10.5 MCPTT service

23.1803GPPMission critical services support in the Isolated Operation for Public Safety (IOPS) mode of operationRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

10.5.1 IOPS group call (IP connectivity functionality)

10.5.1.1 General

The support of MCPTT group calls based on the IP connectivity functionality in the IOPS mode of operation enables that the service is provided by the MCPTT clients over the IOPS MC connectivity function. The IOPS MC connectivity function provides IP connectivity for the communication among MCPTT users.

IOPS group calls based on the IP connectivity functionality can use pre-configured information provided to MCPTT clients prior to the IOPS group call. Therefore, when a MCPTT client initiates an IOPS group call it uses the pre-configured IOPS group IP multicast address associated to the target IOPS MCPTT group ID to establish the IOPS group call based on the IP connectivity functionality. The related packets, i.e. signalling and media, of the IOPS group call are transmitted to the IOPS MC connectivity function for distribution to the corresponding discovered MC users of the target IOPS MCPTT group.

The IOPS MC connectivity function can distribute the group session packets to the discovered MC users over MBMS bearers as described in clause 10.4.5.

The IOPS MC connectivity function can also replicate and distribute the group session packets over unicast transmissions to MCPTT UEs associated to the target IOPS MCPTT group. MCPTT UEs receiving the group session packets are associated to discovered MC users that included the target IOPS MCPTT group ID in the IOPS discovery request, as described in clause 10.5.2.3.

The following clauses specify the IOPS group call procedures and information flows for the IP connectivity functionality in the IOPS mode of operation.

10.5.1.2 Information flows

10.5.1.2.1 IOPS group call announcement

Table 10.5.1.2.1-1 describes the information flow for the IOPS group call announcement from one MCPTT client to other MCPTT clients. The packet(s) carrying the IOPS group call announcement are transmitted from the originating MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT clients.

Table 10.5.1.2.1-1: IOPS group call announcement

Information Element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT group ID	M	The IOPS MCPTT group ID on which the call is to be conducted
SDP offer	M	Media parameters of the MCPTT client
Announcement period	M	Period of the group call announcement
Encryption parameters	O	Encryption parameters to be used for the call, if the call is to be encrypted
Confirm mode indicator	O	Indicates whether the MCPTT group call is to be confirmed
Emergency indicator	O	Indicates that the MCPTT group call is an MCPTT emergency call

10.5.1.2.2 IOPS group call response

Table 10.5.1.2.2-1 describes the information flow for the IOPS group call response from one MCPTT client to other MCPTT clients. The packet(s) carrying the IOPS group call response is transmitted from the called MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT clients.

Table 10.5.1.2.2-1: IOPS group call response

Information Element	Status	Description
IOPS MCPTT ID	M	The identity of the called party
IOPS MCPTT group ID	M	The IOPS MCPTT group ID of the group on which the call is requested
SDP answer	M	Media parameters selected
Result	M	Result of the group call announcement (success or failure)

10.5.1.2.3 IOPS emergency group call upgrade

Table 10.5.1.2.3-1 describes the information flow for the IOPS emergency group call upgrade from one MCPTT client to other MCPTT clients. The packet(s) carrying the IOPS emergency group call upgrade are transmitted from the originating MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT clients.

Table 10.5.1.2.3-1: IOPS emergency group call upgrade

Information Element	Status	Description
IOPS MCPTT ID	M	The identity of the upgrading MC user
IOPS MCPTT group ID	M	The IOPS MCPTT group ID on which the call is to be upgraded to emergency call

10.5.1.2.4 IOPS emergency group call state cancel

Table 10.5.1.2.4-1 describes the information flow for the IOPS emergency group call state cancel from one MCPTT client to other MCPTT clients. The packet(s) carrying the IOPS emergency group call state cancel are transmitted from the originating MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT clients.

Table 10.5.1.2.4-1: IOPS emergency group call state cancel

Information Element	Status	Description
IOPS MCPTT ID	M	The identity of the cancelling MC user
IOPS MCPTT group ID	M	The IOPS MCPTT group ID on which the emergency call state is to be cancelled

10.5.1.3 IOPS group call setup

The procedure in figure 10.5.1.3-1 illustrates the procedure for an IOPS MCPTT group call establishment based on the IP connectivity functionality. The procedure describes how an MCPTT client initiates and establishes an IOPS MCPTT group call with other MCPTT clients.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs;

– The IOPS MCPTT group ID and its associated IOPS group IP multicast address are pre-configured in the MCPTT clients;

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality;

– MCPTT users affiliated to the target IOPS MCPTT group are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality;

– The IOPC MC connectivity function may have established an MBMS bearer and announced it to the MCPTT clients;

– MCPTT client 1 may have retrieved group connectivity information from the IOPS connectivity client related to the target IOPS MCPTT group;

– MCPTT clients 1, 2 … n are configured within the same IOPS MCPTT group.

