Design and Test of a High QoS Radio Network for CBTC Systems in Subway Tunnels

Communications Based Train Control Systems require high quality radio data communications for train signaling and control. Actually most of these systems use 2.4GHz band with proprietary radio transceivers and leaky feeder as distribution system. All them demand a high QoS radio network to improve the efficiency of railway networks. We present narrow band, broad band and data correlated measurements taken in Madrid underground with a transmission system at 2.4 GHz in a test network of 2 km length in subway tunnels. The architecture proposed has a strong overlap in between cells to improve reliability and QoS. The radio planning of the network is carefully described and modeled with narrow band and broadband measurements and statistics. The result is a network with 99.7% of packets transmitted correctly and average propagation delay of 20ms. These results fulfill the specifications QoS of CBTC systems

Assessment and Real Time Implementation of Wireless Communications Systems and Applications in Transportation Systems

Programa Oficial de Doutoramento en Tecnoloxías da Información e das Comunicacións en Redes Móbiles. 5029V01[Resumo] Os sistemas de comunicación sen fíos de cuarta e quinta xeración (4G e 5G) utilizan unha capa física (PHY) baseada en modulacións multiportadora para a transmisión de datos cun gran ancho de banda. Este tipo de modulacións proporcionan unha alta eficiencia espectral á vez que permiten corrixir de forma sinxela os efectos da canle radio. Estes sistemas utilizan OFDMA como mecanismo para a repartición dos recursos radio dispoñibles entre os diferentes usuarios. Este repartimento realízase asignando un subconxunto de subportadoras a cada usuario nun instante de tempo determinado. Isto aporta unha gran flexibilidade ó sistema que lle permite adaptarse tanto ós requisitos de calidade de servizo dos usuarios como ó estado da canle radio. A capa de acceso ó medio (MAC) destes sistemas encárgase de configurar os diversos parámetros proporcionados pola capa física OFDMA, ademais de xestionar os diversos fluxos de información de cada usuario, transformando os paquetes de capas superiores en paquetes da capa física. Neste traballo estúdase o deseño e implementación das capas MAC e PHY de sistemas de comunicación 4G ademais da súa aplicabilidade en sistemas de transporte ferroviarios. Por unha parte, abórdase o deseño e implementación en tempo real do estándar WiMAX. Estúdanse os mecanismos necesarios para establecer comunicacións bidireccionais entre unha estación base e múltiples dispositivos móbiles. Ademais, estúdase como realizar esta implementación nunha arquitectura hardware baseada en DSPs e FPGAs, na que se implementan as capas MAC e PHY. Dado que esta arquitectura ten uns recursos computacionais limitados, tamén se estudan as necesidades de cada módulo do sistema para poder garantir o funcionamento en tempo real do sistema completo. Por outra parte, tamén se estuda a aplicabilidade dos sistemas 4G a sistemas de transporte públicos. Os sistemas de comunicacións e sinalización son unha parte vital para os sistemas de transporte ferroviario e metro. As comunicacións sen fíos utilizadas por estes sistemas deben ser robustas e proporcionar unha alta fiabilidade para permitir a supervisión, control e seguridade do tráfico ferroviario. Para levar a cabo esta avaliación de viabilidade realízanse simulacións de redes de comunicacións LTE en contornos de transporte ferroviarios, comprobando o cumprimento dos requisitos de fiabilidade e seguridade. Realízanse diferentes simulacións do sistema de comunicacións para poder ser avaliadas e seleccionar a configuración e arquitectura do sistema máis axeitada en función do escenario considerado. Tamén se efectúan simulacións de redes baseadas en Wi-Fi, dado que é a solución máis utilizada nos metros, para confrontar os resultados cos obtidos para LTE. Para que os resultados das simulacións sexan realistas débense empregar modelos de propagación radio axeitados. Nas simulacións utilízanse tanto modelos deterministas como modelos baseados nos resultados de campañas de medida realizadas nestes escenarios. Nas simulacións empréganse os diferentes fluxos de información destes escenarios para comprobar que se cumpren os requisitos de calidade de servicio (QoS). Por exemplo, os fluxos críticos para o control ferroviario, como European Train Control System (ETCS) ou Communication-Based Train Control (CBTC), necesitan unha alta fiabilidade e un retardo mínimo nas comunicacións para garantir o correcto funcionamento do sistema.[Resumen] Los sistemas de comunicación inalámbricos de cuarta y quinta generación (4G y 5G) utilizan una capa física (PHY) basada en modulaciones multiportadora para la transmisión de datos con un gran ancho de banda. Este tipo de modulaciones han demostrado tener una alta eficiencia espectral a la vez que permiten corregir de forma sencilla los efectos del canal radio. Estos sistemas utilizan OFDMA como mecanismo para el reparto de los recursos radio disponibles entre los diferentes usuarios. Este reparto se realiza asignando un subconjunto de subportadoras a cada usuario en un instante de tiempo determinado. Esto aporta una gran flexibilidad al sistema que le permite adaptarse tanto a los requisitos de calidad de servicio de los usuarios como al estado del canal radio. La capa de acceso al medio (MAC) de estos sistemas se encarga de configurar los diversos parámetros proporcionados por la capa física OFDMA, además de gestionar los diversos flujos de información de cada