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 under the BOAI definition of open access.</p> <p>ISSN: 1980-6604</p> en-US <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> (Lisandro Lovisolo) (Lisandro Lovisolo) Fri, 18 Feb 2022 15:14:53 -0300 OJS 60 Index Encoding and Antenna Selection in Multiuser Precoder Index Modulation MIMO Communication <p>Index modulation (IM) offers energy efficient solutions to communication systems by altering the on/off status of entities of the system. This work presents a multiuser (MU) IM-based system operating in a multiple-input multiple-output (MIMO) channel, named Multiuser Precoder Index Modulation (MU-PIM-MIMO), in which the choice of the IM-precoder matrices, responsible for assigning zero or nonzero values to the information vector, is a source of information. System model is specified for Zero-Forcing and Block Diagonalization channel precoders, as well as additional mechanisms, such as user notification and channel estimation. Numerical results show that MU-PIM-MIMO systems can offer attractive tradeoff between detection performance and spectral efficiency. Metrics for selection of the most favorable information bearing positions (IBP) patterns of the information vector, based on the maximization of the signal-to-noise ratio and on the maximization of the achievable rate, are developed in order to offer further improvements in system performance. Additionally, a scenario where the number of transmit antenna elements exceeds the number of radiofrequency chains at the base station is considered, and optimal and computational efficient ways to select the IBP patterns and the active transmit antennas are proposed. Simulation results evidence the effectiveness of the strategies.</p> Azucena Duarte, João Alfredo Cal-Braz, Raimundo Sampaio Neto ##submission.copyrightStatement## Fri, 11 Nov 2022 09:27:28 -0300 On Generating Monte Carlo Simulations of Underwater Acoustic Communication Systems with Application to Transmit Beamforming <div class="page" title="Page 1"> <div class="layoutArea"> <div class="column"> <p>Underwater Acoustic (UWA) communication systems still rely heavily on at-sea trials. This work presents an operational framework that significantly reduces the need for practical experiments. The key idea is to generate channel impulse responses (CIRs) drawn from probability density functions constructed based on trusted information and to employ Monte Carlo simulations to develop new UWA communication systems. Hence, the proposed operational framework depends only on cheaper-to-acquire physical measurements to produce CIRs. It comprises a model-based CIR replay tool and a stochastic-based UWA channel simulator. The former can be any model-based CIR replay tool, and the latter is proposed in this work and validated using data from four different practical experiments. We also carried out experiments for a transmit beamforming with signals digitally modulated in binary phase-shift keying, which were transmitted by an array and by a single source with equivalent power. For the array, the ideal transmit direction comes from the lowest bit error rate (BER) obtained with computer simulations. This paper compares the performance of the transmit array to the single source transmission and the results of a practical experimental transmission with a Monte Carlo simulation employing the proposed technique. We show that both achieved close results regarding BER and mean squared error. The conclusion is that the proposed operational framework, once adjusted to the specific transmission site, can be used to design new UWA communication systems, eliminating the burden of at-sea trials for tests of new transceivers. Finally, we conducted real-life transmit beamforming experiments to verify the BER gain obtained in practice using the steering angle obtained from simulations.</p> </div> </div> </div> Denis Backer de souza, Vinicius M. Pinho, Rafael Chaves, Marcello L. R. Campos, José A. Apolinário Jr. ##submission.copyrightStatement## Thu, 03 Nov 2022 16:33:29 -0300 On the Information Content of Predictions in Word Analogy Tests <pre>An approach is proposed to quantify, in bits of information, the actual relevance of analogies in analogy tests. The main component of this approach is a <em>soft</em> accuracy estimator that also yields entropy estimates with compensated biases. Experimental results obtained with pre-trained GloVe 300-D vectors and two public analogy test sets show that proximity hints are much more relevant than analogies in analogy tests, from an information content perspective. Accordingly, a simple word embedding model is used to predict that analogies carry about two bits of information, which is experimentally corroborated.