Estudio sobre un sistema de radiocomunicaciones ferroviarias de acuerdo al paradigma 4G

No hay duda de que el ferrocarril es uno de los símbolos del avance tecnológico y social de la humanidad, y su imparable avance desde el primer tercio del Siglo XIX así lo atestigua. No obstante, a lo largo de gran parte de su historia se ha mostrado algo renuente a abrazar ciertas tecnologías, lo que le ha causado ser tachado de conservador. Sin embargo, en los últimos años, coincidiendo con el auge masivo de los trenes de alta velocidad, los metropolitanos y los tranvías, muchas tecnologías han ido penetrando en el mundo del ferrocarril. La que hoy nos ocupa es una de las que mayor valor añadido le ha proporcionado (y que probablemente le proporcionará también en el futuro): las comunicaciones móviles. Actualmente el uso de este tipo de tecnologías en el entorno ferroviario puede calificarse como de inicial o, por seguir la nomenclatura de las comunicaciones móviles públicas, de segunda generación. El GSM-R en las líneas de alta velocidad es un caso (aunque de éxito al fin y al cabo) que define perfectamente el estado del arte de las comunicaciones móviles en este entorno, ya que proporcionó un gran valor añadido a costa de un gran esfuerzo de estandarización; ha supuesto un importante salto adelante en el campo de la fiabilidad de este tipo de sistemas, aunque tiene unas grandes limitaciones de capacidad y graves problemas de escalabilidad. Todo hace pensar que en 2025 el sustituto de GSM-R deberá estar en el mercado. En cualquier caso, se debería abandonar la filosofía de crear productos de nicho, que son extraordinariamente caros, y abrazar las filosofías abiertas de las redes de comunicaciones públicas. Aquí es donde LTE, la última gran estrella de esta familia de estándares, puede aportar mucho valor. La idea subyacente detrás de esta Tesis es que LTE puede ser una tecnología que aporte gran valor a las necesidades actuales (y probablemente futuras) del sector del ferrocarril, no solamente en las líneas y trenes de alta velocidad, sino en las denominadas líneas convencionales y en los metros y tranvías. Dado que es un campo aún a día de hoy que dista bastante de estar completamente estudiado, se ha explorado la problemática de la propagación electromagnética en los diferentes entornos ferroviarios, como pueden ser los túneles de metro y la influencia de las estructuras de los trenes. En este sentido, se ha medido de forma bastante exhaustiva en ambos entornos. Por otro lado, dado que los sistemas multiantena son uno de los pilares fundamentales de los modernos sistemas de comunicaciones, se ha verificado de forma experimental la viabilidad de esta tecnología a la hora de implementar un sistema de comunicaciones trentierra en un túnel. Asimismo, de resultas de estas medidas, se ha comprobado la existencia de ciertos fenómenos físicos que pueden suponer una merma en la eficiencia de este tipo de sistemas. En tercer lugar, y dado que uno de los grandes desafíos de las líneas de alta velocidad está provocado por la gran celeridad a la que se desplazan los trenes, se ha explorado la influencia de este parámetro en la eficiencia global de una red completa de comunicaciones móviles. Por supuesto, se ha hecho especial hincapié en los aspectos relacionados con la gestión de la movilidad (traspasos o handovers Por último, a modo de cierre de la Tesis, se ha tratado de identificar los futuros servicios de comunicaciones que aportarán más valor a las explotaciones ferroviarias, así como los requisitos que supondrán para las redes de comunicaciones móviles. Para los casos antes enunciados (propagación, sistemas multiantena, movilidad y desafíos futuros) se proporcionan las contribuciones ya publicadas en revistas y congresos internacionales, así como las que están enviadas para su revisión. ABSTRACT There is almost no doubt that railways are one of the symbols of the technological and social progress of humanity. However, most of the time railways have been somewhat reluctant to embrace new technologies, gaining some reputation of being conservative. But in the last years, together with the massive boom of high speed lines, subways and trams all over the world, some technologies have broken through these conservative resistance. The one which concerns us now is one of the most value-added (both today and in the future): mobile communications. The state-of-the-art of these technologies in the railway field could be called as incipient, or (following the mobile communications’ notation) ‘second generation’. GSM-R, the best example of mobile communications in railways is a success story that shows perfectly the state-of-the-art of this field: it provided a noticeable mark-up but also required a great standardization effort; it also meant a huge step forward in the reliability of these systems but it also needs to face some scalability issues and some capacity problems. It looks more than feasible that in 2025 the alternative to GSM-R should be already available. Anyway, the vision here should be forgetting about expensive niche products, and embracing open standards like public mobile communications do. The main idea behind this Thesis is that LTE could be a technology that provides a lot of added value to the necessities of the railways of today and the future. And not only to highspeed lines, but also to the so-called conventional rail, subways and tramways. Due to the fact that even today, propagation in tunnels and influence of car bodies is far from being full-studied, we measured in a very exhaustive way the EM propagation in these two environments. Also, multiantenna systems are one of the basic foundations of the modern communications systems, so we experimentally verified the feasibility of using such a system in a train-towayside in a tunnel. Moreover, from the measurements carried out we proved the existence of some physical phenomena that could imply a decrease in the performance of these multiantenna systems. In third place, we have explored the influence of high-speed in the whole performance of the network, from the mobility management point-of-view. This high-speed movement is one of the most relevant challenges for the mobile communications networks. The emphasis was placed on the mobility aspects of the radio resource management. Finally, the Thesis closure is an identification of the future communication services that could provide a bigger addition of value to railways, and also the requirements that imply to mobile communications networks. For all the previous for scenarios depicted before (propagation, multiantenna systems, mobility and challenges) we provide some contributions already published (or submitted for revision or still in progress) on publications and international conferences.

