Journal of Communication and Information Systems <p>The Journal of Communication and Information Systems (JCIS) features high-quality, peer-reviewed technical papers in several areas of communications and information systems. The JCIS is jointly sponsored by the Brazilian Telecommunications Society (SBrT) and the IEEE Communications Society (ComSoc). As from June 2020, Prof. Rausley Adriano Amaral de Souza from National Institute of Telecommunications (Inatel) and Prof. José Cândido Silveira Santos Filho from University of Campinas (UNICAMP) are the Editors-in-Chief of the JCIS.&nbsp;</p> <p>There are no article publication or submission charges. Previous editions of the JCIS can be accessed <a href="/index.php/JCIS/issue/archive" target="_blank" rel="noopener">here</a>.</p> <p>This is an open access journal which means that all content is freely available without charge to the user or his/her institution, permanently accessible online immediately upon assignment of the DOI. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles, or use them for any other lawful purpose, without asking prior permission from the publisher or the author. This is in accordance with the BOAI definition of open access.</p> <p>ISSN: 1980-6604</p> Brazilian Telecommunications Society en-US Journal of Communication and Information Systems 1980-6604 <p><span>Authors who publish with this journal agree to the following terms:</span><br /><br /></p><ol type="a"><ol type="a"><li>Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a <a href="" target="_new">Creative Commons Attribution License</a> that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.</li></ol></ol><p> </p><ol type="a"><ol type="a"><li>Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.</li></ol></ol><p> </p><ol type="a"><ol type="a"><li>Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See <a href="" target="_new">The Effect of Open Access</a>).</li></ol></ol><p>___________</p> A Machine Learning Approach for Handover in LTE Networks with Signal Obstructions <p>Legacy cell-deployment strategies have been adapted to fulfill the increasing demand for wireless broadband internet access. One of them, the Hierarchical Cell Structure (HCS), that is already in use in LTE-A and it is considered essential for the 5G, consists of the deployment of several types of small cells under the umbrella of macrocells, creating overlaid coverages. Due to their low power and bellow-rooftop-level, sometimes indoor base stations, the small cells are severely affected by the surrounding obstacles, making the perceived Quality of Service (QoS) of the users subject to fast variations, thus rendering ineffective the classical approaches to mobility management, that are unable to predict those severe fading situations (coverage holes). Considering the amount of available information on the network performance and the evolution of real-time processing capabilities, the enhancement of LTE functionalities (such as the handover) by means of machine learning algorithms became possible. This work proposes and evaluates the performance of a machine learning based approach to handover in scenarios with the presence of signal-blocking obstacles. We use the ns-3 simulation for our proof of concept simulations. Our machines learn from experience and they are, therefore, able to choose the eNB that will most likely offer the user the highest long term QoS after the handover procedure, even in severe propagation conditions. The proposed schemes substantially improve the users' QoS in certain circumstances.</p> Tarciana Cabral de Brito Guerra Ycaro Ravel Dantas Vicente Angelo Sousa Jr ##submission.copyrightStatement## 2020-11-18 2020-11-18 35 1 271 289 10.14209/jcis.2020.28 Wavelet Channel Coding <p>In this paper, the wavelet channel coding (WCC) is revisited in a more general analysis embracing flat real wavelet matrices derived from a Haar matrix and complex input symbols. WCC encoding and decoding are algebraically described and a probability distribution of wavelet symbols is formulated. Signal constellations for transmission of wavelet symbols are proposed and the constellation average energy is deduced from probability generating functions of the wavelet symbols. System performance over a flat Rayleigh channel is analyzed and compared with symbol-by-symbol detecting systems and diversity two space-time block coding (STBC) systems. Simulation results show that WCC presents better performance than ordinary symbol-by-symbol detecting systems, particularly at higher signal-to-noise ratios for higher spectral efficiencies, and STBC systems for spectral efficiency of 1 bit/s/Hz.