Figure 10.5.1.3-1: IOPS group call setup based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS group call with a specific IOPS MCPTT group based on the IP connectivity functionality.

2. The MCPTT client 1 sends an IOPS group call announcement to the target IOPS MCPTT group. The MCPTT client 1 transmits the group session packets carrying the IOPS group call announcement to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

4. The IOPS MC connectivity function distributes the group session packets carrying the IOPS group call announcement to the MCPTT clients from the target IOPS MCPTT group.

5. The MCPTT clients receiving the IOPS group call announcement join the IOPS group call and notify the target MCPTT users about the IOPS group call.

6. If confirm mode indication is included in the IOPS group call announcement, the receiving MCPTT clients respond to the IOPS MCPTT group indicating the result of the establishment of the announced IOPS group call. The receiving MCPTT clients transmit the group session packets carrying the IOPS group call response to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

NOTE 1: Step 6 can also occur prior to step 5.

8. The IOPS MC connectivity function distributes the group session packets carrying the IOPS group call response to the MCPTT clients from the target IOPS MCPTT group. The MCPTT clients recognize the IOPS group call originator through the IOPS group call announcement and can check the participants of the IOPS group call through the received response message.

9. The MCPTT clients have successfully established the IOPS group call with floor control based on the IP connectivity functionality.

NOTE 2: Due to the movement of the participants (in and out of the IOPS EPS coverage) during the IOPS group call, the IOPS group call announcement is periodically sent by the MCPTT client 1.

NOTE 3: The participating MCPTT clients do not need to respond to the periodic IOPS group call announcement.

10.5.1.4 IOPS emergency group call

The procedure in figure 10.5.1.4-1 illustrates the procedure for an IOPS MCPTT emergency group call establishment based on the IP connectivity functionality. The IOPS emergency group call is a special case of the IOPS group call setup procedure described in clause 10.5.1.3, wherein the IOPS group call announcement contains an indication that the IOPS group call is an IOPS emergency group call. The group call participants can become aware of the IOPS MCPTT group’s in-progress emergency state based on the emergency indicator.

When an MCPTT client intends to initiate an IOPS emergency group call, the MCPTT client can request higher priority from the IOPS MC connectivity function via the IOPS discovery request.

An IOPS group call in-progress can be upgraded to an IOPS emergency group call by including the emergency indicator within the periodic IOPS group call announcement. An IOPS group call in-progress can also be upgraded by a participating MCPTT client by sending an IOPS emergency group call upgrade to the IOPS group.

The MCPTT user who initiated an IOPS emergency group call, or upgraded an IOPS group call to an emergency group call, or an authorized user can cancel the emergency state of the group call by sending an IOPS emergency group call state cancel to the IOPS MCPTT group. The emergency state of the IOPS group call remains active until the emergency group call ends or the in-progress emergency state is cancelled.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs;

– The IOPS MCPTT group ID and its associated IOPS group IP multicast address are pre-configured in the MCPTT clients;

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality;

– MCPTT users affiliated to the target IOPS MCPTT group are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality;

– The IOPC MC connectivity function may have established an MBMS bearer and announced it to the MCPTT clients;

– MCPTT client 1 may have retrieved group connectivity information from the IOPS connectivity client related to the target IOPS MCPTT group;

– MCPTT clients 1, 2 … n are configured within the same IOPS MCPTT group.

Figure 10.5.1.4-1: IOPS emergency group call setup based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS emergency group call with a specific IOPS MCPTT group based on the IP connectivity functionality.

NOTE 1: The MCPTT client 1 may have previously requested higher priority from the IOPS MC connectivity function using the IOPS discovery request.

2. The MCPTT client 1 sends an IOPS group call announcement to the target IOPS MCPTT group. The announcement contains an indication that the call is an IOPS emergency group call. The MCPTT client 1 transmits the group session packets carrying the IOPS group call announcement to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

3. The IOPS MC connectivity function determines that the received packets correspond to a group session targeting a specific IOPS MCPTT group. The IOPS MC connectivity function decides to distribute the received group session packets to the target MCPTT clients over MBMS and/or unicast transmissions. If the MCPTT client 1 requested a priority state from the IOPS MC connectivity function, the IOPS MC connectivity function distributes the group session packets with higher priority.

