01 OWA200002 WCDMA RAN Fundamental (With Comment) ISSUE1 (2)

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OWA200002 WCDMARAN Fundamental

ISSUE1.0

HUAWEI TECHNOLOGIES CO., LTD. Page 2All rights reserved

Upon completion of this course, you will be able to:

�Outline the advantage of CDMA technology

�Outline the fundamentals of UTRAN

�Outline the key technologies of UTRAN


ChapterChapter 1 CDMA1 CDMA FundamentalFundamental

ChapterChapter 2 WCDMA Key Technologies2 WCDMA Key Technologies


Multiple Access Technology

frequencytime

power

FDMA

frequencytime

power

TDMA

power

time

CDMA

frequency


Characteristics of CDMA System

� High Spectral Efficiency

� Frequency multiplex coefficient is 1.

� soft capacity

�Quality

�Coverage

� Interference

� Self-interference system

�A UE transmission power is interference for another UE.


Correlation� Correlation is a measure of similarity of between any two arbitrary signals.

� EXAMPLE:

-1 1 -1 11 1 1 1

-1 1 -1 1Zero correlation

Orthogonal signals

-1 1 -1 1-1 1 -1 11 1 1 1

1 correlationIdentical signals

+10

-1+10

-1

+10

-1

+10

-1

(a)

(b)


Spreading

UE1: ＋1 －1 1

UE2: －1 ＋1

c1: ＋1 －1 ＋1 －1 ＋1 －1 ＋1 －1

c2: ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1

UE1×c1：：：：＋1 －1 ＋1 －1 －1 ＋1 －1 ＋1

UE2×c2：：：：－1 －1 －1 －1 ＋1 ＋1 ＋1 ＋1

UE1×c1＋＋＋＋ UE2×c2：：：： 0 －2 0 －2 0 ＋2 0 ＋2

UE1: ＋1 －1 1

UE2: －1 ＋1

c1: ＋1 －1 ＋1 －1 ＋1 －1 ＋1 －1

c2: ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1

UE1×c1：：：：＋1 －1 ＋1 －1 －1 ＋1 －1 ＋1

UE2×c2：：：：－1 －1 －1 －1 ＋1 ＋1 ＋1 ＋1

UE1×c1＋＋＋＋ UE2×c2：：：： 0 －2 0 －2 0 ＋2 0 ＋2


Dispreading

UE1×c1＋＋＋＋ UE2×c2: 0 －2 0 －2 0 ＋2 0 ＋2

UE1 Dispreading by c1: ＋1 －1 ＋1 －1 ＋1 －1 ＋1 －1

Dispreading result: 0 ＋2 0 ＋2 0 －2 0 －2

Integral judgment: ＋＋＋＋4 (means＋＋＋＋1) －－－－4 (means－－－－1)

UE2 Dispreading by c2: ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1

Dispreading result: 0 －2 0 －2 0 ＋2 0 ＋2

Integral judgment: －－－－4 (means－－－－1) ＋＋＋＋4 (means＋＋＋＋1)

UE1×c1＋＋＋＋ UE2×c2: 0 －2 0 －2 0 ＋2 0 ＋2

UE1 Dispreading by c1: ＋1 －1 ＋1 －1 ＋1 －1 ＋1 －1

Dispreading result: 0 ＋2 0 ＋2 0 －2 0 －2

Integral judgment: ＋＋＋＋4 (means＋＋＋＋1) －－－－4 (means－－－－1)

UE2 Dispreading by c2: ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1 ＋1

Dispreading result: 0 －2 0 －2 0 ＋2 0 ＋2

Integral judgment: －－－－4 (means－－－－1) ＋＋＋＋4 (means＋＋＋＋1)


Spectrum Analysis of Spreading & Dispreading

Spreading code

Spreading code

SignalCombination

Narrowband signalf

P(f)

