March 2 005 Syed Aon M ujtab Slide 1 doc.: IEEE 802.11-04/888r9 Submission TGn Sync Complete Proposal Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures < http:// ieee802.org/guides/bylaws/ sb -bylaws. pdf >, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart . kerry @ philips .com > as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If Date: 2005-03-04 Author Name Company Address Phone Email Syed Aon Mujtaba Agere Systems 555 Union Blvd., Allentown, PA 18109, USA +1 610 712 6616 mujtaba@agere. com
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March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 1
doc.: IEEE 802.11-04/888r9
Submission
TGn Sync Complete Proposal
Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11.
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair < [email protected]> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <[email protected]>.
PHY Summary of TGn Sync Proposal Mandatory Features:
■ 1 or 2 Spatial Streams■ 20MHz Channelization■ 1/2, 2/3, 3/4, and 5/6 channel coding rates■ RX assisted Rate Control■ 400ns & 800ns Guard Interval■ Full & seamless interoperability with a/b/g
Optional Features:■ 40MHz channelization■ Transmit Beamforming■ Low Density Parity Check (LDPC) Coding ■ support for 3 or 4 spatial streams
*Not required in regulatory domains where prohibited.
144 Mbps in 20MHz
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 11
doc.: IEEE 802.11-04/888r9
Submission
MAC Summary of TGn Sync Proposal Mandatory Features:
■ MAC level aggregation■ RX assisted link adaptation■ QoS support (802.11e)■ Block ACK compression■ Legacy compatible protection■ 20/40 MHz channel management
Optional Features:■ Bi-directional data flow■ MIMO RX Power management
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 12
doc.: IEEE 802.11-04/888r9
Submission
PHY
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 13
doc.: IEEE 802.11-04/888r9
Submission
PHY Architectural Features Mandatory features:
■ Spatial division multiplexing (SDM) of 2 Spatial Streams■ Interoperable 20MHz and 40MHz channelizations■ Channel Coding Rates: 1/2, 2/3, 3/4, and 5/6■ Support for RX assisted Rate Control■ Guard Interval: 400ns and 800ns
Optional robustness & throughput enhancement:■ 40 MHz channelizations■ Transmit beamforming■ Advanced coding (LDPC)■ SDM with 3 or 4 spatial streams
Max Mandatory rate in 20MHz = 144 Mbps(with 2x2 architecture using 2 spatial streams)
with the option to scale to 600Mbps
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 14
doc.: IEEE 802.11-04/888r9
Submission
PHY Modifications after Monterey (Jan ‘05) 40MHz operation made optional
■ previously it was mandatory Expanded data tones from 48 to 52 in 20MHz
■ total is 56 tones now■ Number of Pilots stay at 4
Dropped highest coding rate to 5/6■ previously it was 7/8
Reduced the HT-LENGTH field indicator from 19 bits to 12 bits Adopted a format for sounding packets
■ sounding packets are those in which NSS NTX■ sounding packets enable complete antenna-to-antenna channel estimation
Removed option for unequal power loading in TX Beamforming Introduced a new extended MCS set for TX Beamforming
■ constant code rate with variable modulation levels
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 15
doc.: IEEE 802.11-04/888r9
Submission
Scalable PHY Architecture
Open Loop SDM
RX assisted Rate Control
2 Spatial Streams
20 MHz
144 Mbps
Robustness Enhancement
Closed Loop TX BF
4 Spatial Streams
ThroughputEnhancement
Conv. Coding LDPC
Robustness Enhancement
600 Mbps
Mandatory Optional
40 MHz
ThroughputEnhancement
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 16
doc.: IEEE 802.11-04/888r9
Submission
Mapping Spatial Streams to Multiple Antennas Number of spatial streams = Number of TX antennas
■ Direct map 1 spatial stream to 1 antenna■ Spatial division multiplexing■ Equal rates on all spatial streams
Number of spatial streams ≤ Number of TX antennas■ Each spatial stream mapped to all transmit antennas■ Optional transmit beamforming
• Optimal technique for realizing array and diversity gains• Requires channel state info at the TX• Supports unequal rates on different spatial streams
