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> 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> (Rausley A. A. de Souza and José Cândido S. Santos Filho) (Rausley A. A. de Souza and José Cândido S. Santos Filho) Thu, 02 Jan 2020 16:55:10 -0200 OJS 60 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## Fri, 17 Jul 2020 09:11:00 -0300 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## Mon, 13 Jul 2020 18:06:56 -0300 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## Mon, 13 Jul 2020 10:59:46 -0300 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## Thu, 09 Jul 2020 18:23:36 -0300 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## Tue, 07 Jul 2020 15:28:31 -0300 Asymptotic System Performance over Generalized Fading Channels with Application to Maximal-Ratio Combining <p>The performance of wireless communications systems is affected by many aspects of the fading phenomenon, such as clustering,&nbsp;nonlinearity, scattered waves, and line of sight. Even though several&nbsp;fading models exist which address a multitude of propagation conditions, in many cases the fading statistics or&nbsp;the associated system performance cannot be obtained in a closed&nbsp;form. In such cases, it is difficult to decipher how each physical aspect of fading impacts the system performance. In this work, we propose a unified asymptotic characterization at high signal-to-noise ratio&nbsp;to obtain simple, general closed-form expressions for the diversity and&nbsp;coding gains of essential performance metrics, namely, symbol error rate and outage probability. We cover generalized propagation conditions and all the referred fading aspects. The analysis is further extended to investigate the performance of multibranch maximal-ratio combining. Capitalizing on the fact that the asymptotic channel distribution around the origin fully determines the diversity and coding gains, our results provide new insights into how each physical aspect of fading ultimately affects the wireless system performance.</p> Francisco Raimundo Albuquerque Parente, Flavio du Pin Calmon, José Cândido Silveira Santos Filho ##submission.copyrightStatement## Thu, 02 Jul 2020 16:45:49 -0300 Brillouin Effect Impact in RoF Systems with Photonic-Assisted RF Amplification <p>This work reports the impact of the stimulated Brillouin scattering (SBS) in a radio-over-fiber (RoF) system with photonic-assisted radiofrequency (RF) amplification. Such photonically amplified RoF systems employs long pieces of highly nonlinear fibers (HNLFs) for stimulating the four-wave mixing (FWM) nonlinear effect, in conjunction with appropriate management of the optical modulation index, aiming to provide RF gain. Numerical and experimental results demonstrate SBS might reduce the FWM nonlinear efficiency and limit the overall system power efficiency. We propose using only 35 m of HNLF for ensuring high photonic-assisted RF gain and increasing the SBS threshold in 14 dB. The digital performance of the photonically amplified RoF system is investigated in terms of root mean square error vector magnitude (EVMRMS), before and after mitigating SBS. The 35-m HNLF piece implies in enhancing the system digital performance and reducing in 6 dB the required optical power for attaining 19 dB of photonic-assisted RF gain.</p> Eduardo Saia Lima, Luiz Augusto Melo Pereira, Ramon Maia Borges, Matheus Sêda Borsato Cunha, Arismar Cerqueira Sodré Junior ##submission.copyrightStatement## Wed, 24 Jun 2020 09:12:08 -0300 Channel Equalization Based on Decision Trees <p>This paper analyzes the application of decision trees&nbsp;to the problem of communication channel equalization. Decision&nbsp;trees are interesting structures because they are nonlinear and&nbsp;relatively simple from a computational standpoint. They are&nbsp;tested for channel models that give rise to classification tasks of&nbsp;different complexity and compared to the Bayesian equalizer and&nbsp;the Wiener linear equalizer. The results are quite encouraging, as&nbsp;they show that the tree-based equalizer reaches, in many cases,&nbsp;a performance similar to that of the Bayesian filter at a lower&nbsp;computational cost.</p> David Felice Falivene Baptista, Rafael Ferrari, Romis Attux ##submission.copyrightStatement## Mon, 22 Jun 2020 20:10:07 -0300 Performance Evaluation of Low-Complexity Algorithms for Orthogonal Time-Frequency Space Modulation <p>Data transmission in wireless systems brings numerous challenges, especially when it involves propagating in a multipath scenario over rapidly time-varying channels. In this context, Orthogonal Time-Frequency Space (OTFS) modulation has been recently proposed to work with time-frequency selective channels with high Doppler. In this modulation, the symbols are first multiplexed in a delay-Doppler domain rather than in the time-frequency domain used by Orthogonal Frequency Division Multiplexing (OFDM). The studies point out advantages of OTFS performance over OFDM in many aspects, such as data rate increase in high mobility. Another advantage is the sparsity of the channel produced by OTFS that allows using low-complexity algorithms for the detection of the data. In this paper, the performance of OTFS modulation in a doubly dispersive channel is evaluated with several low-complexity variants of the message passing algorithm (MPA) in terms of complexity and Bit Error Rate (BER) performance. The results show that MPA and Approximate Message Passing simplified by Expectation Propagation (AMP-EP) algorithms achieve higher performance. However, when taking into account both complexity and BER performance, AMP simplified by First-Order (AMP-FO) achieves the best performance complexity tradeoff.</p> Dayse Gonçalves Correia Bandeira, Didier Le Ruyet, Mylene Pischella, João Cesar Moura Mota ##submission.copyrightStatement## Wed, 10 Jun 2020 14:20:52 -0300 Receivers for the uplink of multiuser generalized spatial modulation MIMO systems <p><span class="fontstyle0">Generalized spatial modulation is envisioned as a promising communication paradigm for the next communication systems, in which high data rates and reliability are important features, but also energy and infrastructure-saving solutions are seeked. This work presents a variety of efficient suboptimal signal detection strategies for the uplink of multiuser GSM MIMO systems. They are comprised of user decoupling strategies followed by GSM signal detection schemes, and offer different balances of detection performance and computational complexity. Simulation results exhibit the performance of these strategies under different system scenarios and channel propagation effects.</span> </p> José Calpa, João Alfredo Cal-Braz, Rodrigo David, Raimundo Sampaio-Neto ##submission.copyrightStatement## Sun, 31 May 2020 09:47:53 -0300