1. Communications in Railway Centralized Traffic Control Systems
Mihai Dima
Iulian Adrian Chihaia
Maria Claudia Surugiu
Telematics and Electronics for Transports Department,
"Politehnica" University of Bucharest,
Transports Faculty
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

2. CONTENT Centralized traffic Data transmission trough track circuit
MATLAB application for a binary communication system
CONCLUSIONS
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

3. OBJECTIVES
Centralized Traffic Control (CTC) system for railways overlaps hierarchically over interlocking and fixed block installations that allows traffic control between railway stations and represents the management core and organization of railway traffic.
CTC - centralized control model decisions and related implementation actions concerning traffic control are carried out by the same entity and setting routes or changing signal aspects are tasks performed by remote control from the respective positions.
Network management involves the centralized traffic control for an optimum system with the following functions:
Ethernet network design;
maintenance and control the local network security;
remediation of faulty or failing system equipment; the correct management of the local network (IP, communications equipment, specific applications);
maintaining appropriate quality standards in terms of network configurations.
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

4. related work (1) Main benefits of CBS are:
allow each railroad administration to control their operations;
use of signaling principles and safety-critical standards;
costs of the system is comparable to other overlay systems;
reduce train collisions and protect railway workers;
vital monitoring for all wayside objects;
Figure 1. CBS architecture
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

5. related work (2)
Modern CTC contain an open interface wich allows interconnection of railway subsystems and improve operability for train controller.
All vital and non-vital objects are connected by a communication network with a distribuited arhitecture and redundant configuration.
This type of configuration for software and hardware ensure an excellent reliability, flexibility and expandanbility.
Figure 2. Modern CTC architecture
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

6. CENTRALIZED TRAFFIC (1)
Major advantages represented by the use of CTC in railway systems are:
increasing the efficiency in transport regulation on a section of movement consisting of several sections;
increasing the transportation capacity, achieved by adding the capacity increase due to CTC systems, a significant increase for low movement time, and the capacity increase due to fixed block installations, significantly higher for higher movement time;
better coordination in the exploitation because of the traffic movement regulation for a large railway section is done from a single point, the reports and telephone directives being replaced by graphics, data records, orders and CTC console orders;
reducing the maintenance and the operating staff.
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

7. CENTRALIZED TRAFFIC (2)
Computerization and automation of the systems and the use of the optical fibers allow the command and control of the traffic over large areas and the integration of all services in a management center, along with modern technologies of signaling, command and control.
The system design allows the integration of new facilities by adding or upgrading software or hardware modules (AVI, ATP, ATO).
Figure 3. CTC hardware design
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

8. Data transmission trough track circuit (1)
the track circuit operates in the frequency range of 5,6 kHz - 8,6 kHz and it modulates the carrier at a frequency of 100 Hz (corresponding to a transmission speed of 200 Baud).
The transmitter operates in one of the following ways:
Train detection
Data transmission
Figure 4. Block diagram for track circuit emitter
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

9. Data transmission trough track circuit (2)
Figure 7. Block diagram for track circuit receiver
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

10. MATLAB application for a binary communication system
The channel introduces a phase movement of each of the transmitted signals, so that the received signal in the absence of noise.
FSK modulation is one of the most used modulations due to the simplicity of obtaining the modulated signal and for demodulation available methods. It is mainly used in low speed data transmission.
Figure 10. Data transmission with FSK modulation
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

11. RESULTS
The modulation/demodulation FSK equipment have a medium complexity. The amplitude of the modulated signal is constant, so the power of signal can be easily controlled, which makes this kind of modulation used to limit the signal strength.
Figure 11. The correlator outputs for binary FSK demodulation
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA

12. Conclusions
The transmission of the information via data communication systems is limited in performance (volume, speed) by many factors, including the strength of the broadcast signal, the level of noise or the available bandwidth.
A problem was raised in this context, to find methods that allow the circulation of a useful informational content as close to the maximum transfer capacity of a communication channel as possible.
CRC method for error correction is suitable for railway track circuits communications, where data transmission speed from ground to train is not high (<1Mb), but data accuracy is critical for train safety.
ECAI 2016 INTERNATIONAL CONFERENCE  8th Edition, 30 June-02 July 2016 , Ploiești, ROMANIA