GSM-R and ETCS CoordinationIRCE 2011 Lille; October 25th 2011

ETCS and GSM-R to be one system GSM-R and ETCS face some challenges:o o Usual situation: ETCS is installed after GSM-R deployment Also, GSM-R and ETCS engineering are mainly in touch for coverage and QoS requirements

Certification and authorization are legally necessary and should not be seen as a problem:o o o Certificates of conformity for IC GSM-R network to be verified as part of the CCS Trackside subsystem Verification of ETCS on board and track systems as part of the On-board and Trackside CCS subsystems

For ETCS L2, the verification of the CSS Trackside and Onboard subsystems includes the integration between ETCS and GSM-R25/10/2011 IRCE 2011 2

ETCS and GSM-R to be one systemAPPLICATION LEVEL RBCConnection to train antenna

Transmission network

Configuration requiredTransmission (generally ISDN) Rack ISDN modems

OBU

EDOR

SIM

Internal installation

Configuration required

GSM-R Core Network

GSM-R call

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ETCS and GSM-R to be one system

TSI should not be seen as a procurement list, but as a minimum requirement list for interoperability: there are many more items to be determined when installing ERTMS L2.It is not possible to generalize a solution: fine tuning of the network to respect local conditions is needed. Engineering is required to take into account GSM-R and ETCS requirements, together with the technical specifications of each element.25/10/2011 IRCE 2011 4

ETCS and GSM-R : some points to take into account (I)OPERATION and design

the Network ID list may force an undesired behavior of the EDOR on network registration.SIM

there is no indication of how to handle the list of available networks (give preference to GSM-R, or only subscribe GSM-R). This may lead to not having any GSM-R network in the list : the OBU sees there is no modem available. Cab radios do not present this situation. A vehicle may have this issue but go unnoticed if it has not travelled through areas with high power from public networks.25/10/2011 IRCE 2011 5

EDOR

ETCS and GSM-R : some points to take into account (II)OPERATION and design EDOR

management from OBU: there is no description of the notification that the OBU should receive when an EDOR is not available, nor the actions to be taken in that case. This may lead to a non active EDOR that is not detected on time and it avoids fast recovery of the equipment.

Coordination example: a determined OBU always tries to establish a call through EDOR 1 and 2 in this order, even if it has failed to call through EDOR 1 earlier. No status check is done periodically. This increases the time to set up the connection: may lead to T_NVContact expiration.

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ETCS and GSM-R : some points to take into account (III)SYSTEM design EDOR

Throughput: there is no minimum value for this element. This means it is not possible to establish the maximum amount of data that can be transmitted. Different ETCS lines may have different parameters and special care has to be taken with the buffer size for queuing information to be sent and received.

Coordination example: Position report configuration. The only restriction is that it should be sent every 5 seconds as maximum. There is no harmonized value for this. If other information has to be sent as well or if the train is travelling in a lower quality area where repetitions will be frequent, there is a risk of congestion in the EDOR that may be underestimated.25/10/2011 IRCE 2011 7

ETCS and GSM-R : some points to take into account (IV)SYSTEM design there is no indication on how to manage the set of modems in the RBC . This may lead to a modem that is not active that is not detected on time and it avoids recovery of the equipment.Rack ISDN modems

Coordination example: In a certain RBC, calls are distributed amongst the modems starting from 1-n. If the first modem is busy, the system tries the following. There is no previous polling to determine if a modem is busy or if it is out of service, this increases the call establishment time and avoids the possibility of any automatic action on the modem to recover it.25/10/2011 IRCE 2011 8

ETCS and GSM-R : some points to take into account (V)SYSTEM design

RBC modems Throughput: there is no minimum value for this element. This means it is not possible to establish the maximum amount of data that can be transmitted. Different ETCS lines may have different parameters and special care has to be taken with the buffer size for queuing information to be sent and received. Coordination example: on areas where there are frequent repetitions, together with long packets (MA update, track description), there is a risk of congestion in the modem that may be underestimated.25/10/2011 IRCE 2011 9

Rack ISDN modems

ETCS and GSM-R : some points to take into account (VI)SYSTEM design Timing signal in the transmission to the RBC. A slight inaccuracy may lead to frame misalignment and some frames may be received as corrupted. RBC-RBC handover (specially at country borders, where each RBC belongs to a different network) is a particular case. Coordination Example : accumulative error in the timing signal for the frame composition leads to data corruption, which involves repetition of frames. This situation also increases the congestion risk. In RBC-RBC handover, where each RBC communicates with a different MSC, this could be seen more frequently.25/10/2011 IRCE 2011 10

ETCS and GSM-R : some points to take into account (VII) SYSTEM design Reshaping of GSM-R cells. Cell handover increases the repetitions and therefore, the risk of data loss or corruption. This is critical in some cases such as: - RBC Handover: cell - Proximity of signal: if cellboundary shall not be coincident with RBC handover point.Position Report: location A Repeats Position RBC sends order to Report: stop the train, location A because it reports a position previous to the already occupied track!

Cell 1 A25/10/2011

Cell 2BIRCE 2011

boundary lies where a line signal (or stopping point) is located, the risk of repetition in the area will be high. This may lead to a delay in the reception of a Position Report, which contains the previous mode (i.e. SR) and position when the packet was sent. When the message arrives to the RBC, it reports a previous position and may be interpreted as an unsafe situation, forcing the train to stop. EDOR and RBC throughput may also affect the delay.11

ETCS and GSM-R : some points to take into account (VIII)NETWORK CAPACITY and use Special call profile to be studied in high call density areas and depots. - OBU in L2 shall report every mode change. This includes passing from SLto SB or to IDL, or leaving SH. In a station, all the trains will be making calls to report such changes. The RBC will not send a disconnect order to the trains that report SB. Consequence: increase GSM-R network usage. Other calls may not be possible (SH calls + VGCS + other ETCS calls).

- Delay of cell handover: cells with high density of ETCS L2 traffic may have all the frequencies allocated, and the incoming call may need to preempt channels in the cell or it will be progressed through another cell. This increases the cell handover time and it has an impact on the quality of the link: more frequent errors or corruption.25/10/2011 IRCE 2011 12

ETCS and GSM-R : remember that

Railways interoperability: a train compliant with TSI requirements means it can run seamlessly through borders.

Pay attention that "local solutions" for the network do not export requirements, affecting the behaviour and performance of a TSI compliant CCS On-board subsystem.

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ETCS and GSM-R : what is the message ETCS and GSM-R have to be seen as a unique system: o network planning and engineering o requirements for GSM-R network to be verified together with ETCS needs TSI are not specifications for a system, they only cover requirements for interoperability. Study of the specific characteristics of the system cannot be substituted by TSI requirements.

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GSM-R and ETCS CoordinationIRCE 2011 Lille; October 25th 2011