Combination of Space-Time Block Coding with MC-CDMA Technique for MIMO systems with two, three and four transmit antennas

For future wideband wireless networks, space diversity schemes relying on multiple antennas at the receiver and/or at the transmitter are very attractive to combat fadings and improve the transmission performance. In this paper, Multi-Carrier Code Division Multiple Access (MC-CDMA) technique combined with several Space-Time Block Codes (STBC) is analyzed in the case of Nt transmit antennas and Nr receive antennas to provide a diversity order of NtNr for a 2 bps/Hz spectral efficiency. A general method to decode STBC from orthogonal designs associated with MC-CDMAis proposed. Two Single-user Detection techniques, Zero Forcing (ZF) and Minimum Mean Square Error (MMSE), are studied and compared in the downlink synchronous case over frequency selective Rayleigh channels

Codage temps-espace en blocs combiné avec un système multiporteuse à étalement de spectre de type MC-CDMA

Ce papier présente les performances de systèmes MIMO MC-CDMA à Nt antennes d'émission et Nr antennes de réception offrant une efficacité spectrale de 1 ou 2 bit/s/Hz. Les résultats sont obtenus pour différents schémas de codage temps-espace en blocs (STBC) dans le cas de la liaison descendante synchrone sur des canaux de Rayleigh sélectifs en fréquence pour les deux techniques de détection Zéro-Forcing (ZF) et Minimum Mean Square Error (MMSE). En outre, une méthode générale pour décoder les codes STBC orthogonaux associés aux signaux MC-CDMA est décrite. Par ailleurs, ces résultats démontrent l'intérêt d'un système STBC MC-CDMA reposant sur l'utilisation de codes temps-espace de rendement 1, et qu'il est en conséquence préférable d'utiliser la redondance au niveau du codage de canal et non au niveau du codage temps-espace

Les effets-frontière : évidences empiriques, impasses théoriques

Construction européenne à l'Ouest, ouverture politique et économique à l'Est, évolution des modes de vie, internationalisation de la production et des marchés, l'air du temps est à la croissance des trafics internationaux... Le politique, le professionnel de la frontière, le technicien, l'usager des transports, tous sont alors en droit de s'interroger sur l'évolution de ces flux entre Etats, tous peuvent légitimement se préoccuper des menaces de saturation prochaine d'infrastructures majeures de transport.Or, la connaissance des niveaux, des formes et surtout des déterminants des flux entre Etats demeure encore très lacunaire dans le champ de la socio-économie des transports. Le concept généralement avancé pour saisir la spécificité de ces flux est l'effet-frontière, facteur d'abaissement du trafic constaté empiriquement lors du franchissement d'une frontière. Mais si le concept paraît séduisant (quoi de plus normal, après tout, qu'une frontière implique des effets-frontières ?), est-il pour autant pertinent ?commerce international ; effet frontière ; trafic international ; transport international ; trafic de marchandises ; trafic de voyageurs ; évolution

Large-Scale Cortical Dynamics of Sleep Slow Waves

Slow waves constitute the main signature of sleep in the electroencephalogram (EEG). They reflect alternating periods of neuronal hyperpolarization and depolarization in cortical networks. While recent findings have demonstrated their functional role in shaping and strengthening neuronal networks, a large-scale characterization of these two processes remains elusive in the human brain. In this study, by using simultaneous scalp EEG and intracranial recordings in 10 epileptic subjects, we examined the dynamics of hyperpolarization and depolarization waves over a large extent of the human cortex. We report that both hyperpolarization and depolarization processes can occur with two different characteristic time durations which are consistent across all subjects. For both hyperpolarization and depolarization waves, their average speed over the cortex was estimated to be approximately 1 m/s. Finally, we characterized their propagation pathways by studying the preferential trajectories between most involved intracranial contacts. For both waves, although single events could begin in almost all investigated sites across the entire cortex, we found that the majority of the preferential starting locations were located in frontal regions of the brain while they had a tendency to end in posterior and temporal regions

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Évaluations et contractualisation : nécessité de dépasser les injonctions institutionnelles pour faire vivre un projet innovant

International audienc