■ Optional orthogonal spatial spreading• Exploits all transmit antennas• No channel state info at TX required
■ Due to per spatial stream training, no change is needed at the RX to support optional techniques
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 17
doc.: IEEE 802.11-04/888r9
Submission
Parameters in Link Adaptation
Basic MIMO Beamformed MIMO
Stream Control Yes YesRate (MCS) Control Yes Yes (per
stream)GI selection Yes YesTX Per-Tone Steering Matrix No YesPer Stream Power Loading No No NEW
• 52 data tones (2 extra on each side)• 4 pilot tones
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 21
doc.: IEEE 802.11-04/888r9
Submission
½ GI applies to all data rates in 20MHz
Mandatory MCS Set
Modulation Code RateData Rates 20 MHz (Mbps)
1 Spatial Stream 2 Spatial Streams
BPSK 1/2 7.22 14.44
QPSK 1/2 14.44 28.88
QPSK 3/4 21.67 43.34
16 QAM 1/2 28.89 57.78
16 QAM 3/4 43.33 86.66
64 QAM 2/3 57.78 115.56
64 QAM 3/4 65 130
64 QAM 5/6 72.22 144.44
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 22
doc.: IEEE 802.11-04/888r9
Submission
HT-PPDU Format in 20MHz20
MH
z
AN
T_1
LegendL- Legacy HT- High ThroughputSTF Short Training FieldLTF Long Training FieldSIG Signal Field
Legacy CompatibleCan be decoded by anylegacy 802.11a or g compliant device for interoperability
L-STF L-LTF L-SIG HT-SIG HT-DATA
L-STF L-LTF L-SIG HT-SIG HT-DATA
Legacy Compatible Preamble HT-specific Preamble
HTSTF
HTLTF-1
HTLTF-2
20M
Hz
AN
T_2
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 23
doc.: IEEE 802.11-04/888r9
Submission
Spoofing
Spoofing is the use of the legacy RATE and LENGTH fields to keep the legacy STA off the air for a desired period of time
The duration indicated in the L-SIG can exceed the actual duration in the HT-SIG MAC uses this as a protection mechanism
For a HT-PPDU, L-SIG RATE is hard-coded at 6 Mbps■ max MSDU length = 2304 Bytes spoofing duration up to ~3 msec
L-STF L-LTF L-SIG HT-SIG HT LTF HT LTF Data
Legacy RATE and LENGTH fields => Packet Length in OFDM Symbols
HTSTF
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 24
doc.: IEEE 802.11-04/888r9
Submission
HT PPDU Detection
Auto-detection scheme on HT-SIG■ Q-BPSK modulation (BPSK w/ 90-deg rotation)■ Invert the polarity of the pilot tones■ Combined methods provide speed and reliability
L-STF L-LTF L-SIG HT-SIG
L-STF L-LTF L-SIG
orLegacyDATA
Legacy Compatible Preamble
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 25
doc.: IEEE 802.11-04/888r9
Submission
MIMO AGC
Tone interleaving the L-STF leads to perfect decorrelation■ if L-STF is tone-interleaved, it will hurt legacy interoperability with cross-correlation RX
Cyclic delay across the L-STF is nearly decorrelated■ however, large cyclic delay hurts interoperability with cross-correlation RX■ and, small cyclic delay suffers from inaccurate power estimation, as shown next
L-STF L-LTF L-SIG HT-SIG HT-DATA
single spatial stream multiple spatial streams
powermeasurement
AGC locked
*
1
_ _TXN
j ji jii
Power RX Power TX h h
Accurate measurement of MIMO channel power
requires uncorrelated STFs
*( ) ( ) 0i jE STF f STF f
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 26
doc.: IEEE 802.11-04/888r9
Submission
Power Fluctuation of L-STF w.r.t Data
-7 -6 -5 -4 -3 -2 -1 0 1 2 30
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
x = Power fluctuation of AGC setting w.r.t. data power (dB)
STF = Tone InterleavedSTF = Cyclic Delay
CD
F(x)
Power fluctuation with tone interleaving is within 1dB of the data power
Data power
Introduce a dedicated STF for MIMO that is tone interleaved
Reduces 1 bit in the ADC cost & power savings
2x2, TGn Channel DSNR = 30dB
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 27
doc.: IEEE 802.11-04/888r9
Submission
Power Fluctuation of HT-LTF w.r.t. Data
-10 -8 -6 -4 -2 0 2 40
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
x = Power fluctuation of HT-LTF w.r.t. data (dB)
CD
F(x)
HT-LTF = Tone Interleaved
HT-LTF = Walsh + Cyclic Delay
2x2, TGn Channel DSNR = 30dB
Data power
Large deviation of HT-LTF power wrt data power will result in higher channel estimation error
HT-LTF should be tone interleaved
