Publications

2018

• On BlockChain Technology: Overview of Bitcoin and Future Insights
  
  • Hellani Hussein
  • Samhat Abed Ellatif
  • Chamoun Maroun
  • Ghor Hussein El
  • Serhrouchni Ahmed
  , 2018, pp.1-8. In this paper, we consider blockchain technology that enabledthe existence of digital currency and we investigate Bitcoin cryptocurrency application. This technology nowadays represents a new feature that replaces existing client-server core system on top of some distributed systems with many additional features such as high availability, resistance to alteration, fault tolerance and cost reduction. After overviewing how such technology is working, we highlightthe requirements and benefits related to the security, database and network. We mainly focus on answering the most Bitcoin queries including privacy and double spending. Furthermore, as blockchain has potential applications far beyond bitcoin, we draw future insights where applications based blockchain are provisioned in the market in order to be totally or partially independent of the centralized systems and we provide a questionnaire helping organizations for better using the blockchain feasibilities. (10.1109/IMCET.2018.8603029)
  DOI : 10.1109/IMCET.2018.8603029
• Mixed-Signal Predistortion for Small-Cell 5G Wireless Nodes
  
  • Manyam Venkata Narasimha
  , 2018. Small-cell base stations (picocells and femtocells) handling high bandwidths (> 100 MHz) will play a vital role in realizing the 1000X network capacity objective of the future 5G wireless networks. Power Amplifier (PA) consumes the majority of the base station power, whose linearity comes at the cost of efficiency. With the increase in bandwidths, PA also suffers from increased memory effects. Digital predistortion (DPD) and analog RF predistortion (ARFPD) tries to solve the linearity/efficiency trade-off. In the context of 5G small-cell base stations, the use of conventional predistorters becomes prohibitively power-hungry.Memory polynomial (MP) model is one of the most attractive predistortion models, providing significant performance with very few coefficients. We propose a novel FIR memory polynomial (FIR-MP) model which significantly augments the performance of the conventional memory polynomial predistorter. Simulations with models extracted on ADL5606 which is a 1 W GaAs HBT PA show improvements in adjacent channel leakage ratio (ACLR) of 7.2 dB and 15.6 dB, respectively, for 20 MHz and 80 MHz signals, in comparison with MP predistorter. Digital implementation of the proposed FIR-MP model has been carried out in 28 nm FDSOI CMOS technology. With a fraction of the power and die area of that of the MP a huge improvement in ACLR is attained.An overall estimated power consumption of 9.18 mW and 116.2 mW, respectively, for 20 MHz and 80 MHz signals is obtained.Based on the proposed FIR-MP model a novel low-power mixed-signal approach to linearize RF power amplifiers (PAs) is presented. The digital FIR filter improves the memory correction performance without any bandwidth expansion and the MP predistorter in analog baseband provides superior linearization. MSPD avoids 5X bandwidth requirement for the DAC and reconstruction filters of the transmitter and the power-hungry RF components when compared to DPD and ARFPD, respectively.The impact of various non-idealities is simulated with ADL5606 (1 W GaAs HBT PA) MP PA model using 80 MHz modulated signal to derive the requirements for the integrated circuit implementation. A resolution of 8 bits for the coefficients and a signal path SNR of 60 dB is required to achieve ACLR1 above 45 dBc, with as little as 9 coefficients in the analog domain. Discussion on the potential circuit architectures of subsystems is provided. It results that an analog implementation is feasible. It will be worth in the future to continue the design of this architecture up to a silicon prototype to evaluate its performance and power consumption.
• Mixed-signal predistortion for small-cell 5G wireless nodes
  
