Electronics

2 and 4 Tx MIMO System

10-11 April 2006

CJK-B3G #11

2/18Contents

1. Introduction

2. MIMO scheme set Two Tx scheme

Four Tx scheme

Closed-loop scheme for rate-1

STC-HARQ scheme

3/181. Introduction

Feedback overhead reduction

OFDM TxMIMO

Channel coder Modulation

Coding and Modulation

LDC scheme MIMO-Pilot

OFDM RxMIMO DemodulatorDecoding and Demodulation

MLD or QRM-MLD

Channel

PAPR reduction scheme

Synchronization

Channel estimation

SchedulerH-ARQ, Power control, MCS adaptation, Bit loading, Per stream power control, Per antenna rate control,

OFDM mode change, MIMO mode change

CINR measurement

Feedforward Feedback

Downlink Multi-user MIMO

Uplink MIMO

1.1 Overall system

Sub-carrier allocation

Decoder DemapperMMSE

4/181. Introduction

1.2 LDC (Linear dispersion code) [’02 Heath, ’02 Hassibi]

Nt, Nr : number of transmit and receive antennas

T : LDC period

Q : number of symbols

Aq, Bq : T x Nt dispersion matrix

i, i : real and imaginary value of ith symbol

Every multi-antenna transmit scheme can be expressed in form of LDC

Ex. Alamouti scheme

1

Q

q q q qq

S A j B

01

10

01

10

10

01

10

012211*

1*2

21

1

21

jjss

ssT

T

AntAnt

5/181. Introduction1.3 Design criterion

Pairwise error probability (PEP)

Capacity

H

Hi

NrS

Nr

ii

SSSSr

SSSS

NESS r

r

'' ofrank :

'' of eigenvalue zeronon :

4/)sent|detect'Pr( 01

2, , 1...

1, , max log det

2q q

TLD NrT

A B q QC Nt Nr E I

T Nt

HH

, , , , ,

, , , , ,

, , R q I q I q R q R nn

I q R q R q I q I n

hh

h

A A B B

A A B Bq qA B

,1 ,1

,1 ,1

, ,

, ,

,

R R

I I

R Nr R Nr

I Nr I Nr

y n

y n

Nty n

y n

1

1

Q

Q

H1 1 1 1 1 1

1 1

Q Q

Nr Nr Q Nr Q Nr

h h h h

h h h h

A B A B

H =

A B A B

Equivalent channel model

6/182. MIMO scheme set2.1 Two Tx Rate-1 Scheme [’98 Alamouti]

2.2 Two Tx Rate-2 Scheme [LGE proposal]

IRIR

IRIR

ji

Ii

Rii

xjxxxjxx

xjxxxjxx

esxjxxwherexxj

xx

144233

322411

1

43

21

~,~

~,~

)2(tan2

1,~~

~~

*1

*2

21

1

21

ss

ss

TT

antant

21: ssSM

2.2.1 Another candidates

2

51,

1

1:CMatrix e16.802

4132

3241

2

rsjrssrs

rssjrss

r

7/182. MIMO scheme set

2.2.2 Simulation result

CF> IEEE802.16 Matrix-C has identical performance with the proposal

8/182. MIMO scheme set

2.3 Advantages

SMIEEE802.16e

Matrix CProposal

Decoding complexity

High(2x2 ML)

Low (2x2 MMSE)

High (4x4 ML)

Moderate (4x4 MMSE)

High (4x4 ML)

Low (2x2 MMSE)

Encoding complexity

Low

(no manipulation on signal)

High

(signal multiplication & addition)

Moderate

(signal rotation & reconstruction)

Performance

ModerateBetter, especially in high code rate

Better, especially in high code rate

9/182. MIMO scheme set

2.4 Four Tx Rate-1 scheme [’04 Sethuraman]

IRIRIRIR

ji

Ii

Rii

xjxxxjxxxjxxxjxx

esxjxxwhere

xx

xx

xx

xx

144233322411

1

*3

*4

43

*1

*2

21

~,~,~,~

)2(tan2

1,

~~00

~~00

00~~00~~

*3

*4

43

*1

*2

21

00

00

00

00

:AMatrix IEEE802.16

ss

ss

ss

ss

2.4.1 Another candidates

10/182. MIMO scheme set

2.4.2 Simulation result

MMSE receiver

11/182. MIMO scheme set

2.5 Four Tx Rate-2 scheme [’04 Sethuraman]

IRIRIRIR

IRIRIRIR

ji

Ii

Rii

xjxxxjxxxjxxxjxx

xjxxxjxxxjxxxjxx

esxjxxwhere

xxxx

xxxx

xxxx

xxxx

188277366455

544633722811

1

*7

*8

*5

*6

8765

*3

*4

*1

*2

4321

~,~,~,~

~,~,~,~

)2(tan2

1,

~~~~

~~~~

~~~~

~~~~

2.6 Four Tx Rate-4 scheme

4321 ssss

12/182. MIMO scheme set

2.7 Closed-loop MIMO

2.7.1 Codebook

A set of pre-defined precoding matrices

Moderate feedback overhead (3~6 bits)

Selection criteria [‘03 Love] ML

MMSE

Rx

NrNt

Feedback information

Precoding

W

s1

s2...

sm

H

2

,

)(minmaxarg: jiSSW

optML SSHWwSCji

tdeterminanor ceeither tra is)(where

minarg: 1

M

HWHWIMwSC HH

WoptMMSE

13/182. MIMO scheme set

2.7.2 Four tx rate-1 closed-loop scheme [LGE proposal]

1

1

1

))((

~,~,~,~

432

3

22

144233322411

1

*3

*3

*4

*4

4433

*1

*1

*2

*2

2211

)2(tan2

1,

~~~~

~~~~

~~~~

~~~~

TTT

T

T

NNN

N

N

Ht

IRIRIRIR

ji

Ii

Rii

HHER

realsign

xjxxxjxxxjxxxjxx

esxjxxwhere

xxxx

xxxx

xxxx

xxxx

2.7.3 Advantage over codebook approach

Low feedback overhead (1 bit)

Less sensitive to mobility because of using channel statistics

14/182. MIMO scheme set

2.7.4 Simulation

00.10.20.30.40.50.60.70.80.912.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

(low mobility <<-->> high mobility)

Req

uire

d S

NR

(dB

) fo

r 1%

SE

R

Proposed scheme

Codebook schemeOpen-loop

30km/h & 2ms feedback delayor

20km/h & 3ms feedback delay

30km/h & 5ms feedback delay

t

kHkk

Hk

R

HHEHHE

delayfeedback :

ncorrelatio time:

•Codebook size: 8 (3bit feedback required)•Proposed scheme(1bit feedback required)

15/182. MIMO scheme set

2.8 STC-HARQ (IEEE802.16e)

*3

*4

*1

*2

~~

~~

xjx

xx

43

21~~

~~

xxj

xx

4

3

2

1

s

s

s

s

*3

*4

*1

*2

s

s

s

s

43

21~~

~~

xxj

xx

Initial transmission

Odd retransmission

Even retransmission

2 Tx

4 Tx

4

3

2

1

s

s

s

s

Alamouti pair

16/182. MIMO scheme set

2.8.1 Adaptive STC-HARQ [LGE proposal]

1s

2s

3s

4s

*2s*1s*4s*3s

1s

2s

3s

4s

*2s*1s*4s*3s

Alternative 1 Alternative 2 Alternative 3

ACK/NACK signals (2bits): ACK,

NACK w/ alt 1,

NACK w/ alt 2,

NACK w/ alt 3

1s

2s

3s

4s

*2s*1s*4s*3s

17/182. MIMO scheme set

2.8.2 Simulation Results

802.16e system

20ms difference between transmission and retransmission

18/18

Thanks