7 Off-network MCVideo service media plane procedures

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

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

7.1 General

Transmission control in off-network can be performed in two ways:

– Single arbitrator: transmission participants rely on a single participant designated as transmission arbitrator for the arbitration of transmission requests.

– Self arbitration: each transmission participant arbitrates its own transmission based on its view of the topology.

Both of the approaches, as appropriate for the deployment model, can be adopted for a MCVideo group using the "/<x>/<x>/OffNetwork/MCVideo/ArbitrationApproach" configuration parameter.

If the value of "/<x>/<x>/OffNetwork/MCVideo/ArbitrationApproach" leaf node present in group configuration as specified in 3GPP TS 24.483 [4] is set to:

– "single", then single arbitrator approach applies; or

– "self", then self arbitration approach applies.

In the single arbitrator approach, one MCVideo client assumes the responsibility for arbitration of transmission requests for all group members within range. All requests for transmission are directed to the arbitrator, and the arbitrator checks the configured limits on the simultaneous transmissions, and grants or denies the request. If an MCVideo client is out of range of the current arbitrator, the MCVideo client is allowed to transmit and also become a transmission arbitrator. If there is insufficient capacity to carry an extra transmission i.e. the configured limit for simultaneous transmissions is reached, the MCVideo client can request that an existing transmitting MCVideo client is pre-empted; the pre-emption request is sent to the transmission arbitrator.

In the self arbitration approach, each MCVideo client decides for itself whether there is sufficient capacity to carry the transmission. If it determines that there is insufficient capacity i.e. the configured limit for simultaneous transmissions is reached, and from its perspective another transmitting MCVideo client has a lower priority, the requesting MCVideo client can send an override request directly to this other transmitting MCVideo client, which will either accept the override request and give way, or deny the override request.

In both the single arbitrator approach and the self arbitration approach, if there is insufficient capacity to carry the communication i.e. the configured limit on the simultaneous transmissions is reached, the MCVideo client can report this to the MCVideo user. The MCVideo user can decide to transmit anyway, and instruct the MCVideo client to proceed with the transmission.

7.2 Transmission participant procedures for single arbitrator approach

7.2.1 Transmission participant procedures at MCVideo session initialisation

This clause applies when no active transmission control session exists.

Before a transmission control entity is initiated a state machine with a single state, named as ‘Start-stop’ state, shall exist. At ‘Start-stop’ state, when the MCVideo client receives a request of the MCVideo call control entity to initiate the transmission control as originating client, then the MCVideo client shall initiate a transmission control entity and the transmission control entity shall enter into the ‘O: transmission arbitration’ state. Otherwise, if MCVideo client receives a request of the MCVideo call control entity to initiate the transmission control as terminating client, then the MCVideo client shall initiate a transmission control entity and the transmission control entity for an MCVideo group call shall enter into the ‘O: silence’ state or for both MCVideo private call and MCVideo broadcast call shall enter the ‘O: has no permission’ state.

Once the session is initiated, the initial transmission control messages are sent according to the state machine presented in clause 7.2.3. Normally, once the session is started the originating MCVideo client has the transmission implicitly. For an on-going off-network group call, if an MCVideo client joins later, then it starts the transmission control session and takes the role of transmission participant and enters ‘O: silence’ state.

7.2.1.2 Determine off-network transmission priority

In the absence of a mission critical organization’s method for determining off-network transmission priority, the following procedure shall be used. Otherwise, the mission critical organization’s method shall supersede this clause.

Upon receiving a Transmission Request message, to determine the transmission priority of the Transmission Request message, the transmission arbitrator:

1. shall check the presence of Transmission priority field in the received Transmission Request message. If present, the transmission arbitrator:

a. shall determine the transmission priority of the Transmission Request message by choosing the lowest value from the following inputs:

i. the value of the Transmission priority field in the received Transmission Request message;

ii. the value of the "/<x>/<x>/Common/MCPTTGroupMemberList/<x>/UserPriority" leaf node of the sender of the Transmission Request message, present in group configuration as specified in 3GPP TS 24.483 [4]; and

iii. the value of the "/<x>/OffNetwork/NumLevelHierarchy" leaf node present in service configuration as specified in 3GPP TS 24.483 [4]; and

2. if the Transmission priority field is not present in the Transmission Request message, the transmission arbitrator:

a. shall use the minimum value allowed for the Transmission priority as transmission priority of the Transmission Request message.

Once the transmission priority of the Transmission Request message is determined, to determine the effective priority of the Transmission Request message, if the number of transmitters has reached maximum, the transmission arbitrator:

1. shall check the type of call indicated by the Transmission Indicator field of the received Transmission Request message and:

a. if the type of call indicated by the Transmission Indicator field is Normal call and:

i. if the current type of the call is normal, shall continue to check the next input parameter from step 2; or

ii if the current type of the call is emergency or imminent-peril, shall deny the transmission request and skip step 2;

b. if the type of call indicated by the Transmission Indicator field is Imminent peril call and:

i. if the current type of the call is normal:

A. shall pre-empt a current transmitter;

B. shall grant the transmission request; and

C. shall skip step 2;

ii. if the current type of the call is imminent-peril, shall continue to check the next input parameter from step 2; and

iii. if the current type of the call is emergency, shall deny the transmission request and skip step 2;

c. if the type of the call indicated by the Transmission Indicator field is Emergency call and:

i. if the current type of the call is normal or imminent-peril:

A. shall pre-empt a current transmitter; and

B. shall grant the transmission request;

C. shall skip step 2;

ii. if the current type of the call is emergency, shall continue to check the next input parameter from step 2; and

2. shall compare the determined transmission priority of the received Transmission Request message to the effective priority of the current transmitters (determined at the time of transmission grant to the current transmitters) and:

a. if the effective priority of all the current transmitters are equal to or higher than the determined transmission priority of the Transmission Request message, shall deny the transmission request; and

b. if the determined transmission priority of the Transmission Request message is higher than any of the current transmitters:

i. shall pre-empt a current transmitter with lower priority; and

ii. shall grant the transmission request.