</p> João Fonseca Neto Leocarlos Bezerra da Silva Lima Francisco Marcos de Assis ##submission.copyrightStatement## 2020-11-11 2020-11-11 35 1 256 270 10.14209/jcis.2020.27 A Hybrid Firefly-Genetic Algorithm for Planning of Optical Transport Networks <p class="Abstract"><span lang="EN-US">The network design is a well-known combinatorial optimization problem that is classified as NP-Hard. The main purpose of design is often the same, to allocate and size available resources in the most possible efficient way in terms of budget, considering optimization models oriented towards minimizing costs. In this paper, it is proposed to use a hybrid optimization method called Hybrid Firefly-Genetic Algorithm to solve the Integer Linear Programming (ILP) problem, for Optical Transport Network (OTN) planning, considering cost minimization. The method combines the discrete firefly algorithm with the standard genetic algorithm. To apply this method, first it is proposed a mathematical formulation for the optical network planning problem. The other novelty of the proposed model is that it accomplishes the optical network design with the possibility of multiple destinations of the demand traffic matrix and with dynamic allocation of transmission systems modularity. Computational experiments are carried out to evaluate the performance of the hybrid Firefly-Genetic algorithm. The results show that the proposed algorithm outperforms other metaheuristics described in the literature.</span></p> <p>&nbsp;</p> Bruno Quirino de Oliveira Marcos Antônio de Sousa Flávio Henrique Teles Vieira ##submission.copyrightStatement## 2020-09-24 2020-09-24 35 1 243 255 10.14209/jcis.2020.26 An open-source end-to-end ASR system for Brazilian Portuguese using DNNs built from newly assembled corpora <p>In this work, we present a baseline end-to-end&nbsp;system based on deep learning for automatic speech recognition&nbsp;in Brazilian Portuguese. To build such a model, we employ&nbsp;a speech corpus containing 158 hours of annotated speech&nbsp;by assembling four individual datasets, three of them publicly&nbsp;available, and a text corpus containing 10.2 millions of sentences.&nbsp;We train an acoustic model based on the DeepSpeech 2 network,&nbsp;with two convolutional and five bidirectional recurrent layers. By&nbsp;adding a newly trained 15-gram language model at the character&nbsp;level, we achieve a character error rate of only 10.49% and a&nbsp;word error rate of 25.45%, which are on a par with other works&nbsp;in different languages using a similar amount of training data.</p> Igor Macedo Quintanilha Sergio Lima Netto Luiz Wagner Pereira Biscainho ##submission.copyrightStatement## 2020-09-01 2020-09-01 35 1 230 242 10.14209/jcis.2020.25 Analysis of Acoustic Feedback Cancellation Systems based on Direct Closed-Loop Identification <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>This work presents, using the least squares estimation theory, a theoretical and experimental analysis on the performance of the standard adaptive filtering algorithms when applied to acoustic feedback cancellation. Expressions for the bias and covariance matrix of the acoustic feedback path estimate provided by these algorithms are derived as a function of the signals statistics as well as derivatives of the cost function. It is demonstrated that, in general, the estimate is biased and presents a large covariance because the closed-loop nature of the system makes the cross-correlation between the loudspeaker and system input signals non-zero. Simulations are carried out to exemplify the results using speech signals, a long acoustic feedback path and the recursive least squares algorithm. The results illustrate that these algorithms converge very slowly to a solution that is not the true acoustic feedback path. The relationship between the performance of the adaptive filtering algorithms and the aforementioned cross-correlation is proven by varying the signal-to-noise ratio and the delay introduced by the forward path.</p> </div> </div> </div> Bruno Catarino Bispo Cézar F. Yamamura Wellington M. S. Nogueira Edson A. R. Theodoro Pedro Miguel Rodrigues ##submission.copyrightStatement## 2020-08-25 2020-08-25 35 1 217 229 10.14209/jcis.2020.24 Frequency Selective Surface Microwave Absorber for WLAN Applications <p>Many researchers are studying electromagnetic wave absorbers. This is mainly due to the large number of existing wireless systems. The absorbers find numerous applications, from commercial to military systems. Allied to this, also the interest in Frequency Selective Surfaces (FSS), which are, basically, spatial filters, grows. Thus, this work proposes the use of FSS to design electromagnetic absorbers. In this study, Altair FEKO software was used. A prototype is built to validate the analysis performed. A good agreement between the numerical and experimental results is observed. Furthermore, measured results show that the absorber panel suppresses reflection (below – 10 dB) from 1.98 GHz to 3.08 GHz, covering the entire ISM band.