Content for  TS 23.282  Word version:  18.3.0

User at MCData client 1 would like to initiate an ad hoc group data communication. The MCData client 1 initiates the ad hoc group data communication by sending the ad hoc group data session request containing the list of participants to the MCData server. Encryption supported information element shall be set to true since end-to-end encryption is supported. An SDP offer containing the MCData client media parameters is included. If the MCData user of MCData client 1 has selected a functional alias, then the ad hoc group data session request contains that functional alias. If the MCData user at MCData client 1 initiates an MCData emergency ad hoc group data communication or the MCData emergency state is already set for the MCData client 1 (due to a previously triggered MCData emergency alert):

1. the MCData ad hoc group data session request shall contain an emergency indicator;
2. if the MCData emergency state is not set already, MCData client 1 sets its MCData emergency state. The MCData emergency state of MCData client 1 is retained until explicitly cancelled by the user of MCData client 1.

The MCData server accepts the ad hoc group data session request if the ad hoc group data communication is supported and authorized. Otherwise reject the ad hoc group data session 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 data communication setup. If functional alias is present, the MCData 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 data session request, the MCData server checks the privacy policy of the MCData user to decide if the location information of MCData client 1 can be provided to other users on the ad hoc group data communication (refer to Annex A.3 "Authorisation to provide location information to other MCData users on a data communication when talking"). If an emergency indicator is present in the received MCData ad hoc group data session request, the MCData ad hoc group is considered to be in the in-progress emergency state until this ad hoc group data communication is terminated; and If an imminent peril indicator is present in the received MCData ad hoc group data session request, the MCData ad hoc group is considered to be in the in-progress imminent peril state until this ad hoc group data communication is terminated. The MCData server considers the ad hoc group data communication participants as implicitly affiliated to the ad hoc group.

The MCData server shall send the ad hoc group data session request return message to MCData client 1 containing the below:

1. The MCData ad hoc group ID generated by the MCData server; and
2. Result of whether the ad hoc group data session request is authorized or not

If the ad hoc group data session request is not authorized, MCData client 1 shall not proceed with the rest of the steps.

The MCData server sends the ad hoc group data session requests towards the MCData clients of the invited users based on step 1. While sending the ad hoc group data session requests, the MCData server shall remove the information elements that are not required to be conveyed to the target MCData clients (e.g. MCData ID list of the users who are required to acknowledge)

The receiving MCData clients are notified about the incoming ad hoc group data session request.

The receiving MCData clients accept the ad hoc group data session requests and send ad hoc group data session responses to the MCData server. The response may also contain a functional alias of the responding MCData user, which is verified (valid and activated for the user) by the MCData server.

The MCData server sends the ad hoc group data session response to MCData client 1 through the signalling path to inform about successful data communication establishment.

If the initiating MCData user requires the acknowledgement from the invited MCData users, and the required MCData users do not acknowledge the data session setup within a configured time (the "acknowledged data communication setup timeout"), then the MCData server may proceed with or abandon the data session and then notify the initiating MCData user that the acknowledgements did not include all required members according to ad hoc group data communication policy from the user profile configuration. The MCData server may notify the initiating MCData user of all MCData users who did not acknowledge the ad hoc group data session request within the configured time. This notification may be sent to the initiating MCData user by the MCData server more than once during the data communication when MCData users join or leave the MCData ad hoc group data communication.

MCData client 1, MCData client 2, MCData client 3 and MCData client 4 establish media plane for data communication.

It is assumed that MCData users on MCData client 1, client 2 and client 3 are already part of the ongoing ad hoc group data communication.

MCData server would like to release the MCData ad hoc group data communication which is ongoing e.g., due to hang time expiry, last participant leaving, second last participant leaving, initiator leaving.

MCData server identifies the participants of the ongoing ad hoc group data communication and generates ad hoc group data session release request to release ongoing data communication. The MCData server cancels the in-progress emergency state or in-progress imminent peril state of the ad hoc group if the ad hoc group data communication is an emergency or imminent peril data communication respectively.

MCData server sends ad hoc group data session release request via SIP core towards each participant of the ongoing ad hoc group data communication.

MCData users are notified about the release of the ad hoc group data communication.

MCData client(s) receiving ad hoc group data session release request, acknowledge towards the MCData server by sending an ad hoc group data session release response.

MCData client 1, client 2 and client 3 have successfully released the media plane resources associated with the ad hoc group data communication that is terminated and the ad hoc group ceases to exist (i.e., further data communication is not possible over the same ad hoc group.

User at MCData client 1 would like to initiate an ad hoc group data communication in-order to invite the participants satisfying specific criteria. The MCData client 1 initiates the ad hoc group data communication by sending the ad hoc group data session request containing the details of the criteria to be applied by the MCData 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 MCData group whose configuration is to be applied is included. An SDP offer containing the MCData client media parameters is included. If the MCData user of MCData client 1 has selected a functional alias, then the ad hoc group data session request contains that functional alias. If the MCData user at MCData client 1 initiates an MCData emergency ad hoc group data communication or the MCData emergency state is already set for the MCData client 1 (due to a previously triggered MCData emergency alert):

1. the MCData ad hoc group data session request shall contain an emergency indicator;
2. if the MCData emergency state is not set already, MCData client 1 sets its MCData emergency state. The MCData emergency state of MCData client 1 is retained until explicitly cancelled by the user of MCData client 1.

