Embed Size (px)
Citation preview
Yong Liu, MarvellSlide 1
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Max Frame SizesDate: 2010-09-13
Authors:
Name Company Address Phone email Yong Liu Marvell 5488 Marvell Lane, Santa Clara, CA 95054,
USA 1-408-222-8412
Robert Stacey Intel 2111 NE 25th Ave Hillsboro, OR 97124, USA
Simone Merlin Qualcomm 5775 Morehouse Dr., San Diego, CA 92121, USA
Matthew Fischer Broadcom 190 Mathilda Place, Sunnyvale, CA 94086, USA
James Cho Atheros 1700 Technology Drive, San Jose, CA 95110, USA
Youngsoo Kim Samsung Electronics
Mt. 14-1 Nongseo-Ri, Giheung-Eup, Yongin-Si, Gyeonggi-Do, Korea 449-712
Yongho Seok LG Electronics, Inc.
533, Hogye-1dong, Dongan-Gu, Anyang-Shi, Kyungki-Do, 431-749, Korea
82-31-450-1947
Daewon Lee LG Electronics, Inc
533, Hogye-1dong, Dongan-Gu, Anyang-Shi, Kyungki-Do, 431-749, Korea
82-31-450-7897
Minho Cheong ETRI 161 Gajeong-dong, Yuseong-gu, Daejeon, Korea
+82 42 860 5635
Jae Seung Lee ETRI 161 Gajeong-dong, Yuseong-gu, Daejeon, Korea
+82 42 860 1326
Yong Liu, MarvellSlide 2
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Contents
• 802.11n max frame sizes• Larger MPDU/A-MPDU support
– Motivations
– CRC-32 characteristics
– MAC efficiency calculations
• 802.11ac max frame sizes• Conclusions
Yong Liu, MarvellSlide 3
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
802.11n max frame sizes
• Max MSDU: 2,304 B
• Max A-MSDU: 3,839 B or 7,935 B– HT Capabilities element → HT Capabilities Info field → Maximum A-
MSDU Length subfield (0: 3,839 B, 1: 7,935 B)
• Max Frame body of CCMP MPDU:7919 B– 7919 B = 7935 B – 8B MIC – 8B CCMP header
• Max MPDU in A-MPDU: 4,095 B– Limited by 12-bit MPDU Length field in MPDU delimiter
• Max A-MPDU in HT-PPDU: 8,191B ~ 65,535 B– Limited by 16-bit HT Length field in HT-SIG
– HT Capabilities element → A-MPDU Parameters field → Maximum A-MPDU Length Exponent: (213 -1) B ~ (216 -1) B
Yong Liu, MarvellSlide 4
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Larger MPDU/A-MPDU support
• Motivations– Wider bandwidth (80/160MHz) => higher PHY data rate => shorter PHY payload
duration => higher preamble overhead
– The max VHT PPDU/A-MPDU duration is limited by the max number of symbols indicated by L-SIG length, which is 1365 * 4us = 5.46 ms (around 666KB @ 1Gbps, and 1.3MB @ 2Gbps)
– 3 reserved bits remain in MPDU delimiter, which can be used to extend the max MPDU length
A-MPDU subframe 1
RsvdMPDU Length
CRCDelimiter Signature
A-MPDU subframe 2 A-MPDU subframe n
MPDU Pad
12b 0-4KB (limited by MPDU Length)
1 – 64 A-MPDU subframes (MPDU length > 0)
EOF
1b 3b
Yong Liu, MarvellSlide 5
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
CRC-32 error checking characteristics
• The error checking mechanism of CRC-32 was characterized by R. Jain, "Error Characteristics of Fiber Distributed Data Interface (FDDI)," IEEE Transactions on Communications, Vol. 38, No. 8, August 1990, pp. 1244-1252
• FDDI, Ethernet, and 802.11 use the same CRC-32 error checking mechanism
• The probability of undetected errors remains constant for frame sizes between 3007 and 91639 bits
– 91639b = 91607b data + 32b CRC
RsvdMPDU Length
CRCDelimiter Signature
MPDU Pad
12b < 91639b
EOF
1b 3b
FCS
Yong Liu, MarvellSlide 6
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
MAC Efficiency Calculations (1)
• Parameters– AIFS: 34us
– Average CW: 67.5us
– MSDU: 1500B
