Propagation mechanism modelling in the near region of circular tunnels

Artículo sobre comunicaciones ferroviarias. Abstract: Along with the increase in operating frequencies in advanced radio communication systems utilised inside tunnels, the location of the break point is further and further away from the transmitter. This means that the near region lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. To begin with, this study analyses the propagation loss resulting from the free-space mechanism and the multi-mode waveguide mechanism in the near region of circular tunnels, respectively. Then, by conjunctive employing the propagation theory and the three-dimensional solid geometry, a general analytical model of the dividing point between two propagation mechanisms is presented for the first time. Moreover, the model is validated by a wide range of measurement campaigns in different tunnels at different frequencies. Finally, discussions on the simplified formulae of the dividing point in some application situations are made. The results in this study can be helpful to grasp the essence of the propagation mechanism inside tunnels

Propagation Mechanism modeling in the Near-Region of Arbitrary Cross-Sectional Tunnels.

Along with the increase of the use of working frequencies in advanced radio communication systems, the near-region inside tunnels lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. This paper analytically models the propagation mechanisms and their dividing point in the near-region of arbitrary cross-sectional tunnels for the first time. To begin with, the propagation losses owing to the free space mechanism and the multimode waveguide mechanism are modeled, respectively. Then, by conjunctively employing the propagation theory and the three-dimensional solid geometry, the paper presents a general model for the dividing point between two propagation mechanisms. It is worthy to mention that this model can be applied in arbitrary cross-sectional tunnels. Furthermore, the general dividing point model is specified in rectangular, circular, and arched tunnels, respectively. Five groups of measurements are used to justify the model in different tunnels at different frequencies. Finally, in order to facilitate the use of the model, simplified analytical solutions for the dividing point in five specific application situations are derived. The results in this paper could help deepen the insight into the propagation mechanisms in tunnels

Propagation Characteristics of International Space Station Wireless Local Area Network

This paper describes the application of the Uniform Geometrical Theory of Diffraction (UTD) for Space Station Wireless Local Area Networks (WLANs) indoor propagation characteristics analysis. The verification results indicate good correlation between UTD computed and measured signal strength. It is observed that the propagation characteristics are quite different in the Space Station modules as compared with those in the typical indoor WLANs environment, such as an office building. The existing indoor propagation models are not readily applicable to the Space Station module environment. The Space Station modules can be regarded as oversized imperfect waveguides. Two distinct propagation regions separated by a breakpoint exist. The propagation exhibits the guided wave characteristics. The propagation loss in the Space Station, thus, is much smaller than that in the typical office building. The path loss model developed in this paper is applicable for Space Station WLAN RF coverage and link performance analysis

UHF propagation channel characterization for tunnel microcellular and personal communications.

