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Simulating Poisson Networks Efficiently
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When I first started my Ph.D. I learned about modeling large wireless network using point processes. They allow you to obtain tractable mathematical models that scale well with the size of the network. The most commonly used model in wireless networks is the homogeneous Poisson point proces (PPP), because it has a reasonable assumption about the network geometry and leads to tractable models. To briefly introduce the concept, say we have a set of two dimensional points randomly distributed in , such that for every compact set . The set of points is a HPPP if:
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publications
Uma metodologia para geraçao de sequências aleatórias usando mapas caóticos
Published in XXXIII Simpósio Brasileiro de Telecomunicaçoes (SBrT 2015), Juiz de Fora, 2015
Geradores de números aleatórios são amplamente utilizados em aplicações científicas e tecnológicas. Particularmente em criptografia, são empregados em sistemas de chave pública, assinatura digital. Neste trabalho, apresentamos uma metodologia para o projeto destes geradores a partir de mapas caóticos baseada em duas técnicas: salto de amostras e discretização codificada variante no tempo. Mostramos que o procedimento possui alta taxa de geração de bits, além de dispensar pósprocessamento para melhoria de suas propriedades aleatórias. Validamos o método proposto empregando o teste NIST. Por fim, apresentamos um circuito que implementa o mapa caótico analisado neste trabalho.
Recommended citation: Artiles, J.A., Chaves, D.P., Evangelista, J.V. and Pimentel, C., "Uma metodologia para geraçao de sequências aleatórias usando mapas caóticos." XXXIII Simpósio Brasileiro de Telecomunicaçoes (SBrT 2015), Juiz de Fora, pp.1-5. #
Spectral analysis of a chaotic map based on the hyperbolic tangent function
Published in Journal of Communication and Information Systems, 2016
This work generalizes the chaotic map recently introduced by the authors with the addition of two new control parameters. The Lyapunov exponent is employed to analyze the chaotic dynamics of the proposed map. The spectral characteristics of chaotic signals generated by this map as a function of the control parameters are also investigated. The proposed map can be used in symbolic dynamics based communication systems with advantages over current approaches based on piecewise linear maps.
Recommended citation: Souza, C., Evangelista, J.V., Chaves, D.P. and Pimentel, C., 2016. "Spectral analysis of a chaotic map based on the hyperbolic tangent function." Journal of Communication and Information Systems, 31(1). https://jvce92.github.io/files/2016-spectral-analysis-of-a-chaotic.pdf
Physical-layer authentication Using chaotic maps
Published in Journal of Communication and Information Systems, 2016
Message authentication, which ensures that a received message comes from its acclaimed sender, is of fundamental importance for secure communication systems. We consider in this work a physical layer authentication system employing tag signals embedded in the message to provide a robust au- thentication method. This work diverges from previous work in the area when it comes to the tag generation method. While the previous works use methods based on cryptographic hash functions or on the channel side information our system employs unidimensional chaotic maps to generate these tags. Due to the loss of information about the initial condition of chaotic maps, we show that they are strong candidates for the tag generation process. We prove that chaotic tags provide a positive lower bound on the unconditional security of the system. Additionally, we calculate the probability of suc- cess for three possible attacks to the authentication system: impersonation, substitution and replay. Finally, we analyze how the system parameters affect these probabilities and some performance met- rics (bit error rate, outage probability, probability of false negative) and explore the tradeoff between security and performance in order to provide guidelines to design the system.
Recommended citation: Evangelista, Joao V. C., 2016, "Physical-layer authentication Using chaotic maps." M.Sc. Thesis, Universidade Federal de Pernambuco. https://jvce92.github.io/files/msc-thesis.pdf
Analysis of the cell association for decoupled wireless access in a two tier network
Published in IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2017
In this paper, we analyze the association of a user terminal in a two-tier network (ie, macrocells and millimeter wave small cells). We assumed a decoupled wireless access where a user terminal has the liberty to choose different base stations (BSs) in uplink and downlink based on the received power and the channel quality. A practical blockage model where a human body is a blockage to millimeter wave (mmW) is considered. An in-depth simulation study is done to explore the effectiveness of decoupled wireless access in a crowded environment. In addition to that, a detailed analysis on the intuitiveness and the mathematical tractability of the blockage model used is also provided. In the end, few research questions on the efficacy of decoupled wireless access are raised in this paper.
