Marco Gomes - Academia.edu (original) (raw)

Papers by Marco Gomes

2018 IEEE International Conference on Communications (ICC), 2018

This paper proposes a method to provide secrecy for digital communications with arbitrarily large... more This paper proposes a method to provide secrecy for digital communications with arbitrarily large quadrature amplitude modulation (QAM) constellations for transmission over a Gaussian fading wiretap channel. This is accomplished by breaking the constellation down into nested quadrature phase-shift keying (QPSK) symbols and randomizing the assignment between message bits and modulated symbols using channel state information (CSI). If enough random bits can be generated from CSI it becomes possible to uniquely map an arbitrary message to any symbol in the large QAM constellation. The proposed method can thereby provide perfect secrecy while maintaining high reliability by exclusively assigning minimum-distance-mapped constellations through the randomization for use by the legitimate decoder.

2017 IEEE International Conference on Communications (ICC), 2017

This paper presents a new technique for providing the analysis and comparison of wiretap codes in... more This paper presents a new technique for providing the analysis and comparison of wiretap codes in the small blocklength regime over the binary erasure wiretap channel. A major result is the development of Monte Carlo strategies for quantifying a code's equivocation, which mirrors techniques used to analyze normal error correcting codes. For this paper, we limit our analysis to coset-based wiretap codes, and make several comparisons of different code families at small and medium blocklengths. Our results indicate that there are security advantages to using specific codes when using small to medium blocklengths.

Applied Sciences

From a conceptual perspective, beyond-5G technologies promise to deliver very low latency, even h... more From a conceptual perspective, beyond-5G technologies promise to deliver very low latency, even higher data rates, and ultrareliable connections for future generations of communication systems. Modulation schemes based on orthogonal frequency-domain multiplexing (OFDM) can accommodate these requirements for wireless systems. Several hybrid OFDM-based systems, such as the time-interleaved block-windowed burst–OFDM (TIBWB–OFDM), are capable of achieving even better spectral confinement and power efficiency. This paper addresses the implementation of the TIBWB–OFDM system in more realistic and practical wireless link scenarios by addressing the challenges of proper and reliable channel estimation and frame synchronization. We propose to incorporate a preamble formed by optimal correlation training sequences such as the Zadoff–Chu (ZC) sequences. The added ZC preamble sequence is used to jointly estimate the frame beginning through signal-correlation strategies and a threshold decision ...

Electronics, 2020

The 5G and beyond future wireless networks aim to support a large variety of services with increa... more The 5G and beyond future wireless networks aim to support a large variety of services with increasing demand in terms of data rate and throughput while providing a higher degree of reliability, keeping the overall system complexity affordable. One of the key aspects regarding the physical layer architecture of such systems is the definition of the waveform to be used in the air interface. Such waveforms must be studied and compared in order to choose the most suitable and capable of providing the 5G and beyond services requirements, with flexible resource allocation in time and frequency domains, while providing high spectral and power efficiencies. In this paper, several beyond 5G waveforms candidates are presented, along with their transceiver architectures. Additionally, the associated advantages and disadvantages regarding the use of these transmission techniques are discussed. They are compared in a similar downlink transmission scenario where three main key performance indicat...

Physics Procedia, 2015

This paper addresses the use of computer-aided diagnosis (CAD) system for the cataract classifica... more This paper addresses the use of computer-aided diagnosis (CAD) system for the cataract classification based on ultrasound technique. Ultrasound A-scan signals were acquired in 220 porcine lenses. B-mode and Nakagami images were constructed. Ninety-seven parameters were extracted from acoustical, spectral and image textural analyses and were subjected to feature selection by Principal Component Analysis (PCA). Bayes, K Nearest-Neighbors (KNN), Fisher Linear Discriminant (FLD) and Support Vector Machine (SVM) classifiers were tested. The classification of healthy and cataractous lenses shows a good performance for the four classifiers (F-measure ≥92.68%) with SVM showing the highest performance (90.62%) for initial versus severe cataract classification.

