Multicast in 802.11 WLANs: An Experimental Study

While the deployment of WiFi networks continues to grow at an explosive rate, the multicast multimedia delivery service on WiFi compliant devices is still in its early stage of development. The real culprit is the IEEE 802.11 MAC protocol, and in particular, the absence of feedback mechanism when multicast is used. Recently, a leader-based mechanism has been proposed to overcome this problem. In this paper, we measure the characteristics of the legacy multicast transmission mechanism and analyze its aws. Then, we study the performance of the leader-based approach and compare its performance with the standard multicast service. The analysis is done on a large set of measurements made with our wireless testbed. Such measurements are an important complement to previous simulation studies and help in the design of the best mechanism to replace the faulty legacy multicast mechanism. Our study confirms that the leaderbased mechanism outperforms the standard open-loop multicast mechanism while keeping fairness among other traffic

Introducción a la "Literatura mundial"

En su última entrega del 2010, el Diario de Poesía publicó en sus páginas un importante ensayo de Eric Auerbach traducido al castellano por primera vez a casi seis décadas de su aparición alemana: «Filología de la Weltliteratur». Significativo por múltiples razones, el texto ha ocupado en los últimos años —como adecuadamente señala María Teresa Gramuglio en una infor- mada e inteligente presentación en la misma revista— un lugar central a partir de la renovación del debate sobre la «literatura mundial». En efecto, tal como sostiene Gramuglio, dos textos publicados cerca del año 2000 marcaron el retorno del campo de problemas abierto por Goethe cuando acuñó el concepto de Weltliteratur en la primera mitad del siglo XIX: La república mundial de las letras de Pascale Casanova, aparecido en 1999 en Francia, y el artículo «Conjeturas sobre la literatura mundial» de Franco Moretti en la New Left Review al año siguiente. En la década de 1950, cuando se publicó originalmente el texto de Auerbach, la cuestión fue planteada y discutida vivamente en distintos ámbitos académicos europeos y norteamericanos. En esa oportunidad, sobre el fondo de la dramática experiencia de las derivas del nacionalismo en la Segunda Guerra Mundial, el problema último estribó en si debía construirse un canon que contemplara lo mejor de la literatura en el planeta y, en tal caso, si una concepción tal de la literatura suponía incluir todo lo pro- ducido en cualquier tiempo y lugar. Pero este debate fue, como señalamos, tributario de la propuesta política y cultural a un mismo tiempo que elevó Goethe con el concepto de Weltliteratur en 1827. A través de ella afirmaba la necesidad de la emancipación de la literatura de los marcos nacionales, respetando sin embargo la singularidad cultural que expresaban. La evidente dimensión política de la irrupción del problema de la «literatura mundial», tanto en Goethe como en los medios académicos a mediados del siglo XX, también está presente en las propuestas de Casanova y Moretti. Frente a la expansión del discurso de la «globalización» que señalaría un progresivo avance hacia la homogeneización cultural que se despliega más o menos suavemente sobre un mundo también cada vez más homogéneo, estos autores, aun cuando no pretendiendo dar una respuesta política directa a estas formulaciones, sostienen que la idea de literatura mundial no puede pensarse sino a condición de comprender las desigualdades históricas entre centros idiomáticos y culturales de mayor poder, y una heterogénea periferia conformada por zonas más débiles. A pesar de que la fuerza económica y política de los Estados constituye un factor relevante de análisis, ambos planteos destacan la existencia de recursos específicamente culturales acumulados a lo largo del tiempo que hacen que la geografía literaria no se organice sobre las mismas líneas que dan forma a los países. La ambición heurística y la radical apuesta por una nueva aproxi- mación analítica al hecho literario, no pasaron desapercibidas para la crítica literaria y la sociología de la cultura. Todo lo contrario, pocos años después de su publicación, sobre todo luego de la edi- ción en lengua inglesa de la obra de Casanova, los debates, artí- culos y libros se multiplicaron en los medios académicos. 4 Más allá de la legitimidad de ciertas objeciones, las hipótesis genera- les de ambas propuestas no sólo continúan teniendo validez sino que resultan altamente estimulantes para repensar los modos de abordar la producción literaria, y no sólo literaria, en América Latina. En tal sentido, en esta breve introducción nos interesa presentar los aspectos esenciales de estas propuestas

