Content for &nbsp; TS 23.280 &nbsp; Word version:&nbsp; 19.4.0

The MC service client requests de-affiliation from MC service groups. The MC service groups are either defined in the primary MC system (see clause 10.8.4.2) or the partner MC system (see clause 10.8.4.3).

After migration to the partner MC system, the configuration management client triggers retrieval of the MC service user profile used within the partner MC system (see clause 10.1.4.3.2).

The MC service client requests affiliation to MC service groups. The MCPTT groups are either defined in the primary MC system (see clause 10.8.3.1) or the partner MC system (see clause 10.8.3.2 or clause 10.8.3.2a).

Table 10.16.3.2.1-1: MC service functional alias resolution request information elements

If any of the received group calls are ongoing in the partner MC system, the partner MC system shall initiate a late-entry procedure towards the MC service client. If any of the received group calls are taken place in the primary MC system but not yet in the partner MC system, the affiliation by the migrated MC service UE triggers the late-entry procedure which then includes the MC service UE and the partner MC system into the group call.

The MC service client may indicate the successful migration of group communications to the MC service user.

10.16.2.3 Void

10.16.2.3.1 Void

10.16.3 Private call using functional alias towards a partner MC system p. 308

10.16.3.1 General p. 308

This provides the possibility for an MC service user to initiate a private MC service call using a functional alias, defined in the partner MC system, as target address towards an MC service user in a partner MC system.

10.16.3.2 Information flows p. 308

10.16.3.2.1 MC service functional alias resolution request p. 308

Table 10.16.3.2.1-1 describes the information flow MC service functional alias resolution request from the MC service server to the MC service functional alias controlling server and from the MC service functional alias controlling server to another MC service functional alias controlling server.

Information element	Status	Description
MC service ID	M	The MC service ID of the calling party
Functional alias	O	The functional alias of the calling party
Functional alias	M	The functional alias of the called party

10.16.3.2.2 MC service functional alias resolution response p. 309

Table 10.16.3.2.2-1 describes the information flow MC service functional alias resolution response from the MC service functional alias controlling server to another MC service functional alias controlling server, the MC service functional alias controlling server to the MC service server and the MC service server to the MC service client.

Table 10.16.3.2.2-1: MC service functional alias resolution response information elements

Information element	Status	Description
MC service ID	M	The MC service ID of the calling party
MC service ID	M	The corresponding MC service ID of the called functional alias. Return "NONE" if no one activates the targeted Functional Alias.

10.16.3.3 Procedure p. 309

Figure 10.16.3.3-1 represents a generic MC service private call setup procedure to allow using the functional alias as called party address, i.e., the MC service ID address is resolved by the partner MC system through the primary MC service server and primary MC service functional alias controlling server.

Additional new pre-condition:

A secured connection has been established between the MC service functional alias controlling servers in different MC systems.

Reproduction of 3GPP TS 23.280, Fig. 10.16.3.3-1: Private call setup in automatic commencement mode, users in multiple MC systems

Figure 10.16.3.3-1: Private call setup in automatic commencement mode, users in multiple MC systems

Step 1-2.

Same as in clause 10.7.2.2.3.1 of TS 23.379, clause 7.2.2.3.1 of TS 23.281 or corresponding procedures in TS 23.282, but MC service private call request contains a functional alias of invited user.

If the MC service private call request contains a functional alias instead of an MC service ID as called party, the MC service server checks whether MC service client 1 can use the functional alias to setup a private call. If authorized, the MC service server 1 resolves the functional alias to the corresponding MC service ID for which the functional alias is active by using subsequent steps 4-7.

The MC service server 1 sends an MC service functional alias resolution request message to the MC service functional alias controlling server 1 to resolve the functional alias of the called party.

The MC service functional alias controlling server 1 determines that the functional alias belongs to the partner MC system and forwards the MC service functional alias resolution request message to MC service functional alias controlling server 2.

The MC service functional alias controlling server 2 resolves the functional alias and determines the corresponding MC service ID to terminate the call and returns it to the MC service functional alias controlling server 1 in the MC service functional alias resolution response message.

Step 7.

