Sébastien Roy

• PhD
• Professor (Full) at Université de Sherbrooke

In a previous work, a two-layer linear receiver was proposed as a low-complexity scheme that can achieve a good trade-off between performance and complexity in a massive multiple-input multiple-output (MIMO) context. For this scheme, the antenna array is split up into a number of subsets and multi-cell minimum mean-square-error (M-MMSE) combining i...

bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The structural health monitoring (SHM) of bridges with wireless sensor networks (WSNs) is addressed by leveraging two distinct but interrelated aspects: GaAs-based solar energy harvesting and switched-beam antenna strategies in combination with asynchrono...

The operational and technological structures of radio access networks have undergone tremendous changes in recent years. A displacement of priority from capacity–coverage optimization (to ensure data freshness) has emerged. Multiple radio access technology (multi-RAT) is a solution that addresses the exponential growth of traffic demands, providing...

In a previous work, a two-layer linear receiver was proposed as a low-complexity scheme that can achieve a good trade-off between performance and complexity in a massive multiple-input multiple-output (MIMO) context. For this scheme, the antenna array is split up into a number of subsets and multi-cell minimum mean-square-error (M-MMSE) combining i...

In this paper, we study different modulation techniques for visible light communication (VLC), taking illumination constraints into account. Two modulation schemes are compared, namely pulse amplitude modulation (PAM) and carrierless amplitude and phase (CAP) modulation, through both simulations and experimental measurements. The data link under st...

Emerging Internet-of-Things (IoT) applications are driving increasing demand for advanced services in wireless networks, prompting the development of new technologies to address the associated challenges. Energy efficiency of IoT standards is a key feature targeted by research efforts and industrial activities, leading to an extensive and growing n...

The distributed management of residual energy among sensor devices within wireless sensor networks is a crucial technique that can be leveraged to maximize network lifetime. This paper proposes an approach towards this goal based on an ultra-low-power Medium Access Control (MAC) protocol and a geographical multi-hop routing protocol according to a...

For large-scale antenna array multiple-input multiple-output (MIMO) systems, a typical solution often put forward for uplink detection consists in applying low-complexity linear receivers such as zero-forcing (ZF) and minimum mean-square error (MMSE) combiners. In this paper, the performance of uplink MMSE detection has been analyzed in the context...

In this paper, we provide a performance analysis of communication systems over Rayleigh-product channels with two popular diversity combining techniques, namely maximal ratio combining (MRC) and selection combining (SC). We first derive new closed-form expressions for the exact cumulative distribution function (CDF) and probability density function...

In this paper, we demonstrate an experimental visible light communication (VLC) transmission compliant with illumination standards consisting of low-cost components. We therefore employ the carrierless amplitude and phase (CAP) modulation technique over a low-cost white light emitting diode (LED), and we experimentally investigate the maximum achie...

This paper considers an uplink massive MIMO system, in which the base station (BS) is equipped with a very large antenna array to serve multiple users simultaneously in the presence of out-of-cell interferers. Multi-cell minimum mean-square-error (M-MMSE) detection is used to mitigate co-channel interference (CCI) and multipath fading effects. Howe...

The double-scattering fading models have found applications in many transmission scenarios. In this paper, approximate probability density functions (PDFs) are proposed for double-Nakagami fading and Gamma-Gamma fading, based on Hankel’s expansion of Bessel function. The proposed PDF is not only consistent with the exact PDF when the difference bet...

Non-orthogonal multiple access (NOMA) exploits successive interference cancellation technique at the receivers to improve the spectral efficiency. By using this technique, multiple users can be multiplexed on the same subchannel to achieve high sum rate. Most previous research works on NOMA systems assume perfect channel state information (CSI). Ho...

This paper provides a performance analysis of communication systems over Rayleigh-product single-output multiple-output (SIMO) channels with maximal-ratio combining (MRC) and selection combining (SC). New closed-form expressions for the exact cumulative distribution function (CDF) and probability density function (PDF) of the post-combining signal-...

