6.3.6 Transmission control server state transition for general reception control
24.5813GPPMission Critical Video (MCVideo) media plane controlProtocol specificationRelease 18TS
6.3.6.1 General
The reception control arbitration logic in the transmission control server shall behave according to the state diagram and state transitions specified in this clause.
Figure 6.3.6.1-1 shows the general reception operation states (Gr states) and the state transition diagram.
Figure 6.3.6.1-1: Transmission control server state transition diagram for ‘general reception control operation’
The reception control arbitration logic in the transmission control server shall keep one instance of the ‘general transmission control operation’ state machine per MCVideo call.
If transmission control messages or RTP media packets arrives in a state where there is no procedure specified in the following clauses the transmission control arbitration logic in the transmission control server:
1. shall discard the transmission control message;
2. shall request the media distributor in the MCVideo server to discard any received RTP media packet; and
3. shall remain in the current state.
State details are explained in the following clauses.
6.3.6.2 State: ‘Start-stop’
6.3.6.2.1 General
When a new instance of the ‘general reception control operation’ state machine 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 or the related MCVideo call is released.
6.3.6.2.2 MCVideo call initialization
When an MCVideo call is initiated as specified in 3GPP TS 24.281 [2] and
1. if a confirmed indication is required and at least one invited MCVideo client has accepted the invitation;
2. if a confirmed indication is not required; or
then the reception control arbitration logic in the transmission control server:
1. shall create an instance of the ‘general reception control operation’ state machine;
2. shall wait for the ‘basic reception control operation towards the transmission participant’ to be initialized before continuing the following steps;
3. when the ‘basic reception control operation towards the transmission participant’ state machine is initialized and the initialised session is not a temporary group session:
a. shall enter the ‘G: Reception Idle’ state as specified in clause 6.3.6.3.2; or
6.3.6.3 State: ‘Gr: Reception Idle’
6.3.6.3.1 General
The reception control arbitration logic in the transmission control server is in this state when no MCVideo user currently accept the media invitation to receive media.
Timer T5 (Inactivity) can be running when the reception control arbitration logic in the transmission control server is in this state.
6.3.6.3.2 Enter the ‘Gr: Reception Idle’ state
When entering this state from any state except the ‘Start-stop’ state, the reception control arbitration logic in the transmission control server:
1. shall start timer T5 (Reception Inactivity);
2. shall initialise counter C7 (Reception Accepted) to 0;
3. shall set the general state to the ‘Gr: Reception Idle’ state;
6.3.6.3.3 Receive Media Transmission Notify message (R: Media Transmission Notify)
Upon receiving a media transmission request notify, the reception control arbitration logic in the transmission control server:
1. shall send the Media Transmission Notify message to all other transmission participants. The Media Transmission Notify message:
a. if a group call is a broadcast group call, system call, emergency call, an imminent peril call, shall include the Reception Mode field set to ‘0’ indicating automatic reception mode:
i. shall set the counter C11 (Count of Active Receivers for the stream), associate with the transmitter by the total number of receiving MCVideo clients who are participating in the call;
ii. shall store the SSRC of all the transmission participants who are participating in the call until the reception of media associated with Transmission notification is ended;
iii. shall set the C7 (Reception Accepted) value with a total number of active receivers of each stream and an associated stream of the recieved media transmission notification (i.e. Sum of all C11 counter values); and
iv. shall enter the ‘Gr: Reception Accepted’ state; and
b. if a group call is not a broadcast group call, system call, emergency call or an imminent peril call, shall include the Reception Mode field set to ‘1’ indicating manual reception mode:
i. shall start timer T11 (Stream Reception Idle) and associate it with the transmitter SSRC or UserId;
ii. shall initialize counter C11(Count of active receivers for the stream) to 0 and associate it with the transmitter SSRC or UserId; and
iii. shall remain in ‘Gr: Reception Idle’ state.
