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> Impact of Feature Selection Methods on the Classification of DDoS Attacks using XGBoost <p>Distributed Denial of Service (DDoS) attacks impose a major challenge for today's security systems, given the variety of implementations and the scale they can achieve. One approach for their early detection is the use of Machine Learning (ML) techniques, which create rules for classifying traffic from historical data. However, different types of data contribute unequally to the assertiveness of the trained model. The use of Feature Selection (FS) techniques as a pre-processing step allows identification of the most relevant features for the problem in question. This action reduces training time and can even improve performance when noisy variables are eliminated. The current work is based on a public dataset and the XGBoost algorithm to measure the impact of FS techniques on the DDoS attack classification problem. We consider both techniques independent of the sample labels, as well as methods that use this information to rank the variables in order of importance. We analyzed the problem from the point of view of Binary and Multiclass classification. We also created a benchmark of classification metrics and execution times. Our comparisons involved the Accuracy, Precision, Recall, and F1 Score metrics for different FS methods, in addition to training and execution time. In the results it is possible to verify both for the Binary (30% reduction of the features) and Multiclass classifiers (40% reduction of the features), that the ANOVA method showed as the most advantageous.</p> Pedro Henrique Hauy Netto de Araujo Anderson Silva Norisvaldo Ferraz Junior Fabio Cabrini Alessandro Santiago Adilson Guelfi Sergio Kofuji ##submission.copyrightStatement## 2021-12-28 2021-12-28 36 1 200 214 10.14209/jcis.2021.22 Alinha-PB <p>Phonetic alignment is the task of finding the limits of phones and higher units in an audio file. This has been reliably done in many languages such as English, French and German, but, so far, no available Brazilian Portuguese aligner had a performance comparable with the ones used for these other languages. Thus, the main goal of this work was to implement a useful tool for forced alignment for Brazilian Portuguese. The implementation was done in two steps, the grapheme-to-phoneme conversion and the alignment itself. The Converter is responsible for receiving the input transcription in graphemes and converting it to its equivalent in phonemes and allophones, and was implemented using computational rules derived from the analysis of regular grapheme-phoneme relations in Brazilian Portuguese and an exception dictionary, for words to which no regular rules could be applied. The Aligner was responsible for aligning the phonemes/allophones of the previous module to the corresponding acoustic intervals of the audio file, called "phones". This module was implemented using hidden Markov models. Results for the Converter have an accuracy of over 99%, where the main mistakes involved mid vowels /e/ and /ɛ/ and /o/ and /ɔ/. As for the Aligner, the best model has 87% of the alignments with errors below 25 ms.</p> João Segato Kruse Plinio Almeida Barbosa ##submission.copyrightStatement## 2021-12-20 2021-12-20 36 1 192 199 10.14209/jcis.2021.21 Measurement and Prediction of Short-Range Path Loss between 27 and 40 GHz in University Campus Scenarios <pre style="-qt-block-indent: 0; text-indent: 0px; margin: 0px;"><span style="color: #000000;">In this paper, we present the results of short-range path loss measurement in the microwave and millimetre wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (</span><span style="text-decoration: underline; color: #000000;">ABG</span><span style="color: #000000;">) model and the close-in free space reference distance with frequency-dependent path loss exponent (</span><span style="text-decoration: underline; color: #000000;">CIF</span><span style="color: #000000;">) model, are tested against the measured data, and an improved prediction method that includes the path loss dependence on the height difference between transmitter and receiver is proposed. The main contribution of this paper is the use of the Fuzzy technique to perform path loss predictions for short links in the millimetre wave range, from 27 to 40 GHz, providing lower errors when compared to the traditional </span><span style="text-decoration: underline; color: #000000;">ABG</span><span style="color: #000000;"> and </span><span style="text-decoration: underline; color: #000000;">CIF</span><span style="color: #000000;"> models. However, it should be noted that the Fuzzy technique uses a set of equations to perform the prediction and the attenuation coefficient is not explicit as in the classical models. Also, a non-negligible correlation between the difference in height between transmitter and receiver positions and the path loss in such short links (i.e., the path inclination) has been observed and requires further investigation. If confirmed, it could provide an additional parameter to improve the accuracy of the traditional </span><span style="text-decoration: underline; color: #000000;">ABG</span><span style="color: #000000;"> model.