Papers by Felipe Pereira de Figueiredo
Progress in Electromagnetics Research Letters, 2022
We show a new polarization-and angle-insensitive ultrathin metasurface design using four conjugat... more We show a new polarization-and angle-insensitive ultrathin metasurface design using four conjugated hexagonal split-ring resonators (CHSRRs). The CHSRRs are made of copper and arranged in a λ/4 cell-size polyimide film substrate with a dielectric constant of 3.5 and thickness of 0.2 mm (λ/400 at 3.75 GHz). Each CHSRR aperture faces one corner of the square unit cell, thus forming a conjugated loop to achieve TE and TM polarization-insensitive behavior in a wide range of incident angles. Results demonstrated a −10 dB impedance bandwidth of 530 MHz (3.44 to 3.97 GHz) under normal incidence, partially covering the n77 band used for 5G applications.
Proceedings of the 15th ACM Conference on Embedded Network Sensor Systems, 2017
Spectrum scarcity has been driving cellular operators to utilize unlicensed spectrum in conjuncti... more Spectrum scarcity has been driving cellular operators to utilize unlicensed spectrum in conjunction with licensed bands to deliver mobile data to its Long-Term Evolution (LTE) users, offloading the fully allocated LTE bands. However, the use of LTE in unlicensed spectrum creates numerous challenges as the fair coexistence with other technologies. A myriad of experimental works tackles the problems involved in the coexistence of different radio access technologies (RAT) in unlicensed spectrum, however, they do not cover all aspects of the problem and fail to provide the framework adopted in the experiments for reproducible research. Therefore, in this demo we present a highly configurable packetized-LTE PHY open-source framework for coexistence experiments. The framework allows the evaluation and comparison of different coexistence techniques.
2019 IEEE International Symposium on Dynamic Spectrum Access Networks (DySPAN), 2019
This paper presents the architecture and the basic principles behind the design and implementatio... more This paper presents the architecture and the basic principles behind the design and implementation of the SCATTER system, a wireless end-to-end communication system that participated in the DARPA Second Spectrum Collaboration Challenge (SC2). The focus is mainly on presenting the architecture and the supported interactions between the different components of the system in order to deliver a true dynamic collaborative spectrum allocation and usage, while coexisting with numerous unknown heterogeneous wireless technologies.
IEEE Access, 2019
With a growing number of connected devices relying on the Industrial, Scientific, and Medical rad... more With a growing number of connected devices relying on the Industrial, Scientific, and Medical radio bands for communication, spectrum scarcity is one of the most important challenges currently and in the future. The existing collision avoidance techniques either apply a random back-off when spectrum collision is detected or assume that the knowledge about other nodes' spectrum occupation is known. While these solutions have shown to perform reasonably well in intra-Radio Access Technology environments, they can fail if they are deployed in dense multi-technology environments as they are unable to address the inter-Radio Access Technology interference. In this paper, we present Spectrum Prediction Collision Avoidance (SPCA): an algorithm that can predict the behavior of other surrounding networks, by using supervised deep learning; and adapt its behavior to increase the overall throughput of both its own Multiple Frequencies Time Division Multiple Access network as well as that of the other surrounding networks. We use Convolutional Neural Network (CNN) that predicts the spectrum usage of the other neighboring networks. Through extensive simulations, we show that the SPCA is able to reduce the number of collisions from 50% to 11%, which is 4.5 times lower than the regular Multiple Frequencies Time Division Multiple Access (MF-TDMA) approach. In comparison with an Exponentially Weighted Moving Average (EWMA) scheduler, SPCA reduces the number of collisions from 29% to 11%, which is a factor 2.5 lower. INDEX TERMS Collaborative wireless networks, deep learning, machine learning, wireless MAC.
2013 Wireless Telecommunications Symposium (WTS), 2013
ABSTRACT
International Journal of Parallel Programming, 2014
In our previous work, we presented a brief analysis of the performance of the code block segmenta... more In our previous work, we presented a brief analysis of the performance of the code block segmentation procedure adopted by the 3GPP LTE Advanced (LTE-A) Standard as part of its physical layer channel coding scheme. Here, a detailed analysis of its performance is offered along with a new approach to the LTE-A code block segmentation procedure. Code block segmentation is a generic procedure applied before turbo encoding whose function is to fragment a large transport block (TB) into smaller code blocks, reducing the decoding latency of turbo decoders (Sun et al. in Integr VLSI J 44(4):305-315, 2011). Analysis showed that only 39 % of all TBs need segmentation. Results based on two different architectures, one focused on a digital signal processors and the other on an field programmable gate array are compared and discussed. A new approach for code block segmentation is presented. This new approach exhibits a speed up of more than 83 times over previous and new approaches presented here.
Procedia Technology, 2013
Like other modern systems a LTE eNodeB has a software layer and a hardware layer. Both these laye... more Like other modern systems a LTE eNodeB has a software layer and a hardware layer. Both these layers shall be connected through a fast application programming interface (API) not to compromise the performance of the whole system. When there is no hard-processor available on hardware side and the whole API must be implemented in FPGA, the design process takes too much time. This work presents a systematic way to fast code Small Cell Forum LTE eNB L1 API Definition [1] by using perl scripts. Our results indicates a series of advantages over traditional methods like a code to script character relation of 7.79 to 1, a cleaner code to support and reliability. These results points out a design methodology that can be applied on several coding abstractions or languages achieving similar results as the ones founded here.
