Propagation channel characterisation and modelling for high-speed train communication systems

High-mobility scenarios, e.g., High-Speed Train (HST) scenarios, are expected to be typical scenarios for the Fifth Generation (5G) communication systems. With the rapid development of HSTs, an increasing volume of wireless communication data is required to be transferred to train passengers. HST users demand high network capacity and reliable communication services regardless of their locations or speeds, which are beyond the capability of current HST communication systems. The features of HST channels are significantly different from those of low-mobility cellular communication systems. For a proper design and evaluation of future HST wireless communication systems, we need accurate channel models that can mimic the underlying channel characteristics, especially the non-stationarity for different HST scenarios. Inspired by the lack of such accurate HST channel models in the literature, this PhD project is devoted to the modelling and simulation of non-stationary Multiple-Input Multiple-Output (MIMO) channels for HST communication systems. In this thesis, we first give a comprehensive review of the measurement campaigns conducted in different HST scenarios and address the recent advances in HST channel models. We also highlight the key challenges of HST channel measurements and models. Then, we study the characterisation of non-stationary channels and propose a theoretical framework for deriving the statistical properties of these channels. HST wireless communication systems encounter different channel conditions due to the difference of surrounding geographical environments or scenarios. HST channel models in the literature have either considered large-scale parameters only and/or neglected the non-stationarity of HST channels and/or only consider one of the HST scenarios. Therefore, we propose a novel generic non-stationary Geometry-Based Stochastic Model (GBSM) for wideband MIMO HST channels in different HST scenarios, i.e., open space, viaduct, and cutting. The corresponding simulation model is then developed with angular parameters calculated by the Modified Method of Equal Area (MMEA). The system functions and statistical properties of the proposed channel models are thoroughly studied. The proposed generic non-stationary HST channel models are verified by measurements in terms of stationary time for the open space scenario and the Autocorrelation Function (ACF), Level Crossing Rate (LCR), and stationary distance for the viaduct and cutting scenarios. Transmission techniques which are capable of utilising Three-Dimensional (3D) spatial dimensions are significant for the development of future communication systems. Consequently, 3D MIMO channel models are critical for the development and evaluation of these techniques. Therefore, we propose a novel 3D generic non-stationary GBSM for wideband MIMO HST channels in the most common HST scenarios. The corresponding simulation model is then developed with angular parameters calculated by the Method of Equal Volume (MEV). The proposed models considers several timevarying channel parameters, such as the angular parameters, the number of taps, the Ricean K-factor, and the actual distance between the Transmitter (Tx) and Receiver (Rx). Based on the proposed generic models, we investigate the impact of the elevation angle on some of the channel statistical properties. The proposed 3D generic models are verified using relevant measurement data. Most standard channel models in the literature, like Universal Mobile Telecommunications System (UMTS), COST 2100, and IMT-2000 failed to introduce any of the HST scenarios. Even for the standard channel models which introduced a HST scenario, like IMT-Advanced (IMT-A) and WINNER II channel models, they offer stationary intervals that are noticeably longer than those in measured HST channels. This has inspired us to propose a non-stationary IMT-A channel model with time-varying parameters including the number of clusters, powers, delays of the clusters, and angular parameters. Based on the proposed non-stationary IMT-A channel model, important statistical properties, i.e., the time-variant spatial Cross-correlation Function (CCF) and time-variant ACF, are derived and analysed. Simulation results demonstrate that the stationary interval of the developed non-stationary IMT-A channel model can match that of relevant HST measurement data. In summary, the proposed theoretical and simulation models are indispensable for the design, testing, and performance evaluation of 5G high-mobility wireless communication systems in general and HST ones in specific

Wireless Channel Model and LDM-Based Transmission with Unequal Error Protection for Inside Train Communications