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 28
doc.: IEEE 802.11-04/888r9
Submission
Tone Interleaved HT Training Fields
HT-STF■ 2nd AGC measurement is used to fine-tune MIMO reception
HT-LTF■ Used for MIMO channel estimation■ Additional frequency or time alignment
HT SIG 2 LTS1 LTS2 DATA
DATA
DATA
HT LTF
HT SIG 2
HT SIG 2
HTSTS
HTSTS
HTSTS
LTS1 LTS2
LTS1 LTS2
LTS1 LTS2
LTS1 LTS2
LTS1 LTS2
HT LTFHTSTF
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 29
doc.: IEEE 802.11-04/888r9
Submission
Spatial Stream Tone Interleaving1 SpatialStream
2 SpatialStreams
3 SpatialStreams
4 SpatialStreams
• Color indicates spatial stream• Each HT-LTF has equal representation from all spatial streams
• Eliminates avg. power fluctuation across LTFs• HT-LTS symbols are designed to minimize PAPR
• Distinct symbol designs for different number of spatial streams
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 30
doc.: IEEE 802.11-04/888r9
Submission
Summary of HT-LTF Robust design
■ Tone interleaving reduces power fluctuation■ 2 symbols per field
• 3dB of channel estimation gain with baseline per-tone estimation• Enables additional frequency offset estimation
Per spatial stream training■ HT-LTF and HT-Data undergo same spatial transformation■ Number of HT-LTFs = Number of spatial streams
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 31
doc.: IEEE 802.11-04/888r9
Submission
Preamble Format Comparison
L-STF L-LTF L-SIG
L-STF(400ns) L-LTF(3100ns) L-SIG(3100ns)
Tx1
Tx2
L-STF
.11a preambleL-LTF L-SIGTx1
WWiSE preamble (2TX Mixed-mode)
L-STF L-LTF L-SIG
L-STF(50ns) L-LTF(50ns) L-SIG(50ns)
Tx1
Tx2
TGn Sync preamble (2TX)
Values shown in brackets indicate the amount of CDD delay
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 32
doc.: IEEE 802.11-04/888r9
Submission
Legacy Interoperability of PreambleCross Correlation with STS
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
microseconds
Abs
olut
e Va
lue
of C
ross
Cor
rela
tion
Cross Correlation with STS
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5
microseconds
Abs
olut
e Va
lue
of C
ross
Cor
rela
tion
Cross-correlation of L-STS (TGn Sync)
Cross-correlation of L-STS (WWiSE)
Period = 800ns
Period = 400ns
Potential issues with cross-correlation receivers with WWiSE preamble
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 33
doc.: IEEE 802.11-04/888r9
Submission
Test Setup
Rx1Packet
generatorTGn
Channel model
Tx1
Tx2
C simulator Agilent E4438C
Single inputsingle output
signal generatorNormalized
Test packets generated in C simulator TX signals are convolved with a simulated TGn
channel Signal generator is used for up-conversion
Implication of using WWiSE preambles Legacy devices with a cross-correlation RX will not
correctly decode a WWiSE preamble Hence, such legacy devices will not defer to a
WWiSE HT transmission, potentially creating collisions in the BSS
■ BSS throughput would drop, and latency would increase WWiSE preamble is not legacy compatible Lab test reinforces TGn Sync’s decision to use a
100% backwards compatible legacy preamble
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 38
doc.: IEEE 802.11-04/888r9
Submission
TGn Sync enhanced interleaver11a Bit interleaver,
PermutationOperation 1
parser
FrequencyRotation
SISO (11a/g)
MIMO 2x11a Bit interleaver,
PermutationOperation 1
11a Bit interleaver,PermutationOperation 2
11a Bit interleaver,PermutationOperation 2
11a Bit interleaver,PermutationOperation 1
11a Bit interleaver,PermutationOperation 2
Channelization 20MHz 40MHz
Total # of Streams 1 2 3 4 1 2 3 4
1st stream 0 0 0 0 0 0 0 0
2nd stream 22 22 22 58 58 58
3rd stream 11 11 29 29
Freq
uenc
y R
otat
ion
4th stream 33 87
1st Spatial Stream
2nd, 3rd, or 4th Spatial Stream
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 39
doc.: IEEE 802.11-04/888r9
Submission
2 vs 4 pilots in MIMO■ The TGn Sync Proposal uses the full 4 pilots (like .11a/b/g)
• 2 pilots in WWiSE provide marginal data rate increase: < 4%■ Full CC67 sims to compare multi- and single-stream cases:
• Since data also will have diversity gain, and thus require less operating SNR, would the pilots now limit performance?
