The Gm reference point supports the SIP-based communication between a UE and a P-CSCF (acting as a SIP Proxy) in an IMS core network. The P-CSCF may be located in a visited IMS core network or in the User's Home IMS core network.
This reference point is used to exchange signalling between GGSN and a Broadcast-Multicast Service Centre (BM-SC). This represents the network side boundary of the MBMS Bearer Service from a control plane perspective. This includes user specific Gmb signalling and MBMS bearer service specific signalling.
These interfaces are used to support mobility between the SGSN and GGSN. The Gn interface is used when GGSN and
SGSN are located inside one PLMN. The Gp-interface is used if GGSN and SGSN are located in different PLMNs.
The Gn/Gp interface also includes a part which allows SGSNs to communicate subscriber and user data, when changing
The Gp interface provides the functionality of the Gn interface, plus security functionality required for inter-PLMN communication. The security functionality is based on mutual agreements between operators.
This interface allows for dynamic QoS-related service information to be exchanged between the Policy Decision
Function (PDF) and the Application Function (AF). This information is used by the PDF for service based local policy decisions.
This interface is used to exchange the data related to the location of the mobile station and to the management of the subscriber. The main service provided to the mobile subscriber is the capability to transfer packet data within the whole service area. The SGSN informs the HLR of the location of a mobile station managed by the latter. The HLR sends to the SGSN all the data needed to support the service to the mobile subscriber. Exchanges of data may occur when the mobile subscriber requires a particular service, when he wants to change some data attached to his subscription or when some parameters of the subscription are modified by administrative means.
The Gs interface is used to provide co-ordination between the GSM circuit
switched services controlled at the Visitor Location Register (VLR) and the GSM packet switched services controlled
at the Serving GPRS Support Node (SGSN). The procedures on the Gs interface are intended to optimise
the use of the resources when an MS supports both GSM circuit switched services and GSM packet switched services.