The MC service functional alias controlling server 1 returns the corresponding MC service ID to MC service server 1 in the MC service functional alias resolution response message. The MC service server 1 checks if MC service user at MC service client 1 is authorized to initiate the private call to the MC service user at MC service client 2. If not authorized stop the procedure, otherwise continue with step 8.

The MC service server 1 responds with a MC service functional alias resolution response message that contains the resolved MC service ID back to MC service client 1.

Figure 10.16.4.2-1: Migration during ongoing private communication

The MC service client 1 sends a new MC service private call request towards the resolved MC service ID according to clause 10.7.2.2.3.1 of TS 23.379, clause 7.2.2.3.1 of TS 23.281 or corresponding procedures in TS 23.282.

Step 10-14.

Same as in clause 10.7.2.2.3.1 of TS 23.379, clause 7.2.2.3.1 of TS 23.281 or clause 7.14.2.2 of TS 23.282.

Step 15.

The receiving MC service client 2 accepts the private call automatically, and an acknowledgement is sent to the MC service server 2.

Step 16.

The MC service server 2 forwards the MC service private call response message to MC service server 1.

Step 17-18.

Same as in clause 10.7.2.2.3.1 of TS 23.379, clause 7.2.2.3.1 of TS 23.281 or corresponding procedures in TS 23.282.

10.16.4 Migration during an onging private communication p. 311

10.16.4.1 General p. 311

This subclause provides a generic guidance on the behaviour an MC service client follows to perform migration during an ongoing private communication, e.g., MCPTT private call. Once the MC service client detects the need to migrate during an ongoing private communication, it may initiate preparations and UE configuration which facilitate migration as mentioned in clause 10.1.1.2. The described procedure is applicable to the scenarios whether an MC service client is migrating into its primary MC system or a partner MC system.

10.16.4.2 Procedure p. 311

Figure 10.16.4.2-1 represents a generic procedure to be followed when migration is needed to be done during an ongoing private communication, such as MCPTT private call, or MCVideo private call.

Reproduction of 3GPP TS 23.280, Fig. 10.16.4.2-1: Migration during ongoing private communication

A private call takes place between MC service client 1 and MC service client 2, where the former is connected to MC system A and the latter to MC system B.

The MC service client 1 detects the need to migration into MC system C and MC service server 1 is notified to be prepared for possible service interruption. Furthermore, upon detection, MC service client 1 performs initial steps to be considered prior migration, e.g., UE configuration, authorization, and selection of user profile that permits migration, as described in clause 10.1.1.2

MC service client 1 releases the private communication towards the MC service client 2 as described in clause 10.7.2.2.3.1 of TS 23.379 for MCPTT private call, or in clause 7.2.2.3.3.1 of TS 23.281 for MCVideo private call. A call release reason IE "release due to migration" may be included so that MC service client 2 is informed.

Migration takes place and MC system C retrieves MC service client 1 profile:

Step 4a.

if MC system C is the primary MC system, retrieval of MC service client 1 profile takes place according to clause 10.1.4.3.1.

Step 4b.

if MC system C is a partner MC system, retrieval of MC service client 1 profile takes place according to clause 10.1.4.3.2.

Registration according to procedure in clause 10.6.1 takes place.

Table 10.16.5.2-1: Private call redirection

MC service client 1 initiates a new private communication toward MC service client 2 as described in clause 10.7.2.2.1 of TS 23.379 for MCPTT private call, or in clause 7.2.2.3.1 of TS 23.281 for MCVideo private call.

10.16.5 Generic private call procedure towards a migrated MC service user p. 313

10.16.5.1 General p. 313

This subclause describes a generic private communication procedure towards a migrated MC service user at a partner MC system. This generic private communication can be an MCPTT private call, an MCVideo private call, or a one-to-one MCData communication. For the generic private call, this procedure is used in conjunction with the corresponding MCPTT, MCVideo and MCData procedures described in TS 23.379, TS 23.281, or TS 23.282, respectively.

Once an MC service user is migrated, he or she will be assigned a new MC service ID by the migrated MC system and this MC service ID will be used for all his/her communications. When another MC service user communicates with the migrated MC service user using the newly assigned MC service ID, the private call request described in clause 10.7.2.1.1 of TS 23.379, in clause 7.2.2.2.1 of TS 23.281, or the corresponding procedures in TS 23.282 applies.

