4.3 MBMS Specific Reference points

23.2463GPPArchitecture and functional descriptionMultimedia Broadcast/Multicast Service (MBMS)Release 17TS

4.3.1 Gmb

Signalling between GGSN and BM-SC is exchanged at Gmb reference point. 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.

MBMS bearer service specific Gmb signalling:

– The GGSN establishes the MBMS bearer context and registers at BM-SC.

– The GGSN or the BM-SC releases the MBMS bearer context and de-registers the GGSN from the BM-SC.

– The BM-SC indicates session start, update and stop to the GGSN including session attributes like QoS and MBMS service area.

User specific Gmb signalling:

– The BM-SC authorises the user specific MBMS multicast service activation (join) at the GGSN.

– The GGSN reports to the BM-SC the successful user specific MBMS multicast activation (join) to allow the BM-SC to synchronise the BM-SC MBMS UE context with the MBMS UE contexts in the SGSN and GGSN.

– The GGSN reports to the BM-SC when a user specific MBMS multicast service is released or deactivated (e.g. at implicit detach). The GGSN makes this report in order to synchronise the BM-SC MBMS UE context with the MBMS UE contexts in the SGSN and GGSN.

The BM-SC initiates the deactivation of a user specific MBMS bearer service when the MBMS user service is terminated.

BM-SC functions for different MBMS bearer services may be provided by different physical network elements. Further, MBMS bearer service specific and user specific signalling for the same MBMS bearer service may also be provided by different physical network elements. To allow this distribution of BM-SC functions, the Gmb protocol must support the use of proxies to correctly route the different signalling interactions in a manner which is transparent to the GGSN.

4.3.1a SGmb

The SGmb reference point has similar functions with the Gmb interface in control plane except for the Multicast Mode related functions. Specifically,

MBMS bearer service specific SGmb signalling:

– The BM-SC indicates session start, update and stop to the MBMS-GW including session attributes like QoS and MBMS service area, and some of attributes may be different from them in Gmb.

4.3.2 Mz

Mz is the roaming variant of the Gmb reference point with the same functionality as described under Gmb, i.e. with MBMS bearer and User specific signalling.

MBMS bearer and User specific Mz signalling is used between a BM-SC in the visited PLMN and a BM-SC in the home PLMN when MBMS services from the home PLMN are offered by the visited PLMN.

User specific signalling is used between a BM-SC in the visited PLMN and a BM-SC in the home PLMN when the visited PLMN offers MBMS user services to roaming users. This user specific Mz signalling provides home PLMN authorisation for MBMS user services that are provided by the visited PLMN. This mechanism supports only MBMS user service classes that are offered by the visited and by the home PLMN.

Mz may use proxying capabilities as described for Gmb, e.g. to proxy signalling between BM-SCs. An APN may be included in the signalling between BM-SCs, which is used to select an appropriate GGSN to access the MBMS service aiming for an optimized routing, resource saving, or operator policy.

NOTE: For EPS, the Mz reference point is not supported in this release.

4.3.3 Reference Points for Evolved Packet System

NOTE: The below listed reference points are applicable for the E-UTRAN and UTRAN MBMS Broadcast Mode (with or without counting) only.

M1: It is the reference point between MBMS GW and E-UTRAN/UTRAN for MBMS data delivery. IP Multicast is used on this interface to forward data.

M3: It is the reference point for the control plane between MME and E-UTRAN.

Sm: It is the reference point for the control plane between MME and MBMS GW.

Sn: It is the reference point between MBMS GW and SGSN (S4 based) for the control plane and for MBMS data delivery. Point-to-point mode is used on this interface to forward data..

SGi-mb: It is the reference point between BM-SC and MBMS GW function for MBMS data delivery.

SGmb: It is the reference point for the control plane between BM-SC and MBMS GW.

Protocol assumption:

– The Sm reference point is based on GTPv2-C.

– The Sn reference point is based on GTPv2-C and GTPv1-U.

– The M1 reference point is based on GTPv1-U.