The MCData server accepts the ad hoc group data session request if the ad hoc group data communication is supported and authorized. Otherwise reject the ad hoc group data session request and do not continue with the rest of the steps. If functional alias is present, the MCData 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 data session request, the MCData server checks the privacy policy of the MCData user to decide if the location information of MCData client 1 can be provided to other users on the data communication (refer to Annex A.3 "Authorisation to provide location information to other MCData users on a data communication when talking"). If an emergency indicator is present in the received MCData ad hoc group data session request, the MCData ad hoc group is considered to be in the in-progress emergency state until this ad hoc group data communication is terminated; and If an imminent peril indicator is present in the received MCData ad hoc group data session request, the MCData ad hoc group is considered to be in the in-progress imminent peril state until this ad hoc group data communication is terminated.

The MCData server shall send the ad hoc group data session request return message to MCData client 1 containing the below:

1. The MCData ad hoc group ID generated by the MCData server; and
2. Result of whether the ad hoc group data session request is authorized or not

If the ad hoc group data session request is not authorized, MCData server and client 1 shall not proceed with the rest of the steps.

The MCData server determines the list of participants to be invited for the ad hoc group data communication 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.

The MCData server sends the ad hoc group data session requests towards the MCData clients 2 and 3. While sending the ad hoc group data session requests, the MCData server shall remove the information elements that are not required to be conveyed to the target MCData clients. This request carries the pre-configured group ID whose configuration is to be applied for this ad hoc group data communication if end-to-end encryption is requested. The MCData server considers the ad hoc group data communication participants as implicitly affiliated to the ad hoc group.

The receiving MCData clients are notified about the incoming ad hoc group data communication.

The receiving MCData clients accept the ad hoc group data session requests and send ad hoc group data session responses to the MCData server. The response may also contain a functional alias of the responding MCData user, which is verified (valid and activated for the user) by the MCData server.

The MCData server sends the ad hoc group data session response to MCData client 1 through the signalling path to inform about successful data communication establishment.

The MCData server may notify the initiating MCData user of all MCData users who acknowledged the ad hoc group data session request and joined the ad hoc group data communication. This notification may be sent to the initiating MCData user by the MCData server more than once during the data communication when MCData users join or leave the MCData ad hoc group data communication.

MCData client 1, MCData client 2 and MCData client 3 establish media plane resources.

The MCData client 1 sends the modify ad hoc group data session participants request to the MCData server in order to remove MCData client 3 from the ongoing ad hoc group data communication and add MCData client 2 into it.

The MCData server verifies whether the MCData client 1 is authorized to add or remove (modify) the participants of the on-going ad hoc group data communication.

The MCData server sends modify ad hoc group data session participants response to the MCData client 1.

The MCData server sends the ad hoc group data session leave request to the MCData client 3 in order to remove it from the on-going ad hoc group data communication.

The MCData client 3 notifies the user of the ad hoc group data session leave request.

The MCData client 3 sends the ad hoc group data session leave response to the MCData server.

The MCData server removes the MCData client 3 from the ongoing ad hoc group data communication.

The MCData server sends the ad hoc group data session request towards MCData client 2.

The receiving MCData client 2 notifies the user about the incoming ad hoc group data communication.

The MCData client 2 accepts the ad hoc group data session request and send ad hoc group data session responses to the MCData server. The response may also contain a functional alias of the responding MCData user, which is verified (valid and activated for the user) by the MCData server.

The MCData server may notify the initiating MCData user of all the users who are added to the on-going ad hoc group data communication. This notification may be sent to the initiating MCData user by the MCData server more than once during the data communication when MCData users join or leave the ad hoc group data communication.

The MCData server may notify the participants about the change in the participants list of on-going ad hoc group data communication.

The ad hoc group data communication is established and on-going with the participants MCData client 1, MCData client 2, MCData client 3 and MCData client 4. The participants list is determined by the MCData server based on the criteria specified by the MCData client 1 while initiating the data communication.

The MCData server detects that the MCData client 5 satisfies the criteria specified by the MCData client.

The MCData server sends the ad hoc group data session request to the MCData client 5.

The MCData client 5 notifies the user about the incoming ad hoc group data communication.

The MCData client 5 accepts the ad hoc group data session request and sends the ad hoc group data session response to the MCData server.

The on-going ad hoc group data communication is updated by adding MCData client 5 which satisfies the criteria specified by the MCData client 1.

The MCData server detects that the MCData client 4 is no more satisfying the criteria to be the participant of the ad hoc group data communication.

The MCData server sends the ad hoc group data communication leave request to the MCData client 4 and removes it from the on-going ad hoc group data communication.

The MCData client 4 notifies the user of the ad hoc group data session leave request.

The MCData client 4 sends the ad hoc group data session leave response to the MCData server.

The on-going ad hoc group data communication is updated by removing MCData client 4, which no more satisfies the criteria specified by the MCData client 1.