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Content for  TS 23.434  Word version:  19.4.2

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14.3.4A.8 Service continuity between 5G MBS delivery and unicast delivery  14.3.4A.9 Service continuity between 5G MBS delivery and unicast delivery  14.3.4A.10 VAL service inter-system switching between 5G and LTE 
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14.3.4A.8  Service continuity between 5G MBS delivery and unicast delivery  p. 270

14.3.4A.8.1  General  p. 270
This clause addresses the issue of VAL data delivery over MBS session, specifically, to maintain the service continuity when switching between 5G MBS delivery and unicast delivery.
14.3.4A.8.2  Service continuity for broadcast MBS session  p. 270
14.3.4A.8.2.1  General  p. 270
This solution provides the procedure which allows the NRM client to report the broadcast reception quality to the NRM server which is used to make the decision whether to use the unicast delivery to the VAL UE(s) which are suffering bad broadcast reception quality due to e.g., move out of the broadcast service area.
An NRM client monitors the broadcast MBS session to receive VAL data. Based on the received quality (e.g., radio level quality, RTP packet loss), the NRM client needs to inform the NRM server that the NRM client is able to receive the VAL data on the broadcast MBS session with sufficient quality or not.
This estimation of the broadcast reception quality may be dependent on, for example, the modulation and coding scheme (MCS) and measurements from the reference signals from the NG-RAN node(s), RTP packet loss, BLER of the received VAL data.
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14.3.4A.8.2.2  Procedures  p. 271
14.3.4A.8.2.2.1  Service continuity from broadcast to unicast  p. 271
The procedure in Figure 14.3.4A.8.2.2.1-1 illustrates the VAL UE which is receiving VAL data via broadcast MBS session is switched to unicast delivery because the VAL UE suffers from bad broadcast reception quality due to e.g., moving out of the broadcast service area. It shows only one of the receiving VAL UEs receiving the broadcast MBS session.
Pre-conditions:
  1. The VAL group communication is ongoing and the VAL data (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session.
  2. The NRM client is receiving the VAL data (e.g., DL media, application layer control signalling) via the broadcast MBS session.
  3. The NRM client(s) already have the associated information (e.g., SDP) to receive the unicast delivery during the group communication establishment phase.
  4. An VAL group communication session is ongoing and the DL VAL data is transmitted over broadcast MBS session.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.8.2.2.1-1: Service continuity from broadcast to unicast
Figure 14.3.4A.8.2.2.1-1: Service continuity from broadcast to unicast
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Step 1.
The NRM client detects that it suffers bad broadcast reception due to e.g., moving out of the broadcast service area of the announced MBS session ID. The NRM client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
Step 2.
The NRM client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is not sufficient to receive media. The NRM client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the VAL data has been received.
Step 3.
The NRM server based on the report from the participant, determines that the UE is not able to receive the media or the QoS requirements is not satisfied. The NRM server determines the VAL media (e.g., DL media, application layer control signalling) needs to be delivered via the unicast delivery to the reported NRM client.
Step 4.
If the unicast QoS flow is not satisfied, the NRM server interacts with the 5GC to update the QoS requirements.
Step 5.
The NRM server informs the VAL server to send the VAL data via the unicast delivery towards the reported NRM client by sending a user plane delivery mode message.
Step 6.
The NRM server sends the VAL media via the unicast delivery towards the NRM client which suffers bad broadcast reception quality.
Step 7.
The NRM client then receives the DL VAL data via both broadcast MBS session and unicast delivery.
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14.3.4A.8.2.2.2  Service continuity from unicast to broadcast  p. 272
The procedure in Figure 14.3.4A.8.2.2.2-1 illustrates the VAL UE receiving VAL data via unicast delivery being switched to broadcast MBS session as the UE enters the broadcast service area where the NG-RAN is broadcasting the VAL media of the ongoing group communication. The VAL UE now is able to receive the VAL data via the broadcast MBS session. Only one of the receiving VAL UEs receiving the broadcast MBS session is shown.
