Jose Vieira

Jose Vieira
University of Aveiro | UA · Department of Electronics, Telecommunications and Informatics

About

145
Publications
20,311
Reads
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881
Citations
Citations since 2017
31 Research Items
542 Citations
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2017201820192020202120222023020406080100
2017201820192020202120222023020406080100
2017201820192020202120222023020406080100

Publications

Publications (145)
Article
Full-text available
Doppler-based radar systems have been seen as a promising tool to assess vital signs, since they are capable to monitor the respiratory and cardiac signal remotely, by measuring the chest-wall displacement. However, due to the spectral overlap of these signals, their proper separation is a challenging task. In this paper, we demonstrate the effecti...
Conference Paper
Recently, the number of systems based on FMCW radar technology has been increasing dramatically, due in part to the availability of low-cost development and evaluation kits that permit rapid prototyping and testing of radar-based applications. In a real scenario where it is possible to have multiple radars emitting simultaneously, interference betw...
Article
Full-text available
The ability to remotely assess vital signs using radar systems may potentialize the healthcare systems, since it does not require any direct interaction with the subject. Nonetheless, these systems present inherent challenges that could compromise the accuracy of the vital signs parameters. For instance, there is a lack of resolution on the cardiac...
Article
Full-text available
Radar systems have been widely explored as a monitoring tool able to assess the subject’s vital signs remotely. However, their implementation in real application scenarios is not straightforward. Received signals encompass parasitic reflections that occur in the monitoring environment. Generally, those parasitic components, often treated as a compl...
Article
Full-text available
A bio-radar system is presented for vital signs acquisition, using textile antennas manufactured with a continuous substrate that integrates the ground plane. Textile antennas were selected to be used in the RF (Radio Frequency) front-end, rather than those made of conventional materials, to further integrate the system in a car seat cover and thus...
Article
Full-text available
Non-contact vital signs monitoring has a wide range of applications, such as in safe drive and in healthcare. In mental health care, the use of non-invasive signs holds a great potential, as it would likely enhancethe patient’s adherence to the use of objective measures to assess their emotional experiences, henceallowing for more individualized an...
Article
Full-text available
Cardiopulmonary activity measured through contactless means is a hot topic within the research community. The Doppler radar is an approach often used to acquire vital signs in real time and to further estimate their rates, in a remote way and without requiring direct contact with subjects. Many solutions have been proposed in the literature, using...
Article
Full-text available
The bio-radar system can measure vital signals accurately, by using the Doppler effect principle, which relates the received signal properties to the distance change between the radar antennas and the subject chest-wall. These systems have countless applications, from short range detection to assist in rescue missions, to long-term applications as...
Chapter
Full-text available
The use of smart devices in buildings is many times compromised by its form and size. Smart devices are composed of several components including sensors, boards, batteries, processing units, and antennas. However, the form and size of the smart devices are usually limited due to antenna restrictions. In this paper, we propose the architecture of a...
Conference Paper
We demonstrate the use of 1-bit delta-sigma modulation for digital generation and transmission while performing an analog mm-wave generation using optical heterodyning. After 20 km fiber transmission, EVMs of ∼3.7% are measured for 100 Mbaud 16, 64, and 256QAM signals.
Conference Paper
Full-text available
This paper presents the design methodology used to specify a Human-in-the-Loop Cyber-Physical System (HITL-CPS) for online monitoring and active mitigation of the indoor radon gas concentration in non-residential granitic buildings with regular human occupation restricted to a work schedule, such as public buildings like administration offices, sch...
Article
Contiguous/noncontiguous carrier aggregation (CA) is one of the key features from 4G systems, which is expected to be evolved within 5G technologies. Thus, there is a need for the development of flexible, agile, and reconfigurable radio transceivers with a native support for the integration of multiple bands and multiple standards. All-digital radi...
