6.2 Transmission participant procedures

24.5813GPPMission Critical Video (MCVideo) media plane controlProtocol specificationRelease 18TS

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

6.2.1 Transmission participant procedures at MCVideo session initialization

Based on the negotiations during the call establishment specified in 3GPP TS 24.281 [2], a new instance of the ‘Transmission participant state transition diagram for basic transmission control operation’, as specified in clause 6.2.4 and a new instance of the ‘Transmission participant state transition diagram for basic reception control operation’ as specified in clause 6.2.5, shall be created for this call.

The SIP INVITE request sent by the application and signalling plane:

1. shall be regarded an implicit Transmission request when an implicit Transmission request is negotiated; and

2. shall not be regarded as an implicit Transmission request in case of a rejoin to an already on-going group call.

NOTE: The transmission participant can negotiate the use of prioritization of the Transmission Media Request message. In that case, the transmission participant can request permission to send media at a priority level that is either the same as or lower than the highest priority that was permitted to the participant in the MCVideo call initialization. If a transmission participant is authorized for pre-emptive priority in the MCVideo call it is good practise to always request permission to send RTP media packets at a priority level that is lower than pre-emptive priority unless the user explicitly requests to pre-empt the current RTP media packets sender.

6.2.2 Transmission participant procedures at MCVideo call release

The MCVideo call release (whether it is initiated by the transmission participant or transmission control server) is a two-step procedure.

Step 1 The transmission participant stops sending transmission control and reception control messages and the MCVideo client stops sending and receiving RTP media packets.

Step 2 When the application and signalling plane has determined that the MCVideo call is released, the corresponding instance of the ‘Transmission participant state transition diagram for basic transmission control operation’ as specified in clause 6.2.4 and the corresponding instance of the ‘Transmission participant state transition diagram for basic reception control operation’ as specified in clause 6.2.5 are terminated and the transmission participant releases all the used resources.

The user plane can initiate the release step 1, but the application and signalling plane always initiates the release step 2.

6.2.3 Transmission participant procedures at MCVideo call modification

Editor’s Note: It is FFS whether adding or removing media streams during an MCVideo call influences the transmission control procedures.

6.2.4 Transmission participant state transition diagram for basic transmission control operation

6.2.4.1 General

The transmission participant shall behave according to the state diagram and the state transitions specified in this clause.

Figure 6.2.4.1-1 shows the state diagram for ‘Transmission participant state transition diagram for basic transmission control operation’.

Figure 6.2.4.1-1: Transmission participant state transition diagram for basic transmission control operation.

State details are explained in the following clauses.

If a transmission control message arrives in a state where there is no specific procedure specified for received transmission control message, the transmission participant shall discard the transmission control message and shall remain in the current state.

NOTE: A badly formatted transmission control message received in any state is ignored by the transmission participant and does not cause any change of the current state.

6.2.4.2 State: ‘Start-stop’

6.2.4.2.1 General

When a new instance of the ‘Transmission participant state transition diagram for basic transmission control operation’ is initiated, before any transmission control related input is applied, the state machine is in ‘Start-stop’ state. Similarly when the call is released the state machine shall return to the ‘Start-Stop state.

6.2.4.2.2 MCVideo call initiated, originating MCVideo user

When a call is initiated as described in 3GPP TS 24.281 [2], the transmission participant:

1. shall create an instance of the ‘Transmission participant state transition diagram for basic transmission control operation’;

2. if the originating transmission participant receives a transmission control message before it receives the SIP 200 (OK) response, shall store the transmission control message;

NOTE: The originating transmission participant might receive a transmission control message before the SIP 200 (OK) response when initiating, joining or rejoining a call because of processing delays of the SIP 200 (OK) response in the SIP core.

3. if the established MCVideo call is a chat group call and the SIP INVITE request is not an implicit Transmission request, shall enter the ‘U: has no permission to transmit’ state;

4. if for the established MCVideo call the SIP INVITE request is an implicit Transmission request:

a. shall start timer T100 (Transmission Request) and initialise counter C100 (Transmission Request) to 1;

b. shall enter the ‘U: pending request to transmit’ state; and

c. if the transmission participant has received and stored a transmission control message before the reception of the SIP 200 (OK) response, shall act as if the transmission control message was received in the ‘U: pending request to transmit’ state after entering the ‘U: pending request to transmit’ state; and

5. if the established MCVideo call is a broadcast group call, shall enter the ‘U: has permission to transmit’ state.