</pre> Jugurta Montalvão ##submission.copyrightStatement## Tue, 18 Oct 2022 12:02:53 -0300 Dual-band Polarization-independent Absorber Based on Resistive Frequency Selective Surface <p>In this paper, a three-layered frequency-selective absorber (FSA) that can efficiently absorb electromagnetic waves (EM) in a double-band is proposed. The proposed structure is designed so that signals reflected from the frequency selective ground plane are located at 2.4 and 5.5 GHz (ISM and UNII bands) and absorbed by the front resistive layers. Simulation results show that the proposed absorber not only blocks transmission in the desired bands but absorbs the signals reflected from the conductive layer. Reflective FSS unit cells are composed of double square loops printed on an FR-4 substrate and the resistive layers are formed of OhmegaPly material with a resistivity of 50 ohms per square. Furthermore, the proposed absorber is 0.17λ thick at the lowest frequency of absorption. The experimental results agree with the numerical simulations and show an absorptivity of more than 90% at 2.4 and 5.5 GHz, covering entirely ISM and UNII bands.</p> Anamaria Sena Maia, Antônio Luiz Pereira de Siqueira Campos, Maurício Weber Benjó da Silva, Ruann Víctor de Andrade Lira, Alfredo Gomes Neto ##submission.copyrightStatement## Wed, 05 Oct 2022 15:37:34 -0300 Empirical Mode Decomposition: Theory and Applications in Underwater Acoustics <p>Empirical mode decomposition (EMD) is a signal processing method that produces a data-driven time-frequency representation suited to characterize time-varying and nonlinear phenomena. In EMD, intrinsic mode functions (IMF) are sequentially estimated from the signal of interest to represent different intrinsic oscilation modes and produce an orthogonal representation of the original information. Different algorithms have been proposed for EMD estimation to deal with limitations such as mode-mixing and noise sensitivity. To obtain a frequency-domain representation, EMD is usually associated with the Hilbert transform, in this case, the method is referred to as the Hilbert-Huang transform (HHT). This paper presents a theoretical review of the fundamental aspects of both EMD and HHT, such as IMF estimation procedure and IMF orthogonality. Variations of the original EMD algorithm are also presented. Both simulated and experimental underwater acoustic signals are used to illustrate the efficiency of EMD/HHT in revealing relevant characteristics from time-varying and nonlinear information.</p> Elio Pithon Sarno Filho, Anderson Damacena Santos, Henrique Moura Sinezio, Eduardo Furtado Simas Filho, Antônio Carlos Lopes Fernandes Jr, José Manoel de Seixas ##submission.copyrightStatement## Mon, 22 Aug 2022 08:59:26 -0300 On Symmetric Channels and Codes Over the Quaternion Group <p>In this paper we study symmetric channels and group codes over the quaternion group Q<sub>8</sub>.&nbsp;We show that, related to these channels, there is the number C<sub>Q8</sub><sub>,</sub> called group-capacity,&nbsp;which is less or equal than the capacity of the channel. Also we show that C<sub>Q8&nbsp;</sub>is an upper bound for the rate of any reliable quaternion group code. Finally we show&nbsp;that the group-capacity equals the channel capacity.</p> Jorge P Arpasi ##submission.copyrightStatement## Tue, 26 Jul 2022 15:37:46 -0300 Performances of 2r16APSK and DVB-S2 16APSK Modulations over a Two-Link Satellite Channel <p>In this paper, the 2r16APSK modulation is contrasted&nbsp;with the 16APSK modulation adopted in the digital&nbsp;video broadcast standard, the DVB-S2, aiming at verifying if&nbsp;the 2r16APSK can be considered an alternative choice for the&nbsp;DVB-S2 and other alike communication systems when subjected&nbsp;to nonlinear distortions. To this end, the performances of both&nbsp;modulations are assessed in terms of the metrics: bit error&nbsp;rate (BER), constellation figure of merit (CFM), peak-to-average&nbsp;power ratio (PAPR), total degradation (TD) versus input back-off&nbsp;(IBO), and spectral regrowth, when the transmitted signal goes&nbsp;through a two-link satellite channel under memoryless nonlinear&nbsp;distortion produced by a traveling wave tube amplifier (TWTA),&nbsp;which is described by the Saleh model. The results show that the&nbsp;2r16APSK modulation is indeed an alternative choice.