7.2.2 Transmission participant procedures at MCVideo call release

This clause applies when an active transmission control session exists.

When the off-network call is released the transmission control session is terminated. The off-network transmission control session can also be terminated when no media transmission or reception takes place during transmission control session hold time, T230 (Inactivity). The termination of the transmission control session as a result of the expiry of timer T230 (Inactivity) may terminate the call session.

7.2.3 Transmission participant state diagram – basic operation

7.2.3.1 General

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

The received transmission messages and the RTP media packets are inputs to the state machine according to their arrival order. They are not ignored unless otherwise stated.

The MCVideo client also provides input to the state machine as request to transmit video (click video transmission send button) or as end of video transmission (click video transmission end button).

Figure 7.2.3.1-1 show the ‘Transmission participant state diagram – basic operation’.

Figure 7.2.3.1-1: ‘Transmission participant state diagram – basic operation’

State details are explained in the following clauses.

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

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

7.2.3.2 State: ‘Start-stop’

7.2.3.2.1 General

When a new instance of the state machine is created, before any transmission control related input is applied, the state machine is in the ‘Start-stop’ state. Similarly when the call is released or the transmission control session is terminated, the state machine shall return to the ‘Start-stop’ state.

7.2.3.2.2 MCVideo call established – originating MCVideo user

When an MCVideo call is established with session announcement including an explicit transmission request, the originating transmission participant:

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. shall send Transmission Granted message towards other transmission participants. The Transmission Granted message:

a. shall include the granted priority in the Transmission priority field;

b. shall include the MCVideo user’s own MCVideo ID in the User ID field; and

c. 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; and

3. shall enter ‘O: transmission arbitration’ state.

7.2.3.2.3 MCVideo group 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 operation state machine;

2. shall start timer T230 (Inactivity); and

3. shall enter ‘O: silence’ state.

7.2.3.2.4 MCVideo private call established – terminating MCVideo user

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

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. shall start timer T203(End of RTP media); and

3. shall enter ‘O: has no permission’ state.

7.2.3.2.5 Send Transmission Request message (click video transmission send button)

If the transmission participant receives an indication from the MCVideo user to send media, the transmission participant:

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. shall send the Transmission Request message to other transmission participants. The Transmission Request message:

a. if a different priority than the normal priority is required, shall include the Transmission Priority field with the requested priority in the <Transmission Priority> value;

b. shall include the MCVideo ID of the MCVideo user in the <User ID> value of the User ID field; and

c. 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 initialise the counter C201 (Transmission request) with value set to 1;

4. shall start the timer T201 (Transmission request); and

5. shall enter ‘O: pending request’ state.

7.2.3.2.6 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received, the transmission participant:

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. may provide a transmission taken notification to the MCVideo user;

3. shall set the stored current transmission arbitrator to Granted Party’s Identity value of the Granted Party’s Identity field in the Transmission Arbitration Taken message;

4. shall start timer T203 (End of RTP media) and store the current transmission arbitrator in transmitter list; and

5. shall enter ‘O: has no permission’ state.

7.2.3.2.7 Receive Transmission Granted message (R: Transmission Granted to other)

When a Transmission Granted message is received, the transmission participant:

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. may provide a transmission taken notification to the MCVideo user;

3. shall set the stored current transmission arbitrator to the identity of sender of Transmission Granted message;

4. shall start timer T203 (End of RTP media) and store the user to whom the transmission was granted in the Transmission Granted message in transmitter list; and

5. shall enter ‘O: has no permission’ state.

7.2.3.2.8 Receive RTP media (R: RTP media)

Upon receiving RTP media packets, the transmission participant:

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. may provide a transmission taken notification to the MCVideo user;

3. shall restart timer T203 (End of RTP media);

4. shall request the MCVideo client to start rendering received RTP media packets; and

5. shall enter ‘O: has no permission’ state.

7.2.3.2.9 MCVideo broadcast call established – terminating MCVideo user

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

1. shall create an instance of a transmission participant state transition diagram for basic operation state machine;

2. shall start timer T203 (End of RTP media); and

3. shall enter ‘O: has no permission’ state.

NOTE: In MCVideo broadcast call, only originating MCVideo user is allowed to request transmission and transmit media. A Transmission Request message is locally denied to terminating MCVideo user, if requested.

7.2.3.3 State: ‘O: silence’

7.2.3.3.1 General

When in this state the MCVideo client for the session is unaware of any MCVideo client acting as a transmission arbitrator, has not itself initiated a transmission control request and is not currently receiving RTP media packets.

Timer T230 (Inactivity) is running in this state.

7.2.3.3.2 Send Transmission Request message (click video transmission send button)

If the transmission participant receives an indication from the MCVideo user to send media, the transmission participant:

1. shall send the Transmission Request message to other transmission participants. The Transmission Request message:

a. if a priority different than the default transmission priority is required, shall include the Transmission Priority field with the requested priority in the <Transmission Priority> element;

b. shall include the MCVideo ID of the MCVideo user in the <User ID> value of the User ID field; and

c. 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 initialise the counter C201 (Transmission request) with value set to 1;

3. shall stop timer T230 (Inactivity);

4. shall start timer T201 (Transmission Request); and

5. shall enter ‘O: pending request’ state.

7.2.3.3.3 Receive RTP media (R: RTP media)

Upon receiving RTP media packets, the transmission participant:

1. may provide a transmission taken notification to the MCVideo user;

2. shall stop timer T230 (Inactivity);

3. shall start timer T203 (End of RTP media) for the SSRC of RTP media packet;

4. shall request the MCVideo client to start rendering received RTP media packets; and

5. shall enter ‘O: has no permission’ state.

