Radio wave propagation in curved rectangular tunnels at 5.8 GHz for metro applications, simulations and measurements (original) (raw)

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...

Analysis of path loss and delay spread at 900 MHz and 2.1 GHz while entering tunnels

IEEE Transactions on Vehicular Technology, 2001

Some propagation characteristics in tunnel environments at 900 MHz and 2.1 GHz are analyzed. Narrow-band parameters are given in terms of propagation factor and linear regression slopes. Wide-band analysis is considered by calculating delay spread factors along the communication path. A ray-launching technique has been implemented, using ray optics and the uniform theory of diffraction (UTD). The proposed theoretical model has been validated by comparing results with measurements obtained by other authors. The particular situation when mobile antenna crosses the tunnel entrance and transmitter is outside the tunnel is studied. Our simulations show that the larger the angular separation of the transmitter with respect to the tunnel longitudinal axis is, the higher values of delay spread. The more critical point appears around the tunnel entrance ("excitation zone"), where a signal power decay up to 40 dB may be detected. A similar value has been already found when turning a corner in microcellular urban environments.

Analysis of Propagation Characteristics for Various Subway Tunnel Scenarios at 28 GHz

International Journal of Antennas and Propagation, 2021

In order to meet the higher data transmission rate requirements of subway communication services, the millimeter wave (mmWave) broadband communication is considered as a potential solution in 5G technology. Based on the channel measurement data in subway tunnels, this paper uses ray-tracing (RT) simulation to predict the propagation characteristics of the 28 GHz millimeter wave frequency band in different tunnel scenarios. A large number of simulations based on ray-tracing software have been carried out for tunnel models with different bending radiuses and different slopes, and we further compared the simulation results with the real time measurement data of various subway tunnels. The large-scale and small-scale propagation characteristics of the channel, such as path loss (PL), root mean square delay spread (RMS-DS), and angle spread (AS), for different tunnel scenarios are analyzed, and it was found that the tunnel with a greater slope causes larger path loss and root mean square...

Modeling radio wave propagation in tunnels with a vectorial parabolic equation

IEEE Transactions on Antennas and Propagation, 2000

To study radio wave propagation in tunnels, we present a vectorial parabolic equation (PE) taking into account the cross-section shape, wall impedances, slowly varying curvature, and torsion of the tunnel axis. For rectangular cross section, two polarizations are decoupled and two families of adiabatic modes can be found explicitly, giving a generalization of the known results for a uniform tunnel. In the general case, a boundary value problem arises to be solved by using finite-difference/finite-element (FD/FE) techniques. Numerical examples demonstrate the computational efficiency of the proposed method.

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.

Path Loss Model for 3.5 GHz and 5.6 GHz Bands in Cascaded Tunnel Environments

Sensors

An important and typical scenario of radio propagation in a railway or subway tunnel environment is the cascaded straight and curved tunnel. In this paper, we propose a joint path loss model for cascaded tunnels at 3.5 GHz and 5.6 GHz frequency bands. By combining the waveguide mode theory and the method of shooting and bouncing ray (SBR), it is found that the curvature of tunnels introduces an extra loss in the far-field region, which can be modeled as a linear function of the propagation distance of the signal in the curved tunnel. The channel of the cascaded straight and curved tunnel is thus characterized using the extra loss coefficient (ELC). Based on the ray-tracing (RT) method, an empirical formula between ELC and the radius of the curvature is provided for 3.5 GHz and 5.6 GHz, respectively. Finally, the accuracy of the proposed model is verified by measurement and simulation results. It is shown that the proposed model can predict path loss in cascaded tunnels with desirabl...