Study of OLSR protocol with Network Simulator 2 over Linux

Until a few years ago, most of the network communications were based in the wire as the physical media, but due to the advances and the maturity of the wireless communications, this is changing. Nowadays wireless communications offers fast, secure, efficient and reliable connections. Mobile communications are in expansion, clearly driven by the use of smart phones and other mobile devices, the use of laptops, etc… Besides that point, the inversion in the installation and maintenance of the physical medium is much lower than in wired communications, not only because the air has no cost, but because the installation and maintenance of the wire require a high economic cost. Besides the economic cost we find that wire is a more vulnerable medium to external threats such as noise, sabotages, etc… There are two different types of wireless networks: those which the structure is part of the network itself and those which have a lack of structure or any centralization, in a way that the devices that form part of the network can connect themselves in a dynamic and random way, handling also the routing of every control and information messages, this kind of networks is known as Ad-hoc. In the present work we will proceed to study one of the multiple wireless protocols that allows mobile communications, it is Optimized Link State Routing, from now on, OLSR, it is an pro-active routing, standard mechanism that works in a distributed in order to stablish the connections among the different nodes that belong to a wireless network. Thanks to this protocol it is possible to get all the routing tables in all the devices correctly updated every moment through the periodical transmission of control messages and on this way allow a complete connectivity among the devices that are part of the network and also, allow access to other external networks such as virtual private networks o Internet. This protocol could be perfectly used in environments such as airports, malls, etc… The update of the routing tables in all the devices is got thanks to the periodical transmission of control messages and finally it will offer connectivity among all the devices and the corresponding external networks. For the study of OLSR protocol we will have the help of the network simulator “Network Simulator 2”, a freeware network simulator programmed in C++ based in discrete events. This simulator is used mainly in educational and research environments and allows a very extensive range of protocols, both, wired networks protocols and wireless network protocols, what is going to be really useful to proceed to the simulation of different configurations of networks and protocols. In the present work we will also study different simulations with Network Simulator 2, in different scenarios with different configurations, wired networks, and Ad-hoc networks, where we will study OLSR Protocol. RESUMEN. Hasta hace pocos años, la mayoría de las comunicaciones de red estaban basadas en el cable como medio físico pero debido al avance y madurez alcanzados en el campo de las comunicaciones inalámbricas esto está cambiando. Hoy día las comunicaciones inalámbricas nos ofrecen conexiones veloces, seguras, eficientes y fiables. Las comunicaciones móviles se encuentran en su momento de máxima expansión, claramente impulsadas por el uso de teléfonos y demás dispositivos móviles, el uso de portátiles, etc… Además la inversión a realizar en la instalación y el mantenimiento del medio físico en las comunicaciones móviles es muchísimo menor que en comunicaciones por cable, ya no sólo porque el aire no tenga coste alguno, sino porque la instalación y mantenimiento del cable precisan de un elevado coste económico por norma. Además del coste económico nos encontramos con que es un medio más vulnerable a amenazas