For callers that are not aware of the migrated MC service user`s new MC service ID, the migrated MC service user is also reachable by his/her MC service ID assigned by the primary MC system via redirection done by the primary MC system`s MC service server described in this procedure.

10.16.5.2 Private call redirection p. 313

Table 10.16.5.2-1 describes the information flow of a private call redirection, which is sent from the MC service server to an MC service client initiating a private call towards a migrated MC service user.

Information element	Status	Description
MC service ID	M	The MC service ID of the MC service user initiating a private call, i.e., calling party. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user (i.e., called party), which the MC service user has obtained from its primary MC system before migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user, which the MC service user has obtained from its migrated MC system after Migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
KMS URI (NOTE)	O	The KMS URI associated with the MC service ID of the migrated MC service user.
Redirection reason	O	The MC service server informs the calling party that the target MC service user has migrated.
NOTE: If the KMS URI is not configured in the MC service user profile and is not included in the private call redirection message, then the MC service client shall obtain KMS URI using the KMS lookup procedure defined in TS 33.180.

10.16.5.3 Procedure p. 313

Figure 10.16.5.3-1 presents a generic private communication procedure from MC service user 1 towards a migrated MC service user 2 where the MC system A is the primary MC system of MC service user 2 before migration, and the MC system B is the MC system that the MC service user 2 has migrated

Pre-conditions:

MC system A and MC system B are interconnected.
MC system A is the primary MC system of MC service user 2 before migration. MC system B is the MC system that MC service user 2 has migrated.
The MC service server A is aware that MC service user 2 has migrated and is informed of its MC service ID provided by MC system B, as described in clause 10.6.3.3.

Reproduction of 3GPP TS 23.280, Fig. 10.16.5.3-1: MC private call towards a migrated MC service user

Figure 10.16.5.3-1: MC private call towards a migrated MC service user

The MC service client 1 initiates a private call request towards MC service user 2 (MC service client 2) who has migrated to MC system B. The private call request includes among others the MC service ID of MC service user 2, which is provided by its primary MC system, as the target, i.e., called party. The private call request is described in clause 10.7.2.1.1 in TS 23.379, in clause 7.2.2.2.1 in TS 23.281, or the corresponding procedures in TS 23.282.

If the private call request contains a functional alias instead of an MC service ID as the target party, the MC service server A checks whether the MC service user 1 at the MC service client 1 is allowed to use functional alias during private call setup.

MC service server A checks that MC service user 2 has migrated to MC system B with a new MC service ID assigned by MC system B.

If the private call request contains a functional alias, and if the MC service user 1 at the MC service client 1 is authorized, the MC service server A resolves the functional alias to a corresponding MC service ID of the MC service user which has activated the functional alias. If the MC service server A determines that the corresponding MC service user of the resolved MC service ID is migrated, i.e., MC service user 2 at MC service client 2 is migrated, it checks whether the resolved MC service ID of the MC service user 2 is allowed to receive a private call from the MC service ID of the MC service user 1 using functional alias based on entries in the user profile of the MC service user 2 assigned by the primary system.

The MC service server A sends a private call redirection towards the MC service client 1, to inform MC service user 1 that the target MC service user, i.e., MC service user 2 has migrated and its new MC service ID of MC service user 2 assigned by the migrated MC system. The MC service client 1 releases the private call request at step 1.

Table 10.16.6.2.1-1: Ad hoc group call redirection notify

The MC service client 1 initiates a private call towards MC service user 2, including the MC service ID of MC service user 2 obtained from MC system. The initiated private call can either be an MCPTT private call, an MCVideo private call, or a corresponding one-to-one MCData communication, and shall perform the procedures as described in TS 23.379, TS 23.281, or TS 23.282, respectively.

10.16.6 Ad hoc group call procedure towards a migrated MC service user |R19| p. 315

10.16.6.1 General p. 315

The following clauses specify the generic procedure for ad hoc group call towards a migrated MC service user that is utilised by all the MC services (i.e. MCPTT, MCVideo and MCData) in conjunction with the procedures as specified in the respective MC services in TS 23.379, TS 23.281, and TS 23.282.