Assistive Technologies (ATs) also called extrinsic enablers are useful tools for people living with various disabilities. The key points when designing such useful devices not only concern their intended goal, but also the most suitable human-machine interface (HMI) that should be provided to users. This paper describes the design of a highly intui...

To improve wireless system performance using co-channel signals and multiple receiver antennas, we develop a new adaptive block-length partitioned Viterbi algorithm (ABL-PVA) receiver for the MIMO frequency-selective fading channel. The classic PVA has a trellis detector for each transmit antenna and feeds back tentative decisions between these tre...

A new block-delayed partitioned Viterbi algorithm (BD-PVA) receiver for the MIMO frequency-selective fading channel is proposed. The classic PVA has a trellis detector for each transmit antenna and feeds back tentative decisions between these trellis detectors. The proposed algorithm uses more reliable temporary decisions in the feedback loop inste...

In this paper, we propose a new block coding scheme to increase the diversity gain of multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems over slow-fading wireless channels. We assume that the antenna elements at the transmitter are reconfigurable and capable of independently changing the physical charact...

This paper presents a technique to optimize with constraints, the performance of three degrees of freedom silicon accelerometers. A flexure configuration has been proposed in order to meet the requirements of small cross-axial acceleration, high sensitivity, and linear sensitivity. The overall chip dimension is 1.5 x 1.5 x 0.5 mm(3) (L x W x T) and...

In this paper, we derive analytical expressions to compute the covariance matrix of the signals impinging on a reconfigurable antenna array. We consider a receiver equipped with a linear antenna array where each antenna element can be independently configured to create a directive radiation pattern toward a selected direction. In our derivation, we...

A challenge in the design of rate-compatible (RC) low-density parity-check (LDPC) codes is how to maximize the range of code rates. In this paper, we propose a class of RC LDPC codes with a very wide range of code rates. To ensure linear encoding, dual-diagonal form for the parity part of the mother parity-check matrix is used. Constructed from shi...

In this paper, we present an experimental study evaluating the performance of a reconfigurable antenna element for direction-of-arrival (DOA) estimation in wireless systems. We consider a reconfigurable antenna with directive radiation pattern and an electronic control mechanism to continuously scan its beam over the space. We implement a MUSIC-typ...

Inter-cell interference is a challenging issue in non-cooperative time-division duplex (TDD) cellular systems with large antenna arrays. In this document we propose two signal detection methods based on Differential chaos-shift-keying (DCSK) modulation that robustly detect individual users in congested networks. Blind signal detection at the BTS is...

We propose a class of rate-compatible (RC) low-density parity-check (LDPC) codes that has linear encoding complexity and low error floor. To ensure linear encoding, a deterministic form for the parity part of the mother parity-check matrix is used. To guarantee good performances in the waterfall region for a wide range of code rates, a layered dens...

We propose a space-frequency (SF) block coding scheme for a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system using antennas with reconfigurable radiation patterns. In this system, each element of the antenna array at the transmitter side is assumed to be reconfigurable so that it can independently chang...

This work discusses the stability issues of PI-based brushless DC motor (BLDCM) speed controllers under the presence of strong time delay in the controller loop. Understanding of the time delay effect is of paramount importance to increase performance, quality and productivity in important modern applications. Unfortunately, the time delay effect i...

The applicability of the Viterbi add-compare-select (ACS) functional block to both convolutional and LDPC codes in various parallel implementations is investigated. To this end, a trellis representation for arbitrary LDPC codes must first be established. Then, a high-level architecture for a Viterbi-algorithm-based unified decoder is proposed. An i...

Inter-cell interference is a challenging issue in noncooperative time-division duplex (TDD) cellular systems with large antenna arrays. Such a problem arises when pilot sequences received by a base station (BTS) are contaminated by users in adjacent cells transmitting the same training sequences. In [7], Fernandes, Ashikhmin and Marzetta proposed a...