Sensors
The demand for wireless connectivity has grown exponentially over the last years. By 2030 there s... more The demand for wireless connectivity has grown exponentially over the last years. By 2030 there should be around 17 billion of mobile-connected devices, with monthly data traffic in the order of thousands of exabytes. Although the Fifth Generation (5G) communications systems present far more features than Fourth Generation (4G) systems, they will not be able to serve this growing demand and the requirements of innovative use cases. Therefore, Sixth Generation (6G) Networks are expected to support such massive connectivity and guarantee an increase in performance and quality of service for all users. To deal with such requirements, several technical issues need to be addressed, including novel multiple-antenna technologies. Then, this survey gives a concise review of the main emerging Multiple-Input Multiple-Output (MIMO) technologies for 6G Networks such as massive MIMO (mMIMO), extremely large MIMO (XL-MIMO), Intelligent Reflecting Surfaces (IRS), and Cell-Free mMIMO (CF-mMIMO). Mo...
Anais do XL Simpósio Brasileiro de Telecomunicações e Processamento de Sinais
Resumo-Dispositivos IoT estão cada vez mais presentes em nosso dia-a-dia, tanto em contextos part... more Resumo-Dispositivos IoT estão cada vez mais presentes em nosso dia-a-dia, tanto em contextos particulares quanto em ambientes públicos. Consequentemente, a segurança deles também deve ser tratada com atenção. Após revisar diversas técnicas propostas, este trabalho propõe uma abordagem para detecção de ameaças baseada em análise de tráfego de rede, realizada por modelos de aprendizado de máquina. Após extensa experimentação e avaliação, foi possível produzir um modelo rapidamente treinável e altamente confiável, comprovando a eficácia da proposta e apontando direções para trabalhos futuros. Palavras-Chave-Internet das Coisas, cibersegurança, aprendizado de máquina.
The performance of modern wireless communication systems is highly dependent on the adoption of m... more The performance of modern wireless communication systems is highly dependent on the adoption of multiple antennas and the associated signal processing. In 5G and 6G networks, beamforming and beam management become challenging tasks due to aspects such as user mobility, increased number of antennas, and the adoption of higher frequencies. Artificial intelligence, and more specifically, machine learning, are efficient tools to reduce the complexity involved in generating beams and the overhead associated with beam management without sacrificing system performance. Therefore, AI-aided beamforming and beam management have received a lot of attention recently. This article presents a complete survey on this topic, emphasizing open problems and promising directions. The discussion includes architectural and signal processing aspects of modern beamforming and beam management. The article presents communication problems and respective solutions using centralized/decentralized, supervised/un...
Anais do XL Simpósio Brasileiro de Telecomunicações e Processamento de Sinais
The explosive emergence of wireless technologies and standards, covering licensed and unlicensed ... more The explosive emergence of wireless technologies and standards, covering licensed and unlicensed spectrum bands has triggered the appearance of a huge amount of wireless technologies, with many of them coexisting in the same band. Unfortunately, the wireless spectrum is a scarce resource, and the available frequency bands will not scale with the foreseen demand for new capacity. Certain parts of the spectrum, in particular the license-free ISM bands, are overcrowded, while other parts, mostly licensed bands, may be significantly underutilized. As such, there is a need to introduce more advanced techniques to access and share the wireless medium, either to improve the coordination within a given band, or to explore the possibilities of intelligently using unused spectrum in underutilized (e.g., licensed) bands. Therefore, in this paper, we present an open source SDR-based framework that can be employed to devise disruptive techniques to optimize the sub-optimal use of radio spectrum ...
2017 IEEE XXIV International Conference on Electronics, Electrical Engineering and Computing (INTERCON), 2017
This paper proposes an automated test framework for eNodeB's physical layer development, comp... more This paper proposes an automated test framework for eNodeB's physical layer development, comprising procedures for checking data integrity, stability and performance. The proposed framework is based on a simplified LTE MAC layer, which operates as a software element that communicates directly with the physical layer and performs mapping procedures between logical and physical channels, reception and transmission of physical layer data, user data scheduling and data exchange with mobile terminals. All above procedures are performed with no further dependency on other LTE network element, thus providing a stand-alone test framework.
Anais do XL Simpósio Brasileiro de Telecomunicações e Processamento de Sinais
Anais do XL Simpósio Brasileiro de Telecomunicações e Processamento de Sinais
IEEE Access, 2021
With the emergence of new technologies and standards for wireless communications and an increase ... more With the emergence of new technologies and standards for wireless communications and an increase in application and user requirements, the number and density of deployed wireless ad hoc networks is increasing. For deterministic ad hoc networks, Time-Division Multiple Access (TDMA) is a popular medium access scheme, with many distributed TDMA scheduling algorithms being proposed. However, with increasing traffic demands and the number of wireless devices, proposed protocols are facing scalability issues. Besides, these protocols are achieving suboptimal spatial spectrum reuse as a result of the unsolved exposed node problem. Due to a shortage of available spectrum, a shift from fixed spectrum allocation to more dynamic spectrum sharing is anticipated. For dynamic spectrum sharing, improved distributed scheduling protocols are needed to increase spectral efficiency and support the coexistence of multiple co-located networks. Hence, in this paper, we propose a dynamic distributed multi-channel TDMA (DDMC-TDMA) slot management protocol based on control messages exchanged between one-hop network neighbors and execution of slot allocation and removal procedures between sender and receiver nodes. DDMC-TDMA is a topology-agnostic slot management protocol suitable for large-scale and high-density ad hoc networks. The performance of DDMC-TDMA has been evaluated for various topologies and scenarios in the ns-3 simulator. Simulation results indicate that DDMC-TDMA offers near-optimal spectrum utilization by solving both hidden and exposed node problems. Moreover, it proves to be a highly scalable protocol, showing no performance degradation for large-scale and high-density networks and achieving coexistence with unknown wireless networks operating in the same wireless domain. INDEX TERMS Ad hoc networks, distributed scheduling protocol, exposed/hidden node, multi-channel communication, TDMA scheduling.
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Papers by Felipe Pereira de Figueiredo