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Pierre Duhamel

Ecole CentraleSupelec, L2S, Emeritus

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Papers by Pierre Duhamel

Parity-check matrix calculation for paraunitary oversampled DFT filter banks

HAL (Le Centre pour la Communication Scientifique Directe), Oct 1, 2008

Oversampled filter banks, interpreted as error correction codes, were recently introduced in the ... more Oversampled filter banks, interpreted as error correction codes, were recently introduced in the literature. We here present an efficient calculation and implementation of the parity-check polynomial matrices for oversampled DFT filter banks. If desired, the calculation of the partity-check polynomials can be performed as part of the prototype filter design procedure. We compare our method to those previously presented in the literature.

Lossless Coding of Point Cloud Geometry using a Deep Generative Model

arXiv (Cornell University), Jul 1, 2021

Detecting Covariate Shift with Black Box Predictors

Many Machine Learning algorithms aiming at classifying signals/images X among a number of discret... more Many Machine Learning algorithms aiming at classifying signals/images X among a number of discrete labels Y involve training instances, from which the predictor P Y |X is extracted according to the data distribution P X|Y . This predictor is later used to predict the appropriate label for other instances of X that are hence assumed to be drawn from the same distribution. This is a fundamental requirement for many realworld applications, therefore it is of great importance to monitor the reliability of the classification provided by the algorithm based on the learned distributions, when the test set statistics differ from the training set ones. This paper makes a step in that direction by proposing a Black Box Shift Detector of the data evolution (covariate shift). 'Black Box' here means that it does not require any knowledge of the predictor's architecture. Experiments demonstrate accurate detection on different highdimensional datasets of natural images.

Codage conjoint souce/canal: enjeux et approches

HAL (Le Centre pour la Communication Scientifique Directe), Sep 1, 1997

En partant de la théorie de SHANNON, expliquée sur deux exemples très simples, nous montrons que ... more En partant de la théorie de SHANNON, expliquée sur deux exemples très simples, nous montrons que la manière de réaliser l'optimum pour un critère combiné source/canal n'est pas unique. Par rapport à un système traditionnel où l'optimisation source et canal est faite séparément, la complexité globale peut être réduite tout en conservant un bon niveau de performances. Nous explicitons ensuite les avantages potentiels en pratique d'une optimisation conjointe et ses limites.

Audio watermarking under desynchronization and additive noise attacks

HAL (Le Centre pour la Communication Scientifique Directe), 2006

Digital watermarking is often modeled as the transmission of a message over a noisy channel denot... more Digital watermarking is often modeled as the transmission of a message over a noisy channel denoted as "watermark channel." Distortions introduced by the watermark channel result mainly from attacks and may include interference from the original signal. One of the main differences with classical transmission situations stems from the fact that perceived distortions have to be taken into account. However, measuring the perceived impact an attack has on a watermarked signal is currently an unsolved problem. Possible means of circumventing this problem would be 1) to define the distortion in a so-called "perceived domain" and define an "ad hoc" equivalence between objective and perceived distortion or 2) to define an "equivalent distortion" by removing from the attack noise the part that is correlated to the host signal. This paper concentrates on the second approach and first shows that the resulting "equivalent" attack is a particular case of a thoroughly studied channel: filtering plus additive noise. However, the approach in this paper emphasizes the fact that the additive noise in the model has to be decorrelated with the signal. Then, the formalism is applied to (desynchronization plus noise) attacks on audio signals. In this context, this paper provides the corresponding capacities, as well as optimal "attack" and "defense" strategies in a game theory context.

A Simple Statistical Method to Detect Covariate Shift

HAL (Le Centre pour la Communication Scientifique Directe), Aug 26, 2019

L'utilisation croissante de réseaux de neurones dans le traitement automatique de données soulève... more L'utilisation croissante de réseaux de neurones dans le traitement automatique de données soulève de nouvelles problématiques. L'une d'elles est la détection de décalage des covariables d'entrées. Ce décalage entraîne une inadéquation entre le réseau et les données: le réseau continue de traiter les données, mais fournit des résultats vides de sens. Nous présentons des méthodes statistiques de détection de comportement peu confiant.