  • Manyam Venkata Narasimha
  , 2018. Small-cell base stations (picocells and femtocells) handling high bandwidths (> 100 MHz) will play a vital role in realizing the 1000X network capacity objective of the future 5G wireless networks. Power Amplifier (PA) consumes the majority of the base station power, whose linearity comes at the cost of efficiency. With the increase in bandwidths, PA also suffers from increased memory effects. Digital predistortion (DPD) and analog RF predistortion (ARFPD) tries to solve the linearity/efficiency trade-off. In the context of 5G small-cell base stations, the use of conventional predistorters becomes prohibitively power-hungry.Memory polynomial (MP) model is one of the most attractive predistortion models, providing significant performance with very few coefficients. We propose a novel FIR memory polynomial (FIR-MP) model which significantly augments the performance of the conventional memory polynomial predistorter. Simulations with models extracted on ADL5606 which is a 1 W GaAs HBT PA show improvements in adjacent channel leakage ratio (ACLR) of 7.2 dB and 15.6 dB, respectively, for 20 MHz and 80 MHz signals, in comparison with MP predistorter. Digital implementation of the proposed FIR-MP model has been carried out in 28 nm FDSOI CMOS technology. With a fraction of the power and die area of that of the MP a huge improvement in ACLR is attained.An overall estimated power consumption of 9.18 mW and 116.2 mW, respectively, for 20 MHz and 80 MHz signals is obtained.Based on the proposed FIR-MP model a novel low-power mixed-signal approach to linearize RF power amplifiers (PAs) is presented. The digital FIR filter improves the memory correction performance without any bandwidth expansion and the MP predistorter in analog baseband provides superior linearization. MSPD avoids 5X bandwidth requirement for the DAC and reconstruction filters of the transmitter and the power-hungry RF components when compared to DPD and ARFPD, respectively.The impact of various non-idealities is simulated with ADL5606 (1 W GaAs HBT PA) MP PA model using 80 MHz modulated signal to derive the requirements for the integrated circuit implementation. A resolution of 8 bits for the coefficients and a signal path SNR of 60 dB is required to achieve ACLR1 above 45 dBc, with as little as 9 coefficients in the analog domain. Discussion on the potential circuit architectures of subsystems is provided. It results that an analog implementation is feasible. It will be worth in the future to continue the design of this architecture up to a silicon prototype to evaluate its performance and power consumption.
• Archives, fragments Web et diasporas : pour une exploration désagrégée de corpus d'archives Web liées aux représentations en ligne des diasporas
  
  • Lobbe Quentin
  , 2018. Le Web est un environnement éphémère. Alors que de nouveaux sites Web émergent chaque jour, il arrive que certaines communautés disparaissent entièrement de la surface de la toile, ne laissant derrière elles que des traces incomplètes voire inexistantes. Face à la volatilité du Web vivant, plusieurs initiatives d’archivage cherchent malgré tout à préserver la mémoire du Web passé. Mais aujourd’hui, force est de constater qu’un mystère demeure : Pourquoi, alors qu’elles n’ont jamais été aussi vastes et aussi nombreuses, les archives Web ne font-elles pas déjà l’objet de multiples recherches historiques ? Initialement construites pour inscrire la mémoire de la toile sur un support durable, ces archives ne doivent pourtant pas être considérées comme une représentation fidèle du Web vivant. Elles sont les traces directes des outils de collecte qui les arrachent à leur temporalité d’origine. Partant de là, cette thèse ambitionne de redonner aux chercheurs les moyens théoriques et techniques d’une plus grande maniabilité du Web passé, en définissant une nouvelle unité d’exploration des archives Web : le fragment Web, un sous-ensemble cohérent et auto-suffisant d’une page Web. Pour ce faire, nous nous inscrirons dans l’héritage des travaux pionniers de l’Atlas e-Diasporas qui permit, dans les années 2000, de cartographier et d’archiver plusieurs milliers de sites Web migrants. Source principale de données à partir desquelles nous déploierons nos réflexions, c’est à travers l’angle particulier des représentations en ligne des diasporas que nous chercherons à explorer les archives Web de l’Atlas.
• Procédé de gestion d’un message transmis par une station émettrice d’un système de transport intelligent
  
  • Monteuuis Jean-Philippe
  • Zhang Jun J.
  • Labiod Houda
  • Servel Alain
  • Mafrica Stefano
  , 2018.
• Sociabilités en ligne, usages et réseaux
  
