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Content for  TS 23.281  Word version:  19.0.0

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7.19.3  Proceduresp. 181

7.19.3.1  Ad hoc group call procedures in single MCVideo systemp. 181

7.19.3.1.1  Ad hoc group call setupp. 181
Figure 7.19.3.1.1-1 below illustrates the ad hoc group call setup procedure initiated by an authorized user.
Pre-conditions:
  1. The authorized user at MCVideo client 1 wants to invite MCVideo users at MCVideo client 2, MCVideo client 3 and MCVideo client 4 for the ad hoc group call and is aware of the MCVideo IDs of the participants or to invite the ad hoc group member if the ad hoc group call follows an ad hoc group emergency alert, the MCVideo client 1 is aware of the ad hoc group ID.
  2. Number of participants being invited for the ad hoc group call is within the limit.
  3. End-to-End encryption is supported for this ad hoc group call.
  4. The pre-configured group identity and pre-configured group configuration to be used for an ad hoc group have been preconfigured in MCVideo client and other participants of ad hoc group have also received the relevant security related information to allow them to communicate in an ad hoc group communication.
Reproduction of 3GPP TS 23.281, Fig. 7.19.3.1.1-1: Ad hoc group call setup
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Step 1.
User at MCVideo client 1 would like to initiate an ad hoc group call. The MCVideo client 1 initiates the ad hoc group call by sending the ad hoc group call request containing the list of participants or an ad hoc group ID from an ad hoc group emergency alert to the MCVideo server. Encryption supported information element shall be set to true since end-to-end encryption is supported. An SDP offer containing the MCVideo client media parameters is included. If there is a transmit media request to transmit media, then the ad hoc group call request contains an indication of an implicit transmit media request. If the MCVideo user of MCVideo client 1 has selected a functional alias, then the ad hoc group call request contains that functional alias. If the ad hoc group call request contains an implicit transmit media request it may also include location information.
If the MCVideo user at MCVideo client 1 initiates an MCVideo emergency ad hoc group call or the MCVideo emergency state is already set for the MCVideo client 1 (due to a previously triggered MCVideo emergency alert):
  1. the MCVideo ad hoc group call request shall contain an emergency indicator;
  2. if the MCVideo emergency state is not set already, MCVideo client 1 sets its MCVideo emergency state. The MCVideo emergency state of MCVideo client 1 is retained until explicitly cancelled by the user of MCVideo client 1.
Step 2.
The MCVideo server accepts the ad hoc group call request if the ad hoc group call is supported and authorized. Otherwise reject the ad hoc group call request and do not continue with the rest of the steps. If authorised, it validates whether the number of invited participants is within the configured limit before proceeding with the call setup.
If functional alias is present, the MCVideo server checks whether the provided functional alias allowed to be used and has been activated for the user.
If location information was included in the ad hoc group call request, the MCVideo server checks the privacy policy of the MCVideo user to decide if the location information of MCVideo client 1 can be provided to other users on the call (refer to Annex A.3 "Authorisation to provide location information to other MCVideo users on a call when talking").
If an emergency indicator is present in the received MCVideo ad hoc group call request, the MCVideo ad hoc group is considered to be in the in-progress emergency state until this ad hoc group call is terminated; and
If an imminent peril indicator is present in the received MCVideo ad hoc group call request, the MCVideo ad hoc group is considered to be in the in-progress imminent peril state until this ad hoc group call is terminated.
If the the MC service users' information received in step 1 does not contain an ad hoc group ID from an ad hoc group emergency alert, the MCVideo server forms the ad hoc group by using MCVideo users' information received in step 1, determines the preconfigured group to be used for the configuration of the ad hoc group and assigns a MCVideo group ID for the newly formed ad hoc group.
The MCVideo server considers the ad hoc group call participants as implicitly affiliated to the ad hoc group.
Step 3.
The MCVideo server shall send the ad hoc group call request return message to MCVideo client 1 containing the below:
  1. The MCVideo ad hoc group ID either generated by the MCVideo server or provided by the MCVideo client 1 if the ad hoc group ID is from an ad hoc group emergency alert (only included when the ad hoc group call is authorized);
  2. The group ID of the pre-configured group to be used for the ad hoc group call (only included when the ad hoc group call is authorized); and
  3. Result of whether the ad hoc group call is authorized or not.
If the ad hoc group call request is not authorized, MCVideo client 1 shall not proceed with the rest of the steps.
