001 Wcdma Ran Fundamental Issue

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OWA200002 WCDMA

RAN Fundamental

ISSUE1.0




Section 1 3GSection 1 3G OverviewOverview

Section 2 CDMASection 2 CDMA FundamentalFundamental

Section 3 WCDMA Key TechnologiesSection 3 WCDMA Key Technologies

Section 4 PerformanceSection 4 Performance EnhancementEnhancement MethodsMethods




Different Service, Different Technology

AMPS

TACS

NMT

Others

1G 1980sAnalog

GSMGSM

CDMACDMAIS-95IS-95

TDMATDMA

IS-136IS-136

PDCPDC

2G 1990sDigital

Technologiesdrive

3GIMT-2000

UMTSUMTS

WCDMAWCDMA

CDMACDMA

20002000

Demandsdrive

TD-SCDMA

TD-SCDMA

3G provides compositive services for both operators and subscribers




3G Evolution

Proposal of 3G

IMT-2000: the general name of third generation mobile

communication system

The third generation mobile communication was first proposed in

1985，and was renamed as IMT-2000 in the year of 1996

− Commercialization: around the year of 2000

− Work band : around 2000MHz

− The highest service rate :up to 2000Kbps




3G Objectives

3G is developed to achieve:

Universal frequency band for standard and seamless global

coverage

High spectral efficiency

High quality of service with complete security and reliability

Easy and smoothly transition from 2G to 3G, compatible with 2G

Provide multimedia services, with the rates:

Vehicle environment: 144kbps

Walking environment: 384kbps

Indoor environment: 2Mbps




1850 1900 1950 2000 2050 2100 2150 2200 2250

ITU

Europe

USA MSSPCS

A D B BC D CE F A FEMSSReserveBroadcast auxiliary

2165 MHz1990 MHz

1850 1900 1950 2000 2050 2100 2150 2200 2250

1880 MHz 1980 MHz

UMTSGSM 1800 DECT MSS

1885 MHz 2025 MHz

2010 MHz

IMT 2000

MSSUMTS

Japan MSSIMT 2000MSSIMT 2000PHS

1 8 9 5

1 9 1 8

BC

1 8 8 5

A A’

2170 MHz

IMT 20002110 MHz 2170 MHz

MSS MSS

CDMA

TDDWLL

FDDWLL

1 9 8 0

2025MHz

GSM1800 CDMA

FDDWLL

1 9 6 0

1 9 2 0

1 9 4 5

China

cellular(1) cellular(2) cellular(2)

1805 MHz

1 8 6 5

1 8

6 5

1 8

7 0

1 8

8 5

1 8

9 0

1 8

9 5

1 9

1 0

1 9

3 0

1 9

4 5

1 9

6 5

1 9

7 0

1 9

7 5

3G Spectrum Allocation




Bands WCDMA used

Main bands

1920 ~ 1980MHz / 2110 ~ 2170MHz

Supplementary bands: different country maybe different

1850 ~ 1910 MHz / 1930 MHz ~ 1990 MHz (USA)

1710 ~ 1785MHz / 1805 ~ 1880MHz (Japan)

890 ~ 915MHz / 935 ~ 960MHz (Australia)

……

Frequency channel number＝

central frequency×

5, for main band:− UL frequency channel number：9612～9888

− DL frequency channel number : 10562～10838




Section 1 3G OverviewSection 1 3G Overview

Section 2 CDMA FundamentalSection 2 CDMA Fundamental

Section 3 WCDMA Key TechnologiesSection 3 WCDMA Key Technologies

Section 4 Performance Enhancement MethodsSection 4 Performance Enhancement Methods




Multiple Access Technology

f r e q u

e n c y

t i m e

power

FDMA

f r e q u e n c

y

t i m e

power

TDMA

power

t i m e

CDMA

f r e q u e n c y




Correlation

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

EXAMPLE:

-1 1 -1 1

1 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)




Section 1 3G Overview

Section 2 CDMA Fundamental

Section 3 WCDMA Key Technologies

Section 4 Performance Enhancement Methods




Source

coding

Channel

coding

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 support

more subscribers.




WCDMA Channel Coding

Purpose:

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

TypesSpeech 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 ……

8

16

.