2018 IEEE 88th Vehicular Technology Conference (VTC-Fall)

Time-Interleaved Block Windowed Burst-OFDM (TIBWB-OFDM) was recently proposed as a new waveform c... more Time-Interleaved Block Windowed Burst-OFDM (TIBWB-OFDM) was recently proposed as a new waveform candidate for future 5G systems and beyond. In this paper, it is shown that this technique is, in fact, easily combined with MIMO systems, offering promising gains in terms of power and spectral efficiency. In addition, since TIBWB-OFDM is built on the mature OFDM technique, it enables fast forward implementation of a frequency domain equalization with inter-stream MIMO suppression, maintaining the simplicity of the equalizer at an affordable cost. Bearing the complexity requirement in mind, three equalization techniques are studied, namely low-complexity iterative maximum rate combining (MRC) and equal gain combining (EGC) receivers, that do not require costly matrix operations, and an iterative block decision feedback equalizer (IB-DFE) receiver that, although requiring matrix inversions, can provide excellent results by taking advantage of single-carrier type nature of the TIBWB-OFDM block. We show that, on the one hand, IB-DFE receiver exhibits superior gains and can be successfully employed in scenarios with moderate number of antenna-elements, where its complexity can be actually manageable. On the other hand, it is shown that iterative MRC and EGC offers excellent performances for high values of receiving antenna-elements.

Physical Communication

Abstract The growing progress in wireless communication services led to a demand in high data rat... more Abstract The growing progress in wireless communication services led to a demand in high data rates, spectral efficiency and flexibility requirements. The Block-Windowed Burst Orthogonal Frequency Division Multiplexing (BWB-OFDM) technique has been recently proposed to face these demands. This technique employs smoother, non-rectangular windows, allowing a power spectral density similar to the filtered OFDM approach, thus achieving high spectral efficiency; also, it packs together several OFDM symbols, with the addition of a sole zero-padding to accommodate the multipath channel’s propagation delay, thereby improving power efficiency. However, BWB-OFDM has the same drawbacks of OFDM when transmitting over hostile channel conditions, namely the performance degradation due to deep fades associated to severe frequency-selective channels. This paper proposes a new Time Interleaved BWB-OFDM (TIBWB-OFDM) technique that performs interleaving on the time-samples of each BWB-OFDM block, creating a kind of diversity effect at the frequency domain, granting a much better resilience against deep inband fades, while keeping all the mentioned advantages of BWB-OFDM at the cost of no added complexity. Also, by regarding TIBWB-OFDM as a hybrid technique combining single-carrier and multicarrier characteristics, this paper also proposes the use of non-linear frequency domain equalizers based on the Iterative Block Frequency Domain Equalization (IB-DFE) concept for TIBWB-OFDM detection. It is shown that noteworthy improvements can be achieved in bit error rate (BER) performance compared to conventional OFDM schemes when employing typical zero-forcing (ZF) and minimum mean-square error (MMSE) linear equalizers.

2018 IEEE 87th Vehicular Technology Conference (VTC Spring)

This paper proposes a way of turning the equalisation of multiple- input multiple-output orthogon... more This paper proposes a way of turning the equalisation of multiple- input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) signals simpler through the employment of low complexity iterative frequency domain equalisation (FDE) receivers based on equal gain combining (EGC) and maximum ratio combining (MRC) concepts, that do not require computing the inverses of high dimensional channel matrices. Performance results show that MIMO- OFDM schemes employing this type of techniques can achieve excellent bit error rate (BER) performances over severe time- dispersive channels and, therefore, approach or even outperform receivers that require inverting channel matrices, such as zero forcing (ZF) and minimum mean squared error (MMSE), after a few iterations.

2017 25th European Signal Processing Conference (EUSIPCO)

This paper proposes a transmitter structure that combines a ring-type magnitude modulation (RMM) ... more This paper proposes a transmitter structure that combines a ring-type magnitude modulation (RMM) technique with a linear amplification with nonlinear components (LINC) scheme for power and spectrally efficient transmission based on bandwidth limited OQPSK signals, for either a linear combiner (LC) or a Chireix combiner (CC). It shows that by controlling the transmitted signal's envelope through RMM, the range of the LINC decomposition angle is considerably decreased. This significantly improves LC's power efficiency, and substantially reduces CC's spectral leakage while maintaining its high amplification efficiency.