When the transmission participant is rejoining an ongoing MCVideo call as described in 3GPP TS 24.281 [2] the transmission participant shall enter the ‘U: has no permission to transmit’ state.

6.2.4.2.3 MCVideo call established, terminating MCVideo user

When an MCVideo call is established, the terminating transmission participant:

1. shall create an instance of a ‘Transmission participant state transition diagram for basic transmission control operation’; and

2. shall enter the ‘U: has no permission to transmit’ state.

NOTE: From a transmission participant perspective the MCVideo call is established when the application and signalling plane sends the SIP 200 (OK) response.

6.2.4.3 State: ‘U: has no permission to transmit’

6.2.4.3.1 General

The transmission participant is in this state when the transmission participant is not sending RTP media packets or is not waiting for a transmission control message response.

In this state transmission control messages can be received.

6.2.4.3.2 Send Transmission Request message (Click Transmission send button)

Upon receiving an indication from the user to request permission to send media, the transmission participant:

1. void

2. shall send the Transmission Request message toward the transmission control server; The Transmission Request message:

a. if a different priority than the normal priority is required, shall include the Transmission Priority field with the priority not higher than negotiated with the transmission control server as specified in clause 14.3.3; and

b. if the Transmission request is a broadcast group call, system call, emergency call or an imminent peril call, shall include a Transmission Indicator field indicating the relevant call types;

3. shall start timer T100 (Transmission Request) and initialise counter C100 (Transmission Request) to 1; and

4. shall enter the ‘U: pending request to transmit’ state.

6.2.4.3.3 Void

6.2.4.3.4 Void

6.2.4.4 State: ‘U: pending request to transmit’

6.2.4.4.1 General

The transmission participant is in this state when the transmission participant is waiting for response to a Transmission Request message.

In this state transmission control messages can be received.

Timer T100 (Transmission Request) is running in this state.

6.2.4.4.2 Receive Transmission rejected message (R: Transmission rejected)

Upon receiving a Transmission rejected message, the transmission participant:

1. if the first bit in the subtype of the Transmission rejected message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘1’ (Transmission rejected); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall provide Transmission rejected notification to the user;

3. may display the Transmission rejected reason to the user using information in the Reject Cause field;

4. shall stop timer T100 ( Transmission Request); and

5. shall enter the ‘U: has no permission to transmit’ state.

6.2.4.4.3 Timer T100 (Transmission request) expired

On expiry of timer T100 ( Transmission Request) less than the upper limit of counter C100 (Transmission Request) times the timer is allowed to expire, the transmission participant:

1. shall send a Transmission Request message towards the transmission control server. The Transmission Request message:

b. if the Transmission request is a broadcast group call, system call, emergency call or an imminent peril call, shall include a Transmission Indicator field indicating the relevant call types;

2. shall restart timer T100 (Transmission request) and increment counter C100 (Transmission Request) by 1; and

3. shall remain in the ‘U: pending request to transmit’ state.

6.2.4.4.4 Timer T100 (Transmission Request) expired N times

When timer T100 (Transmission Request) expires by the upper limit of counter C100 (Transmission Request), the transmission participant:

1. shall provide a Transmission request timeout notification to the user; and

2. shall enter the ‘U: has no permission to transmit’ state.

6.2.4.4.5 Receive Queue Position Info message (R: Queue Position Info)

Upon receiving a Queue Position Info message, the transmission participant:

1. if the first bit in the subtype of the Queue Position Info message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘5’ (Queue Position Info); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall provide Transmission request queued notification to the MCVideo user;

3. may provide the queue position and priority to the MCVideo user; and

4. shall enter the ‘U: queued transmission’ state.

