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Content for  TS 23.281  Word version:  17.6.0

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7.1.2.3  Group call within one MC system

7.1.2.3.1  Group call models
7.1.2.3.1.1  Pre-arranged group call
7.1.2.3.1.1.1  General
A pre-arranged group call is initiated by one of the affiliated group members. The initiation of a pre-arranged group call results in all other affiliated group members being invited. Media plane resources are reserved (on-demand) or a pre-established session is associated during the group call setup procedure and released (if on-demand session) or de-associated (if pre-established session) when the call is released. SIP signalling is used to setup and release pre-arranged group calls.
7.1.2.3.1.1.2  Pre-arranged group call setup
The procedure enables the scenario where an MCVideo client is initiating an MCVideo group call with unicast signalling for communicating with the affiliated members of that group.
Procedures in Figure 7.1.2.3.1.1.2-1 are the signalling control plane procedures for the MCVideo client initiating establishment of an MCVideo group call with a pre-arranged group i.e., MCVideo users on client 1, client 2 and client 3 belong to the same group which is defined in the group management server.
Pre-conditions:
  1. A pre-arranged group is an MCVideo group that is pre-defined with MCVideo group ID and member list in the group management server. All members of the group belong to the same MC system.
  2. It is assumed that MCVideo users on MCVideo client 1, MCVideo client 2 and MCVideo client 3 are already registered for receiving MCVideo service and affiliated.
  3. The MCVideo client 1 may have an activated functional alias to be used.
  4. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
  5. The MCVideo user on MCVideo client 1 may have bound a functional alias to the MCVideo group ID (TS 23.280).
(not reproduced yet)
Figure 7.1.2.3.1.1.2-1: Pre-arranged group call setup
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Step 1.
User at MCVideo client 1 would like to initiate an MCVideo group call with a selected group (identified by MCVideo group ID). The MCVideo user at MCVideo client 1 may include a functional alias used within the MCVideo group call.
Step 2.
MCVideo client 1 sends a group call request towards the MCVideo server via the SIP core, which hosts the group selected by the user and identified by MCVideo group ID. The group call request also contains the MCVideo group ID and an SDP offer containing the MCVideo client media parameters. If the MC service user of MCVideo client 1 has selected a functional alias, then the group call request contains that functional alias. If there is a transmit media request, then the group call request contains an indication for the implicit transmit media request.
Step 3.
MCVideo server checks whether the user of MCVideo client 1 is authorized to initiate a group call for the selected group. If a functional alias is present, the MCVideo server checks whether it is allowed to be used and if it has been activated for the user. If authorized and the group call is ongoing for that MCVideo group ID, the MCVideo server adds the requesting MCVideo client 1 to the existing MCVideo group call and notifies the MCVideo client 1 that the MCVideo group call is already in progress. Otherwise, MCVideo server resolves the MCVideo group ID to determine the members of that group and their affiliation status, based on the information from the group management server.
If the functional alias is provided only in the group call request, or via binding, the MCVideo server proceeds with the value that is provided. If the functional alias is provided in both the group call request and via binding, it is up to the MCVideo server implementation to determine a value for the functional alias to be used.
Step 4.
MCVideo server includes information that it communicates using MCVideo service, offers the same media parameters or a subset of the media parameters contained in the initial received request and sends the corresponding group call request via the SIP core towards the MCVideo clients of each of those affiliated group members. MCVideo users are notified about the incoming group call and, if present, the functional alias of the initiating MC service user is displayed. The MCVideo server indicates whether acknowledgement is required for the call.
Step 5.
The receiving MCVideo clients accept the group call request, and a group call response is sent to the group host MCVideo server. This response may contain an acknowledgement. The conditions for sending acknowledgement may be based on configuration.
Step 6.
MCVideo server sends the group call response including the selected media parameters to the MCVideo client 1 through the signalling path to inform about successful call establishment.
Step 7.
If the initiating MCVideo user requires the acknowledgement from affiliated MCVideo group members, and the required MCVideo group members do not acknowledge the call setup within a configured time (the "acknowledged call setup timeout"), then the MCVideo server may proceed with or abandon the call and then notify the initiating MCVideo user that the acknowledgements did not include all required members according to group policy. This notification may be sent to the initiating MCVideo user by the MCVideo server more than once during the call when MCVideo users join or leave the MCVideo group call.
Step 8.
MCVideo client 1, client 2 and client 3 have successfully established media plane and transmission control for communication.
