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Advances in Communications-Based Train Control Systems by F. Richard Yu

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213
Chapter 10
Cognitive Control for
Communications-Based
Train Control Systems
Hongwei Wang and F. Richard Yu
Contents
10.1 Introduction ..........................................................................................214
10.2 Overview of Cognitive Control .............................................................216
10.2.1 Cognitive Control Approach to CBTC Systems ......................217
10.3 Cognitive Control .................................................................................218
10.4 Formulation of Cognitive Control Approach to CBTC Systems ............ 221
10.4.1 Train Control Model ...............................................................221
10.4.2 Channel Model in MIMO-Enabled WLANs ..........................223
10.4.3 Q-Learning in the Cognitive Control Approach ......................225
10.4.3.1 System States and Actions ......................................225
10.4.3.2 Reward Function ................................................... 226
10.5 Simulation Results and Discussions ....................................................... 231
10.5.1 Parameters of Train Dynamics ................................................231
10.5.2 Parameters of the ATO ............................................................232
10.5.3 Parameters of the Wireless Channel ........................................233
10.5.4 Simulation Results and Discussions ......................................... 233
10.6 Conclusion ............................................................................................242
References .........................................................................................................243
214 Advances in Communications-Based Train Control Systems
10.1 Introduction
Urban rail transit systems have developed rapidly around the world in the recent
past. Due to the huge urban trac pressure, improving the eciency of urban rail
transit systems is in high demand. As a key subsystem of urban rail transit systems,
communications-based train control (CBTC) is an automated train control system
using train–ground communications to ensure the safe and ecient operation of
rail vehicles [1]. CBTC can improve the utilization of railway network infrastruc-
ture and enhance the level of service oered to customers [2].
As urban rail transit systems are built in a variety of environments (e.g., under-
ground tunnels, viaducts, etc.), there are dierent wireless network congurations
and propagation schemes. For tunnels, the free space is generally adopted as the
propagation medium. However, the leaky coaxial cable is also an option, such as
Tianjin Subway lines 1 and 2 built by Bombardier. For the viaduct scenarios, leaky
rectangular waveguide is a popular approach, as it can provide higher performance
and stronger anti-interference ability than the free space [3]. In addition, due to the
available commercial o-the-shelf (COTS) equipment, wireless local area networks
(WLANs) are often adopted as the main method of train–ground communications
for CBTC systems [4].
Building a train control system over wireless networks is a challenging task. Due
to unreliable wireless communications and train mobility, the train control perfor-
mance can be signicantly aected by wireless networks [5]. Because CBTC systems
are safety critical, trains usually run according to the front trains state, including
velocity and position. When a wireless network brings large communication latency
caused by unreliable wireless communications or handos, the current train may
not be able to obtain the accurate state information of the front train, which would
severely aect train operation eciency, or even cause train emergency brake.
e performance issues in railway environments have attracted a lot of interest
recently. A fast hando algorithm suitable for passenger lines is proposed in [6] by
setting a neighboring cell list to facilitate hando operations. In [7], a novel hand-
o scheme based on on-vehicle antennas is introduced. e authors of [8] propose
a cross-layer hando design in for multiple-input and multiple-output (MIMO)-
enabled WLANs in CBTC systems. In [9], energy-ecient train control schemes
are studied in CBTC systems.
Although these above excellent works have been done to study CBTC systems
from both train–ground communication and train control perspectives, these two
important areas have traditionally been addressed separately in the CBTC literature.
However, as shown in the following, it is necessary to jointly consider these two
advanced technologies together to enhance the level of safety and services in CBTC
systems. e motivation behind our work is based on the following observations.
Most existing CBTC systems are based on the COTS equipment, in which
traditional design criteria (e.g., network capacity) are used in the design and

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