Pre-conditions:
  1. The VAL group communication is ongoing and the VAL data (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session in the broadcast service areas.
  2. The VAL UE is receiving the VAL data (e.g., DL media, application layer control signalling) via the unicast delivery.
  3. The NRM client has already received the broadcast MBS session announcement, MapVALGroupToSessionStream information and enters the broadcast service area.
  4. A VAL group communication session is ongoing and the broadcast MBS session is used by the VAL server to deliver the VAL data of the group communication. The VAL UE is receiving the VAL data via the unicast delivery.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.8.2.2.2-1: Service continuity from unicast to broadcast
Figure 14.3.4A.8.2.2.2-1: Service continuity from unicast to broadcast
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Step 1.
The NRM client detects that it is able to receive the broadcast media due to e.g., moving into the broadcast service area of the announced MBS session ID. The NRM client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
Step 2.
The NRM client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is sufficient to receive VAL data. The NRM client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the VAL data has been received.
Step 3.
The NRM server determines the VAL UE is able to receive the VAL data via the the broadcast MBS session, and the NRM server sends a user plane delivery mode to the VAL server indicating to stop the unicast delivery.
Step 4.
Based on the MapVALGroupToSessionStream received before, the NRM client receives the DL VAL data via both the broadcast MBS session and the unicast delivery.
Step 5.
The VAL server, based on the user plane delivery mode message, determines to stop sending the VAL data (e.g., DL media, application layer control signalling) via the unicast delivery to the reporting NRM client. After then, the NRM client receives the VAL data only via the broadcast MBS session.
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14.3.4A.8.3  Service continuity for multicast MBS session  p. 274
14.3.4A.8.3.1  General  p. 274
The NRM server may also switch between multicast and unicast by utilizing application layer mechanisms similar to switching between broadcast and unicast as specified in clause 14.3.4A.8.2. If indicated in the MBS session announcement information, the NRM client reports the monitoring state (i.e., the reception quality of the MBS session) back to the NRM server.
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14.3.4A.9  Service continuity between 5G MBS delivery and unicast delivery  p. 274

14.3.4A.9.1  General  p. 274
This clause addresses the issue of VAL data delivery over MBS session, specifically, to maintain the service continuity when switching between 5G MBS delivery and unicast delivery.
14.3.4A.9.2  Service continuity for broadcast MBS session  p. 274
14.3.4A.9.2.1  General  p. 274
This solution provides the procedure which allows the NRM client to report the broadcast reception quality to the NRM server which is used to make the decision whether to use the unicast delivery to the VAL UE(s) which are suffering bad broadcast reception quality due to e.g., move out of the broadcast service area.
An NRM client monitors the broadcast MBS session to receive VAL data. Based on the received quality (e.g., radio level quality, RTP packet loss), the NRM client needs to inform the NRM server that the NRM client is able to receive the VAL data on the broadcast MBS session with sufficient quality or not.
This estimation of the broadcast reception quality may be dependent on, for example, the modulation and coding scheme (MCS) and measurements from the reference signals from the NG-RAN node(s), RTP packet loss, BLER of the received VAL data.
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14.3.4A.9.2.2  Procedures  p. 274
14.3.4A.9.2.2.1  Service continuity from broadcast to unicast  p. 274
The procedure in Figure 14.3.4A.9.2.2.1-1 illustrates the VAL UE which is receiving VAL data via broadcast MBS session is switched to unicast delivery because the VAL UE suffers from bad broadcast reception quality due to e.g., moving out of the broadcast service area. It shows only one of the receiving VAL UEs receiving the broadcast MBS session.
Pre-conditions:
  1. The VAL group communication is ongoing and the VAL data (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session.
  2. The NRM client is receiving the VAL data (e.g., DL media, application layer control signalling) via the broadcast MBS session.
  3. The NRM client(s) already have the associated information (e.g., SDP) to receive the unicast delivery during the group communication establishment phase.
