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Multicast/Broadcast Communication With Acknowledge

Multicast/Broadcast Communication With Acknowledge. Authors:. Date: 2008-07-08. Abstract. Audio video requires reliable transmissions and deterministic delay.

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Multicast/Broadcast Communication With Acknowledge

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  1. Multicast/Broadcast Communication With Acknowledge Authors: Date: 2008-07-08 Liwen Chu Etc.

  2. Abstract Audio video requires reliable transmissions and deterministic delay. Currently, it is difficult to provide reliable audio video transmissions in 802.11 because of the poor support of broadcast/multicast transmission, and because EDCA cannot provide a deterministic delay guarantee. This contribution proposes the use of blockAck based methods to provide reliable audio video transmission. The proposed methods do not require any physical layer modifications. Liwen Chu Etc.

  3. Graceful degradation of audio video streams when there is insufficient channel capacity, by enabling packet discarding without any requirement for deep packet inspection, Increased robustness in OBSS environments, without the requirement for a centralised management entity, Intra-Access Category prioritization of transport streams by modifying EDCA timing and parameter selection without any requirement for deep packet inspection, Improved link reliability and low jitter characteristics for multicast/broadcast audio video streams, Interworking with relevant 802.1AVB mechanisms (802.1Qat, 802.1Qav, 802.1AS) MAC Enhancements in VTS PAR Liwen Chu Etc.

  4. Intra BSS collision: Associated STAs transmit frames when an AP is transmitting broadcast/multicast frames. Inter BSS collision (OBSS collision): OBSS STAs/APs transmit frames when an AP is transmitting broadcast/multicast frames. No feedback to indicate the correct reception of the broadcast/multicast frames Reasons why Broadcast/Multicast is Unreliable AP Collision! AP2 AP1 STA4 Collision! STA1 STA3 STA1 STA3 STA6 STA2 STA2 STA5 Collision! Inter BSS collision Intra BSS (OBSS) collision Liwen Chu Etc.

  5. Decrease the probability of a broadcast/multicast collision. Decrease the impact of a broadcast/multicast collision. Add feedback to broadcast/multicast frames. Methods to make Broadcast/Multicast Reliable Liwen Chu Etc.

  6. The AP selects a single STA to feedback an ACK to the multicast/broadcast frame. It is the most efficient, but least reliable solution. The AP selects many STAs to feedback ACK frames and specifies the sequence for the replies (start offset, duration). It is a less efficient solution, since more than one ACK will respond to a multicast/broadcast frame, but is more reliable. Feedback for a Single Multicast/broadcast Frame Liwen Chu Etc.

  7. The AP must maintain a multicast/broadcast blockAck (MBBA) group (the AP and all STAs of the multicast/broadcast blockAck destinations are defined as a MBBA group). STA joining procedure STA leaving procedure MBBA group teardown procedure The AP must select STAs to reply with blockAcks using blockAck request. The AP allocates the start offset and duration of the blockAck replies. Feedback for Multiple (BlockAck) Multicast/broadcast Frames Liwen Chu Etc.

  8. The AP sends an Add multicast/broadcast blockAck (ADDMBBA) Request frame to a STA with the capability to join an MBBA group. After receiving an ADDMBBA Request frame, a STA with the capability to join an MBBA group replies with an ADDMBBA Response frame to the AP in order to complete the joining. If a STA wants to leave an MBBA group, it uses a Leave multicast/broadcast blockAck (LVMBBA) frame to tell the AP that it will leave the MBBA group. Multicast/broadcast Joining/Leaving Procedure Liwen Chu Etc.

  9. If the AP wants to tear down the group, it sends via multicast/broadcast a Leave multicast/broadcast blockAck (LVMBBA) frame to each STA in the MBBA group. If all STAs have left a MBBA group, the AP tears down the MBBA group. MBBA Group Teardown Procedure Liwen Chu Etc.

  10. Multicast/broadcast BlockAck only support the immediate blockAck policy. The AP uses MBBA Request (MBBAReq) frames to request all or part of destination STAs to respond MBBA Ack frames MBBA Request frame indicates when a STA will reply a MBBA Ack frame The following fields are required in MBBAReq in addition to the fields in BlockAckReq frame: AID (STA identifier) MBBA Ack start offset The start offset is the offset relative to the start of MBBA Req frame MBBA Ack duration The duration is used for MBBA Ack transmission Multicast/Broadcast BlockAck Procedure Liwen Chu Etc.

  11. AP1, STA1, STA2, STA3 are in a MBBA group. STA4 AP1 STA1 STA3 STA2 Multicast/Broadcast BlockAck Example Multicast Data Frames Backoff MBBA Req AP1 MBBA Ack STA1 MBBA Ack STA2 MBBA Ack STA3 MBBA TXOP Liwen Chu Etc.

  12. When many of the indicated STAs do not receive the multicast/broadcast frames correctly, the AP may use the MBBA mechanism to retransmit the multicast/broadcast frames. A STA which receives the multicast/broadcast frames more than once will discard the repeated frames, but must reply with an MBBA Ack frame if requested by the AP. When a few of the indicated STAs do not receive the multicast/broadcast frames correctly, the AP may use the normal blockAck procedure to retransmit the frames to the STA. When only a few frames need to be retransmitted, the AP may send frames with normal ack policy. Multicast/Broadcast BlockAck Retransmission Procedure Liwen Chu Etc.

  13. AP1, STA1, STA2, STA3 are in a MBBA group. STA4 AP1 STA1 STA3 STA2 Multicast/Broadcast BlockAck Retransmission Example Backoff Backoff MBBA Req BA Req AP1 Multicast Data Frames Multicast Data Frames MBBA Ack STA1 MBBA Ack STA2 MBBA Ack corrupted BA Ack STA3 Normal BlockAck for Retransmission MBBA TXOP Liwen Chu Etc.

  14. Non protected MBBA TXOP may have a high chance to collide with other transmission. BlockAck recommend to use RTS/CTS, HCCA etc. protection mechanism to protect the blockAck transmission. STA7 AP2 AP1 STA4 STA1 STA3 STA6 STA2 STA5 Collision! Possible MBBA Collision Backoff Backoff MBBA Req AP1 BA Req Multicast Data Frames Multicast Data Frames MBBA Ack STA1 MBBA Ack STA2 Corrupted frames Corrupted MBBA Req BA Ack STA3 Normal BlockAck for Retransmission MBBA TXOP Backoff Backoff STA5 Liwen Chu Etc.

  15. Before the MBBA txop, the AP can select more than one MBBA group member and use MBBA Req/MBBA Ack to protect the MBBA TXOP. Before the MBBA txop, the AP can select a MBBA group member and use RTS/CTS to protect the MBBA TXOP. STA4 AP1 STA1 STA3 STA2 MBBA TXOP Protection Methods Backoff MBBA Req MBBA Req AP1 MBBA Ack Multicast Data Frames MBBA Ack STA1 MBBA Ack MBBA Ack STA2 MBBA Ack STA3 MBBA TXOP Backoff MBBA Req AP1 RTS Multicast Data Frames MBBA Ack STA1 MBBA Ack STA2 CTS MBBA Ack STA3 MBBA TXOP Liwen Chu Etc.

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