• Single stream modes important: CDD (TGn Sync) , STBC (WWiSE)■ Analysis must consider differences in 11n vs. 11a:
• Different preambles, antenna configurations• Decoded data SNR improved due to MIMO (e.g, MRC, STBC)• Thus pilot accuracy requirements also increase• Comparing 11n pilot SNR to 11a is thus not sufficient
■ Robustness to narrowband interference and impairments• These both reduce effective number of pilots – thus need margin
■ Full details in doc. 11-05/1636r0
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 40
doc.: IEEE 802.11-04/888r9
Submission
Dual Stream Performance2 vs 4 Pilots with 2 streams, 2x2, E NLOS
1.E-03
1.E-02
1.E-01
1.E+00
5 10 15 20Average SNR [dB]
Pac
ket E
rror
Rat
e
2 streams, BPSK, 1/2, 2 pilots
2 streams, BPSK, 1/2, 4 pilots
1 dB
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 41
doc.: IEEE 802.11-04/888r9
Submission
Single Stream Performance2 vs 4 Pilots with single stream, 2x2, E NLOS
1.E-03
1.E-02
1.E-01
1.E+00
5 10 15 20Average SNR [dB]
Pac
ket E
rror
Rat
e
1 stream, BPSK, 1/2, 2 pilots
1 stream, BPSK, 1/2, 4 pilots
3.5 dB
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 42
doc.: IEEE 802.11-04/888r9
Submission
Summary of 2 vs 4 pilots Quantitative analyses show that using only 2 pilots
causes significant performance degradation in many situations
■ 4 vs 2 pilots compared for 2x2 basic MIMO channel E• Dual stream: ~1dB loss• Single stream: 1.5~3.5dB loss.
■ Robustness• Performance loss w/ narrow-band interference or impairments:
– 4 ~ 6dB loss with 2 pilots -> NOT ROBUST !!
Performance penalty of using only 2 pilots is not justified by the less than 4% data rate increase
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 43
doc.: IEEE 802.11-04/888r9
Submission
Importance of Rate Feedback and Stream Control
Throughput is maximized if there is rapid convergence to a good choice of stream count and MCS
■ Initial MCS/stream selection ■ Ongoing tracking and optimization
Receiver determines its preferred stream count and MCS■ Based on observation of received HT-LTF in sounding packet■ Sends this choice back to transmitter using MCS Feedback (MFB)
Transmitter makes a rate choice based on the MCS selection at RX
■ Under some circumstances, e.g. pairwise spoofing, TX must adhere to MFB
Important for Basic MIMO, Spatial Spreading and Beamforming
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 44
doc.: IEEE 802.11-04/888r9
Submission
Rate feedback in Basic MIMO MRQ (MCS Request) is sent in sounding packet:
■ RX gets estimate of full H matrix■ Channel quality estimates based on H matrix guide rate and
stream selection
TX RX
MRQ payload in PHY sounding packet
Full H matrix
Number of streams and coding rate carried in MFB
h11Ant1
Ant2
h12
h21
h22
2
1
2212
2111
hh
hhhh
H
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 45
doc.: IEEE 802.11-04/888r9
Submission
Stream/Rate Control Approaches SNR calculation performed at equalizer
output:■ Can provide stream count and MCS selection■ Includes impairments due to channel estimation
errors SNR calculation performed by re-encoding