</p> Dayan Adionel Guimarães ##submission.copyrightStatement## Wed, 20 Jul 2022 13:49:17 -0300 Resource Allocation for Maximizing Spectral Efficiency in a Multiuser MFSK System <p>In this paper we explore strategies to improve spectral efficiency values of a multiuser M-ary Frequency Shift Keying (MFSK) system when a fast and frequency selective fading channel with limited bandwidth is available and $L$ receiving antennas are present at the base station. Two options are considered: bandwidth splitting and cell splitting, where random user distribution and the effects of antenna directivity on signal to noise ratio was considered. Results show that in this situation the best case scenario is the one in which all users share the whole bandwidth instead of splitting it. Also, given the limitation on available antennas and radio frequency receiver chains at the base station, it is better to split cell antennas into as many sectors as possible, even at the cost of losing spatial diversity in each sector. Given the constraints, sectoring allows the system to reach values of spectral and energy efficiencies unachievable by spatial diversity by itself.</p> Manish Sharma, Daniel Basso Ferreira ##submission.copyrightStatement## Wed, 06 Jul 2022 10:03:36 -0300 On the Uniqueness of the Quasi-Moment-Method Solution to the Pathloss Model Calibration Problem <p><strong>Investigations in this paper focus on establishing the uniqueness properties of the Quasi-Moment-Method (QMM) solution to the problem of calibrating nominal radiowave propagation pathloss prediction models. Nominal (basic) prediction models utilized for the investigations, were first subjected to QMM calibrations with measurements from three different propagation scenarios. Then, the nominal models were recast in forms suitable for Singular Value Decomposition (SVD) calibration before being calibrated with both the SVD and QMM algorithms. The prediction performances of the calibrated models as evaluated in terms of Root Mean Square Prediction Error (RMSE), Mean Prediction Error (MPE), and Grey Relational Grade-Mean Absolute Percentage Error (GRG-MAPE) very clearly indicate that the uniqueness of&nbsp; QMM-calibrations of basic pathloss models is more readily observable, when the basic models are recast in forms specific to SVD calibration. In the representative case of calibration with indoor-to-outdoor measurements, RMSE values were recorded for QMM-calibrated nominal models as 5.2639dB for the ECC33 model, and 5.3218dB for the other nominal models. Corresponding metrics for the alternative (rearranged) nominal models emerged as 5.2663dB for the ECC33 model and 5.2591dB for the other models. A similar general trend featured in the GRG-MAPE metrics, which for both SVD and QMM calibrations of all the alternative models, was recorded as 0.9131, but differed slightly (between 0.9138 and 0.9196) for the QMM calibration of the nominal models. The slight differences between these metrics (due to computational round-off approximations) confirm that when the &nbsp;components of basic models are linearly independent, the QMM solution is unique. Planning for wireless communications network deployment may consequently select any basic model of choice for QMM-calibration, and hence, identify relative contributions to pathloss by the model’s component parts.</strong></p> Hisham Abubakar Muhammed, Mr., Ayotunde Abimbola Ayorinde, Dr., Francis Olutunji Okewole, Engr., Michael Adedosu Adelabu, Dr., Ike Mowete ##submission.copyrightStatement## Fri, 01 Jul 2022 00:00:00 -0300 User-Level Handover Decision Making Based on Machine Learning Approaches <p>This letter covers a broad comparison of methods for classification and regression applications for a user-level handover decision making in scenarios with adverse propagation conditions involving buildings, coverage holes, and shadowing effects. The simulation campaigns are based on network simulator <em>ns-3</em>. The comparison encompasses classical machine learning approaches, such as KNN, SVM, and neural networks, but also state-of-the-art fuzzy logic systems and latter boosting machines. The results indicate that SVM and MLP are the most suitable for the classification of the best handover target, although fuzzy system SOFL can perform similarly with lower processing time. Additionally, for the download time estimation, LightGBM provides the smallest error with short processing time, even in hard propagation scenarios.</p> João Lima, Alvaro Medeiros, Eduardo Aguiar, VICENTE ANGELO DE SOUSA JUNIOR, Tarciana Guerra ##submission.copyrightStatement## Wed, 22 Jun 2022 13:03:00 -0300