Proceedings of the International Conference on Signal Processing and Multimedia Applications

This paper proposes an efficient HDL library of processing units for generic and DVB-S2 LDPC deco... more This paper proposes an efficient HDL library of processing units for generic and DVB-S2 LDPC decoders following a modular and automatic design approach. General purpose, low complexity and high throughput bit node and check node functional models are developed. Both full serial and parallel architecture versions are considered. Also, a dedicated functional unit for an array processor LDPC decoder architecture to the DVB-S2 standard is considered. Additionally, it is described an automatic HDL code generator tool for arbitrary decoder architectures and LDPC codes, based on the proposed processing units and Matlab scripts.

Sensors

In order to secure wireless communications, we consider the usage of physical-layer security (PLS... more In order to secure wireless communications, we consider the usage of physical-layer security (PLS) mechanisms (i.e., coding for secrecy mechanisms) combined with self-interference generation. We present a prototype implementation of a scrambled coding for secrecy mechanisms with interference generation by the legitimate receiver and the cancellation of the effect of self-interference (SI). Regarding the SI cancellation, four state-of-the-art algorithms were considered: Least mean square (LMS), normalized least mean square (NLMS), recursive least squares (RLS) and QR decomposition recursive least squares (QRDRLS). The prototype implementation is performed in real-world software-defined radio (SDR) devices using GNU-Radio, showing that the LMS outperforms all other algorithms considered (NLMS, RLS and QRDRLS), being the best choice to use in this situation (SI cancellation). It was also shown that it is possible to secure communication using only noise generation by the legitimate rec...

This paper addresses the problem of controlling the envelope's power peak of single carrier m... more This paper addresses the problem of controlling the envelope's power peak of single carrier modulated signals, band limited by root-raised cosine (RRC) pulse shaping filters, in order to maximize the efficiency of the transmitter's high power amplifier (HPA). A novel multistage polyphase approach for the magnitude modulation (MM) concept is developed. As opposed to traditional MM solutions, based on look-up-tables (LUT), in this proposal, the MM coefficients are computed in real-time by a low complexity polyphase filter system. The need to use back-off from HPA saturation is almost eliminated (reduction greater than 95%) with just a 2-stage system. Simulation results also show peak-to-average (PAPR) reduction gains similar to the state of the art trellis shaping techniques. However our proposal has the major advantage of allowing this MPMM system to be easily added to any currently working transmitter system to significantly improve its power efficiency.

Health and Technology

Cataract is an ocular condition associated to the loss of the normal crystalline lens transparenc... more Cataract is an ocular condition associated to the loss of the normal crystalline lens transparency, and its progression can result in a total loss of vision. The gold standard diagnostic method consists on qualitative observation through a slit lamp. This method has two limitations: incipient cataract may not be detected and the cataract hardness is subjectively evaluated. It may delay the diagnosis, or result on phacoemulsification surgeries complications when cataract hardness is not correctly estimated. On this study we present a new prototype for objective cataract detection and characterization, based on ultrasounds. The Eye Scan Ultrasonic System (ESUS) acquires A-scan signals at a nominal frequency of 20 MHz. The lens interfaces can be automatically detected in real time, based on the analysis of signal energy levels. The detection and characterization of cataract type and severity is done by an automatic classification algorithm based on features extracted in time and frequency domain. The system performance has been tested on preclinical data, and the beginning of clinical studies is expected shortly.

2018 IEEE 87th Vehicular Technology Conference (VTC Spring)

This paper presents a testbed implementation and evaluation of coding for secrecy schemes in a re... more This paper presents a testbed implementation and evaluation of coding for secrecy schemes in a real environment through software defined radio platforms. These coding schemes rely on interleaving and scrambling with randomly generated keys to shuffle information before transmission. These keys are then encoded jointly with data and then hidden (erased) before transmission, thus only being retrievable through parity information resulting from encoded data. An advantage of the legitimate receiver (e.g. a better signal-to-noise ratio) on the reception of those keys provides the means to achieve secrecy against an adversary eavesdropper. Through this testbed implementation, we show the practical feasibility of coding for secrecy schemes in real-world environments, unveiling the usefulness of interleaving and scrambling with a hidden key to reduce the required advantage over an eavesdropper. We further describe and present solutions to a set of issues that appear when doing practical implementations of security schemes in software defined radio platforms.