decoded data and comparing it against decoder input:■ allows MCS selection, but not stream count
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 46
doc.: IEEE 802.11-04/888r9
Submission
Close Loop vs Open Loop Throughput Comparison■ Open loop vs closed loop comparison for 2x2■ TxBf = Transmit Beamforming; SS=Spatial spreading
Open vs. Closed loop
0
20
40
60
80
100
120
140
160
180
200
10 15 20 25 30 35 40 45 50
SNR [dB]
MA
C th
roug
hput
[Mbp
s]
TxBf 2%SS closed loop 2%SS open loop 2%TxBf 10%SS closed loop 10%SS open loop 10%
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 47
doc.: IEEE 802.11-04/888r9
Submission
MSDU Delay CDFTarget PHY PER = 10%
SS open loop 10% PER
SS closed loop 10% PER
TxBf closed loop 10% PER
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 48
doc.: IEEE 802.11-04/888r9
Submission
Optional PHY Features
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 49
doc.: IEEE 802.11-04/888r9
Submission
Tone Format in 40MHz
-58 -6 +6 +58-64 +63
-53 -25 -11 +11 +25 +53
-2 +2-32 +32
Legacy 20 MHz inLower Sub-Channel
Legacy 20 MHz inUpper Sub-Channel
40 MHz:• 128 point FFT• 108 data tones• 6 pilot tones
20/40 MHz Interoperability 40 MHz PPDU into a 40 MHz receiver
■ Get 3dB processing gain – duplicate format allows combining the legacy compatible preamble and the HT-SIG in an MRC fashion
20 MHz PPDU into a 40 MHz receiver■ The active 20 MHz sub-channel is detected as the 20 MHz sub-channel with
higher energy, cross-correlation or autocorrelation, etc.
40 MHz PPDU into a 20 MHz receiver■ One 20 MHz sub-channel is sufficient to decode the L-SIG and the HT-SIG■ 20 MHz RX (either HT or legacy) will defer properly to 40 MHz PPDU
See MAC slides for additional information on 20/40 inter-op
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 53
doc.: IEEE 802.11-04/888r9
Submission
Benefit of 40MHz channelization
0
20
40
60
80
100
120
140
160
180
200
220
240
260
0 5 10 15 20 25 30 35
SNR (dB)
Ove
r the
Air
Thro
ughp
ut (M
bps)
2x2-40 MHz
4x4-20 MHz
2x2-20 MHz w/ short GI
2x3-20 MHz w/ short GI
2x2 – 40 MHz• Only 2 RF chains => Cost effective & low power• Lower SNR at same throughput => Enhanced robustness
Basic MIMO MCS setNo impairments1000 byte packetsTGn channel model B
Sweet spot for 100Mbps top-of-MAC
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 54
doc.: IEEE 802.11-04/888r9
Submission
Seamless Arch Extension for TX BFe.g. 2 Spatial Streams across 3 Transmit Antennas
Cha
nnel
Enc
oder
Pun
ctur
er
FrequencyInterleaver
ConstellationMapper
Pilots
HT LTF
Scr
ambl
edM
PD
U
FrequencyInterleaver
ConstellationMapper
Pilots
Spat
ial S
teer
ing
Mat
rix
Per Spatial Stream Processing:HT-LTF & HT-Data undergo same spatial transformation iFFT
Mod.insert
GI win
dow
iFFTMod.
insertGI
iFFTMod.
insertGI
win
dow
win
dow
Spa
tial P
arse
r
HT LTF
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 55
doc.: IEEE 802.11-04/888r9
Submission
0
20
40
60
80
100
120
140
160
0 5 10 15 20 25 30 35
SNR (dB)
Ove
r-th
e-A
ir Th
roug
hput
(Mbp
s)
2x2 - SDM
2x3 - SDM
2x2 - Advanced BF
3x2 - Advanced BF
4x2 - Advanced BF
Why introduce TX Beamforming?