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7.1.2.3.1.1.3  Release pre-arranged group callWord‑p. 30
The procedure enables the scenario where an MCVideo server initiates the termination of an ongoing MCVideo group call for all the participants of that group call, since at least one of the termination conditions are met e.g., last participant leaving, second last participant leaving, initiator leaving, or minimum number of affiliated MCVideo group members are not present.
Procedures in Figure 7.1.2.3.1.1.3-1 are the signalling control plane procedures for the MCVideo server initiating termination of an ongoing MCVideo group call.
(not reproduced yet)
Figure 7.1.2.3.1.1.3-1: Release pre-arranged group call
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Step 1.
It is assumed that MCVideo users on MCVideo client 1, client 2 and client 3 are already part of the ongoing group call (e.g., as a result of pre-arranged group call setup).
Step 2.
MCVideo server would like to release the MCVideo group call which is ongoing e.g., last participant leaving, initiator leaving, or minimum number of affiliated group members are not present.
Step 3.
MCVideo server identifies the participants of the ongoing group call and generates group call release request to release ongoing session.
Step 4.
MCVideo server sends a group call release request via SIP core towards each participant of the ongoing group call.
Step 5.
MCVideo users are notified about the release of the group call.
Step 6.
MCVideo client(s) receiving group call release request, acknowledge towards the MCVideo server by sending a group call release response.
Step 7.
MCVideo client 1, client 2 and client 3 have successfully released the media transmission control and media plane resources associated with the group call that is terminated.
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7.1.2.3.1.1.4  Late entry pre-arranged group callWord‑p. 31
Procedures in Figure 7.1.2.3.1.1.4-1 are the signalling control plane procedures for the MCVideo server requesting a newly affiliated member or a member coming back from out of coverage to join an ongoing MCVideo group call.
Pre-conditions:
  1. MCVideo group is previously defined on the group management server with MCVideo users affiliated to that group. All members of the group belong to the same MC system.
  2. It is assumed that MCVideo users on MCVideo client 2 to MCVideo client n are on an ongoing call.
  3. Optionally, the MCVideo client 1 may have activated functional alias to be used.
  4. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
(not reproduced yet)
Figure 7.1.2.3.1.1.4-1: Late entry pre-arranged group call
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Step 1.
MCVideo server determines that MCVideo client 1 which is newly affiliated or coming back from out of coverage has to be invited to join an ongoing group call (late entry).
Step 2.
MCVideo server generates group call request including the information such as MCVideo service identifier (possible for the SIP core to route the request to the MCVideo server), MC service group ID of the group invited to join, offer one or more media types and sends towards the MCVideo client 1 via SIP core.
Step 3.
MCVideo user at MCVideo client 1 is notified about the incoming group call.
Step 4.
Upon MCVideo user at MCVideo client 1 accepting the incoming group call request, MCVideo client 1 sends the group call response including the selected media types to the MCVideo server through the signalling path. If the incoming group call request is rejected by the MCVideo client 1, the MCVideo server should not resend the group call request
Step 5.
MCVideo client 1 is successfully added to the ongoing group call and MCVideo users at MCVideo client 1 to MCVideo client n may be notified about the MCVIDEO client 1 joining the group call.
Step 6.
A notification with the information of media transmissions in the group call is sent to MCVideo client1.
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7.1.2.3.1.1.5  Rejoining callWord‑p. 32
Procedures in Figure 7.1.2.3.1.1.5-1 are the signalling control plane procedures for the MCVideo client to rejoin an ongoing MCVideo group call (e.g. coming back from out of coverage).
Pre-condition:
  1. It is assumed that MCVideo users on MCVideo client 2 to MCVideo client n are on an ongoing call.
  2. Optionally, the MCVideo client 1 may have activated functional alias to be used.
  3. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
(not reproduced yet)
Figure 7.1.2.3.1.1.5-1: Rejoin call
Up
Step 1.
MCVideo client 1 has necessary information for rejoining an ongoing group call, then the MCVideo client 1 initiates group call rejoin request including the ongoing group call information. The MCVideo user at MCVideo client 1 may include a functional alias used within the MCVideo rejoin request.
Step 2.
MCVideo server checks whether the MCVideo client 1 can rejoin the ongoing call (e.g. based upon affiliation status) and checks the functional alias, if present.
Step 3.
MCVideo client 1 is informed that the group call rejoin is successful by sending a group call rejoin response.
Step 4.
MCVideo client 1 is successfully added to the ongoing group call and MCVideo users at MCVideo client 1 to MCVideo client n may be notified about the MCVideo client 1 joining the group call and the functional alias of MCVideo client 1 may be displayed.
