1. Communication Based Train Control
Navneet Kaushik
DMRC

2. DMRC’s mission
Complete the Metro project without cost and time over run
Catch up with the state of art technology
Started Metro operation in 2002 in Delhi with track circuit based CATC (first time in India)
Decided to go for CBTC for Phase III on two independent lines in 2012 – around 90 Kms
Also decided UTO on these lines (again first time in India)

3. Scenario in the country:
CBTC projects being executed by DMRC
City
Line
Length
Stations
Headway
Operation
Traction
SIG Supplier
Delhi
Line-7
58 KM 38
90sec
GoA4
25KV AC
Bombardier
Line-8
38 KM 25
90 sec
Nippon Signal
KOCHI
26 KM 22
GoA2
750V DC
Alstom
Noida-Greater Noida
29 KM 21
Tender yet to be awarded
Scenario in the country:
Apart from these, other CBTC projects in pipe line
are Hyderabad, Lucknow, Vijaywada, Vizag, Nagpur,
Ahemedabad, Kolkata and Mumbai

4. DELHI METRO MAP INCLUDING PHASE III

5. Need for improvement Key challenges faced today increasing traffic,
absolute passenger safety and security,
travel comfort demands,
real time multimedia information and entertainment in stations or in train
Operations need dynamically adjustable systems while maintaining Safety and security
Energy efficiency

6. Solution – Communication at the core
Signalling draws its strength from efficient computing and Telecom
Signalling & Telecommunication are coming closure
to deliver a safer, efficient and passenger friendly Rail Transport system
to give quick response to dynamics
Typically:
Data backbones on Metro Rail– from 100 Mbps to 10 Gbps now
Link between train to wayside – wi fi to LTE in future

7. Two different applications
1. Signalling and Train control – the vital one
low bandwidth (below 100 kbps) but high availability (at least 99.99%),
highly robust and reliable
CBTC (Communication Based Train Control) for metros or ETCS (European Train Control System) for mainline trains.
2. Passenger Information, maintenance, video surveillance, CCTV, internet access – the non vital one
much higher bandwidth (train-to-ground and ground-to-train),
lesser robustness can be accepted

8. Progress on Signalling front – Telecom upgrade automatic
TRACK VACANCY DETECTION
Track circuit Axle counter Radio based (CBTC)
TRAIN CONTROL
No ATC Train stop Speed code Distance To Go Moving Block
INTERLOCKING
Mechanical Relay based Electronic

9. Definition of CBTC as per IEEE 1474 standard
CBTC system is a "continuous, automatic train control system utilizing high-resolution train location determination, independent of track circuits; continuous, high-capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing Automatic Train Protection (ATP) functions, as well as optional Automatic Train Operation (ATO) and Automatic Train Supervision (ATS) functions."

10. Highlights of the definition
Location determination independent of track circuit
Continuous detection
High capacity train communication
Bidirectional train to wayside data communication
Solution – wifi radio working in ISM band taking information from onboard ATP based on inputs from odometer, beacons etc. and transferring this information to track side ATP to calculate Movement Authority

11. CBTC Functionality – Normal Mode
3. Trackside CBTC calculates the point to be protected ( ) ), by the tail of train B
2. The ONBOARD RADIO on train B transmits its position ( ) to the CBTC trackside equipment
TRACKSIDE
CBTC
4. The TRACKSIDE RADIO continuously transmits to the following train (A) the point to be protected ( ) )
TRACKSIDE
Radio
Controller
Trackside Radio
Trackside Radio
Trackside Radio
Radio
Train
CBTC
CBTC
Radio
Train A B B A
5.The ONBOARD CBTC on train A calculates the safety curve and applies it to the train to be protected
1. Based on the odometry, train B calculates continuously its position (and recalculates tolerances after passing over the track balises)

