Hirley Alves

Dr. Hirley Alves

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Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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11 January 2021 in IEEE Internet of Things Journal
Verified
Journal Article
Open access
Onel Luis Alcaraz LópezOnel Luis Alcaraz López
Onel Luis Alcaraz López
HAHirley Alves
Hirley Alves
RSRichard Demo Souza
Richard Demo Souza
Samuel Montejo SánchezSamuel Montejo Sánchez
Samuel Montejo Sánchez
EFEvelio Martín García Fernández
Evelio Martín García Fernández
MLMatti Latva-Aho
Matti Latva-Aho
Recent advances on wireless energy transfer (WET) make it a promising solution for powering future Internet-of-Things (IoT) devices enabled by the upcoming sixth-generation (6G) era. The main architectures, challenges and techniques for efficient and scalable wireless powering are overviewed in this article. Candidates enablers, such as energy beamforming (EB), distributed antenna systems (DASs), advances on devices' hardware and programmable medium, new spectrum opportunities, resource scheduling, and distributed ledger technology are outlined. Special emphasis is placed on discussing the suitability of channel state information (CSI)-limited/free strategies when powering simultaneously a massive number of devices. The benefits from combining DAS and EB, and from using average CSI whenever available, are numerically illustrated. The pros and cons of the state-of-the-art CSI-free WET techniques in ultralow power setups are thoroughly revised, and some possible future enhancements are outlined. Finally, key research directions toward realizing WET-enabled massive IoT networks in the 6G era are identified and discussed in detail.
19 April 2012 in IEEE Signal Processing Letters
Verified
Journal Article
Closed access
HAHirley Alves
Hirley Alves
RSRichard Demo Souza
Richard Demo Souza
MDMérouane Debbah
Mérouane Debbah
MBMehdi Bennis
Mehdi Bennis
We analyze the physical layer (PHY) security of a communication scheme consisting of a multiple antenna transmitter with a single radio frequency (RF) chain using transmit antenna selection (TAS) and a single antenna receiver, in the presence of a sophisticated multiple antenna eavesdropper. We develop closed-form expressions for the analysis of the secrecy outage probability, and we show that the PHY security can be considerably enhanced when multiple antennas are available at the legitimate transmitter. Moreover, a single RF chain multiple antenna transmitter reduces cost, complexity, size and power consumption at the expense of a slight loss in performance with respect to a multiple RF chain transmitter.
5 June 2018 in IEEE Access
Verified
Journal Article
Open access
Arliones Hoeller JuniorArliones Hoeller Junior
Arliones Hoeller Junior
RSRichard Demo Souza
Richard Demo Souza
Onel Luis Alcaraz LópezOnel Luis Alcaraz López
Onel Luis Alcaraz López
HAHirley Alves
Hirley Alves
MNMario de Noronha Neto
Mario de Noronha Neto
GBGlauber Brante
Glauber Brante
Low power wide area network (LPWAN) technologies are increasingly catching the attention of the Internet-of-Things market and have brought the need for reliable knowledge about the performance of such networks. This paper is concerned with the performance and scalability of LoRa networks, a leading LPWAN technology. Several recently published articles have analyzed the ability of LoRa networks to scale, i.e., their ability to support increased traffic and number of nodes. This paper proposes to employ message replication and gateways with multiple receive antennas to achieve, respectively, time and spatial diversity. The paper presents the proposed schemes and evaluates them through theoretical analysis and computer simulations. Results show that LoRa networks are highly sensitive to the increase in user and traffic density, but both message replication and multiple antennas can enhance performance. Message replication has an optimum number of message copies for each network configuration, and its utilization is more beneficial in low-density networks, while the use of multiple receive antennas at the gateway is always beneficial.
14 November 2022 in IEEE Transactions on Vehicular Technology
Verified
Journal Article
Open access
EEEslam Eldeeb
Eslam Eldeeb
JAJean Michel de Souza Sant' Ana
Jean Michel de Souza Sant' Ana
DPDian Echevarría Pérez
Dian Echevarría Pérez
MSMohammad Shehab
Mohammad Shehab
Nurul Huda MahmoodNurul Huda Mahmood
Nurul Huda Mahmood
HAHirley Alves
Hirley Alves
In many emerging Internet of Things (IoT) applications, the freshness of the is an important design criterion. Age of Information (AoI) quantifies the freshness of the received information or status update. This work considers a setup of deployed IoT devices in an IoT network; multiple unmanned aerial vehicles (UAVs) serve as mobile relay nodes between the sensors and the base station. We formulate an optimization problem to jointly plan the UAVs' trajectory, while minimizing the AoI of the received messages and the devices' energy consumption. The solution accounts for the UAVs' battery lifetime and flight time to recharging depots to ensure the UAVs' green operation . The complex optimization problem is efficiently solved using a deep reinforcement learning algorithm. In particular, we propose a deep Q-network, which works as a function approximation to estimate the state-action value function. The proposed scheme is quick to converge and results in a lower ergodic age and ergodic energy consumption when compared with benchmark algorithms such as greedy algorithm (GA), nearest neighbour (NN), and random-walk (RW).
16 December 2021 in IEEE Wireless Communications Letters
Verified
Journal Article
Open access
MUMuhammad Asad Ullah
Muhammad Asad Ullah
Konstantin MikhaylovKonstantin Mikhaylov
Konstantin Mikhaylov
HAHirley Alves
Hirley Alves
Long Range-Frequency Hopping Spread Spectrum (LR-FHSS) has been recently introduced into the LoRaWAN protocol specification to increase network capacity and collision robustness, and enable direct connectivity between machine devices and the Low Earth Orbit (LEO) satellites. In this letter, we first construct the analytical and simulation models for packet delivery over LR-FHSS from ground nodes to a LEO satellite, and then use the developed analytic and simulation models to generate the numerical results. Our results reveal the potential feasibility of large-scale networks, demonstrate some trade-offs between the two new LR-FHSS-based data rates for the EU region, and reveal the key reasons for packet losses.
12 May 2015 in IEEE Signal Processing Letters
Verified
Journal Article
Closed access
DOD. P. Moya Osorio
D. P. Moya Osorio
EOEdgar Eduardo Benitez Olivo
Edgar Eduardo Benitez Olivo
HAHirley Alves
Hirley Alves
JFJ. C. S. Santos Filho
J. C. S. Santos Filho
MLM. Latva-Aho
M. Latva-Aho
This letter investigates the outage probability of a variable-gain amplify-and-forward full-duplex relaying network in which not only the relaying link but also the direct link is used to convey information, thus improving the system reliability. We consider a basic three-node relaying system composed of a source, a destination, and a two-antenna relay-one antenna for transmission, one antenna for reception. Also, we consider that the full-duplex relay undergoes some residual self interference, modeled as a fading channel, and that maximal-ratio combining is employed at the destination to merge the signals from the source and relay. We derive an exact integral-form expression for the outage probability and validate this via Monte Carlo simulation. In addition, we propose a highly-accurate closed-form approximation to the outage probability, as well as a simple asymptotic expression at high signal-to-noise ratio. The use of the direct link is shown to overcome the zero diversity order inherent to full-duplex relaying.