-OFDM technology (especially using Nakagami windows) is a candidate for applications in future generations of mobile communication systems, as compared to OFDM technology, it maintains its advantages, for example ISI, while reducing one of its disadvantages, out-of-band emissions (OOBE).
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    Avaliação comparativa de modulações candidatas às redes 5G baseadas em LTE e escalonamento de recursos considerando fila e qualidade de canal
    (Universidade Federal de Goiás, 2018-07-04) Souza, Dalton Foltran de; Vieira, Flávio Henrique Teles; http://lattes.cnpq.br/0920629723928382; Vieira, Flávio Henrique Teles; Borges, Vinicius da Cunha Martins; Rocha, Flávio Geraldo Coelho; Cardoso, Kleber Vieira
    With the development of the next generation of mobile communications systems for 5G, several technologies are being studied aiming to reach the new requirements in new application scenarios. Among them, is the use of new modulations with higher spectral efficiency in substitution of OFDM, such as F-OFDM and UFMC, and also the scheduling algorithms which are in charge of sharing resources between users. In this work, we evaluated the application of F-OFDM and UFMC, 5G modulations candidates, on downlink LTE compared with OFDM and evaluated the schedulers Round Robin, QoS Guaranteed and PSO dealing with additional resources provided by the tested modulations. For that, we compared performance considering parameters like fairness, latency, throughput and spectral efficiency. The results showed that the downlink LTE improved performance in all evaluated parameters with UFMC modulation. In fact, there were a performance improvement in all schedulers evaluated. For example, PSO based scheduler improved latency and throughput while QoS Guaranteed reached the lowest loss, as the highest fairness were reached by QoS Guaranteed and Round Robin. Also, we propose a scheduling algorithm that takes into account the queue size in the user buffer and channel quality to maximize throughput and fairness in the LTE downlink network. The metrics evaluated were transmission efficiency, throughput, fairness, delay and losses. The proposed algorithm achieved better results for all evaluated metrics.