Article
Full-text available
This article describes and evaluates the performance of DETIboot, a system conceived for securely deploying temporary Linux systems into countless receiving hosts close enough to a Wi-Fi DETIboot server. This system was created with the ultimate goal of installing, in numerous students’ laptops and just-in-time, special Linux distributions for bein...
Article
In this article the concept of a fully electronic beamforming antenna array for radar systems based on a SDR architecture is proposed and experimentally evaluated in an anechoic chamber. The system uses 2 software defined radio (SDR) transceivers with 4 independently controlled transmitters, allowing an individual digital control of both amplitude...
Conference Paper
In this work, we demonstrate a real-time architecture for enabling the use of all-digital transmitters in mm-wave frequency bands. We propose the combination of delta-sigma modulation techniques and electro-optical upconversion stages to ease the stringent requirements in the design of RF front-ends. In our proof-of-concept demonstration, the real-...
Article
The migration from analog to digital television (TV) broadcasting has introduced significant improvements in terms of spectral efficiency. As a result, the number of radio channels required to ensure equivalent coverage has been dramatically reduced [1]. This efficiency gain has allowed the release of a valuable portion of spectrum (previously assi...
Article
Cardiopulmonary monitoring without any physical contact with the human body has several applications, such as health monitoring of bedridden patients, monitoring sleeping, or even for rescuing people from collapsed buildings. The Bio-Radar system can accurately measure vital signals by using the principle of the Doppler effect, which relates the pr...
Article
Real-time frequency agility is one of the key limitations of current all-digital transmitters (ADTs). In this paper, to address this problem, an ADT based on direct-RF generation is proposed and implemented in a field-programmable gate array (FPGA). To achieve this, the pulse encoding is performed after the digital upconversion, which presents chal...
Conference Paper
In this paper, we present a novel architecture for an All-Digital FPGA-based Antenna Array RF Transmitter. The proposed method reduces the complexity inherent to the design of antenna arrays by removing external Digital-to-Analog Converters and external analog upconversion stages. With such a concept, the analog front-end complexity is highly reduc...
Conference Paper
In this article we propose a subtractive histogram clustering method to estimate the number of LTE users based on the uplink energy probability density distribution sensed by an RF front-end. The energy of the signal is estimated and its histogram is analyzed to determinate the number of different distributions. As the energy estimation of the sens...
Book
Full-text available
This book presents an indoor acoustic simulator for ultrasonic signals using a hybrid method based on the virtual sources method with ray tracing validation. The simulator takes into account the multiple reflections produced by the walls and other obstacles, the beam pattern of the transducers and the acoustic wave propagation losses. We have also...
Conference Paper
This paper provides an overview on recent advances on all-digital transceivers, as a promising approach to the ideal Software-Defined Radio concept. Several techniques and architectural optimizations are discussed to improve the coding efficiency, spectral purity, signal to noise ratio, bandwidth and flexibility.
Article
In this paper, a new architecture for designing tunable single- and dual-band radio-frequency fully digital transmitters is proposed and validated. The proposed architecture excels the state of the art in terms of simplicity and flexibility. While its short critical path leverages the use of equivalent polyphase decomposition techniques to increase...
Article
In this article we address a novel method for spectrum sensing, based on the Expectation Maximization algorithm applied to the histogram of the moving average signal power. The method enables the estimation of the number of active users in a given frequency band, the power received from each user, the occupied time slots and the front-end noise flo...
Conference Paper
Full-text available
This paper proposes an algorithm to design band-limited Orthogonal Frequency Division Multiplexing (OFDM) pulses for accurate time-of-flight ranging in acoustic-based localization systems. The proposed algorithm is capable to generate OFDM pulses with higher energy when compared with other common pulse design approaches with similar characteristics...
Article
Full-text available
In this article we discuss a novel approach to Bio-Radar, contactless measurement of bio-signals, called Cognitive Bio-Radar. This new approach implements the Bio-Radar in a Software Defined Radio (SDR) platform in order to obtain awareness of the environment where it operates. Due to this, the Cognitive Bio-Radar can adapt to its surroundings in o...