externas tales como el ruido, escuchas no autorizadas, sabotajes, etc… Existen dos tipos de redes inalámbricas: las constituidas por una infraestructura que forma parte más o menos de la misma y las que carecen de estructura o centralización alguna, de modo que los dispositivos que forman parte de ella pueden conectarse de manera dinámica y arbitraria entre ellos, encargándose además del encaminamiento de todos los mensajes de control e información, a este tipo de redes se las conoce como redes Ad-hoc. En el presente Proyecto de Fin de Carrera se procederá al estudio de uno de los múltiples protocolos inalámbricos que permiten comunicaciones móviles, se trata del protocolo inalámbrico Optimized Link State Routing, de ahora en adelante OLSR, un mecanismo estándar de enrutamiento pro-activo, que trabaja de manera distribuida para establecer las conexiones entre los nodos que formen parte de las redes inalámbricas Ad-hoc, las cuales carecen de un nodo central y de una infraestructura pre-existente. Gracias a este protocolo es posible conseguir que todos los equipos mantengan en todo momento las tablas de ruta actualizadas correctamente mediante la transmisión periódica de mensajes de control y así permitir una completa conectividad entre todos los equipos que formen parte de la red y, a su vez, también permitir el acceso a otras redes externas tales como redes privadas virtuales o Internet. Este protocolo sería usado en entornos tales como aeropuertos La actualización de las tablas de enrutamiento de todos los equipos se conseguirá mediante la transmisión periódica de mensajes de control y así finalmente se podrá permitir conectividad entre todos los equipos y con las correspondientes redes externas. Para el estudio del protocolo OLSR contaremos con el simulador de redes Network Simulator 2, un simulador de redes freeware programado en C++ basado en eventos discretos. Este simulador es usado principalmente en ambientes educativos y de investigación y permite la simulación tanto de protocolos unicast como multicast. El campo donde más se utiliza es precisamente en el de la investigación de redes móviles Ad-hoc. El simulador Network Simulator 2 no sólo implementa el protocolo OLSR, sino que éste implementa una amplia gama de protocolos, tanto de redes cableadas como de redes inalámbricas, lo cual va a sernos de gran utilidad para proceder a la simulación de distintas configuraciones de redes y protocolos. En el presente Proyecto de Fin de Carrera se estudiarán también diversas simulaciones con el simulador NS2 en diferentes escenarios con diversas configuraciones; redes cableadas, redes inalámbricas Ad-hoc, donde se estudiará el protocolo antes mencionado: OLSR. Este Proyecto de Fin de Carrera consta de cuatro apartados distintos: Primeramente se realizará el estudio completo del protocolo OLSR, se verán los beneficios y contrapartidas que ofrece este protocolo inalámbrico. También se verán los distintos tipos de mensajes existentes en este protocolo y unos pequeños ejemplos del funcionamiento del protocolo OLSR. Seguidamente se hará una pequeña introducción al simulador de redes Network Simulator 2, veremos la historia de este simulador, y también se hará referencia a la herramienta extra NAM, la cual nos permitirá visualizar el intercambio de paquetes que se produce entre los diferentes dispositivos de nuestras simulaciones de forma intuitiva y amigable. Se hará mención a la plataforma MASIMUM, encargada de facilitar en un entorno académico software y documentación a sus alumnos con el fin de facilitarles la investigación y la simulación de redes y sensores Ad-hoc. Finalmente se verán dos ejemplos, uno en el que se realizará una simulación entre dos PCs en un entorno Ethernet y otro ejemplo en el que se realizará una simulación inalámbrica entre cinco dispositivos móviles mediante el protocolo a estudiar, OLSR.

