BlockAck Enhancement for Multicast Transmissions November 2007 2/22/2019May 2008 doc.: IEEE 802.11-07/2752r1 BlockAck Enhancement for Multicast Transmissions Date: 2008-7-11 Authors: Hang Liu, et. al, Thomson Inc. Peter Ecclesine, Cisco Systems

November 2007 2/22/2019May 2008 doc.: IEEE 802.11-07/2752r1 Abstract This contribution proposes BlockAck enhancements to improve link reliability for multicast/broadcast transmissions Hang Liu, et. al, Thomson Inc. Peter Ecclesine, Cisco Systems

Outlines Problems for Multicast in 802.11 November 2007 2/22/2019May 2008 doc.: IEEE 802.11-07/2752r1 Outlines Problems for Multicast in 802.11 Multicast BlockAck with Immediate Policy Multicast BlockAck with Delayed Policy Multicast BlockAck with PSMP Hang Liu, et. al, Thomson Inc. Peter Ecclesine, Cisco Systems

Problems for Multicast/Broadcast in 802.11 2/22/2019May 2008 Problems for Multicast/Broadcast in 802.11 Collision in the BSS (intra-BSS Collision) The associated STAs transmit when an AP is transmitting multicast/broadcast frames Overlapping BSS (OBSS) Collision (Inter-BSS Collision) The STAs/APs in OBSSes transmit when an AP is transmitting multicast/broadcast frames Hidden node problem Link transmission errors No ACK Collision S2 S1 S1 Collision S7 AP1 AP2 S5 S4 S3 S6 S3 S2 AP2 is a hidden node to AP1 Hang Liu, et. al, Thomson Inc.

Multicast BlockAckReq with Immediate Block Ack Policy Multicast Block Ack exchange Multicast data block (BAR control, BAR Info, Receiver Info) Sender/AP Frame-exchange for NAV Protection Data Data M-Block AckReq M-Block Ack Receiver/STA1 Receiver/STA 2 M-Block Ack Receiver/STA 3 Not included in the BlockAck-requested receiver list Multicast BlockAckReq (M-BlockAckReq) contains a list of BlockAck-requested receiver identifiers (in the form of receiver bitmap control and partial virtual bitmap field) The STAs send their M-BlockAck in the order that they are specified in the receiver bitmap of the M-BlockAckReq Hang Liu, et. al, Thomson Inc.

Multicast BlockAck and Retransmission M-BlockAckReq or M-BlockAck may be lost If AP does not successfully receive the M-BlockAcks from all the intended recipient STAs, then retransmits the M-BlockAckReq with the remaining STAs in the receiver bitmap field from which the M-BlockAck have not received the remaining STAs respond with an M-BlockAck in the order listed in the M-BlockAckReq receiver bitmap this process is repeated until the AP receives M-BlockAcks from all the intended STAs or the number of retransmission attempts has reached to a limit. After M-BlockAckReq and M-BlockAck exchanges, the AP determines from the information in the received M-BlockAck bitmap whether a frame needs to be retransmitted. If a frame is lost (not correctly received by one or more intended multicast recipient STAs), the AP arranges the retransmissions of the lost frame. The retransmitted frames are sent multicast After retransmitting the lost frames and/or transmitting new frames, the AP can initiate a new M-BlockAckReq and M-BlockAck exchange to obtain the receiving status of (re)transmitted frames. This retransmission process can be repeated for a lost frame until all the intended recipient STAs that sent the M-BlockAck receive the frame correctly or the lifetime of this frame expires. Hang Liu, et. al, Thomson Inc.

M-BlockAckReq Frame Frame Control Duration /ID Receiver Information RA TA BAR Control BAR Information FCS BAR Receiver Bitmap Control BAR Receiver Partial Bitmap Type/Flags BAR receiver bitmap control subfield (1 octet): Bitmap Offset Value N = STA’s AID divided by 16 Bit 0 reserved and bits 1-7 Bitmap Offset Each bit in the BAR receiver partial virtual bitmap subfield corresponds to a specific station Bit i corresponds to the STA with an AID of 16 x N + i. The length of partial virtual bitmap varies and is a multiple of octets, which can be determined from the total frame size. If bit i in the receiver bitmap field is set to 1, then the station with AID 16 x N + i is requested to reply to this M-BlockAckReq with M-BlockAck, Hang Liu, et. al, Thomson Inc.

M-BlockAck Frame Frame Control BA Information Duration/ID RA TA BA Control FCS BA Ack Policy Multi- TID Compressed Bitmap Multi- cast Reserved TID_Info BA Control Field Block Ack Starting Sequence Control BA Information field (BlockAck or Compressed BlockAck) Block Ack Bitmap Block Ack Starting Sequence Control BA Information field (Multi-TID BlockAck) Per TID Info Block Ack Bitmap Hang Liu, et. al, Thomson Inc.

M-BlockAckReq & M-BlockAck Exchange Sequence with Delayed Policy and Ack Multicast Block Ack Request and ACK Delayed multicast Block Ack and ACK Multicast data block Sender/AP (BAR Control, BAR Info, Receiver Info) Frame-exchange for NAV Protection Data Data M-Block AckReq Ack Ack M-Block Ack Ack Receiver/STA 1 Ack M-Block Ack Receiver/STA 2 Receiver/STA 3 Not included in the block ack-requested receiver list Hang Liu, et. al, Thomson Inc.

Delayed multicast Block Ack Multicast Block Ack Request M-BlockAckReq &M-BlockAck Exchange Sequence with Delayed Policy and No Ack Delayed multicast Block Ack Multicast data block Multicast Block Ack Request Sender/AP (BAR Control, BAR Info, Receiver Info) Frame-exchange for NAV Protection Data Data M-Block AckReq M-Block Ack Receiver/STA 1 M-Block Ack Receiver/STA 2 Receiver/STA 3 Not included in the blockack-requested receiver list Hang Liu, et. al, Thomson Inc.

M-BlockAckReq & M-BlockAck Exchange Sequence with PSMP MP Originator /AP Downlink phase PSMP Multicast Data Block Other multicast or unicast data blocks Multi-cast Data Multi-cast Data M-Block AckReq Uni-cast data STA 1 uplink data block Uplink phase M-Block Ack Up-link data Receiver/STA 1 STA 2 uplink data block M-Block Ack Receiver/STA 2 STA 3 uplink data block Up-link data Receiver/STA 3 Not included in the blockack-requested receiver bitmap of M-BlockAckReq Hang Liu, et. al, Thomson Inc.

Thank You! Questions? Hang Liu, et. al, Thomson Inc.