In this procedure the NRM client is requested by the NRM server to send a MBMS suspension report. This request for MBMS suspension report can be included in the MBMS bearer announcement and the NRM server may choose to only send this request for MBMS suspension report to a subset of all NRM clients.
Figure 18.104.22.168.2-1 illustrates a procedure in which the NRM client notifies the NRM server about an MBMS suspension decision in RAN.
The NRM server can decide on a subset of all VAL UEs in the MBMS broadcast area that shall report on MBMS bearer suspension. When the NRM server makes the decision of the VAL UE subset, consideration shall be taken to the location of the VAL UEs, since VAL UEs' location is dynamically changed. This means that the MBMS suspension reporting instruction may need to be updated regularly based on the VAL UEs mobility.
It is assumed that there is at least one active MBMS bearer
Based on the MBMS suspsension report received, the NRM server determines whether to switch to a new bearer (unicast or MBMS). If NRM server determines to switch to unicast bearer, then the NRM server sends the user plane delivery mode message to VAL server , and the VAL server sends the downlink data over the new bearer.
The NRM client that is not instructed to send an MBMS suspension report shall still detect the MBMS suspension indication from RAN (step 3). A NRM client shall in this case not send other types of report (e.g. MBMS listening reports).
The same procedure can be applied at MBMS resumption or other MBMS events that may be detected by the NRM client.
The NRM server is an instantiation of a GCS AS. For the NRM server to know the status of the MBMS bearer, and thus know the network's ability to deliver the VAL service, it is required that the network provides MBMS bearer event notifications to the NRM server. The different events notified to the NRM server include the MBMS bearer start result (e.g. when the first cell successfully allocated MBMS resources), including information if any cells fail to allocate MBMS resources to a specific MBMS bearer, the current status of the MBMS bearer, MBMS bearer suspension/resume or overload scenarios.
The BM-SC notifies the NRM server of certain MBMS related events including references to affected MBMS services areas or list of cells. Example of such events may be radio resources not available, overload, MBMS suspension.
Figure 22.214.171.124.2-1 shows the procedure for service continuity when a UE is about to move out of MBMS coverage or getting into good MBMS coverage by switching between MBMS bearer and unicast bearer.
It is assumed that a bearer (unicast or MBMS) has been activated by the VAL server for downlink delivery.
The NRM server makes the decision to switch between MBMS delivery and unicast delivery based on available information at the NRM server including the MBMS listening status report as described in clause 126.96.36.199. The NRM server notifies a user plane delivery mode to the VAL server.
During the switching, the VAL client simultaneously receives downlink data through both bearers (unicast bearer and MBMS bearer). If there is no downlink data to the VAL client, this step can be skipped.