Implementação do sistema GSM-R na rede ferroviária nacional : projeto-piloto

O GSM -R-Global System for Mobile Communications Railway começou o seu desenvolvimento em 1992 pela UIC (União Internacional dos Caminhos de ferro) com a criação do EIRENE (European lntegrated Railway Radio Enhanced Network) e constitui a componente de telecomunicações do sistema ERTMS - European Railway Trajjic Management System em conjunto com o ETCS - European Train Contrai System e o ATP­ Automatic Train Protection. O GSM-R baseia-se assim no GSM público com algumas adaptações e um conjunto de funcionalidades adicionais necessárias à sua utilização especificamente ferroviária. Em termos de rádio as principais diferenças relativamente à norma GSM, residem no facto de o sistema GSM-R suportar velocidades até aos 500 km/h, suportando handovers e seleção/re-seleção de células mais rápidos do que na norma do GSM original. Por outro lado, ao nível funcional e aplicacional, novas funções específicas da ferrovia foram consideradas, tais como por exemplo o controlo automático dos comboios e as chamadas de emergência. O GSM-R encontra-se já instalado em diversos países europeus. Em Portugal encontra-se instalado na Linha de Cascais e entre a Estação do Oriente e a Ponte 25 Abril, atualmente ainda numa fase experimental. O Estágio decorreu na empresa Refer Telecom - Serviços de Telecomunicações S.A. (RT) que é uma empresa do grupo REFER E.P.E. Mais concretamente, o estágio integrou-se nas atividades da Direção de Comunicações Móveis, pertencente à Direção de Coordenação de Sistemas Ferroviários da REFER Telecom. Neste Relatório de Estágio pretende-se fazer uma apresentação das atividades com participação e acompanhamento do estagiário, integrada numa descrição de todas as fases em que se dividiu a implementação do Projeto-piloto GSM-R em Portugal, desde a elaboração dos elementos técnicos para o concurso até à sua implementação no terreno. Pretende-se ainda enquadrar os principais aspetos relacionados com a utilização de algumas ferramentas de suporte à operação e à manutenção ao sistema GSM-R. Neste contexto são apresentados os conhecimentos teóricos e práticos adquiridos com a realização do estágio, incluindo o estudo necessário para compreender a arquitetura complexa do sistema GSM-R e tecnologias associadas, sobre a sua implementação no terreno e a operação e manutenção dos equipamentos, assim como sobre as áreas da contratação e da gestão de projetos. O Projeto-piloto GSM-R é um dos mais importantes projetos de telecomunicações ferroviárias instalado em Portugal nos últimos anos, pois visa projetar a ferrovia nacional para o futuro, com melhores comunicações em termos de qualidade, segurança, fiabilidade, interoperabilidade e sustentabilidade. Trata-se assim de uma importante experiência profissional e pessoal, muito enriquecedora, e que no seu conjunto abre novas perspectivas para o futuro.

The performance of the maximum ratio combining method in correlated Rician-fading channels for antenna-diversity signal combining

The performance of the maximum ratio combining method for the combining of antenna-diversity signals in correlated Rician-fading channels is rigorously studied. The distribution function of the normalized signal-to-noise ratio (SNR) is expanded in terms of a power series and calculated numerically. This power series can easily take into account the signal correlations and antenna gains and can be applied to any number of receiving antennas. An application of the method to dual-antenna diversity systems produces useful distribution curves for the normalized SNR which can be used to find the diversity gain. It is revealed that signal correlation in Rician-fading channels helps to increase the diversity gain rather than to decrease it as in the Rayleigh fading channels. It is also shown that with a relative strong direct signal component, the diversity gain can be much higher than that without a direct signal component.