</p> Thais Carvalho Areias Roberta N. G. Carvalho Mauricio Weber Benjó da Silva Leni J. Matos José Jaime G. Peixoto Neto Antônio Luiz P. S. Campos Alfredo Gomes Neto ##submission.copyrightStatement## 2020-07-17 2020-07-17 35 1 208 216 10.14209/jcis.2020.23 Unified Scheduling Framework for Dual Connectivity in Multi-RAT NSA 5G Networks <p>Supporting the dual connectivity technology in non-stand-alone 5G scenarios involves three main functionalities: a user device (UD)-base station (BS) association (UBA) mechanism, a flow control algorithm (FCA) to determine the data split transmitted by each BS and radio resource management (RRM) algorithms. However, previous works only focused on the design of at most two of these functionalities. In this<br>letter, we go beyond and design a unified scheduling framework including the three aforementioned functionalities. The proposed framework targets the user satisfaction maximization and runs in a completely decentralized fashion, where the UBA algorithm runs independently at each UD, the FCA is executed at the master LTE BS and the RRM is performed individually by each BS. Simulations show the incremental gains of each proposed functionality as well as the total gain of the unified framework.</p> Roberto Pinto Antonioli Diego Aguiar Sousa Emanuel Bezerra Rodrigues Igor Moaco Guerreiro Carlos Filipe Moreira e Silva Tarcisio Ferreira Maciel Francisco Rodrigo Porto Cavalcanti ##submission.copyrightStatement## 2020-07-13 2020-07-13 35 1 203–207 203–207 10.14209/jcis.2020.22 Coexistence Analysis Between 5G NR and TVRO in C-Band <p class="Abstract"><span lang="EN-US">This work reports a coexistence analysis between 5G New Radio (5G NR) and Satellite Television Receive Only (TVRO) in C-Band. The coexistence experiments were based on the two following systems: broadcast of analog and digital TV channels, received by a 1.7 meters parabolic antenna pointed to the Star One C2 geostationary satellite from Embratel; 100 MHz-bandwidth 5G NR link at 3.55 GHz with two printed logperiodic antennas. The performance analysis has been carried out as a function of the TV channel quality signal, by means of varying the 5G power level at vertical polarization. Measured spectra of either RF and IF signals are presented for demonstrating a probable interference problem due to the installation of 5G base stations close to TVRO user homes. For instance, there are still 22 million TVRO users in Brazil and 120 million homes attended by C-Band satellites in United States for radio and TV services.</span></p> <p>&nbsp;</p> Luciano Camilo Alexandre Lucas de Oliveira Veiga Agostinho Linhares José Reis Pinto Moreira Marcelo Abreu Arismar Cerqueira Sodré Junior ##submission.copyrightStatement## 2020-07-13 2020-07-13 35 1 198–202 198–202 10.14209/jcis.2020.21 Optimized Energy Consumption for Slotted Aloha and CSMA/CA Multihop Ad Hoc Networks <p>Ad hoc and wireless sensor networks are characterized by their ability to monitor phenomena in the most adverse scenarios. However, to perform well, these networks need to be self-adjusting and save energy. In general, these networks operate without human interference and require strategies to provide longer operating life. This paper investigates the energy consumption in a random multihop ad hoc network, comparing the slotted Aloha with the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) implemented in the IEEE 802.11 Distributed Coordination Function (DCF) as medium access control (MAC) protocols. We obtain the optimal transmission power as a function of physical and link layers parameters which results the optimized energy consumption per successfully transmitted bit. In this paper, we find that there are values of these parameters that can be used to extend the battery life of wireless communication devices comparing the Aloha and CSMA/CA performance.</p> Bruna Alves da Silva Renato Mariz de Moraes ##submission.copyrightStatement## 2020-07-09 2020-07-09 35 1 189 197 10.14209/jcis.2020.20 Low-Complexity Tree-Based Iterative Decoding for Coded SCMA <p>Sparse Code Multiple Access (SCMA) is a powerful multiple access technique for future generations of wireless communication where users are allowed to transmit through pre-defined channel resources with a controlled degree of collision. The base-station then recovers all the users' data through some iterative method. The well-known Message-Passing Algorithm (MPA) has excellent performance but has exponential decoding complexity. Alternative decoding algorithms, such as MPA in the log-domain (Log-MPA), have been proposed in the literature aiming to reduce the decoding complexity while not significantly decreasing performance. In recent work, the authors proposed a modification in the conventional Log-MPA by exploring a tree structure associated with the decoding equations. By properly avoiding symbols with low reliability, a pruned tree is obtained, yielding an arbitrary trade-off between performance and complexity in the joint detection. In the present work, we extend this contribution by showing that the advantages of the tree-based decoding algorithm are magnified when SCMA is coupled to an error-correcting code, in particular, a Low-Density-Parity-Check (LDPC) code. Through computer simulations, we show that an improved performance-decoding complexity trade-off is obtained.</p> Ana Luiza Scharf Bartolomeu Uchˆoa-Filho Bruno Fontana da Silva Didier Ruyet ##submission.copyrightStatement## 2020-07-07 2020-07-07 35 1 181 188 10.14209/jcis.2020.19