Proposed Modifications to 802.11e-D4.0 Group ACK

1. Proposed Modifications to 802.11e-D4.0 Group ACK • Carlos Rios, RiosTek LLC

2. D4.0 Group ACK Summary • Group ACK per 802.11e-D4.0 is a relatively involved protocol to allow QSTAs to burst transmissions to another QSTA while deferring any and all corresponding ACKs until after a later (Group) ACK request. • Upon association, sender QSTA gleans from (Association frame) Capabilities Info field that candidate receiver QSTA is capable of Group ACK • Group ACK is set up, characterized and torn down with Action Frames:Sender transmits ADDGA Request to set up GA with receiverReceiver responds with ADDGA Response to announce its GA capabilities • Sender and Receiver define Tx, Rx Buffer sizes and otherwise prep for GA DELGA Request lets the sender tear down previously established GA capability • Once GA is set up, sender advertises any transmitted frames subject to GA by setting an appropriate flag in the packet MAC Header QOS Control field • Keeps track of all buffer sizes, etc so to not send too many packets, etc • Group ACKable frames are transmitted, separated by SIFS • Done transmitting the burst, Sender issues GroupACK Request Control frame • Receiver immediately responds with a Group ACK or an ACK • The ACK lets him mark time until he’s done preparing a real Group ACK • Needs to process Group ACK Req and correlate with his Rx buffer • Real Group ACK ready, receiver QSTA transmits it as soon as possible • Sender needs to ACK this Group ACK • Sender can then initiate another burst at his convenience

3. D4.0 Group ACK Shortcomings • GA functionality should be available to all stations, not just QSTAs • GAs should be allowed under DCF rules • SIFS Burst packet separation hard requirement is too restrictive • Indicates all GA packets need be queued at the sender • SIFS should be a minimum,goal separation • Don’t use QOS Control field to advertise GA parameters • Replace “Order” bit (B15) in MAC Header Frame Control field with a “No Immediate ACK” bit always set upon a Group ACK transmission • Modify Group ACK Request frame to simplify GA processing • GAReq frame now contains a “Start Sequence Control” field • Receiver and sender need calculate which sequence numbers were actually received from sender, which were actually sent to the receiver and, which, if any need be retransmitted • Much easier for the GAReq to contain the list of seqnos actually sent, and the GA to contain the list of seqnos actually received

4. Proposed Group ACK Modifications • Modified Group ACK is a relatively involved protocol to allow a STA to burst transmissions to another STA while deferring any and all corresponding ACKs until after a later (Group) ACK request. • Upon association, senderSTA gleans from (Association frame) Capabilities Info field that candidate receiver STA is capable of Group ACK • Group ACK is set up, characterized and torn down with Action Frames:Sender transmits ADDGA Request to set up GA with receiver Receiver responds with ADDGA Response to announce its GA capabilities • Sender and Receiver define Tx, Rx Buffer sizes and otherwise prep for GA DELGA Request lets the sender tear down previously established GA capability • Once GA is set up, sender advertises any transmitted frames subject to GA by setting an appropriate flag in the packet MAC Header Frame Control field • Keeps track of all buffer sizes, etc so to not send too many packets, etc • Group ACKable frames are transmitted, separated at a minimum by SIFS • Done transmitting the burst, Sender issues GroupACK Request Control frame • Receiver immediately responds with a Group ACK or an ACK • The ACK lets him mark time until he’s done preparing a real Group ACK • Needs less time to process Group ACK Req, correlate with his Rx buffer • Real Group ACK ready, receiver QSTA transmits it as soon as possible • Sender needs to ACK this Group ACK • Sender can then initiate another burst at his convenience

5. Proposed Group ACK Modifications Summary • The modified GA remains a relatively involved protocol, but now allows non-QoS STAs to burst transmissions to each other. • No longer necessary to queue up packets at the sender prior to issuing a burst • Better supports pseudo-streaming apps like MPEG2 MPTS distribution to multiple SPTS-processing STBs • Reduced complexity sent/received/need-retransmit packet processing • The herein modified Group ACK is a more robust solution • Candidate normative text revisions to 802.11e-D4.0 are contained in document 03/052r0