Recommended citation: Z. Sattar, J. V. C. Evangelista, G. Kaddoum and N. Batani, "Analysis of the cell association for decoupled wireless access in a two tier network," 2017 IEEE 28th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), Montreal, QC, 2017, pp. 1-6. https://jvce92.github.io/files/2017-analysis-of-the-cell-association.pdf
Fairness and Sum-Rate Maximization via Joint Channel and Power Allocation in Uplink SCMA Networks
Published in arXiv preprint arXiv:1805.11722, 2018
In this work, we consider a sparse code multiple access uplink network, where J users simultaneously transmit data over K subcarriers, such that J > K , with a constraint on the power transmitted by each user. To jointly optimize the codebook assignment and the transmitted power per subcarrier, two new iterative algorithms are proposed, the first one aims to maximize the sum-rate (Max-SR) of the network, while the second aims to maximize the minimum rate (Max-Min). In both cases, the optimization problem is of the mixed-integer nonlinear programming (MINLP) type, with non-convex objective functions. To address this issues, we employ an alternating optimization framework, where the codebook allocation problem is decoupled from the power allocation into two subproblems, and they are solved in an iterative alternating fashion. These subproblems are non-convex, therefore, we employ a sequential convex programming (SCP) method to solve them. An analysis of the convergence of the algorithms is provided. A comparison of the sum-rate and Jain’s fairness index of the novel algorithms with three other algorithms proposed in the literature is presented for varying power budgets. The Max-SR algorithm outperforms the others in the sum-rate sense, while the Max-Min outperforms them in the fairness sense, achieving near perfect fairness.
Recommended citation: Evangelista, J.V., Sattar, Z., Kaddoum, G. and Chaaban, A., 2018. "Fairness and Sum-Rate Maximization via Joint Channel and Power Allocation in Uplink SCMA Networks." arXiv preprint arXiv:1805.11722. https://jvce92.github.io/files/2018-fairness-and-sum-rate-maximization.pdf
Spectral Efficiency Analysis of the Decoupled Access for Downlink and Uplink in Two Tier Network
Published in arXiv preprint arXiv:1808.02523, 2018
This paper analyzes the efficacy of decoupled wireless access in a two-tier heterogeneous network. The decoupled wireless access and its performance benefits have been studied in different scenarios recently. In this paper, an in-depth analysis on its efficacy from spectral efficiency perspective is provided. To achieve this task, (i) new closed form expressions for probability of association of user equipment with different tiers employing different frequency bands (i.e., microwave and millimeter wave) with different pathloss exponents are derived using univariate Fox’s H-functions; (ii) Distributions of the distance to the serving base stations are also derived; (iii) Exact expressions of spectral efficiency for different association cases are further obtained in a closed form using bivariate Fox’s H-functions. Furthermore, rigorous simulation results are provided which validate the aforementioned analytical results. In addition to that, a detailed discussion on the decoupling gain of decoupled wireless access and its efficacy is also provided. Lastly, despite the improvement provided by the decoupled wireless access, which is evident from the results presented in this paper, few questions are raised on its pragmatic value.
Recommended citation: Z. Sattar, J. V. C. Evangelista, G. Kaddoum and N. Batani,, 2018. "Spectral Efficiency Analysis of the Decoupled Access for Downlink and Uplink in Two Tier Network." arXiv preprint arXiv:1808.02523 https://jvce92.github.io/files/2018-spectral-efficiency-analysis-of-the-decoupled-access.pdf
talks
Talk 1 on Relevant Topic in Your Field
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Conference Proceeding talk 3 on Relevant Topic in Your Field
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teaching
Digital Circuits Teaching Assistant
Undergraduate Course, Universidade Federal de Pernambuco, Department of Electronics and Systems, 2013
I’ve taught the digital circuits lab classes and graded the student participation and reports. The focus of the lab was on the design and synthesis of digital circuits using the VHDL description language targeting Altera FPGAs.
Analog Circuits Teaching Assistant
Undergraduate Course, Universidade Federal de Pernambuco, Department of Electronics and Systems, 2014
I’ve taught the analog circuits lab classes and graded the student participation and reports. The focus of the lab was on the analysis, simulation and design of:
- Differential amplifiers
- Multistage BJT and CMOS amplifiers
- Stable current and voltage sources I’ve also introduced the students to SPICE simulation through the ngspice software.