6.3.6.3.4 Void
6.3.6.3.5 Timer T5 (Reception Inactivity) expired
On expiry of timer T5 (Reception Inactivity) the reception control arbitration logic in the transmission control server based on a configurable service provider policy either:
1. shall indicate to the application and signalling plane that timer T5 (Reception Inactivity) has expired;
2. if the application and signalling planes initiates MCVideo call release, shall enter the ‘Releasing’ state; and
3. if the application and signalling planes do not initiate MCVideo call release:
a. should restart the T5 (Reception Inactivity) timer; and
b. shall remain in the ‘G: Reception Idle’ state.
6.3.6.3.6 Reception of Receive Media Request message (R: Receive Media Request)
Upon receiving a Receive Media Request message, the reception control arbitration logic in the transmission control server:
1. if the Receive Media Request is rejected:
a. shall send the Receive Media Response (Rejected) message. The Receive Media Response message:
i. 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; and
ii. shall include the Result field set to 0 (Receive media rejected); and
b. shall remain in ‘Gr: Reception idle’ state; or
2. if the Receive Media Request is granted:
a. shall stop timer T5 (Reception Inactivity);
b. shall stop timer T11(Stream Reception Idle) if running;
c. shall increment the counter C11 (Count of Active Receivers for the stream), associated with the transmitter SSRC by 1;
d. shall store the SSRC of transmission participant requesting to receive media until the reception is finished associated with that Transmission request;
e. shall send the Receive Media Response message. The Receive Media Response message:
i. 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; and
ii. shall include the Result field set to 1 (Receive media granted);
f. shall increase C7 (Reception Accepted) by 1 if it has not reach its upper limit; and
g. shall enter the ‘Gr: Reception accepted’ state.
6.3.6.3.7 Receive RTP media (R: RTP media)
Upon receiving RTP media, the reception control arbitration logic in the transmission control server:
1. shall instruct the media distributor to forward the RTP media packets to MCVideo clients according to local policy:
a. If discard is specified in the local policy for transmission without receiving MCVideo clients, shall discard the RTP packet;
b. If buffer is specified in the local policy for transmission without receiving MCVideo clients, shall buffer the RTP packet;
2. shall remain ‘Gr: Reception Idle’ state.
6.3.6.3.8 Receive Transmission End Notify message (R: Transmission End Notify)
Upon receiving a Transmission End Notify, the reception control arbitration logic in the transmission control server:
1. shall send the Transmission End Notify message to all other transmission participants.
2. shall stop timer T11(Stream Reception Idle) associated with the transmitter SSRC, if running;
3. shall remain in ‘Gr: Reception Idle’ state.
6.3.6.3.9 Timer T11(Stream Reception Idle) expired
On expiry of timer T11 (Stream Reception Idle) the reception control arbitration logic in the transmission control server
1. shall communicate to the transmission control arbitration logic in transmission control server to terminate the stream associated to the expired timer T11.
2. shall remain in the ‘Gr: Reception Idle’ state.
NOTE: Terminating the stream by sending Transmission Revoke message or Transmission End Request message is decided based on MCVideo server local policy.
6.3.6.4 State: ‘Gr: Reception accepted’
6.3.6.4.1 General
The reception control arbitration logic in the transmission control server is in this state when other MCVideo users currently accept the media invitation to receive media.
