第四讲 WCDMA系统技术.docxVIP

第四讲

第四讲WCDMA技术

孟维晓

2003-4-9 哈工大通信所 1

内容提纲

内容提纲

2G的技术限制

直接扩频和解扩技术

Rake接收功率控制系统容量软切换

WCDMA与cdma200的比较

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1.2G的技术限制

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2.直接扩频和解扩技术

2.直接扩频和解扩技术

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DS-CDMA技术原理

DS-CDMA技术原理

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PrincipleofDS-CDMA

Input

Data

Spreading

Despreading

Data

Output

data

modulation

(1) (2) (3)

demodulation(4)

data

PowerPowerPowerPowerSpreadingcode

Power

Power

Power

Power

Spreadingcode

FrequencyFrequencyFrequencyFrequencyTransmitdata(Narrowbanddata)

Frequency

Frequency

Frequency

Frequency

Transmitdata(Spreaddata)

Receiveddata(withinterference)

Recovereddata(De-spreaddata)

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Spreading/Despreading

Spreadingcodesequence

Chipperiod(=260nsec@3.84Mcps)

-11Transmitteddatasequence

-1

1

User2

Spreading

1111-

1

1

1

1

-1

-1

-1

-1

11

1

1

Compositesignal

Spreadingcodereplica

-

-1

-1

-1

-1

1

1

1

1

IntegratedumpRecoveredtransmitteddatasequenceforUser

Integratedump

User

User1

-1

-1

-1

-1

1

1

1

1

-

-1

1

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Cch,2,0=(1,1)Cch,4,0=(1,1,1,1)Cch,4,1

Cch,2,0=(1,1)

Cch,4,0=(1,1,1,1)

Cch,4,1=(1,1,-1,-1)

Cch,1,0=(1)

Cch,2,1=(1,-1)

SF=1

SF=2

Cch,4,2=(1,-1,1,-1)

Cch,4,3=(1,-1,-1,1)

SF=4

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OrthogonalVariableSpreadingfactor(OVSF)codesareusedaschannelizationcodes.

OVSFisrecursivelygeneratedasthetree-structuredcodeset.

ByusingOVSFcodes,orthogonalityamongthechannelswithdifferentspreadingfactors(symbolrates)isachieved.

Orthogonal

OrthogonalMulti-SF

VerFificoatriownoaforrdthoLgLonianlitky

Example@3.84Mcps

One

Onesymbolperiod

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162408480

16

240

8

480

8

480

4

960

4

960

ksymbols/s

SF

Datarate

1111 1111 0000 0000

Multi-SFcode

1001

1001

1010

1010

1100

1100 1100

1111

1111 0000

● ●●●

●● ●●

1100

1100 1100

1111 0000

2-layeredSpreadingCode

Channelization

ChannelizationCode(Shortcode)

ScramblingCode(Longcode)

CodeLength

1InformationSymbol

1Frame(10ms)