Maria Marquezini

• Doctor of Philosophy
• Project Manager at Ericsson

Changes in telecommunication services demand the development of a new infrastructure to attend new network applications' requirements. The traditional approach to network functions running over dedicated equipment can no longer handle all the dynamics of these new services. The network function virtualization (NFV) paradigm decouples a function fro...

With the emergence of new applications driven by the popularization of mobile devices, the next generation of mobile networks faces challenges to meet different requirements. Virtual Network Functions (VNFs) have been deployed to minimize operational costs and make network management more flexible. In this sense, strategies for VNF placement can im...

This work presents an adaptive hybrid signal precoding strategy for Cell-Free (CF) Massive multiple-input multiple-output (MIMO) systems. The proposed solution exploits the advantages of both distributed and centralized signal processing schemes to perform precoding. In our proposal, some access points (APs) are dynamically configured to be used in...

This work proposes a scalable access point (AP) selection framework based on a competitive mechanism that operates in two stages. Initially, the user equipment (UE) connects to an intermediate AP cluster, where a matched-decision among the APs and UEs establishes the best connection in terms of large-scale fading and prevents UEs from being dropped...

Human-robot collaboration has gained a notable prominence in Industry 4.0, as the use of collaborative robots increases efficiency and productivity in the automation process. However, it is necessary to consider the use of mechanisms that increase security in these environments, as the literature reports that risk situations may exist in the contex...

This work describes the development of RBOT, a robot-driven radio base station maintenance system. RBS deployment and maintenance tasks are increasing both in complexity and density with the introduction of 5G microcells. The main objective behind our application is to reduce maintenance costs by developing an integrated system based on a robotic a...

Human-robot collaboration has gained a notable prominence in Industry 4.0, as the use of collaborative robots increases efficiency and productivity in the automation process. However, it is necessary to consider the use of mechanisms that increase security in these environments, as the literature reports that risk situations may exist in the contex...

IoT devices suffer from resource limitations, such as processor, RAM, and disc storage. These limitations become more evident when handling demanding applications, such as deep learning, well-known for their heavy computational requirements. A case in point is robot pose estimation, an application that predicts the critical points of the desired im...

The network function virtualization (NFV) paradigm is an emerging technology that provides network flexibility by allowing the allocation of network functions over commodity hardware, like legacy servers in an IT infrastructure. In comparison with traditional network functions, implemented by dedicated hardware, the use of NFV reduces the operating...

The introduction of technological innovations is essential for accident mitigation in work environments. In a human-robot collaboration scenario, the current number of accidents raises a safety problem that must be dealt. This work proposes an intelligent system that aims to address such problems using deep and machine learning techniques. More spe...

Human–robot collaboration is increasingly present not only in research environments, but also in industry and many contemporary day-to-day activities. There is a need for the automation of tasks ranging from the simplest to the most complex ones. The insertion of robotic arms provides a considerable step useful in achieving this goal. In this conte...

With the popularity of mobile devices, the next generation of mobile networks has faced several challenges. Different applications have been emerged, with different requirements. Offering an infrastructure that meets different types of applications with specific requirements is one of these issues. In addition, due to user mobility, the traffic gen...

The network function virtualization (NFV) paradigm is an emerging technology that provides network flexibility by allowing the allocation of network functions over commodity hardware, like legacy servers in an IT infrastructure. In comparison with traditional network functions, implemented by dedicated hardware, the use of NFV reduces the operating...

For an autonomous system to perform maintenance tasks in a networking device or a radio base station (RBS), it has to deal with a series of technological challenges ranging from identifying hardware-related problems to manipulating connectors. This paper describes the development of a robot maintenance system dedicated to detect and resolve faulty...

Globalization, digitalization, and urbanization are progressing at a fast pace in cities and regions across the world. New technologies and innovations typically reach urban regions first, where Return on Investment (ROI) tends to be higher than in remote or rural areas, which are characterized by low population densities, low potential revenues, a...

A data center infrastructure is composed of heterogeneous resources divided into three main subsystems: IT (processor, memory, disk, network, etc.), power (generators, power transformers, uninterruptible power supplies, distribution units, among others), and cooling (water chillers, pipes, and cooling tower). This heterogeneity brings challenges fo...

The next generation of mobile communication system will allow a plethora of new services and use cases. By offering support for high throughput connections, low latency response and massive number of connections, the fifth generation of the mobile network will trigger applications unseen in any other network. However, one important application scen...

Autonomous Vehicles (AV) are expected to bring considerable benefits to society, such as traffic optimization and accidents reduction. They rely heavily on advances in many Artificial Intelligence (AI) approaches and techniques. However, while some researchers in this field believe AI is the core element to enhance safety, others believe AI imposes...

Autonomous Vehicles (AV) are expected to bring considerable benefits to society, such as traffic optimization and accidents reduction. They rely heavily on advances in many Artificial Intelligence (AI) approaches and techniques. However, while some researchers in this field believe AI is the core element to enhance safety, others believe AI imposes...

We have calculated the electronic structure of spherical PbS, PbSe, and PbTe quantum dots using a four-band envelope-function formalism that accounts for band anisotropy. By comparing our results with an analytical calculation that assumes a spherical approximation of the (k) over right arrow.(p) over right arrow Hamiltonian, we show that the effec...

Mean-field, Hartree-Fock theory has been successful in explaining many nonlinear optical experiments in semiconductors. But recently experiments have shown important cases where the mean-field theory (the semiconductor Bloch equations) fails. One such case is bulk GaAs in a strong magnetic field. Here the exciton-exciton interaction can be tuned by...