7.2.3.3.4 Receive Transmission Granted message (R: Transmission Granted to other)

When a Transmission Granted message is received and if the User ID in the Transmission Granted message does not match its own User ID, the transmission participant:

1. may provide a transmission taken notification to the MCVideo user;

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

3. shall stop timer T230 (Inactivity);

4. shall start timer T203 (End of RTP media) and store the identity of the user, to whom the transmission was granted in the Transmission Granted message, in transmitter list; and

5. shall enter ‘O: has no permission’ state.

7.2.3.3.5 Receive Transmission Request message (R: Transmission Request)

The transition is used in private call only. When a Transmission Request message is received, the transmission participant:

1. shall send a Transmission Granted message toward the other transmission participant. The Transmission Granted message:

a. shall include the MCVideo ID of the Transmission Request message received in User ID value of the User ID field;

b. shall include the SSRC of the Transmission Request message received in the SSRC of transmission control server field;

c. shall include the max duration as configured in the MCVideo client in the OffNetwork/MaxDuration parameter in the <Duration> value of the Duration field; and

d. shall include the priority of the Transmission Request message received in the <Transmission Priority> value of the Transmission Priority field;

2. shall stop timer T230 (Inactivity);

3. shall start timer T205 (Transmission Granted); and

4. shall enter ‘O: pending delegated’ state.

7.2.3.3.6 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received, the transmission participant:

1. may provide a transmission taken notification to the MCVideo user;

2. shall set the stored the current transmission arbitrator to Granted Party’s Identity value of the Granted Party’s Identity field in the Transmission Arbitration Taken message;

3. shall stop timer T230 (Inactivity);

4. shall start timer T203 (End of RTP media) and store the identity of the current transmission arbitrator in transmitter list; and

5. shall enter ‘O: has no permission’ state.

7.2.3.3.7 Timer T230 (Inactivity) expired

Upon expiry of timer T230 (Inactivity), the transmission participant:

1. shall indicate to the call control that timer T230 (inactivity) has expired;

2. shall terminate the instance of transmission participant state transition diagram; and

3. shall enter ‘Start-stop’ state.

7.2.3.4 State: ‘O: has no permission’

7.2.3.4.1 General

In this state the MCVideo client does not have permission to send media.

7.2.3.4.2 Sending Transmission Request message (click video transmission send button)

If the transmission participant receives an indication from the MCVideo user that the MCVideo user wants to send media, the transmission participant:

1. shall send the Transmission Request message to other clients. The Transmission Request message:

a. if a priority different than the default transmission priority is required, shall include the Transmission Priority field with the requested priority in the <Transmission Priority> element;

b. shall include the MCVideo ID of the MCVideo user in the User ID field; and

c. 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 initialise the counter C201 (Transmission request) with value set to 1;

3. shall start timer T201 (Transmission Request); and

4. shall enter ‘O: pending request’ state.

7.2.3.4.3 Receive Transmission Release message (R: Transmission Release)

When a Transmission Release message is received and if the User ID in the Transmission Release message matches with the stored User ID in transmitter list, the transmission participant:

1. may provide transmission released notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Release message;

4. shall delete the User ID from the transmitter list;

5. if there is no transmitter in transmitter list, shall start timer T230 (Inactivity) and enter ‘O: silence’ state; or

6. if there are transmitter(s) in transmitter list, shall remain in ‘O: has no permission’ state.

7.2.3.4.4 Receive Transmission Arbitration Release message (R: Transmission Arbitration Release)

When a Transmission Arbitration Release message is received and if the User ID in the Transmission Arbitration Release message matches with the stored current transmission arbitrator, the transmission participant:

1. may provide transmission arbitration idle notification to the MCVideo user;

2. shall stop timer T203 (End of RTP media) for User ID in the Transmission Arbitration Release message;

3. shall delete the User ID in transmitter list;

4. shall clear the stored current transmission arbitrator;

5. if there is no User ID in transmitter list, shall start timer T230 (Inactivity) and enter ‘O: silence’ state; or

6. if there are transmitter(s) in transmitter list, shall remain in ‘O: has no permission’ state.

7.2.3.4.5 Timer T203 (End of RTP media) expired

On expiry of T203 (End of RTP media) timer, the transmission participant:

1. may provide transmission lost notification to the MCVideo user for the User ID whose associated timer T203 (End of RTP media) expired;

3. shall delete the associated User ID from the transmitter list;

4. if there is no User ID in transmitter list, shall start timer T230 (Inactivity) and enter ‘O: silence’ state; or

5. if there are transmitter(s) in transmitter list, shall remain in ‘O: has no permission’ state.

7.2.3.4.6 Receive Transmission Granted message (R: Transmission Granted to other)

When a Transmission Granted message is received and if the <User ID> value in the User ID field does not match its own MCVideo ID, the transmission participant:

1. shall start timer T203 (End of RTP media) for the User ID;

2. shall store the user to whom the transmission was granted in the Transmission Granted message in transmitter list;

3. may provide a transmission taken notification to the MCVideo user;

4. if the Transmission Indicator field is included with the B-bit set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating that this is a broadcast group call; and

5. shall remain in the ‘O: has no permission’ state.

7.2.3.4.7 Receive RTP media (R: RTP media)

Upon receiving RTP media packets and with SSRC not associated with any transmitter stored in the transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall store the SSRC of RTP media packet in the transmitter list as unknown user;

3. shall start timer T203 (End of RTP media) associated with the SSRC; and

4. shall remain in ‘O: has no permission’ state.

Otherwise, if SSRC of transmission participant sending the media matches the stored SSRC of a user in transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall restart timer T203 (End of RTP media) associated with the User ID; and

3. shall remain in ‘O: has no permission’ state.