Introducción a la “Literatura mundial”

El presente artículo tiene la intención de presentar los autores y las líneas más generales y productivas abiertas por la aproximación que se conoce como “literatura mundial”, y que han sobrevivido el paso de las críticas de los últimos años. De igual modo, nos interesa recuperar algunas claves teóricas para un acercamiento sociológico al fenómeno de la traducción que dialogan de manera directa con la “literatura mundial”. Con ello procuramos proveer de un primer marco teórico que, al considerar dimensiones y condicionamientos no siempre contemplados, contribuya a estimular nuevas formas de comprender a la producción literaria en América Latina.Fil: Dujovne, Miguel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Desarrollo Económico y Social; ArgentinaFil: García, Diego. Universidad Nacional de Córdoba. Facultad de Filosofía y Humanidades; Argentin

220904

This letter proposes a multi-gateway designation framework to design real-time wireless sensor networks (WSNs) improving traffic schedulability, i.e., meeting the traffic time constraints. To this end, we resort to Spectral Clustering un-supervised learning that allows defining arbitrary k disjoint clusters without knowledge of the nodes physical position. In each cluster we use a centrality metric from social sciences to designate one gateway. This novel combination is applied to a time-synchronized channel-hopping (TSCH) WSN under earliest-deadline-first (EDF) scheduling and shortest-path routing. Simulation results under varying configurations show that our framework is able to produce WSN designs that greatly reduce the worst-case network demand. In a situation with 5gateways, 99% schedulability can be achieved with 3.5 times more real-time flows than in a random benchmark.This work was co-financed by national funds through FCT/MCTES (Portuguese Foundation for Science and Technology) within the CISTER Research Unit (UIDB/04234/2020); by the Operational Programme for Competitiveness and Internationalization (COMPETE 2020) under the PT2020 Agreement, through the European Regional Development Fund (ERDF); and also by FCT and the ESF (European Social Fund) through the Regional Operational Programme (ROP) Norte 2020, under PhD grant 2020.06685.BD. The authors also thank to the CYTED AgIoT Project (520RT011), CORFO COTH2O “Consorcio de Gestion de Recursos Hídricos para la Macrozona Centro-Sur” and Proyecto Asociativo UDP “Plataformas Digitales como Modelo Organizacional”.info:eu-repo/semantics/publishedVersio

frost: an R package - prediction of minimum temperature for frost forecasting in agriculture

We present the package frost which aim is to survey prediction techniques of minimum temperature for agronomic frost prediction in viticulture and agriculture. The version 0.0.1 of the package frost introduces two empiric methods used by agronomic engineers and farmers: the 4rst one is recommended by FAO (Food and Agriculture Organization of the United Nations) [2], and the second one is used in Mendoza, Argentina. This package can be downloaded from its GitHub repository under the MIT open source license.Sociedad Argentina de Informática e Investigación Operativ

Experimental Methodology For Wireless Networks

The adoption of new protocols and network mechanisms requires an experimentation phase which is complex to deploy, and even more on wireless networks. Generally, ad-hoc tools are developed for the specific needs on a experimental scenario to capture, analize and store statistical data. Because there is no common experimental methodology within the research community, and research publications do not provide often the experimental conditions, it is almost impossible for another researcher to reproduce the same experimental scenario. Within this research report, we define a network evaluation methodology to simplify the deployment of wireless experiments and their analysis. The proposed method uses a modular approach for the different experimentation phases. We also illustrate this methodology by an example

Network Provisioning for High Speed Vehicles Moving along Predictable Routes - Part 1: Spiderman Handover