  4. An VAL group communication session is ongoing and the DL VAL data is transmitted over broadcast MBS session.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.9.2.2.1-1: Service continuity from broadcast to unicast
Figure 14.3.4A.9.2.2.1-1: Service continuity from broadcast to unicast
Up
Step 1.
The NRM client detects that it suffers bad broadcast reception due to e.g., moving out of the broadcast service area of the announced MBS session ID. The NRM client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
Step 2.
The NRM client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is not sufficient to receive media. The NRM client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the VAL data has been received.
Step 3.
The NRM server based on the report from the participant, determines that the UE is not able to receive the media or the QoS requirements is not satisfied. The NRM server determines the VAL media (e.g., DL media, application layer control signalling) needs to be delivered via the unicast delivery to the reported NRM client.
Step 4.
If the unicast QoS flow is not satisfied, the NRM server interacts with the 5GC to update the QoS requirements.
Step 5.
The NRM server informs the VAL server to send the VAL data via the unicast delivery towards the reported NRM client by sending a user plane delivery mode message.
Step 6.
The NRM server sends the VAL media via the unicast delivery towards the NRM client which suffers bad broadcast reception quality.
Step 7.
The NRM client then receives the DL VAL data via both broadcast MBS session and unicast delivery.
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14.3.4A.9.2.2.2  Service continuity from unicast to broadcast  p. 276
The procedure in Figure 14.3.4A.9.2.2.2-1 illustrates the VAL UE receiving VAL data via unicast delivery being switched to broadcast MBS session as the UE enters the broadcast service area where the NG-RAN is broadcasting the VAL media of the ongoing group communication. The VAL UE now is able to receive the VAL data via the broadcast MBS session. Only one of the receiving VAL UEs receiving the broadcast MBS session is shown.
Pre-conditions:
  1. The VAL group communication is ongoing and the VAL data (e.g., DL media, application layer control signalling) is transmitted via broadcast MBS session in the broadcast service areas.
  2. The VAL UE is receiving the VAL data (e.g., DL media, application layer control signalling) via the unicast delivery.
  3. The NRM client has already received the broadcast MBS session announcement, MapVALGroupToSessionStream information and enters the broadcast service area.
  4. A VAL group communication session is ongoing and the broadcast MBS session is used by the VAL server to deliver the VAL data of the group communication. The VAL UE is receiving the VAL data via the unicast delivery.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.9.2.2.2-1: Service continuity from unicast to broadcast
Figure 14.3.4A.9.2.2.2-1: Service continuity from unicast to broadcast
Up
Step 1.
The NRM client detects that it is able to receive the broadcast media due to e.g., moving into the broadcast service area of the announced MBS session ID. The NRM client may determine the broadcast reception quality by using the BLER of the received media. When no media is received, the quality estimation can consider the reference signals and the modulation and coding scheme (MCS).
Step 2.
The NRM client sends MBS listening status report which indicates the broadcast reception quality associated with the MBS session ID is sufficient to receive VAL data. The NRM client may also map the determined broadcast reception quality to a broadcast reception quality level. The broadcast reception quality level indicates at which specific broadcast reception quality level the VAL data has been received.
Step 3.
The NRM server determines the VAL UE is able to receive the VAL data via the the broadcast MBS session, and the NRM server sends a user plane delivery mode to the VAL server indicating to stop the unicast delivery.
Step 4.
Based on the MapVALGroupToSessionStream received before, the NRM client receives the DL VAL data via both the broadcast MBS session and the unicast delivery.
Step 5.
The VAL server, based on the user plane delivery mode message, determines to stop sending the VAL data (e.g., DL media, application layer control signalling) via the unicast delivery to the reporting NRM client. After then, the NRM client receives the VAL data only via the broadcast MBS session.
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14.3.4A.9.3  Service continuity for multicast MBS session  p. 277
14.3.4A.9.3.1  General  p. 277
The NRM server may also switch between multicast and unicast by utilizing application layer mechanisms similar to switching between broadcast and unicast as specified in clause 14.3.4A.9.2. If indicated in the MBS session announcement information, the NRM client reports the monitoring state (i.e., the reception quality of the MBS session) back to the NRM server.
