Introduction to Smart Introduction to Smart AntennaAntenna

AdvisorAdvisor ：： Dr. Wen-Jye HuangDr. Wen-Jye Huang

StudentStudent ：： Chi-Ting WuChi-Ting Wu

2004.08.182004.08.18

Wireless Communication LABWireless Communication LAB

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

Switched beam systemSwitched beam system

。 select one of several beams to enhance received signals

Adaptive antenna systemAdaptive antenna system

。 adaptive beam system can adjust its antenna pattern to enhance the desired signal

。 null or reduce interference

。 collect correlated multipath power

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 suffer different delays

► This gives rise to ISI► reject or stimulate

multipath 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

►UUniformniform L Linearinear A Arrayrray geometry geometry►UUniformniform C Circularircular A Arrayrray geometry geometry

UUniformniform L Linearinear A Arrayrray geometrygeometry

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 geometrygeometry

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 and interference, improve BER performance and hence capacityhence capacity