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doc.:IEEE 802.11-09/0303March 12, 2009
Effect of SDMA in 802.11acA thAuthors:
Name Affiliations Address Phone email Naoki Honma NTT Corp. 1-1 Hirkarinooka, Yokosuka-shi,
Kanagawa, Japan, 239-0847+81-46-859-5107 honma.naoki@lab.ntt.co.jp
Kentaro Nishimori NTT Corp. 1-1 Hirkarinooka, Yokosuka-shi, Kanagawa, Japan, 239-0847
+81-46-859-8266 nishimori.kentaro@lab.ntt.co.jp
Riichi Kudo NTT Corp. 1-1 Hirkarinooka, Yokosuka-shi, Kanagawa Japan 239-0847
+81-46-859-3140 riichi.kudo@lab.ntt.co.jp Kanagawa, Japan, 239 0847
Yasushi Takatori NTT Corp. 1-1 Hirkarinooka, Yokosuka-shi, Kanagawa, Japan, 239-0847
+81-46-859-8596 takatori.yasushi@lab.ntt.co.jp
Submission NTT CorporationSlide 1
doc.:IEEE 802.11-09/0303March 12, 2009
Contents
1. Introduction1. Introduction
1 Evaluation of SDMA effect1. Evaluation of SDMA effect
1 Effect of time variant channel1. Effect of time-variant channel
1 C l i1. Conclusion
Submission NTT CorporationSlide 2
doc.:IEEE 802.11-09/0303March 12, 2009
Introduction• In PAR of TGac, more than 1 Gbps throughput must
be achieved with multiple STAs.
• MIMO-SDMA can be a key technology to reach this y gyvery high throughput.
• The feasibility of MIMO-SDMA is evaluated in an actual indoor office environment which can be aactual indoor office environment, which can be a typical scenario in 802.11ac.
Submission NTT CorporationSlide 3
doc.:IEEE 802.11-09/0303March 12, 2009
Contents
1. Introduction1. Introduction
1 Evaluation of SDMA effect1. Evaluation of SDMA effect
1 Effect of time variant channel1. Effect of time-variant channel
1 C l i1. Conclusion
Submission NTT CorporationSlide 4
doc.:IEEE 802.11-09/0303March 12, 2009
Measurement SetupAP
D/AMapper Up convIFFT D/AMapper Up convIFFTer
#1
STA 1 STA 4
D/A
D/A
D/A
Mapper
Mapper
M
Up conv.
Up conv.
Up convIFFT
IFFT
IFFT
D/A
D/A
D/A
Mapper
Mapper
M
Up conv.
Up conv
Up conv.IFFT
IFFT
IFFTmul
tiple
xe #2
#3STA-1
STA 2
STA-4D/A
D/A
Mapper Up conv
Up conv.IFFT
IFFT
D/A
D/A
Mapper Up conv.
Up conv.
IFFT-W
eigh
t m
IFFTS/P #4
MapperMapper
STA-3STA-2.
Inter -
D/AMapper
Conv.
.
Inter -Inter -
IFFTTx-
#16
Tx-
Up conv
16 16 MIMO h l t d d t ectio
n FFT
FFT oder
mapperDe-
De-ectio
n FFT
FFT oder
mapperDe-
mapperDe-
-conv.Down
Down AGC/
AGCA/D
#1
#2
leaver encoderleaverleaver data
•16x16 MIMO channel measurements and data transmission at 5GHz with 20MHz BW were conducted at a typical office room in NTT lab.
min
g de
te FFT
FFT
SDM
dec
o mapper
mapperDe-
Dmin
g de
te FFT
FFT
SDM
dec
o mapper
mapperDe-
D
S/P-conv.
-conv.Down
D
A/D
AGC
AGCA/D
#3
#4•Downlink performances were evaluated for up to 8 STAs in static and time variant channels.