4. The IOPS MC connectivity function distributes the group session packets carrying the IOPS group call announcement to the MCPTT clients from the target IOPS MCPTT group.

5. The MCPTT clients receiving the IOPS group call announcement with an emergency indicator join the IOPS emergency group call and notify the target MCPTT users about the IOPS emergency group call. The IOPS MCPTT group’s emergency state is defined.

NOTE 2: Whilst the emergency state of the IOPS group call remains active, other participating MCPTT clients of the group call may also request higher priority from the IOPS MC connectivity function using the IOPS discovery request.

6. If confirm mode indication is included in the IOPS group call announcement, the receiving MCPTT clients respond to the IOPS MCPTT group indicating the result of the establishment of the announced IOPS emergency group call. The receiving MCPTT clients transmit the group session packets carrying the IOPS group call response to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

NOTE 3: Step 6 can also occur prior to step 5.

7. The IOPS MC connectivity function determines that the received packets correspond to a group session targeting a specific IOPS MCPTT group. The IOPS MC connectivity function decides to distribute the received group session packets to the target MCPTT clients over MBMS and/or unicast transmissions. If any participating MCPTT client of the group call requested a priority state from the IOPS MC connectivity function, the IOPS MC connectivity function distributes the group session packets with higher priority.

8. The IOPS MC connectivity function distributes the group session packets carrying the IOPS group call response to the MCPTT clients from the target IOPS MCPTT group. The MCPTT clients recognize the IOPS emergency group call originator through the IOPS group call announcement and can check the participants of the IOPS group call through the received response message.

9. The MCPTT clients have successfully established the IOPS emergency group call based on the IP connectivity functionality.

NOTE 4: Due to the movement of the participants (in and out of the IOPS EPS coverage) during the IOPS emergency group call, the IOPS group call announcement is periodically sent by the MCPTT client 1.

NOTE 5: The participating MCPTT clients do not need to respond to the periodic IOPS group call announcement.

10.5.1.5 IOPS group call release

Each MCPTT client may release itself from an ongoing IOPS group call without the transmission of any signalling if the call has been inactive for a specific duration.

NOTE: Inactivity time can be set according to the policy of the MCPTT service provider.

10.5.2 IOPS private call (IP connectivity functionality)

10.5.2.1 General

The support of MCPTT private calls based on the IP connectivity functionality in the IOPS mode of operation enables that the service is provided by the MCPTT clients over the IOPS MC connectivity function. The IOPS MC connectivity function provides IP connectivity for the communication among MCPTT users.

When an MCPTT user wants to communicate with a specific target MCPTT user based on the IP connectivity functionality, the MCPTT client retrieves the connectivity information of the target MCPTT user (i.e. the MCPTT UE’s IP address) from the IOPS connectivity client. Then, the MCPTT clients enable establishing the IOPS private call over the IOPS MC connectivity function. The related session packets, i.e. signalling and media, of the IOPS private call are transmitted to the IOPS MC connectivity function addressing the corresponding target MCPTT UE’s IP address.

NOTE: The IOPS connectivity client can only provide connectivity information of the target MCPTT user if it is already available (see clauses 10.3 on IOPS subscription and notification procedures).

The IOPS MC connectivity function distributes the received session packets over unicast transmissions to the target MCPTT client.

IOPS private calls can be setup in two different commencement modes, automatic commencement mode and manual commencement mode.

The following clauses specify the IOPS private call procedures and information flows for the IP connectivity functionality in the IOPS mode of operation.

10.5.2.2 Information flows

10.5.2.2.1 IOPS call setup request

Table 10.5.2.2.1-1 describes the information flow for the IOPS call setup request from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS call setup request are transmitted from the calling MCPTT client to the IOPS MC connectivity function for distribution to the called MCPTT client.