6.2.4.4.6 Receive Transmission Granted message (R: Transmission Granted)

Upon receiving a Transmission Granted message from the transmission control server, the transmission participant:

1. if the first bit in the subtype of the Transmission Granted message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘0’ (Transmission Granted); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall store the SSRC of granted transmission participant received in the Transmission Granted message;

3. shall provide Transmission granted notification to the user, if not already done;

4. shall stop timer T100 (Transmission Request); and

5. shall enter the ‘U: has permission to transmit’ state.

6.2.4.4.7 Send Transmission end request message (Click Transmission end button)

Upon receiving an indication from the user to end the Transmission request, the transmission participant:

1. shall send a Transmission end request message towards the transmission control server. The Transmission end request message, if the session is a broadcast call and if the session was established as a normal call, shall include the Transmission Indicator with the A-bit set to ‘1’ (Normal call);

2. shall stop time T100 (Transmission Request)

3. shall start timer T101 (Transmission End Request) and initialize counter C101 (Transmission End Request) to 1; and

4. shall enter the ‘U: pending end of transmission’ state.

6.2.4.5 State: ‘U: has permission to transmit’

6.2.4.5.1 General

The transmission participant is in this state when the MCVideo client is permitted to send RTP media.

In this state transmission control messages can be received.

In this state, the transmission participant can release permission to send RTP media at any time, even before sending any media.

The MCVideo client could have already buffered media when it enters this state.

NOTE: If the transmission participant was queued, the transmission participant requests a confirmation from the MCVideo user before start sending media. If confirmed, the media sending starts otherwise the permission to send media is released.

6.2.4.5.2 Send RTP media packets (S: RTP media)

Upon receiving indication from the MCVideo client that encoded video is received from the user or if encoded video is already buffered, the transmission participant:

1. shall request the MCVideo client to start to forward encoded video to the MCVideo server; and

2. shall remain in the ‘U: has permission to transmit’ state.

6.2.4.5.3 Send Transmission end request message (Click Transmission end button)

Upon receiving an indication from the user to end the permission to send RTP media, the transmission participant:

2. shall start timer T101 (Transmission End Request) and initialize counter C101 (Transmission End Request) to 1; and

3. shall enter the ‘U: pending end of transmission’ state.

6.2.4.5.4 Void

6.2.4.5.5 Receive Transmission Revoked message (R: Transmission Revoked)

Upon receiving a Transmission Revoked message, the transmission participant:

1. shall inform the user that the permission to send RTP media is being revoked;

2. may give information to the user about the reason for revoking the permission to send media:

3. shall request the media in the MCVideo client discard any remaining buffered RTP media packets and to stop forwarding of encoded video to the MCVideo server; and

4. if the revoke reason is:

a. terminate the RTP stream, shall enter the ‘U: pending end of transmission’ state:

i. shall send a Transmission end request message towards the transmission control server; and

ii. shall start timer T101 (Transmission End Request) and initialize counter C101 (Transmission End Request) to 1; or

b. queue the transmission, shall enter the ‘U: queued transmission’ state:

i. shall send a Queue Position Request message towards the transmission control server; and

ii. shall start timer T102 (Transmission Queue Position Request) and initialize counter C102 (Queue Position Request) to 1.

6.2.4.5.6 Receive Media reception notification message (R: Media Reception notification)

Upon receiving a Media Reception notification message, the transmission participant:

1. shall inform the user about the media reception by another user; and

2. shall remain in the ‘U: has permission to transmit’ state.

6.2.4.5.7 Receive Transmission End Rquest message (R: Transmission End Request)

Upon receiving a Transmission End Request message from transmission control server, the transmission participant:

1. shall inform the user that the permission to send RTP media is being revoked;

2. may give information to the user about the reason for terminating the permission to send media;

3. shall request the media in the MCVideo client to discard any remaining buffered RTP media packets and to stop forwarding of encoded video to the MCVideo server; and

4. shall send Transmission End Response message to the transmission control server.

5. if the session is not a broadcast group call or if the A-bit in the Transmission Indicator field is set to ‘1’ (Normal call), shall enter the ‘U: has no permission to transmit’ state; and

6. if the session was initiated as a broadcast group call:

a. shall indicate to the MCVideo client the media transmission is completed; and

b shall enter the ‘Call releasing’ state.