Conference Paper
DETIboot is an over-the-air, �le distribution system that allows a teacher to gain control over students' personal laptops during exams, by distributing a properly hardened Linux operating system image. In this scenario, a student could boot the hardened image over a Virtual Machine, being able to explore the hosting system while doing the exam on...
Article
Full-text available
Context Forest management has impacts on bats worldwide. Given that many forest bats are threatened and that bats are important providers of ecosystem services, understanding the effects of forest management practices on their activity is fundamental for the implementation of conservation measures. Despite these important issues, studies on the eff...
Conference Paper
The File Broadcast Protocol (FBP) was developed as a part of the DETIboot system. DETIboot allows a host to broadcast an operating system image through an 802.11 wireless network to an arbitrary number of receivers. Receivers can load the image and immediately boot a Linux live session. The initial version of FBP had no security mechanisms. In this...
Conference Paper
In several scenarios, such as in training and education, it is frequently important to distribute large files to many clients, e.g., operating system boot images or raw data files. To carry out such distribution efficiently, we use wireless broadcast and Fountain Codes with low density random encoding to tolerate network packet losses. In particula...
Conference Paper
There are many situations, such as in training and education, in which there is a frequent need to distribute large files to many clients, e.g., operating system boot images or raw data files. To carry out such distribution efficiently, we use wireless broadcast and a hybrid coding technique that combines forward coding using weak LT Codes with a f...
Conference Paper
Full-text available
The ability to locate objects and people indoors remains a substantial challenge and effective centimeter-level smartphone-based indoor positioning, is still an open problem. Conventional smartphones have recently been used for centimeter-level indoor positioning by performing acoustic Time-of-Flight (ToF) ranging. Due to limitations in the smartph...
Conference Paper
Full-text available
In this work the Near-Far problem is characterized in the context of an acoustic local positioning system (ALPS). First, a simple energy normalization algorithm is presented to identify the Near-Far situation and also to resolve the signal detection in the case of non-overlapping receptions. Then, an improved signal interference cancellation (ISIC)...
Article
In this brief, we present a new reconfigurable filtering technique for all-digital transmitters using signal interference and cancellation. The proposed method allows the change of some filtering characteristics digitally. This technique is used to reduce the quantization noise from the all-digital transmitter's output, reducing the analog output f...
Conference Paper
In this article we describe a novel process for blind detection in spectrum sensing taking advantage of the cyclostationary features of any digital modulation that uses a finite number of distinct signals to represent digital data. Traditional models only look at any peak in a cyclic spectrum that satisfies a given threshold, in this method we take...
Conference Paper
In this work we propose a wideband spectrum sensing system based on hybrid filter banks. The polyphase implementation of the digital counterpart of the filter bank can be modified to include a parallelized version of discrete Fourier transform algorithm (FFT) avoiding this way any sampling rate expanders. In this work we show how to incorporate the...
Conference Paper
Full-text available
This work presents a system conceived to deploy temporary Linux systems into an unlimited number of client hosts using a Wi-Fi source station (DETIboot server). The ultimate goal of this system is to provide a simultaneous and just-in-time installation of a custom Linux distribution on several tens of laptops for being used in classes or exams. DET...
Article
Full-text available
Experiments with captive bats need a flight room that is acoustically neutral, especially when recording and analysing bat calls or the response of bats to certain sound stimuli. Our aim was to identify an isolation material with the best quality–price relationship to acoustically coat such a flight room. For this, we built a flight room divided in...
Chapter
Conventional radios can be seen as analog signal processing systems. The appearance of digital signal processors (DSPs) has opened up the possibility of digitizing parts of the signal processing performed in a radio, namely the signals in the final stages having a narrow bandwidth. With the increase of the processing power of the DSPs and field pro...
