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About

About

Joana Tavares completed the Master Course in Electrical and Computer Engineering in 2012 and the Doctoral Programme in Telecommunications (MAP-tele) in 2021, both at the Faculty of Engineering of the University of Porto (FEUP). She has been a research fellow since 2014 in the Optical and Electronic Technologies (OET) group from the Centre of Telecommunications and Multimedia at the Institute for Systems and Computer Engineering, Technology and Science (INESC TEC). Currently, she is an Invited Assistant Professor at the Department of Electrical and Computer Engineering of FEUP. Her main research interests include optical fiber communication systems and smart antenna arrays.

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Details

Details

  • Name

    Joana Santos Tavares
  • Role

    Assistant Researcher
  • Since

    13th February 2012
005
Publications

2023

Misalignment-Resilient Propagation Model for Underwater Optical Wireless Links

Authors
Araujo, JH; Tavares, JS; Marques, VM; Salgado, HM; Pessoa, LM;

Publication
SENSORS

Abstract
This paper proposes a multiple-lens receiver scheme to increase the misalignment tolerance of an underwater optical wireless communications link between an autonomous underwater vehicle (AUV) and a sensor plane. An accurate model of photon propagation based on the Monte Carlo simulation is presented which accounts for the lens(es) photon refraction at the sensor interface and angular misalignment between the emitter and receiver. The results show that the ideal divergence of the beam of the emitter is around 15 degrees for a 1 m transmission length, increasing to 22 degrees for a shorter distance of 0.5 m but being independent of the water turbidity. In addition, it is concluded that a seven-lense scheme is approximately three times more tolerant to offset than a single lens. A random forest machine learning algorithm is also assessed for its suitability to estimate the offset and angle of the AUV in relation to the fixed sensor, based on the power distribution of each lens, in real time. The algorithm is able to estimate the offset and angular misalignment with a mean square error of 5 mm (6 mm) and 0.157 rad (0.174 rad) for a distance between the transmitter and receiver of 1 m and 0.5 m, respectively.

2023

Sigma-Delta Modulation for Enhanced Underwater Optical Wireless Communication Systems

Authors
Araújo J.H.; Rocha H.J.; Tavares J.S.; Salgado H.M.;

Publication
International Conference on Transparent Optical Networks

Abstract
This paper presents an experimental investigation of sigma-delta modulation (SDM) as a means of improving the performance of underwater optical communication systems. The study considers the impact of the key parameters of SDM, including oversampling ratio, the system's signal-to-noise ratio, bandwidth, and optical link distance. The results of this study provide insights into the design and optimization of SDM-based underwater optical communication systems, paving the way for future research in this field. A fully digital solution, albeit operating at a lower bit rate than previously published OFDM counterparts, provides immunity against nonlinearities of the system and robustness to noise, which is relevant in harsh environments. Moreover, the proposed solution based on a first-order bandpass SDM architecture avoids the employment of a DAC at the receiver, simplifying its operation and reducing costs. An experimental investigation is carried out for the transmission of 16-QAM over SDM, and a transmission distance of 4.8 m over the underwater channel is achieved with a maximum transmission rate of 400 Mbit/s with an MER of 28 dB.

2022

A Gaussian Window for Interference Mitigation in Ka-band Digital Beamforming Systems

Authors
Tavares, JS; Avelar, HH; Salgado, HM; Pessoa, LM;

Publication
2022 13th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2022

Abstract
This paper proposes the use of a Gaussian window on the array factor as an interference mitigation method, aiming to avoid the computational complexity of the MVDR algorithm at the cost of a slight performance reduction. We show that by optimizing the parameters of the Gaussian window, it is possible to effectively mitigate the interfering signal if it is received within a certain angular range from the desired signal, while being still effective beyond that range. Finally, we show that the effectiveness of this approach is maintained across the full frequency reception range of the Ka-band, and confirm its validity using 8 × 8 and 16 × 16 array sizes. © 2022 IEEE.

2021

iBROW

Authors
Tavares, JS; Watson, S; Zhang, W; Figueiredo, JML; Cantu, HI; Wang, J; Al-Khalidi, A; Kelly, AE; Wasige, E; Salgado, HM; Pessoa, LM;

Publication
Springer Series in Optical Sciences - THz Communications

Abstract

2020

5.36 Gbit/s OFDM optical wireless communication link over the underwater channel

Authors
Araujo, JH; Kraemer, R; Tavares, JS; Pereira, F; Salgado, HM; Pessoa, LM;

Publication
2020 12th International Symposium on Communication Systems, Networks and Digital Signal Processing, CSNDSP 2020

Abstract
An OFDM transmission system is reported based on a directly modulated blue LASER diode, for high bit rate under-water optical communication applications. The 256 subcarriers 16-QAM signal is transmitted over a total distance of 2.4 m underwater with an EVM lower than -28.5 dB for a 250 MHz bandwidth and -16.5 dB for a 2 GHz bandwidth, the BER being lower than the forward error corrector limit. At the maximum bandwidth of 2 GHz a transmission rate of 5.36 Gbit/s is achieved. © 2020 IEEE.