Improving the Routing Layer of Ad Hoc Networks Through Prediction Techniques

Cada dia és més evident el paper clau que juguen la informàtica/computació mòbil i les tecnologies sense fils a les nostres activitats diàries. Estar sempre connectat, en qualsevol moment i lloc, és actualment més una necessitat que un luxe. Els escenaris de computació ubics creats en base a aquests avenços tecnològics, permeten a les persones proporcionar i consumir informació compartida. En aquests escenaris, les xarxes que donen suport a aquestes comunicacions són típicament sense fils i ad hoc. Les característiques dinàmiques i canviants de les xarxes ad hoc, fan que el treball realitzat per la capa d'enrutament tingui un gran impacte en el rendiment d'aquestes xarxes. És molt important que la capa d'enrutament reaccioni ràpidament als canvis que es produeixen, i fins i tot s'avanci als que es produiran en un futur proper, mitjançant l'aplicació de tècniques de predicció. Aquesta tesi investiga si les tècniques de predicció poden millorar la capa d'enrutament de les xarxes ad hoc. Com a primer pas en aquesta direcció, explorem la potencialitat d'una estratègia de Predictor-Basat-en-Història (HBP) per predir la Informació de Control Topològic (TCI) generada pels protocols d'enrutament. Demostrem que hi ha una gran oportunitat per predir TCI, i aquesta predicció pot centrar-se en un petit subconjunt de missatges. En base a les nostres troballes, implementem el predictor OLSR-HBP i l'avaluem respecte al protocol Optimized Link State Routing (OLSR). OLSR-HBP aconsegueix disminucions importants de TCI (sobrecàrrega de senyalització), sense afectar el funcionament de la xarxa i necessita una quantitat de recursos petita i assequible. Finalment, en referència a l'impacte de la predicció en les dades d'enrutament tant de la informació de Qualitat d'Enllaç como de Ruta (o Extrem-a-Extrem), demostrem que l'Anàlisi de Sèries Temporals és un enfocament prometedor per predir amb precisió, tant la Qualitat d'Enllaç como la Qualitat d'Extrem a Extrem en Xarxes Comunitàries.Cada día es más evidente el papel clave que juegan la informática/computación móvil y las tecnologías inalámbricas en nuestras actividades diarias. Estar siempre conectado, en cualquier momento y lugar, es actualmente más una necesidad que un lujo. Los escenarios de computación ubicuos creados en base a estos avances tecnológicos, permiten a las personas proporcionar y consumir información compartida. En estos escenarios, las redes que dan soporte a estas comunicaciones son típicamente inalámbricas y ad hoc. Las características dinámicas y cambiantes de las redes ad hoc, hacen que el trabajo realizado por la capa de enrutamiento tenga un gran impacto en el rendimiento de estas redes. Es muy importante que la capa de enrutamiento reaccione rápidamente a los cambios que se producen, e incluso se adelante a los que sucederán en un futuro cercano, mediante la aplicación de técnicas de predicción. Esta tesis investiga si las técnicas de predicción pueden mejorar la capa de enrutamiento de las redes ad hoc. Como primer paso en esta dirección, exploramos la potencialidad de una estrategia de Predictor-Basado-en-Historia (HBP) para predecir la Información de Control Topológico (TCI) generada por los protocolos de enrutamiento. Demostramos que hay una gran oportunidad para predecir TCI, y esta predicción puede centrarse en un pequeño subconjunto de mensajes. En base a nuestros hallazgos, implementamos el predictor OLSR-HBP y lo evaluamos con respecto al protocolo Optimized Link State Routing (OLSR). OLSR-HBP consigue disminuciones importantes de TCI (sobrecarga de señalización), sin afectar al funcionamiento de la red, y necesita una cantidad de recursos pequeña y asequible. Finalmente, en referencia al impacto de la predicción en los datos de enrutamiento tanto de la información de Calidad de Enlace como de Ruta (o Extremo-a-Extremo), demostramos que el Análisis de Series Temporales es un enfoque prometedor para predecir con precisión, tanto la Calidad de Enlace como la Calidad de Extremo a Extremo en Redes Comunitarias.Everyday becomes more evident the key role that mobile computing and wireless technologies play in our daily activities. Being always connected, anytime, and anywhere is today more a necessity than a luxury. The ubiquitous computing scenarios created based on these technology advances allow people to provide and consume shared information. In these scenarios, the supporting communication networks are typically wireless and ad hoc. The dynamic and changing characteristics of the ad hoc networks, makes the work done by the routing layer to have a high impact on the performance of these networks. It is very important for the routing layer to quickly react to changes that happen, and even be advanced to what will happen in the near future, by applying prediction techniques. This thesis investigates whether prediction techniques can improve the routing layer of ad hoc networks. As a first step in this direction, in this thesis we explored the potentiality of a History-Based Predictor (HBP) strategy to predict the Topology Control Information (TCI) generated by routing protocols. We demonstrated that there is a high opportunity for predicting theTCI, and this prediction can be just focused on a small subset of messages. Based on our findings we implemented the OLSR-HBP predictor and evaluated it with regard to the Optimized Link State Routing (OLSR) protocol. OLSR History-Based Predictor (OLSR-HBP) achieved important decreases of TCI (signaling overhead), without disturbing the network operation, and requiring a small and affordable amount of resources. Finally, regarding the impact of Prediction on the routing data for both Link and Path (or End-to-End) Quality information, we demonstrated that Time-series analysis is a promising approach to accurately predict both Link and End-to-End Quality in Community Networks