Table 10.5.2.2.1-1: IOPS call setup request

Information element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT ID	M	The identity of the called party
SDP offer for the IOPS private call	M	SDP with media information offered by (to) client
Location information	O	Location of the calling party
Requested commencement mode	O	An indication that is included if the user is requesting a particular commencement mode
Implicit floor request	O	An indication that the user is also requesting the floor.
Emergency indicator	O	Indicates that the MCPTT private call is an MCPTT emergency call

10.5.2.2.2 IOPS call setup response

Table 10.5.2.2.2-1 describes the information flow for the IOPS call setup response from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS call setup response are transmitted from the called MCPTT client to the IOPS MC connectivity function for distribution to the calling MCPTT client.

Table 10.5.2.2.2-1: IOPS call setup response

Information element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT ID	M	The identity of the called party
SDP answer for private call	M	SDP with media parameters selected
Acceptance confirmation	O	An indication whether the user has positively accepted the call.

10.5.2.2.3 IOPS MCPTT ringing

Table 10.5.2.2.3-1 describes the information flow for the IOPS MCPTT ringing from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS MCPTT ringing are transmitted from the called MCPTT client to the IOPS MC connectivity function for distribution to the calling MCPTT client.

Table 10.5.2.2.3-1: IOPS MCPTT ringing information elements

Information Element	Status	Description
IOPS MCPTT ID	M	The MCPTT ID of the calling party
IOPS MCPTT ID	M	The MCPTT ID of the called party
Ringing indication	O	Indication to the caller.

10.5.2.2.4 IOPS call release request

Table 10.5.2.2.4-1 describes the information flow for the IOPS call release request from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS call release request are transmitted from one MCPTT client to the IOPS MC connectivity function for distribution to the other MCPTT client.

Table 10.5.2.2.4-1: IOPS call release request

Information element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT ID	M	The identity of the called party
MCPTT private call release reason	O	This element indicates the reason for the private call release. e.g., Originating client requested.

10.5.2.2.5 IOPS call release response

Table 10.5.2.2.5-1 describes the information flow for the IOPS call release response from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS call release response are transmitted from one MCPTT client to the IOPS MC connectivity function for distribution to the other MCPTT client.

Table 10.5.2.2.5-1: IOPS call release response

Information element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT ID	M	The identity of the called party

10.5.2.2.6 IOPS emergency private call upgrade

Table 10.5.2.2.6-1 describes the information flow for the IOPS emergency private call upgrade from one MCPTT client to another MCPTT client. The packet(s) carrying the IOPS emergency private call upgrade are transmitted from the originating MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT client.

Table 10.5.2.2.6-1: IOPS emergency private call upgrade

Information Element	Status	Description
IOPS MCPTT ID	M	The identity of the calling party
IOPS MCPTT ID	M	The identity of the called party

10.5.2.3 IOPS private call setup in automatic commencement mode procedure

The procedure in figure 10.5.2.3-1 is the basic procedure for an MCPTT client initiating the establishment of an IOPS MCPTT private call with a target MCPTT client based on the IP connectivity functionality.

The procedure focuses on the case of an IOPS MCPTT private call using an automatic commencement mode.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs.

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality

– The MCPTT users are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality.

– MCPTT clients have retrieved connectivity information from target MCPTT users.

Figure 10.5.2.3-1: IOPS private call setup in automatic commencement mode based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS private call with the MCPTT user at MCPTT client 2 based on the IP connectivity functionality.

2. The MCPTT client 1 retrieves the connectivity information of the target MCPTT user from the IOPS connectivity client 1 (not shown in figure) and sends an IOPS call setup request towards the MCPTT client 2. The MCPTT client 1 transmits the session packets carrying the IOPS call setup request to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 2’s IP address.

The IOPS call setup request contains an SDP offer, an automatic commencement mode indication, and an element that indicates that MCPTT client 1 is requesting the floor. The IOPS private call request may include location information.

4. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup request to the MCPTT client 2.

5. The MCPTT client 2 notifies the target MCPTT user about the incoming IOPS private call.

6. The receiving MCPTT client 2 accepts the IOPS private call automatically, and an IOPS call setup response indicating the successful call establishment is sent to MCPTT client 1. The MCPTT client 2 transmits the session packet(s) carrying the IOPS call setup response to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 1’s IP address.

If MCPTT client 2 rejected the incoming call, the MCPTT client 2 sends an IOPS call setup response indicating the failure reason to the MCPTT client 1.

NOTE: Step 6 can also occur prior to step 5.

8. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup response to the MCPTT client 1.

9. The MCPTT client 1 and the MCPTT client 2 have successfully established the IOPS private call with floor control based on the IP connectivity functionality. The MCPTT client 1 is automatically granted the floor.