.

.

456

8

16

.

.

.

456

2

10

.

.

.

450

2

10

.

.

.

450

6

14

.

.

.

454

6

14

.

.

.

454

1

9

.

.

.

449

1

9

.

.

.

449

4

12

.

.

.

452

4

12

.

.

.

452

7

15

.

.

.

455

7

15

.

.

.

455

3

11

.

.

.

451

3

11

.

.

.

451

5

13

.

.

.

453

5

13

.

.

.

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 for

indoor coverage

Disadvantage: the interference between code is larger than m

sequence




WCDMA Modulation

Different modulation methods corresponding to different transmitting

abilities 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

Received

signal

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 correlatorCalculate the

time delay andsignal strength

Combiner Thecombinedsignal

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

Matched

Filter

Phase

Rotator

Channel

Estimator

Delay

Equalizer

I

Q

Path 1

Path 2

Path 3

Input signal

Correlator

Code

Generators Q




WCDMA Fast Power Control – Control Fast Fading

Without power control With power control




Section 1 3G Overview

Section 2 CDMA Fundamental

Section 3 WCDMA Key Technologies

Section 4 Performance Enhancement Methods

HSDPA K T h i O iHSDPA K T h i O i




HSDPA Key Techniques - OverviewHSDPA Key Techniques - Overview

AMC (Adaptive modulation andcode )

Fast SchedulingHARQ（（（（Hybrid ARQ））））

16QAMSF16, 2ms and CDM/TDM 3 New Physical Channels




AMC (Adaptive Modulation & Coding) based on Channel Quality Feedback

Adjust data rate to compensate channel conditions

− Good channel condition – Higher rate

− Bad channel condition – Lower rate

Adjust the coding rate to compensate channel conditions

− Good channel condition –3/4

− Bad channel condition –1/3

Adjust the modulation scheme to compensate channel conditions

− Good channel condition –16QAM

− Bad channel condition – QPSK

Channel Quality Feedback (CQI)

UE measures the channel quality (SNR) reports (every 2ms or more cycle) to Node-B

Node-B choose modulation and block size, data rate primarily based on CQI

HSDPA Key Techniques - AMCHSDPA Key Techniques - AMCHigh data rate

Low data rate




HSDPA Key Techniques - HARQHSDPA Key Techniques - HARQ

Conventional ARQ

–Received Transmitted blocks are decoded

–Checked for CRC errors on decoded blocks

–If errors

•discard the error bolcks•Request the trasmitter forretransmission

Hybrid ARQ

–Received Transmitted blocks are decoded

–Checked for CRC errors on decoded blocks

–If errors

•Store the erroneous block without discarding•Request the trasmitter for retransmission

•Combine the received re-trasmission withpreviously received trasnmisison

HARQ with Soft Combining

NodeB

UE Packet1? N

Packet 1 Packet 1

Packet 1

Packet1?

+A

Packet2

Transmitter

Receiver




HSDPA Key Techniques - Fast scheduling

Scheduler may be based on

CDM, TDM

Channel condition

Amount of data waiting in the queue (delay)

Fairness (satisfied users)

Cell throughput, etc

Schedulingdetermineswhich user

shall betransmitted.




HSDPA Key Techniques – CDM and TDM

Channelization codes allocated

for HS-DSCH transmission8 codes (example)SF=16

SF=8

SF=4

SF=2

SF=1

User #1 User #2 User #3 User #4

TTI

Sharedchannelization

codes

10 ms20 ms40 ms

80 ms

Earlier releases

2 ms

Rel 5 (HS-DSCH)

“sub-frames” (2560 chips)




HSDPA Key Techniques – 16QAM

HSDPA Modulation

QPKS16QAM




Smart Antenna

Omni antenna Directional antenna Smart antenna




Smart Antenna Reduce interference

Increase coverage and capacity

Wanted signal

interference




Summary

Spreading/Dispreading principle

UTRAN Voice Coding

UTRAN Channel Coding

UTRAN Spreading Code

UTRAN Scramble Code

UTRAN Modulation

UTRAN Transmission/Receiving



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001 Wcdma Ran Fundamental Issue

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