Predicting topology propagation messages in mobile ad hoc networks: The value of history

This research was funded by the Spanish Government under contracts TIN2016-77836-C2-1-R,TIN2016-77836-C2-2-R, and DPI2016-77415-R, and by the Generalitat de Catalunya as Consolidated ResearchGroups 2017-SGR-688 and 2017-SGR-990.The mobile ad hoc communication in highly dynamic scenarios, like urban evacuations or search-and-rescue processes, plays a key role in coordinating the activities performed by the participants. Particularly, counting on message routing enhances the communication capability among these actors. Given the high dynamism of these networks and their low bandwidth, having mechanisms to predict the network topology offers several potential advantages; e.g., to reduce the number of topology propagation messages delivered through the network, the consumption of resources in the nodes and the amount of redundant retransmissions. Most strategies reported in the literature to perform these predictions are limited to support high mobility, consume a large amount of resources or require training. In order to contribute towards addressing that challenge, this paper presents a history-based predictor (HBP), which is a prediction strategy based on the assumption that some topological changes in these networks have happened before in the past, therefore, the predictor can take advantage of these patterns following a simple and low-cost approach. The article extends a previous proposal of the authors and evaluates its impact in highly mobile scenarios through the implementation of a real predictor for the optimized link state routing (OLSR) protocol. The use of this predictor, named OLSR-HBP, shows a reduction of 40–55% of topology propagation messages compared to the regular OLSR protocol. Moreover, the use of this predictor has a low cost in terms of CPU and memory consumption, and it can also be used with other routing protocols.Peer ReviewedPostprint (published version

Active Q-switched distributed feedback erbium-doped fiber lasers

This letter presents a distributed feedback fiber laser that operates in an actively controlled Q-switched regime. The laser is based on a Bragg grating made in an erbium-doped fiber. The grating has a defect induced by a magnetostrictive transducer that configures the distributed feedback laser structure. The phase shift generated by the defect can be dynamically modified by an electric current, permitting active Q-switching of the laser. The laser generates pulses of 75 ns duration and the repetition rate can be continuously adjusted from 0 to 10 kHz

Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating

We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be continuously varied from 1 Hz to 125 kHz

Predicting topology propagation messages in mobile ad hoc networks: The value of history