1000 byte packetsNo impairment20MHz, channel D
4 TX-antenna AP 2 RX-antenna client ~10 dB gain of 4x2-ABF over 2x2-SDM => cost effective client
■ Added• Precise TSF Synchronization support• Max PSDU Length Capability
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 65
doc.: IEEE 802.11-04/888r9
Submission
Baseline MAC Features
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 66
doc.: IEEE 802.11-04/888r9
Submission
A-MPDU Aggregation StructureM
PD
UH
eade
r
Leng
thC
RC
MP
DU
Pay
load
FC
S
MP
DU
Hea
der
Leng
thC
RC
MP
DU
Pay
load
FC
S
MP
DU
Hea
der
Leng
thC
RC
MP
DU
Pay
load
FC
S
MP
DU
Del
imite
r
MP
DU
PSDU
Robust Structure Aggregation is a purely-MAC function
■ PHY has no knowledge of MPDU boundaries■ Simplest MAC-PHY interface
Control and data MPDUs can be aggregated
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 67
doc.: IEEE 802.11-04/888r9
Submission
A-MSDU Aggregation Structure
FrameControl Dur / ID Address
1Address
2Address
3Seq
ControlQoS
ControlAddress
4A-
MSDU FCS
Subframe 1 Subframe 2 Subframe n...
SubframeHeader MSDU Pad
DA SA Len
0-2304 B 0-3 B14 B
6B 6B 2B
Carrier MPDU
•Efficient Structure
•MSDUs of the same TID can be aggregated
•MSDUs with differing SA/DA can be aggregated
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 68
doc.: IEEE 802.11-04/888r9
Submission
A-MPDU Aggregate Exchange Sequences
A-MPDU Aggregate exchange sequences include single frames or groups of frames that are exchanged “at the same time”
■ Allows effective use of Aggregate Feature■ Allows control and data to be sent in the same PPDU
An initiator sends a PPDU and a responder may transmit a response PPDU
■ Either PPDU can be an aggregate
(“Initiator” / “responder” are new terms relating to roles in aggregate exchange protocol)
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 69
doc.: IEEE 802.11-04/888r9
Submission
Dat
a M
PDU
Agg
PPD
UD
ata
MPD
U
Dat
a M
PDU
Initi
ator
Tx
Activ
ityPH
Y Tx
MAC
Tx
Res
pond
er T
x Ac
tivity
PHY
TxM
AC T
x
Non
-agg
PPD
UBl
ock
Ack
Basi
c ra
teno
n-ag
gR
TS
Basi
c ra
teno
n-ag
gC
TS
Dat
a M
PDU
Agg
PPD
UD
ata
MPD
U
Dat
a M
PDU
Non
-agg
PPD
UBl
ock
Ack
Dat
a M
PDU
Dat
a M
PDU
Dat
a M
PDU
Dat
a M
PDU
Dat
a M
PDU
Dat
a M
PDU
Implicit BlockAck Protocol
RTS/CTSProtocol
Dat
a M
PDU
Dat
a M
PDU
Basic Aggregate Exchange
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 70
doc.: IEEE 802.11-04/888r9
Submission
RX Assisted Link Adaptation Protocol Support for PHY closed-loop modes with on-the-air
signalling Request for training and feedback are carried in
control frames Rate feedback supported Transmit beamforming training supported
■ sounding packet■ calibration exchange
Timing of response is not constrained permitting a wide range of implementation options
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 71
doc.: IEEE 802.11-04/888r9
Submission
RX Assisted Link Adaptation Protocol
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 72
doc.: IEEE 802.11-04/888r9
Submission
Features Providing Additional Efficiency
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 73
doc.: IEEE 802.11-04/888r9
Submission
Reverse Direction Data Flow Gives an opportunity for a responder to
transmit data to an initiator during the initiator’s TXOP
Aggregates data with response control MPDUs
Reduces Contention Effective in increasing TCP/IP performance
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 74
doc.: IEEE 802.11-04/888r9
Submission
Agg
PP
DU
Initi
ator
Tx
Act
ivity
PH
Y T
xM
AC
Tx
Res
pond
er T
x A
ctiv
ityP
HY
Tx
MA
C T
x
Bas
ic ra
teno
n-ag
gIA
C M
PD
U(R
TS+
RD
L)
Bas
ic ra
teno
n-ag
gR
AC
MP
DU
(CTS
+RD
R)
Dat
a M
PD
U
Agg
PP
DU
Dat
a M
PD
U
BA
MP
DU
Agg
PP
DU
Blo
ck A
ck
Dat
a M
PD
UD
ata
MP
DU
Dat
a M
PD
U
RA
C M
PD
U
IAC
MP
DU
(RD
G)
Reverse DirectionProtocol
BA
R M
PD
U
Dat
a M
PD
UD
ata
MP
DU
IAC
MP
DU
RD
GD
urat
ion
Dat
a M
PD
U
Dat
a M
PD
U
Reverse Direction Protocol
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 75
doc.: IEEE 802.11-04/888r9
Submission
Enhanced BA Mechanism
Aggregation frameM
D D1 D2 D3 D4Initiator
ResponderCompressed
BA
SIFS
The originator may omit the inclusion of a BAR frame in an aggregated frame (Implicit BAR). Defines a compressed variant of the 802.11e BA MPDU (Compressed BA).