Summary form only given. In the absence of strong damping, the coupling between the GaAs exciton and the electromagnetic field leads to the creation of the exciton-polariton. The polariton dispersion curve has been studied by techniques such as resonant Brillouin scattering. But the longitudinal-transverse splitting (Δ_LT) being very smal...

Fourier transform spectral interferometry is applied to measure both amplitude and phase of the electric field in different types of semiconductor nanostructures, thus determining the real and imaginary parts of the dielectric function. The importance of measuring the phase is shown and discussed in three studies. First, the phase measurement is us...

We investigate the effects of interface localization due to microroughness in a sample presenting a quantum well and a quantum wire. The magnetoshift of the emission lines measured at different temperatures are analysed using a model where the average effect of the microroughness is represented by a Gaussian defect. We obtain a quantitative estimat...

The possibility of using a minimal-volume photoacoustic cell to perform spectroscopy of samples is discussed. It is shown that this alternative signal-to-noise-enhanced photoacoustic configuration allows one to obtain both absorption and transmission spectra with minimal experimental arrangement and cell machining requirements. The theoretical mode...

Summary form only given. We present applications of phase/amplitude spectroscopy in GaAs-based semiconductor structures, using Fourier Transform Spectral Interferometry. This technique allows one to measure both phase and amplitude of an optical pulse transmitted by the sample and therefore provides simultaneous absorption and refractive index meas...

We present simultaneous measurement of the refractive index and absorption coefficient in a AlGaAs/GaAs multiple quantum well structure near the band gap by Fourier transform spectral interferometry. Both quantities were measured across heavy- and light-hole excitons for temperatures ranging from liquid helium to room temperature. The experimental...

We studied the effects of interface localization due to microroughness in a sample presenting a quantum well and a quantum wire. We measured the magnetoluminescence at different temperatures and analyzed the results with a model where the average microroughness, the magnetic field, and the excitonic effects are treated within the same level of appr...

We study the effects of photocarrier density on a magnetically induced Fano resonance in GaAs, using a combined phase-amplitude transmission spectroscopy technique. By comparing our results to an extension of the Fano model we measure the relative contributions of two, usually undistinguished, effects of the photocarriers: the screening of the inte...

We have observed the suppression of Fano resonances in epitaxial layers of GaAs in a magnetic field due to discretization of the quasi-continuum by quantum confinement. Our observations can be explained using a simple “picket fence” model in which the density of states can be adjusted to model the different thickness epitaxial layers. The suppressi...

The results of femtosecond four-wave mixing experiments in bulk GaAs in high magnetic field are presented. At high magnetic field and low density, our measurements are dominated by features that cannot be explained by the semiconductor Bloch equations. These features are due to exciton-exciton correlations and are accounted for by a calculation bas...

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We present here the first combined phase-amplitude measurement on a semiconductor microcavity. The phase reveals surprising behavior under confinement by a magnetic field or in a pump-probe experiment which is not clearly seen in the amplitude.

The first experimental and theoretical investigations of the effect of increasing two-dimensional confinement on the mechanisms that govern the nonlinear optical response of Lorentzian excitons (LX), is presented. Femtosecond (fs) coherent four-wave mixing (FWM) under high magnetic field is used for studying the model material, gallium arsenide (Ga...

We present a study of carrier dynamics in GaAs during and just after creation by ultrashort laser pulses. We observe a quasi-instantaneous spread of the carrier population in momentum-energy space. Attempts to fit the scattering rates in the relaxation time approximation result in parameters outside the range of validity of the theory. We interpret...

Summary form only given. We have demonstrated that application of a magnetic field is a powerful tool to investigate the interplay between the fundamental processes governing the nonlinear optical response of excitons. We explore these processes in an optically thin, 0.25 /spl mu/m, bulk GaAs sample by time-resolved and frequency-resolved four wave...

We present a study on the exciton dynamics in a thin quantum well grown with self-assembled islands with thicknesses ranging from 1 to 5 ML. The exciton dynamics is investigated by combinining continuous-wave and time-resolved photoluminescence measurements as a function of temperature. We analyze the exciton dynamics through a system of rate equat...

We demonstrate the possibility of obtaining two-dimensional confinement in semiconductor heterostructures through direct control of the growth kinetics. The confinement is characterized through the exciton behavior in the presence of a magnetic field applied following the symmetry of the structure. The comparison between the magneto-optical propert...

We present an investigation of the exciton dynamics in a single quantum well with self-assembled islands. We combine continuous-wave and time-resolved luminescence measurements as a function of the temperature to obtain quantitative information on the recombination processes in the well. The obtained radiative recombination times indicate that exci...

100-fs time- and frequency-resolved four-wave mixing in GaAs at T=1.6K under magnetic field, 0â¤|{rvec B}|â¤12T, is used for investigating how magnetic confinement modifies the processes that govern the manybody nonlinearities of the Lorentzian excitons.

We investigated the optical properties of lattice‐matched InGaAs/InP quantum wells grown by metalorganic molecular beam epitaxy on top of patterned InP buffer layers with elongated features along the [01¯1] direction. The resulting quantum wells present a periodic thickness variation following the elongated features. Low temperature luminescence me...

An open-cell photoacoustic (OCPA) spectroscopic technique is described which can assess genetically rooted differences in the response of live specimens of corn (Zea Mays L.) to the toxic action of aluminium. Specimens from a susceptible and a tolerant inbred line were examined. The differences in their OCPA in vivo leaf spectra were evident and an...