Step 5.
A notification with the information of media transmissions in the group call is sent to MCVideo client 1.
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7.1.2.3.1.2  Chat group callWord‑p. 33
7.1.2.3.1.2.1  General
In a chat group (restricted) call model, the MCVideo user individually joins a group call without being explicitly invited by the MCVideo server. The establishment of a chat group (restricted) call does not result in other group members being invited.
Figure 7.1.2.3.1.2.2-1 describes the basic procedure for the MCVideo client initiating an MCVideo group call which uses the chat group (restricted) call model. The chat group (restricted) call model can be used to realize the video conferencing service where only users that have been configured as participants for the video conferencing group are allowed to join the group communications for the given group.
Chat group join mechanism:
  • Each MCVideo client sends a group join request when the MCVideo user wants to participate in the group communication for the group. (This message does not impact the MCVideo user's membership in the group; the MCVideo server will verify that the MCVideo user is an authorized member of the group.)
  • The group join request may include a transmit media request. It is assumed that the group join request will be delivered from MCVideo client to MCVideo server using SIP.
  • The group join request is used to indicate to the MCVideo server that the MCVideo user associated with the given MCVideo client wishes to participate (begin to receive notifications for media transmissions) from the group.
  • The group join request shall cause the MCVideo server to generate an implicit affiliation for the MCVideo user to the group, if the user is not already affiliated to the group.
  • The group join request contains the information needed to negotiate media parameters (on demand) or to associate a pre-established session between MCVideo server and MCVideo client for the group call. The group join request can take the form of a SIP invite.
  • A selected functional alias is not changed by a MCVideo client during the whole participation within a chat group call, i.e. a MCVideo client uses the same functional alias selected when joining the chat group call until the chat group call is released or the MCVideo client leaves the chat group call.
Subsequent participation in a group call when the group is using the chat model:
  • Once an MCVideo client successfully joins a group call which is using the chat model, the MCVideo client connects to the media plane for the media transmission if the media transmission is currently ongoing.
  • If the MCVideo group call is not currently ongoing (i.e.: when MCVideo clients on the group call are not sending or receiving media, and the time out between transmission control exchanges has expired) then the newly joined MCVideo client will only have pre-established its media parameters for the call.
  • If the newly joined MCVideo user wishes to transmit media to the other joined users of the group using the chat model, then the MCVideo client shall use a normal transmission control procedure for transmitting the media.
  • Subsequent group call media transmissions are controlled using transmission control signalling.
  • The MCVideo server may tear down the media plane between successive group calls using the chat model, or the MCVideo server may allow the media plane to remain up between successive group calls using the chat model depending on resources.
Leaving and releasing a chat group:
  • When a user wants to leave a chat group call, the client shall send a group call leave request to the server and release the media plane.
  • The server can release a chat group call by sending a group call release to all joined clients. A server initiated release also releases the media plane for all joined clients.
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7.1.2.3.1.2.2  Chat group call setupWord‑p. 34
MCVideo client 1, client 2, and client 3 are served by the home MCVideo service provider in Figure 7.1.2.3.1.2.2-1.
Pre-conditions:
  1. MCVideo user 2 and MCVideo user 3 have previously joined (affiliated) to the group call. MCVideo client 1, client 2, and client 3 are registered and all users (MCVideo user 1, user 2, and user 3) have been authenticated and authorized to use the MCVideo service.
  2. MCVideo client 1, MCVideo client 2 and MCVideo client 3 may have activated functional alias(es) configured to be used during the group call communication. No call is currently in progress for the group.
  3. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
  4. The MCVideo user on MCVideo client 1 may have bound a functional alias to the MCVideo group ID (TS 23.280).
(not reproduced yet)
Figure 7.1.2.3.1.2.2-1: MCVideo chat group call
Up
Step 1.
MCVideo user 1 indicates to join the group communication for the group. This may include a transmit media request.
Step 1a.
MCVideo client 1 sends a group join request with the MCVideo group ID of the desired group. It contains the MCVideo user's MCVideo ID and the MCVideo client media parameters. The MCVideo user at MCVideo client 1 may include a functional alias used within the MCVideo group join request. If there is a request for media transmission, then the group join request contains an indication of an implicit transmit media request.
Step 1b.
The MCVideo server receives the group join request. MCVideo server generates an implicit affiliation (if the MCVideo user is not already affiliated to the group) and verifies that MCVideo user 1 is authorized to affiliate to the group by following the affiliation procedure for MCVideo. If a functional alias is present, the MCVideo server checks whether it is allowed to be used and if it has been activated for the user.