</span></pre> Glaucio Lopes Ramos Carlos Vargas Luiz da Silva Mello Paulo Pereira Robson Vieira Sandro Gonçalves Cássio Rego ##submission.copyrightStatement## 2021-11-12 2021-11-12 36 1 184 191 10.14209/jcis.2021.20 Influence of a Direct-Conversion Receiver Model on the Performance of Detectors for Spectrum Sensing <p>An implementation-oriented receiver model for centralized data-fusion cooperative spectrum sensing was proposed a few years ago to assess the performances of the energy detector and some eigenvalue-based detectors. The model is grounded on a direct-conversion receiver whose main influences on the sensing performance have been found to be the direct-current-offset and the automatic gain control. In this paper we improve the referred model and use it to assess the performances of state-of-the-art blind detectors whose computations of the test statistics are among the least complex known to date. These detectors are the Gerschgorin radii and centers ratio (GRCR), the Gini index detector (GID), the Pietra-Ricci index detector (PRIDe), and the locally most powerful invariant test (LMPIT). The energy detector (ED) is also included as a benchmark. It is shown that the performances of all detectors are overestimated if the conventional model (in the sense of signal processing operations not oriented by receiver implementation aspects) is adopted. The ED is the detector whose performance is the most affected by the operations made in the implementation-oriented model. The other detectors are affected in quite similar ways, with an advantage of the PRIDe in most of the situations analyzed.</p> Dayan Adionel Guimarães Elivander Judas Tadeu Pereira ##submission.copyrightStatement## 2021-11-10 2021-11-10 36 1 173–183 173–183 10.14209/jcis.2021.19 A Compact Dual-Band UHF Microstrip Patch Antenna for CubeSat Applications <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>This paper presents a slitted, dual-band, square, microstrip patch antenna for CubeSat application. Compared to recently reported works, the originality of this design is the capability to operate at dual-band UHF, using a single feeding point, and, in this way, reducing the risks inherent to wire antennas. The antenna resonates at 399.025 MHz and 431.600 MHz frequencies and it is limited at 100 mm x 100 mm area in a CubeSat face. Forty slits, on the perimeter of a square patch, ten slits on each edge, and a high relative permittivity substrate was used to decrease the operating frequencies. An asymmetry between the slits allows the operation in two different frequencies. This slitted square patch may be up to 48% smaller in area than a square patch without slits, both with the same operating frequency. The design, simulation, manufacturing, and measurement details are presented. Simulated and measured results reveal that the gain, the radiation patterns, the bandwidth, and other parameters are adequate for CubeSat applications.</p> </div> </div> </div> Wellington Guilherme da Silva Antonio L. P. S. Campos, Dr Juan Rafael Filgueira Guerra ##submission.copyrightStatement## 2021-11-09 2021-11-09 36 1 166–172 166–172 10.14209/jcis.2021.18 Improving Bluetooth Mesh Energy Efficiency Using Clustering <p>This work proposes a Clustering Algorithm to improve the energy efficiency of Bluetooth Mesh networks. To further reduce the burden over the Cluster Heads, a Radio Duty Cycling algorithm that requires only a simple modification on the Bluetooth packet transmission logic is proposed. Computer simulations show that the radio duty cycling and clustering methods are effective in improving energy efficiency. It is observed that duty cycling provides a 78% improvement on the energy efficiency. In addittion, simulations show that the proposed clustering technique is effective in controlling the excessive message replication that is inherent in flooding operation, which in turn have a positive impact on packet delivery ratio and network scalability. Finally, it can be observed that the proposed clustering algorithm together with the proposed radio duty cycling algorithm can provide an improvement on the energy efficiency when compared to the baseline Bluetooth Mesh profile.