7.2.3.4.8 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received and there is no stored current transmission arbitrator, the transmission participant:

1. if the <User ID> value in the User ID field in Transmission Arbitration Taken message doesn’t match with User ID in transmitter list, shall start timer T203 (End of RTP media);

2. shall store the value of <User ID> field of the Transmission Arbitration Taken message as the current transmission arbitrator; and

3. shall remain in ‘O: has no permission’ state.

7.2.3.4.9 Receive Transmission Revoked message (R: Transmission Revoked)

When a Transmission Revoked message is received and if the User ID in the Transmission Revoked message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission revoked notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets from the revoked user;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Revoked message;

4. shall delete the User ID inform the transmitter list;

5. if the User ID in the Transmission Revoked message matches with the stored User ID of current transmission arbitrator, shall clear current transmission arbitrator;

6. if there is no transmitter in transmitter list, shall start timer T230 (Inactivity) and enter ‘O: silence’ state; or

7. if there are transmitter(s) in transmitter list, shall remain in ‘O: has no permission’ state.

7.2.3.5 State: ‘O: transmission arbitration’

7.2.3.5.1 General

In this state the MCVideo client is acting as a transmission control server (transmission arbitrator) and has the permission to send media.

Timer T206 (Stop talking warning) and timer T207 (Stop Talking) are running in this state.

7.2.3.5.2 Send RTP Media packets (S: RTP Media)

Upon receiving encoded media from the user or if encoded media is already buffered the transmission participant:

1. shall start timer T206 (Stop talking warning);

2. shall request the MCVideo client to start sending RTP media packets towards other MCVideo clients; and

3. shall remain in ‘O: transmission arbitration’ state.

7.2.3.5.3 Receive Transmission Release message (R: Transmission Release)

When a Transmission Release message is received and if the User ID in the Transmission Release message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission release notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets from the user;

3. shall stop timer T203 (End of RTP media) associated with the User ID in the Transmission Release message;

4. shall delete the User ID from the transmitter list; and

5. shall remain in ‘O: transmission arbitration’ state.

7.2.3.5.4 Receive Transmission Request message (R: Transmission Request)

Upon receiving a Transmission Request message which is not pre-emptive and if the number of current transmitter have reached maximum then, the transmission participant:

1. shall send the Transmission Rejected message. The Transmission Rejected message:

a. shall include in the Reject Cause field the <Reject Cause> value cause #1 (Transmission limit reached);

b. may include in the Reject Cause field an additional text string explaining the reason for rejecting the transmission request in the <Reject Phrase> value; and

c. shall include the User ID field received in the Transmission Request message; and

2. shall remain in ‘O: transmission arbitration’ state.

Upon receiving a Transmission Request message which is not pre-emptive and if the number of current transmitter have not reached the maximum limit, the transmission participant:

1. shall send the Transmission Granted message toward the other transmission participants. The Transmission Granted message:

a. shall include the MCVideo ID of the granted transmission participant in the User ID field;

b. shall include the SSRC of the granted transmission participant in the SSRC of the granted transmission participant field; and

c. 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 start timer T205 (Transmission Granted) and shall initiate counter C205 (Transmission Granted ) to 1;

3. shall remain in ‘O: transmission arbitration’ state.

7.2.3.5.5 Send Transmission Arbitration Release message (click video transmission end button with empty transmitter list)

Upon receiving an indication from the MCVideo user to release permission to send RTP media and there is no transmitter in transmitter list, the transmission participant:

1. shall stop timer T206 (Stop talking warning), if running;

2. shall stop timer T207 (Stop talking), if running;

3. shall send a Transmission Arbitration Release message towards other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field; and

b. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call);

4. shall start timer T230 (Inactivity); and

5. shall enter ‘O: silence’ state.

7.2.3.5.6 Send Transmission Arbitration Release message (click video transmission end button with non-empty transmitter list)

When no more encoded media is received from the user and if at least one transmitter is present in the transmitter list , the transmission participant:

1. shall stop timer T206 (Stop talking warning), if running;

2. shall stop timer T207 (Stop talking), if running;

3. shall request the MCVideo client to stop sending RTP media packets towards other MCVideo clients;

4. shall send the Transmission Arbitration Release message toward the other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field;

b. shall include the MCVideo ID of the first transmission participant in the transmitter list in the Next Arbitrator field;

c. shall remove the first transmission participant from the transmitter list;

d for the remaining transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field; and

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field; and

5. shall start timer T208 (Transmission Arbitration Release) and shall initiate counter C208 (Transmission Arbitration Release) to 1; and

6. shall enter the ‘O: pending delegated’ state.

7.2.3.5.7 Receive Transmission Request message with pre-emption indication and revoking self (R: Transmission Request with pre-emption)

Upon receiving a Transmission Request message which is pre-emptive and the transmission arbitrator revokes self, the transmission participant:

1. shall stop timer T206 (Stop talking warning), if running;

2. shall stop timer T207 (Stop talking), if running;

3. shall request the MCVideo client to stop sending RTP media packets towards other MCVideo clients;

4. shall send the Transmission Revoked message toward the other transmission participants. The Transmission Revoked message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field;

b. shall include in the Reject Cause field the <Reject Cause> value cause #1 (Transmission limit reached);

c. may include in the Reject Cause field an additional text string explaining the reason for rejecting the transmission request in the <Reject Phrase> value; and

d. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call);

5. shall send the Transmission Granted message toward the other transmission participants. The Transmission Granted message:

a. shall include the MCVideo ID of the granted transmission participant in the User ID field;

b. shall include the SSRC of the granted transmission participant in the SSRC of the granted transmission participant field;

c. shall include the MCVideo ID of the granted transmission participant in the Next Arbitrator field; and

d for the transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field; and

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field;

6. shall start timer T205 (Transmission Granted) and shall initiate counter C205 (Transmission Granted) to 1; and

7. shall enter the ‘O: pending delegated’ state.

