The MCPTT user is able to receive MCPTT media services (e.g. group communication, private calls) from partner MCPTT systems in normal and roaming conditions. In this service delivery model, the media plane transmissions between the MCPTT UE of the user and the partner MCPTT system can be achieved directly or via the primary MCPTT system, selected by the PLMN operator's policy. The protocol used for media plane signalling is non-SIP like RTCP.
Figure 10.12-1 provides the procedure for media related signalling.
Figure 10.12-2 provide the procedure for the media transmission (directly) between MCPTT UE of the user and the partner MCPTT system.
Figure 10.12-3 provides the procedure for the media transmission (via the primary MCPTT system) between MCPTT UE of the user and the partner MCPTT system.
Pre-conditions:
The MCPTT group is defined in the partner MCPTT system, where the MCPTT client of user receives the MCPTT service.
An MCPTT group call is set up and active.
The partner MCPTT system is the group host MCPTT server that is hosting the MCPTT group. The corresponding floor control server manages the media corresponding to the group call.
Protocol used for signalling of media plane is non-SIP, it can be protocol like RTCP.
Media related signalling is sent via the primary MCPTT system.
The path for media between the MCPTT UE and partner MCPTT system has been selected to be sent directly to the partner MCPTT system or via the primary MCPTT system based on PLMN operator's policy.
The floor participant corresponding to the MCPTT user sends a floor request message to floor control server (partner MCPTT system) to get the authorization and/or permission to talk.
The floor control server (partner MCPTT system) performs the authorization and arbitrates between requests that are in contention (i.e., floor control).
The MCPTT system makes use of all of the procedures for location management as specified in TS 23.280, utilising the CSC-14 reference point between the location management client and location management server and the CSC-15 reference point between the MCPTT server and location management server.
The ambient listening call is a type of a private MCPTT call that only allows a "listened to" user to transmit media to a "listening" user such that there is no indication on the MCPTT UE of the "listened to" user about the call and the media transmission.
There are two types of ambient listening call as below:
Remotely initiated ambient listening is initiated by the authorized user (e.g., dispatcher) who wants to listen to another user. In this case, the "listened to" user is the called party, and shall automatically accept the call without causing any indication about the call and transmit the media to the "listening" user.
Locally initiated ambient listening is initiated by an authorized user who wants another user to listen to the MCPTT UE communication. In this case, the "listened to" user is the calling party and shall automatically transmit the media to the "listening" user without causing any indication about the call processing and media transmission.
Table 10.14.2.1-1 describes the information flow ambient listening call request from the MCPTT client to the MCPTT server and MCPTT server to the MCPTT client.
Table 10.14.2.2-1 describes the information flow ambient listening call response from the MCPTT client to the MCPTT server and MCPTT server to the MCPTT client.
Table 10.14.2.3-1 describes the information flow ambient listening call release request from the MCPTT client to the MCPTT server and MCPTT server to the MCPTT client.
Table 10.14.2.4-1 describes the information flow ambient listening call release response from the MCPTT client to the MCPTT server and MCPTT server to the MCPTT client.
The MCPTT service provides the capability for an authorised user to initiate a remotely initiated ambient listening call at an MCPTT client.
Figure 10.14.3.1-1 illustrates the information flow for remotely initiated ambient listening call setup.
Pre-conditions:
MCPTT client 1 is the client of the authorized user who is authorized to invoke a remotely initiated ambient listening call to be set up at the requested MCPTT client 2.
MCPTT user 1 is the "listening" user at MCPTT client 1, and MCPTT user 2 is the "listened to" user at MCPTT client 2.
MCPTT client 1 initiates a remotely initiated ambient listening call by sending the ambient listening call request to the MCPTT server. The remotely initiated ambient listening call type is included.
The MCPTT server performs an authorization check for the authorized user 1 for the remotely initiated ambient listening call. If authorization fails, the MCPTT server provides a failure response to MCPTT client 1. The MCPTT server also performs check whether MCPTT client 2 is engaged in an MCPTT Private Call or an MCPTT Group Call. If MCPTT client 2 is engaged in an MCPTT call, then the ambient listening call set up fails and response is provided to MCPTT client 1.
The MCPTT service provides the capability for an authorised user to initiate a locally initiated ambient listening call at an MCPTT client.
Figure 10.14.3.2-1 illustrates the information flow for locally initiated ambient listening call setup.
Pre-conditions:
MCPTT client 2 is the client of the authorized user who is authorized to invoke a locally initiated ambient listening call to be set up at the requested MCPTT client 1.
MCPTT user 1 is the "listening" user at MCPTT client 1, and MCPTT user 2 is the "listened to" user at MCPTT client 2.
MCPTT client 2 is not already engaged in an MCPTT Private Call or an MCPTT Group Call.
MCPTT client 2 initiates a locally initiated ambient listening call by sending the ambient listening call request to the MCPTT server. The locally initiated ambient listening call type is included.
The MCPTT server performs an authorization check for the authorized user 2 for the locally initiated ambient listening call. If authorization fails, the MCPTT server provides a failure response to MCPTT client 2.