6.2.4.6 State: ‘U: pending end of transmission’

6.2.4.6.1 General

The transmission participant is in this state when the transmission participant is waiting for response to a Transmission end request message.

Timer T101 (Transmission End Request) is running or can be running in this state.

6.2.4.6.2 Timer T101 (Transmission End Request) expired

On expiry of timer T101 (Transmission End Request) less than the configurable number of the upper limit of counter C101 (Transmission End Request) times, the transmission participant:

1. shall send a Transmission end request message towards the transmission control server;

2. shall restart timer T101 (Transmission End Request) and increment counter C101 (Transmission End Request) by 1; and

3. shall remain in state ‘U: pending end of transmission’.

6.2.4.6.3 Timer T101 (Transmission End Request) expired N times

When timer T101 (Transmission End Request) expires by the upper limit of counter C101 (Transmission End Request) times, the transmission participant:

1. shall enter the ‘U: has no permission to transmit’ state.

6.2.4.6.4 Receive Transmission End Response message (R: Transmission end response)

Upon receiving a Transmission end response message, the transmission participant:

1. if the first bit in the subtype of the Transmission end response message to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘1’ (Transmission end response); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. may provide a Transmission end notification to the MCVideo user;

3. if the Transmission Indicator field is included and the B-bit set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating the type of call;

4. shall stop timer T101 (Transmission End Request);

5. if the session is not a broadcast group call or if the A-bit in the Transmission Indicator field is set to ‘1’ (Normal call), shall enter the ‘U: has no permission to transmit’ state; and

6. if the session was initiated as a broadcast group call:

a. shall indicate to the MCVideo client the media transmission is completed; and

b shall enter the ‘Call releasing’ state.

6.2.4.6.5 Void

6.2.4.7 In any state

6.2.4.7.1 General

This clause describes the actions to be taken in all states defined for the basic state diagram with the exception of the ‘Start-stop’ state and the ‘Call releasing’ state.

In this state RTP media packets can be received due to previous reception control, RTP media packets can be sent due previous transmission control and transmission control and reception control messages can be received.

6.2.4.7.2 Receive MCVideo call release – step 1 (R: MCVideo call release – 1)

Upon receiving an MCVideo call release step 1 request from the application and signalling plane when the MCVideo call is going to be released or when the transmission participant is leaving the MCVideo call, the transmission participant:

1. shall stop sending transmission control messages;

2. shall request the MCVideo client to stop sending RTP media packets; and

3. shall enter the ‘Call releasing’ state.

6.2.4.8 State: ‘Call releasing’

6.2.4.8.1 General

The transmission participant is in this state while waiting for the application and signalling plane to finalize the disconnection of an MCVideo call.

6.2.4.8.2 Receive MCVideo call release – step 2 (R: MCVideo call release – 2)

Upon receiving an MCVideo call release step 2 request from the application and signalling, the transmission participant:

1. shall release all resources including any running timers associated with the MCVideo call; and

2. shall enter the ‘Start-stop’ state and terminate the current instance of the ‘Transmission control state machine – basic’.

6.2.4.9 State: ‘U: queued transmission’

6.2.4.9.1 General

The transmission participant uses this state when a Transmission Media Request message has been queued by the transmission control server, and is awaiting the Transmission Granted message.

The timer T102 (Transmission Queue Position Request) can be running in this state.

6.2.4.9.2 Receive Queue Position Info message (R: Queue Position Info)

Upon receiving a Queue Position Info message, the transmission participant:

a. shall include the Message Type field set to ‘5’ (Queue Position Info); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. if the message indicates that the request has been queued or if a request for the queue position was sent, the transmission participant:

a. may provide the queue position and priority (if available) to the MCVideo user;

3. shall stop the timer T102 (Transmission Queue Position Request), if running; and

4. shall remain in the ‘U: queued transmission’ state.

6.2.4.9.3 Send Queue Position Request message (S: Queue Position Request)

Upon receipt of an indication from the MCVideo client to request the queue position, the transmission participant:

1. shall send the Queue Position Request message;

2. shall start timer T102 (Transmission Queue Position Request) and initialize counter C102 (Queue Position Request) to 1; and

3. remain in the ‘U: queued transmission” state.