If the functional alias is provided only in the group join request, or via binding, the MCVideo server proceeds with the value that is provided. If the functional alias is provided in both the group join request and via binding, it is up to the MCVideo server implementation to determine a value for the functional alias to be used.
Step 1c.
The MCVideo server replies with a group join response indicating the acceptance of the group join request and also returns the MCVideo server selected media parameters for the group call in the group join response.
Step 2.
If MCVideo user 1 requests to transmit media by sending transmit media request to MCVideo server, the MCVideo server establishes the media plane (if not already established) for the call.
Step 3.
Transmission control will continue to be used by the transmission control participants associated with MCVideo client 1, MCVideo client 2 and MCVideo client 3 for the duration of the call. .If present, the functional alias of MCVideo client 1, MCVideo client 2 and MCVideo client 3 are displayed where appropriate.
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7.1.2.3.1.2.3  Release chat group call
The procedure describes the case where the MCVideo server releases an ongoing MCVideo group call for all the participants of that group call, since at least one of the conditions for release are met e.g. due to chat duration expiry, last participant leaving or initiator leaving.
Procedures in Figure 7.1.2.3.1.2.3-1 are the procedures for the MCVideo server initiating the release of an ongoing MCVideo group call.
The following precondition applies:
    - A group call is ongoing between MCVideo clients 1, 2 and 3
(not reproduced yet)
Figure 7.1.2.3.1.2.3-1: Release chat group call
Up
Step 1.
MCVideo server would like to release the MCVideo group call which is ongoing e.g., due to chat duration expiry, last participant leaving, or initiator leaving.
Step 2.
MCVideo server identifies the participants of the ongoing group call and generates group call release request to release the ongoing session.
Step 3.
MCVideo server sends a group call release request towards each participant of the ongoing group call.
Step 4.
MCVideo users are notified about the release of the group call.
Step 5.
Optionally the MCVideo client(s) receiving group call release request, may send a group call release response to the MCVideo server.
Step 6.
MCVideo client 1, client 2 and client 3 release the transmission control and media plane resources associated with the group call that is released. Successful release of the group call does not affect the status of affiliation of any of the clients.
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7.1.2.3.1.2.4Void
7.1.2.3.1.2.5  Late entry chat group call, newly joined group memberWord‑p. 37
Procedures in Figure 7.1.2.3.1.2.5-1 are those for a group member entering an ongoing MCVideo group call, i.e. performing a late entry.
Pre-conditions:
  1. MCVideo user 2 and MCVideo user 3 have previously joined to the group. MCVideo client 1, client 2, and client 3 are registered and all users (MCVideo user 1, user 2, and user 3) have been authenticated and authorized to use the MCVideo service.
  2. MCVideo user 1 indicates to join the group communication for the group.
  3. MCVideo users using MCVideo client 1 to MCVideo client n may have activated functional alias(es) configured to be used during the group call communication.
  4. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
  5. The MCVideo user on MCVideo client 1 may have bound a functional alias to the MCVideo group ID (TS 23.280).
(not reproduced yet)
Figure 7.1.2.3.1.2.5-1: Late entry of a newly joined group member
Up
Step 1.
MCVideo client 1 sends a group join request with the MCVideo group ID of the desired group. It contains the MCVideo user's MCVideo ID and the MCVideo client media parameters. The MCVideo user at MCVideo client 1 may include a functional alias used within the MCVideo group join request. If there is a request to transmit, then the group join request contains an indication of an implicit transmit media request.
Step 2.
The MCVideo server receives the group join request. MCVideo server generates an implicit affiliation (if the MCVideo user is not already affiliated to the group) and verifies that MCVideo user 1 is authorized to affiliate to the group. If a functional alias is present, the MCVideo server checks whether it is allowed to be used and if it has been activated for the user.
If the functional alias is provided only in the group join request, or via binding, the MCVideo server proceeds with the value that is provided. If the functional alias is provided in both the group join request and via binding, it is up to the MCVideo server implementation to determine a value for the functional alias to be used.
Step 3.
The MCVideo server replies with a group join response indicating the acceptance of the group join request.
Step 4.
Media plane between MCVideo client 1 and MCVideo server is established using media plane control signalling.
Step 5.
MCVideo users at MCVideo client 2 and MCVideo client 3 may be notified about the MCVideo client 1 joining the group call, and the functional alias of MCVideo client 1 may be displayed.
Step 6.