Advanced handover procedure for cellular communication systems

Third Generation cellular communication systems are expected to support mixed cell architecture in which picocells, microcells and macrocells are used to achieve full coverage and increase the spectral capacity. Supporting higher numbers of mobile terminals and the use of smaller cells will result in an increase in the number of handovers, and consequently an increase in the time delays required to perform these handovers. Higher time delays will generate call interruptions and forced terminations, particularly for time sensitive applications like real-time multimedia and data services. Currently in the Global System for Mobile communications (GSM), the handover procedure is initiated and performed by the fixed part of the Public Land Mobile Network (PLMN). The mobile terminal is only capable of detecting candidate base stations suitable for the handover; it is the role of the network to interrogate a candidate base station for a free channel. Handover signalling is exchanged via the fixed network and the time delay required to perform the handover is greatly affected by the levels of teletraffic handled by the network. In this thesis, a new handover strategy is developed to reduce the total time delay for handovers in a microcellular system. The handover signalling is diverted from the fixed network to the air interface to prevent extra delays due to teletraffic congestion, and to allow the mobile terminal to exchange signalling directly with the candidate base station. The new strategy utilises Packet Reservation Multiple Access (PRMA) technique as a mechanism to transfer the control of the handover procedure from the fixed network to the mobile terminal. Simulation results are presented to show a dramatic reduction in the handover delay as compared to those obtained using fixed channel allocation and dynamic channel allocation schemes.

The factors affecting attitudes toward HSDPA service and intention to use:a cross-cultural comparison between Asia and Europe

HSDPA (High-Speed Downlink Packet Access) is a 3.5-generation asynchronous mobile communications service based on the third generation of W-CDMA. In Korea, it is mainly provided in through videophone service. Because of the diffusion of more powerful and diversified services, along with steep advances in mobile communications technology, consumers demand a wide range of choices. However, because of the variety of technologies, which tend to overflow the market regardless of consumer preferences, consumers feel increasingly confused. Therefore, we should not adopt strategies that focus only on developing new technology on the assumption that new technologies are next-generation projects. Instead, we should understand the process by which consumers accept new forms of technology and devise schemes to lower market entry barriers through strategies that enable developers to understand and provide what consumers really want.

Why Cyber Security is Hard

Abstract There has been a great deal of interest in the area of cyber security in recent years. But what is cyber security exactly? And should society really care about it? We look at some of the challenges of being an academic working in the area of cyber security and explain why cyber security is, to put it rather simply, hard! Speaker Biography Keith Martin Prof. Keith Martin is Professor of Information Security at Royal Holloway, University of London. He received his BSc (Hons) in Mathematics from the University of Glasgow in 1988 and a PhD from Royal Holloway in 1991. Between 1992 and 1996 he held a Research Fellowship at the University of Adelaide, investigating mathematical modelling of cryptographic key distribution problems. In 1996 he joined the COSIC research group of the Katholieke Universiteit Leuven in Belgium, working on security for third generation mobile communications. Keith rejoined Royal Holloway in January 2000, became a Professor in Information Security in 2007 and was Director of the Information Security Group between 2010 and 2015. Keith's research interests range across cyber security, but with a focus on cryptographic applications. He is the author of 'Everyday Cryptography' published by Oxford University Press.

Gestão de desempenho numa rede celular

A realização desta dissertação tem como principal objetivo a análise de indicadores chave de desempenho numa rede celular de terceira geração - Universal Mobile Telecommunication System (UMTS), bem como a aplicação de técnicas matemáticas de previsão como apoio ao respetivo planeamento e otimização. Para o efeito, foi inicialmente efetuado um estudo sobre a evolução das comunicações de uma forma generalista, até às redes de nova geração, abordando individualmente, as de voz, as de dados e as comunicações móveis, assim como, uma breve descrição das organizações envolvidas nestas mudanças. No seguimento do estudo inicial, dando enfoque à tecnologia UMTS, foram expostas as suas características, a sua estrutura e arquitetura. Foram ainda elaboradas, duas comparações, com base em diferentes parâmetros, uma com a tecnologia da geração anterior e outra, com a de última geração. Com base nos conhecimentos adquiridos em diferentes pesquisas, foram estudados, os indicadores chave de desempenho (KPIs), as técnicas de planeamento e otimização, apresentando propostas de prevenção e soluções para problemas existentes na rede.

