917 resultados para wireless communication technology


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The wide adaptation of Internet Protocol (IP) as de facto protocol for most communication networks has established a need for developing IP capable data link layer protocol solutions for Machine to machine (M2M) and Internet of Things (IoT) networks. However, the wireless networks used for M2M and IoT applications usually lack the resources commonly associated with modern wireless communication networks. The existing IP capable data link layer solutions for wireless IoT networks provide the necessary overhead minimising and frame optimising features, but are often built to be compatible only with IPv6 and specific radio platforms. The objective of this thesis is to design IPv4 compatible data link layer for Netcontrol Oy's narrow band half-duplex packet data radio system. Based on extensive literature research, system modelling and solution concept testing, this thesis proposes the usage of tunslip protocol as the basis for the system data link layer protocol development. In addition to the functionality of tunslip, this thesis discusses the additional network, routing, compression, security and collision avoidance changes required to be made to the radio platform in order for it to be IP compatible while still being able to maintain the point-to-multipoint and multi-hop network characteristics. The data link layer design consists of the radio application, dynamic Maximum Transmission Unit (MTU) optimisation daemon and the tunslip interface. The proposed design uses tunslip for creating an IP capable data link protocol interface. The radio application receives data from tunslip and compresses the packets and uses the IP addressing information for radio network addressing and routing before forwarding the message to radio network. The dynamic MTU size optimisation daemon controls the tunslip interface maximum MTU size according to the link quality assessment calculated from the radio network diagnostic data received from the radio application. For determining the usability of tunslip as the basis for data link layer protocol, testing of the tunslip interface is conducted with both IEEE 802.15.4 radios and packet data radios. The test cases measure the radio network usability for User Datagram Protocol (UDP) based applications without applying any header or content compression. The test results for the packet data radios reveal that the typical success rate for packet reception through a single-hop link is above 99% with a round-trip-delay of 0.315s for 63B packets.

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The communication in vehicular ad hoc networks (VANETs) is commonly divided in two scenarios, namely vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I). Aiming at establishing secure communication against eavesdroppers, recent works have proposed the exchange of secret keys based on the variation in received signal strength (RSS). However, the performance of such scheme depends on the channel variation rate, being more appropriate for scenarios where the channel varies rapidly, as is usually the case with V2V communication. In the communication V2I, the channel commonly undergoes slow fading. In this work we propose the use of multiple antennas in order to artificially generate a fast fading channel so that the extraction of secret keys out of the RSS becomes feasible in a V2I scenario. Numerical analysis shows that the proposed model can outperform, in terms of secret bit extraction rate, a frequency hopping-based method proposed in the literature.