This report presents our on-going work on a new system designed to provide a continuous network connectivity to communicating devices located on-board a vehicle moving at ”high speed” with a predictable trajectory such as trains, subways or buses. The devices on-board the vehicle form a sub-network called the ”in-motion network”. This system we propose is composed of two parts. The mobile part, called Spiderman Device (SD), installed on the roof of the vehicle, and the fixed part is composed of multiples access points, called Wireless Switch Access Points (WS APs), installed along the predictable route of the vehicle. To provide a continuous connectivity, we designed a new handover algorithm that relies on a two IEEE802.11 radio hardware placed in the SD device. This dual-radio architecture allows to minimize or even hide the handover effects, achieving a seamless continuous data-link connection at high speeds, up-to 150 Km/h and possibly more. The link between the SD and the WS AP forms a Layer 2 Ethernet Bridge, supporting any Layer 3 protocol between the infrastructure network and the in-motion network. This concept has been validated by simulations and is currently tested using a real prototype in order to assess the performances and practical feasibility of the system

Generation of Realistic 802.11 Interferences in the Omnet++ INET Framework Based on Real Traffic Measurements

International audienceRealistic simulation of 802.11 traffic subject to high interference, for example in dense urban areas, is still an open issue. Many studies do not address the interference problem properly. In this paper, we present our preliminary work on a method to recreate interference traffic from real measurements. The method consists in capturing real traffic traces and generating interference patterns based on the recorded information. Furthermore, we assume that the coordinates of the sources of interference in the real scene are not known a priori. We introduce an extension to Omnet++ INET-Framework to replay the recreated interference in a transparent way into a simulation. We validate our proposed method by comparing it against the real measurements taken from the scene. Furthermore we present an evaluation of how the injected interference affects the simulated results on three arbitrary simulated scenarios

A deep learning approach to halo merger tree construction

A key ingredient for semi-analytic models of galaxy formation is the mass assembly history of haloes, encoded in a tree structure. The most commonly used method to construct halo merger histories is based on the outcomes of high-resolution, computationally intensive N-body simulations. We show that machine learning (ML) techniques, in particular Generative Adversarial Networks (GANs), are a promising new tool to tackle this problem with a modest computational cost and retaining the best features of merger trees from simulations. We train our GAN model with a limited sample of merger trees from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation suite, constructed using two halo finders-tree builder algorithms: SUBFIND-D-TREES and ROCKSTAR-ConsistentTrees. Our GAN model successfully learns to generate well-constructed merger tree structures with high temporal resolution, and to reproduce the statistical features of the sample of merger trees used for training, when considering up to three variables in the training process. These inputs, whose representations are also learned by our GAN model, are mass of the halo progenitors and the final descendant, progenitor type (main halo or satellite), and distance of a progenitor to that in the main branch. The inclusion of the latter two inputs greatly improves the final learned representation of the halo mass growth history, especially for SUBFIND-like ML trees. When comparing equally sized samples of ML merger trees with those of the EAGLE simulation, we find better agreement for SUBFIND-like ML trees. Finally, our GAN-based framework can be utilized to construct merger histories of low-and intermediate-mass haloes, the most abundant in cosmological simulations.Fil: Robles, Sandra. Universidad Autónoma de Madrid; España. Kings College London (kcl); . University of Melbourne; AustraliaFil: Gómez, Jonathan S. Universidad Católica de Chile; Chile. Universidad Autónoma de Madrid; España. Pontificia Universidad Católica de Chile; ChileFil: Ramírez Rivera, Adín. University of Oslo; NoruegaFil: Padilla, Nelson David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Dujovne, Diego. Universidad Diego Portales; Chil

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This research proposes a co-design framework for scheduling, routing and gateway designation to improve the real-time performance of low-power wireless mesh networks. We target time-synchronized channel hopping (TSCH) networks with centralized network management and a single gateway. The end goal is to exploit existing trade-offs between the three dimensions to enhance traffic schedulability at systems' design time. The framework we propose considers a global Earliest-Deadline-First (EDF) scheduler that operates in conjunction with the minimal-overlap (MO) shortest-path routing, after a centrality-driven gateway designation is concluded. Simulation results over varying settings suggest our approach can lead to optimal or near-optimal real-time network performance, with 3~times more schedulable flows than a naive real-time configuration.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDB/04234/2020); by the Operational Competitiveness Programme and Internationalization (COMPETE 2020) under the PT2020 Agreement, through the European Regional Development Fund (ERDF); by FCT and the ESF (European Social Fund) through the Regional Operational Programme (ROP) Norte 2020, under PhD grant 2020.06685.BD.N/