by Yue Ping Zhang.Publication date from spine.Thesis (Ph.D.)--Chinese University of Hong Kong, 1995.Includes bibliographical references (leaves 194-200).DEDICATIONACKNOWLEDGMENTSChapterChapter 1. --- Introduction --- p.1Chapter 1.1 --- Brief Description of Tunnels --- p.1Chapter 1.2 --- Review of Tunnel Imperfect Waveguide Models --- p.2Chapter 1.3 --- Review of Tunnel Geometrical Optical Model --- p.4Chapter 1.4 --- Review of Tunnel Propagation Experimental Results --- p.6Chapter 1.5 --- Review of Existing Tunnel UHF Radio Communication Systems --- p.13Chapter 1.6 --- Statement of Problems to be Studied --- p.15Chapter 1.7 --- Organization --- p.15Chapter 2 --- Propagation in Empty Tunnels --- p.18Chapter 2.1 --- Introduction --- p.18Chapter 2.2 --- Propagation in Empty Tunnels --- p.18Chapter 2.2.1 --- The Imperfect Empty Straight Rectangular Waveguide Model --- p.19Chapter 2.2.2 --- The Hertz Vectors for Empty Straight Tunnels --- p.20Chapter 2.2.3 --- The Propagation Modal Equations for Empty Straight Tunnels --- p.23Chapter 2.2.4 --- The Propagation Characteristics of Empty Straight Tunnels --- p.26Chapter 2.2.5 --- Propagation Numerical Results in Empty Straight Tunnels --- p.30Chapter 2.3 --- Propagation in Empty Curved Tunnels --- p.36Chapter 2.3.1 --- The Imperfect Empty Curved Rectangular Waveguide Model --- p.37Chapter 2.3.2 --- The Hertz Vectors for Empty Curved Tunnels --- p.39Chapter 2.3.3 --- The Propagation Modal Equations for Empty Curved Tunnels --- p.41Chapter 2.3.4 --- The Propagation Characteristics of Empty Curved Tunnels --- p.43Chapter 2.2.5 --- Propagation Numerical Results in Empty Curved Tunnels --- p.47Chapter 2.4 --- Summary --- p.50Chapter 3 --- Propagation in Occupied Tunnels --- p.53Chapter 3.1 --- Introduction --- p.53Chapter 3.2 --- Propagation in Road Tunnels --- p.53Chapter 3.2.1 --- The Imperfect Partially Filled Rectangular Waveguide Model --- p.54Chapter 3.2.2 --- The Scalar Potentials for Road tunnels --- p.56Chapter 3.2.3 --- The Propagation Modal Equations for Road Tunnels --- p.59Chapter 3.2.4 --- Propagation Numerical Results in Road Tunnels --- p.61Chapter 3.3 --- Propagation in Railway Tunnels --- p.64Chapter 3.3.1 --- The Imperfect Periodically Loaded Rectangular Waveguide Model --- p.65Chapter 3.3.2 --- The Surface Impedance Approximation --- p.66Chapter 3.3.2.1 --- The Surface Impedance of a Semi-infinite Lossy Dielectric Medium --- p.66Chapter 3.3.2.2 --- The Surface Impedance of a Thin Lossy Dielectric Slab --- p.67Chapter 3.3.2.3 --- The Surface Impedance of a Three-layered Half Space --- p.69Chapter 3.3.2.4 --- The Surface Impedance of the Sidewall of a Train in a Tunnel --- p.70Chapter 3.3.3 --- The Hertz Vectors for Railway Tunnels --- p.71Chapter 3.3.4 --- The Propagation Modal Equations for Railway Tunnels --- p.73Chapter 3.3.5 --- The Propagation Characteristics of Railway Tunnels --- p.76Chapter 3.3.6 --- Propagation Numerical Results in Railway Tunnels --- p.78Chapter 3.4 --- Propagation in Mine Tunnels --- p.84Chapter 3.4.1 --- The Imperfect periodically Loaded Rectangular Waveguide Model --- p.85Chapter 3.4.2 --- The Hertz Vectors for Mine Tunnels --- p.86Chapter 3.4.3 --- The Propagation modal Equations for Mine Tunnels --- p.88Chapter 3.4.4 --- The Propagation Characteristics of Mine Tunnels --- p.95Chapter 3.4.5 --- Propagation Numerical Results in Mine Tunnels --- p.96Chapter 3.5 --- Summary --- p.97Chapter 4 --- Statistical and Deterministic Models of Tunnel UHF Propagation --- p.100Chapter 4.1 --- Introduction --- p.100Chapter 4.2 --- Statistical Model of Tunnel UHF Propagation --- p.100Chapter 4.2.1 --- Experiments --- p.101Chapter 4.2.1.1 --- Experimental Set-ups --- p.102Chapter 4.2.1.2 --- Experimental Tunnels --- p.104Chapter 4.2.1.3 --- Experimental Techniques --- p.106Chapter 4.2.2 --- Statistical Parameters --- p.109Chapter 4.2.2.1 --- Parameters to Characterize Narrow Band Radio Propagation Channels --- p.109Chapter 4.2.2.2 --- Parameters to Characterize Wide Band Radio Propagation Channels --- p.111Chapter 4.2.3 --- Propagation Statistical Results and Discussion --- p.112Chapter 4.2.3.1 --- Tunnel Narrow Band Radio Propagation Characteristics --- p.112Chapter 4.2.3.1.1 --- Power Distance Law --- p.114Chapter 4.2.3.1.2 --- The Slow Fading Statistics --- p.120Chapter 4.2.3.1.3 --- The Fast Fading Statistics --- p.122Chapter 4.2.3.2 --- Tunnel Wide Band Radio Propagation Characteristics --- p.125Chapter 4.2.3.2.1 --- RMS Delay Spread --- p.126Chapter 4.2.3.2.2 --- RMS Delay Spread Statistics --- p.130Chapter 4.3 --- Deterministic Model of Tunnel UHF Propagation --- p.132Chapter 4.3.1 --- The Tunnel Geometrical Optical Propagation Model --- p.134Chapter 4.3.2 --- The Tunnel Impedance Uniform Diffracted Propagation Model --- p.141Chapter 4.3.2.1 --- Determination of Diffraction Points --- p.146Chapter 4.3.2.2 --- Diffraction Coefficients for Impedance Wedges --- p.147Chapter 4.3.3 --- Comparison with Measurements --- p.151Chapter 4.3.3.1 --- Narrow Band Comparison of Simulated and Measured Results --- p.151Chapter 4.3.3.1.1 --- Narrow Band Propagation in Empty Straight Tunnels --- p.151Chapter 4.3.3.1.2 --- Narrow Band Propagation in Curved or Obstructed Tunnels --- p.154Chapter 4.3.3.2 --- Wide Band Comparison of Simulated and Measured Results --- p.158Chapter 4.3.3.2.1 --- Wide Band Propagation in Empty Straight Tunnels --- p.159Chapter 4.3.3.2.2 --- Wide Band Propagation in an Obstructed Tunnel --- p.163Chapter 4.4 --- Summary --- p.165Chapter 5 --- Propagation in Tunnel and Open Air Transition Region --- p.170Chapter 5.1 --- Introduction --- p.170Chapter 5.2 --- Radiation of Radio Waves from a Rectangular Tunnel into Open Air --- p.171Chapter 5.2.1 --- Radiation Formulation Using Equivalent Current Source Concept --- p.171Chapter 5.2.2 --- Radiation Numerical Results --- p.175Chapter 5.3 --- Propagation Characteristics of UHF Radio Waves in Cuttings --- p.177Chapter 5.3.1 --- The Attenuation Constant due to the Absorption --- p.178Chapter 5.3.2 --- The Attenuation Constant due to the Roughness of the Sidewalls --- p.182Chapter 5.3.3 --- The Attenuation Constant due to the tilts of the Sidewalls --- p.183Chapter 5.3.4 --- Propagation Numerical Results in Cuttings --- p.184Chapter 5.4 --- Summary --- p.187Chapter 6 --- Conclusion and Recommendation for Future Work --- p.189APPENDIX --- p.193The Approximate Solution of a Transcendental Equation --- p.193REFERENCES --- p.19

