A Multistage Method for SCMA Codebook Design Based on MDS Codes

Sparse Code Multiple Access (SCMA) has been recently proposed for the future generation of wireless communication standards. SCMA system design involves specifying several parameters. In order to simplify the procedure, most works consider a multistage design approach. Two main stages are usually emphasized in these methods: sparse signatures design (equivalently, resource allocation) and codebook design. In this paper, we present a novel SCMA codebook design method. The proposed method considers SCMA codebooks structured with an underlying vector space obtained from classical block codes. In particular, when using maximum distance separable (MDS) codes, our proposed design provides maximum signal-space diversity with a relatively small alphabet. The use of small alphabets also helps to maintain desired properties in the codebooks, such as low peak-to-average power ratio and low-complexity detection.Comment: Submitted to IEEE Wireless Communication Letter

Analyse de la structure des haies dans les vergers pour la définition de paysages mieux adaptés contre les bioagresseurs

National audienceAfin de modéliser la structure des haies de vergers, nous utilisons des méthodes de fouille de données. Ainsi, les chaînes de Markov couplées avec les chemins de Hilbert-Peano et les processus ponctuels servent à déterminer les paramètres propres à la disposition des haies dans le paysage. Ceci permet, par la suite, de simuler des paysages valides afin de créer des scénarios paysagers luttant contre les ravageur

On the equivalence of the self-dual and Maxwell-Chern-Simons models coupled to Fermions

We study the exact equivalence between the self-dual model minimally coupled with a Dirac field and the Maxwell-Chern-Simons model with non-minimal magnetic coupling to fermions. We show that the fermion sectors of the models are equivalent only if a Thirring like interaction is included. Using functional methods we verify that, up to renormalizations, the equivalence persists at the quantum level.Comment: 8 pages, revte

Forces and flow structures evolution on a car body in a sudden crosswind

A vehicle driver is commonly exposed to strong side air flows, for example when passing through a wind gust. The aerodynamic efforts generated in these situations may induce undesired lateral deviations, which can lead to dramatic effects, if the driver is surprised. In order to simulate a sudden yaw angle change on a moving vehicle, a double wind tunnel facility, adapted from the one of Ryan, Dominy, 2000. Wake Surveys Behind a Passenger Car Subjected to a Transient Cross-wind Gust. SAE Technical Paper No. 2000-01-0874 is developed. Two Windsor car body models, differing from their rear geometry, are analysed. The transient evolution of the side force and yaw moment aerodynamic coefficients are interpreted in connection with the unsteady development of the flow, based on TR-PIV and stereoscopic PIV measurements. Our analysis shows that the region which is most sensitive to crosswind is located at the rear part of the leeward flank. However, changes in the rear geometry (from squareback to fastback body) only affect the established lateral coefficients values while transient duration and the force overshoots appear not to be significantly modified. Furthermore, the circulation of the most energetic leeward vortex appears to be correlated with the lateral coefficients transient evolutions

Etude de l'évolution instationnaire de l'écoulement entourant un véhicule soumis brusquement à un vent latéral

Les techniques de PIV résolue en temps et de PIV stéréoscopique sont appliquées autour de corps automobiles soumis à un coup de vent latéral. Ainsi, l’évolution instationnaire des efforts aérodynamiques peut être interprétée en lien avec la topologie de l’écoulement. On montre en particulier que la réponse instationnaire du véhicule est dominée par le transitoire de la partie arrière. Le développement de la structure tourbillonnaire d’axe longitudinal apparaissant du côté sous le vent du véhicule soumis à un dérapage apparaît jouer un rôle important dans la réponse instationnaire de efforts aérodynamiques

VIRTUAL INTERACTIONS: CAN EEG HELP MAKE THE DIFFERENCE WITH REAL INTERACTION?

International audienceScience and technology progress fast, but mouse and keyboard are still used to control multimedia devices. One of the limiting factors of gesture based HCIs adoption is the detection of the user's intention to interact. This study tries to make a step in that direction with use of consumer EEG sensor headset. EEG headset records in real-time data that can help to identify intention of the user based on his emotional state. For each subject EEG responses for different stimuli are recorded. Acquiring these data allows to determine the potential of EEG based intention detection. The findings are promising and with proper implementation should allow to building a new type of HCI devices

LLM-based Interaction for Content Generation: A Case Study on the Perception of Employees in an IT department

In the past years, AI has seen many advances in the field of NLP. This has led to the emergence of LLMs, such as the now famous GPT-3.5, which revolutionise the way humans can access or generate content. Current studies on LLM-based generative tools are mainly interested in the performance of such tools in generating relevant content (code, text or image). However, ethical concerns related to the design and use of generative tools seem to be growing, impacting the public acceptability for specific tasks. This paper presents a questionnaire survey to identify the intention to use generative tools by employees of an IT company in the context of their work. This survey is based on empirical models measuring intention to use (TAM by Davis, 1989, and UTAUT2 by Venkatesh and al., 2008). Our results indicate a rather average acceptability of generative tools, although the more useful the tool is perceived to be, the higher the intention to use seems to be. Furthermore, our analyses suggest that the frequency of use of generative tools is likely to be a key factor in understanding how employees perceive these tools in the context of their work. Following on from this work, we plan to investigate the nature of the requests that may be made to these tools by specific audiences.Comment: 14 pages (bibliography inclued), 6 figures, preprint submitted to Work-In-Progress session of ACM IMX'23 Interactive Media Experienc

Study of depth bias of observers in free viewing of still stereoscopic synthetic stimuli

Observers’ fixations exhibit a marked bias towards certain areas on the screen when viewing scenes on computer monitors. For instance, there exists a well-known “center-bias” which means that fixations are biased towards the center of the screen during the viewing of 2D still images. In the viewing of 3D content, stereoscopic displays enhance depth perception by the mean of binocular parallax. This additional depth cue has a great influence on guiding eye movements. Relatively little is known about the impact of binocular parallax on visual attention of the 3D content displayed on stereoscopic screen. Several studies mentioned that people tend to look preferably at the objects located at certain positions in depth. But studies proving or quantifying this depth-bias are still limited. In this paper, we conducted a binocular eye-tracking experiment by showing synthetic stimuli on a stereoscopic display. Observers were required to do a free-viewing task through passive polarized glasses. Gaze positions of both eyes were recorded and the depth of eyes’ fixation was determined. The stimuli used in the experiment were designed in such a way that the center-bias and the depth-bias affect eye movements individually. Results indicate the existence of a depth-bias: objects closer to the viewer attract attention earlier than distant objects, and the number of fixations located on objects varies as a function of objects’ depth. The closest object in a scene always attracts most fixations. The fixation distribution along depth also shows a convergent behavior as the viewing time increases