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Tutkimuksessa selvitetään turkulaisten peruskoulun päättöluokkalaisten urapohdintaeroja ja sitä, miten oppilaiden arviot opettajien ja oppilaanohjaajien toteuttamasta ohjauksesta ovat yhteydessä heidän urapohdintaansa. Tutkimuksen kohdejoukkona ovat ensi sijassa yleisopetusta antavien suomenkielisten peruskoulujen yhdeksäsluokkalaiset. Tutkimus on poikkileikkaustutkimus, jossa tarkastellaan oppilaiden kokemuksia ohjauksen saatavuudesta ja hyödyllisyydestä sekä urapohdinnasta peruskoulun päättyessä. Tutkimusaineisto koottiin yhteishaun jälkeen huhti–toukokuussa 2014. Vuoden 2004 perusopetuksen opetussuunnitelman perusteista johdettujen väittämien avulla selitetään urapohdinta-mittarin sisältämien muuttujien vaihtelua. Taustamuuttujina käytetään oppilaiden koti- ja koulutaustaa. Urapohdinta-mittari on johdettu CIP-teoriasta (Cognitive Information Processing) ja muokattu CTI-mittarista (Career Thoughts Inventory). Tutkimusaineisto (N = 887) on koottu Webropol-kyselyn avulla. Oppilaiden urapohdintaa mitattiin neljän summamuuttujien avulla. Mittariston 48 väittämästä muodostettiin urapohdinta-summamuuttuja. Tämän lisäksi urapohdinnan osa-alueita arvioitiin sitoutuminen-, epävarmuus- ja konflikti-summamuuttujan avulla. Sitoutuminen-summamuuttuja mittasi sitä, miten vaikeaksi oppilas koki yhteen ura- ja jatkokoulutusvalintaan sitoutumisen. Epävarmuus-summamuuttuja mittasi päätöksenteon epävarmuutta ja konflikti-summamuuttuja vaikeutta tasapainoilla omien ajatusten ja toisaalta merkittäviksi koettujen läheisten ajatusten välillä. Kaikkien opettajien ohjaustyön näkökulmasta parhaiten hyvää urapohdintatulosta, jatkokoulutukseen sitoutumista ja päätöksentekovarmuutta ennustivat oppilaan hyvät kokemukset yhteistoiminnasta, hänen myönteinen suhtautumisensa koulunkäyntiin ja opintosuoritukset. Myös itseohjautuvuus oli tilastollisesti merkitsevässä yhteydessä urapohdintaan. Itseohjautuvuus-summamuuttuja mittasi sitä, oliko oppilas kokenut, että ohjaukselle asetetut tavoitteet saavutettiin. Opettajien tulisi kiinnittää ohjauksessaan huomiota hiljaisiin ja vähän huomiota vaativiin oppilaisiin ja tukea kaikkien oppilaiden toimintakykyä. Opinto-ohjaajan taas tulisi panostaa oppilaan itsetuntemuksen kehittämiseen ja valmiuteen toimia suunnitelmallisesti. Toisen asteen nivelvaiheohjauksen painopiste tulisi siirtää päättöluokkaa varhaisemmaksi. Tutkimustulos ei tue ajatusta, että tehostettu oppilaanohjaus kohdennettaisiin opintomenestyksen mukaan, koska heikkoja urapohtijoita oli kaikissa keskiarvosanaluokissa. Opinto-ohjaajien tulisi panostaa tieto- ja viestintätekniikan hyödyntämiseen ja tehostaa koko koulun työelämäyhteistyötä.

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Nos últimos anos têm surgido vários debates e estudos sobre a importância do conhecimento. As organizações consideram a Gestão do Conhecimento (GC) uma vantagem competitiva, capaz de gerar riqueza e poder. Para tal necessitam de desenvolver mecanismos e de ter pessoas com capacidade de criar, compartilhar e disseminar conhecimentos na organização. As Tecnologias de Informação e os Sistemas de Informação são uma ferramenta de grande impacto na GC, pois assumem um papel importante no sucesso e na renovação dos conhecimentos. A partir do Modelo de GC desenvolvido por Nonaka e Takeuchi, o Modelo Metavisão, e as técnicas de Business lntelligence, elaborou-se um Modelo de Gestão do conhecimento para a Unidade de Saúde. Com este modelo pretende-se obter beneficies, que passam pelo desenvolvimento de mecanismos de comunicação interna, formação e melhorias no processo de tomada de decisão. ABSTRACT; During the last years, debates and studies have arisen in relation to the importance of knowledge. The organizations consider Knowledge Management a competitive advantage, capable of generating wealth and power. Therefore, new mechanisms have to be developed in the organizations and employ people with capacity to create, share and disseminate knowledge. The information and Communication Technology is an important tool and has a great impact on Knowledge Management because it assumes an important role in the success and the renovation of knowledge. The Model of Knowledge Management developed by Nonaka and Takeuchi, the "Metavision" Model and the techniques of Business intelligence were the starting point to elaborate a Model of Knowledge Management for a Health Unit. With this model we aim to obtain benefits, such as development of mechanisms of internal communication, training plans and improvement during the process of decision making.