6.2.4.9.4 Send Transmission end request message (Click Transmission end button)

Upon receipt of an indication from the MCVideo client to cancel the media transmit request from the queue, the transmission participant:

1. shall send the Transmission end request message to the transmission control server. The Transmission end request message, if the session is a broadcast call and if the session was established as a normal call, shall include the Transmission Indicator with the A-bit set to ‘1’ (Normal call);

2. shall start timer T101 (Transmission End Request) and initialize counter C101 (Transmission End Request) to 1; and

3. shall enter the ‘U: pending end of transmission’ state.

6.2.4.9.5 void

6.2.4.9.6 Receive Transmission cancel request notify message (R: Transmission Cancel Request Notify)

Upon receiving a Transmission cancel request notify message, the transmission participant:

1. if the first bit in the subtype of the Transmission cancel request notify message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ’10’ (Transmission cancel request); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall enter in the ‘U: has no permission to transmit’ state.

6.2.4.9.7 Timer T102 (Transmission Queue Position Request) expired

On expiry of timer T102 (Transmission Queue Position Request) less than the upper limit of C102 (Queue Position Request) times, the transmission participant:

1. shall send a Queue Position Request message towards the transmission control server;

2. shall restart timer T102 (Transmission Queue Position Request) and increment counter C102 (Queue Position Request) by 1; and

3. shall remain in the ‘U: queued transmission” state.

6.2.4.9.8 Timer T102 (Transmission Queue Position Request) expired N times

When timer T102 (Transmission Queue Position Request) expires by the upper limit of counter C102 (Queue Position Request) times, the transmission participant:

1. shall provide a queued timeout to the MCVideo client;

2. send the Transmission End Request message to the transmission control server;

3. shall start timer T101 (Transmission End Request) and increment counter C101 (Transmission End Request) by 1

4. shall enter the ‘U: pending end of transmission’ state.

6.2.4.9.9 Receive Transmission Granted message (R: Transmission Granted)

Upon receiving a Transmission Granted message from the transmission control server, the transmission participant:

a. shall include the Message Type field set to ‘0’ (Transmission Granted); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall store the SSRC of granted transmission participant received in the Transmission Granted message;

3. shall provide Transmission granted notification to the user, if not already done;

4. shall stop timer T102 (Transmission Queue position request); and

5. shall enter the ‘U: has permission to transmit’ state.

6.2.5 Transmission participant state transition diagram for reception control operation

6.2.5.1 General

The transmission participant shall behave according to the state diagrams and the state transitions specified in this clause.

Figure 6.2.5.1-1 shows the state diagram for ‘Transmission participant state transition diagram for general reception control operation’.

Figure 6.2.5.1-1: Transmission participant state transition diagram for general reception control operation.

Figure 6.2.5.1-2 shows the state diagram for ‘Transmission participant state transition diagram for basic reception control operation’.

Figure 6.2.5.1-2: Transmission participant state transition diagram for basic reception control operation.

The reception control arbitration logic in the transmission control participant shall keep one instance of the ‘general reception control operation’ state machine per MCVideo call and shall create one instance of the ‘basic reception control operation’ state machine for each ‘receive media request’ of the MCVideo user.

State details are explained in the following clauses.

If an RTP media packet arrives in a state where there is no specific procedure specified for the RTP media packets or the received reception control message, the transmission participant shall discard the reception control message or the RTP media packet and shall remain in the current state.

NOTE: A badly formatted RTP packet or reception control message received in any state is ignored by the transmission participant and does not cause any change of the current state.

6.2.5.2 State: ‘Start-stop’

6.2.5.2.1 General

This state is part of ‘Transmission participant state transition diagram for general reception control operation’. When a new instance of the ‘Transmission participant state transition diagram for general reception control operation’ is initiated, before any reception control related input is applied, the state machine is in ‘Start-stop’ state. Similarly when the call is released the state machine shall return to the ‘Start-Stop state.