The MCVideo server may send (6a) Media transmission notification to MCVideo client 1, indicating the current transmitter. Alternatively the MCVideo server may send (6b) Transmit media granted, (6b) Transmit media rejected or (6d) Queue position info.
Step 7.
Transmission control will continue to be used by the transmission control participants associated with MCVideo client 1, MCVideo client 2 and MCVideo client 3. If present, the functional alias of MCVideo client 1, MCVideo client 2 and MCVideo client 3 are displayed where appropriate.
Up
7.1.2.3.1.2.6  Late entry chat group call, MCVideo client coming back from out of coverageWord‑p. 38
Procedures in Figure 7.1.2.3.1.2.6-1 are those for an MCVideo client coming back from out of coverage during an ongoing MCVideo group call.
Pre-conditions:
  1. MCVideo users using MCVideo client 1, MCVideo client 2 and MCVideo client 3 are in an ongoing group call when MCVideo client1 goes out of radio coverage.
  2. MCVideo client1 returns from out of coverage while the group call is still ongoing.
  3. MCVideo users using MCVideo client 1 to MCVideo client n may have activated functional alias(es) configured to be used during the group call communication.
  4. The MCVideo server may have subscribed to the MCVideo functional alias controlling server within the MC system for functional alias activation/de-activation updates.
(not reproduced yet)
Figure 7.1.2.3.1.2.6-1: Late entry of an MCVideo client returning from out of coverage
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Step 1.
MCVideo client 1 or MCVideo server detects that MCVideo client 1 has returned from out of coverage.
Step 2.
Media plane between MCVideo client 1 and MCVideo server is re-established using media plane control signalling.
Step 3.
The MCVideo server may send (3a) Media transmission notification to MCVideo client 1, indicating the current transmitter. Alternatively, the MCVideo server may send (3b) Transmit media granted, (3c) Transmit media rejected or (3d) Queue position info.
Step 4.
MCVideo users at MCVideo client 2 and MCVideo client 3 may be notified about the MCVideo client 1 returning to the group call, and the functional alias of MCVideo client 1 may be displayed.
Step 5.
Transmission control will continue to be used by the transmission control participants associated with MCVideo client 1, MCVideo client 2 and MCVideo client 3. If present, the functional alias of MCVideo client 1, MCVideo client 2 and MCVideo client 3 are displayed where appropriate.
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7.1.2.3.2  Exiting group call due to de-affiliationWord‑p. 39
Procedures in Figure 7.1.2.3.2-1 are the signalling control plane procedures for the MCVideo server requesting a newly de-affiliated member to leave an ongoing MCVideo group call.
Pre-conditions:
  1. MCVideo group is previously defined on the group management server with MCVideo users affiliated to that group. All members of the group belong to the same MC system.
  2. MCVideo users on MCVideo client 1 to MCVideo client n are on an ongoing call.
  3. MCVideo client 1 has been de-affiliated from the MCVideo group.
(not reproduced yet)
Figure 7.1.2.3.2-1: Exiting MCVideo group call due to de-affiliation
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Step 1.
MCVideo client 1 which has been de-affiliated is instructed to leave the ongoing group call.
Step 2.
MCVideo server sends a group call leave request to MCVideo client 1.
Step 3.
MCVideo user at MCVideo client 1 is notified about leaving the group call.
Step 4.
MCVideo client 1 sends the group call leave response and leaves the group call.
Step 5.
MCVideo client 1 is now removed from the ongoing group call and MCVideo users at MCVideo client 2 to MCVideo client n may be notified that MCVideo client 1 has left the group call.
7.1.2.3.3  MCVideo user leaving a group call |R16|Word‑p. 40
Procedures in Figure 7.1.2.3.3-1 are the signalling control plane procedures for the MCVideo user leaving an ongoing MCVideo group call.
Pre-conditions:
  1. MCVideo group is previously defined on the group management server with MCVideo users affiliated to that group. All members of the group belong to the same MC system.
  2. MCVideo users on MCVideo client 1 to MCVideo client n are on an ongoing call.
  3. MCVideo user 1 indicates to leave the group call
(not reproduced yet)
Figure 7.1.2.3.3-1: MCVideo user leaving a group call
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Step 1.
MCVideo client 1 sends a group call leave request to the MCVideo server.
Step 2.
MCVideo server sends a group call leave response to MCVideo client 1.
Step 3.
Release of transmission control and media plane resources associated with the group call for MCVideo client 1.
Step 4.
MCVideo users at MCVideo client 2 to MCVideo client n may be notified that the MCVideo user of client 1 has left the group call.
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