In this paper, we propose a simple design for a multi-user MIMO precoder using a Grassmannian codebook. The precoder design is applied to both sides of the wireless link under the assumption of limited feedback and the same codebook. The proposed scheme aims to correct the precoding vectors choice in order to avoid more than one user having the sam...

It is known that a selection combining (SC) diversity receiver can offer the full diversity order of an antenna array while necessitating only a single RF chain. However, a means must be provided to continuously monitor the SNR in all branches of the array. Switched diversity schemes, such as switch-and-examine (SEC), do not have this requirement b...

The ubiquitous real-time monitoring and recording of surface electromyography (sEMG) signal is essential to several rehabilitation applications, such as muscle recovery analysis. We present an inexpensive wireless sEMG sensor using a commercial off-the-shelf wireless microcontroller unit (MCU) incorporating a simplified adaptive differential pulse...

In a previous work, a hierarchical selection diversity scheme (HSD) was proposed as a cost-effective means of extracting a high diversity gain out of a large antenna array. To achieve this, the array is split up into a number of groups and the antenna having the best instantaneous SNR in each group is selected for further processing. The resulting...

In this paper, we study the performance of a reconfigurable multiple-input multiple-output (RE-MIMO) system in spatially correlated frequency- selective fading channels. In particular, we propose to use a RE-MIMO system to overcome the inter symbol interference (ISI) problem caused by multipath propagation. In the proposed system, we use a 3-dimens...

This paper presents a novel precoding approach for MIMO broadcast channels, in which is performed on both sides of the wireless link. The aim of the proposed approach is to avoid the same precoding vectors choice when all users use a common codebook. In the proposal approach, firstly, we focus on the brute codeword selection at the transmitter side...

Todays' networks are becoming increasingly complex. They must provide a growing variety of services to a wide range of devices. In order to do so, they must make efficient use of modern technologies including MIMO, macrodiversity, power control, channel allocation, beamforming, and so on. In this context, the centralized management of radio resourc...

In this paper, we study the performance of the MUltiple SIgnal Classification (MUSIC) direction-of-arrival (DoA) estimation algorithm in a clustered channel model. We examine the effect of angular spread on the estimation accuracy of the MUSIC algorithm. Simulation result shows that the performance of the MUSIC algorithm degrades as the angular spr...

This paper proposes a hierarchical selection diversity (HSD) scheme whereby a large array is split up into multiple groups, with the best antenna (in the SNR sense) being selected in each group. The set of selected antennas is then combined using maximal-ratio combining. As opposed to generalized selection combining (GSC), which imposes no restrict...

This paper presents a new method to map a state-space continuous-time model into an equivalent discrete state-space model. It is shown that the discrete model can approximate the continuous one to an arbitrary high-order which can be set by the user. In addition, it is demonstrated that the constructed discrete model is guaranteed stable, where it...

There is an abundant literature on the fully-analytical performance assessment of diversity combining arrays in the presence of interference, where the combining method is anything from scanning and selection diversity through optimum (MMSE) combining. However, in most of the literature and for the sake of analytic tractability, the noise is often...

In this paper, we present a study of optimal training sequences for robust joint channel estimation and signal detection. Particularly, we study the case of virtual MIMO links, where there are more co-channel signals M than receive antennas N, i.e., N

This paper investigates the average bit error rate (BER) performance of reconfigurable single-input single-output (RE-SISO) antenna systems in the clustered channel model. The main focus of the paper is to evaluate the impacts of angle of arrival (AoA) estimation errors, angular spread and antenna beamwidth on the performance of a reconfigurable sy...

Many wireless communication systems such as IS-54, enhanced data rates for the GSM evolution (EDGE), worldwide interoperability for microwave access (WiMAX) and long term evolution (LTE) have adopted low-density parity-check (LDPC), tail-biting convolutional, and turbo codes as the forward error correcting codes (FEC) scheme for data and overhead c...

In this paper, we present a method which jointly performs robust channel estimation and signal detection over rank-deficient MIMO links. This technique achieves an excellent estimation of the channel matrix by using all detected symbols within a data frame. Symbol detection is achieved by means of a sphere decoding algorithm. The proposed scheme is...