6.2.5.2.2 MCVideo call established, terminating MCVideo user

When an MCVideo call is established, the terminating transmission participant:

1. shall create an instance of a ‘Transmission participant state transition diagram for general reception control operation’; and

2. shall enter the ‘U: reception controller’ state.

NOTE: From a transmission participant perspective the MCVideo call is established when the application and signalling plane sends the SIP 200 (OK) response.

6.2.5.2.3 MCVideo call initiated, originating MCVideo user

When an MCVideo call is established, the originating transmission participant:

1. shall create an instance of a ‘Transmission participant state transition diagram for general reception control operation’; and

2. shall enter the ‘U: reception controller’ state.

NOTE: From a transmission participant perspective the MCVideo call is established when the application and signalling plane receives the SIP 200 (OK) response.

6.2.5.3 State: ‘U: reception controller’

6.2.5.3.1 General

This state is part of the ‘Transmission participant state transition diagram for general reception control operation’. The transmission participant is in this state handles the incoming media transmission notifications and MCVideo user’s requests to receive media transmissions.

6.2.5.3.2 Receive Media transmission notification message (R: Media Transmission Notification)

Upon receiving the media transmission notification from the transmission control server, the transmission participant:

1. if the first bit in the subtype of the media transmission notification message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘6’ (Media transmission notification); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall provide media transmission notification to the user;

3. shall store the User ID and the SSRC of the user transmitting the media;

4. shall store the Functional Alias ID if received in the Media transmission notification;

5. if the Reception Mode field is set to ‘0’ indicating automatic reception mode:

a. shall create an instance of the ‘Transmission participant state transition diagram for basic reception control operation’;

b. shall map the stored User ID and the SSRC of the user transmitting the media with the instance of ‘Transmission participant state transition diagram for basic reception control operation’ created in step a); and

c. shall enter the ‘U: has permission to receive’ state;

6. may display the details of the incoming media to the user; and

7. shall remain in the ‘U: reception controller’ state.

6.2.5.3.3 Send Receive Media Request message (Click video receive button)

Upon receiving an indication from the user to request permission to receive media, the transmission participant:

1. shall send the Receive Media Request message toward the transmission control server; The Receive Media Request message:

a. if a different priority than the normal priority is required, shall include the Reception Priority field with the priority not higher than negotiated with the transmission control server as specified in clause 14.3.3; and

b. if the receive media request is a broadcast group call, system call, emergency call or an imminent peril call, shall include a Transmission Indicator field indicating the relevant call types;

2. shall create an instance of the ‘Transmission participant state transition diagram for basic reception control operation’;

3. shall map the stored User ID and the SSRC of the user transmitting the media with instance of ‘Transmission participant state transition diagram for basic reception control operation’ created in step 2; and

4. shall remain in the ‘U: reception controller’ state.

6.2.5.3.4 Receive Transmission end notify message (R: Transmission end notify)

Upon receiving a Transmission end notify message, the transmission participant:

1. shall inform the user about the media transmission ended by another user; and

2. shall remain in the ‘U: reception controller’ state.

6.2.5.3.5 Receive MCVideo call release – step 1 (R: MCVideo call release – 1)

1. shall stop receiving reception control messages;

2. shall request the MCVideo client to stop receiving RTP media packets; and

3. shall enter the ‘Call releasing’ state.

6.2.5.4 State: ‘U: pending request to receive’

6.2.5.4.1 General

This state is part of the ‘Transmission participant state transition diagram for basic reception control operation’. The transmission participant is in this state when the transmission participant is waiting for response to a Receive Media Request message.

In this state, the transmission participant can cancel the Receive Media Request at any time, even before actually receiving response to a Receive Media Request message.

The transmission participant shall start Timer T103 (Receive Media Request) and initialize the counter C103 (Receive Media Request) to 1 on entering in this state.

6.2.5.4.2 Reception of Receive media response (rejected) message (R: RM response (rejected))

Upon receiving a rejected response for Receive media request message, the transmission participant:

1. if the first bit in the subtype of the Receive media response message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘7’ (Receive media response); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall provide receive media rejected notification to the user;

3. may display the receive media rejected reason to the user using information in the Reject Cause field;

4. shall stop timer T103 (Receive Media Request); and

5. shall enter the ‘terminated’ state.