The mobile ad hoc communication in highly dynamic scenarios, like urban evacuations or search-and-rescue processes, plays a key role in coordinating the activities performed by the participants. Particularly, counting on message routing enhances the communication capability among these actors. Given the high dynamism of these networks and their low bandwidth, having mechanisms to predict the network topology offers several potential advantages; e.g., to reduce the number of topology propagation messages delivered through the network, the consumption of resources in the nodes and the amount of redundant retransmissions. Most strategies reported in the literature to perform these predictions are limited to support high mobility, consume a large amount of resources or require training. In order to contribute towards addressing that challenge, this paper presents a history-based predictor (HBP), which is a prediction strategy based on the assumption that some topological changes in these networks have happened before in the past, therefore, the predictor can take advantage of these patterns following a simple and low-cost approach. The article extends a previous proposal of the authors and evaluates its impact in highly mobile scenarios through the implementation of a real predictor for the optimized link state routing (OLSR) protocol. The use of this predictor, named OLSR-HBP, shows a reduction of 40–55% of topology propagation messages compared to the regular OLSR protocol. Moreover, the use of this predictor has a low cost in terms of CPU and memory consumption, and it can also be used with other routing protocols.Fil: Millán, Pere. Universitat Rovira I Virgili; EspañaFil: Aliagas, Carles. Universitat Rovira I Virgili; EspañaFil: Molina, Carlos. Universitat Rovira I Virgili; EspañaFil: Meseguer, Roc. Universidad Politécnica de Catalunya; EspañaFil: Ochoa, Sergio F.. Universidad de Chile; ChileFil: Santos, Rodrigo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias e Ingeniería de la Computación. Universidad Nacional del Sur. Departamento de Ciencias e Ingeniería de la Computación. Instituto de Ciencias e Ingeniería de la Computación; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentin

Minimulticomputador de bajo coste

En la mayoría de los estudios de Grado en Ingeniería Informática hay asignaturas que abordan el tema de la supercomputación. Uno de sus objetivos es adquirir competencias en programación paralela. Para realizar ejercicios y prácticas se suelen usar estándares como OpenMP, MPI y CUDA. Para programar con dichos estándares se usan sistemas de elevado precio, lo que hace que el presupuesto disponible limite el número de procesadores. Por lo tanto, el acceso a un supercomputador con cientos de procesadores (que supone centenares de miles de euros) no parece estar justificado para realizar prácticas con los estudiantes. Sin embargo, y siguiendo la tendencia de usar muchos procesadores pero poco potentes basados en ARM, se puede construir un minimulticomputador de bajo coste por un precio equivalente a un servidor de memoria compartida. Este trabajo presenta un recurso docente basado en placas de HardKernel, que integran 64 placas Odroid y que mediante Gigabit-Ethernet permiten montar un servidor de programación MPI con 256 procesadores. Si bien se trata de un recurso de bajas prestaciones, es interesante el hecho de tener acceso a centenares de procesadores para poder hacer estudios de escalabilidad, manteniendo un buen compromiso entre prestaciones, precio y consumo.In most of Computer Science Degrees, there are subjects that address the topic of supercomputing. One of the objectives of these subjects is to acquire competences in parallel programming. To carry out exercises and practices, standards such as OpenMP, MPI and CUDA are often used. Unfortunately, the most suitable systems to deal with those standards are very expensive and most of the times the available budget limits the number of processors. Owning a supercomputer with hundreds of processors (that means hundreds of thousands of euros) does not seem to be justified in a teaching environment. However, assuming the trend of dealing with many low-power processors (based on ARM architectures), a low-cost minimulticomputer can be built for a price equivalent to a shared memory server. In this work, we present a teaching resource based on HardKernel boards, with 64 Odroid boards connected through Gigabit-Ethernet, to build a MPI server with 256 processors. Although it is a resource with a relatively low performance, the aim is to have access to hundreds of processors to be able to carry out scalability analysis and, above all, maintaining a good trade-off between performance, price and energy consumption.Este trabajo ha contado con la financiación del Gobierno de España bajo los contratos TIN2016-77836-C2-1-R, TIN2016-77836-C2-2-R, TIN2016-75344-R y DPI2016-77415-R, y también de la Generalitat de Catalunya como Grupos de Investigación Consolidados 2017-SGR-688 y 2017-SGR-990

A low-cost and do-it-yourself device for pumping monitoring in deep aquifers

Water crises due to climate change, high population growth and increasing demands from industry and agriculture claim for increasing efficiency and universalizing water resources management strategies and techniques. Water monitoring helps providing necessary evidences for making sound decisions about managing water resources both now and in the future. In this work, a low cost and “do it yourself” communication device is proposed to record water production and energy consumption of electric pumpings from deep boreholes/wells, and to predict the impact of the ongoing and previous pumpings in the evolution of the water level in the aquifer. The proposal incorporates an edge-computing approach for the simulation of the aquifer response in real-time. Computation of results of interest is performed at the sensor, minimizing communication requirements and ensuring almost immediate results. An approximated solution to physically based modeling of aquifer response is computed thanks to the a priori expression of the water level time evolution in a reduced basis. The accuracy is enough to detect deviations from expected behaviour. The energy consumption of the device is very much reduced with respect to that of a full modelling, which can be computed off-line for calibrating reduced model parameters and perform detailed analyses. The device is tested in a real scenario, in a mountain subbasin of the Ebro river in Spain, obtaining a good trade-off between performance, price, and energy consumption.This research has been partly supported by EU under grant agreement N. 825184 and funded by the Government of Spain under contracts PID2019-106774RB-C21, PID2019-106774RB-C22, and PID2020-113172RB-I00 and by the Government of Catalonia as Consolidated Research Groups 2017-SGR-688 and 2017-SGR-990, and Pre-consolidated Research Group 2017-SGR-1496. The APC was funded by the Open program from Universitat Rovira i Virgili.Peer ReviewedPostprint (published version

Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings

This paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.36.002104. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment. © 2011 Optical Society of America.This work was financially supported by the European Commission under the FP7 EURO-FOS Network of Excellence (ICT-2007-2-224402), the Ministerio de Educación y Ciencia SINADEC project (TEC2008-06333), and the Natural Sciences and Engineering Research Council of Canada (NSERC). The work of G. E. Villanueva was supported by the Ministerio de Educación y Ciencia Formación de Profesorado Universitario programs. The work of P. Pérez-Millán was supported by the Juan de la Cierva program, JCI-2009-05805.Villanueva Ibáñez, GE.; Jakubinek, M.; Simard, B.; Oton Nieto, CJ.; Matres Abril, J.; Shao, L.; Pérez Millán, P.... (2011). Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings. Optics Letters. 36(11):2104-2106. https://doi.org/10.1364/OL.36.002104S210421063611Sakakibara, Y., Rozhin, A. G., Kataura, H., Achiba, Y., & Tokumoto, M. (2005). Carbon Nanotube-Poly(vinylalcohol) Nanocomposite Film Devices: Applications for Femtosecond Fiber Laser Mode Lockers and Optical Amplifier Noise Suppressors. Japanese Journal of Applied Physics, 44(4A), 1621-1625. doi:10.1143/jjap.44.1621Chow, K. K., Yamashita, S., & Song, Y. W. (2009). A widely tunable wavelength converter based on nonlinear polarization rotation in a carbon-nanotube-deposited D-shaped fiber. Optics Express, 17(9), 7664. doi:10.1364/oe.17.007664Set, S. Y., Yaguchi, H., Tanaka, Y., & Jablonski, M. (2004). Ultrafast Fiber Pulsed Lasers Incorporating Carbon Nanotubes. IEEE Journal of Selected Topics in Quantum Electronics, 10(1), 137-146. doi:10.1109/jstqe.2003.822912Chow, K. K., Tsuji, M., & Yamashita, S. (2010). Single-walled carbon-nanotube-deposited tapered fiber for four-wave mixing based wavelength conversion. Applied Physics Letters, 96(6), 061104. doi:10.1063/1.3304789Chow, K. K., & Yamashita, S. (2009). Four-wave mixing in a single-walled carbon-nanotube-deposited D-shaped fiber and its application in tunable wavelength conversion. Optics Express, 17(18), 15608. doi:10.1364/oe.17.015608Choi, S. Y., Rotermund, F., Jung, H., Oh, K., & Yeom, D.-I. (2009). Femtosecond mode-locked fiber laser employing a hollow optical fiber filled with carbon nanotube dispersion as saturable absorber. Optics Express, 17(24), 21788. doi:10.1364/oe.17.021788Chan, C.-F., Chen, C., Jafari, A., Laronche, A., Thomson, D. J., & Albert, J. (2007). Optical fiber refractometer using narrowband cladding-mode resonance shifts. Applied Optics, 46(7), 1142. doi:10.1364/ao.46.001142Kingston, C. T., Jakubek, Z. J., Dénommée, S., & Simard, B. (2004). Efficient laser synthesis of single-walled carbon nanotubes through laser heating of the condensing vaporization plume. Carbon, 42(8-9), 1657-1664. doi:10.1016/j.carbon.2004.02.020Jakubinek, M. B., Johnson, M. B., White, M. A., Guan, J., & Simard, B. (2010). Novel Method to Produce Single-Walled Carbon Nanotube Films and Their Thermal and Electrical Properties. Journal of Nanoscience and Nanotechnology, 10(12), 8151-8157. doi:10.1166/jnn.2010.3014Vallaitis, T., Koos, C., Bonk, R., Freude, W., Laemmlin, M., Meuer, C., … Leuthold, J. (2008). Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier. Optics Express, 16(1), 170. doi:10.1364/oe.16.00017