Step 4a-4c.
The MCVideo server sends the ad hoc group call requests towards the MCVideo clients of the invited users based on step 1. While sending the ad hoc group call requests, the MCVideo server shall remove the information elements that are not required to be conveyed to the target MCVideo clients (e.g. MCVideo ID list of the users who are required to acknowledge)
Step 5a-5c.
The receiving MCVideo clients are notified about the incoming ad hoc group call.
Step 6a-6c.
The receiving MCVideo clients accept the ad hoc group call requests and send ad hoc group call responses to the MCVideo server. The response may also contain a functional alias of the responding MCVideo user, which is verified (valid and activated for the user) by the MCVideo server.
Step 7.
The MCVideo server sends the ad hoc group call response to MCVideo client 1 through the signalling path to inform about successful call establishment.
Step 8.
If the initiating MCVideo user requires the acknowledgement from the invited MCVideo users, and the required MCVideo users 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 ad hoc group call policy from the user profile configuration. The MCVideo server may notify the initiating MCVideo user of all MCVideo users who did not acknowledge the ad hoc group call request within the configured time. 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 ad hoc group call.
Step 9.
MCVideo client 1, MCVideo client 2, MCVideo client 3 and MCVideo client 4 establish media plane and transmission control resources.
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7.19.3.1.2  Release ad hoc group callp. 184
The procedure focuses on the case where the MCVideo server releases an ongoing MCVideo ad hoc group call for all the participants of that ad hoc group call, since at least one of the release conditions are met e.g., due to hang time expiry, last participant leaving, second last participant leaving, initiator leaving.
Figure 7.19.3.1.2-1 below illustrates the signalling control plane procedure for the MCVideo server initiating termination an ongoing ad hoc group call.
Reproduction of 3GPP TS 23.281, Fig. 7.19.3.1.2-1: Release ad hoc 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 ad hoc group call.
Step 2.
MCVideo server would like to release the MCVideo ad hoc group call which is ongoing e.g., due to hang time expiry, last participant leaving, second last participant leaving, initiator leaving.
Step 3.
MCVideo server identifies the participants of the ongoing ad hoc group call and generates ad hoc group call release request to release ongoing session. The MCVideo server cancels the in-progress emergency state or in-progress imminent peril state of the ad hoc group if the ad hoc group call is an emergency or imminent peril call respectively.
Step 4.
MCVideo server sends ad hoc group call release request via SIP core towards each participant of the ongoing ad hoc group call.
Step 5.
MCVideo users are notified about the release of the ad hoc group call.
Step 6.
MCVideo client(s) receiving ad hoc group call release request, acknowledge towards the MCVideo server by sending an ad hoc group call release response.
Step 7.
MCVideo client 1, client 2 and client 3 have successfully released the transmission control and media plane resources associated with the ad hoc group call that is terminated and the ad hoc group ceases to exist (i.e., further call is not possible over the same ad hoc group, otherwise if the ad hoc group call follows an ad hoc group emergency alert the ad hoc group continues to exist (i.e., further calls over the same ad hoc group are possible).
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7.19.3.1.3  Ad hoc group call setup with MCVideo server determining the participants listsp. 185
Figure 7.19.3.1.3-1 below illustrates the ad hoc group call setup procedure initiated by the MCVideo user and MCVideo client 1 wherein the list of participants is determined by the MCVideo server based on the citeria received from the MCVideo client.
Pre-conditions:
  1. The MCVideo user at MCVideo client 1 is authorized to initate ad hoc group call.
  2. The MCVideo user at MCVideo client 1 wants to invite MCVideo users who are satisying certain criteria for the ad hoc group call.
Reproduction of 3GPP TS 23.281, Fig. 7.19.3.1.3-1: Ad hoc group call participants determined by MCVideo server
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Step 1.
User at MCVideo client 1 would like to initiate an ad hoc group call in-order to invite the participants satisfying specific criteria. The MCVideo client 1 initiates the ad hoc group call by sending the ad hoc group call request containing the details of the criteria to be applied by the MCVideo server for determining the participants list. If end-to-end encryption is supported, the Encryption supported information element shall be set to true and pre-configured MCVideo group whose configuration is to be applied is included. An SDP offer containing the MCVideo client media parameters is included. If there is a transmission request to transmit, then the ad hoc group call request contains an indication of an implicit transmit media request. If the MCVideo user of MCVideo client 1 has selected a functional alias, then the ad hoc group call request contains that functional alias. If the ad hoc group call request contains an implicit transmit media request it may also include location information.