6.3.6.4.2 Enter the ‘Gr: Reception Accepted’ state
When entering this state from any state except the ‘Start-stop’ state, the reception control arbitration logic in the transmission control server:
1. shall stop timer T5 (Inactivity);
2. shall set the general state to the ‘Gr: Reception Accepted’ state;
6.3.6.4.3 Reception of Receive Media Request message (R: Receive Media Request)
Upon receiving a Receive Media Request message, the reception control arbitration logic in the transmission control server:
1. if the Receive Media Request is rejected:
a. shall send the Receive Media Response (Rejected) message. The Receive Media Response message:
i. 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; and
ii. shall include the Result field set to 0 (Receive media rejected); and
b. shall remain the ‘Gr: Reception accepted’ state; or
2. if the Receive Media Request is granted:
a. shall stop timer T5 (Inactivity);
b. shall stop timer T11(Stream Reception Idle) associated with the transmitter SSRC, if running;
c. shall increment the counter C11 (Count of Active Receivers for the stream), associated with the transmitter SSRC by 1;
d. shall store the SSRC of transmission participant requesting to receive media until the reception is finished associated with that Transmission request;
e. shall send the Receive Media Response (Granted) message. The Receive Media Response message:
i. 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; and
ii. shall include the Result field set to 1 (Receive media granted);
f. shall start timer T6 (Reception Granted);
g. shall increase C7 (Reception Accepted) by 1 if it has not reach its upper limit; and
h. shall remain in ‘Gr: Reception accepted’ state.
6.3.6.4.4 Reception of Receive Media End Request message (R: Receive Media End Request)
Upon receiving a Receive Media End Request message, the reception control arbitration logic in the transmission control server:
1.. shall send the Receive Media End Response message. The Receive Media End Response message:
a.. the first bit in the subtype of the Receive media end response message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message.
b. shall include the Message Type field set to ‘y’ (Receive media end granted);
2.. shall stop timer T6 (Reception Granted);
3. shall decrement the counter C11 (Count of Active Receivers for stream) by 1, if it has not reach its lower limit;
4. if C11 has reached its lower limit, shall start timer T11 (Stream Reception Idle);NOTE: Decision to start same timer T11 or a new timer, when all the participants have stopped reception, can be taken based on MCVideo server local policy.
5. shall decrease C7 (Reception Accepted) by 1 if it has not reach its lower limit;
6. if C7 has not reached it lower limit, shall remain in ‘Gr: Reception accepted’ state.
7. if C7 has reached it lower limit, shall enter the ‘Gr: Reception Idle’ state.
6.3.6.4.5 Reception of Receive Media End Response message (R: Receive Media End Response)
Upon receiving a Receive Media End Response message, the reception control arbitration logic in the transmission control server:
1. if the the first bit in the subtype of the Receive media end response message is set to ‘1’ (Acknowledgment is required) as described in clause 9.2.2.1, shall send a Transmission control Ack message.
2. shall stop timer T6 (Reception Granted);
3. shall decrement the counter C11 (Count of Active Receivers for the stream) by 1, if it has not reach its lower limit;
4. if C11 has reached its lower limit, shall start timer T11 (Stream Reception Idle);
NOTE: Decision to start same timer T11 or a new timer, when all the participants have stopped reception, can be taken based on MCVideo server local policy.
5. shall decrease C7 (Reception Accepted) by 1 if it has not reach its lower limit;
6. if C7 has not reached its lower limit, shall remain in ‘Gr: Reception accepted’ state.
7. if C7 has reached its lower limit, shall enter the ‘Gr: Reception Idle’ state.
6.3.6.4.6 Void
6.3.6.4.7 Receive RTP media (R: RTP media)
Upon receiving a RTP media, the reception control arbitration logic in the transmission control server:
1. shall instruct the media distributor to forward the RTP media packets to MCVideo clients according to local policy; and
2. shall remain the ‘Gr: Reception accepted’ state.
6.3.6.4.8 Timer T6 (Reception Granted) expires
On expiry of timer T6 (Reception Granted) the reception control arbitration logic in the transmission control server:
1. shall send a Receive Media Response (Granted) message to the granted transmission participant if counter C6 (Reception Granted) has not reached its upper limit.
2. shall start timer T6 (Reception Granted) and increment counter C6 (Reception Granted) by 1 if counter C6 (Reception Granted) has not reached its upper limit; and
3. shall remain in the ‘G: Reception accepted’ state.
6.3.6.4.9 Timer T6 (Reception Granted) expired N times
When timer T6 (Reception Granted) expires and counter C6 (Reception Granted) reaches its upper limit, the reception control arbitration logic in the transmission control server:
1. shall remain in the ‘G: Reception Accepted’ state.
