Juan Moreno García-Loygorri

Delay Spread and Electromagnetic Reverberation in Subway Tunnels and Stations

This letter presents an extensive campaign of wideband propagation measurements conducted in a modern subway environment in Madrid, Spain, at 980 and 2450 MHz. Measurements have been made using a channel sounder in a realistic environment of tunnel and station. Based on the measurement results, the principal parameters, such as mean power and delay spread, have been extracted for wideband propagation modeling. Furthermore, the results have been used to model electromagnetic reverberation, quality factor, and transition region between tunnel and station. The quantitative results provide a detailed wideband model of subway environment, as well as determine the design tradeoffs inside real tunnels and stations, in terms of optimal frequency band, antenna position, and expected multipath.

2.6 GHz Intra-Consist Channel Model for Train Control and Management Systems

This paper presents a full characterization of the communications channel inside a train vehicle, in both narrow and wideband configurations. The purpose of this characterization is to be one of the first steps to check the feasibility of a wireless implementation of a train-control management system, a service which has been always carried over a wired network. Many different train topologies and scenarios have been taken into account in this paper (continuous and non-continuous train; train inside a tunnel, open-air or depot) and different results have been obtained (path-loss, angle of arrival, power-delay profile, and delay spread). The results show significant differences between continuous and non-continuous trains, and also highlight the importance of having a proper channel model with one slope per train car, instead of having only one slope for the whole train.

Wideband Channel Modeling for mm-Wave inside Trains for 5G-Related Applications

Passenger trains and especially metro trains have been identified as one of the key scenarios for 5G deployments. The wireless channel inside a train car is reported in the frequency range between 26.5 GHz and 40 GHz. These bands have received a lot of interest for high-density scenarios with a high-traffic demand, two of the most relevant aspects of a 5G network. In this paper we provide a full description of the wideband channel estimating Power-Delay Profiles (PDP), Saleh-Valenzuela model parameters, time-of-arrival (TOA) ranging, and path-loss results. Moreover, the performance of an automatic clustering algorithm is evaluated. The results show a remarkable degree of coherence and general conclusions are obtained.

Keyholes in MIMO-OFDM: Train-to-Wayside Communications in Railway Tunnels

One of the key challenges in railway engineering is how to provide passengers an efficient, secure, and safe service. To achieve this, operators and stakeholders demand robust and high-capacity train-to-wayside broadband radio. Current radio technologies implement MIMO (Multiple-Input Multiple-Output) technology, whose use requires a good characterization of the propagation. In this paper, the results of an experimental campaign on MIMO propagation in subway tunnels are presented. The campaign makes use of an OFDM testbed at roughly 600 MHz, allowing the measurement of the channel transfer matrix under different conditions regarding polarization, antenna separation, tunnel cross section, power allocation algorithm, and so forth. Particular attention is paid to the probability of appearance of keyholes, which imply a severe degradation of the MIMO performance even when transmitter and receiver antennas are uncorrelated. The measurements are carried out using a train that travels at the normal operative velocities. As a result of the measurements, it has been found that the use of vertical polarization at both terminals is advantageous and that, on average but for a narrow margin, λ-spaced antennas outperform λ/2-spaced ones (90% capacities of 7.00 and 6.76 bps/Hz, resp.), although the latter show a lower probability of keyholes. However, keyhole probabilities are always below 2%, so their influence on the performance of the whole system is limited.

Propagation at mmW Band in Metropolitan Railway Tunnels

The next generation of mobile communications, 5G, will provide a wideband network based on microwave and millimeter-wave (mmW) communication radio links with the goal of fulfilling the strict and severe requirements of the future test cases. In particular, this paper research is focused on mmW bands in metropolitan railway tunnels. For that purpose, a propagation measurement campaign was performed at 24 GHz band in a passenger train on a realist subway environment, and these results were combined with simulations ad hoc for tunnels and a theoretical modal propagation model. A narrowband and a wideband study have been conducted with the aim of obtaining the path loss, fading, power-delay profile, and angle of arrival, taking into consideration horizontal and vertical polarization in the receiving and transmitting antennas. This validation can be used to design and deploy wideband mobile communication networks at mmW bands in railway scenarios.

Reverberation Time in Vehicular Cabins

This paper research is focused on the reverberation time produced inside cabins where the influence of windows on wide-band signals is substantial. This kind of scenarios are important for the new generations of wireless communications since high-density scenarios with high-traffic demand are one of the keys environments. The study presents a preliminary measurement campaign in a close-room of wideband signals in the frequency range between 1.7 to 6 GHz. Based on the measured s21 parameter, the power delay profile has been obtained in order to analyze the diffuse scattering produced inside this particular environment.

Characterization of a Wireless Train Backbone for TCMS

This paper presents a both narrowband and wideband measurement campaign carried out in a Metro environment in order to assess the feasibility of a wireless link for the backbone train communications network. This backbone is the part of the network that links all the vehicles in the consist (A consist is a single vehicle or a group of vehicles that cannot be uncoupled during normal operation.). All the measurements were taken using a channel sounder and also an outdoor-to-indoor link was measured in order to compare with the outdoor-to-outdoor one. The obtained results are the path-loss, power-delay-profiles (PDP), mean delay, RMS spread and also a characterization of the fading is provided.

A Deterministic Two-Ray Model for Wideband Air Ground Channel Characterization

A two-path deterministic model is developed with an analytical dispersion delay computed solution for two common types of flight. From the results, it is deduced that an optimal antenna for the payload communication link in the Ground Station for flat environments should be a λ/4 linear monopole with a ground plane and vertical polarization at a height as close as possible to the ground.

Narrowband Characterization of a Train-to-Train Wireless Link at 2.6 GHz in Metro Environments

A Train-to-Train (T2T) wireless link at 2.6 GHz is characterized for three different metro environments: tunnel, station and open-field. A narrow- band measurement system is used, and obtained attenuation results are analyzed and modeled. The analysis indicates that reflections coming from the environment allow the RF signal to reach higher distances. In this sense, the station environment is the most reflective environment, while the open-field is the opposite situation, and the tunnel an intermediate case. Path-loss models are also obtained for these T2T link; these models allow to estimate the behavior of the link in each metro environment. A statistical analysis of the received signal is also done, and a fit with a log-normal distribution is obtained.

Wireless Communication Systems for Urban Transport

This chapter describes the main features of the wireless communication systems of urban rail and related applications. The perspective will be complete: application, network and physical layers will be discussed. Moreover, to properly address some of the challenges that these systems face, we will provide a deep insight into propagation issues related to tunnels and urban areas. Finally, a detailed survey on the directions of research on all these topics will be provided.