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In this research work, a new routing protocol for Opportunistic Networks is presented. The proposed protocol is called PSONET (PSO for Opportunistic Networks) since the proposal uses a hybrid system composed of a Particle Swarm Optimization algorithm (PSO). The main motivation for using the PSO is to take advantage of its search based on individuals and their learning adaptation. The PSONET uses the Particle Swarm Optimization technique to drive the network traffic through of a good subset of forwarders messages. The PSONET analyzes network communication conditions, detecting whether each node has sparse or dense connections and thus make better decisions about routing messages. The PSONET protocol is compared with the Epidemic and PROPHET protocols in three different scenarios of mobility: a mobility model based in activities, which simulates the everyday life of people in their work activities, leisure and rest; a mobility model based on a community of people, which simulates a group of people in their communities, which eventually will contact other people who may or may not be part of your community, to exchange information; and a random mobility pattern, which simulates a scenario divided into communities where people choose a destination at random, and based on the restriction map, move to this destination using the shortest path. The simulation results, obtained through The ONE simulator, show that in scenarios where the mobility model based on a community of people and also where the mobility model is random, the PSONET protocol achieves a higher messages delivery rate and a lower replication messages compared with the Epidemic and PROPHET protocols.

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The evolution of wireless communication systems leads to Dynamic Spectrum Allocation for Cognitive Radio, which requires reliable spectrum sensing techniques. Among the spectrum sensing methods proposed in the literature, those that exploit cyclostationary characteristics of radio signals are particularly suitable for communication environments with low signal-to-noise ratios, or with non-stationary noise. However, such methods have high computational complexity that directly raises the power consumption of devices which often have very stringent low-power requirements. We propose a strategy for cyclostationary spectrum sensing with reduced energy consumption. This strategy is based on the principle that p processors working at slower frequencies consume less power than a single processor for the same execution time. We devise a strict relation between the energy savings and common parallel system metrics. The results of simulations show that our strategy promises very significant savings in actual devices.

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Se trata de un estudio descriptivo de corte transversal entre estudiantes de la Facultad de Ciencias Médicas de la Universidad de Cuenca1, para determinar la magnitud del uso excesivo de Tecnologías de Información y Comunicación (TICs), su variación en función de la edad, sexo, estado civil y la carrera; así como su asociación con síntomas depresivos y de ansiedad. En el cuestionario previamente validado que fue aplicado a muestra aleatoria por conglomerados de 333 estudiantes, se integraron preguntas de información demográfica, test de uso excesivo de TICs y de síntomas depresivos y de ansiedad. El concepto de Riesgo Relativo y su Intervalo de Confianza al 95% fue utilizado para el análisis estadístico. Los resultados nos revelan que la edad promedio de la muestra de la población fue de 22 años, 37,2% con uso excesivo de TICs, el 18,3% presentan síntomas depresivos y 39,8% de ansiedad. Entre las variables asociadas de manera significativa con el uso excesivo de TICs están: la edad menor de 19 años (RR 2,04; IC 95% 1,31-3,20), el género masculino (RR 1,36; IC 95% 1,03-1,80) y la carrera de Tecnología Médica (RR 1,83; IC 95% 1,28-2,63). El uso excesivo de las TICs no está asociado con el estado civil. Sin embargo, el análisis estadístico nos muestra la existencia de una correlación positiva entre el uso excesivo de las TICs y la frecuencia de estudiantes con síntomas depresivos (RR 1,88; IC 95% 1,45-2,44) y de ansiedad (RR 2,61; IC 95% 1,64-4,15).

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Secret communication over public channels is one of the central pillars of a modern information society. Using quantum key distribution this is achieved without relying on the hardness of mathematical problems, which might be compromised by improved algorithms or by future quantum computers. State-of-the-art quantum key distribution requires composable security against coherent attacks for a finite number of distributed quantum states as well as robustness against implementation side channels. Here we present an implementation of continuous-variable quantum key distribution satisfying these requirements. Our implementation is based on the distribution of continuous-variable Einstein–Podolsky–Rosen entangled light. It is one-sided device independent, which means the security of the generated key is independent of any memoryfree attacks on the remote detector. Since continuous-variable encoding is compatible with conventional optical communication technology, our work is a step towards practical implementations of quantum key distribution with state-of-the-art security based solely on telecom components.