If the MCVideo user at MCVideo client 1 initiates an MCVideo emergency ad hoc group call or the MCVideo emergency state is already set for the MCVideo client 1 (due to a previously triggered MCVideo emergency alert):
  1. the MCVideo ad hoc group call request shall contain an emergency indicator;
  2. if the MCVideo emergency state is not set already, MCVideo client 1 sets its MCVideo emergency state. The MCVideo emergency state of MCVideo client 1 is retained until explicitly cancelled by the user of MCVideo client 1.
Step 2.
The MCVideo server accepts the ad hoc group call request if the ad hoc group call is supported and authorized. Otherwise reject the ad hoc group call request and do not continue with the rest of the steps.
If functional alias is present, the MCVideo server checks whether the provided functional alias is allowed to be used and has been activated for the user.
If location information was included in the ad hoc group call request, the MCVideo server checks the privacy policy of the MCVideo user to decide if the location information of MCVideo client 1 can be provided to other users on the call (refer to Annex A.3 "Authorisation to provide location information to other MCVideo users on a call when talking").
If an emergency indicator is present in the received MCVideo ad hoc group call request, the MCVideo ad hoc group is considered to be in the in-progress emergency state until this ad hoc group call is terminated; and
If an imminent peril indicator is present in the received MCVideo ad hoc group call request, the MCVideo ad hoc group is considered to be in the in-progress imminent peril state until this ad hoc group call is terminated.
If the information received in the request in step 1 does not contain an ad hoc group ID from an ad hoc group emergency alert, the MCVideo server forms the ad hoc group by using received information, and determines the preconfigured group to be used for the configuration of the ad hoc group. The MCVideo server assigns a MCVideo group ID for the newly formed ad hoc group. Further, the ad hoc group participants are included to ad hoc group once determined as specified in the step 4.
Step 3.
The MCVideo server shall send the ad hoc group call request return message to MCVideo client 1 containing the below:
  1. The MCVideo ad hoc group ID, either generated by the MCVideo server, if not included in the ad hoc group call request of step 1, or if the provided MCVideo ad hoc group ID is not accepted by the MCVideo server, or provided by the MCVideo client 1 if the ad hoc group ID is from an ad hoc group emergency alert;
  2. The group ID of the pre-configured group to be used for the ad hoc group communication (only included when the ad hoc group data session is authorized); and
  3. Result of whether the ad hoc group call is authorized or not
If the ad hoc group call request is not authorized, MCVideo server and client 1 shall not proceed with the rest of the steps.
Step 4.
The MCVideo server determines the list of participants to be invited for the ad hoc group call based on the information present in the information element Criteria for determining the participants. This information element could carry either criteria or indicator identifying pre-defined criteria or a combination of both.
Step 5.
The MCVideo server sends the ad hoc group call requests towards the MCVideo clients 2 and 3. While sending the ad hoc group call requests, the MCVideo server shall remove the information elements that are not required to be conveyed to the target MCVideo clients. This request carries the pre-configured group ID whose configuration is to be applied for this ad hoc group call if end-to-end encryption is requested. The MCVideo server considers the ad hoc group call participants as implicitly affiliated to the ad hoc group.
Step 6.
The receiving MCVideo clients are notified about the incoming ad hoc group call.
Step 7.
The receiving MCVideo clients accept the ad hoc group call requests and send ad hoc group call responses to the MCVideo server. The response may also contain a functional alias of the responding MCVideo user, which is verified (valid and activated for the user) by the MCVideo server.
Step 8.
The MCVideo server sends the ad hoc group call response to MCVideo client 1 through the signalling path to inform about successful call establishment.
Step 9.
The MCVideo server may notify the initiating MCVideo user of all MCVideo users who acknowledged the ad hoc group call request and joined the ad hoc group call. 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 ad hoc group call. If the authorized users (not shown in figure) are configured to receive the participants information of ad hoc group call, the MCVideo server provides ad hoc group call notify about all MCVideo users who acknowledged the ad hoc group call request and joined the ad hoc group call, and when MCVideo users join or leave the MCVideo ad hoc group call.
Step 10.
MCVideo client 1, MCVideo client 2 and MCVideo client 3 establish media plane and transmission control resources.
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