■ Support for non-fragmented BA. This reduces the bitmap size to 1 bit per MSDU.■ Truncation of the bitmap to reduce the number of MSDUs acknowledged in the bitmap.
Compressed Non-Frag Num MSDU TID
1 – 128 Frame
ControlDuration/
ID RA TA BA Control
BA Starting Seq. Control BlockAckBitmap FCS
BA Bitmap size is fixed through BA setup.
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 76
doc.: IEEE 802.11-04/888r9
Submission
Multiple Receiver Aggregation Aggregates can contain MPDUs addressed
for multiple receiver addresses (MRA) MRA may be followed by multiple
responses from the multiple receivers MRA is effective in improving throughput
in applications where frames are buffered to many receiver addresses
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 77
doc.: IEEE 802.11-04/888r9
Submission
Multiple ResponsesIAC:
OffsetDuration
IAC:Offset
Duration
IAC:Offset
Duration
Initiator’s PPDU
Response from RA2
Response from RA 3
Duration 1
Duration 3
Offset 1
Duration 2E
nd o
f PP
DU Offset 2
Offset 3
Response from RA1
MRA contains multiple IAC for ■ One per response■ At most one per receiver
IAC specifies response offset and duration
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 78
doc.: IEEE 802.11-04/888r9
Submission
Legacy Interoperability and Channel Management
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 79
doc.: IEEE 802.11-04/888r9
Submission
Protection Mechanisms LongNAV
■ An entire sequence is protected by NAV set using MPDU duration field or during contention-free period
■ CF-end packet at end of EDCA TXOP sequence may be used to return unused time by resetting NAV
Pairwise Spoofing■ Protection of pairs of PPDUs sent between an initiator and a
single responder■ Uses Legacy PLCP header duration spoofing
Single-ended Spoofing■ Protection of aggregate and any responses using legacy PLCP
spoofing at the initiator only■ Can be used to protect multiple responses
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 80
doc.: IEEE 802.11-04/888r9
Submission
LongNAV protection Provides protection of a sequence of multiple PPDUs Provides a solution for .11b Comes “for free” with polled TXOP Gives maximum freedom in use of TXOP by initiator
RAC(CTS)
IAC(RTS) Agg
Agg
Agg
Agg
CF-End
NAV Value
NAV Value
Nom
inal
End
of T
XO
P
Nav Timer Non-Zero
Resetsthe
NAV
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 81
doc.: IEEE 802.11-04/888r9
Submission
Pairwise Spoofing Protection Protects pairs of PPDUs (current and following) Very low overhead, suitable for short exchanges, relies on robust
PHY signaling Places Legacy devices into receiving mode for spoofed duration Spoofing is interpreted by HT devices as a NAV setting
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 82
doc.: IEEE 802.11-04/888r9
Submission
Single-Ended Spoofing Protection Protects MRA and all responses Very low overhead, suitable for short exchanges Places legacy devices into receiving mode for spoofed duration Same level of protection as initiator CTS-to-Self
■ Assuming CTS is sent at the lowest rate
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 83
doc.: IEEE 802.11-04/888r9
Submission
Operating Mode Selection BSS operating mode controls the use of protection
mechanisms and 20/40 width switching by HT STA■ Supports mixed BSS of legacy + HT devices
HT AP-managed modes■ If only the control channel is overlapped, managed mixed
mode provides a low overhead alternative to mixed mode■ If both channels are overlapped, 20 MHz base mode allows an
HT AP to dynamically switch channel width for 40 MHz-capable HT STA
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 84
doc.: IEEE 802.11-04/888r9
Submission
20 MHz-base Managed Mixed Mode
ch_a (control)
CTSself/Bcn
CF-End
tch_b (extension)
Bcn/ICB
CF-End
CF-End
tRCB
NAV
NAV
NAVNAV
NAVch_a
NAVch_b
NAVch_a+ch_b
20MHz
40MHz20MHz
CarrierSense(CS)
CS
CS
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 85
doc.: IEEE 802.11-04/888r9
Submission
System Simulation Results Compliant to TGn FRCC requirements 3 independent MAC simulations
■ 802.11-04/893■ 802.11-04/894■ 802.11-04/1359
FRCC Results and analysis of MAC features is presented in 802.11-04/892
Detailed description of MAC simulation methodology in 802.11-04/895
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 86
doc.: IEEE 802.11-04/888r9
Submission
Selected System CC PerformanceCC# Name Result
HCCA EDCA2x2x20 2x2x40 2x2x20 2x2x40
CC3 List of goodput results for usage models 1, 4 and 6.