  • Charbey Raphaël
  , 2018. Avec l’avènement du numérique, il est désormais possible aux chercheurs d’amasser des grandes quantités de données et les plateformes de réseaux sociaux en ligne ne font pas exception à cela. Les sociologues, comme d’autres, se sont emparés de ces nouvelles ressources afin de poursuivre leurs enquêtes sur les modalités de l’interaction entre individus et leur impact sur la structuration de la sociabilité. Suivant cette voie, ce travail de thèse vise à l’analyse d’un grand nombre de comptes Facebook, aussi bien au travers des outils classiques de l’analyse de données que de la théorie des graphes, à laquelle des contributions méthodologiques sont apportées. Deux facteurs principaux encouragent l’étude de l’activité et de la sociabilité en ligne. D’une part, le temps important dédié à cette plateforme par de nombreux internautes justifie l’intérêt porté par les sociologues aux échanges qui s’y construisent. Par ailleurs, et contrairement à ce que l’on peut observer sur d’autre sites de réseaux sociaux en ligne, les liens entre individus sur Facebook sont proches de ceux hors-lignes. Dans un premier temps, la thèse s’évertue à démêler les multiples facettes de ce à quoi ”être sur Facebook” correspond. Distribués autour de pratiques normatives fabulées, les usages de nos enquêtés fluctuent au gré de leur appropriation ou non des composantes de l’importante variété de moyens de communication proposés par la plateforme. Ces usages, comme on le verra, sont ainsi différemment adoptés selon les catégories socioprofessionnelles et influent par ailleurs sur les modalités d’échanges et d’interactions des enquêtés avec leurs amis en ligne. Ces modalités sont également explorées dans ce travail, tout comme le rôle du conjoint et sa place dans la structure relationnelle. La seconde partie de la thèse se propose de construire une typologie de ces structures relationnelles dites égocentrées, c’est-à-dire depuis le point de vue de l’enquêté. Cette typologie des réseaux de sociabilité en ligne se base sur l’énumération de leurs sous-graphes induits, les graphlets, initialement développée par des chercheurs en bioinformatique. Cette approche offre une vision méso (entre micro et macro) des réseaux, propice à souligner des phénomènes inédits de sociologie des réseaux. A fort potentiel pluri-disciplinaire, la méthodologie graphlets elle même est également discutée et explorée.
• Identify, locate and separate: Audio-visual object extraction in large video collections using weak supervision
  
  • Parekh Sanjeel
  • Ozerov Alexey
  • Essid Slim
  • Duong Ngoc Q. K.
  • Pérez Patrick
  • Richard Gael
  , 2018. We tackle the problem of audiovisual scene analysis for weakly-labeled data. To this end, we build upon our previous audiovisual representation learning framework to perform object classification in noisy acoustic environments and integrate audio source enhancement capability. This is made possible by a novel use of non-negative matrix factorization for the audio modality. Our approach is founded on the multiple instance learning paradigm. Its effectiveness is established through experiments over a challenging dataset of music instrument performance videos. We also show encouraging visual object localization results.
• Optimal Content Management and Dimensioning in Wireless Networks
  
  • Krolikowski Jonatan
  , 2018. The massive increase in cellular traffic poses serious challenges to all actors concerned with wireless content delivery. While network densification provides access to additional users, high-speed and high-capacity backhaul connections are expensive. Caching popular content at the network edge promises to offload user traffic from these congestion prone connections as well as from the data centers in the backbone network. This thesis proposes a business model in which a mobile network operator (MNO) pre-installs and maintains caches at its wireless equipment (Cache-equipped Base Stations, CBSs). Memory space together with computational capabilities is then leased to content providers (CPs) that want to bring their content closer to the user. For a financial compensation, a CP can then offload traffic from its data center and improve user Quality of Service. The CP makes content placement decisions based on predictive user traffic and content popularity data. In the delivery phase, users can be served from the caches in case they are associated to stations that have the requested content cached. This work investigates three aspects of the proposed business model: The first research question focuses on user association as a central element to the edge caching scheme. Cache-aware user association policies can allow for users in coverage overlap areas to be associated to a CBS that holds the requested content rather than conventionally to the one that provides the strongest signal. The thesis proposes an original decentralized algorithm for user association called Generalized Bucket-filling that allows gains beyond maximizing the hit ratio. Performance metrics such as network throughput and load balancing of users among CBSs are taken into account. Experiments show that cache-aware user association a) increases the hit ratio b) without overloading single CBSs while c) providing high system throughput. The second problem treated considers a single CP that needs to decide how much cache space to lease at each CBS for a fixed price, and what content to place. Its choices should be based on estimates of file popularity as well as MNO user association policy. The cache leasing and content placement problem is formulated as a non-linear mixed-integer problem (NLMIP). In its solution, the problem is separated into a linear discrete CP subproblem and a nonlinear continuous subproblem using Benders decomposition. The CP and the MNO cooperate, helping the CP to make optimal decisions that benefit both parties: The CP maximizes its savings from caching while the MNO can find the optimal cache price and receive the maximum financial compensation. A third research question widens the focus to the interaction between several CPs and one MNO. Now, the MNO does not set a fixed price per memory unit but instead reacts to CP demands for memory space that depend on the savings they can achieve from caching.
• Cross-layer optimization of cooperative and coordinative schemes for next generation cellular networks
  
  • Khreis Alaa
  , 2018. HARQ has become an important research field in the wireless digital communications area during the last years. In this thesis, we improve the HARQ mechanisms in terms of throughput and/or latency which are the bottleneck of next generation wireless communication systems. More precisely, we improve the time-slotted HARQ systems by mimicking NOMA, which means using superposed packets in a single-user context. In the first part of the thesis, we propose HARQ protocols using the help of a relay to improve the transmission rate and reliability. An enhanced HARQ protocol adapted to delayed feedback is proposed in the second part. In this new multi-layer HARQ protocol, additional redundant packets are sent preemptively before receiving the acknowledgement, and in superposition to other HARQ processes.
• Is Two Better than One?
  
