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Multicast/Broadcast Communication With Acknowledge

Multicast/Broadcast Communication With Acknowledge. Authors:. Date: 2008-07-21. 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: 2008-07-21 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. Add feedback to broadcast/multicast frames. Methods to make Broadcast/Multicast Reliable Liwen Chu Etc.

  6. An AP selects a single STA to feedback an ACK to the multicast/broadcast frame. It is the most efficient, but least reliable solution. An 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. An 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 An AP must select STAs to reply with blockAcks using blockAck request. An AP allocates the start offset and duration of the blockAck replies. Feedback for Multiple (BlockAck) Multicast/broadcast Frames Liwen Chu Etc.

  8. A STA with the capability to join an MBBA group sends an Add multicast/broadcast blockAck (ADDMBBA) Request frame to the AP. After receiving an ADDMBBA Request frame, an AP replies with an ADDMBBA Response frame to the STA with the capability to join an MBBA group 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 an AP that it will leave the MBBA group. Multicast/broadcast Joining/Leaving Procedure Liwen Chu Etc.

  9. If an AP wants to tear down the group, it sends via unicast/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. An 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, an 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, an AP may use the normal blockAck procedure to retransmit the frames to the STA. When only a few frames need to be retransmitted, an 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 BA: BlockAck Backoff Backoff MBBA Req BA Req AP1 Multicast Data Frames Multicast Data Frames MBBA Ack STA1 MBBA Ack STA2 MBBA Ack corrupted STA3 BA 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 STA3 BA Normal BlockAck for Retransmission MBBA TXOP Backoff Backoff STA5 Liwen Chu Etc.

  15. Before the MBBA txop, an AP can select more than one MBBA group member and use MBBA Req/MBBA Ack to protect the MBBA TXOP. STA8 AP2 AP1 AP3 STA4 STA7 STA1 STA2 STA6 STA3 STA5 STA9 MBBA TXOP Protection Methods MBBA TXOP Backoff MBBA Req MBBA Req AP1 MBBA Ack Multicast Data Frames MBBA Ack STA1 MBBA Ack MBBA Ack STA2 MBBA Ack STA3 Protection Stage Broadcast/Multicast Tx Stage Liwen Chu Etc.

  16. Before the MBBA txop, an AP can select a MBBA group member and use RTS/CTS to protect the MBBA TXOP. AP2 AP1 STA4 STA2 STA1 STA6 STA3 STA5 MBBA TXOP Protection Methods (Cont’d) MBBA TXOP Backoff MBBA Req AP1 RTS Multicast Data Frames MBBA Ack STA1 MBBA Ack STA2 CTS MBBA Ack STA3 Protection Stage Broadcast/Multicast Tx Stage Liwen Chu Etc.

  17. An AP selects one or more STAs that transmit protection frames in the protection stage to neighboring OBSS. An 802.11k neighbor report or other method may be used to select STAs to transmit protection frames. The selected STAs should cover all neighboring OBSS in order to minimize collisions. MBBA TXOP Protection Methods (Cont’d) Liwen Chu Etc.

  18. PSMP can be used as reliable multicast/broadcast communication. But PSMP need protection before PSMP transmission to avoid OBSS collision. Method 1: before the PSMP TXOP, an AP can select more than one multicast group member and use PSMP/Null frame (other protection frames may be used instead) to protect the PSMP TXOP. No downlink data frames are transmitted. The uplink duration only allows a null frame to be transmitted. If there are buffered frames to the AP, the STA will respond with a null frame to request more uplink TXOP. If there is no buffered frame, the STA will respond with a null frame to indicate no buffered frames. Method 2: before the PSMP TXOP, an AP can select a multicast group member and use RTS/CTS (protection frame) to protect the PSMP TXOP. PSMP TXOP Protection Methods Liwen Chu Etc.

  19. An AP selects one or more STAs that transmit protection frames in the protection stage to neighboring OBSS. An 802.11k neighbor report or other method may be used to select STAs to transmit protection frames. The selected STAs should cover all neighboring OBSS in order to minimize collisions. PSMP TXOP Protection Methods (Cont’d) Liwen Chu Etc.

  20. STA8 AP2 AP1 AP3 STA4 STA7 STA1 STA2 STA6 STA3 STA5 STA9 PSMP TXOP Protection Methods (Cont’d) MBBA TXOP Backoff AP1 PSMP PSMP STA1 MTBA Multicast Data Frames Null frame STA1 STA2 MTBA Null frame STA2 STA3 MTBA STA3 Protection Stage Broadcast/Multicast Tx Stage Liwen Chu Etc.

  21. AP2 AP1 STA4 STA2 STA1 STA6 STA3 STA5 PSMP TXOP Protection Methods (Cont’d) MBBA TXOP Backoff AP1 PSMP RTS Multicast Data Frames STA1 MTBA STA1 STA2 MTBA STA2 CTS STA3 MTBA STA3 Protection Stage Broadcast/Multicast Tx Stage Liwen Chu Etc.

  22. Multiple BlockAckReq/Blockack in a TXOP can be used as reliable multicast/broadcast communication. But multiple BlockAck TXOP need protection before PSMP transmission to avoid OBSS collision. Method 1: before the Multiple BlockAck TXOP, the AP can select more than one multicast group member and use multiple RTS/CTS or modified RTS (multicast RTS)/CTS (other protection frames may be used instead) to protect the PSMP TXOP. After receiving multicast RTS, multicast destinations return CTS based on the sequence indicated by the AP. Method 2: before the Multiple BlockAck TXOP, the AP can select a multicast group member and use RTS/CTS (protection frame) to protect the Multiple BlockAck TXOP. Multiple BlockAckReq/BlockAck (Leader) Based TXOP Protection Methods Liwen Chu Etc.

  23. An AP selects one or more STAs that transmit protection frames in the protection stage to neighboring OBSS. An 802.11k neighbor report or other method may be used to select STAs to transmit protection frames. The selected STAs should cover all neighboring OBSS in order to minimize collisions. Multiple BlockAckReq/BlockAck (Leader) Based TXOP Protection Methods (Cont’d) Liwen Chu Etc.

  24. BA Req BA Req BA Req STA8 AP2 AP1 AP3 STA4 STA7 STA1 STA2 STA6 STA3 STA5 STA9 Multiple BlockAckReq/BlockAck (Leader) Based TXOP Protection Methods (Cont’d) MBBA TXOP Backoff AP1 RTS RTS Multicast Data Frames STA1 CTS BA STA2 CTS BA STA3 BA Broadcast/Multicast Tx Stage Protection Stage Backoff MRTS AP1 CTS STA1 CTS STA2 STA3 Protection Stage Liwen Chu Etc.

  25. BA Req BA Req BA Req AP2 AP1 STA4 STA2 STA1 STA6 STA3 STA5 Multiple BlockAckReq/BlockAck (Leader) Based TXOP Protection Methods (Cont’d) MBBA TXOP Backoff AP1 RTS Multicast Data Frames STA1 BA STA2 CTS BA STA3 BA Protection Stage Broadcast/Multicast Tx Stage Liwen Chu Etc.

  26. An AP can reserve TXOP for video communication (HCCA etc.). Before the multicast video transmission in a reserved TXOP, STAs selected by the AP can transmit CTS2Self to protect the video transmission. An AP selects one or more STAs that transmit protection frames in the protection stage to neighboring OBSS. An 802.11k neighbor report or other method may be used to select STAs to transmit protection frames. The selected STAs should cover all neighboring OBSS in order to minimize collisions. Protection Methods for Reserved Multicast TXOP Liwen Chu Etc.

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