Figure 10.14.3.3-1 illustrates the information flow for ambient listening call release - server initiated when trigger by the MCPTT administrator. This procedure is applied for both remotely initiated ambient listening call and the locally initiated ambient listening call.
Pre-conditions:
MCPTT client 1 is the MCPTT client of the authorized user, who initiated the ambient listening call at MCPTT client 2.
There is an ongoing ambient listening call between MCPTT client 2 and MCPTT client 1.
MCPTT user 1 is the current user at MCPTT client 1 who is listening, and MCPTT user 2 is the current user at MCPTT client 2 who is being listened to.
The MCPTT server sends an ambient listening call release notification to MCPTT client 1 together with a reason code identifying that the call was released.
Figure 10.14.3.4-1 illustrates the information flow for ambient listening call release - "listening" user initiated. This procedure is applied for both remotely initiated ambient listening call and the locally initiated ambient listening call.
Pre-conditions:
MCPTT client 1 is the MCPTT client of the authorized user, who is authorized to release the ambient listening call at MCPTT client 2.
There is an ongoing ambient listening call between MCPTT client 2 and MCPTT client 1.
MCPTT user 1 is the "listening" user at MCPTT client 1, and MCPTT user 2 is the "listened to"user at MCPTT client 2.
The authorized user 1 at MCPTT client 1 initiates the ambient listening call release by sending an ambient listening call release request to the MCPTT server.
Figure 10.14.3.5-1 illustrates the information flow for ambient listening call release - "listened to" user initiated. This procedure is only applied for the locally initiated ambient listening call.
Pre-conditions:
There is an ongoing ambient listening call between MCPTT client 1 and MCPTT client 2.
MCPTT user 1 is the "listening" user at MCPTT client 1, and MCPTT user 2 is the "listened to" user at MCPTT client 2.
MCPTT client 2 is the MCPTT client of the authorized user, who is authorized to release the locally initiated ambient listening call at MCPTT client 2.
The authorized user 2 at MCPTT client 2 initiates the ambient listening call release by sending an ambient listening call release request to the MCPTT server.
Figure 10.15.3-1 describes the basic procedure for the MCPTT client initiating MCPTT first-to-answer call. The flow may use a floor request in the MCPTT call request indicating that the originator will be given the floor when the call starts and eliminates the need for a separate initial floor request message during media plane establishment. Alternatively, the call initiation may be sent without the floor request, which allows the called party to request the floor first. For a MCPTT first-to-answer call without floor control, floor control is not established.
Figure 10.15.3-1 also describes the handling of private calls when a functional alias replaces the MCPTT ID as target address. A functional alias can be simultaneously used by more than one MCPTT user, i.e. multiple MCPTT clients can activate the same functional alias.
This element indicates whether floor control will be used for the private call
SDP offer
O
Media parameters of MCPTT client
Implicit floor request
O
An indication that the user is also requesting the floor
Location information
O
Location of the calling party
NOTE:
At least one identity shall be present. If both are present the MCPTT ID list shall be used to route the call request and the functional alias is just for information.
All clients are served by the primary MCPTT service provider in Figure 10.15.3-1.
Pre-conditions:
The calling MCPTT user has selected first-to-answer call.
MCPTT clients 1 to n are registered and their respective users, MCPTT user 1 to MCPTT user n, are authenticated and authorized to use the MCPTT service, as per procedure in subclause 10.2.
MCPTT clients 2 to n have activated the same functional alias.
The MCPTT server has subscribed to the MCPTT functional alias controlling server within the MC system for functional alias activation/de-activation updates.
MCPTT user at MCPTT client 1 would like to establish a MCPTT first-to-answer call indicating a set of potential target recipients or by calling a functional alias. For a MCPTT first-to-answer call with floor control, floor control is to be established. For first-to-answer call without floor control, both users will have the ability to transmit without floor arbitration.
MCPTT client 1 sends an MCPTT first-to-answer call request including a set of potential target recipients to the MCPTT server (via the SIP core as defined in TS 23.228), using either a list of MCPTT IDs or a functional alias. The MCPTT first-to-answer call request contains the MCPTT ID and may contain the functional alias of originating user and an SDP offer containing one or more media types. The MCPTT first-to-answer call request may also contain a data element that indicates that MCPTT client 1 is requesting the floor, for a first-to-answer call with floor control. The MCPTT client 1 includes a first-to-answer call indication that the call is to be established only to the first answering user.
The MCPTT server confirms that MCPTT users are authorized for the call and whether the MCPTT user at MCPTT client 1 is authorized to initiate a first-to-answer call. The MCPTT server checks whether the provided functional alias of the calling user, if present, can be used and has been activated for the MCPTT user. If a functional alias is present, the MCPTT server shall also check whether MCPTT client 1 is allowed to use the functional alias of MCPTT client 2 (to MCPTT client n) to setup a private call and whether MCPTT client 2 (to MCPTT client n) is (are) allowed to receive a private call from MCPTT client 1 using a functional alias.
