In this scenario, the MC service server pre-establishes MBMS bearer(s) in certain pre-configured areas before the initiation of the group communication session. When a user originates a request for a group communication session for one of these areas, the pre-established MBMS bearer(s) is used for the DL media transmission.
The following steps needs to be performed prior the start of the MC group communication session over pre-established MBMS bearer:
-
MBMS bearer(s) is Pre-established
-
Announce the pre-established MBMS bearer to the MC service clients
When these preparation steps have been done the MC group communication session using MBMS bearer can start.
Both the media packets as well as the application level control signalling (e.g. floor control messages) to the receiving MC service clients are sent on the MBMS bearer. Optionally a separate MBMS bearer could be used for the application level control messages, due to different bearer characteristic requirements.
The procedure
Figure 10.7.3.1.2-1 shows only one of the receiving MC service clients using an MBMS bearer. There might also be MC service clients in the same MC group communication session that receive the communication on unicast bearers.
Pre-conditions:
-
The participating users are already affiliated.
Step 1a.
The MC service server determines to activate MBMS bearer. The activation of the MBMS bearer is done on the MB2-C reference point and according to
TS 23.468. This bearer will be used for the MC communication media.
Step 1b.
Optionally, the MC service server may also activate an MBMS bearer dedicated for application level control signalling. The activation of the MBMS bearer is done on MB2-C reference point and according to
TS 23.468.
Step 2a.
The MC service server passes the MBMS bearer info for the service description associated with the pre-established MBMS bearer to the MC service client. The MC service client obtains the TMGI, identifying the MBMS bearer, from the service description.
Step 2b.
The MC service server may pass the MBMS bearer info for the service description associated with the pre-established floor control MBMS bearer to the MC service client. The MC service client obtains the TMGI, identifying the MBMS bearer, from the service description.
Step 3.
The MC service client stores the information associated with the TMGI(s). The MC service client uses the TMGI and other MBMS bearer related information to activate the monitoring of the MBMS bearer by the MC service UE.
4. The MC service client that enters or is in the service area of at least one announced TMGI indicates to the MC service server that the MC service client is able to receive media over MBMS, whereby the MC service server may decide to use the MBMS bearer instead of unicast bearer for MC communication sessions.
Step 5.
An MC service group communication session is established.
Step 6.
As the MC service server transmits the media over the MBMS bearer, the media packets are detected and delivered to the MC service client.