12. CBTC Functionality – Mixed Mode
3. Trackside CBTC knows at all times the existence of trains, and locates the point to be protected ( ) ) behind the last track section occupied by train B
TRACKSIDE
CBTC
4. The TRACKSIDE RADIO continuously transmits to the following train (A) the point to be protected ( )
TRACKSIDE
Radio
Controller
Interlocking
Trackside Radio
Trackside Radio
Trackside Radio
2. The interlocking continuously provides information on the track circuits occupied to the TRACKSIDE CBTC
Radio
Train
CBTC
(NO-COMN) B A
5.The ONBOARD CBTC on train A calculates the safety curve using the point to be protected ( )
1. A non-communicating train (B) does NOT transmit its position but occupies track section

13. Advantages of CBTC
Moving block instead of fixed block hence Optimized train speeds to gain best line capacity
Ease of upgradation to Driverless system
Ease of maintenance;
Easy expansion;
Immunity against interference;
Ease of Obsolescence management;
Minimum trackside equipment.

14. Grade of Automation

15. Some considerations for design
Fallback
Frequency availability and interference
UTO from day one or upgradation later
Overlap
Station layouts to match headways
PSD commands
And many more

16. Failure and Fallback
In a CBTC system if the communications link with any of the trains is disrupted then corresponding parts of the system have to enter a failsafe state until the problem is rectified.
Depending on the severity of the communication loss, this state can range from vehicles temporarily reducing speed, coming to a halt or operating in a degraded mode until communications are re-established.
If duration of communication failure is permanent, contingency operation need to be implemented - Manual operation and absolute block

17. Fallback Signaling
To handle this situation or do operation in case of failure of primary train detection due to communication loss, simplest method is to guide the driver over phone about his movement authority. OR
provide secondary means of train detection and resort to absolute block working with the help of signals
Considerations:
Capital cost
Number of track side equipment - maintenance
Effect on operation
Mixed mode operation

18. Methodology adopted by DMRC

19. Frequency issues – ISM band
World over wi-fi in ISM used
Mainly in 2.4 GHz band
Various techniques used to have reliable communication (mostly proprietary)
Main issues:
Jamming – during VIP movement
Congestion in 2.4 GHz band – where metro going through thickly populated areas

20. Frequency issues – ISM band
Demand for CCTV from train is growing
So two frequency bands are needed – one for CBTC and one for CCTV
2.4 GHz already heavily utilized
CBTC needs low throughput but highly stable and interference free
Most of the vendors have proven CBTC products in 2.4 GHz
5.8 GHz has limited bandwidth (WPC restriction) making it unsuitable for CCTV
Allow wider band in 5.8 GHz
Preferably reserve a frequency band for railway

21. Upgradation to UTO later or straight away UTO implementation?
Main requirements of UTO
Normal operation by onboard and track side computers communicating continuously
Manual functions (in case of failure) to be done remotely which requires a communication channel of sufficient bandwidth to deal with alarms and remote commands
The basic requirement is full filled by CBTC by default
The investment in UTO is very low if decided initially compared to upgradation later
Choice with operator if to use UTO as default mode of operation

22. Overlap requirement
Main line railway have requirement of signal overlap – Absolute block working
CBTC implements moving block
Train always remain protected hence no need of signal overlap
Signal overlap needed only in fallback (rare)
If provided, Moving Block not available for a certain distance – un necessary gap created
Conscious decision required

23. Effect of overlap

24. Terminal layout Demand – improved headway
Signaling systems capable of providing
Layout of terminal stations and intermediate turnback stations remain a bottleneck
Variety of layouts available
Need to decide in the beginning of project

26. PSD commands Need for best end to end run time
Demand for PSD increasing for passenger protection and more space on platform
Train door and PSD opening and closing time already high (2.5 s and 3 s respectively)
Can’t afford delay in transfer of door open and close command from Onboard to PSD at station – two paths
On board – zone control – station control (CBI) – PSD
On board – station control - PSD

27. There are many more issues
If one really wish to get the best results from CBTC, consider such issues in advance while planning

28. Thanks