Multi-TID Ack

July 2016
doc.: IEEE 802.11-16/0961r0
Consideration on Multi-STA BlockAck
Optimization
Date: 2016-07-00
Authors:
Name
Affiliations
Address
Hanseul
Hong
Jinsoo Ahn
Yonsei Univ.
[email protected]
Ronny
Yongho Kim
Woojin Ahn
Korea National
University of
Transportation
WILUS
50, Yonsei-ro, Seodaemun-gu,
Seoul, Korea
50, Yonsei-ro, Seodaemun-gu,
Seoul, Korea
157 Cheoldobakmulgwan-ro,
Uiwang, Gyenggi, Korea
Jiho Lee
Korea Univ.
woojin.ahn@wilusgrou
p.com
[email protected]
Young-Chai
Ko
Youn-Kwan
Kim
Korea Univ.
2nd floor, 48, Mabang-ro,
Seocho-gu, Seoul, Korea
145 Anam-ro, Seungbuk-gu,
Seoul Korea
145 Anam-ro, Seungbuk-gu,
Seoul Korea
43 Jibong-ro Wonmi-gu, Buchunshi, Gyeonggi-do, Korea
Submission
Yonsei Univ.
The Catholic
University of
Korea
Phone
Slide 1
email
[email protected]
[email protected]
[email protected]
[email protected].
kr
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Introduction
• In the spec draft, Block Acknowledgement procedures for UL
MU and some Ack optimization methods are agreed:
– When receiving multiple frames from more than one STA that are part of
an UL MU transmission (Clause 9.42.2) and that require an immediate
acknowledgement, an AP may send multiple BlockAck frames (or ACK
frames) in an OFDMA HE MU PPDU or a Multi-STA BlockAck (M-BA)
frame.
– If the Ack Type field is 0, then the Block Ack Starting Sequence Control
and Block Ack Bitmap subfields are not present and the Per STA Info
subfield indicates the acknowledgment of successful reception of either a
single MPDU or of all the MPDUs carried in the eliciting (A-)MPDU.
– MPDUs with multiple TIDs that ask for Ack and/or BA acknowledgement
and a management frame that asks for Ack acknowledgement may be
aggregated in one A-MPDU of MU transmission.
• However, more effort for Ack optimization is needed
• In this presentation, we discuss further optimization method for
BlockAck is proposed as in CID 2389
Submission
Slide 2
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Problem: BA length exceeds EIFS
• The duration for BA procedures lasts up to milliseconds
• Hidden STAs may send Data frames after EIFS duration,
which makes collision
AP
...
...
Trigger
BA 1
BA 2
UL MU PPDU STA 1
UL MU PPDU STA 2
STA(s)
BA N
UL MU PPDU STA N
EIFS
hidden STA
Submission
Slide 3
ion
Collis
Data
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Recap: Multi-STA BA length selection
• In [2] the length of M-BA with fragmentation is decided
– Depending on Fragment Number subfield value, the length of
BlockAck bitmap varies from 4 octets to 32 octets
Submission
Slide 4
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Recap: Ack/BA mode for Multi-STA BA
• In Draft,
– If the Ack Type field is 0, then the Block Ack Starting Sequence Control and
Block Ack Bitmap subfields are not present and the Per STA Info subfield
indicates the acknowledgment of successful reception of either a single MPDU
or of all the MPDUs carried in the eliciting (A-)MPDU.
Submission
Slide 5
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Recap: Multi-TID BA
• In 11ax, Multi-TID A-MPDU format is allowed[4]
– Multiple TIDs in a single PSDU between AP and a STA for DL/UL
OFDMA/MU-MIMO
– BlockAck setup is done per TID.
• In [5],
– Multi-STA BA supports BA acknowledgement and Ack
acknowledgement for multiple TIDs of a STA
– The spec shall allow UL MU transmission of Multi-STA Block ACK
frame in response to multi-TID A-MPDU of DL MU transmission.
Submission
Slide 6
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Multi-TID Ack (cont.)
• All TID Ack
– The Ack mode for multiple TID can be done with specific TID value
(group TID), when all of A-MPDU for an AID is received successfully
Not repeated by TID
AID
Ack
Type=0
TID
=group TID
11 bit
1 bit
4 bit
– More discussion about TID setting in Multi-TID Ack is discussed in
16/916r0
Submission
Slide 7
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
The Ack duration problem
• The Ack duration extends up to more than 3ms, even
though it assumes 4 octet length in BlockAck bitmap
• Also, using Ack Type field is not enough, because in many
cases, it exceeds EIFS even though all of M-BA has 0 in
Ack Type field
• EIFS excess problem may cause the retransmission of UL
STAs due to corrupted BlockAck.
– Ack protection or further Ack optimization is needed
Submission
Slide 8
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Additional Ack Optimization method
• All STA All Ack
– In case of A-MPDUs from all AIDs are received successfully, AP may
use a specific AID in Multi-STA BlockAck frame to indicate the all
frames from all triggered STAs are successfully received
If all of PPDUs are
received successfully
AP
Trigger
UL MU PPDU STA 1
UL MU PPDU STA 2
M-BA
...
STA(s)
UL MU PPDU STA N
Not repeated by AID
...
Submission
AID=all 1s (2047)
Ack
Type=0
TID
=specified
11 bit
1 bit
4 bit
Slide 9
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Conclusion
• In this presentation, we continued to discuss the Ack
optimization method and some clarification
– There are some methods to reduce the duration of Ack procedure,
including adjusting length of Ack Bitamap, Ack/BA mode, and MultiTID Ack
• However, though all of triggered frame is sent successful,
Ack duration exceeds EIFS even though all of M-BA has 0
in Ack Type field for many user case
• We present the further optimization method, in case all of
triggered STAs’ transmission is successful
– All AID Ack mode with group AID
Submission
Slide 10
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Straw Poll 2
• Do you agree to add to the spec draft?
9.3.1.9.7 Multi-STA BlockAck variant
…
If the Ack Type field is 0, then the Block Ack Starting Sequence Control
and Block Ack Bitmap subfields are not present and the Per STA Info
subfield indicates the acknowledgment of successful reception of either a
single MPDU or of all the MPDUs carried in the eliciting (A-)MPDU.
If the ACK Type field is 0, the AID value of the Per AID TID Info
subfield is set to TBD value (e.g., 2047), and the TID value of the Per AID
TID Info subfield is set to 14, then the Block Ack Starting Sequence
Control and Block Ack Bitmap are not present and the single Per STA Info
field indicates the acknowledgement of successful reception of all the AMPDUs of all the STAs elicited by the trigger frame.
Submission
Slide 11
Hanseul Hong, Yonsei University
July 2016
doc.: IEEE 802.11-16/0961r0
Reference
[1] IEEE P802.11ax D0.2
[2] IEEE 802.11-16/616r2 “BlockAck generation and selection
rules”
[3] IEEE 802.11-15/626r1 “Further consideration for MultiSTA BlockAck frame”
[4] IEEE 802.11-15/1065r1 “UL multi-TIDs aggregation”
[5] IEEE 802.11-16/0069 “Multi-TID A-MPDU in MU
Transmission”
Submission
Slide 12
Hanseul Hong, Yonsei University

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