Convergence des techniques de transmission fibre optique et radio MIMO haut débit

Pour répondre à l'accroissement de la demande en bande passante, de nouveaux réseaux optiques sont mis en place. Ce déploiement s'accompagne de la mise en service de nouveaux standards de fibres optiques, ce qui pose la question de l'utilisation et de la mise en valeur du réseau fibré existant, et notamment des fibres multimodes déjà installées, rapidement vouées à l'obsolescence. On cherche ainsi à mettre à profit la diversité spatiale que procure la nature multimode des ces fibres, via une analogie avec le domaine radiofréquences. L'utilisation des techniques MIMO, largement répandue dans le contexte de transmission radiofréquences, peut constituer une solution à cette amélioration nécessaire de la capacité de transmission de ces fibres optiques multimodes. Ce travail de thèse s'intéresse donc à l'étude et à la transposition des techniques MIMO dans le cadre de transmissions sur fibre optique et aux enjeux et défis associés. La transmission de signaux OFDM via un schéma de transmission SIMO optique permet de démontrer l'intérêt de la transposition des techniques MIMO à l'optique et la faisabilité de tels dispositifs.New technological uses such as cloud computing, smartphones, take part to the huge current increase of data consumption. This growth goes along with the development of optical networks, which will replace the copper networks with an higher and higher transmission capacity, thanks to new standards of fibers. This situation raises the question of the obsolete optical fibers reuse. It's shown in this thesis that MIMO techniques can be applied to multimode optical fibers in order to benefit from their inherent spatial diversity. This thesis focuses on the optical SIMO scheme, showing an improvement of the multimode fiber capacity for OFDM signals transmissions. We prove hereby the interest of such a technique, combining radio MIMO aspects and optical transmissions principles.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

A review of additive manufacturing of ceramics by powder bed selective laser processing (sintering / melting): Calcium phosphate, silicon carbide, zirconia, alumina, and their composites

This review offers an overview on the latest advances in the powder bed selective laser processing, known as selective laser sintering/melting, of calcium phosphate, silicon carbide, zirconia, alumina, and some of their composites. A number of published studies between 1991 and August 2020 was collected, analyzed and an inclusive state of the art was created for this review. The paper focuses on the process description, feedstock criteria and process parameters and strategy. A comparison is made between direct and indirect powder bed selective laser processing of each ceramic, regarding the present achievements, limitations and solutions. In addition, technical aspects and challenges about how to address these issues are presented

Zebularine, a DNA Methylation Inhibitor, Activates Anthocyanin Accumulation in Grapevine Cells

Through its role in the regulation of gene expression, DNA methylation can participate in the control of specialized metabolite production. We have investigated the link between DNA methylation and anthocyanin accumulation in grapevine using the hypomethylating drug, zebularine and Gamay Teinturier cell suspensions. In this model, zebularine increased anthocyanin accumulation in the light, and induced its production in the dark. To unravel the underlying mechanisms, cell transcriptome, metabolic content, and DNA methylation were analyzed. The up-regulation of stress-related genes, as well as a decrease in cell viability, revealed that zebularine affected cell integrity. Concomitantly, the global DNA methylation level was only slightly decreased in the light and not modified in the dark. However, locus-specific analyses demonstrated a decrease in DNA methylation at a few selected loci, including a CACTA DNA transposon and a small region upstream from the UFGT gene, coding for the UDP glucose:flavonoid-3-O-glucosyltransferase, known to be critical for anthocyanin biosynthesis. Moreover, this decrease was correlated with an increase in UFGT expression and in anthocyanin content. In conclusion, our data suggest that UFGT expression could be regulated through DNA methylation in Gamay Teinturier, although the functional link between changes in DNA methylation and UFGT transcription still needs to be demonstrated

2 -La conscience phonologique chez les enfants

Maury Ghislaine. 2 -La conscience phonologique chez les enfants. In: Repères pour la rénovation de l'enseignement du français à l'école élémentaire, n°19, 1973. pp. 14-15

Receiver Sensitivity Improvement for IoT

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Enhancement of the Sensitivity of a Digital Receiver by Time Synchronous Averaging

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Synchronization for Coherent Averaging Based Communication Systems

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Spectrally Augmented Hartley Transform Precoded Asymmetrically Clipped Optical OFDM for VLC

International audienceIn this letter, layered discrete Hartley transform (DHT)-spread asymmetrically clipped optical-orthogonal frequency division multiplexing (LDHTS-ACO-OFDM) is presented; it uses DHT for multiplexing/demultiplexing and pulse-amplitude modulation (PAM) alphabets. LDHTS-ACO-OFDM yields several concrete enhancements over classical layered asymmetrically clipped O-OFDM (LACO-OFDM), such as low peak-to-average power ratio (PAPR), lower computational complexity, improved bit error rate (BER), and lower optical power penalty in a dispersive channel. Besides, LDHTS-ACO-OFDM augments the spectral efficiency relative to DHTS-ACO-OFDM with each addition of layer and ousts the inefficient bandwidth utilization limitation of DHTS-ACO-OFDM

Hermitian symmetry free optical-single-carrier frequency division multiple access for visible light communication

International audienceOptical-orthogonal frequency division multiplexing (O-OFDM) is an effective scheme for visible light communications (VLC), offering a candid extension to multiple access (MA) scenarios, i.e., O-OFDMA. However, O-OFDMA exhibits high peak-to-average power ratio (PAPR), which exacerbates the non-linear distortions from the light emitting diode (LED). To overcome high PAPR while sustaining MA, optical-single-carrier frequency-division multiple access (O-SCFDMA) is used. For both O-OFDMA and O-SCFDMA, Hermitian symmetry (HS) constraint is imposed in frequency-domain (FD) to obtain a real-valued time-domain (TD) signal for intensity modulation-direct detection (IM-DD) implementation of VLC. Howbeit, HS results in an increase of PAPR for O-SCFDMA. In this regard, we propose HS free (HSF) O-SCFDMA (HSFO-SCFDMA). We compare HSFO-SCFDMA with several approaches in key parameters, such as, bit error rate (BER), optical power penalty, PAPR, quantization, electrical power efficiency and system complexity. BER performance and optical power penalty is evaluated considering multipath VLC channel and taking into account the bandwidth limitation of LED in combination with its optimized driver. It is illustrated that HSFO-SCFDMA outperforms other alternatives

Enhanced DC-biased optical OFDM for intensity-modulated optical OFDM access systems

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