6.2.5.4.3 Timer T103 (Receive media request) expired

On expiry of timer T103 (Receive Media Request) less than the upper limit of counter C103 (Receive Media Request) times the timer is allowed to expire, the transmission participant:

1. shall send a Receive Media Request message towards the transmission control server. The Receive Media Request message:

b. if the receive media request is a broadcast group call, system call, emergency call or an imminent peril call, shall include a Transmission Indicator field indicating the relevant call types;

2. shall restart timer T103 (Receive media request) and increment counter C103 (Receive Media Request) by 1; and

3. shall remain in the ‘U: pending request to receive’ state.

6.2.5.4.4 Timer T103 (Receive Media Request) expired N times

When timer T103 (Receive Media Request) expires by the upper limit of counter C103 (Receive Media Request), the transmission participant:

1. shall provide a receive media request timeout notification to the user; and

2. shall enter the ‘terminated’ state.

6.2.5.4.5 Reception of Receive media response (granted) message (R: RM response (granted))

Upon receiving a granted response for Receive media request message, the transmission participant:

a. shall include the Message Type field set to ‘7’ (Receive media response); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. shall provide receive media success notification to the user;

3. if the Receive Media Indicator field is included and the B-bit is set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating the type of call;

4. shall stop timer T103 (Receive Media Request); and

5. shall enter the ‘U: has permission to receive’ state.

6.2.5.4.6 Media reception request cancel (Click video reception end button)

Upon receiving an indication from the user to cancel the Receive Media Request, the transmission participant:

1. shall send a Media reception end request message towards the transmission control server The Media reception end request message:

a. if the session is a broadcast call and if the session was established as a normal call, shall include the Transmission Indicator with the A-bit set to ‘1’ (Normal call); and

b. shall include the SSRC of user transmitting the media in the Media reception end request message;

2. shall remove the indication that the participant is overriding without revoke if this indication is stored;

3. shall remove the indication that the participant is overridden without revoke if this indication is stored;

4. shall stop timer T103 (Receive Media Request);

5. shall start timer T104 (Receive Media Release) and initialize counter C104 (Receive Media Release) to 1; and

6. shall enter the ‘U: pending reception release’ state.

6.2.5.5 State: ‘U: has permission to receive’

6.2.5.5.1 General

This state is part of the ‘Transmission participant state transition diagram for basic reception control operation’. The transmission participant is in this state when the MCVideo client is permitted to receive RTP media.

In this state, the transmission participant can end the reception of RTP media at any time, even before actually receiving any media.

6.2.5.5.2 Receive RTP media packets (R: RTP media)

Upon receiving indication from the transmission control server that encoded video is received from the source, the transmission participant:

NOTE: RTP media packets can be received from multiple sources by the transmission control server. The MCVideo client can differentiate between the different sources using the SSRC in the received RTP media packets. How the media mixer in the MCVideo client mixes the different RTP media stream sources is out of scope of the present document.

1. shall receive the encoded video from the MCVideo server; and

2. shall remain in the ‘U: has permission to receive’ state.

6.2.5.5.3 Media reception end request message (Click video reception end button)

Upon receiving an indication from the user to end the RTP media reception, the transmission participant:

1. shall send a Media reception end request message towards the transmission control server The Media reception end request message:

a. if the session is a broadcast call and if the session was established as a normal call, shall include the Transmission Indicator with the A-bit set to ‘1’ (Normal call); and

b. shall include the SSRC of user transmitting the media in the Media reception end request message;

2. shall remove the indication that the participant is overriding without revoke if this indication is stored;

3. shall remove the indication that the participant is overridden without revoke if this indication is stored;

4. shall start timer T104 (Receive Media Release) and initialize counter C104 (Receive Media Release) to 1; and

5. shall enter the ‘U: pending reception release’ state.