The ad hoc group calls can be initiated by using the participant list provided by an initiator of the call and the ad hoc group call will be hosted in the primary MC system of the initiator of the ad hoc group call. If one of the requested participant is migrated to a partner MC system then the call should be delivered to the partner MC system to which MC service user has migrated. The primary MC system of the migrated MC service user assists in redirecting the call to the partner MC system using partner MC system assigned MC service ID. The initiator of the call is not aware of the migration information of the requested participants, uses an MC service ID assigned by primary MC system of the migrated MC service user. The MC service server of the both primary and partner MC systems are involved in call redirection to deliver a call appropriately into the MC system.

If one of the requested participant is from an interconnected MC system and has migrated to another partner system, then the call should be delivered to the partner MC system to which participant is migrated. The primary MC system of the migrated MC service user assists in redirecting the ad hoc group call setup request by providing the another partner MC system the assigned MC service ID to the MC system where this ad hoc group call is hosted (focus MC service server of the caller's primary MC system). The primary MC system of the migrated MC service user receives the ad hoc group call setup request using the primary MC system assigned MC service ID when an initiator of the call not aware of the migration of the MC service user. The ad hoc group call hosting MC service server of the MC system further delivers the call to the migrated MC service user using another partner MC system assigned MC service ID.

10.16.6.2 Information flows p. 315

10.16.6.2.1 Ad hoc group call redirection notify p. 315

Table 10.16.6.2.1-1 describes the information flow of an ad hoc group call redirection notify, which is sent from the MC service server to MC service server and MC service server to an MC service client initiating an ad hoc group call towards a migrated MC service user.

Information element	Status	Description
MC service ID	M	The MC service ID of the MC service user initiating an ad hoc group call, i.e., calling party. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user (i.e., called party), which the MC service user has obtained from its primary MC system before migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user, which the MC service user has obtained from its migrated MC system after Migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
Redirection reason	O	The called MC service user has migrated.

10.16.6.3 Procedure p. 315

Figure 10.16.6.3-1 presents a generic ad hoc group call procedure for the MC service user 1 using MC service client 1 towards a MC service user 2 using MC service client 2, a migrated MC service user 3 using MC service client 3 and a migrated MC service user 4 using MC service client 4, where the MC system A is the primary MC system of MC service user 3 before migration, MC system B is the primary MC system of MC service user 4 before migration, the MC system B is the MC system that the MC service user 3 has migrated and the MC system C is the MC system that the MC service user 4 has migrated.

The procedure is based on the following existing procedures:

The ad hoc group call setup procedures as described in clause 10.19.3.2.1 of TS 23.379, in clause 7.19.3.2.1 of TS 23.281, or in clause 7.17.3.2.1 of TS 23.282.

Pre-conditions:

The MC system A, MC system B and MC system C are interconnected MC systems.
The MC system A is the primary MC system of MC service user 1, MC service user 2 and the MC service user 3 The MC system B is the MC system that MC service user 3 has migrated.
The MC system B is the primary MC system of MC service user 4. The MC system C is the MC system that MC service user 4 has migrated.
The MC service server A is aware that MC service user 3 has migrated and is informed of its MC service ID provided by MC system B, as described in clause 10.6.3.3.
The MC service server B is aware that MC service user 4 has migrated and is informed of its MC service ID provided by MC system C, as described in clause 10.6.3.3.
The authorized MC service user 1 at MC service client 1 wants to invite MC service users at MC service client 2, MC service client 3 and MC service client 4 for the ad hoc group call.
The ad hoc group call is hosted in the MC service server A of the MC system A.

Reproduction of 3GPP TS 23.280, Fig. 10.16.6.3-1: Ad hoc group call towards migrated MC service users

Figure 10.16.6.3-1: Ad hoc group call towards migrated MC service users

The MC service user 1 (at MC service client 1) initiates an ad hoc group call request towards MC service user 2 (at MC service client 2), MC service user 3 (at MC service client 3) who has migrated to MC system B, and MC service user 4 (at MC service client 4) who has migrated to MC system C. The initiator of the ad hoc group call includes the MC service ID of MC service users in an ad hoc group call request, which are obtained from their primary MC system.