Tim
FFT
S
lDe-inter
mapperDe-Ti
m
FFT
S
De-inter
mapperDe-
ViterbiD
-conv.Down AGC
A/D#4
Rx-d
Submission NTT CorporationSlide 5
0leaverDec.data
doc.:IEEE 802.11-09/0303D l d M t S t
March 12, 2009Developed Measurement System
Transmit antennas
Rx site1.7 m
Transmitters (16)
Receivers (16)
Tx site
( )
Received antennas
LNAs0.7 m
Submission NTT CorporationSlide 6
doc.:IEEE 802.11-09/0303March 12, 2009
Transmission ParametersSignal format based on IEEE802.11n is used.
Number of antennas (Tx) 16 (Element spacing: 1λ) N b f t (R ) 2 3 4 (El t i 0 5λ)
g
Number of antennas (Rx) 2, 3, 4 (Element spacing: 0.5λ)Transmit power Max. 6 dBm (Total) Packet length 100 coded OFDM signalPacket length 100 coded OFDM signalNumber of subcarriers 48 ( Pilot 4) Pilot signal 6 20 34 48Pilot signal 6, 20, 34, 48Bit error Less than 10-7
Bandwidth 20 MHzBandwidth 20 MHzSampling rate 40 MHzModulation scheme QPSK, 16QAM, 64QAM,Modulation scheme QPSK, 16QAM, 64QAM,
256QAM, and 1024QAMCoding rate 1/2, 2/3, 3/4, 5/6, and 7/8
Submission NTT CorporationSlide 7
Cod g ate / , /3, 3/ , 5/6, a d 7/8
doc.:IEEE 802.11-09/0303March 12, 2009
Achieved over 42.8 bits/s/Hz (@SNR=30 dB)
STA-1(9.8 bit/s/Hz (196Mbps), R=5/6)
STA-2(11 bit/s/Hz (220Mbps), R=7/8) ( ( p ) )
STA-4(11 bit/s/Hz (220Mbps), R=7/8)
STA-3(11 bit/s/Hz (220Mbps), R=7/8) ( ( p ), )( ( ) )
Submission NTT CorporationSlide 8
doc.:IEEE 802.11-09/0303Transmission Rate vs Number of Receiving Antennas
March 12, 2009Transmission Rate vs. Number of Receiving Antennas
in a Static Office Environment60
50
60SDMA (NT =16, NT =NR x NU) (16x16x1)
(16x4x4)(16x8x2)
SDMA (NT =8, NT =NR x NU)
40
50
bit/s
/Hz] TDMA (NT =16, NT > NU) (16x2x8)
TDMA (NT = NR)
(16x4x4)
(16x8x1) (12 12 1)
( T , T R U)
30rate
[b (12x12x1)
(8x2x4)(8x4x2) - Spectrum efficiency strongly
depends on the number of20
mis
sion
(8x8x1)
(16x4x1)
(8x2x4) depends on the number ofantennas at AP.-Even with 2 or 4 antennas at
10 SNRave.
= 31dBTran
sm
(N x N x N )(4x4x1)
( 6 ) Even with 2 or 4 antennas ateach STA, 20bit/s/Hz (NR=8)and 40bit/s/Hz (NR=16) were
00 4 8 12 16
N b f i i t (N )
(NT x NR x NU) ( R )attained.
Submission NTT CorporationSlide 9
Number of receiving antennas (NR)
doc.:IEEE 802.11-09/0303March 12, 2009
Transmission Rate per STA vs. Number of STAs
12 MIMO-TDMATransmission rate becomess/
Hz]
(16x2)(SNR = 30 dB)
8
10 Rs / U.
TA [b
it/s
MIMO-SDMA(16x2)
U: Number of users
6
8
MIMO-SDMA yields aper S
TA
(16x2)
4
yhigher transmission ratethan MIMO-TDMA, whenon
rate
MIMO-TDMA11n(2x2)
2 the number of users isincreased.
nsm
issi
o (2x2)
11a(1x1)01 2 3 4 5 6 7 8
N b f
Tran 11a(1x1)
Submission NTT CorporationSlide 10
Number of users
doc.:IEEE 802.11-09/0303March 12, 2009
Contents
1. Introduction1. Introduction
1 Evaluation of SDMA effect1. Evaluation of SDMA effect
1 Effect of time variant channel1. Effect of time-variant channel
1 C l i1. Conclusion
Submission NTT CorporationSlide 11
doc.:IEEE 802.11-09/0303March 12, 2009
Evaluation in time variant channel
Tx : 8 ele.h = 2 5m
Rx : 2ele.h 0 7
D/A Up-conv.
