The CBC is responsible for the management of CBS (cell broadcast service) messages and for determining the CBS delivery parameters
of the BSS/RNS. The CBC may be connected to several BSCs/RNCs. The CBC is regarded to be integrated as a node
into the core network.
The CDRs produced by the CDF are transferred immediately to the CGF via the Ga
reference point. The CGF acts as a gateway between the 3GPP network and the BD. It uses the Bx reference point for
the transfer of CDR files to the BD. The entity relationship between the CDF and the CGF is m:1, i.e. one or more
CDFs may feed CDRs into a single CGF.
The CN is constituted of a Circuit Switched (CS) domain and a Packet Switched (PS) domain (which includes GPRS
and EPC). These two domains differ by the way they support user traffic.
These two domains are overlapping, i.e. they contain some common entities. A PLMN can implement only one domain
or both domains.
The CSCF can act as
P-CSCF (Proxy CSCF),
S-CSCF (Serving CSCF),
E-CSCF (Emergency CSCF), or
I-CSCF (Interrogating CSCF).
The P-CSCF is the first contact point for the UE within the IM subsystem (IMS); the S-CSCF actually
handles the session states in the network; the E-CSCF handles certain aspects of emergency sessions such as routing an
emergency request to the correct emergency centre or PSAP; the I-CSCF is mainly the contact point within an
operator's network for all IMS connections destined to a subscriber of that network operator, or a roaming subscriber
currently located within that network operator's service area.
The CS domain refers to the set of all the CN entities offering "CS type of connection" for user traffic as well as all the entities supporting the related signalling. A "CS type of connection" is a connection for which dedicated network resources are allocated at the connection establishment and released at the connection release.
The C-SGN is a combined node EPC implementation option that minimizes the number
of physical entities by collocating EPS entities in the control and user planes paths (e.g. MME, S-GW, P-GW), which may be preferred in CIoT deployments. The external interfaces of C-SGN implementation option are the interfaces of
the respective EPC entity supported by the C-SGN, such as MME, S-GW, and P-GW.
A C-SGN supports sub-set and necessary functionalities compared with the existing EPS core network elements.
The Media Gateway terminates the signalling over the Mc interface from the (G)MSC servers. The Media Gateway
terminates the Iu transport network control plane signalling with its transport bearer. The Media Gateway also terminates the Iu user plane protocol. It
also terminates the bearer control signalling and the transport bearer over the Nb interface.
The Media Gateway contains bearer terminations and media manipulation equipment (e.g. transcoders, echo cancellers,
or tone senders). It may perform media conversion and framing protocol conversion.
The CSS is an optional element that stores CSG (Closed Subscriber Group) subscription data for roaming subscribers. The CSS stores and provides VPLMN specific CSG subscription information to the SGSN or MME.
The CSS is accessible from the MSC/VLR via the Hv interface, from the Gn/Gp SGSN via the Ghv interface, from the S4-SGSN via the S7d interface and from the MME via the S7a interface. The CSS is always in the same PLMN as the current MME.
The CTF, in every network element and service element that provides charging information, is
the focal point for
collecting the information pertaining to chargeable events within the network element,
assembling this information into matching charging events, and
sending these charging events:
towards the CDF via the Rf reference point for offline charging,
towards the OCS via the Ro or CAP reference point for online charging.