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ERTMS Certification Questions and Answers  
1. Are Subsets 119, 120 and 121 mandatory in the CCS TSI?
The above mentioned subsets are listed in the “List of supporting informative specifications - Set of specifications # 2” with version number as well as in the “Set of specifications # 2 (ETCS baseline 3 and GSM-R baseline 1)”
Are these subsets mandatory and do NoBos have to check the compliance?
The 3 subsets are NOT mandatory at the moment.
-      Subset 121 is NOT listed in the CCS TSI Annex A, nor in the informative documents of the CCS TSI Application Guide. Obviously, as it is not listed in the CCS TSI, it is not mandatory.
-      Subsets 119 and 120 are listed in the CCS TSI without version and with a note (“Reference to these specifications will be published in the Application Guide, waiting for clarifications on the rolling stock side of the interface”). The intention is to make them mandatory, once an agreement is reached on the content. At that moment, they will be included in the Annex A of the CCS TSI. Work has not finished yet. Therefore, in the meantime, they have to be considered as informative documents.
Application Guide documents are informative:  NoBos do not have to check compliancy to them.
2. Do NoBos have to check the fulfilment of Subset-093 when assessing a GSM-R network?
In EIRENE FRS, the following requirement is found:
2.3.13 Where ERTMS/ETCS level 2 or 3 is implemented, the network shall be capable of supporting data communications for that train control system with the required quality of service. (MI)
2.11.1 Where ERTMS/ETCS level 2 or 3 is implemented, the Quality of Service requirements as specified in document [SUBSET 093] and the test specification [ERTMS/GSM-R QoS Test Specification] are applicable. (I)
Is it the NoBo task to check the performance requirements in order to assess the compliancy to FRS 2.3.13?

The FRS requirement 2.3.13 (MI) imposes the obligation in the network to support data communications in case it is going to be used for ETCS Level 2 or 3. This is the reason for classifying this requirement as MI (mandated by the CCS TSI). The NoBo has to verify that, if the network is going to be used for ETCS L2 or 3, it supports data communications.
In the FRS, the meaning of the clause is that the network should be prepared for the data communication. In fact, SRS 3.2.2 and 3.2.3 have to be fulfilled (and verified by the NoBo).
There is currently no mandatory quality of service stated in the TSI, therefore, the reference to the “required quality of service” is not to be understood as something to be verified by the NoBo. 
Subset-093 is listed in the CCS TSI Application Guide. Application Guide documents are informative:  NoBos do not have to check compliancy to them in general, unless a specific section is explicitly referred to in a mandatory requirement.
The required quality of service is currently a matter to be agreed at the project level. The check of the fulfillment of the required quality of service is out of the scope of the NoBo verifying the subsystem.
An assessor can be requested to check many additional items, in addition to those required by the TSI. This may be done, but always outside of the process for verification of the subsystem, as additional checks if requested by the applicant, in which case the assessor will be acting as a technical expert and not as NoBo.
In order to make clear the scope of the verification carried out for the FRS 2.3.13 requirement, a note in the Technical file can be added, stating that there is no specific QoS required in the CCS TSI, and therefore, no Qos verification has been done.
3. Why is Subset-093 not mandatory in the CCS TSI?
GSM-R performance is important for the safe integration between GSM-R and ETCS. ETCS suppliers ask for the evidence related to Subset-093 and they want to see it in the GSM-R EC Certificate.
Indeed, the performance of the radio network is very important to allow the ETCS Level 2 or 3 service to be operational. However, there is no definitive agreement on mandatory performance requirements for the network (Trackside subsystem) or for the different Interoperability Constituents (EDOR, ETCS on board-EVC, RBC), nor on the way to measure their performance. In this situation, the assessment by a NoBo is not possible.
Subset-093 includes requirements between the interface of the EVC and the EDOR, and the interface between the GSM-R network and the RBC. This does not correspond with the entities that the NoBo has to assess (Subsystems or ICs, as defined in the CCS TSI). Therefore, the document, as it is, is not suitable for the assessment of the Trackside subsystem or for the EDOR.