Blind identification/equalization using deterministic maximum likelihood and a partial information on the input

Transform Coefficient Coding for Screen Content in Versatile Video Coding (VVC)

A transform coefficient coding scheme is proposed for 4 × 4 blocks in Versatile Video Coding (VVC... more A transform coefficient coding scheme is proposed for 4 × 4 blocks in Versatile Video Coding (VVC), targeting screen content applications. The proposed algorithm, called Unary Bitplane Coding (UBC), uses unary codes of the coefficient amplitudes and represents each block by their bitplanes. This representation allows exploiting further contextual information for source separation during the entropy coding. Experiments in the Joint Exploration test Model (JEM) show that replacing the existing transform coding with UBC only for 4 × 4 blocks brings on average 2.8% and 3.4% BD-R gain in the random access and all intra modes, respectively.

Intra Block-DPCM with Layer Separation of Screen Content in VVC

An intra coding algorithm with layer separation is proposed. This algorithm is designed on top of... more An intra coding algorithm with layer separation is proposed. This algorithm is designed on top of an adopted tool in VVC, called Block DPCM (BDPCM), and benefits from texture information in a neighborhood to derive intensity levels of background and foreground layers. This information is used to reduce large rate of residual in case of incorrect layer prediction by BDPCM. For this purpose, three inter-layer transition states are defined that are either implicitly or explicitly conveyed to the decoder. Once a transition is signaled, the decoder corrects the prediction value using the derived layer information. Experiments on screen contents show a BD-rate gain of about 10% percent over VVC Test Model (VTM) and 1% over the regular BDPCM, with the cost of computational complexity.

Short-Distance Intra Prediction of Screen Content in Versatile Video Coding (VVC)

IEEE Signal Processing Letters, Nov 1, 2018

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Learning Semi-Supervised Anonymized Representations by Mutual Information

This paper addresses the problem of removing from a set of data (here images) a given private inf... more This paper addresses the problem of removing from a set of data (here images) a given private information, while still allowing other utilities on the processed data. This is obtained by training concurrently a GAN-like discriminator and an autoencoder. The optimization of the resulting structure involves a novel surrogate of the misclassification probability of the information to remove. Several examples are given, demonstrating that a good level of privacy can be obtained on images at the cost of the introduction of very small artifacts.

Multi-Packet HARQ with Delayed Feedback

In current wireless communication systems, the feedback required by the Hybrid Automatic ReQuest ... more In current wireless communication systems, the feedback required by the Hybrid Automatic ReQuest (HARQ) mechanism is received with some delay at the transmitter side. To alleviate this issue, parallel Stop-and-Wait HARQ is usually employed. In this paper, we propose a multi-packet HARQ protocol (also called superposition coding or multi-layer HARQ) to improve the user's delay distribution and increase the throughput, without any additional feedback such as Channel State Information. The performance analysis, provided from an informationtheoretic point-of-view, shows that the proposed protocol offers better delay distribution, higher throughput and lower message error rate compared to the conventional parallel Stop-and-Wait HARQ, at the expense of increased decoding complexity.

Distributed stochastic optimization in networks with low informational exchange

Wide-band, band-pass and versatile Hybrid Filter Bank A/D conversion for software radio

HAL (Le Centre pour la Communication Scientifique Directe), Aug 1, 2009

Throughput-efficient Relay assisted Hybrid ARQ

2018 15th International Symposium on Wireless Communication Systems (ISWCS), 2018

Reliable data transmission within wireless communication systems can be obtained via various mean... more Reliable data transmission within wireless communication systems can be obtained via various means, including (i) Hybrid Automatic Repeat reQuest (HARQ) mechanisms which allow retransmission of incorrectly decoded packets; (ii) Additional nodes, called relays, which may also help the transmission by retransmitting these packets. An efficient combination of both techniques is therefore of great interest. This paper investigates a relay assisted HARQ protocol aiming at maximizing the system throughput. The protocol allows the source to transmit a new message during the same time-slot in which the relay is retransmitting a previous message. By using an efficient interference canceler at the destination, the numerical results show significant throughput gain compared to standard approaches.