6.3.6.4.10 Receive Media Transmission Notify message (R: Media Transmission Notify)
Upon receiving a media transmission request notify message from the reception control arbitration logic in the transmission control server:
1. shall send the Media Transmission Notify message to all other transmission participants. The Media Transmission Notify message:
a. if a group call is a broadcast group call, system call, emergency call or an imminent peril call, shall include the Reception Mode field set to ‘0’ indicating automatic reception mode:
i. shall set the counter C11 (Count of Active Receivers for the stream), associated with the transmitter by the total number of receiving MCVideo clients who are participating in the call;
ii shall store the SSRC of all the transmission participants who are participating in the call until the reception of media associated with Transmission notification is ended; and
iii shall set C7 (Reception Accepted) value with a total number of active receivers of each stream and an associated stream of the recieved media transmission notification (i.e. Sum of all C11 counter values); and
b. if a group call is not a broadcast group call, system call, emergency call or an imminent peril call, shall include the Reception Mode field set to ‘1’ indicating manual reception mode:
i. shall start timer T11 (Stream Reception Idle) and associate it with the transmitter SSRC or UserId present in Media Transmission Notify message; and
ii shall initialize a counter C11(Count of Active Receivers for the stream) to 0 & associate it with the transmitter SSRC or UserId present in Media Transmission Notify message; and
2. shall remain in the ‘Gr: Reception Accepted’ state.
6.3.6.4.11 Receive Transmission End Notify message (R: Transmission End Notify)
Upon receiving a Transmission End Notify message, the reception control arbitration logic in the transmission control server:
1. shall send the Transmission End Notify message to all other transmission participants.
2. shall stop timer T11(Stream Reception Idle) associated with the transmitter SSRC, if running;
3. shall decrease C7 (Reception Accepted) by the value of C11(Count of Active Receivers for the stream) associated with the transmitter SSRC or UserId present in Transmission End Notify message;
4. if C7 has not reached it lower limit, shall remain the ‘Gr: Reception accepted’ state.
5. if C7 has reached it lower limit, shall enter the ‘Gr: Reception Idle’ state.
6.3.6.4.12 Timer T11(Stream Reception Idle) expired
On expiry of timer T11 (Stream Reception Idle), the reception control arbitration logic in the transmission control server
1. shall communicate to the transmission control arbitration logic in transmission control server to terminate the stream associated to the expired timer T11.
2. shall remain in ‘Gr: Reception Accepted’ state.
NOTE: Terminating the stream by sending Transmission Revoke message or Transmission End Request message is decided based on MCVideo server local policy.
6.3.6.5 State: ‘Gr: Any state’
6.3.6.5.1 General
This clause describes the actions to be taken in all states defined for the general state diagram with the exception of the ‘Start-stop’ state.
6.3.6.5.2 Receive MCVideo call release – 1
This clause is used by the reception control arbitration logic in the transmission control server when an MCVideo call is released.
Upon receiving an MCVideo call release step 1 request from the application and signalling plane the transmission control arbitration logic in the transmission control server:
1. shall request the media distributor in the MCVideo server to stop sending RTP media packets MCVideo clients; and
2. shall enter the ‘Releasing’ state.
6.3.6.6 State: ‘Gr: Releasing’
6.3.6.6.1 General
The reception control arbitration logic in the transmission control server uses this state while waiting for the application and signalling plane to finalize the disconnection of an MCVideo call.
6.3.4.6.2 Receive MCVideo call release – 2
Upon receiving an MCVideo call release step 2 request from the application and signalling plane, the reception control arbitration logic in the transmission control server:
1. shall release all resources reserved in the media plane including the instances used for the ‘transmission control server state transition diagram for general reception control operation’, and ‘Transmission control server state transition diagram for basic reception control operation towards the transmission participant’ state machines and any running timers associated with the state machines; and
2. shall enter the ‘Start-stop’ state.