usuario, transformando los paquetes de capas superiores en paquetes de la capa física. En este trabajo se estudia el diseño e implementación de las capas MAC y PHY de sistemas de comunicación 4G además de su aplicabilidad en sistemas de transporte ferroviarios. Por una parte, se aborda el diseño e implementación en tiempo real del estándar WiMAX. Se estudian los mecanismos necesarios para establecer comunicaciones bidireccionales entre una estación base y múltiples dispositivos móviles. Además, se estudia cómo realizar esta implementación en una arquitectura hardware basada en DSPs y FPGAs, en la que se implementan las capas MAC y PHY. Dado que esta arquitectura tiene unos recursos computacionales limitados, también se estudian las necesidades de cada módulo del sistema para poder garantizar el funcionamiento en tiempo real del sistema completo. Por otra parte, también se estudia la aplicabilidad de los sistemas 4G a sistemas de transporte públicos. Los sistemas de comunicaciones y señalización son una parte vital para los sistemas de transporte ferroviario y metro. Las comunicaciones inalámbricas utilizadas por estos sistemas deben ser robustas y proporcionar una alta fiabilidad para permitir la supervisión, control y seguridad del tráfico ferroviario. Para llevar a cabo esta evaluación de viabilidad se realizan simulaciones de redes de comunicaciones LTE en entornos de transporte ferroviarios, comprobando si se cumplen los requisitos de fiabilidad y seguridad. Se realizan diferentes simulaciones del sistema de comunicaciones para poder ser evaluados y seleccionar la configuración y arquitectura del sistema más adecuada en función del escenario planteado. También se efectúan simulaciones de redes basadas en Wi-Fi, dado que es la solución más utilizada en los metros, para comparar los resultados con los obtenidos para LTE. Para que los resultados de las simulaciones sean realistas se deben utilizar modelos de propagación radio apropiados. En las simulaciones se utilizan tanto modelos deterministas como modelos basados en los resultados de campañas de medida realizadas en estos escenarios. En las simulaciones se utilizan los diferentes flujos de información de estos escenarios para comprobar que se cumplen sus requisitos de calidad de servicio. Por ejemplo, los flujos críticos para el control ferroviario, como European Train Control System (ETCS) o Communication-Based Train Control (CBTC), necesitan una alta fiabilidad y un retardo bajo en las comunicaciones para garantizar el correcto funcionamiento del sistema.[Abstract] The fourth and fifth generation wireless communication systems (4G and 5G) use a physical layer (PHY) based on multicarrier modulations for data transmission using high bandwidth. This type of modulations has shown to provide high spectral efficiency while allowing low complexity radio channel equalization. These systems use OFDMA as a mechanism for distributing the available radio resources among different users. This allocation is done by assigning a subset of subcarriers to each user in a given instant of time. This provides great flexibility to the system that allows it to adapt to both the quality of service requirements of users and the radio channel state. The media access layer (MAC) of these systems is in charge of configuring the multiple OFDMA PHY layer parameters, in addition to managing the data flows of each user, transforming the higher layer packets into PHY layer packets. This work studies the design and implementation of MAC and PHY layers of 4G communication systems as well as their applicability in rail transport systems. On the one hand, the design and implementation in real time of the WiMAX standard is addressed. The required mechanisms to establish bidirectional communications between a base station and several mobile devices are also evaluated. Moreover, a MAC layer and PHY layer implementation is presented, using a hardware architecture based in DSPs and FPGAs. Since this architecture has limited computational resources, the requirements of each processing block of the system are also studied in order to guarantee the real time operation of the complete system. On the other hand, the applicability of 4G systems to public transportation systems is also studied. Communications and signaling systems are a vital part of rail and metro transport systems. The wireless communications used by these systems must be robust and provide high reliability to enable the supervision, control and safety of rail traffic. To carry out this feasibility assessment, LTE communications network simulations are performed in rail transport environments to verify that reliability and safety requirements are met. Several simulations are carried out in order to evaluate the system performance and select the most appropriate system configuration in each case. Simulations of Wi-Fi based networks are also carried out, since it is the most used solution in subways, to compare the results with those obtained for LTE. To perform the simulations correctly, appropriate radio propagation models must be used. Both deterministic models and models based on the results of measurement campaigns in these scenarios are used in the simulations. The simulations use the different information flows present in the railway transportation systems to verify that its quality of service requirements are met. For example, critical flows for railway control, such as the European Train Control System (ETCS) or Communication-Based Train Control (CBTC), require high reliability and low delay communications to ensure the proper functioning of the system