In a time-varying transmission environment, the received signal components are subject to frequency shifts due to the Doppler effect. The Doppler frequency is dependent on the carrier frequency and the environment variation rate. In a fixed wireless channel, the channel variation is caused by scatterer motion. In such a channel, if the channel is N...

Many fields of human endeavour, such as biology and the theory of complex systems, are now embracing the concept of self-organization based on local actions leading to a desirable global emergent behavior. While many examples, both natural and artificial, can be found of such self-organized systems, the relationship between the local rules and the...

A baseband multi-input, multi-output (MIMO) multi-carrier code division multiple access (MC-CDMA) downlink system meeting wideband CDMA (WCDMA) bandwidth requirements is simulated and its receiver part is implemented into a field programmable gate array (FPGA). The receiver was designed by integrating an existing single-input, single-output (SISO)...

Over the last few years, a research program was undertaken in collaboration with InterDigital Canada under the theme “Advanced Broadband Transceivers.” The aim was the development of novel signal processing techniques, exploiting the latest in communication theory and having fundamental advantages, while keeping a focus throughout on associated imp...

In this paper, we present a technique that provides spatial diversity for a Chaos Shift Keying (CSK) transceiver. The system transmits and receives chaos-based modulated signals through multiple antennas with high spectral efficency. We show that Multiple-Input Multiple-Output (MIMO) systems greatly improve the Bit -error-rate (BER) performance of...

In a time-varying transmission environment, the received signal components are subject to frequency shifts due to the Doppler effect. The Doppler frequency is dependent on the carrier frequency and the environment variation rate. In a fixed wireless channel, the channel variation is caused by scatterer motion. In such a channel, if the channel is No...

A baseband multi-carrier code division multiple access (MC-CDMA) downlink receiver meeting wideband CDMA (WCDMA) bandwidth requirements is simulated and implemented into a field programmable gate array (FPGA) platform. The receiver was designed and implemented to achieve low FPGA resource consumption via the use of low-complexity DSP algorithms and...

In this paper, we present a method which jointly performs robust channel estimation and signal detection. In most receive antenna arrays, a known signal preamble at the beginning of the data frame is used to estimate the channel matrix. In this document, a first channel estimate is based on the received signal subspace analysis which uses statistic...

In this paper, we present an enhancement of the sphere decoder (SD) algorithm that uses a novel radius initialization based on a noise-predictive Minimum Mean Squared Error (MMSE) filter. This technique decreases considerably the complexity of the lattice search. Our SD can to be used over underdetermined channels and it outputs soft information fo...

Low-density parity-check (LDPC) codes offer a very powerful error correction technique which allows data transmission in wireless networks with arbitrarily low probability of error. This paper studies LDPC-coded wireless networks with a two-way relay scheme. Two techniques have been developed to increase the throughput of relay networks. First, onl...

To resolve today's spectrum scarcity problem, cognitive radio network is widely expected to usher in the next wave in wireless communications. This paper has developed a high-speed sphere decoder for multiple-inputs multiple-outputs (MIMO) transceivers used in cognitive radio networks. First, a novel sphere decoding algorithm is proposed which incr...

The need for speed and reliability in wireless local area networks is constantly increasing. The IEEE 802.11n standard aims to offer better data rates and performances by combining OFDM and MIMO techniques. Transmit beamforming is one of these techniques and should allow a stronger, more reliable signal for the intended user, while reducing interfe...

Power consumption is a critical issue in many wireless sensor network scenarios where network life expectancy is measured in months or years. Communication protocols typically rely on synchronous operation and duty-cycle mechanisms to reduce the power usage at the cost of decreased network responsiveness and increased communication latency. A low-p...

The proposed proof-of-concept design described herein demonstrates that minimalist multiagent systems do provide all expected qualities: scalability, dynamic properties, efficiency, simplicity, adaptability and auto-configuration. Moreover, it represents a novel and surprisingly simple solution to resource allocation. It is most obvious with the po...