2017 25th European Signal Processing Conference (EUSIPCO), Aug 1, 2017

Wireless Communications and Mobile Computing

The exploration of the physical layer characteristics of the wireless channel is currently the ob... more The exploration of the physical layer characteristics of the wireless channel is currently the object of intensive research in order to develop advanced secrecy schemes that can protect information against eavesdropping attacks. Following this line of work, in this manuscript we consider a massive MIMO system and jointly design the channel precoder and security scheme. By doing that we ensure that the precoding operation does not reduce the degree of secrecy provided by the security scheme. The fundamental working principle of the proposed technique is to apply selective random rotations in the transmitted signal at the antenna level in order to achieve a compromise between legitimate and eavesdropper channel capacities. These rotations use the phase of the reciprocal wireless channel as a common random source between the transmitter and the intended receiver. To assess the security performance, the proposed joint scheme is compared with a recently proposed approach for massive MIMO...

IEEE Access

The purpose of this paper is to advance the current state of physical layer security through the ... more The purpose of this paper is to advance the current state of physical layer security through the design and analysis of a discrete jamming scheme that exploits the reciprocal characteristic of the wireless channel with the aim to create equivocation to a passive multiple-antenna eavesdropper. Closed form solutions of the secrecy capacity for different configurations of the jamming component were obtained and successfully compare with the simulation results. Furthermore, the secrecy level provided by the developed scheme is analyzed taking into account the number of bits extracted from the channel. The asymptotic study of the proposed secrecy technique allowed to conclude that in the high-power regime, full secrecy is obtained even considering that the eavesdropper is equipped with an unlimited number of antennas. INDEX TERMS Physical layer security, secrecy capacity, jamming, channel reciprocity.

IET Communications

This study considers massive multiple-input multiple-output (m-MIMO) schemes employing orthogonal... more This study considers massive multiple-input multiple-output (m-MIMO) schemes employing orthogonal frequency division multiplexing (OFDM) or single-carrier with frequency-domain equalisation (SC-FDE) modulation, concerning an uplink transmission. The authors study the performance and complexity for both conventional zero forcing (ZF) and minimum mean squared error (MMSE) (which require the inversion of channel matrix) and iterative frequency domain equalisation receivers based on equal gain combining (EGC) and maximum ratio combining (MRC) concepts, that do not require matrix inversions. It is shown that, although matrix inversions are generally the more complex operations for relatively balanced systems (i.e. with similar number of transmit and receive antennas), this is not generally true for systems where the channel matrix is `very tall' (i.e. much more receive than transmit antennas), at least in terms of the number of multiplications and sums. This means that the advantage on a reduced complexity of MRC/EGC-based equalisers with respect to ZF/MMSE is, in fact, limited. However, the performance advantages combined with the possibility of parallel receiver implementations, make those techniques particularly interesting for m-MIMO schemes, either employing OFDM or SC-FDE modulations.

2018 IEEE International Conference on Communications (ICC), 2018

2017 IEEE International Conference on Communications (ICC), 2017

Applied Sciences

Electronics, 2020

Physics Procedia, 2015

2018 IEEE 88th Vehicular Technology Conference (VTC-Fall)

Physical Communication

2018 IEEE 87th Vehicular Technology Conference (VTC Spring)

2017 25th European Signal Processing Conference (EUSIPCO)

Proceedings of the International Conference on Signal Processing and Multimedia Applications

Sensors

Health and Technology

2018 IEEE 87th Vehicular Technology Conference (VTC Spring)

2017 25th European Signal Processing Conference (EUSIPCO), Aug 1, 2017

Wireless Communications and Mobile Computing

IEEE Access

IET Communications