Modeling radio wave propagation in tunnels with a vectorial parabolic equation (original) (raw)
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Radio Wave Propagation in Arched Cross Section Tunnels – Simulations and Measurements
Journal of Communications, 2009
For several years, wireless communication systems have been developed for train to infrastructure communication needs related to railway or mass transit applications. The systems should be able to operate in specific environments, such as tunnels. In this context, specific radio planning tools have to be developed to optimize system deployment. Realistic tunnels geometries are generally of rectangular cross section or arch-shaped. Furthermore, they are mostly curved. In order to calculate electromagnetic wave propagation in such tunnels, specific models have to be developed.
A Survey of Radio Propagation Modeling for Tunnels
—Radio signal propagation modeling plays an important role in designing wireless communication systems. The propagation models are used to calculate the number and position of base stations and predict the radio coverage. Different models have been developed to predict radio propagation behavior for wireless communication systems in different operating environments. In this paper we shall limit our discussion to the latest achievements in radio propagation modeling related to tunnels. The main modeling approaches used for propagation in tunnels are reviewed, namely, numerical methods for solving Maxwell equations, waveguide or modal approach, ray tracing based methods and two-slope path loss modeling. They are discussed in terms of modeling complexity and required information on the environment including tunnel geometry and electric as well as magnetic properties of walls.
Scaled Modeling and Measurement for Studying Radio Wave Propagation in Tunnels
Electronics
The subject of radio wave propagation in tunnels has gathered attention in recent years, mainly regarding the fading phenomena caused by internal reflections. Several methods have been suggested to describe the propagation inside a tunnel. This work is based on the ray tracing approach, which is useful for structures where the dimensions are orders of magnitude larger than the transmission wavelength. Using image theory, we utilized a multi-ray model to reveal non-dimensional parameters, enabling measurements in down-scaled experiments. We present the results of field experiments in a small concrete pedestrian tunnel with smooth walls for radio frequencies (RF) of 1, 2.4, and 10 GHz, as well as in a down-scaled model, for which millimeter waves (MMWs) were used, to demonstrate the roles of the frequency, polarization, tunnel dimensions, and dielectric properties on the wave propagation. The ray tracing method correlated well with the experimental results measured in the tunnel as we...
Taking a Sharp Turn: Modeling of Diffraction Coupling in Radio Propagation Inside Tunnels
IEEE Vehicular Technology Magazine, 2016
arash aziminejad, andrew W. lee, and gabriel epelbaum DecemBer 2016 | ieee vehicular technology magazine ||| 21 the model provides an accurate tool for analyzing diffraction effects of tunnel discontinuities with sharp edges on the process of radio propagation. Challenges of Radio-Based Data Communication Subsystem Design Among the key challenges that metro lines and light-rail systems operators face today are overcoming increasing traffic, ensuring passenger safety and security during their daily urban journeys, and improving travel comfort. As a modern successor of the traditional railway signaling system, a CBTC system ensures the cited challenge requirements through a systematic approach [1]. In most CBTC systems, bidirectional data between trains and trackside equipment are transferred by means of an open-standard wireless network as part of DCS functionality. For urban mass transit systems currently, the wireless local area network (WLAN) governed by the family of IEEE 802.11 standards offers the most popular, flexible, and cost-effective technology solution for the wireless segment of the DCS network, due to the available commercial off-the-shelf equipment. The essential subsystem-level requirements of the DCS network include throughput, packet loss, latency, and availability, which can have a significant impact on CBTC system-level performance. Such sensitive and stringent requirements add to the criticality burden of the DCS radiofrequency (RF) network design process in terms of quality, precision, and cost (time and money). Urban rail transit systems are constructed within a variety of environments (e.g., underground tunnels, viaducts, and open-cut areas) that require comprehensive radio network planning activity along the railroad tracks to get involved with a variety of propagation mechanisms. Therefore, a thorough understanding of radio-wave propagation phenomena in tunnels is deemed indispensable to DCS design methodology. In recent years, significant efforts have been made both theoretically and empirically to study radio propagation inside tunnel environments and its characteristics in a variety of tunnel scenarios and geometries [2]-[4]. We proposed a heuristic and flexible radio propagation model inside the tunnel environment, in which the framework of modal analysis is combined with the ray-tracing technique, and a novel approach has been adopted to tackle the scenario of a horizontal curvature in tunnel geometry [5]. Nevertheless, the role of the diffraction phenomenon at the sharp corners and edges inside a tunnel environment has not received the attention it deserves. Study of the diffraction process in a tunnel environment proves to be useful mainly because it provides a means for the reliable extension of radio coverage to non-line-of-sight areas and furnishes a capability to assess diffraction coupling loss owing to tunnel discontinuities, including four-arm cross sections, three-arm T and Y junctions, and L bends. The phenomenon of diffraction occurs when there is a partial blocking of a portion of the wavefront by some kind of object with a comparable size to that of the wavelength. This manifests itself in the apparent bending of waves from the straight path. This occurs prominently when there is a change in tunnel geometry (i.e., discontinuity), such as a box tunnel transitioning to/from a circular tunnel. Such a diffraction effect is also apparent when the environment changes from tunnel to open air or vice versa. Various classifications of diffraction loss modeling methods exist, but, from a high-level point of view, three main groups of modeling approaches can be distinguished: ■ electromagnetism that tends to provide a full-wave analysis and is usually numerically intensive (e.g., integral equation [6] or parabolic equation [7] methods) ■ physical optics that integrate illuminations delivered by rays incident on a surface over the surface to calculate the transmitted or scattered field using a high-frequency approximation (e.g., the Fresnel the role oF diFFrAction becomeS even more pronounced when non-line-oF-Site coverAge ScenArioS or coverAge through tunnel diScontinuitieS Such AS portAlS And vAriouS junctionS in A tunnel environment Are involved.