7.2.3.5.8 Receive Transmission Request message with pre-emption indication and revoking a transmitter (R: Transmission Request with pre-emption)

Upon receiving a Transmission Request message which is pre-emptive and the transmission arbitrator determines to revoke a transmitter from the transmitter list, the transmission participant:

1. shall request the MCVideo client to stop rendering RTP media packets from the MCVideo user to be revoked;

2. shall send the Transmission Revoked message toward the other transmission participants. The Transmission Revoked message:

a. shall include the MCVideo ID of the MCVideo user to be revoked in the User ID field;

b. shall include in the Reject Cause field the <Reject Cause> value cause #1 (Transmission limit reached);

c. may include in the Reject Cause field an additional text string explaining the reason for rejecting the transmission request in the <Reject Phrase> value; and

d. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call);

3. shall send the Transmission Granted message toward the other transmission participants. The Transmission Granted message:

a. shall include the MCVideo ID of the granted transmission participant in the User ID field; and

b. shall include the SSRC of the granted transmission participant in the SSRC of the granted transmission participant field;

4. shall start timer T205 (Transmission Granted) and shall initiate counter C205 (Transmission Granted) to 1; and

5. shall remain in the current state.

7.2.3.5.9 Transmission time limit warning (Timer T206 expires)

When timer T206 (Stop talking warning) expires, the transmission participant:

1. may notify the MCVideo user that the transmission time limit is about to reach;

2. shall start timer T207 (Stop talking); and

3. shall remain in the current state.

7.2.3.5.10 Transmission time limit reached with transmitter(s) in transmitter list (Timer T207 expires with transmitter(s))

When the timer T207 (Stop talking) expires and if at least one transmitter information is stored in transmitter list, the transmission participant:

1. shall request the MCVideo client to stop sending RTP media packets towards other MCVideo clients;

2. shall send the Transmission Arbitration Release message toward the other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field;

b. shall include the MCVideo ID of the first transmission participant in the transmitter list in the Next Arbitrator field;

c. shall remove the first transmission participant from the transmitter list;

d for the remaining transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field; and

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field; and

3. shall start timer T208 (Transmission Arbitration Release) and shall initiate counter C208 (Transmission Arbitration Release) to 1; and

4. shall enter the ‘O: pending delegated’ state.

7.2.3.5.11 Transmission time limit reached with no transmitter in transmitter list (Timer T207 expires with no transmitter)

When the timer T207 (Stop talking) expires and if no transmitter information is stored in transmitter list, the transmission participant:

1. shall send a Transmission Arbitration Release message towards other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field; and

b. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call);

2. shall start timer T230 (Inactivity); and

3. shall enter ‘O: silence’ state.

7.2.3.5.12 Receive RTP media (R: RTP media)

Upon receiving RTP media packets and with SSRC not associated with any transmitter stored in the transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall store the SSRC of RTP media packet in the transmitter list as unknown user;

3. shall start timer T203 (End of RTP media) associated with the SSRC; and

4. shall remain in ‘O: transmission arbitration’ state.

Otherwise, if SSRC of transmission participant sending the media matches the stored SSRC of a user in transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall restart timer T203 (End of RTP media) associated with the User ID; and

3. shall remain in ‘O: transmission arbitration’ state.

7.2.3.5.13 Timer T205 (Transmission Granted) expired (timer T205 expired)

On expiry of timer T205 (Transmission Granted) and counter C205 (Transmission Granted) is less than the upper limit, the transmission participant:

1. shall send the Transmission Granted message toward the other transmission participants. The Transmission Granted message:

a. shall include the MCVideo ID of the granted transmission participant in the User ID field;

b. shall include the SSRC of the granted transmission participant in the SSRC of the granted transmission participant field; and

c. 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 T205 (Transmission Granted) and shall increment counter C205 (Transmission Granted) by 1; and

3. shall remain in the current state.

7.2.3.5.14 Timer T205 (Transmission Granted) expired N times (Timer T205 expired N times)

On the expiry of timer T205 (Transmission Granted) for the configured upper limit of counter C205 (Transmission Granted), the transmission participant:

1. shall reset the value of counter C205 (Transmission Granted) to 1;

2. shall remain in the current state.

7.2.3.5.15 Timer T203 (End of RTP media) expired

On expiry of T203 (End of RTP media) timer, the transmission participant:

1. may provide transmission lost notification to the MCVideo user.

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall remove the User ID matching with the SSRC of RTP media packet from transmitter list; and

4. shall remain in the current state.

7.2.3.6 State: ‘O: has permission’

7.2.3.6.1 General

In this state the MCVideo client has the permission to send media.

Timer T206 (Stop talking warning) and timer T207 (Stop Talking) are running in this state.

7.2.3.6.2 Send RTP Media packets (S: RTP Media)

Upon receiving encoded media from the user or if encoded media is already buffered the transmission participant:

1. shall start timer T206 (Stop talking warning);

2. shall request the MCVideo client to start sending RTP media packets towards other MCVideo clients; and

3. shall remain in ‘O: has permission’ state.

7.2.3.6.3 Receive Transmission Release message (R: Transmission Release)

When a Transmission Release message is received and if the User ID in the Transmission Release message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission released notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Release message;

4. shall delete the User ID from the transmitter list; and

5. shall remain in ‘O: has permission’ state.

7.2.3.6.4 Send Transmission Release message (click video transmission end button)

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

1. shall stop timer T206 (Stop talking warning), if running;

2. shall stop timer T207 (Stop talking), if running;

3. shall send a Transmission Release message towards other transmission participants. The Transmission Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field; and

b. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call); and

4. shall enter ‘O: has no permission’ state.