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14.3.4A.10  VAL service inter-system switching between 5G and LTE  p. 277

14.3.4A.10.1  General  p. 277
The VAL server delivers the VAL data to the VAL UE(s) without being aware of the mobility of the VAL UE with the assistance and guidance of the NRM server. When working in transport only mode, the NRM server guides the NRM clients throughout the VAL data transmission for switching between the LTE and 5G systems. For this purpose, the location management client may send location related information to the location management server, similar to the one defined in clause 9, which is triggered due to its location change - in this case due to Radio Access Technology (RAT) change, to inform the NRM server hence the latter provides guidance related to how to receive the VAL data after the location update.
The procedures cover both the deployment scenarios with/without MBSF/MBSTF. The procedures specify four inter-system switching related scenarios as follows:
  1. Inter-system switching from 5G MBS session to LTE eMBMS bearer, as in clause 14.3.4A.10.2
  2. Inter-system switching from 5G MBS session to LTE unicast bearer, as in clause 14.3.4A.10.3
  3. Inter-system switching from LTE eMBMS to 5G MBS session, as in clause 14.3.4A.10.4
  4. Inter-system switching from LTE eMBMS to 5G unicast PDU session, as in clause 14.3.4A.10.5
In all the inter-system switching related scenario described in clause 14.3.4A.10.2, clause 14.3.4A.10.3, clause 14.3.4A.10.4 and clause 14.3.4A.10.5, the functional entity that resides in 5GS may be NEF, or MBSF, or MB-SMF for session creation and together with PCF or PCC related interaction.
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14.3.4A.10.2  Inter-system switching from 5G MBS session to LTE eMBMS bearer  p. 278
The procedure provided in Figure 14.3.4A.10.2-1 describes how the NRM server handles inter-system switching when the VAL UE switches from 5G to LTE network, where the NRM server is able to provide the VAL data to the clients over eMBMS bearer(s).
Pre-conditions:
  • NRM clients are attached to the 5GS, registered.
  • The VAL service can be provided via both 5GS and EPS.
  • The NRM client(s) is within the eMBMS service area.
  • It is assumed that the NRM client(s) has not received the eMBMS bearer announcement while camping in 5GS.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.10.2-1: Inter-system switching from 5G MBS session to LTE eMBMS bearer
Figure 14.3.4A.10.2-1: Inter-system switching from 5G MBS session to LTE eMBMS bearer
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Step 1.
An VAL group communication takes place, and the VAL data is delivered over 5G MBS session (either broadcast or multicast session mode), which is associated to the VAL group X.
Step 2.
The VAL UE performs handover to EPS.
Step 3.
Location information indicating the RAT change from the VAL UE is provided to the NRM server. VAL UE's location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the NRM server. Also, location information handling can be based on notifications provided from the network to the NRM server related to 5GS supporting EPS interworking, as specified in TS 23.501, TS 23.502, and TS 23.503. For that, the NRM server can subscribe to receive notifications of specific events from the network. For instance, the NRM server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g., access network information notification and change of access type. Also, when SCEF+NEF is deployed, the NRM server can subscribe to SCEF+NEF related notifications for specific events, e.g., core network (CN) type change.
Step 4.
The NRM server analyses the RAT change and decides how to deliver the DL VAL data. If the NRM server decides to serve the client via eMBMS bearer, it may send an eMBMS bearer announcement. This step is optional as the bearer announcement related information could be sent in advance (implementation specific).
Step 5.
If not already available, the NRM client stores the announced TMGI(s), service area, and any relevant information to the eMBMS, which is delivered via the bearer announcement. As a result, the NRM client starts monitoring the bearer.
Step 6.
The NRM server may inform the VAL server to stop sending DL VAL data via the MBS by sending the user plane delivery mode message, e.g., when the last UE leaves the MBS session or move out of the MBS service area.
Step 7.
The NRM client sends an eMBMS listening status report to inform the server of its ability of receiving DL VAK data over the specified bearer.
Step 8.