10.5.2.4 IOPS private call setup in manual commencement mode procedure

The procedure in figure 10.5.2.4-1 focuses on the case where an MCPTT user is initiating an IOPS MCPTT private call for communicating with another MCPTT user using a manual commencement mode. The IOPS MCPTT private call is based on the IP connectivity functionality.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs.

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality.

– The MCPTT users are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality.

– MCPTT clients have retrieved connectivity information from target MCPTT users.

Figure 10.5.2.4-1: IOPS private call setup in manual commencement mode based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS MCPTT private call with the MCPTT user at MCPTT client 2 based on the IP connectivity functionality.

The IOPS call setup request contains an SDP offer, a manual commencement mode indication, and an element that indicates that MCPTT client 1 is requesting the floor. The IOPS private call request may include location information.

4. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup request to the MCPTT client 2.

5. The MCPTT client 2 notifies the target MCPTT user about the incoming IOPS private call.

6. The MCPTT client 2 sends an IOPS MCPTT ringing message to the MCPTT client 1. The MCPTT client 2 transmits the session packet(s) carrying the IOPS MCPTT ringing to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 1’s IP address.

NOTE 1: Step 6 can also occur prior to step 5.

8. The IOPS MC connectivity function distributes the session packets carrying the IOPS MCPTT ringing to the MCPTT client 1.

9. The MCPTT user at the MCPTT client 2 has accepted the call using manual commencement mode (i.e., it has taken some action to accept it via the user interface). The MCPTT user may also reject or fail to answer the incoming call.

NOTE 2: Step 9 can also occur at any time between steps 6 and 8.

10. The MCPTT client 2 sends an IOPS call setup response indicating the successful call establishment to the MCPTT client 1. If the MCPTT client 2 rejected the call or the MCPTT user 2 rejected or failed to answer the incoming call, the MCPTT client 2 sends an IOPS call setup response indicating the failure reason to the MCPTT client 1. The MCPTT client 2 transmits the session packet(s) carrying the IOPS call setup response to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 1’s IP address.

11. The IOPS MC connectivity function receives the session packets addressing the MCPTT UE 1’s IP address. The IOPS MC connectivity function checks if the MCPTT UE 1’s IP address corresponds to a discovered MC user in order to distribute the received session packets. If it does, the IOPS MC connectivity function distributes the received session packets to the MCPTT client 1 over unicast transmissions.

12. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup response to the MCPTT client 1.

13. The MCPTT client 1 and the MCPTT client 2 have successfully established the IOPS private call with floor control based on the IP connectivity functionality. The MCPTT client 1 is automatically granted the floor.

10.5.2.5 IOPS private call release

The procedure in figure 10.5.2.5-1 focuses on the case where an MCPTT client is requesting to release an ongoing IOPS MCPTT private call based on the IP connectivity functionality. Either MCPTT client can initiate the call release procedure.

Pre-conditions:

– Two MCPTT users are currently engaged in an IOPS MCPTT private call based on the IP connectivity functionality.

Figure 10.5.2.5-1: IOPS private call release based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS MCPTT private call release to the MCPTT user at MCPTT client 2 based on the IP connectivity functionality.

2. The MCPTT client 1 retrieves the connectivity information of the target MCPTT user from the IOPS connectivity client 1 (not shown in figure) and sends an IOPS call release request towards the MCPTT client 2. The MCPTT client 1 transmits the session packets carrying the IOPS call release request to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 2’s IP address.

4. The IOPS MC connectivity function distributes the session packets carrying the IOPS call release request to the MCPTT client 2.

5. The MCPTT client 2 notifies the MCPTT user about the IOPS private call release.

6. The MCPTT client 2 sends an IOPS call release response indicating the successful call release to the MCPTT client 1. The MCPTT client 2 transmits the session packet(s) carrying the IOPS call release response to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 1’s IP address.

NOTE: Step 6 can also occur prior to step 5.

8. The IOPS MC connectivity function distributes the session packets carrying the IOPS call release response to the MCPTT client 1.

9. The MCPTT client 1 and the MCPTT client 2 release all associated call resources from the private call communication based on the IP connectivity functionality.

10.5.2.6 IOPS emergency private call

The procedure in figure 10.5.2.6-1 is the basic procedure for an MCPTT client initiating the establishment of an IOPS emergency private call with a target MCPTT client based on the IP connectivity functionality. The IOPS emergency private call is a special case of the IOPS private call setup procedures described in clause 10.5.2.3, wherein the IOPS call setup request contains an indication that the IOPS private call is an IOPS emergency private call. The called MCPTT user can become aware of the emergency state of the calling MCPTT user based on the emergency indicator.