Finite-SNR analysis for partial relaying cooperation with channel coding and opportunistic relay selection

EURASIP Journal on Advances in Signal Processing, 2017

This work studies the performance of a cooperative network which consists of two channel-coded so... more This work studies the performance of a cooperative network which consists of two channel-coded sources, multiple relays, and one destination. To achieve high spectral efficiency, we assume that a single time slot is dedicated to relaying. Conventional network-coded-based cooperation (NCC) selects the best relay which uses network coding to serve the two sources simultaneously. The bit error rate (BER) performance of NCC with channel coding, however, is still unknown. In this paper, we firstly study the BER of NCC via a closed-form expression and analytically show that NCC only achieves diversity of order two regardless of the number of available relays and the channel code. Secondly, we propose a novel partial relaying-based cooperation (PARC) scheme to improve the system diversity in the finite signal-to-noise ratio (SNR) regime. In particular, closed-form expressions for the system BER and diversity order of PARC are derived as a function of the operating SNR value and the minimum distance of the channel code. We analytically show that the proposed PARC achieves full (instantaneous) diversity order in the finite SNR regime, given that an appropriate channel code is used. Finally, numerical results verify our analysis and demonstrate a large SNR gain of PARC over NCC in the SNR region of interest.

Semi-orthogonal MARC with half duplex relaying: A backward compatible cooperative network with interference channels

2016 IEEE 17th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), 2016

This paper proposes a full-rate cooperative scheme adapted to the slow fading semi-orthogonal mul... more This paper proposes a full-rate cooperative scheme adapted to the slow fading semi-orthogonal multiple access relay channel (MARC). It is assumed that the sources transmit on orthogonal channels and the relay is half duplex transmitting on the same channels as the one of the sources. The sources employ LDPC to encode their messages before transmitting them, while the relay uses a simple demodulate-and-forward strategy to transmit the combination of the received codewords. The presence of the relay does not affect the time-scheduling of the sources. Therefore, this scheme is backward compatible to existing noncooperative systems. In order to cancel the interference at the destination, we propose a joint network-channel decoder that uses maximum a posteriori (MAP) detection and channel decoding. Through numerical results, we show the benefits of joint network-channel decoder. We also show that the proposed scheme significantly outperforms, in terms of BER, the non-cooperative system as well as the classical relay-assisted orthogonal channel network and that it achieves the maximum code diversity.

Linear scalar quantization of wavelet image decomposition using joint optimization

2005 12th IEEE International Conference on Electronics, Circuits and Systems, 2005

This paper proposes a new linear scalar quantization algorithm. A modified Lloyd's optimum algori... more This paper proposes a new linear scalar quantization algorithm. A modified Lloyd's optimum algorithm, based on a linear quantization, is proposed to decompose a memoryless source into the bits. This is the case of the considered source which is the output of the wavelet transformation. The developed algorithm gives acceptable results for generalized Gaussian sources. Our approach is compared with the Lloyd max one's and a second one where the quantization intervals are equiprobable.

Rate Adaptation for Incremental Redundancy Secure HARQ

IEEE Transactions on Communications, Feb 1, 2016

This paper studies secure communication based on incremental redundancy (INR) secure hybrid autom... more This paper studies secure communication based on incremental redundancy (INR) secure hybrid automatic retransmission request (HARQ) protocol over block-fading wiretap channels. The transmitter has no instantaneous channel state information (CSI) available from either main channel or the eavesdropper channel, hence the coding rates cannot be adapted to instantaneous channel conditions. We investigate the outage performance for two schemes of INR secure HARQ protocols: case 1) when there exists two reliable multi-bit feedback channels from both legitimate receiver and eavesdropper to the transmitter carrying a function of outdated CSI, case 2) when there is a multi-bit feedback channel only from legitimate receiver. In both cases, we demonstrate that using the information carried via multi-bit feedback channels, the transmitter can adapt the coding rates in order to achieve a better secrecy throughput using a smaller number of transmissions comparing to the ACK/NACK feedback channel model. For some parameters, our rate adaptation protocol achieves a strictly positive secrecy throughput whereas it is equal to zero for the protocol with ACK/NACK feedback. We show that for some set of parameters, the loss of secrecy throughput between case 1 and case 2 is very small compared to the gain provided by both protocols.

Analysis of Multi-Messages Retransmission Schemes

Hybrid Automatic ReQuest (HARQ) protocol enables reliable communications in wireless systems. Usu... more Hybrid Automatic ReQuest (HARQ) protocol enables reliable communications in wireless systems. Usually, several parallel streams are sent in successive timeslots following a time-sharing approach. Recently, multi-layer HARQ has been proposed by superposing packets within a timeslot. In this paper, we evaluate the potential of this multi-layer HARQ by playing with some design parameters. We show that a gain in throughput is only obtained at mid-Signal-to-Noise Ratio (SNR).