Consumer appraisals of mobile marketing communications

This paper reports on a study that investigates the emotions elicited from appraising SMS-based mobile marketing (m-marketing) communications under three marketing conditions: product consistency, incentives and permission giving. Results from the experimental design show that appraising m-marketing communications elicits both single emotions and mixed emotions; that is, a mixture of positive and negative emotions in the same response. Additionally, the results show that the influence of specific marketing conditions may increase or reduce the intensity of the emotions elicited. This study contributes to marketing practice by examining consumer appraisals of m-marketing communications under different combinations of marketing conditions. The results provide insights into which emotions are likely to be elicited as a result, and how a specific marketing condition might influence their levels of intensity. The study contributes to marketing theory also through combining appraisal theory with Richins (1997) consumption emotion set.

Advances in base- and mobile-station aided cooperative wireless communications : An overview

In recent years, there has been an upsurge of research interest in cooperative wireless communications in both academia and industry. This article presents a simple overview of the pivotal topics in both mobile station (MS)- and base station (BS)- assisted cooperation in the context of cellular radio systems. Owing to the ever-increasing amount of literature in this particular field, this article is by no means exhaustive, but is intended to serve as a roadmap by assembling a representative sample of recent results and to stimulate further research. The emphasis is initially on relay-base cooperation, relying on network coding, followed by the design of cross-layer cooperative protocols conceived for MS cooperation and the concept of coalition network element (CNE)-assisted BS cooperation. Then, a range of complexity and backhaul traffic reduction techniques that have been proposed for BS cooperation are reviewed. A more detailed discussion is provided in the context of MS cooperation concerning the pros and cons of dispensing with high-complexity, power-hungry channel estimation. Finally, generalized design guidelines, conceived for cooperative wireless communications, are presented.

Energy-Aware Rate and Description Allocation Optimized Video Streaming for Mobile D2D Communications

The proliferation problem of video streaming applications and mobile devices has prompted wireless network operators to put more efforts into improving quality of experience (QoE) while saving resources that are needed for high transmission rate and large size of video streaming. To deal with this problem, we propose an energy-aware rate and description allocation optimization method for video streaming in cellular network assisted device-to-device (D2D) communications. In particular, we allocate the optimal bit rate to each layer of video segments and packetize the segments into multiple descriptions with embedded forward error correction (FEC) for realtime streaming without retransmission. Simultaneously, the optimal number of descriptions is allocated to each D2D helper for transmission. The two allocation processes are done according to the access rate of segments, channel state information (CSI) of D2D requester, and remaining energy of helpers, to gain the highest optimization performance. Simulation results demonstrate that our proposed method (named OPT) significantly enhances the performance of video streaming in terms of high QoE and energy saving.

Mobile Wearable Communications

This special issue provides the latest research and development on wireless mobile wearable communications. According to a report by Juniper Research, the market value of connected wearable devices is expected to reach $1.5 billion by 2014, and the shipment of wearable devices may reach 70 million by 2017. Good examples of wearable devices are the prominent Google Glass and Microsoft HoloLens. As wearable technology is rapidly penetrating our daily life, mobile wearable communication is becoming a new communication paradigm. Mobile wearable device communications create new challenges compared to ordinary sensor networks and short-range communication. In mobile wearable communications, devices communicate with each other in a peer-to-peer fashion or client-server fashion and also communicate with aggregation points (e.g., smartphones, tablets, and gateway nodes). Wearable devices are expected to integrate multiple radio technologies for various applications' needs with small power consumption and low transmission delays. These devices can hence collect, interpret, transmit, and exchange data among supporting components, other wearable devices, and the Internet. Such data are not limited to people's personal biomedical information but also include human-centric social and contextual data. The success of mobile wearable technology depends on communication and networking architectures that support efficient and secure end-to-end information flows. A key design consideration of future wearable devices is the ability to ubiquitously connect to smartphones or the Internet with very low energy consumption. Radio propagation and, accordingly, channel models are also different from those in other existing wireless technologies. A huge number of connected wearable devices require novel big data processing algorithms, efficient storage solutions, cloud-assisted infrastructures, and spectrum-efficient communications technologies.

Adaptive transceiver - antenna techniques for mobile broadband communications at millimetre - wave frequencies

This paper is concerned with the implementation of a Mobile Broadband System, currently under research in Europe. We present a low-complexity, adaptive transceiver/antenna approach where simple, linear, phased arrays are adjusted under a transmission quality measurement provided by a decision-feedback equalizer. Several simulation results are presented and discussed.