Although the deployment of wireless systems is widespread, there are still sectors where they are not used due to their lack of reliability in comparison to wired systems. Sectors like industry or vehicle communications consider their environment hostile because the wireless signals suffer a lot of interferences. One of such environments is the railway sector, where wiring removal will allow more flexibility for both control and monitoring systems. This thesis analyzes wireless communications inside train cars, aiming at modelling their behavior and at proposing techniques to increase the reliability of the critical signals among train systems, wich can coexist with other lower priority systems. After proposing a novel model of an inside train wireless channel, a transmission system based on Layered Division Multiplexing (LDM) has been proposed which theoretically promises higher capacities than traditional TDM or FDM. This capacity gain is used to provide higher reliability to critical data using Unequal Error Protection (UEP) while maintaining the same bit rate as equivalent TDM or FDM based systems. In the final part of the thesis, simulation results of the proposed LDM system are provided, combined with Alamouti space time coding and different coding rates. Multiantenna extensions of the proposed LDM schemes are also simulated, providing BER and throughput results. These results will be used to shed light about how to reduce BER of an inside train wireless communication system.Aunque el despliegue de los sistemas inalámbricos está muy extendido, aun hay sectores donde no se utiliza por la poca fiabilidad que proporcionan comparado con los sistemas cableados. Sectores como la industria o las comunicaciones vehiculares consideran el entorno donde trabajan como entorno hostil, debido a que las señales inalámbricas sufren muchas interferencias. Uno de estos entornos es el de las comunicaciones en ferrocarril donde la eliminación de cables permitiría mayor flexibilidad entre los sistemas de control y monitorización. En esta tesis se analiza el canal de comunicación inalámbrico dentro de los trenes, con el objetivo de modelar su comportamiento y proponer técnicas que permitan aumentar la fiabilidad de la información de tipo crítico transmitida entre los sistemas del tren, repercutiendo lo menos posible en otros sistemas de menor prioridad. Tras proponer el modelo de canal inalámbrico dentro del tren, se ha propuesto un sistema de transmisión basado en Layered Division Multiplexing (LDM) que analizándolo teóricamente promete mayores capacidades que los tradicionales TDM o FDM. Esta capacidad se utilizará para obtener mayor redundancia de los datos críticos usando Unequal Error Protection (UEP) manteniendo la misma tasa de transferencia bits que los sistemas basados en TDM/FDM. En la parte final de la tesis, se obtienen resultados de las simulaciones realizadas con el sistema LDM propuesto, combinada con codificación espacio temporal como Alamouti y diferentes ratios de codificación. También se han simulado configuraciones multiantena obteniendo resultados de BER y throughput. Estos resultados servirán para arrojar luz sobre cómo reducir el BER en las comunicaciones inalámbricas dentro de los trenes.Haririk gabeko sistemak oso hedatuak dauden arren oraindik erabiltzen ez dituen sektoreak badaude ematen duten fidagarritasuna txikia delako kableatutako sistemekin alderatuz. Industria bezalako sektoreek edo ibilgailuetako komunikazioek lan egiten duten ingurua oso zaratatsua izaten da eta seinaleek interferentzia asko jasaten dituzte. Tesi honetan tren barruko haririk gabeko komunikazio kanala aztertzen da, bere portaera aztertu eta modelatzeko asmotan. Jakintza honekin zein teknika izan daitekeen erabilgarriak aztertuko da datuen fidagarritasuna handitzeko helburuarekin, lehentasun gutxiago duten sistemetan eragin txikiena izanik. Modeloa atera ondoren proposatu den transmisio sistema Layered Division Multiplexing (LDM) izan da, non azterketa teorikoek TDM edo FDM sistemek baino kapazitate gehiago dutela frogatzen dute. Kapazitate hau sistemaren datu kritikoei erredundantzia gehiago emateko erabiliko da Unequal Error Protection (UEP) erabiliz, TDM/FDM sistemetan bidaltzen den bit tasa kopurua mantenduz. Tesiaren azken partean, proposatutako LDM sistemaren simulazio emaitzak ematen dira, Alamouti espazio denbora kodifikazioarekin konbinatuak eta kodigo ratio desberdinekin. Antena anitzezko konfigurazioak ere simulatu dira BER eta throughput emaitzak lortuz. Emaitza hauek haririk gabeko tren barruko komunikazioetan BER-a nola gutxitu daitekeen jakiten lagunduko digute

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

Experimental characterization of the radio channel for systems with large bandwidth and multiple antennas