Propagation Mechanism Analysis Before the Break Point Inside Tunnels

There is no unanimous consensus yet on the propagation mechanism before the break point inside tunnels. Some deem that the propagation mechanism follows the free space model, others argue that it should be described by the multimode waveguide model. Firstly, this paper analyzes the propagation loss in two mechanisms. Then, by conjunctively using the propagation theory and the three-dimensional solid geometry, a generic analytical model for the boundary between the free space mechanism and the multi-mode waveguide mechanism inside tunnels has been presented. Three measurement campaigns validate the model in different tunnels at different frequencies. Furthermore, the condition of the validity of the free space model used in tunnel environment has been discussed in some specific situations. Finally, through mathematical derivation, the seemingly conflicting viewpoints on the free space mechanism and the multi-mode waveguide mechanism have been unified in some specific situations by the presented generic model. The results in this paper can be helpful to gain deeper insight and better understanding of the propagation mechanism inside tunnel

Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels

An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments

An Integrative Overview of the Open Literature's Empirical Data on In-tunnel Radiowave Propagation's Power Loss

This paper offers a comprehensive and integrative overview of all empirical data available from the open literature on the in-tunnel radiowave-communication channel's power loss characteristics, as a function of the tunnel's cross-sectional shape, cross-sectional size, longitudinal shape, wall materials, presence or absence of vehicular/human traffic, and presence/absence of branches. These data were originally presented in about 50 papers in various journals, conferences, and books