The MC service server A of the MC system A invites the MC service client 2 to ad hoc group call and successfully establishes the ad hoc group call with the MC service client 2.

The MC service server A determine that MC service user 3 which has to be invited for ad hoc group call is migrated to MC system B with a new MC service ID assigned by MC system B.

The MC service server A may inform the MC service client 1 that ad hoc group call request towards MC service user 3 is redirected to MC system B (migrated MC system) by sending ad hoc group call redirection notify. The ad hoc group call redirection notify contains the information about MC service ID of the target MC service user 3 assigned by both MC system A and MC system B, and reason for the call redirection as user migration.

The MC service server A of the MC system A invites the MC service client 3 to ad hoc group call using MC service ID assigned by the MC system B and successfully establishes the ad hoc group call with the MC service client 3.

The MC service server A of the MC system A further initiates an ad hoc group call request towards the MC service client 4 of the MC system B. The ad hoc group call request is routed to the MC service client 4 via the MC service server B of the MC system B.

Step 7.

The MC service server B of the MC system B determine that MC service user 3 has to be invited for ad hoc group call is migrated to MC system C with a new MC service ID assigned by MC system C.

The MC service server B inform the MC service server A that initiation of ad hoc group call towards the MC service user 4 has migrated and assigned with a new MC service ID by MC system C (migrated MC system) by sending ad hoc group call redirection notify. The ad hoc group call redirection notify contains the information about MC service ID of the target MC service user 4 assigned by both MC system B and MC system C, and reason for the call redirection notify as user migration.

Table 10.16.7.2.1-1: Ad hoc group call redirection notify

The MC service server A may inform the MC service client 1 that ad hoc group call request towards MC service user 4 is redirected to MC system C (migrated MC system) by sending ad hoc group call redirection notify. The ad hoc group call redirection notify contains the information about MC service ID of the target MC service user 4 assigned by both MC system B and MC system C, and reason for the call redirection as user migration.

Step 10.

The MC service server A of the MC system A invites the MC service client 4 to ad hoc group call using MC service ID assigned by the MC system C and successfully establishes the ad hoc group call with the MC service client 4.

Step 11.

The MC service server A of the MC system A provides an ad hoc group call response to the MC service client 1 upon receiving response to the corresponding ad hoc group call request in step 1. The ad hoc group call response will consist of the success or failure result and/or detailed reason information in case of failure.

Step 12.

Upon successful of an ad hoc group call setup, call is established amongst the multiple group members from MC system A, MC system B and MC system C. The media plane and floor control resources are established.

10.16.7 Migration during Ad hoc group call procedure |R19| p. 318

10.16.7.1 General p. 318

The following clauses specify the generic procedure for MC service user to continue to participate in ad hoc group call when migrated to partner system that is utilised by all the MC services (i.e. MCPTT, MCVideo and MCData) in conjunction with the procedures as specified in the respective MC services in TS 23.379, TS 23.281, and TS 23.282.

The ad hoc group call can be initiated by using the participant list or criteria (along with criteria or local policies at MC service server) provided by an initiator of the call and the ad hoc group call will be hosted in the primary MC system of the initiator of the ad hoc group call. During ongoing call, the participating MC service user can migrate to partner MC system. While migrating to partner MC system, the MC service user will leave the ongoing ad hoc group call by providing the reason for leaving the ad hoc group call is due to migration. After succesful migration, the MC service user will be invited again to continue the participation in an ongoing ad hoc group call. If the ad hoc group call is established using the participant list provided by the initiator of the call, then the MC service server where the ad hoc group call is hosted will invite the migrated MC service user using partner MC system assigned MC service ID. If the ad hoc group call is established using the criteria provided by the initiator of the call, then the MC service server where the ad hoc group call is hosted will invite the migrated MC service user using partner MC system assigned MC service ID only when it is informed about the migrated MC service user meeting the criteria and to be invited for ongoing ad hoc group call by partner MC system (migrated MC system).