6.2.5.5.4 Receive Media reception override notify message (R: Media Rx override notify)

Upon receiving a Media reception override notify message, the transmission participant:

1. shall inform the user that the permission to receive a RTP media is being overriden;

2. may give information to the user about the reason for overriding the received RTP media;

3. shall send a Media reception end request message towards the transmission control server;

4. shall start timer T104 (Receive Media Release) and initialize counter C104 (Receive Media Release) to 1; and

5. shall enter the ‘U: pending reception release’ state.

6.2.5.5.5 Receive Media reception end request message (R: MRE request)

Upon receiving a Media reception end request message, the transmission participant:

1. if the first bit in the subtype of the Media reception end request message set to "1" (Acknowledgment is required) as described in clause 8.3.2, shall send a Reception control Ack message. The Reception control Ack message:

a. shall include the Message Type field set to ‘2’ (Media reception end request);

b. shall include the Source field set to ‘0’ (the transmission participant is the source); and

c. shall include the Message Name field set to MCV2.

2. shall inform the user that the receiving RTP media is being ended;

3. may give information to the user about the reason for ending the received RTP media;

4. shall request the MCVideo client to discard any remaining buffered RTP media packets and stop displaying to user;

5. shall send a Media reception end response message towards the transmission control server;

6. may provide a Media reception end notification to the MCVideo user;

7. if the Receive Media Indicator field is included and the B-bit set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating the type of call; and

8. shall enter the ‘terminated’ state.

6.2.5.5.6 Void

6.2.5.6 State: ‘U: pending reception release’

6.2.5.6.1 General

Timer T104 (Receive Media Release) is running in this state.

6.2.5.6.2 Timer T104 (Receive Media Release) expired

On expiry of timer T104 (Receive Media Release) less than the configurable number of the upper limit of counter C104 (Receive Media Release) times, the transmission participant:

1. shall send a MRE request message towards the transmission control server;

2. shall restart timer T104 (Receive Media Release) and increment counter C104 (Receive Media Release) by 1; and

3. shall remain in state ‘U: pending reception release’.

6.2.5.6.3 Timer T104 (Receive media release) expired N times

When timer T104 (Receive media Release) expires by the upper limit of counter C104 (Receive Media Release) times, the transmission participant:

1. shall enter the ‘terminated’ state.

6.2.5.6.4 Receive Media Reception End Response message (R: MRE response)

Upon receiving a MRE response message, the transmission participant:

1. if the first bit in the subtype of the MRE response message set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message. The Transmission control Ack message:

a. shall include the Message Type field set to ‘3’ (Media reception end response); and

b. shall include the Source field set to ‘0’ (the transmission participant is the source);

2. may provide a Media reception end notification to the MCVideo user;

3. if the Receive Media Indicator field is included and the B-bit set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating the type of call;

4. shall stop timer T104 (Receive Media Release); and

5. shall enter the ‘terminated’.

6.2.5.6.5 Void

6.2.5.7 Void

6.2.5.7.1 Void

6.2.5.7.2 Void

6.2.5.7.3 Void

6.2.5.7.4 Void

6.2.5.8 State: ‘U: terminated’

6.2.5.8.1 General

This state is part of the ‘Transmission participant state transition diagram for basic reception control operation’. On entering this state, the transmission participant:

1. shall delete the instance of this basic reception control state machine; and

2. if the session was initiated as a broadcast group call, shall indicate to the ‘Transmission participant state transition diagram for general reception control operation’ state machine to move to ‘Call releasing’ state.

6.2.5.9 State: ‘Call releasing’

6.2.5.9.1 General

This state is part of the ‘Transmission participant state transition diagram for general reception control operation’. The transmission participant is in this state while waiting for the application and signalling plane to finalize the disconnection of an MCVideo call.

6.2.5.9.2 Receive MCVideo call release – step 2 (R: MCVideo call release – 2)

Upon receiving an MCVideo call release step 2 request from the application and signalling, the transmission participant:

1. shall release all resources including any running timers associated with the MCVideo call;

2. shall terminate all instance(s) of the ‘Transmission participant state transition diagram for basic reception control operation’; and

3. shall enter the ‘Start-stop’ state and terminate the current instance of the ‘Transmission participant state transition diagram for general reception control operation’.