The NRM server sends the necessary information related to receiving the DL VAL data in the form of the MapGroupToBearer.
Step 9.
The NRM server may inform the VAL server to start sending DL VAL data via the eMBMS by sending the user plane delivery mode message, e.g., the first UE(s) enters the eMBMS service area.
Step 10.
The VAL group communication takes place over EPS, and the VAL data is transmitted over an eMBMS bearer.
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14.3.4A.10.3  Inter-system switching from 5G MBS session to LTE unicast bearer  p. 279
The procedure provided in Figure 14.3.4A.10.3-1 describes how the NRM server handles inter-system switching when the VAL UE switches from 5G to LTE network, where the VAL server is unable to provide the VAL services to the VAL UE over eMBMS bearer.
Pre-conditions:
  • NRM clients are attached to the 5GS, registered and affiliated to the same VAL group X.
  • The VAL services can be provided via both 5GS and EPS.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.10.3-1: Inter-system switching from 5G MBS session to LTE unicast bearer
Figure 14.3.4A.10.3-1: Inter-system switching from 5G MBS session to LTE unicast bearer
Up
Step 1.
An VAL group communication takes place, and the VAL data is delivered over 5G MBS session (either broadcast or multicast session mode), which is associated to the VAL group X.
Step 2.
The VAL UE performs handover to EPS.
Step 3.
Location information indicating the RAT change from the VAL UE is provided to the NRM server. VAL UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the NRM server.
Also, location information handling can be based on notifications provided from the network to the NRM server related to 5GS supporting EPS interworking, as specified in TS 23.501, TS 23.502, and TS 23.503. For that, the NRM server can subscribe to receive notifications of specific events from the network. For instance, the NRM server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. Also, when SCEF+NEF is deployed, the NRM server can subscribe to SCEF+NEF related notifications for specific events, e.g. core network (CN) type change.
Step 4.
The NRM server may inform the VAL server to stop sending DL VAL data via the MBS by sending the user plane delivery mode message, e.g., when the last UE leaves the MBS session or move out of the MBS service area.
Step 5.
The NRM server may interact with the EPC for providing the required media resources over the unicast bearer, if not already allocated.
Step 6.
The NRM server informs the VAL server to send DL VAL data to the VAL UE via the LTE unicast bearer by sending the user plane delivery mode message.
Step 7.
The VAL group communication takes place over EPS, and the DL VAL data is transmitted over a LTE unicast bearer.
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14.3.4A.10.4  Inter-system switching from LTE eMBMS to 5G MBS session  p. 281
The procedure provided in Figure 14.3.4A.10.4-1 describes how the NRM server handles inter-system switching when the VAL UE switches from LTE network to 5G, where the NRM server is able to provide the VAL services to the client over 5G MBS sessions (either broadcast or multicast).
Pre-conditions:
  • NRM clients are attached to the EPC.
  • The VAL services can be provided via both 5GS and EPS.
  • The NRM client(s) is within the service area (if the session is limited to an area), where the MBS session is configured.
  • It is assumed that the NRM client(s) has not received the 5G MBS session announcement while camping in EPS.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.10.4-1: Inter-system switching from LTE eMBMS bearer to 5G MBS sessions (either broadcast or multicast)
Figure 14.3.4A.10.4-1: Inter-system switching from LTE eMBMS bearer to 5G MBS sessions (either broadcast or multicast)
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Step 1.
An VAL group communication takes place, and the DL VAL data is delivered over eMBMS bearer, which is associated to the VAL group X.
Step 2.
The VAL UE performs handover to 5GS.
Step 3.
Location information indicating the RAT change from the VAL UE is provided to the NRM server. VAL UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the NRM server.
Also, location information handling can be based on notifications provided from the network to the NRM server related to 5GS supporting EPS interworking, as specified in TS 23.501, TS 23.502, and TS 23.503. For that, the NRM server can subscribe to receive notifications of specific events from the network. For instance, the NRM server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g., access network information notification and change of access type. Also, when SCEF+NEF is deployed, the NRM server can subscribe to SCEF+NEF related notifications for specific events, e.g., core network (CN) type change.
