Content for  TS 23.379  Word version:  19.1.0

It is assumed that MCPTT users on MCPTT client 1 and MCPTT client 2 are already registered for receiving MCPTT service to their respective MCPTT service provider, as per procedure in subclause 10.2.

MCPTT user at MCPTT client 1 would like to initiate an MCPTT private call for the chosen MCPTT user. For a private call with floor control, floor control is to be established.

MCPTT client 1 sends an MCPTT private call request towards the home MCPTT server 1 (via SIP core) using a service identifier as defined in TS 23.228 for MCPTT, for establishing private call with the MCPTT client 2 registered at MCPTT service provider 2. The MCPTT private call request contains the MCPTT id of invited user and an SDP offer containing one or more media types. For a private call with floor control, the MCPTT private call request also contains an element that indicates that MCPTT client 1 is requesting the floor. If the private call request request the floor it may include location information. The MCPTT client 1 may include a requested commencement mode that indicates that the call is to be established in automatic commencement mode if automatic commencement mode is requested by the initiating user.

MCPTT server 1 checks whether the MCPTT user at MCPTT client 1 is authorized to initiate the private call. If the MCPTT private call request requested automatic commencement mode then the MCPTT server 1 also checks whether the MCPTT user at MCPTT client 1 is authorized to initiate a call in automatic commencement mode.

MCPTT server 1 may provide a progress indication to MCPTT client 1 to indicate progress in the call setup process.

If authorized, MCPTT server 1 includes information that it communicates using MCPTT service, offers the same media types or a subset of the media types contained in the initial received request, includes an automatic commencement mode indication if automatic commencement mode was requested by and authorised for the calling user and sends the corresponding MCPTT private call request towards the MCPTT system (via SIP core) of the MCPTT client specified in the original MCPTT private call request (MCPTT client 2) i.e., MCPTT server 2. If location information was included in the private call request, the MCPTT server checks the privacy policy of the MCPTT user to decide if the location information of MCPTT client 1 can be provided to the other user on the call (refer to Annex A.3 "Authorisation to provide location information to other MCPTT users on a call when talking").

MCPTT server 2 checks whether the MCPTT user at MCPTT client 2 is authorized to receive a private call.

MCPTT server 2 includes information that it communicates using MCPTT service, offers the same media types or a subset of the media types contained in the initial received request, includes a requested automatic commencement mode indication based on a requested automatic commencement mode by the calling user or based upon the setting of the called MCPTT client and sends the received MCPTT private call request towards the MCPTT client specified in the received MCPTT private call request (i.e., MCPTT client 2). If the called MCPTT user has registered to the MCPTT service with multiple MCPTT UEs and has designated the MCPTT UE for receiving the private calls, then the incoming MCPTT private call request is delivered only to the designated MCPTT UE.

The receiving MCPTT client 2 notifies the user about the incoming private call.

The receiving MCPTT client 2 accepts the private call automatically, and an acknowledgement is sent to the MCPTT server 1 (via SIP core and MCPTT server 2).

Upon receiving the MCPTT private call response from MCPTT client 2 accepting the private call request, MCPTT client 1 is informed about successful call establishment.

MCPTT client 1 and MCPTT client 2 have successfully established media plane for communication and either user can transmit media. For successful call establishment of a private call with implicit floor control request from MCPTT client 1, floor participant at MCPTT client 1 is granted floor by the floor control server at MCPTT service provider 1, giving it permission to transmit. At the same time floor participant at MCPTT client 2 is informed by the floor control server at MCPTT service provider 1 that the floor is taken.

It is assumed that MCPTT users on MCPTT client 1 and MCPTT client 2 are already registered for receiving MCPTT service to their respective MCPTT service provider, as per procedure in subclause 10.2.

MCPTT user at MCPTT client 1 would like to initiate an MCPTT private call for the selected MCPTT user. For a private call with floor control, floor control is to be established.

MCPTT client 1 sends an MCPTT private call request towards the home MCPTT server 1 (via SIP core), for establishing private call with the MCPTT client 2 registered at MCPTT service provider 2. For a private call with floor control, the MCPTT private call request contains an element that indicates that MCPTT client 1 is requesting the floor. If the call request requests the floor the call request may include location information. The MCPTT client 1 may include a requested commencement mode that indicates that the call is to be established in manual commencement mode if manual commencement mode is requested by the initiating user.

MCPTT server 1 checks whether the MCPTT user at MCPTT client 1 is authorized to initiate the private call. The MCPTT server 1 also checks whether the MCPTT user at MCPTT client 1 is authorized to initiate a call in manual commencement mode.

If authorized, MCPTT server 1 sends the corresponding MCPTT private call request towards the MCPTT system (via SIP core) of the MCPTT client specified in the original MCPTT private call request (MCPTT client 2) i.e., MCPTT server 2. If location information was included in the private call request, the MCPTT server checks the privacy policy of the MCPTT user to decide if the location information of MCPTT client 1 can be provided to the other user on the call (refer to Annex A.3 "Authorisation to provide location information to other MCPTT users on a call when talking").