7.2.3.6.5 Receive RTP media (R: RTP media)

Upon receiving RTP media packets and with SSRC not associated with any transmitter stored in the transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall store the SSRC of RTP media packet in the transmitter list as unknown user;

3. shall start timer T203 (End of RTP media) associated with the SSRC; and

4. shall remain in ‘O: has permission’ state.

Otherwise, if SSRC of transmission participant sending the media matches the stored SSRC of a user in transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall restart timer T203 (End of RTP media) associated with the User ID; and

3. shall remain in ‘O: has permission’ state.

7.2.3.6.6 Transmission time limit warning (Timer T206 expires)

When timer T206 (Stop talking warning) expires, the transmission participant:

1. may notify the MCVideo user that the transmition time limit is about to reach;

2. shall start timer T207 (Stop talking); and

3. shall remain in the current state.

7.2.3.6.7 Transmission time limit (Timer T207 expires)

When the timer T207 (Stop talking) expires, the transmission participant:

1. shall send a Transmission Release message towards other transmission participants. The Transmission Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field; and

b. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call); and

2. shall enter ‘O: has no permission’ state.

7.2.3.6.8 Timer T203 (End of RTP media) expired

On expiry of T203 (End of RTP media) timer, the transmission participant:

1. may provide transmission lost notification to the MCVideo user.

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall delete the User ID matching with the SSRC of RTP media packet in transmitter list; and

4. shall remain in the current state.

7.2.3.6.9 Receive Transmission Granted message (R: Transmission Granted to other)

When a Transmission Granted message is received and if the <User ID> value in the User ID field does not match its own MCVideo ID, the transmission participant:

1. shall start timer T203 (End of RTP media) for the User ID;

2. shall store the user to whom the transmission was granted in the Transmission Granted message in transmitter list;

3. may provide a transmission taken notification to the MCVideo user;

4. shall remain in the ‘O: has permission’ state.

7.2.3.6.10 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received and there is no stored current transmission arbitrator, the transmission participant:

1. if the <User ID> value in the User ID field in Transmission Arbitration Taken message doesn’t match with User ID in transmitter list, shall start timer T203 (End of RTP media);

2. shall store the value of <User ID> field of the Transmission Arbitration Taken message as the current transmission arbitrator; and

3. shall remain in ‘O: has permission’ state.

7.2.3.6.11 Receive Transmission Arbitration Release message with next arbitrator to me (R: Transmission Arbitration Release with next arbitrator to me)

1. shall send the Transmission Arbitration Taken message toward the other transmission participants. The Transmission Arbitration Taken message:

a. shall include the transmission participant’s own SSRC in the SSRC field;

b. shall include the transmission participant’s own MCVideo ID in the User ID field; and

2. shall enter ‘O: transmission arbitration’ state.

7.2.3.6.12 Receive Transmission Revoked message (R: Transmission Revoked)

When a Transmission Revoked message is received and if the User ID in the Transmission Revoked message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission revoked notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Revoked message;

4. shall delete the User ID in transmitter list;

5. if the User ID in the Transmission Revoked message matches with the stored User ID of current transmission arbitrator, shall clear current transmission arbitrator; and

6. shall remain in ‘O: has permission’ state.

7.2.3.6.13 Receive Transmission Arbitration Release message with next arbitrator to other (R: Transmission Arbitration Release with next arbitrator to other)

1. shall update the identity of the transmission arbitrator to the identity of the user indicated in the Next Arbitrator field of the Transmission Arbitration release message

2. shall remain in the current state.

7.2.3.7 State: ‘O: pending request’

7.2.3.7.1 General

In this state the MCVideo client is waiting for a response to a Transmission request message.

In this state timer T201 (Transmission Request) is running.

To resolve race condition between multiple simultaneous transmission requests, the MCVideo client resets the counter associated with timer T201, if another transmission request with higher priority or higher SSRC, in case the priority is same, is received.

7.2.3.7.2 Receive RTP media (R: RTP media)

Upon receiving RTP media packets and with SSRC not associated with any transmitter stored in the transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall store the SSRC of RTP media packet in the transmitter list as unknown user;

3. shall start timer T203 (End of RTP media) associated with the SSRC; and

4. shall remain in ‘O: pending request’ state.

Otherwise, if SSRC of transmission participant sending the media matches the stored SSRC of a user in transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall restart timer T203 (End of RTP media) associated with the User ID; and

3. shall remain in ‘O: pending request’ state.

7.2.3.7.3 Receive Transmission Rejected message (R: Transmission Rejected)

Upon receiving Transmission Rejected message, if the <User ID> value in the User ID field matches its own MCVideo ID and User ID of transmission participant sending the Transmission Rejected message matches the stored User ID of current transmission arbitrator, the transmission participant:

Editor’s Note: How a new participant obtains the identity of the transmission arbitrator is FFS.

1. shall stop the timer T201 (Transmission Request);

2. shall provide transmission deny notification to the user;

3. may display the transmission deny reason to the user using information in the Reject Cause field; and

4. shall enter ‘O: has no permission’ state.

Otherwise, if the <User ID> value in the User ID field matches its own MCVideo ID and there is no stored the current transmission arbitrator, the transmission participant:

1. shall stop the timer T201 (Transmission Request);

2. shall set the stored User ID of the current transmission arbitrator to the value in the User ID of transmission control server field as received in the Transmission Rejected message;

3. shall provide transmission deny notification to the user;

4. may display the transmission deny reason to the user using information in the Reject Cause field; and

5. shall enter ‘O: has no permission’ state.