Step 4.
The NRM server analyses the RAT change and decides how to deliver the DL VAL data. If the NRM server decides to serve the client via 5G MBS session, it may send an MBS session announcement indicating information among others the session mode to serve the NRM client and the corresponding MBS session ID. This step is optional as the session announcement related information could be sent in advance (implementation specific).
Step 5.
The VAL UE acts according to the MBS session mode provided to receive the DL media.
Step 5a.
In case of multicast MBS sessions, the VAL UE performs a UE session join towards the 5GC indicating the MBS session ID to join. It may as well send a UE session join acknowledgement to the NRM server.
Step 5b.
In case of broadcast MBS sessions, the VAL UE starts monitoring the broadcast MBS session.
Step 6.
The NRM server may inform the VAL server to stop sending DL VAL data via the eMBMS bearer by sending the user plane delivery mode message, e.g., when the last UE moves out of the MBMS service area.
Step 7.
The NRM client sends an MBS listening status report to the server indicating its ability to receive media over the indicated MBS session.
Step 8.
The NRM server sends a MapVALGroupToSessionStream over the MBS session providing the required stream information to receive the media related to the group communication.
Step 9.
The NRM client processes the received information related to the DL VAL data over the MBS session.
Step 10.
The NRM server may inform the VAL server to start sending DL VAL data via the 5G MBS session by sending the user plane delivery mode message, e.g., the first UE(s) enters the MBS service area or joins the multicast MBS session.
Step 11.
The VAL group communication takes place over 5GS, and the DL VAL data is delivered over the broadcast or multicast MBS session.
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14.3.4A.10.5  Inter-system switching from LTE eMBMS to 5G unicast PDU session  p. 281
The procedure provided in Figure 14.3.4A.10.5-1 describes how the NRM server handles inter-system switching when the VAL UE switches from LTE network to 5G, where the NRM server is able to provide the VAL services to the client over 5G MBS sessions (either broadcast or multicast).
Pre-conditions:
  • NRM clients are attached to the EPC and affiliated to the same VAL group X.
  • The VAL services can be provided via both 5GS and EPS.
Reproduction of 3GPP TS 23.434, Fig. 14.3.4A.10.5-1: Inter-system switching from LTE eMBMS bearer to 5G unicast PDU session.
Figure 14.3.4A.10.5-1: Inter-system switching from LTE eMBMS bearer to 5G unicast PDU session.
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Step 1.
An VAL group communication takes place, and the VAL data is delivered over eMBMS bearer, which is associated to the VAL group X.
Step 2.
The VAL UE performs handover to 5GS.
Step 3.
Location information indicating the RAT change from the VAL UE is provided to the NRM server. VAL UE`s location information is provided via the location management client, triggered by RAT change, to the location management server, where the latter provides the location information to the NRM server.
Also, location information handling can be based on notifications provided from the network to the NRM server related to 5GS supporting EPS interworking, as specified in TS 23.501, TS 23.502, and TS 23.503. For that, the NRM server can subscribe to receive notifications of specific events from the network. For instance, the NRM server can subscribe to PCF related notifications (via N5 or Rx) for specific events, e.g. access network information notification and change of access type. Also, when SCEF+NEF is deployed, the NRM server can subscribe to SCEF+NEF related notifications for specific events, e.g. core network (CN) type change.
Step 4.
The NRM server may inform the VAL server to stop sending DL VAL data via the eMBMS bearer by sending the user plane delivery mode message, e.g., when the last UE moves out of the LTE MBMS service area.
Step 5.
The NRM server may interact with the 5GC to request media resources (if not already allocated) with specific requirements over unicast PDU session, as it is able to serve the NRM client via unicast PDU session.
Step 6.
The NRM server informs the VAL server to send DL VAL data to the VAL UE via the PDU session by sending the user plane delivery mode message.
Step 7.
The VAL group communication takes place over 5GS, and the VAL data is delivered over unicast PDU session.
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