In this paper, we present three techniques that provide spatial diversity to a Differential Chaos Shift Keying (DCSK) chaotic transceiver. The system transmits and receives chaos-based modulated signals through multiple antennas. We show that Multiple-Input Multiple-Output (MIMO) systems greatly improve the BER performance of chaotic communications...

We investigate a new approach to decode convolutional and turbo codes by means of the belief propagation (BP) decoder used for low-density parity-check (LDPC) codes. In addition, we introduce a general representation scheme for convolutional codes through parity check matrices. Also, the parity check matrices of turbo codes are derived by treating...

Power management in wireless networks has been thoroughly studied and applied in many different contexts. However, the problem has not been tackled from a multiple-agent perspective (MA). This paper intends to do so in the context of a wireless network comprised of distributed base stations using macrodiversity. The proposed design is shown to pro...

Many cryptosystems embed a high-quality true random number generator (TRNG). The randomness quality of a TRNG output stream depends on its implementation and may vary due to various changes in the environment such as power supply, temperature, electromagnetic interferences. Attacking TRNGs may be a good solution to decrease the security of a crypto...

Many embedded security chips require a high-quality random number generator (RNG). Unfortunately, hardware RNG randomness can vary in time due to implementation defects or certain kinds of attacks. To overcome this issue, this paper presents the implementation of a battery of statistical test for randomness. The battery is selected for its efficien...

Many embedded security chips require a high- quality Random Number Generator (RNG). Unfortunately, hard- ware RNG randomness can vary in time due to implementation defects or certain kinds of attacks. To overcome this issue, this paper presents the implementation of a battery of statistical test for randomness. The battery is selected for its effic...

Many embedded security chips require a high- quality digital True Random Number Generator (TRNG). Re- cently, some new TRNGs have been proposed in the literature, innovating by their new architectures. Moreover, some of them don't need to use the post-processing unit usually required in TRNG constructions. As a result, the TRNG data rate is enhance...

Low density parity check (LDPC) codes are known to achieve a performance very close to the Shannon capacity limit on Additive White Gaussian Noise (AWGN) and erasure channels. The extrinsic information transfer (EXIT) chart is a powerful method for analyzing iteratively decoded codes such as Turbo codes. EXIT charts were introduced as a method for...

This paper presents a protocol to manage multi-user interference (MUI) in a distributed base station system (DBS). Traditional cellular communication schemes are based on one-to-one wireless links. In a DBS scheme, more than one station can relay the same mobile. Hence, interference patterns cannot be handled by conventional means. The protocol pro...

Many fields of human endeavour, such as biology and the theory of complex systems, are now embracing the concept of self-organization based on local actions leading to a desirable global emergent behavior. While many examples, both natural and artificial, can be found of such self-organized systems, the relationship between the local rules and the...

Cooperation in wireless communications is an attractive means to gain spectral efficiency or diversity. Typically, cooperation is studied at the level of an individual end-to-end link. On the other hand, the primary goal of the the protocol proposed herein is not the improvement of individual link quality, but rather to improve global resource util...

Power consumption is a critical issue in many wireless sensor network scenarios where network life expectancy is measured in months or years. Communication protocols typically rely on duty-cycle mechanisms to reduce the power usage at the cost of decreased network responsiveness and increased communication latency. A low-power radio-triggered devic...

The rapid progress in microsystems technology is increasingly supported by various modeling methodologies and simulation tools. A coupled-field analysis procedure is established to analyze a multi-degree of freedom accelerometer. The proposed sensor dimensions are 1.5times1.5times0.5 mm3 (LtimesWtimesT) and the beam size is 950times80times10 mum3 (...

By using a multi-rate low density parity check (LDPC) code, we propose an LDPC coded multiple-input multiple-output (MIMO) transceiver with adaptive spectral efficiency which allows data transmission in wireless networks at rates near the channel capacity with arbitrarily low probability of error. Equipped with multiple transmit and multiple receiv...