When an MCPTT client intends to initiate an IOPS emergency private call, the MCPTT client can request higher priority from the IOPS MC connectivity function via the IOPS discovery request.

For the case of an IOPS private call in-progress, either call participant can upgrade the call to an IOPS emergency private call by sending an IOPS emergency private call upgrade.

The emergency state of the call remains until the emergency call ends.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs.

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality

– The MCPTT users are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality.

– MCPTT clients have retrieved connectivity information from target MCPTT users.

Figure 10.5.2.6-1: IOPS emergency private call setup based on the IP connectivity functionality

1. The MCPTT user at MCPTT client 1 would like to initiate an IOPS emergency private call with the MCPTT user at MCPTT client 2 based on the IP connectivity functionality.

NOTE 1: The MCPTT client 1 may have previously requested higher priority from the IOPS MC connectivity function using the IOPS discovery request.

2. The MCPTT client 1 retrieves the connectivity information of the target MCPTT user from the IOPS connectivity client 1 (not shown in figure) and sends an IOPS call setup request towards the MCPTT client 2. The request contains an indication that the call is an IOPS emergency private call. The MCPTT client 1 transmits the session packets carrying the IOPS call setup request to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 2’s IP address.

3. The IOPS MC connectivity function receives the session packets addressing the MCPTT UE 2’s IP address. The IOPS MC connectivity function checks if the MCPTT UE 2’s IP address corresponds to a discovered MC user in order to distribute the received session packets. If it does, the IOPS MC connectivity function distributes the received session packets to the target MCPTT client over unicast transmissions. If the MCPTT client 1 requested a priority state from the IOPS MC connectivity function, the IOPS MC connectivity function distributes the session packets with higher priority.

4. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup request to the MCPTT client 2.

5. The MCPTT client 2 notifies the target MCPTT user about the incoming IOPS emergency private call.

6. The receiving MCPTT client 2 accepts the IOPS emergency private call and an IOPS call setup response indicating the successful call establishment is sent to MCPTT client 1. The MCPTT client 2 transmits the session packet(s) carrying the IOPS call setup response to the IOPS MC connectivity function for distribution to the corresponding target MCPTT UE 1’s IP address.

NOTE 2: Whilst the IOPS emergency private call is in progress, the MCPTT client 2 may also request higher priority from the IOPS MC connectivity function using the IOPS discovery request.

NOTE 3: Step 6 can also occur prior to step 5.

7. The IOPS MC connectivity function receives the session packets addressing the MCPTT UE 1’s IP address. The IOPS MC connectivity function checks if the MCPTT UE 1’s IP address corresponds to a discovered MC user in order to distribute the received session packets. If it does, the IOPS MC connectivity function distributes the received session packets to the target MCPTT client over unicast transmissions. If any participating MCPTT client of the call requested a priority state from the IOPS MC connectivity function, the IOPS MC connectivity function distributes the session packets with higher priority.

8. The IOPS MC connectivity function distributes the session packets carrying the IOPS call setup response to the MCPTT client 1.

9. The MCPTT client 1 and the MCPTT client 2 have successfully established the IOPS emergency private call based on the IP connectivity functionality.

10.5.3 IOPS floor control (IP connectivity functionality)

10.5.3.1 General

For MCPTT calls based on the IP connectivity functionality in the IOPS mode of operation, floor control is performed by using floor control messages among the MCPTT clients without a centralized MCPTT server. The MCPTT client can transmit voice packets over the IOPS MC connectivity function once it is granted the right to speak, either locally in the UE or by the reception of a floor granted message from another MCPTT client.

The MCPTT client currently speaking performs the temporary floor arbitrator during speaking since there is no centralized MCPTT floor control server. The floor arbitrator controls the floor whether or not queue is supported, and when floor is requested with override. If queue is supported, the MCPTT client performing floor arbitrator grants the right to speak to the next speaker and transfers the floor arbitrator role after completing the voice transfer and releasing the floor. For IOPS group calls, the floor arbitrator also transfers the floor control queue when granting the floor. The next MCPTT client receiving the right to speak becomes the new floor arbitrator and, for IOPS group calls, has the floor control queue.