10.16.7.2 Information flows p. 318

10.16.7.2.1 Ad hoc group call redirection notify p. 318

Table 10.16.7.2.1-1 describes the information flow of an ad hoc group call redirection notify, which is sent from the MC service server to MC service server and MC service server to an MC service client initiating an ad hoc group call towards a migrated MC service user.

Information element	Status	Description
MC service ID	M	The MC service ID of the MC service user initiating an ad hoc group call, i.e., calling party. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user (i.e., called party), which the MC service user has obtained from its primary MC system before migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
MC service ID	M	The MC service ID of the target MC service user, which the MC service user has obtained from its migrated MC system after Migration. The MC service ID can either be MCPTT ID, MCVideo ID, or MCData ID.
Redirection reason	O	The called MC service user has migrated.

10.16.7.3 Procedure for participants list provided by the Initiator p. 319

Figure 10.16.7.3-1 presents a generic ad hoc group call procedure in which MC service user 3 using MC service client 3 and MC service user 4 using MC service client 4 migrates during the call, where the MC system A is the primary MC system of MC service user 3 before migration, MC system B is the primary MC system of MC service user 4 before migration, the MC system B is the MC system that the MC service user 3 has migrated and the MC system C is the MC system that the MC service user 4 has migrated. After the migration, the migrated MC service user 3 and MC service user 4 are re-invited to ongoing ad hoc group call and successfully added to the call.

The procedure is based on the following existing procedures:

The ad hoc group call setup procedures as described in clause 10.19.3.2.1 of TS 23.379, in clause 7.19.3.2.4 of TS 23.281, or in clause 7.17.3.2.1 of TS 23.282.
The migration of the MC service user to the partner MC system procedures as described in clause 10.6.3.
The inviting a MC service user and adding to the ongoing ad hoc group call procedures steps (see steps 6 and 7) are as described in clause 10.19.3.2.1 of TS 23.379, in clause 7.19.3.2.4 of TS 23.281, or in clause 7.17.3.2.1 of TS 23.282.

Pre-conditions:

The MC system A, MC system B and MC system C are interconnected MC systems.
The MC system A is the primary MC system of MC service user 1, MC service user 2 and the MC service user 3. The MC system B is the MC system that MC service user 3 has migrated.
The MC system B is the primary MC system of MC service user 4. The MC system C is the MC system that MC service user 4 has migrated.
An ad hoc group call is ongoing among the MC service users at MC service client 1 (initiator), MC service client 2, MC service client 3 and MC service client 4 using the MC service ID which are obtained from their primary MC system, and the participants list provided by the originating MC service user while initiating the ad hoc group call.
The ad hoc group call is hosted in the MC service server A of the MC system A.

Reproduction of 3GPP TS 23.280, Fig. 10.16.7.3-1: Migration during ongoing ad hoc group call based on participants list

Figure 10.16.7.3-1: Migration during ongoing ad hoc group call based on participants list

The MC service client 3 determines the need to migrate to the MC system B and MC service user 3 is notified to be prepared for possible service interruption.

Step 2a-2b.

The MC service client 3 leaves the ad hoc group call by sending ad hoc group call leave request towards the MC service server A containing the ad hoc group ID and reason for the leaving the call as user migration.

The ongoing ad hoc group call is updated by removing MC service client 3 and call continues with remaining MC service clients.

The MC service client 3 migrates to the MC system B as described in the clause 10.6.3 and new MC service ID is assigned by the MC system B. The MC service server A of the MC system A, which is the primary MC system of the migrated MC service user 3, is informed about migrated MC service user's MC service ID obtained from the MC system B (i.e. a migrated MC system) along with successful MC service authorization at the MC system B.

Step 4a.

The MC service server A of the MC system A determines that MC service user 3 has to be re-invited for ongoing ad hoc group call. The MC service server A of the MC system A invites the MC service client 3 to ad hoc group call using MC service ID assigned by the MC system B and successfully establishes the ad hoc group call with the MC service client 3.

The MC service client 4 determines the need to migrate to the MC system C and MC service user 4 is notified to be prepared for possible service interruption.

Step 7a-7b.

The MC service client 4 leaves the ad hoc group call by sending ad hoc group call leave request towards the MC service server A containing the ad hoc group ID and reason for the leaving the call as user migration.