</p> Joelton Deonei Gotz Ohara Kerusauskas Rayel Guilherme Luiz Moritz ##submission.copyrightStatement## 2021-08-30 2021-08-30 36 1 156 165 10.14209/jcis.2021.17 Iterative Error Decimation for Syndrome-Based Neural Network Decoders <p>In this letter, we introduce a new syndrome-based decoder where a deep neural network (DNN) estimates the error pattern from the reliability and syndrome of the received vector. The proposed algorithm works by iteratively selecting the most confident positions to be the error bits of the error pattern, updating the vector received when a new position of the error pattern is selected. Simulation results for the (63,45) and (63,36) BCH codes show that the proposed approach outperforms existing neural network decoders. In addition, the new decoder is flexible in that it can be applied on top of any existing syndrome-based DNN decoder without retraining.</p> Jorge Kysnney Santos Kamassury Danilo Silva ##submission.copyrightStatement## 2021-08-27 2021-08-27 36 1 151 155 10.14209/jcis.2021.16 An Analog Filter Bank-based Circuit for Performing the Adaptive Impedance Matching in PLC Systems <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>Aiming to bring attention to the necessity of dealing with the dynamics of access impedance in electric power systems, this paper introduces an adaptive impedance matching circuit that is based on an analog filter bank approach. In this sense, it describes a prototype that validates the proposed filter bank approach for improving impedance matching. Numerical results obtained with the detailed prototype operating in the frequency band between 2 and 500 MHz show that the proposed analog filter bank approach helps to improve impedance matching in power line communication (PLC) systems. Also, the numerical results show that the dynamics of impedance matching between two or more PLC transceivers is a difficult task to be accomplished because real-time coordination among them is necessary. Overall, it is shown that the proposed analog filter bank approach constitutes an interesting research direction for improving impedance matching between PLC transceivers and electric power systems.</p> </div> </div> </div> Luís Guilherme da Silva Costa Antônio Carlos Moreirão de Queiroz Vinícius Lagrota Rodrigues da Costa Moisés Vidal Ribeiro ##submission.copyrightStatement## 2021-08-20 2021-08-20 36 1 133 150 10.14209/jcis.2021.15 Optimizing the Spectral Efficiency in mmWave Massive SU-MIMO Systems Using Hybrid Processing <p>In this letter, a methodology to optimize the spectral efficiency in downlink massive single-user multiple-input multiple-output (SU-MIMO) millimeter-wave (mmWave) systems is proposed. Making use of a hierarchical strategy, four optimization sub-problems are formulated, whose solutions and derivations are strongly related to each other. This fact produces efficient coordination between the parties involved such that higher spectral efficiency is achieved. Therefore, the main feature of the proposed methodology relies on the coordination of the proposed RF and passband beamformer of both the transmitter and the receiver. This fact produced that the proposed hybrid processing surpasses the considered hybrid processings and even the considered fully-digital technique in the simulated scenarios.</p> Alvaro Javier Ortega ##submission.copyrightStatement## 2021-07-25 2021-07-25 36 1 128 132 10.14209/jcis.2021.14 MUSA Grant-Free Access Framework and Blind Detection Receiver <p>Recently, a non-orthogonal multiple access scheme called multi-user shared access (MUSA) was proposed to provide massive connection capability of low-complexity devices in the 5G networks. MUSA achieves higher spectral efficiency allowing independent devices to transmit data on the same physical layer time-frequency resources. Furthermore, MUSA introduces a grant-free transmission and a blind multi-user detection at the receiver, reducing the complexity on the transmit side. This approach is interesting for Internet of Things applications over mobile communication networks, where the devices have limited power and processing capacity. The references available in the literature about this multiple access scheme do not bring sufficient details about the MUSA multi-user detector. This limitation makes it difficult to evaluate the MUSA performance and to propose improvements for this new technique. The main goal of this paper is to provide a framework describing the entire communication chain using MUSA as multiple access. This paper also brings a proposal for a blind multi-user detection, where the information about the MUSA parameters and the channel state information are unknown at the receiver side. The performance of the MUSA multi-user detector is improved by a deep learning based processing that improves the quality of the channel estimation provided by a initial minimum mean square error estimator. The proposed deep neural network architecture employed to improve the channel estimation allows more users to share the same time-frequency resources for a given target block error rate, increasing the overall spectrum efficiency of the system.</p> Guilherme Pedro Aquino Tiago Cardoso Barbosa Marwa Chafii Luciano Leonel Mendes Abdul Karim Gizzini ##submission.copyrightStatement## 2021-07-12 2021-07-12 36 1 119 127 10.14209/jcis.2021.13