Emulation of Radio Technologies for Railways: A Tapped-Delay-Line Channel Model for Tunnels

Abstract

Radio access technologies (RATs) are a key topic in railways, enabling them a better service rendering in terms of shorter headways between trains, higher safety levels and higher customer satisfaction. Very often, these railway RATs need a lot of time to be developed, tested and put into service, which implies a lack of efficiency and bottlenecks in the evolution of railway systems. To solve this situation, an emulation platform that considers both the physical layer and the network (this is, able to emulate the end-to-end chain) is envisaged in the EmulRadio4Rail project. Therefore, the physical layer of many railway scenarios must be emulated, which is a remarkable challenge because railways are very diverse. We see Tapped-Delay Lines (TDL) models as the most efficient way for emulation with the available hardware. In the literature, there are many TDL-based channel models for all the scenarios we considered but one: tunnels. Therefore, in order to fill this gap, we develop a novel TDL model for railway tunnels, considering the impact of the rolling stock (both high-speed railway (HSR) and subway trains). The proposed model allows the full characterization of this scenario in terms of power-delay-profile (PDP), Doppler spectrum and fading characteristics.INDEX TERMS Channel modelling, propagation, railway communications, tapped-delay-line models, tunnel.

Wave Propagation Modeling Techniques in Tunnel Environments: A Survey

“…TDL models need the best hardware requirements to be used in emulators [57]. The proposed model characterizes the power-delay profile (PDP), Doppler spectrum, and fading properties.…”

Zero on site testing of railway wireless systems: the Emulradio4Rail platforms

“…Thanks to their simplicity, well known Tapped Delay Line (TDL) models were considered for the proof of concept of the Emulradio4Rail project [6][7]. In addition, due to the absence of a valid channel model related to railway tunnels, a TDL model in tunnel (for both high speed and metro) has been also developed specifically [8]. At the same time, in order to take into account the characteristics of railway environments in a realistic way, different types of perturbations have been identified and also injected at RF level in the platforms [9].…”

Analysis and Modeling of Propagation in Tunnel at 3.7 and 28 GHz

“…However, this technique has several limitations in the implementation and analysis of RT signals. For example, an implementation through delay line time-domain analysis is minimal if the minimum delay is less than 8 ns (in which case, it will require a larger bandwidth (BW); for instance, a 1 ns time delay will require 1 GHz BW) [21]. While an alternative implementation utilizes the shooting and bouncing RT realization technique, this approach has the impediment of the hypothetical size of the receiver receiving the propagated ray [22,23].…”