The ongoing ad hoc group call is updated by removing MC service client 4 and call continues with remaining MC service clients.

Figure 10.16.7.4-1: Migration during ongoing ad hoc group call based on criteria

The MC service client 4 migrates to the MC system C as described in the clause 10.6.3 and new MC service ID is assigned by the MC system C. The MC service server B of the MC system B, which is the primary MC system of the migrated MC service user 4, is informed about migrated MC service user's MC service ID obtained from the MC system C (i.e. a migrated MC system) along with successful MC service authorization at the MC system C.

Step 10.

The MC service server A of the MC system A determines that MC service user 4 has to be re-invited for ongoing ad hoc group call. The MC service server A of the MC system A initiates an ad hoc group call request towards the MC service client 4 of the MC system B (i.e. interconnected MC system) using MC service ID assigned by the MC system B (i.e. primary MC system). The ad hoc group call request is routed to the MC service client 4 via the MC service server B of the MC system B.

Step 11.

The MC service server B of the MC system B determines that MC service user 4 has to be invited for ad hoc group call is migrated to MC system C with a new MC service ID assigned by MC system C.

Step 12.

Step 13.

Step 14.

10.16.7.4 Procedure for criteria provided by the Initiator p. 321

Figure 10.16.7.4-1 presents a generic ad hoc group call procedure in which MC service user 3 using MC service client 3 and MC service user 4 using MC service client 4 migrates during the call, where the MC system A is the primary MC system of MC service user 3 before migration, MC system B is the primary MC system of MC service user 4 before migration, the MC system B is the MC system that the MC service user 3 has migrated and the MC system C is the MC system that the MC service user 4 has migrated. After the migration, the migrated MC service user 3 and MC service user 4 are re-invited to ongoing ad hoc group call based on the criteria in the migrated MC system and successfully added to the call.

The procedure is based on the following existing procedures:

The ad hoc group call setup procedures as described in clause 10.19.3.2.3 of TS 23.379, in clause 7.19.3.2.1 of TS 23.281, or in clause 7.17.3.2.3 of TS 23.282.
The migration of the MC service user to the partner MC system procedures as described in clause 10.6.3.
Inviting a MC service user meeting the criteria to the ongoing ad hoc group call procedure steps are as described in clause 10.19.3.2.4 of TS 23.379, in clause 7.19.3.2.2 of TS 23.281, or in clause 7.17.3.2.4 of TS 23.282.

Pre-conditions:

The MC system A, MC system B and MC system C are interconnected MC systems and the criteria is shared among these interconnected systems.
The MC system A is the primary MC system of MC service user 1, MC service user 2 and the MC service user 3. The MC system B is the MC system that MC service user 3 has migrated.
The MC system B is the primary MC system of MC service user 4. The MC system C is the MC system that MC service user 4 has migrated.
An ad hoc group call is ongoing among the MC service users at MC service client 1 (initiator), MC service client 2, MC service client 3 and MC service client 4 using the MC service ID which are obtained from their primary MC system, and the participants list determined using criteria provided by the originating MC service user while initiating the ad hoc group call.
The ad hoc group call is hosted in the MC service server A of the MC system A.

Reproduction of 3GPP TS 23.280, Fig. 10.16.7.4-1: Migration during ongoing ad hoc group call based on criteria

The MC service client 3 determines the need to migrate to the MC system B and MC service user 3 is notified to be prepared for possible service interruption.

Step 2a-2b.

The ongoing ad hoc group call is updated by removing MC service client 3 and call continues with remaining MC service clients.

The MC service server B of the MC system B determines that newly migrated MC service user 3 meets the criteria and notify the MC service server A of the MC system A to add the MC service user 3 to an on-going ad hoc group call. The MC service server A of the MC system A invites the MC service client 3 to ad hoc group call using MC service ID assigned by the MC system B and successfully establishes the ad hoc group call with the MC service client 3.

The MC service client 4 determines the need to migrate to the MC system C and MC service user 4 is notified to be prepared for possible service interruption.

Step 7a-7b.

The ongoing ad hoc group call is updated by removing MC service client 4 and call continues with remaining MC service clients.