7.2.3.7.4 Send Transmission Release message (click video transmission end button with no transmitter)

When an indication from the MCVideo user to release the pending request for the transmission is received and if there is no transmitter in transmitter list, the transmission participant:

1. shall send a Transmission Release message towards other transmission participants. The Transmission Release message:

a. shall include the MCVideo ID of the MCVideo user in the <User ID> value of the User ID field; and

2. shall stop the timer T201 (Transmission Request);

3. shall start the timer T230 (Inactivity) and enter ‘O: silence’ state;

7.2.3.7.5 Send Transmission Release message (click video transmission end button with transmitter)

When an indication from the MCVideo user to release the pending request for the transmission is received and if at least one transmitter information is stored in transmitter list, the transmission participant:

1. shall send a Transmission Release message towards other transmission participants. The Transmission Release message:

a. shall include the MCVideo ID of the MCVideo user in the <User ID> value of the User ID field; and

b. if the session is not initiated as a broadcast group call with the B-bit set to ‘1’ (Broadcast group call), shall include a Transmission Indicator field set to ‘0’ (normal call);

2. shall stop the timer T201 (Transmission Request); and

3. shall enter ‘O: has no permission’ state;

7.2.3.7.6 Send Transmission Arbitration Taken message (Timer T201 expired N times)

When timer T201 (Transmission Request) expires and counter C201 (Transmission Request) reaches its upper limit, the transmission participant:

1. shall send the Transmission Arbitration Taken message toward the other transmission participants. The Transmission Arbitration Taken message:

a. shall include the transmission participant’s own SSRC in the SSRC field;

b. shall include the transmission participant’s own MCVideo ID in the User ID field; and

c. 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; and

2. shall enter ‘O: transmission arbitration’ state.

7.2.3.7.7 Receive Transmission Granted message (R: Transmission Granted to me)

Upon receiving Transmission Granted message and if the <User ID> value in the User ID field matches its own MCVideo ID and User ID of transmission participant sending the Transmission Granted message matches the stored User ID of current transmission arbitrator, the transmission participant:

1. shall stop timer T201 (Transmission Request);

2. may provide a transmission granted notification to the MCVideo user; and

3. shall enter ‘O: has permission’ state.

Otherwise, if the <User ID> value in the User ID field matches its own MCVideo ID and there is no stored User ID of the current transmission arbitrator, the transmission participant:

1. shall set the stored User ID of the current transmission arbitrator to User ID of transmission participant sending the Transmission Granted message;

2. shall stop timer T201 (Transmission Request);

3. may provide a transmission granted notification to the MCVideo user; and

4. shall enter ‘O: has permission’ state.

7.2.3.7.8 Receive Transmission Granted message with next arbitrator (R: Transmission Granted with next arbitrator to me)

1. shall stop timer T201 (Transmission Request);

2. clear the stored current transmission arbitrator;

3. shall store the transmitter list of the Transmission Granted message;

4. may provide a transmission granted notification to the MCVideo user; and

5. shall enter ‘O: has permission’ state.

7.2.3.7.9 Receive Transmission Granted message (R: Transmission Granted to other)

When a Transmission Granted message is received and if the <User ID> value in the User ID field does not match its own MCVideo ID, the transmission participant:

1. shall start timer T203 (End of RTP media) for the User ID;

2. shall store the user to whom the transmission was granted in the Transmission Granted message in transmitter list;

3. may provide a transmission taken notification to the MCVideo user;

4. if the Transmission Indicator field is included with the B-bit set to ‘1’ (Broadcast group call), shall provide a notification to the user indicating that this is a broadcast group call; and

5. shall remain in ‘O: pending request’ state.

7.2.3.7.10 Timer T201 (Transmission Request) expired (Timer T201 expired)

On expiry of timer T201 (Transmission Request) if the counter C201 (Transmission Request) has not reached its upper limit, the transmission participant:

1. shall send the Transmission Request message to other transmission participants. The Transmission Request message:

a. if a priority different than the default transmission priority is required, shall include the Transmission Priority field with the requested priority in the <Transmission Priority> element;

b. shall include the MCVideo ID of the own MCVideo user in the User ID field; and

c. 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 the timer T201 (Transmission Request) and increment counter C201 (Transmission Request) by 1; and

3. shall remain in the ‘O: pending request’ state.

7.2.3.7.11 Receive Transmission Request message (R: Transmission request)

Upon receiving Transmission Request message, if the priority of received request is higher than priority of the transmission participant or if the SSRC of received request is higher, if the priority is same, the transmission participant:

1. shall reset the value of the counter C201 (Transmission Request) to 1;

2. shall re-start timer T201 (Transmission Request); and

3. shall remain in ‘O: pending request’ state.

7.2.3.7.12 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received and there is no stored current transmission arbitrator, the transmission participant:

1. if the <User ID> value in the User ID field in Transmission Arbitration Taken message doesn’t match with User ID in transmitter list, shall start timer T203 (End of RTP media);

2. shall store the value of <User ID> field of the Transmission Arbitration Taken message as the current transmission arbitrator; and

3. shall remain in ‘O: pending request’ state.

7.2.3.7.13 Receive Transmission Release message (R: Transmission Release)

When a Transmission Release message is received and if the User ID in the Transmission Release message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission released notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Release message;

4. shall delete the User ID in transmitter list; and

5. shall remain in ‘O: pending request’ state.

7.2.3.7.14 Receive Transmission Revoked message (R: Transmission Revoked)

When a Transmission Revoked message is received and if the User ID in the Transmission Revoked message matches with a stored User ID in transmitter list, the transmission participant:

1. may provide transmission revoked notification to the MCVideo user;

2. shall request the MCVideo client to stop rendering received RTP media packets;

3. shall stop timer T203 (End of RTP media) for User ID in the Transmission Revoked message;

4. shall delete the User ID in transmitter list;

5. if the User ID in the Transmission Revoked message matches with the stored User ID of current transmission arbitrator, shall clear current transmission arbitrator; and

6. shall remain in ‘O: pending request’ state.

7.2.3.8 State: ‘O: pending delegated’

7.2.3.8.1 General

In this state the MCVideo client is waiting for another client to take over the role of transmission controller.

