Channel measurements and models for high-speed train wireless communication systems in tunnel scenarios: a survey

Abstract

The rapid developments of high-speed trains (HSTs) introduce new challenges to HST wireless communication systems. Realistic HST channel models play a critical role in designing and evaluating HST communication systems. Due to the length limitation, bounding of tunnel itself, and waveguide effect, channel characteristics in tunnel scenarios are very different from those in other HST scenarios. Therefore, accurate tunnel channel models considering both large-scale and small-scale fading characteristics are essential for HST communication systems. Moreover, certain characteristics of tunnel channels have not been investigated sufficiently. This article provides a comprehensive review of the measurement campaigns in tunnels and presents some tunnel channel models using various modeling methods. Finally, future directions in HST tunnel channel measurements and modeling are discussed.Keywords 5G, HST, tunnel scenarios, tunnel channel measurements, tunnel channel models, non-stationary statistical properties. CitationLiu Y, Ghazal A, Wang C X, et al. Channel measurements and models for high-speed train wireless communication systems in tunnel scenarios: a survey. Sci China Inf Sci, 2016, 59(1): xxxxxx, doi: xxxxxxxxxxxxxx IntroductionHigh-speed trains (HSTs) have experienced a rapid development recently [1], and wireless technologies for HST communications will be considered as an important issue in the fifth generation (5G) wireless communication networks [2]. With the number of HST users increasing, numerous communication data need to be transmitted to train passengers through wireless channels. Therefore, high-capacity and reliable HST communication networks regardless of users' locations or speeds, are required. In order to meet these requirements, HST wireless communication systems need to mitigate various challenges resulting from the high * Corresponding author (email: cheng-xiang.wang@hw.ac.uk) 2 Liu Y, et al. Sci China Inf Sci speed of the train, such as frequent handovers, large Doppler spreads, and fast travel through different HST scenarios [3]. Currently, the most widely used HST communication system is the Global System for Mobile Communication Railway (GSM-R) [4]. It can be used for the train communication and control. However, it cannot satisfy the increasing communication requirements of high data rates. In recent years, the Long-Term Evolution-Railway (LTE-R) system, which is based on the LTE-Advanced (LTE-A) system, has been recommended to replace the GSM-R. Both of them adopted the conventional network architecture in which HST users inside the train communicate with outdoor base stations (BSs) directly. However, such an architecture results in high penetration losses when the signals travel into the carriages and leads to a spotty coverage, which will result in the handover failure or the high drop calls rate [4]. To overcome the above problems, the promising mobile relay station (MRS) solution has been proposed for future HST communication systems to solve the spotty coverage problem and mitigate ...

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