Key Features Scalable PHY & MAC Architecture 20 and 40 MHz channels – fully interoperable Data rate scalable to 600 Mbps Legacy interoperability – all modes Robust preamble Transmit beamforming Robust frame aggregation Bi-directional data flow Fast link adaptation
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 93
doc.: IEEE 802.11-04/888r9
Submission
GlossaryCRC Cyclic Redundancy Check MPDU MAC protocol data unit
BA Block Ack MRQ MCS requestBAR Block Ack Request MSDU MAC service data unitBSS Basic service set NAV Network allocation vectorCHDATA Compressed header data Non-Agg Non-AggregateCTS Clear to send PPDU PHY protocol data unitFCS Frame checksum QoS Quality of Service
HCCAHybrid controlled channel access RAC Responder aggregate control
IAC Initiator aggregate control RDG Reverse direction grantMAC Medium access controller RDL Reverse direction limitMCS Modulation and coding RDR Reverse direction requestMFB MCS feedback RTS Ready to sendMHDR MAC header MPDU TXOP Transmit opportunity
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 94
doc.: IEEE 802.11-04/888r9
Submission
MAC Backup
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 95
doc.: IEEE 802.11-04/888r9
Submission
MAC Challenges in HT Environment HT requires an improvement in MAC Efficiency HT requires effective Rate Adaptation HT requires Legacy Protection
0%
10%
20%
30%
40%
50%
60%
70%
80%
0 5 10 15 20 25
Packet Size (KB)
MAC
Effi
cien
cy
Basic Rate 54 Mbps
Basic Rate 6 Mbps
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 96
doc.: IEEE 802.11-04/888r9
Submission
Periodic Multi-Receiver Aggregation
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 97
doc.: IEEE 802.11-04/888r9
Submission
Following Packet Descriptor (FPD) Protocol
Agg
PPD
U
Initi
ator
Tx
Activ
ityPH
Y Tx
MAC
Tx
Res
pond
er T
x Ac
tivity
PHY
TxM
AC T
x
Dat
a M
PDU
FPDProtocol
Spoofed PLCP Length
Spoofed Length
Note, duration value ofEIFS-DIFS which is NOTincluded in the spoofed
PLCP LengthIAC
MPD
U(F
PD:L
engt
h)
Dat
a M
PDU
Dat
a M
PDU
Agg
PPD
UBl
ock
ACK
RAC
MPD
U(M
FB:R
ate)
Agg
PPD
U
IAC
MPD
U
Spoofed
Dat
a M
PDU
Dat
a M
PDU
Non
-Agg
PPD
UBl
ock
ACK
Non
-Agg
PPD
UIA
C M
PDU
(FPD
:Len
gth)
Non
-Agg
PPD
UR
AC M
PDU
(MFB
:Rat
e)
Spoofed Length
Spoofed
Length / Rate Length / Rate
Dat
a M
PDU
Dat
a M
PDU
March 2005
Syed Aon Mujtaba, Agere Systems, et. al.
Slide 98
doc.: IEEE 802.11-04/888r9
Submission
Channel Selection Support 20/40 MHz and 20 MHz operating modes of
whole BSS In 20/40 MHz mode, all legacy PPDUs are 20 MHz, all
HT PPDUs exchanged between HT STA are either 40 MHz or 20 MHz depending on operating mode and STA capability
Channel selection constraints■ Partial overlap between HT systems is not allowed■ Legacy STAs are only allowed in the control sub-channel except
in 20 MHz-base managed mixed mode An HT AP responds to changes in environment to