– Max MPDU (~ Max A-MSDU)• 1540B (w/o A-MSDU)• 4095B (w/ A-MSDU) • 8197B (w/ A-MSDU)• 12287B (w/ A-MSDU)• 16383B (w/ A-MSDU)
– Max BA window: 32
– BA: legacy rate
– TXOP duration: 3ms• TXOP truncation enabled
– Note: actual A-MSDU/MPDU and A-MPDU sizes depend on TXOP duration and residual TXOP duration
Yong Liu, MarvellSlide 7
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
MAC Efficiency Calculations (2)
80MHz 4 streams
60.00%
65.00%
70.00%
75.00%
80.00%
85.00%
90.00%
95.00%
MCS (low => high)
MA
C u
tili
zati
on
1500 4095 8191 12287 16383
Yong Liu, MarvellSlide 8
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
MAC Efficiency Calculations (3)
80MHz 8 streams
50.00%
55.00%
60.00%
65.00%
70.00%
75.00%
80.00%
85.00%
90.00%
95.00%
MCS (low => high)
MA
C u
tili
zati
on
1500 4095 8191 12287 16383
Yong Liu, MarvellSlide 9
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
MAC Efficiency Calculations (4)
160MHz 4 streams
50.00%
55.00%
60.00%
65.00%
70.00%
75.00%
80.00%
85.00%
90.00%
95.00%
MCS (low => high)
MA
C u
tili
zati
on
1500 4095 8191 12287 16383
Yong Liu, MarvellSlide 10
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
MAC Efficiency Calculations (5)
160MHz 8 streams
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
MCS (low => high)
MA
C u
tili
zati
on
1500 4095 8191 12287 16383
Yong Liu, MarvellSlide 11
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Max MPDU size
• Max MPDU size is increased to 11454B– 11454B = 11450B (~91607b) + 4B FCS
– Maintain the same CRC-32 error checking characteristics
– Improve MAC efficiency for very high data rate
• MPDU Length in delimiter is extended to 14 bits
RMPDU Length
CRCDelimiter Signature
MPDU Pad
12b 0-11454B
EOF
1b 1b
Len Ex
2b
FCS
14b
Yong Liu, MarvellSlide 12
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Max A-MSDU and A-MPDU sizes
• Max A-MSDU– Max A-MSDU = Max MPDU – Max MAC header – FCS
– Extend Maximum A-MSDU Length subfield by 1 bit (0: 3,839 B, 1: 7,935 B, 2: {11454 B – Max MAC header – FCS}, 3: reserved)
– Max Frame body of CCMP MPDU = Max A-MSDU – 8B MIC – 8B CCMP header
• Max A-MPDU – If the max BA window is maintained to 64, the max A-MPDU can be up
to 733,056B
– Extend Maximum A-MPDU Length Exponent subfield by 1 bit: 0-7 => (213 -1) B (=8191B) ~ (213+7 -1) B (=1MB -1)
Yong Liu, MarvellSlide 13
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Conclusions
• Propose to extend max MPDU, max A-MSDU, and max A-MPDU sizes to improve MAC efficiency
• Define max MPDU, max A-MSDU, and max A-MPDU sizes for 11ac
• Extend the 802.11n max frame size negotiation/signaling to support new max frame sizes
Yong Liu, MarvellSlide 14
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Reference
• 11-10-yyyy-00-00ac-a-mpdu-delimiter-changes.ppt
Yong Liu, MarvellSlide 15
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Straw Poll 1
• Should the spec framework document be updated to include the following limits:– Max MPDU = 11454B
– Max A-MSDU = 11454B – Max MAC Header - FCS
– Max A-MPDU = 1MB
– Yes:
– No:
– Abstain:
Yong Liu, MarvellSlide 16
doc.:IEEE 802.11-10/1079r0
Submission
Sept. 13, 2010
Straw Poll 2
• Should the spec framework document be updated to include the following capability signaling:– Max A-MPDU length supported as exponent n where 0 <= n <=7
and indicates a max A-MPDU length (2^(13+n)-1)B
– Max A-MSDU length supported as 3839B, 7935B or {11454B-Max MAC Header-FCS}
– Yes:
– No:
– Abstain:
