xv
Preface
Introduction
With rapid population explosion, improving rail transit speed and capacity is
strongly desirable around the world. Communications-based train control (CBTC)
is an automated train control system using high capacity and bidirectional train–
ground communications to ensure the safe operation of rail vehicles. As a modern
successor to traditional railway signaling systems using track circuits, interlockings,
and signals, CBTC can improve the capacity of railway network infrastructure and
enhance the level of safety and service oered to customers.
CBTC systems have opened up several areas of research, which have been
explored extensively and continue to attract research and development eorts. is
book features some of the major advances in the research on CBTC systems. e
contributed chapters in this book from leading experts in this eld cover dierent
aspects of modeling, analysis, design, testing, management, deployment, and opti-
mization of algorithms, protocols, and architectures of CBTC systems. A summary
of all of the chapters is provided in the following sections.
As the rst chapter of this book, Chapter 1, authored by Li Zhu, F. Richard Yu,
and Fei Wang, presents the background and evolution of train signaling/train con-
trol systems. en it introduces the main features and architecture of CBTC sys-
tems. Some challenges of CBTC systems are presented. e chapter also describes
the main CBTC projects around the world.
Chapter 2, authored by Kenneth Diemunsch, explains why transit agencies
decide to use CBTC for new lines or for upgrading their signaling systems. en,
the author explains the reason for performing specic tests at the factory or in the
eld and provides insight based on experience with several CBTC projects in the
last decade.
Chapter 3, authored by Vassilios Kappatos, Tat-Hean Gan, and Dimitris
Stamatelos, discusses nondestructive testing techniques that can be employed
to inspect rails and fastening parts as well as relevant research and development
work in this eld. As nondestructive testing techniques signicantly depend on
the nature of defects, a discussion about the defects that emerge on the rail infra-
structure is included. Finally, an overview of the capacity of the recent train
xvi ◾ Preface
protectionmethods mainly based on the CBTC is carried out for a complete
overview of all measures (nondestructive testing, train protection) that can be
used to avoid any potential and serious rail accidents.
Channel Modeling
Chapter 4, authored by Hongwei Wang, F. Richard Yu, Li Zhu, and Tao Tang,
develops a nite-state Markov channel (FSMC) model for tunnel channels in
CBTC systems. e proposed FSMC model is based on real eld CBTC channel
measurements obtained from a business operating subway line. Unlike most exist-
ing channel models, which are not related to specic locations, the proposed FSMC
channel model takes train locations into account to have a more accurate channel
model. e distance between the transmitter and the receiver is divided into inter-
vals, and an FSMC model is applied in each interval. e accuracy of the proposed
FSMC model is illustrated by the simulation results generated from the model and
the real eld measurement results.
Chapter 5, authored by Hongwei Wang, F. Richard Yu, Li Zhu, and Tao Tang,
discusses modeling the wireless channels with a leaky waveguide for CBTC sys-
tems. For viaduct scenarios, leaky rectangular waveguides are a popular approach,
as they provide better performance and stronger anti-interference ability com-
pared to free space. Based on the measurement results on the Beijing Subway
Yizhuang Line, the authors use polynomial tting and an equivalent magnetic
dipole method to build the path loss model. In addition, the Akaike information
criterion with a correction is applied to determine the distribution model of small-
scale fading. e proposed path loss model of the channel with a leaky waveguide
in CBTC systems is linear; the path loss exponent can be approximated by the
transmission loss of the leaky waveguide. e authors show that small-scale fading
follows a log-normal distribution, which is often referred to as the distribution
model of small scale fading in body area communication propagation channels. In
addition, the corresponding parameters of log-normal distribution are also deter-
mined from the measurement results.