A cognitive control approach to interference mitigation in communications-based train control (CBTC) co-existing with passenger information systems (PISs)

As a key component of urban rail transit systems, communications-based train control (CBTC) is an automated train control system using train-ground communications to ensure efficient operation of rail vehicles. In addition to CBTC systems, passenger information systems (PISs) are adopted in urban rail transit systems to improve quality of service (QoS) offered to customers. The interference between CBTC systems and PISs is an important factor impacting QoS of both CBTC systems and PISs. With recent advances in cognitive dynamic systems, in this paper, we take a cognitive control approach to interference mitigation considering the co-existence of CBTC systems and PISs. In our cognitive control approach, the notion of information gap is adopted to quantitatively describe effects of interference on CBTC. The wireless channel is modeled as a finite-state Markov chain with multiple state transition probability matrices, which are derived from real field measurements. Simulation results show that the proposed cognitive control approach can significantly improve performance of CBTC train-ground communications under interference from

Access point deployment optimisation in communication-based train control systems

Through the use of new communication-based train control (CBTC) systems, modern metro railways have been able to provide a more efficient, more reliable and more eco-friendly transport services. The main advantages of the CBTC systems are achieved by utilising modern communication technologies. The performance of the communications network is dependent on a well-designed access point (AP) deployment, as this determines the overall communication capability and impacts the cost. In this thesis, a systematic methodology is proposed for formulating and solving AP deployment planning (ADP) problems in two scenarios: (i) a tunnel section area; and (ii) a real-world metro system. Different mathematical models are presented for modelling the ADP problem in these two scenarios. In addition to mathematical models, an exhaustive search and a customized search algorithm, which uses a multi-objective evolutionary algorithm based on decomposition (MOEA/D), are proposed for solving the ADP optimisation problems. The methodologies are applied to the scenarios mentioned above. To evaluate the optimisation results, the optimised AP deployments are tested on a simulation platform integrating a railway network simulator and a communication network simulator. The test result shows that with the optimised AP deployments the DCS can achieve a better performance while using fewer APs

Towards the Internet of Smart Trains: A Review on Industrial IoT-Connected Railways

[Abstract] Nowadays, the railway industry is in a position where it is able to exploit the opportunities created by the IIoT (Industrial Internet of Things) and enabling communication technologies under the paradigm of Internet of Trains. This review details the evolution of communication technologies since the deployment of GSM-R, describing the main alternatives and how railway requirements, specifications and recommendations have evolved over time. The advantages of the latest generation of broadband communication systems (e.g., LTE, 5G, IEEE 802.11ad) and the emergence of Wireless Sensor Networks (WSNs) for the railway environment are also explained together with the strategic roadmap to ensure a smooth migration from GSM-R. Furthermore, this survey focuses on providing a holistic approach, identifying scenarios and architectures where railways could leverage better commercial IIoT capabilities. After reviewing the main industrial developments, short and medium-term IIoT-enabled services for smart railways are evaluated. Then, it is analyzed the latest research on predictive maintenance, smart infrastructure, advanced monitoring of assets, video surveillance systems, railway operations, Passenger and Freight Information Systems (PIS/FIS), train control systems, safety assurance, signaling systems, cyber security and energy efficiency. Overall, it can be stated that the aim of this article is to provide a detailed examination of the state-of-the-art of different technologies and services that will revolutionize the railway industry and will allow for confronting today challenges.Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; ED431C 2016-045Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; ED341D R2016/012Galicia. Consellería de Cultura, Educación e Ordenación Universitaria; ED431G/01Agencia Estatal de Investigación (España); TEC2013-47141-C4-1-RAgencia Estatal de Investigación (España); TEC2015-69648-REDCAgencia Estatal de Investigación (España); TEC2016-75067-C4-1-

Analysis of Railway Signalling Systems to Increase Line and Node Capacity

"Europe is one of the most urbanized continents on the planet: about 75% of its population lives in urban areas” (European Enviroment Agency, 2017). In this urban context, the car is still the widely used way of transport, while public transport manages to capture residual segments of the demand for mobility. However, in a structural framework of obvious concern and criticality for public transport, there is a component of the sector in strong expansion, that is, all rail transports. In addition, the incidence of rail transport is even more significant in large metropolitan systems where daily travel reaches its highest levels of expression. It is known, however, that the supply of transport services is limited by the capacity of the transport system which depends on the physical size of the infrastructure, that is, the capacity of the infrastructure, the number of vehicles, the capacity of the vehicle fleet, the operating time and the traffic regime implemented