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A lo largo de la historia, el desarrollo de la agricultura tardó siglos en concretarse, en expandirse y en darse a conocer en la mayoría de las culturas. Durante los últimos 200 años, parte de la humanidad ha sido dominada por la actividad industrial. Mientras el resto del mundo se esfuerza por participar en la RevoluciónIndustrial, algunas naciones atraviesan por una etapa que transforma todo de un modo extraordinariamente acelerado. Es lo que se conoce como “sociedad de la información”. No cabe ninguna duda, de que la sociedad está entrando en una nueva era, en que cada aspecto de la vida de las personas se caracteriza por las aplicaciones de las Tecnologías de la Información y de la Comunicación (TIC). Se presentan, en este nuevo medio ambiente, algunos cambios que deben plantearse en la formación de los profesionales de la información.

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El avance en las tecnologías de la comunicación e información han rediseñado los escenarios del ser humano y el modo de funcionar el mundo. Los procesos son más sencillos, inmediatos y globales, pero ameritan de conocimiento, de destrezas y de tecnologías.Unas décadas atrás, cuando Vannaver Bush ideó el ME MEX, era difícil de conceptuar, ese acceso casi ilimitado entre dos puntos militares internacionales. Más tarde, Jorge Luis Borges soñó la Biblioteca Global, a la cual se ingresa a través de puertas hexagonales y en la cual fluye el saber universal. Todos estos acontecimientos, que son realidades hoy, serían cuentos de duendes y hasta herejías para los monjes que custodiaban las bibliotecas en la Edad Media. Cómo imaginar el acceso inmediato a colecciones antiguas y modernas de otras bibliotecas y de otros países desde un solo ingreso?.

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Part 4: Transition Towards Product-Service Systems

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There is clear evidence that in typically developing children reasoning and sense-making are essential in all mathematical learning and understanding processes. In children with autism spectrum disorders (ASD), however, these become much more significant, considering their importance to successful independent living. This paper presents a preliminary proposal of a digital environment, specifically targeted to promote the development of mathematical reasoning in students with ASD. Given the diversity of ASD, the prototyping of this environment requires the study of dynamic adaptation processes and the development of activities adjusted to each user’s profile. We present the results obtained during the first phase of this ongoing research, describing a conceptual model of the proposed digital environment. Guidelines for future research are also discussed.

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Home Automation holds the potential of realizing cost savings for end users while reducing the carbon footprint of domestic energy consumption. Yet, adoption is still very low. High cost of vendor-supplied home automation systems is a major prohibiting factor. Open source systems such as FHEM, Domoticz, OpenHAB etc. are a cheaper alternative and can drive the adoption of home automation. Moreover, they have the advantage of not being limited to a single vendor or communication technology which gives end users flexibility in the choice of devices to include in their installation. However, interaction with devices having diverse communication technologies can be inconvenient for users thus limiting the utility they derive from it. For application developers, creating applications which interact with the several technologies in the home automation systems is not a consistent process. Hence, there is the need for a common description mechanism that makes interaction smooth for end users and which enables application developers to make home automation applications in a consistent and uniform way. This thesis proposes such a description mechanism within the context of an open source home automation system – FHEM, together with a system concept for its application. A mobile application was developed as a proof of concept of the proposed description mechanism and the results of the implementation are reflected upon.

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The energy consumption by ICT (Information and Communication Technology) equipment is rapidly increasing which causes a significant economic and environmental problem. At present, the network infrastructure is becoming a large portion of the energy footprint in ICT. Thus the concept of energy efficient or green networking has been introduced. Now one of the main concerns of network industry is to minimize energy consumption of network infrastructure because of the potential economic benefits, ethical responsibility, and its environmental impact. In this paper, the energy management strategies to reduce the energy consumed by network switches in LAN (Local Area Network) have been developed. According to the lifecycle assessment of network switches, during usage phase, the highest amount of energy consumed. The study considers bandwidth, link load and traffic matrixes as input parameters which have the highest contribution in energy footprint of network switches during usage phase and energy consumption as output. Then with the objective of reducing energy usage of network infrastructure, the feasibility of putting Ethernet switches hibernate or sleep mode was investigated. After that, the network topology was reorganized using clustering method based on the spectral approach for putting network switches to hibernate or switched off mode considering the time and communications among them. Experimental results show the interest of this approach in terms of energy consumption