MCPTT server may provide a progress indication to MCPTT client 1 to indicate progress in the call setup process.

The MCPTT server 2 checks whether the MCPTT user at MCPTT client 2 is authorized to receive a private call and also checks the commencement mode setting of MCPTT client 2.

The MCPTT server 2 offers the same media types or a subset of the media types contained in the initial received request and sends an MCPTT private call request towards the MCPTT client specified in the received MCPTT private call request (i.e., MCPTT client 2). If the called MCPTT user has registered to the MCPTT service with multiple MCPTT UEs and has designated the MCPTT UE for receiving the private calls, then the incoming MCPTT private call request is delivered only to the designated MCPTT UE.

The MCPTT user is alerted. MCPTT client 2 sends an MCPTT ringing to the MCPTT server 1 (via server 2).

The MCPTT server 1 sends an MCPTT ringing to MCPTT client 1, indicating that MCPTT client 2 is being alerted.

MCPTT user 2 has accepted the call using manual commencement mode (i.e. has taken some action to accept via the user interface) which causes MCPTT client 2 to send an MCPTT private call response to the MCPTT server 1 (via SIP core and MCPTT server 2)

Upon receiving the MCPTT private call response from MCPTT client 2 accepting the private call request, MCPTT client 1 is informed about successful call establishment.

MCPTT client 1 and client 2 have successfully established media plane for communication and either user can transmit media. For successful call establishment of a private call with implicit floor control request from MCPTT client 1, floor participant at MCPTT client 1 is granted the floor by the floor control server at MCPTT service provider 1, giving it permission to transmit. At the same time floor participant at MCPTT client 2 is informed by the floor control server at MCPTT service provider 1 that the floor is taken.

The user at the MCPTT client 1 initiates an MCPTT emergency private call. MCPTT client 1 sets its MCPTT emergency state. MCPTT client 1 retains the MCPTT emergency state until explicitly cancelled by the user of MCPTT client 1.

MCPTT client 1 sends an MCPTT emergency private call request towards the MCPTT server. The request contains an indication of the MCPTT emergency. MCPTT user at MCPTT client 1 may select a functional alias as calling party address and the MCPTT server verifies whether the provided functional alias can be used. Instead of an MCPTT ID the MCPTT user at MCPTT client 1 may also select a functional alias as called party address, which the MCPTT server replaces by an appropriate MCPTT ID. The MCPTT server records the identity of the MCPTT user that initiated the MCPTT emergency private call until the MCPTT emergency is cancelled. If the MCPTT client is configured to send an MCPTT emergency alert when initiating an MCPTT emergency private call, the request also contains an indication that an MCPTT emergency alert is to be initiated.

MCPTT server sends the MCPTT emergency private call request towards the target MCPTT client. The request contains an indication of the in-progress emergency. The request contains an indication of an MCPTT emergency alert if the request from the originator indicated MCPTT emergency alert.

The MCPTT user on MCPTT client 2 is notified of the incoming MCPTT emergency private call and may display the functional alias of MCPTT client 1.

The receiving MCPTT client acknowledges the MCPTT emergency private call request to the MCPTT server.

The MCPTT server adjusts the priority of the underlying bearer.

The MCPTT server informs MCPTT client 1 about the successful MCPTT emergency private call establishment.

MCPTT client 1 and MCPTT client 2 establish the media plane for communication. The MCPTT client 1 can override MCPTT client 2 unless MCPTT client 2 is also in the MCPTT emergency state.

The MCPTT user at MCPTT client 1 initiates an emergency. MCPTT client 1 sets its MCPTT emergency state. MCPTT client 1 retains the MCPTT emergency state until explicitly cancelled by the user of MCPTT client 1.

MCPTT client 1 requests the MCPTT server to upgrade the private call to in-progress emergency by sending an MCPTT emergency request. If configured to send an MCPTT alert when initiating an MCPTT emergency upgrade, the request also contains an indication that an MCPTT alert is to be initiated. The request may contain an indication of an implicit floor request. If the emergency private call request includes an implicit floor reques it may also include location information.

The MCPTT server sends the MCPTT emergency request towards MCPTT client 2, the MCPTT client of the other participant. If location information was included in the emergency private call request, the MCPTT server checks the privacy policy of the MCPTT user to decide if the location information of MCPTT client 1 can be provided to the other user on the call (refer to Annex A.3 "Authorisation to provide location information to other MCPTT users on a call when talking").

The MCPTT user of MCPTT client 2 is notified of the in-progress emergency of the MCPTT emergency private call.

The receiving MCPTT client acknowledges the MCPTT emergency request to the MCPTT server.

The MCPTT server adjusts the priority of the underlying bearer for both participants in the private call. The priority is retained until the call ends.

The MCPTT server confirms the upgrade request to MCPTT client 1.

MCPTT client 1 and MCPTT client 2 continue with the private call, which has been transformed into an MCPTT emergency private call. MCPTT client 1 can override MCPTT client 2 unless MCPTT client 2 is also in the MCPTT emergency state.