The timer T205 (Transmission Granted) and timer T208 (Transmission Arbitration Release) are running in this state.

7.2.3.8.2 Receive RTP media (R: RTP Media)

Upon receiving RTP media packets and with SSRC not associated with any transmitter stored in the transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall store the SSRC of RTP media packet in the transmitter list as unknown user;

3. shall start timer T203 (End of RTP media) associated with the SSRC; and

4. shall remain in ‘O: pending delegated’ state.

Otherwise, if SSRC of transmission participant sending the media matches the stored SSRC of a user in transmitter list, the transmission participant:

1. shall request the MCVideo client to render the received RTP media packets;

2. shall restart timer T203 (End of RTP media) associated with the User ID; and

3. shall remain in ‘O: pending delegated’ state.

7.2.3.8.3 Timer T205 (Transmission Granted) expired (timer T205 expired)

On expiry of timer T205 (Transmission Granted) and counter C205 (Transmission Granted) is less than the upper limit, the transmission participant:

1. shall send the Transmission Granted message toward the other transmission participants. The Transmission Granted message:

a. shall include the MCVideo ID of the granted transmission participant in the User ID field;

b. shall include the SSRC of the granted transmission participant in the SSRC of the granted transmission participant field;

c. shall include the MCVideo ID of the granted transmission participant in the Next Arbitrator field;

d for the remaining transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field;

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field; and

e. 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 T205 (Transmission Granted) and shall increment counter C205 (Transmission Granted) by 1; and

3. shall remain in ‘O: pending delegated’ state.

7.2.3.8.4 Timer T205 (Transmission Granted) expired N times with transmitter(s) in the transmitter list (Timer T205 expired N times and transmitter in transmitter list)

On the expiry of timer T205 (Transmission Granted) for the configured upper limit of counter C205 (Transmission Granted) and if there is transmitter(s) in transmitter list, the transmission participant:

1. shall reset the value of counter C205 (Transmission Granted) to 1;

2. shall send the Transmission Arbitration Release message toward the other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field ;

b. shall include the MCVideo ID of the first transmission participant in the transmitter list in the Next Arbitrator field;

c. shall remove the first transmission participant from the transmitter list;

d for the remaining transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field; and

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field; and

e. 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 T208 (Transmission Arbitration Release) and shall initiate counter C208 (Transmission Arbitration Release) to 1; and

4. shall remain in ‘O: pending delegated’ state.

7.2.3.8.5 Timer T205 (Transmission Granted) expired N times with no transmitter in the transmitter list (Timer T205 expired N times and no transmitter in transmitter list)

On the expiry of timer T205 (Transmission Granted) for the configured upper limit of counter C205 (Transmission Granted) and if at least one transmitter in transmitter list is stored, the transmission participant:

1. shall reset the value of counter C205 (Transmission Granted) to 1;

2. shall start timer T230 (Inactivity); and

. shall enter ‘O: silence’ state.

7.2.3.8.6 Click Video transmission send button

If the transmission participant receives an indication from the MCVideo user to send media, the transmission participant:

1. may notify the MCVideo user about rejection; and,

2. shall remain in ‘O: pending delegated’ state.

7.2.3.8.7 Receive Transmission Release message (R: Transmission Release)

Upon receiving a Transmission Release message, the transmission participant:

1. shall remove the sender of the Transmission Release message from the transmitter list, if the User ID in the transmission release message matches a User ID in the transmitter list; and

2. shall remain in ‘O: pending delegated’ state.

7.2.3.8.8 Receive Transmission Request message (R: Transmission Request)

When a Transmission Request message is received, the transmission participant:

1. shall send the Transmission Rejected message toward the other transmission participant. The Transmission Rejected message:

a. shall include in the Reject Cause field the <Reject Cause> value cause #1 (Transmission limit reached);

b. may include in the Reject Cause field an additional text string explaining the reason for rejecting the transmission request in the <Reject Phrase> value; and

c. shall include the User ID field received in the Transmission Request message; and

2. shall remain in ‘O: pending delegated’ state.

7.2.3.8.9 Receive Transmission Arbitration Taken message (R: Transmission Arbitration Taken)

When a Transmission Arbitration Taken message is received and if the User ID in the Transmission Arbitration Taken message matches with the stored User ID of next transmission arbitrator, the transmission participant:

1. shall set the stored current transmission arbitrator to the <User ID> value in the User ID field in the Transmission Arbitration Taken message; and

2. shall remain in ‘O: pending delegated’ state.

7.2.3.8.10 Timer T208 (Transmission Arbitration Release) expired (timer T208 expired)

On expiry of timer T208 (Transmission Arbitration Release) and counter C208 (Transmission Arbitration Release) is less than the upper limit, the transmission participant:

1. shall send the Transmission Arbitration Release message toward the other transmission participants. The Transmission Arbitration Release message:

a. shall include the MCVideo ID of the MCVideo user in the User ID field;

b. shall include the MCVideo ID of the first transmission participant in the transmitter list in the Next Arbitrator field;

c for the remaining transmission participants in the transmitter list:

i. shall include the MCVideo ID of the transmission participant in the User ID field; and

ii. shall include the SSRC of the transmission participant in the SSRC of transmission participant field; and

d. 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 T208 (Transmission Arbitration Release) and shall increment counter C208 (Transmission Arbitration Release) by 1; and

3. shall remain in ‘O: pending delegated’ state.

7.2.3.8.11 Timer T208 (Transmission Arbitration Release) expired N times with transmitter(s) in the transmitter list (Timer T208 expired N times and transmitter in transmitter list)

On the expiry of timer T208 (Transmission Arbitration Release) for the configured upper limit of counter C208 (Transmission Arbitration Release) and if there is transmitter(s) in transmitter list, the transmission participant:

1. shall reset the value of counter C208 (Transmission Arbitration Release) to 1;