Performance Analysis and Improvement
withAdvanced Communication Technologies
Chapter 6, authored by Li Zhu and F. Richard Yu, discusses the availability issue
of WLAN-based data communication systems in CBTC. e authors propose two
WLAN-based data communication systems with redundancy to improve availabil-
ity in CBTC systems. e availability of WLAN-based data communication sys-
tems is analyzed using the continuous time Markov chain model. e transmission
Preface ◾ xvii
errors due to dynamic wireless channel fading and handos that take place when
the train crosses the border of coverage areas of two successive access points are
considered to be the main causes of system failures. e authors then model the
WLAN-based data communication system behavior using the deterministic and
stochastic petri net, which is a high-level description language for formally speci-
fying complex systems. e deterministic and stochastic petri net solution is used
to show the soundness of the proposed continuous time Markov chain model.
edeterministic and stochastic petri net provides an intuitive and ecient way to
describe complex system behavior and facilitates the modeling of system steady-
state probability. Using numerical examples, the authors compare the availability
of the two proposed WLAN-based data communication systems with that of an
existing system that has no redundancy. e results show that the proposed data
communication systems with redundancy have much higher availability compared
to the existing system.
Chapter 7, authored by Li Zhu, F. Richard Yu, and Tao Tang, uses recent
advances in coordinated multipoint transmission/reception (CoMP) to enable
soft handos and consequently enhance the performance of CBTC systems.
CoMP is a new method that helps with the implementation of dynamic base
station coordination in practice. With CoMP, a train can communicate with a
cluster of base stations simultaneously, a system that is dierent from the cur-
rent CBTC systems, where a train can communicate with only a single base sta-
tion at any given time. e authors jointly consider CoMP cluster selection and
hando decision issues in CBTC systems. In order to mitigate the impacts of
communication latency on train control performance, they propose an optimal
guidance trajectory calculation scheme in the train control procedure that takes
full consideration of the tracking error caused by communication latency. en,
the system optimization of CBTC system with CoMP is formulated as a semi-
Markov decision process. Extensive simulation results are presented to show that
train control performance can be improved substantially in the proposed CBTC
system with CoMP.
Chapter 8, authored by Hailin Jiang, Victor C. M. Leung, Chunhai Gao, and
Tao Tang, proposes a multiple-input and multiple-output (MIMO)-assisted hand-
o scheme for CBTC WLAN systems with two or more antennas congured on
the train and at each access point. A location-based hando is proposed that takes
advantage of the fact that the train in a CBTC system can acquire its locations
accurately in real time. Information on train position from the mobile station is
sent simultaneously with hando signaling by means of MIMO multiplexing. e
signaling and data packets are recovered at the access points by means of MIMO
signal detection algorithms such as V-BLAST algorithms. e hando perfor-
mance, including the frame error rate of the hando signaling, the hando latency,
the error-free period, and the impacts on the inter-site distance, is analyzed and
compared with parameters associated with traditional hando schemes.
xviii ◾ Preface
Performance Analysis and Improvement
with Advanced Control Technologies
Chapter 9, authored by Bing Bu, F. Richard Yu, and Tao Tang, integrates the design
of trains’ control and train–ground communication through modeling the control
system of a group of trains in CBTC as a networked control system. eauthors
discuss packet drops in CBTC systems, introduce packet drops into the networked
control system model, analyze their impact on the stability and performance of
CBTC systems, and propose two novel control schemes to improve the perfor-
mances of CBTC systems with random packet drops. Extensive eld test and simu-
lation results are presented to show that the proposed schemes can provide less
energy consumption, better riding comfortability, and higher line capacity com-
pared to existing scheme.
Chapter 10, authored by Hongwei Wang and F. Richard Yu, uses recent advances
in cognitive dynamic systems in CBTC systems considering both train–ground
communication and train control. In the cognitive control approach, the notion
of information gap is adopted to quantitatively describe the eects of train–ground
communication on train control performance. Specically, as train–ground com-
munication is used to exchange information between the train and control center,
packet delay and drop lead to an information gap, which is the dierence between
the actual state and the observed state of the train. e wireless channel is modeled
as nite-state Markov chains with multiple state transition probability matrices,
which can demonstrate the characteristics of both large-scale fading and small-scale
fading. e channel state transition probability matrices are derived from real eld
measurement results. Simulation results show that the proposed cognitive control
approach can signicantly improve train control performance in CBTC systems.
Conclusion
e chapters in this book essentially feature some of the major advances in the
research on CBTC systems. erefore, the book will be useful to both researchers
and practitioners in this area. Readers will nd the rich set of references in each
chapter particularly valuable.
F. Richard Yu
Carleton University
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.