Emergency department direct discharge compared to short-stay unit admission for selected patients with acute heart failure: analysis of short-term outcomes

Insuficiència cardíaca; Serveis d'urgències mèdiques; MortalitatHeart failure; Emergency service, hospital; MortalityInsuficiencia cardíaca; Servicio hospitalario de urgencias; MortalidadShort stay unit (SSU) is an alternative to conventional hospitalization in patients with acute heart failure (AHF), but the prognosis is not known compared to direct discharge from the emergency department (ED). To determine whether direct discharge from the ED of patients diagnosed with AHF is associated with early adverse outcomes versus hospitalization in SSU. Endpoints, defined as 30-day all-cause mortality or post-discharge adverse events, were evaluated in patients diagnosed with AHF in 17 Spanish EDs with an SSU, and compared by ED discharge vs. SSU hospitalization. Endpoint risk was adjusted for baseline and AHF episode characteristics and in patients matched by propensity score (PS) for SSU hospitalization. Overall, 2358 patients were discharged home and 2003 were hospitalized in SSUs. Discharged patients were younger, more frequently men, with fewer comorbidities, had better baseline status, less infection, rapid atrial fibrillation and hypertensive emergency as the AHF trigger, and had a lower severity of AHF episode. While their 30-day mortality rate was lower than in patients hospitalized in SSU (4.4% vs. 8.1%, p < 0.001), 30-day post-discharge adverse events were similar (27.2% vs. 28.4%, p = 0.599). After adjustment, there were no differences in the 30-day risk of mortality of discharged patients (adjusted HR 0.846, 95% CI 0.637-1.107) or adverse events (1.035, 0.914-1.173). In 337 pairs of PS-matched patients, there were no differences in mortality or risk of adverse event between patients directly discharged or admitted to an SSU (0.753, 0.409-1.397; and 0.858, 0.645-1.142; respectively). Direct ED discharge of patients diagnosed with AHF provides similar outcomes compared to patients with similar characteristics and hospitalized in a SSU.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The author(s) disclosed receipt of the following fnancial support for the research, authorship, and/or publication of this article: This study was partially supported by grants from the Instituto de Salud Carlos III supported with funds from the Spanish Ministry of Health and FEDER (PI15/01019, PI18/00393) and Fundació La Marató de TV3 (2015/2510). The Emergencies: Processes and Pathologies research group of the IDIBAPS receives fnancial support from the Catalonian government for consolidated groups of investigation (GRC 2009/1385 and 2014/0313)

Minimulticomputador de bajo coste

En la mayoría de los estudios de Grado en Ingeniería Informática hay asignaturas que abordan el tema de la supercomputación. Uno de sus objetivos es adquirir competencias en programación paralela. Para realizar ejercicios y prácticas se suelen usar estándares como OpenMP, MPI y CUDA. Para programar con dichos estándares se usan sistemas de elevado precio, lo que hace que el presupuesto disponible limite el número de procesadores. Por lo tanto, el acceso a un supercomputador con cientos de procesadores (que supone centenares de miles de euros) no parece estar justificado para realizar prácticas con los estudiantes. Sin embargo, y siguiendo la tendencia de usar muchos procesadores pero poco potentes basados en ARM, se puede construir un minimulticomputador de bajo coste por un precio equivalente a un servidor de memoria compartida. Este trabajo presenta un recurso docente basado en placas de HardKernel, que integran 64 placas Odroid y que mediante Gigabit-Ethernet permiten montar un servidor de programación MPI con 256 procesadores. Si bien se trata de un recurso de bajas prestaciones, es interesante el hecho de tener acceso a centenares de procesadores para poder hacer estudios de escalabilidad, manteniendo un buen compromiso entre prestaciones, precio y consumo.Este trabajo ha contado con la financiación del Gobierno de España bajo los contratos TIN2016-77836-C2-1-R, TIN2016-77836-C2-2-R, TIN2016-75344-R y DPI2016-77415-R, y también de la Generalitat de Catalunya como Grupos de Investigación Consolidados 2017-SGR-688 y 2017-SGR-990Peer ReviewedPostprint (published version