  • Kantharaju Reshmashree B
  • de Franco Dominic
  • Pease Alison
  • Pelachaud Catherine
  , 2018, pp.255-262. (10.1145/3267851.3267890)
  DOI : 10.1145/3267851.3267890
• Noisy Broadcast Networks With Receiver Caching
  
  • Saeedi Bidokhti Shirin
  • Wigger Michèle
  • Timo Roy
  IEEE Transactions on Information Theory, Institute of Electrical and Electronics Engineers, 2018, 64 (11), pp.6996-7016. An erasure broadcast network is considered with two disjoint sets of receivers: a set of weak receivers with all-equal erasure probabilities and equal cache sizes and a set of strong receivers with all-equal erasure probabilities and no cache memories. Lower and upper bounds are presented on the capacity-memory tradeoff of this network (the largest rate at which messages can be reliably communicated for given cache sizes). The lower bound is achieved by means of a joint cache-channel coding scheme and significantly improves over traditional schemes based on the separate cache-channel coding. In particular, it is shown that the joint cache-channel coding offers new global caching gains that scale with the number of strong receivers in the network. The upper bound uses bounding techniques from degraded broadcast channels and introduces an averaging argument to capture the fact that the contents of the cache memories are designed before knowing users' demands. The derived upper bound is valid for all stochastically degraded broadcast channels. The lower and upper bounds match for a single weak receiver (and any number of strong receivers) when the cache size does not exceed a certain threshold. Improved bounds are presented for the special case of a single weak and a single strong receiver with two files and the bounds are shown to match over a large range of cache sizes. (10.1109/TIT.2018.2835507)
  DOI : 10.1109/TIT.2018.2835507
• Fine-Grained Detection of Inverse Tone Mapping in HDR Images
  
  • Fan Wei
  • Valenzise Giuseppe
  • Banterle Francesco
  • Dufaux Frédéric
  Signal Processing, Elsevier, 2018, 152, pp.178-188. High dynamic range (HDR) imaging enables to capture the full range of physical luminance of a real-world scene, and is expected to progressively replace traditional low dynamic range (LDR) pictures and videos. Despite the increasing HDR popularity, very little attention has been devoted to new forensic problems that are characteristic to this content. In this paper, we address for the first time such kind of problem, by identifying the source of an HDR picture. Specifically, we consider the two currently most common techniques to generate an HDR image: by fusing multiple LDR images with different exposure time, or by inverse tone mapping an LDR picture. We show that, in order to apply conventional forensic tools to HDR images, they need to be properly preprocessed, and we propose and evaluate a few simple HDR forensic preprocessing strategies for this purpose. In addition, we propose a new forensic feature based on Fisher scores, calculated under Gaussian mixture models. We show that the proposed feature outperforms the popular SPAM features in classifying the HDR image source on image blocks as small as 3 × 3, which makes our method suitable to detect composite forgeries combining HDR patches originating from different acquisition processes. (10.1016/j.sigpro.2018.05.028)
  DOI : 10.1016/j.sigpro.2018.05.028
• La programmation orientée modèles au service des télécommunications mobiles
  
  • Enrici Andrea
  • Apvrille Ludovic
  • Pacalet Renaud
  • Roullet Laurent
  Programmez !, Magazine Programmez, 2018, pp.36-44. Les besoins croissants en termes de latence, débit et flexibilité des réseaux futurs poussent les architectures distribuées des réseaux d’accès radio actuels à évoluer vers des architectures plus centralisées qui reposent sur les paradigmes de l’informatique en nuage (=cloud, NDLR). Au sein de ces nouvelles architectures, le traitement du signal numérique s’effectue sur des matériels hétérogènes (processeurs généralistes, circuits dédiés à hautes performances tels des FPGA ou des GPU). De nombreuses questions restent ouvertes à propos de tels systèmes hétérogènes. En particulier, comment les programmer de façon efficace ?
• Near-Optimal Detection of TAST Codes Over Multimode Optical Fiber Channels
  
  • Damen Mohamed Oussama
  • Rekaya-Ben Othman Ghaya
  , 2018.
• Compression adaptative d'hologrammes numériques en utilisant la technique du Matching Pursuit
  
  • El Rhammad Anas
  • Gioia Patrick
  • Gilles Antonin
  • Cagnazzo Marco
  , 2018.
• Reference list optimization for improvement of compression of 2D-multiview content for free-navigation applications
  
