Adaptation de la stratégie de retransmission dans le protocole HARQ.

Le Protocole HARQ (Hybrid Automatic Repeat reQuest) permet d'améliorer la fiabilité de la communication par le renvoi des acquittements sur les paquets transmis, et retransmettre ceux-ci si nécessaire. Ainsi, l'HARQ combine les deux mécanismes de contrôle d'erreurs: ARQ (Automatic Repeat reQuest) et FEC (Forward Error Correction) afin d'offrir un service plus performant. Dans ce travail on considère l'HARQ avec la redondance incrémentale (IR) dans un canal à évanouissement par blocs. On considère une communication point à point où l'émetteur n'a aucune information sur l'état actuel du canal, tandis que l'état antérieur lui est connu. Basé sur cette information, l'émetteur choisit une stratégie de retransmission, si un NACK (Negative Acknowledgement) est reçu, pour maximiser le débit du système. L'ensemble de stratégies est principalement composé de deux catégories : la retransmission classique, ou bien, le multiplexage des deux paquets en une transmission. Ce multiplexage est fait soit par le partage du temps (TS) ou bien en superposant les codes (SC). L'objectif de ce travail est de proposer un protocole basé sur l'HARQ qui permettra d'ajuster les paramètres de la transmission en tenant compte de l'état précédent du canal. Pour cela, on propose d'utiliser le modèle du Processus de Décision Markovien (MDP). Les résultats numériques obtenus pour un canal Rayleigh montrent qu'on peut atteindre un meilleur débit que celui de l'HARQ conventionnel (on obtiens un gain qui peut atteindre 12%)

The structure and regulation of the Irish equine industries: Links to considerations of equine welfare

The equine industries in Ireland are vibrant and growing. They are broadly classified into two sectors: Thoroughbred racing, and sports and leisure. This paper describes these sectors in terms of governance, education and training in equine welfare, and available data concerning horse numbers, identification, traceability and disposal. Animal welfare, and specifically equine welfare, has received increasing attention internationally. There is general acceptance of concepts such as animal needs and persons' responsibilities toward animals in their care, as expressed in the 'Five Freedoms'. As yet, little has been published on standards of equine welfare pertaining to Ireland, or on measures to address welfare issues here. This paper highlights the central role of horse identification and legal registration of ownership to safeguard the health and welfare of horses

Alternating MSA and Mo-QEA to Design Slow-Time Coded PRF-Set in Pulse-Doppler Radar

In this paper, we propose a novel framework based on a multivariable hybrid optimization algorithm that integrates single-objective modified simulated annealing (MSA) and multi-objective quantum-inspired evolutionary algorithm (Mo-QEA) layers based on the impact of the slow-time phase coding for minimizing unwanted signals at the output of matching filters, on the frequency spectrum of pulsed-Doppler radars. Slow-time codes alter the spectrum’s structure and result in increasing the blind areas within the blind-zone map (BZM). The hybrid framework comprises two layers that identify the optimum pulse repetition frequency (PRF) set and slow-time code by considering spectrum disturbances. The first layer employs the MSA for PRF set optimization. Modifications to the SA include restructured loops based on the perturbation functions. The outer loop considers the overall PRF set structure (overall direction and step—ODS), while the inner loop conducts a sequential search based on the cost function’s standard deviation and small increments. The output of this layer serves as the foundation for the subsequent layer, where the phase sequence of each PRF is optimized to concurrently minimize blind areas due to the M of N criterion and grating lobes through Mo-QEA. Innovations are mutation-like operators and tournament selection to enhance the diversity of generated solutions, alongside rotation gates in quantum computing. Our research highlights a previously unexplored relationship between BZM and slow-time coding, demonstrating improved performance for each layer compared to existing studies

Minimizing ISL in DFT-Spread OFDM Radar Using Complementary Overlaying and Greedy-MSA Optimization

This paper proposes a new scheme of discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing (OFDM) radar waveform design for system unwanted signal levels decreasing at the receiver. The proposed method mitigates limitations like grating lobe formation and reduced range resolution in interleaved frequency division multiplexing (IFDM). It also addresses high-range side lobes and signal amplitude fluctuations common in conventional OFDM radars. The proposed approach is divided into two sections: First, design a sequence of bi-phase elements as primal part of transmitted waveform and minimize its’ auto-correlation integrated side lobe level (ISL) through a modified simulated annealing algorithm based on a greedy search (greedy-MSA). Refinements have been made to various aspects of the SA algorithm: the initial temperature to adjust acceptance probability, the perturbation function to increase the diversity of generated solutions, and the local probing strategy with sequential search to improve solution effectiveness—Secondly, we employ a frequency multiplexing approach based on interleaved DFT-spreading to positioning it as a viable candidate solution for joint radar communication (JRC) applications due to OFDM drawbacks. The main contribution of this section is the elimination of auto-correlation grating lobes in the IFDM waveform. This is achieved through time-domain modifications of the waveform by overlaying a phase sequence onto the outer frame while preserving the auto-correlation characteristics of the primal phase sequence. Simulation results demonstrate that our methodology significantly surpasses existing techniques in decreasing unwanted signal levels

Excellence in animal transportation Looking to the future

SIGLEAvailable from British Library Document Supply Centre-DSC:99/36162 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Propensity Score Matching Analysis of the Association between Instructor Competence and Utilization of Digital Tools in TVET Institutions of Uganda

The effectiveness of online teaching in Technical and Vocational Education and Training (TVET) institutions largely depends on instructor competence in utilizing digital gadgets. This paper utilizes the Propensity Score Matching model to examine the association between instructor digital gadgets utilization competence and online teaching/learning among selected TVET institutions. This paper presents and emphasizes the critical role of digital competence among instructors as a necessary condition for online teaching. A cross-sectional survey design was employed. Univariate analysis using bar charts and histograms was done. The bivariate analysis covered an ANOVA table and scatterplot, while the Multivariate level entailed the Propensity Score Matching model. The findings showed that instructor competence in digital gadget utilization enhances online teaching, but rural residences and poor infrastructure limit engagement. Internet access remains a major hindrance, requiring government intervention for free connectivity. Practical fields face significant challenges in integrating online teaching, necessitating hefty investments in digital learning tools and simulators. Financial constraints among instructors, due to limited income-generating activities, further reduce online teaching adoption in TVET institution

Multi-packet Hybrid ARQ: Closing gap to the ergodic capacity

International audienceIn this work we consider incremental redundancy (IR) hybrid automatic repeat request (HARQ), where transmission rounds are carried out over independent block-fading channels. We propose the so-called multi-packet HARQ where the transmitter allows different packets to share the same channel block. In this way the resources (block) are optimally assigned throughout the transmission rounds. This stands in contrast with the conventional HARQ, where each transmission round occupies the entire block. We analyze superposition coding and time-sharing transmission strategies and we optimize the parameters to maximize the throughput. Besides the conventional one-bit feedback (ACK/NACK) we also consider the rich, multi-bit feedback. To solve the optimization problem we formulate it as a Markov decision process (MDP) problem where the decisions are taken using accumulated mutual information (AMI) obtained from the receiver via delayed feedback. When only one-bit feedback is used to inform the transmitter about the decoding success/failure (ACK/NACK), the Partial State Information Markov Decision Process (PSI-MDP) framework is used to obtain the optimal policies. Numerical examples obtained in a Rayleigh-fading channel indicate that, the proposed multi-packet HARQ outperforms the conventional one, by more than 5 dB for high spectral efficiencies