Propagation, Localization and Navigation in Tunnel-like Environments

La robótica de servicio, entendida como aquella destinada al uso de uno o varios robots con fines de, por ejemplo, vigilancia, rescate e inspecciones, ha ido tomando cada vez más relevancia en los últimos años. Debido a los grandes avances en las distintas áreas de la robótica, los robots han sido capaces de ejecutar satisfactoriamente tareas que resultan peligrosas o incluso imposibles para los humanos, en diversos entornos. Entre ellos, los entornos confinados como túneles, minas y tuberías, han atraído la atención en aplicaciones relacionadas con transporte ferroviario, redes vehiculares, búsqueda y rescate, y vigilancia, tanto en el ámbito civil como militar. En muchas tareas, la utilización de varios robots resulta más provechoso que utilizar sólo uno. Para cooperar, los robots deben intercambiar información sobre el entorno y su propio estado, por lo que la comunicación entre ellos resulta crucial. Debido a la imposibilidad de utilizar redes cableadas entre robots móviles, se despliegan redes inalámbricas. Para determinar la calidad de señal entre dos robots, inicialmente se utilizaban modelos de propagación basados únicamente en la distancia entre ellos. Sin embargo, estas predicciones sólo resultan útiles en exteriores y sin la presencia de obstáculos, que sólo componen una pequeña parte de los escenarios de la robótica de servicio. Mas aún, la naturaleza altamente multi-trayecto de la propagación electromagnética en túneles hace que éstos actúen como guías de onda para cierto rango de frecuencias, extendiendo considerablemente el alcance de comunicación en comparación con entornos exteriores. Sin embargo, la señal se ve afectada con profundos desvanecimientos (llamados fadings en inglés). Esto los convierte en un reto para la robótica que considera la comunicación entre robots como fundamental. Además, la naturaleza hostil de estos entornos, así como también la falta de características visuales y estructurales, dificultan la localización en estos escenarios, cuestión que resulta fundamental para ejecutar con éxito una tarea con un robot. Los métodos de localización utilizados en interiores, como aquellos basados en SLAM visual, resultan imprecisos por la falta de características distintivas para cámaras o lásers, mientras que los sensores utilizados en exteriores, como el GPS, no funcionan dentro de túneles o tuberías. En esta tesis abordamos problemas fundamentales para la robótica con el fin de proporcionar herramientas necesarias para la exploración con robots en entornos tipo túnel, manteniendo la conectividad de la red de comunicaciones formada por varios robots y una estación base. Para ello, primeramente caracterizamos, en términos de propagación, los dos escenarios tipo túnel más comunes: un túnel de hormigón y una tubería metálica. Hacemos énfasis en el fenómeno de los fadings, ya que son el problema más importante a considerar para mantener la comunicación. Posteriormente presentamos una estrategia de navegación para desplegar un equipo de robots en un túnel, lidiando con los fadings para mantener la conectividad de la red formada por los robots. Esta estrategia ha sido validada a través de numerosos experimentos realizados en un túnel real, el túnel de Somport. Luego, abordamos el problema de la localización, proponiendo e implementando una técnica que permite estimar la posición de un robot dentro de una tubería, basada en la periodicidad de los fadings. El método es validado a través de experimentos reales en tuberías de pequeña y grandes dimensiones. Finalmente, proponemos esquemas de diversidad espacial, de forma que se facilita la navegación mientras se mejora la localización.Deploying a team of robots for search and rescue, inspection, or surveillance, has increasingly gained attention in the last years. As a result of the advances in several areas of robotics, robots have been able to successfully execute tasks that are hazardous or even impossible for humans in a variety of scenarios, such as outdoors, indoors, or even underground. Among these scenarios, tunnel-like environments (such as tunnels, mines, or pipes) have attracted attention for train applications, vehicular networks, search and rescue, and even service and surveillance missions in both military and civilian contexts. In most of the tasks, utilizing a multi-robot team yields better results than a singlerobot system, as it makes the system more robust while reducing the time required to complete tasks. In order to cooperate, robots must exchange information about their current state and the surrounding environment, making communication between them a crucial task. However, due to the mobile nature of robots used for exploration, a wired architecture is not possible nor convenient. Instead, a wireless network is often deployed. Wireless propagation in tunnel-like environments, characterized for the presence of strong fading phenomena, differs from regular indoor and outdoor scenarios, posing multiple challenges for communication-aware robotics. In addition, accurate localization is a problem in environments such as tunnels or pipes. These environments generally lack distinctive visual and/or structural features and are longer than they are wide in shape. Standard indoor localization techniques do not perform well in pipelines or tunnels given the lack of exploitable features, while outdoor techniques (GPS in particular) do not work in these scenarios. In this thesis, we address basic robotics-related problems in order to provide some tools necessary for robotics exploration in tunnel-like scenarios under connectivity constraints. In the first part, we characterize, in terms of propagation, two of the most common tunnel-like environments: a pipe and a tunnel. We emphasize the spatial-fadings phenomena, as it is one of the most relevant issues to deal with, in a communications context. Secondly, we present a navigation strategy to deploy a team of robots for tunnel exploration, in particular maintaining network connectivity in the presence of these fadings. Several experiments conducted in a tunnel allow us to validate the connectivity maintenance of the system. Next, we address the localization problem and propose a technique that uses the periodicity of the fadings to estimate the position of the robots from the base station. The method is validated in small-scale and large-scale pipes. Finally, we propose spatial diversity schemes in order to ease the navigation while improving the localization

Break point analysis and modelling in subway tunnels

The time constraints in network developments inside tunnels require a characterisation of canonical tunnels in terms of propagation path losses and developing a slope model which is usually represented as a two slope model. One of the problems arisen when the canonical model tries to predict the propagation path losses inside the tunnel is to determine the distance where the slope of the propagation path losses changes. This paper analyses two of the most common approaches to determine that distance and their behaviour in different scenarios in order to clarify the radio propagation mechanisms which define the break point distance.Postprint (published version