2011
Nowadays, the need for wireless communication systems is increasing in transport domain. These systems have to be operational in every type of environment and particularly tunnels for metro applications. These ones can have rectangular, circular or arch-shaped cross section. Furthermore, they can be straight or curved. This article presents a new method to model the radio wave propagation in straight tunnels with an arch-shaped cross section and in curved tunnels with a rectangular cross section. The method is based on a Ray Launching technique combining the computation of intersection with curved surfaces, an original optimization of paths, a reception sphere, an IMR technique and a last criterion of paths validity. Results obtained with our method are confronted to results of literature in a straight arch-shaped tunnel. Then, comparisons with measurements at 5.8 GHz are performed in a curved rectangular tunnel. Finally, a statistical analysis of fast fading is performed on these results.
Approximate Calculation of the Total Attenuation Rate of Propagating Wave Inside Curved Tunnel
2016
─ In this paper, a model is presented to simulate wave propagation in curved rectangular tunnels with imperfectly conducting walls. The model is based on treating the tunnel as a waveguide, which is an extension of previous proposed model by Mahmoud [3]. A new approach to calculate the total attenuation rate of the propagated wave inside tunnel is proposed. The approach is considering the effect of imperfect conductivity of the upper and lower walls of the tunnel. This approach is based on assuming that the boundaries of the tunnel section are constant impedance surfaces as the surface impedance of the wall is almost independent of the angle of the wave incidence onto the wall. A simple scenario is considered to check the accuracy of this model. This scenario is verified by comparing experimental and numerical simulation results. Good agreement between the proposed model and the experimental results is obtained. Index Terms ─ Curved waveguide, imperfect conducting walls, wave propag...
Time-Domain Electromagnetic Wave Propagation in Confined Environments
Advanced Electromagnetic Waves, 2015
Confined environments like tunnels are electrically large structures for guided wave propagation. They can have arbitrary cross sections, and the design and optimization of antenna for communication system requires the knowledge of a "full-wave" solution in nearby zones. Current models based on asymptotic approaches do not describe adequately the wave propagation under the above conditions. In addition, a complete "full-wave" analysis of the tunnel propagation performances is not feasible in terms of computer expenditure. After a survey of the most commonly used techniques for propagation in tunnels, some investigation regarding an appropriate approach to find the fields is proposed. It is based on a modal decomposition of the wave propagation that allows an optimization of the coupling with the antenna. To find the mode characteristic for arbitrary cross section, a full-wave method, namely, the transmission-line matrix (TLM), is modified to a so-called 2.5-dimensional TLM algorithm and presented in details. This approach is validated for a canonical structure. Then, it is applied to study the wave propagation in a realistic rectangular tunnel. The concept of surface impedance boundary condition (SIBC) is introduced to reduce the TLM computational domain and model the tunnel walls that can be considered as lossy dielectric. Results show that guided structures with lossy dielectric walls of arbitrary cross section can be studied with this approach.
2010
In this paper, a computational model is developed for predicting the electromagnetic wave propagation over different realistic types of environments for some realistic conditions. The model allows specification of frequency, polarization, antenna radiation pattern, antenna altitude and elevation angle. It also treats standard and non-standard refractive conditions; super-refractive, sub-refractive, and ducts. In addition, the model allows specification of the electrical characteristics of the ground (permittivity and conductivity). Furthermore, the model is used to deal with mixed path situation composed of user-defined number of sections each with a different electrical characteristic, and it treats flat and non-flat terrain configurations with residential areas and forest environment.
Channel characteristics in tunnels: FDTD simulations and measurement
Journal of Microwaves, Optoelectronics and Electromagnetic Applications, 2011
This paper presents the results of measurements and simulations of the characteristics of 900 MHz band radio propagation channels in a tunnel environment. The simulations were made using the FDTD method (with companion UPML) and measurements made use of the swept frequency technique. Another method, the metaheuristic Simulated Annealing, was implemented for estimating the values of characteristic parameters of materials. The FDTD code was reformulated for use with CUDA with the objective of decreasing program running time.