For IOPS group calls, the group session packets carrying the floor control messages can be transmitted by the IOPS MC connectivity function over MBMS transmissions and can be monitored by all the members from the target IOPS MCPTT group.

The following clauses specify the floor control procedures and information flows for IOPS private calls and IOPS group calls based on the IP connectivity functionality in the IOPS mode of operation.

10.5.3.2 Information flows

10.5.3.2.1 IOPS floor request

Table 10.5.3.2.1-1 describes the information flow for the IOPS floor request, from the floor participant to another floor participant, which is used to request the floor for media transfer. The packet(s) carrying the IOPS floor request are transmitted from the requesting MCPTT client to the IOPS MC connectivity function for distribution to the target MCPTT client.

Table 10.5.3.2.1-1: IOPS floor request

Information element	Status	Description
IOPS MCPTT ID	M	Requester identity
Floor priority	M	Priority of the request

10.5.3.2.2 IOPS floor taken

Table 10.5.3.2.2-1 describes the information flow for the IOPS floor taken, from the floor participant to the floor participant, which is used to indicate the floor is granted to an MCPTT user. The packet(s) carrying the IOPS floor taken are transmitted from the originating MCPTT client to the IOPS MC connectivity function for distribution to target MCPTT client.

Table 10.5.3.2.2-1: IOPS floor taken

Information element	Status	Description
IOPS MCPTT ID	M	Identity for the granted party
Acknowledgement required	O	Indicates if acknowledgement from the floor participant is required

10.5.3.3 IOPS floor control during silence

If a floor arbitrator does not exist, figure 10.5.3.3-1 shows the successful high level floor control procedure during periods when there is no detectable talker in an IOPS group call based on the IP connectivity functionality.

NOTE 1: The description also applies to IOPS private calls.

Pre-conditions:

– MCPTT user profile used for the IOPS mode of operation is pre-provisioned in the MCPTT UEs.

– MCPTT users have an active PDN connection to the IOPS MC connectivity function for the communication based on the IP connectivity functionality

– The IOPS MCPTT group ID and its associated IOPS group IP multicast address are pre-configured in the MCPTT clients (for the case of an IOPS group call)

– The IOPC MC connectivity function may have established an MBMS bearer and announced it to the MCPTT clients

– The MCPTT users are discovered by the IOPS MC connectivity function supporting the IP connectivity functionality.

– MCPTT clients has retrieved connectivity information from the target MCPTT user (for the case of an IOPS private call).

– An IOPS private call or IOPS group call based on the IP connectivity functionality has been established. No participant is currently talking (i.e. the floor is idle) and no floor arbitrator is identified.

Figure 10.5.3.3-1: Successful floor taken flow in an IOPS group call based on the IP connectivity functionality (no floor contention)

1. The MCPTT client 1 sends the IOPS floor request message to the target IOPS MCPTT group. The MCPTT client 1 transmits the group session packets carrying the IOPS floor request message to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

2. The IOPS MC connectivity function determines that the received packets correspond to a group session targeting a specific IOPS MCPTT group. The IOPS MC connectivity function decides distributing the received group session packets to the target MCPTT clients over MBMS and/or unicast transmissions.

3. The IOPS MC connectivity function distributes the group session packets carrying the IOPS floor request to the MCPTT clients from the target IOPS MCPTT group.

4. The MCPTT client 1 does not detect any floor contention. Floor contention occurs when multiple floor requests may exist simultaneously.

NOTE 2: The mechanism for detecting floor contention in the IOPS mode of operation is out of scope of the present document.

5. The MCPTT client 1 sends the IOPS floor taken message to the IOPS MCPTT group. The MCPTT client 1 transmits the group session packets carrying the IOPS floor taken message to the IOPS MC connectivity function for distribution to the corresponding IOPS group IP multicast address.

6. The IOPS MC connectivity function determines that the received packets correspond to a group session targeting a specific IOPS MCPTT group. The IOPS MC connectivity function decides distributing the received group session packets to the target MCPTT clients over MBMS and/or unicast transmissions.

7. The IOPS MC connectivity function distributes the group session packets carrying the IOPS floor taken message to the MCPTT clients from the target IOPS MCPTT group.

8. The MC user at MCPTT client 1 gets a notification that the IOPS floor request was successful (the floor has been granted).

NOTE 3: Step 8 can also occur prior to steps 6 and 7.

9. The MCPTT client 1 begins voice transmission with the target IOPS MCPTT group based on the IP connectivity functionality.