Broadband signal

P(f)

f

Noise

P(f)

f

Noise+Broadband signal

P(f)

f

Recovered signalP(f)

f


ChapterChapter 1 CDMA1 CDMA FundamentalFundamental

ChapterChapter 2 WCDMA Key Technologies2 WCDMA Key Technologies


Sourcecoding

Channelcoding

Spreading Modulation

Sourcedecoding

Channeldecoding Despreading Demodulation

Radio channelRadio channelRadio channel

Processing Procedure of WCDMA System

Transmission

Reception


Terms

� Bit, Symbol, Chip

�Bit : data after source coding

�Symbol: data after channel coding and interleaving

�Chip: data after spreading

�Process Gain: 10log (cps/bps); for different service, the Gain is different

− Process Gain is smaller, UE need more power for this service

− Process Gain is smaller, the coverage of the service is smaller


WCDMA Source Coding

� AMR (Adaptive Multi-Rate) voice coding

�Multi-rate:

− 8 kinds of coding rates

− Benefit multi-mode terminal design

�Adaptation: when cell load increases, the system will decreasespeech rate of part of subscribers automatically so as to supportmore subscribers.


WCDMA Channel Coding

� Purpose:

�Enhance the correlation among symbols so as to recover the signalwhen interference occurs.

� Types

�Speech service: Convolution code（1/2、1/3）

�Data service: Turbo code


� Interleaving is used for continuous bit error correction

WCDMA Interleaving

1 2 3 4 5 6 7 8 ... ... 452 453 454 ……1 2 3 4 5 6 7 8 ... ... 452 453 454 ……

816...

456

816...

456

210...

450

210...

450

614...

454

614...

454

19...

449

19...

449

412...

452

412...

452

715...

455

715...

455

311...

451

311...

451

513...

453

513...

453

.... ....

B0 B1 B2 B3 B4 B5 B6 B7

{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}

First interleaving

Second interleaving


WCDMA Spreading Code: OVSF Walsh

� OVSF: Orthogonal Variable Spreading Factor, generated by Walsh matrix

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

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

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

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

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

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


Purpose of OVSF

� For uplink, OVSF is used to separate different services of one connection

� For downlink, OVSF is used to separate different connections

6412812.2+3.4AMR

4

8

16

32

Uplink SF

812.2+384+3.412.2kAMR & 384k packet data



6428.8+3.4Modem28.8k

Downlink SFData rateTypical service


Why we need scrambling code

�Distinguishing cells or users

�Downlink

�Scrambling code is used for distinguishing cells

�OVSF code is used for distinguishing users

�Uplink

�Scrambling code is used for distinguishing users

�OVSF code is used for distinguishing channels of one user


WCDMA Scrambling Code: Gold Sequence

�Gold sequence is made by two m sequence.

�Advantage: No need to use GPS as the system clock, NodeBcan work in asynchronous mode, and it is also convenient forindoor coverage

�Disadvantage: the interference between code is larger than msequence


WCDMA Modulation

� Different modulation methods corresponding to different transmittingabilities in air interface

�R99/R4: adopt QPSK

�DL max data rate is 2.7Mbps

HSDPA: adopt 16QAM

DL max data rate is 14.4Mbps


Multi-path Environment

Time

Receivedsignal

Transmitted

signal


Fading

Distance(m)

Received Power(dBm)

10 20 30

-20

-40

-60

Slow fading

Fast fading


Introduction to Diversity Technique

� Diversity technique is used to obtain uncorrelated signals for combining

�Reduce the effects of fading

� Improve the reliability of communication

� Increase the coverage and capacity

� Diversity methods

�Time diversity

�Frequency diversity

�Space diversity


Principle of RAKE Receiver

Receive set

Correlator 1

Correlator 2

Correlator 3

Searcher correlator Calculate thetime delay andsignal strength

CombinerThe

combinedsignal

tt

s(t) s(t)

RAKE receiver help to overcome on the multi-path fading and enhance the receiveperformance of the system


Structure of RAKE Receiver

∑∑∑∑Q

∑∑∑∑ I

Combiner

I

MatchedFilter

PhaseRotator

ChannelEstimator

DelayEqualizer

I

Q

Path 1

Path 2

Path 3

Input signal

Correlator

CodeGenerators Q


WCDMA Fast Power Control – Control Fast Fading

Without power control With power control

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01 OWA200002 WCDMA RAN Fundamental (With Comment) ISSUE1 (2)

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