AP h = 2.5m h = 0.7m
D/AD/A
Up-conv.Up-conv.D/A
D/Ap
AGCA/DDown-conv
Up-conv.
D/ATCP-IP
Up-conv.A/DAGCA/D
Down-conv.
Down-conv.
Preamble generatorSTA
TCP-IPChannel estimator
Submission NTT CorporationSlide 12
doc.:IEEE 802.11-09/0303March 12, 2009
Environment for the measurements
1 2
CSI is obtained fromAP to P1~P8.
26AP
354
H1(t)~ H8(t) (0 ≤ t ≤ 100msec)
26 m7
86
8 1) Without personin front of each STA
2) Wi h40 m Height: 3 m
2) With personin front of each STA
AP position STA position DeskWallPartition 1Pillar Partition 2
Submission NTT CorporationSlide 13
p p
doc.:IEEE 802.11-09/0303March 12, 2009
Capacity in time variant channel (1) Without person in front of each STA
Eigen-mode transmission (MIMO-TDMA)
Without person in front of each STA.
MIMO-SDMA (2-STAs, 2-streams)(4-STAs, 2-streams)
(8-STAs, 1-stream)
5 0
6 0
ec/H
z]
- MIMO-SDMA attains 2.8-
3 0
4 0
rate
[bit/
se
2.8fold
fold improvement overMIMO-TDMA.
MIMO-SDMA
2 0
3 0
evab
le b
it r fold - Slight fall off in ABR is
observed with MIMO-MIMO TDMA
0
1 0
0 2 0 4 0 6 0 8 0 1 0 0
Ach
i
SDMA.MIMO-TDMA
Submission NTT CorporationSlide 14
0 0 0 6 0 8 0 1 0 0D e l a y t i m e [ m s e c ]
doc.:IEEE 802.11-09/0303March 12, 2009
Capacity for time variant channel (2) With person in front of each STAWith person in front of each STA.
Eigen-mode transmission (MIMO-TDMA)MIMO-SDMA (2-STAs, 2 streams)(4 STAs, 2 streams) (8 STAs, 1 stream)
5 0
6 0
c/H
z] - MIMO-SDMA attains2 5 2 8 f ld i t
3 0
4 0
ate
[bit/
sec
2.8fold
2.5fold
2.5-2.8 fold improvementover MIMO-TDMA.
Sli ht f ll ff i2 0
3 0
vabl
e bi
t ra fold fold
MIMO-SDMA- Slight fall off inachievable bit rate isobserved with MIMO
0
1 0
Ach
iev
MIMO-TDMAobserved with MIMO-SDMA.
Submission NTT CorporationSlide 15
0 2 0 4 0 6 0 8 0 1 0 00D e l a y t im e [ m s e c ]
doc.:IEEE 802.11-09/0303March 12, 2009
Contents
1. Introduction1. Introduction
1 Evaluation of SDMA effect1. Evaluation of SDMA effect
1 Effect of time variant channel1. Effect of time-variant channel
1 C l i1. Conclusion
Submission NTT CorporationSlide 16
doc.:IEEE 802.11-09/0303March 12, 2009
Conclusions• SDMA can be important technology in TGac
– 40 bits/s/Hz frequency utilization efficiency was achieved i h 16 @ AP d 2 4 @ MTwith 16 antennas @ AP and 2 or 4 antennas @ MT.
– 20 bits/s/Hz frequency utilization efficiency was achieved with 8 antennas @ AP and 2 or 4 antennas @ MTwith 8 antennas @ AP and 2 or 4 antennas @ MT.
• Time-variant channel was measured: indoor environmentTime variant channel was measured: indoor environment– Small effect of the human body on the bit-rate was observed.– The bit-rate deterioration can be alleviated by reducing the number of y g
streams.
• TGac channel models may consider time-variant characteristics with spatially multiplexed STAs.
Submission NTT CorporationSlide 17
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