It is known that fast, fully combinational leading-digit detector circuits can be generated efficiently by recognizing their inherent hierarchical structure. It is shown herein that this structure is not only hierarchical, but also recursive. This recursivity fully defines a minimal-complexity circuit, thus guaranteeing optimal circuit synthesis. S...

In this paper, we propose a class of adaptive low-density parity-check (LDPC) codes for reliable data transmission in wireless networks, i.e. the code rate can be adapted according to channel conditions to maximize the total capacity. Constructed from shifted identity matrices, the first advantage of the proposed codes is that these codes are parti...

Low-density parity-check (LDPC) codes offer a very powerful error correction technique which allows data transmission in wireless networks at rates near the channel capacity with arbitrarily low probability of error. In this paper, we design a class of linearly encodable LDPC codes with adaptive code rates, i.e. the code rate can be adapted accordi...

OFDM Wireless LANs based on the IEEE802.11 standard are complex systems in themselves. When smart antennas are used in such systems, both the MAC and the PHY layers must be redefined in order to achieve application-specific goals. As a result, the development of such systems can become impressively heavy. A complete development framework is present...

It is well known that to perform accurate Direction of Arrivals (DOA) estimation using algorithms like MUSIC (MUltiple SIgnals Classification), antenna array data must be calibrated to match the theoretical model upon which DOA algorithms are based. This paper presents experimental measurements from independent sources obtained with a linear antenn...

A synthesis and optimization process is proposed and applied to the design of a specific MEMS device, namely an acceleration sensor. The design synthesis methodology exploits the fast and accurate simulation of the SUGAR tool (based on modified modal analysis) along with the full simulation capability of ANSYS (based on the finite element method)....

We propose a new semi-analytic method for the study of the performance of a RAKE receiver in a direct-sequence code-division multiple-access (DS-CDMA) based ultra wideband (UWB) system. This method is intended as a tool to facilitate further performance studies of this type of system and, ultimately, to lead to a fully analytical model. We also ana...

Cooperation in wireless communications is an at- tractive means to gain spectral efficiency or diversity. Typically, cooperation is studied at the level of an individual end-to-end link. On the other hand, the primary goal of the the protocol proposed herein is not the improvement of individual link quality, but rather to improve global resource ut...

Traditional cellular communication schemes are based on one to one wireless links. In a distributed base station (DBS) scheme, more then one station can relay the same mobile. This paper studies the impact of channel interference on the behavior of an agent system which manages the multiple connections at the DBS. It is shown that DBS can provide a...

OFDM Wireless LANs based on the IEEE 802.11 standard are complex systems in themselves. When smart antennas are used in such systems, both the MAC and the PHY layers must be redefined in order to achieve application-specific goals. As a result, the development of such systems can become impressively heavy. A complete development framework is presen...

The main bottleneck in broadband reconflgurable (or software-defined) radio systems is the fast analog-to-digital converters (ADC) required to capture the entire system band. Such ADCs are typically costly, consume a lot of power, and have non-ideal transfer characteristics, as well as a limited spurious-free dynamic range (SFDR). This cost problem...

This paper discusses high-performance code construction and high-speed encoder and decoder designs for low density parity check (LDPC) codes. Thanks to their nice structures, LDPC codes constructed from shifted identity matrices have been emphasized. Several techniques in code constructions have been proposed to lower the bit error floor down to 10...

Cellular automata are recognized as efficient solutions for high-rate random number generators. However, for good randomness, the CA rule and the number of neighbor cells must be chosen with care. If a cell has N neighbors, 2² ⁿ rules are possible, and finding the optimal rule is a time-consuming task. To reduce its complexity...

This paper presents a joint row-column decoding algorithm for the decoding of low-density parity-check (LDPC) codes. Simulation indicates that the proposed algorithm improves the performance in both the waterfall region and the error floor region. By combining row processing with column processing, the joint row-column decoding algorithm reduces th...