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2011 1st semesterommunca on ys ems

Kei Sakaguchi. . . .

May 31, 2011

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nd

Date Text Contents

#7 May 31 A-5 MIMO receiver

une - , ransm e

#9 J une 14 B-9 Adaptive commun. system

#10 J une 21 A-6, B-14 Multi-user MIMO

#11 J une 28 B-15, 16 Distributed MIMO networks

J uly 12 Final Examination

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Derive BER & throughput performances

o as c near non- near rece vers

MIMO receiver architecture

rame sync ronza on c anne es ma on

Linear MIMO detection algorithm Non- near MIMO etecton a gor t m

Measurement experiment

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Question 1escr e genera ze ma rx nverse

of non-square matrix by using SVD.H

Question 2

Prove t at t e o owng equaton o s.HH HHHH

1

Singular Value Decompositionmn

CH mn Non-square matrix:

H mn mm mm

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MIMO detectionx. , , -

OFDM

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anne estmaton

Decision feedback

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Preamble with repetition sequence

Training Data

pL

1

*p

)(

L

Litit yytP0

p

i

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Cyclic delay preamble

Tx #1

Tx #2

Tx #3

Tx #4

Without cyclic delay With cyclic delayNull beamforming effect Transmit delay diversity

)(

)(

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Ex eriment on MIMO S nchronization

Performance improvement owing to transmit & receive diversity

Performance of frame synch.

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h nn l E tim ti n

hAt each receive antenna

1s

Training signals

2h yny s

2sn

T

hs S

tMh

tMs

Training signal

nhSy

tp,,, 21pML

M C

tsssS

Channel estimation erro

pL

Channel estimation

pppp

nShySh

2

pp

22

ce E

1E

1

nShh

HH p1

ppp SSSS

1pp2

pp

2

TrTr SSSS H

H

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tt

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tim l Tr inin nChannel estimation error

1h1s

Training signals

1ppt

2

ce Tr

SSHM

2h y

2s

pS

Optimal training sequence

1Tr

SSH is minimal

tMh

tMs

t

t

p

pp M

H

M

PL ISS whenPL

M

p

2t2

ce

pL

Receive signal with channel estimation error

NHH MH

22

tE NN Effective noise

nsHnsNsHnHsy ~ ce

PLp

r

1~~E t2 MH M

Inn

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p

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Schemes Performance Complexity

LineaZF

Low Low

VBLASTHybrid

QRM-MLDMedium Medium

Non-linear MLD High High

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1st stream

rm

1111

Wys

rrtt mmmm yww 1Mt-th stream

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Interference Cancellation Detection

(Zero Forcing)ece ve s gna

nHsy

0dB 0dB -25dB 0dB

HH HHHHW 1

ZF weight

Estimated signal

~

Effective SNR for i-th stream

2~~E

HHnn

HH

Diversity orderZF

P

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12

ii

H

tM HH

trd

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Minimum Mean S uare Error Detection

Cost function0dB 0dB -25dB 0dB

2E WysW J

0

WJ

H

M

H MHIHHW

12

t

t

Effective SNR for i-th stream

11

2

MMSE

t

M

H

i

PIHH

Diversity order

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t iitr

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No diversity gain if tr MM

No performance gain of MIMO (moreover noise enhancement)

Noise

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High performance due to multiplexing gain at high SNR region

Multi lexingain

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Diversity order increases stage by stage

t

stageMM tr

vers y or e

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Diversity gain owing to successive interference cancellation

Diversity gain

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Diversity gain improves the throughput performance at lower SNR region

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Maximum likelihood detection

~

~minarg sHyss

2 Tx with QPSK signaling

Pair wise error probability

2

2)(

erfc1

)(ki

kipssH

ss

r2M

ikdP

1h 2Diversity order

t

24 M

Computational cost

rd

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t

ary combinations on r receiver branches

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-

Full receive diversity due to MLD at all receive branches

Full receive diversity

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-Maximal available throughput among all MIMO detection schemes

s compu a ona compex y s a mos pro e

Full receive diversity

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-QRM-MLD approaches the performance of MLD asymptotically

-

tmsrr 1111

ttt mmm sr00

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pper ranguar ecompos on:

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QRM-MLD achieves full receive diversity as with MLD

SNR penalty

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In IID, performance of VBLAST & QRM-MLD are almost the same

SNR penalty

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Com arison of MIMO Detection Schemes

Multi lexin ain Diversit ain

MMSE

VBLAST sta e

1tr MMtM

MLD

QRM-MLD tM rM

Complexity

MMSE

VBLAST

)((INV) rtOLO )(2(INV)

rttMMOLOM

MLD

QRM-MLD )2/)1(()QRD( ttrt MMMMMOLO)( taryrtO

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:L Number of symbols

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Measurement conditionMIMO structure 4 (Tx) x 4 (Rx)

linear array

MIMO receive scheme ZF, MMSE, VBLAST, MLD

, , ,

Frame structure IEEE802.11a based

Packet length 480 bits

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Slight spatial correlation will affect MIMO performance

Pathloss distribution Spatial correlation

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BER performance agrees with that in Rayleigh environment

Degradation of throughput performance is due toimperfection of frequency characteristics in RF transceiver

BER performance Throughput performance

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Performance de radation of BER is due to s atial correlation

RF impairment & spatial correlation degrades throughput performance

BER performance Throughput performance

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MIMO receiver architecture

ransmt rece ve vers ty on rame sync ronzaton

Orthogonal preamble sequences for MISO channel estimation

MIMO detection algorithm

Multi lexin ain to im rove throu h ut erformance

Diversity gain to improve BER performance Tradeoff between complexity & performance (diversity order)

near sc emes ,Non-linear schemes (VBLAST, MLD, QRM-MLD)

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