1. Proposed Modifications to
January 2003
Proposed Modifications to
802.11e-D4.0 Group ACK
Carlos Rios
RiosTek LLC

2. January 2003
D4.0 Group ACK Summary
Group ACK per e-D4.0 is a relatively involved protocol to allow a QSTA to burst transmissions to another QSTA while deferring any and all associated ACKs until after a later (Group) ACK request.
Upon association, sender gleans from (Association frame) Capabilities Info field that candidate receiver 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 QOS Control field
Keeps track of all buffer sizes, etc so to not send too many packets, etc
GA-able frames are burst transmitted, separated by SIFS if within one TXOP
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
Real Group ACK ready, receiver transmits it ASAP (during his own TXOP)
Sender needs to ACK this Group ACK
Sender can then initiate another burst at his convenience

3. Unbundle Group ACK from QoS
January 2003
Unbundle Group ACK from QoS
GA functionality should be available to all stations, not just QSTAs
Group ACKs should be allowed under DCF rules
Don’t use QOS Control field to advertise GA parameters
Replace “Order” bit (B15) in MAC Header Frame Control field with a “GA” bit set upon a Group ACK-able packet transmission
Reclassify ADDGA Request, ADDGA Response and DELGA Request as new category “GA Action Frames”
Remove them from the QOS Action Frame class
As TXOPs don’t apply in DCF, finesse the SIFS interframe spacing issue
Use SIFS to separate GA-able packets whenever possible
If don’t/can’t use SIFS, accept possibility of losing medium access to DCF contender

4. Proposed Group ACK Modifications
January 2003
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, sender gleans from (Association frame) Capabilities Info field that candidate receiver 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
Real Group ACK ready, receiver 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
January 2003
Proposed Group ACK Modifications Summary
The modified GA remains a complicated protocol, but now allows non-QoS STAs to burst transmissions to each other.
Candidate normative text revisions to e-D4.0 are contained in document 03/052r0
“QSTA” replaced by “STA” throughout
Additions, clarifications regarding GA under DCF
FCS “Order” bit replaced by a “No immediate ACK” bit
GA frames moved from the “QoS action” category to a new “GA action” category
Substantial revisions made to section 7, 9.11, and 11.5

6. January 2003
Motion
“Move to instruct the Technical Editor to work with the author and the Group ACK Ad Hoc group to incorporate modifications contained in document 03/52r0 into the successor to e-D4.0”