Conference Paper
In this work we propose a system to efficiently broadcast large files at maximum Wi-Fi transmission speed over an ad-hoc network using Fountain codes. With this type of rateless encoding we were able to avoid the feedback channel from the receivers and the need to retransmit the lost packets. This way it is possible to take advantage of the full ba...
Article
Full-text available
In this paper we propose a reliable acoustic indoor positioning system fully compatible with a conventional smartphone. The proposed system takes advantage of the smartphone audio I/O and its processing capabilities to perform acoustic ranging in the audio band using non-invasive audio signals and it has been developed having in mind applications t...
Chapter
In this work we propose a method based on compressive sensing (CS) for estimating the spectrum of a signal written as a linear combination of a small number of sinusoids. In practice one deals with signals with finite-length and so the Fourier coefficients are not exactly sparse. Due to the leakage effect in the case where the frequency is not a mu...
Conference Paper
This paper presents the architecture and implementation of an FPGA-based all digital transmitter with a baseband sampling rate of 1 GHz. Hardware complexity and operation frequency analysis are performed to find the best hardware topology to improve the transmitter performance. The used polyphase decomposition techniques for delta sigma modulators...
Conference Paper
This paper presents a new radio-over-fiber system that uses an all-digital transmitter architecture enabling a very simple remote radio head comprised only by an amplifying stage, a bandpass filter and an antenna. An all-digital transmitter is proposed to implement a flexible centralized digital radio, able to perform the baseband processing and tr...
Conference Paper
Full-text available
Neste trabalho é apresentado um sistema de realidade aumentada áudio 3D (binaural) para dispositivos móveis iOS. O sistema tira partido dos recursos de processamento e entrada/saída existentes num dispositivo iOS para obter a posição do utilizador recorrendo a um sistema de localização acústico e da unidade de medição inercial (IMU) existente no di...
Article
The requirement of wireless access by novel telecommunications and remote-sensing applications, such as Internet-in-mobile services and ultrawideband (UWB) radar systems, is continuously growing in western society but also in countries with big and emerging economies such as China, Brazil, India, and even some African nations [1], [2]. As a consequ...
Conference Paper
In this paper, a new class of microstrip filter with dual-band lowpass/bandpass response is reported. It consists of a periodic-type circuit configuration made up of an original firstorder double-band lowpass/bandpass filtering cell. The operating principle of this lowpass/bandpass filter structure is explained, and guidelines for its systematic de...
Article
The basic theories of compressed sensing (CS) turn around the sampling and reconstruction of 1-D signals. To deal with 2-D signals (images), the conventional treatment is to convert them into1-D vectors. This has drawbacks, including huge memory demands and difficulties in the design and calibration of the optical imaging systems. As a result, in 2...
Article
In this work we show that coding with a binary block angular matrix with some extra coupling rows can achieve similar results to codes that use other random binary matrices. Moreover, we also show that it is possible to use sparse block diagonal matrices and get the same results obtained with a dense equiprobable binary random matrix. The block dia...
Conference Paper
Full-text available
Este artigo apresenta os últimos desenvolvimentos do projeto de um sistema para reproduzir áudio binaural sem necessidade de auscultadores convencionais. O sistema utiliza altifalantes paramétricos e técnicas de beamforming digital, implementadas em FPGA, para produzir feixes áudio e controlar a sua direção em tempo real.
Conference Paper
In this work we present a bat monitoring system for wind farms. The proposed system includes a thermal camera and an ultrasound acquisition device to detect and record bats that come into the detection range of each one of these devices. All events are registered simultaneously with climatic variables and sent to a central database using 3G/4G. The...
Conference Paper
Full-text available
In this paper we propose a reliable acoustic indoor positioning system fully compatible with the hardware of a conventional smartphone. The proposed system takes advantage of the smartphone audio I/O and processing capabilities to perform acoustic ranging in the audio band using non-invasive audio signals and it has been developed having in mind ap...