[SPA] Cada día son necesarias comunicaciones mejores y más eficientes, con mayores anchos de banda y mayores tasas de transferencias de datos. Por un lado los sistemas de múltiples antenas, MIMO, surgieron como una técnica para optimizar el uso de la potencia y el espectro. Por otro lado, los sistemas Ultra-Wideband, UWB, han ganado recientemente el interés de la comunidad científica por su gran ancho de banda combinado con su baja potencia de transmisión. A la hora de diseñar y testear nuevos dispositivos de comunicaciones inalámbricas, es esencial poseer un conocimiento preciso del canal de propagación por el que se propagan dichas señales. Esta tesis, se basa en el modelado del canal de propagación para sistemas de gran ancho de banda y múltiples antenas desde un punto de vista experimental. Primeramente se presentan las mejoras y desarrollos realizados en el ámbito de los sistemas de medida del canal, dado que es necesario disponer de equipos adecuados y precisos para realizar adecuadas medidas del canal. Seguidamente, se analiza el canal MIMO-UWB en interiores. Se realiza un análisis en profundidad de varios parámetros, especialmente parámetros de una antena como las pérdidas de propagación, el factor de polarización cruzada o la dispersión del retardo. Finalmente, la tesis particulariza el análisis del canal en un entorno especial como es el caso de túneles. Se realiza un análisis experimental de parámetros de una antena como multi antena para luego evaluar las prestaciones que pueden brindar varias técnicas de diversidad como es en el dominio de la frecuencia, la polarización, el espacio o el tiempo.[ENG] Wireless communications have become essential in our society [Rappaport, 1996], [Parsons, 2000]. Nowadays, people need to be connected everywhere and at any time, and demand faster and enhanced communications every day. New applications requires higher data rates and, therefore, higher bandwidths. On the one hand, Multiple-Input Multiple-Output (MIMO) systems were proposed as one solution to achieve higher data rates and optimize the use of the spectrum. On the other hand, more recently, systems with an ultra large bandwidth, and particularly Ultra-Wideband (UWB) systems, have gained the interest of the scientific community. Such interest is owing to the extremely high data rates offered and its possible coexistence with existing systems due to the its low transmitted power. However, this improvement in mobile communications involves the development and testing of new wireless communications systems. Precise knowledge of the radio channel is an essential issue to design this new devices and, thus, reach such improvement in wireless communications. In general, the modeling of the radio channel can be undertaken in two main ways: Theoretically, where the channel is characterized by means of simulations and theoretical approaches. - Experimentally, where the radio channel is characterized by means of the analysis of measurements carried out in real scenarios. This thesis is mainly focused on the experimental characterization of the radio channel for systems with large bandwidth and multiple antennas (MIMO). However, characterizing experimentally the MIMO wideband channel implies the availability of adequate and accurate channel sounders.Universidad Politécnica de CartagenaUniversité des Sciences et Technologies de Lille (USTL)Programa de doctorado en Tecnologías de la Información y Comunicacione

Statistical Modeling of Ultrawideband MIMO Propagation Channel in a Warehouse Environment

This paper describes an extensive propagation channel measurement campaign in a warehouse environment for line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The measurement setup employs a vector network analyzer operating in the 2-8-GHz frequency band combined with an 8×8 virtual multiple-input multiple-output (MIMO) antenna array. We develop a comprehensive statistical propagation channel model based on high-resolution extraction of multipath components and subsequent spatiotemporal clustering analysis. The intracluster direction of departure (DoD), direction of arrival (DoA), and the time of arrival (ToA) are independent, both for the LOS and NLOS scenarios. The intracluster DoD and DoA can be approximated by the Laplace distribution, and the intracluster ToA can be approximated by an exponential mixture distribution. The intercluster analysis, however, shows a dependency between the cluster DoD, DoA, and ToA. To capture this dependency, we separately model the clusters caused by single and multiple bounce scattering along the aisles in the warehouse. The intercluster DoD distribution follows a Laplace distribution, while the cluster DoA conditioned on the DoD is approximated by a Gaussian mixture distribution. The model was validated using the capacity and delay-spread values

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin