Introduction to Smart Antenna

Introduction to Smart AntennaIntroduction to Smart Antenna

指導老師：黃文傑 博士指導老師：黃文傑 博士姓 名： 吳 濟 廷 姓 名： 吳 濟 廷

2003.11.072003.11.07無線通訊實驗室無線通訊實驗室

OUTLINEOUTLINE

IntroductionIntroduction What is Smart Antenna ?What is Smart Antenna ? Why Smart Antenna ?Why Smart Antenna ? How Smart Antenna works ?How Smart Antenna works ?

• ULAULA• UCAUCA

ConclusionConclusion

IntroductionIntroduction

Rapid growth of wireless communicationRapid growth of wireless communication Multi-services requirementMulti-services requirement Effective usage of frequency bandEffective usage of frequency band Classic antennas are omni-directionalClassic antennas are omni-directional

smart antennasmart antenna

What is Smart AntennaWhat is Smart Antenna

Concept of SDMA systemConcept of SDMA system Arrange in a particular geometric formArrange in a particular geometric form Use few methods to change EM wave patternUse few methods to change EM wave pattern

• Switched beam systemSwitched beam system• Adaptive antenna systemAdaptive antenna system

Why Smart AntennaWhy Smart Antenna

Higher capacity (traffic/area) Better transmission quality and/or

coverage

Standard Coverage

Extended Coverage

Why Smart AntennaWhy Smart Antenna

Reduction of transmitter power Reduction of delay spread Accurate user position estimation

Fixed cell shape Dynamic cell shape

Limiting effects of the wireless channel

Multi-path propagation gives rise to fading inter-symbol interference time variation of signals

Co-channel interference gives rise to increased noise level and hence greater

errors

Multi-path propagation Multipath components su

ffer different delays This gives rise to ISI reject or stimulate multip

ath components by changing their radiation patterns

significantly reduce the requirements of equalization and/or increase CINR

Mobile

Smart Antenna

LoS

MP

Co-channel interference

Interference from other directions than wanted user

suppress unwanted user by placing nulls in directions of unwanted signals

improved transmission quality and/or system capacity

Mobile 2

Smart Antenna

LoS

MPMobile 1

Interference

How Smart Antenna worksHow Smart Antenna works

Wave propagationWave propagation Parametric data modelParametric data model UUniformniform L Linearinear A Arrayrray geometry geometry UUniformniform C Circularircular A Arrayrray geometry geometry

Wave propagationWave propagation

From Maxwell’s From Maxwell’s equationsequations

Homogeneous Homogeneous wave equationwave equation

f satisfy f satisfy homogeneous homogeneous wave equation wave equation

22

2 2

10E E

c t

( , )E E t r

T(r, ) ( r )E t f t 1

c

(0, ) ( ) j tE t s t e r /c B Where B is the bandwidth of s(t)

T

T

T ( )

( )

( , ) ( )

( )

j t

j t

E t s t e

s t e

r

r k

r r

(cos sin )Tk k

Parametric data modelParametric data model ( cos sin )(r , ) ( ) l lj t k x y

lE t s t e

cos sin( ) ( ) ( )

( ) ( )

l ljk x yl l

l

x t g e s t

a s t

Base-band signal

Array propagation vector ( )la

UUniformniform L Linearinear A Arrayrray geometry geometry

cos ( 1) cos( ) ( ) 1 .....Tjkd j L kd

ULAa g e e

( 1) 0T

lr l d

1

( ) ( ) ( )M

m mm

t s t

x aBase-band signal

UUniformniform C Circularircular A Arrayrray geometry geometry

2 ( 1) 2 ( 1)cos sin

T

l

l lR

L L

r

(0, ) (1, ) ( 1, )( ) ( ) .....Tj j j L

UCAa g e e e

2 ( 1) 2 ( 1)( , ) cos cos sin sin

l ll kR

L L

1( ) ( )....... ( )T

Mt s t s ts

( ) ( ) ( ) ( )t t t X A s n

1( ) ( .... ( ) ( )M L x M A a a

1

( ) ( ) ( )M

m mm

t t

x a s

ConclusionConclusion

Smart Antenna offer new ways to combat and/or exploit the spatial channel

Smart Antennas reduce co-channel Smart Antennas reduce co-channel interference, improve BER performance interference, improve BER performance and hence capacityand hence capacity