scope:

The present document describes the Rel-4 Core Network architecture as depicted in the Rel-4 version of the 3GPP/ETSI Technical Specifications for application on railway networks in order to provide the ability for railway operators to deploy a Rel-4 CN architecture, also known as Bearer Independent Core Network.

It then specifies the requirements on interfaces and procedures to operate such a Rel-4 Core Network architecture for railway usage.

The present document does not mandate Rel-4 CN architecture to become the reference architecture for railways, baseline for railway telecommunications remaining the Rel-99 version of the 3GPP/ETSI Technical Specifications.

Also the present document focuses on the changes from a Rel-99 to a Rel-4 CN architecture for the CS domain, as PS domain equipments and interfaces are not affected by the deployment of BICN.

The present document is focussing on the requirements concerning the architecture and the interfaces only. It does not take into consideration any other features or applications inserted into 3GPP/ETSI versions later than Rel-99.