  • Nikitin Pavel
  • Jung Joel
  • Cagnazzo Marco
  , 2018.
• Explanatory relations in arbitrary logics based on satisfaction systems, cutting and retraction
  
  • Aiguier Marc
  • Atif Jamal
  • Bloch Isabelle
  • Pino Perez Ramon
  International Journal of Approximate Reasoning, Elsevier, 2018, 102, pp.1 - 20. (10.1016/j.ijar.2018.07.014)
  DOI : 10.1016/j.ijar.2018.07.014
• High-Speed Software Data Plane via Vectorized Packet Processing
  
  • Barach David
  • Linguaglossa Leonardo
  • Marion Damjan
  • Pfister Pierre
  • Pontarelli Salvatore
  • Rossi Dario
  IEEE Communications Magazine, Institute of Electrical and Electronics Engineers, 2018, 56 (12), pp.97 - 103.
• Snake: a stochastic proximal gradient algorithm for regularized problems over large graphs
  
  • Salim Adil
  • Bianchi Pascal
  • Hachem Walid
  IEEE Transactions on Automatic Control, Institute of Electrical and Electronics Engineers, 2018.
• Multilevel MIMO detection with deep learning
  
  • Corlay Vincent
  • Boutros Joseph
  • Ciblat Philippe
  • Brunel Loïc
  , 2018.
• Low-frequency fluctuations of a mid-infrared quantum cascade laser operating at cryogenic temperatures
  
  • Spitz Olivier
  • Wu Jiagui
  • Carras Mathieu
  • Wong Chee-Wei
  • Grillot Frederic
  Laser Physics Letters, IOP Publishing, 2018, 15 (11), pp.116201. This work demonstrates that mid-infrared quantum cascade lasers operating under external optical feedback can output a chaotic dynamics through low-frequency fluctuations close to 77 K. Results also show that the birth of chaotic dynamics is not limited to near-threshold pumping levels. In addition, when the semiconductor material is cooled down from room temperature to 77 K, it is found that the laser destabilization takes place at a lower feedback ratio which proves that quantum cascade lasers are sensitive to temperatures, likely due to changes in the upper state lifetime. These examinations are meaningful for chaotic operation of quantum cascade lasers in secure atmospheric transmission lines and optical countermeasure systems. (10.1088/1612-202X/aadc5a)
  DOI : 10.1088/1612-202X/aadc5a
• Disfluencies and Teaching Strategies in Social Interactions Between a Pedagogical Agent and a Student: Background and Challenges
  
  • Dinkar Tanvi
  • Vasilescu Ioana
  • Pelachaud Catherine
  • Clavel Chloé
  , 2018, pp.188-191. <p>This paper i) Presents the related work and the challenges regarding the integration of disfluencies in human-agent interactions and, ii) Positions the context and motivations behind ourproject.</p>
• Video conference in the fog: an economical approach based on enterprise desktop grid
  
  • Sorokin Roman
  • Rougier Jean-Louis
  Annals of Telecommunications - annales des télécommunications, Springer, 2018. There exist two classical and well-understood approaches to video-processing tasks (such as mixing or trans-coding) for videoconferencing. The first one is using a centralized multipoint control unit (MCU), hardware- or software-based, deployed on-premises or in the cloud. In the second approach, the video-processing tasks are directly handled in endpoints (i.e., equipment such as PCs, laptops, and tablets that are involved in the video session). Performance is then restricted by device characteristics, especially in the case of mobile devices. In this paper, we propose a third alternative approach. It has been shown that there exist significant computational resources in user equipment deployed in enterprises, which are under-utilized most of the time. In this paper, we propose a system, which distributes real-time video-processing tasks on these available resources. A dedicated multi-attribute decision-making (MADM) method is designed in order to take into account the variety of attributes impacting Quality of Experience. We enumerate a comprehensive list of events, which may cause distribution or redistribution of video-processing activities and provide simple algorithms to tackle all these cases. We then test the MADM algorithm by means of simulations in order to study the impact of the main critical parameters. (10.1007/s12243-017-0613-4)
  DOI : 10.1007/s12243-017-0613-4
• Energy-Latency Tradeoff in Ultra-Reliable Low-Latency Communication with Retransmissions
  
  • Avranas Apostolos
  • Kountouris Marios
  • Ciblat Philippe
  IEEE Journal on Selected Areas in Communications, Institute of Electrical and Electronics Engineers, 2018, 36 (11), pp.2475-2485.
• This is IT: A Primer on Shannon's Entropy and Information
  
  • Rioul Olivier
  , 2018.