The MCPTT server determines the list of MCPTT users to send MCPTT first-to-answer call request, based on a set of potential target recipients obtained from the request from MCPTT client 1. Alternatively, when a functional alias is used as target address, the MCPTT server resolves the functional alias to a corresponding list of related MCPTT IDs of MCPTT client 2 to MCPTT client n who have activated the functional alias. The functional alias must have been activated to identify the MCPTT IDs of the called users.
The MCPTT server 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 and sends similar MCPTT first-to-answer call request to each potential target recipient, including the MCPTT ID and, if present, the functional alias of the calling MCPTT user at MCPTT client 1. If one or more called MCPTT users have registered to the MCPTT service with multiple MCPTT UEs and has designated the MCPTT UE for receiving the calls, then the incoming MCPTT first-to-answer call request is delivered only to the designated MCPTT UE. Otherwise MCPTT first-to-answer call request may be delivered to all the registered MCPTT UEs. If a functional alias is present and more than one MCPTT client has activated that functional alias, then the MCPTT server sends an MCPTT first-to-answer call request to each MCPTT client.
The MCPTT server sends an MCPTT first-to-answer call response to MCPTT client 1 indicating that MCPTT user at MCPTT client 2 has accepted the call, including the accepted media parameters.
The media plane for communication is established. Either user can transmit media individually when using floor control. For successful call establishment for first-to-answer call with floor request from MCPTT client 1, the floor participant associated with MCPTT client 1 is granted the floor initially. At the same time the floor participant associated with MCPTT client 2 is informed that the floor is taken. For a first-to-answer call without floor control both users are allowed to transmit simultaneously.
A remotely initiated MCPTT call allows an authorized user to cause a remote MCPTT UE to initiate a call by itself, without its user explicitly initiating the call.
Table 10.16.2.1-1 describes the information flow remotely initiated MCPTT call request from the MCPTT client to the MCPTT server and from the MCPTT server to MCPTT client.
Table 10.16.2.2-1 describes the information flow remotely initiated MCPTT call response from the MCPTT client to the MCPTT server and from the MCPTT server to MCPTT client.
The remotely initiated MCPTT call request procedure includes the initial remotely initiated MCPTT call request from the MCPTT user to the remote UE and either the MCPTT private call procedures or the MCPTT group call procedures originating at the remote UE.
Procedures in Figure 10.16.3.1-1 show the signalling control plane procedures for the MCPTT client initiating a remotely initiated MCPTT call request with the chosen MCPTT user.
Pre-conditions:
If the MCPTT user on MCPTT client 1 wants the resulting remotely initiated MCPTT call to be:
an MCPTT group call, then MCPTT user 2 on MCPTT client 2 is an affiliated MCPTT group member of the MCPTT group that is the target of the remotely initiated MCPTT call.
an MPCTT private call, then the MCPTT user 2 on MCPTT client 2 is permitted to initiate an MCPTT private call to the identified MCPTT user.
MCPTT server checks whether the MCPTT user at MCPTT client 1 is authorized to initiate a remotely initiated MCPTT call request. If the resulting of this request is to initiate a group call, MCPTT client 1 is authorized to remotely initiate the MCPTT call request, and if MCPTT client 2 is a member of the group, the MCPTT server implicitly affiliates the MCPTT user 2 on MCPTT client 2 to the MCPTT group if the MCPTT client 2 is not already affiliated and notifies the MCPTT client 2 of this affiliation change.
After receiving the remotely initiated MCPTT call response from MCPTT client 2, the MCPTT server informs the MCPTT client 1 about successful remotely initiated MCPTT call request.
Based on the received information the MCPTT client 2 initiates an MCPTT call (either an MCPTT group call or an MCPTT private call) using the normal MCPTT call establishment procedures (clause 10.6.2.3.1.1.2 or clause 10.7.2.2) with implicit floor request and other call set up parameters if received in the remotely initiated call request. The MCPTT call request may include the additional information such as indication of whether the call initiation is due to receiving of remotely initiated call request.
If the remotely initiated call is a group call, then when the ongoing MCPTT group call is terminated, the MCPTT server de-affiliates the MCPTT user 2 on MCPTT client 2 from the MCPTT group if MCPTT client 2 is implicitly affiliated as defined in the step 3 above (the de-affiliation is not shown in the figure for simplicity).
The result of these procedures is an on-going MCPTT (group or private) call which includes MCPTT client 1.
An MCPTT user may be authorized to use the MCPTT service from multiple MCPTT UEs as per the procedure in subclause 10.2.
If an MCPTT server receives a service authorization request for an MCPTT user who is previously MCPTT service authorized on another MCPTT UE, then the MCPTT server shall process this service authorization request as described in subclause 10.2. In the MCPTT service authorization response to the MCPTT user, the MCPTT server shall also indicate that the MCPTT user is already MCPTT service authorized from another MCPTT UE.
The MCPTT service shall support the procedures and related information flows as specified in subclauses 10.13.10 of TS 23.280 with the following clarifications: