001 Wcdma Ran Fundamental Issue1

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OWA200002 WCDMA

RAN Fundamental

ISSUE1.0


Upon completion of this module, you will be able

to:

�Know the development of 3G

�Outline the advantage of CDMA technology

�Outline the fundamentals of UTRAN

�Outline the key technologies of UTRAN


Section 1 3G Section 1 3G OverviewOverview

Section 2 CDMA Section 2 CDMA FundamentalFundamental

Section 3 WCDMA Key TechnologiesSection 3 WCDMA Key Technologies

Section 4 Performance Section 4 Performance EnhancementEnhancement MethodsMethods


Different Service, Different Technology

AMPS

TACS

NMT

Others

1G 1980sAnalog

GSMGSM

CDMA CDMA IS-95IS-95

TDMATDMA

IS-136IS-136

PDCPDC

2G 1990sDigital

Technologies drive

3G IMT-2000

UMTSUMTS

WCDMAWCDMA

CDMACDMA

20002000

Demands drive

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 FE MSSReserveBroadcast 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

1895

1918

BC

1885

A A’

2170 MHz

IMT 20002110 MHz 2170 MHz

MSS MSS

CDMATDDWLL

FDDWLL

1980

2025MHz

GSM1800

CDMAFDDWLL

1960

1920

1945

China

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

1805 MHz

1865

1865

1870

1885

1890

1895

1910

1930

1945

1965

1970

1975

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

frequency

time

power

FDMA

frequency

time

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 1

1 1 1 1

-1 1 -1 1

Zero correlation

Orthogonal signals

-1 1 -1 1

-1 1 -1 1

1 1 1 1

1 correlation

Identical 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

Signal Combination

Narrowband signal

f

P(f)

Broadband signal

P(f)

f

Noise

P(f)

f

Noise+Broadband signal

P(f)

f

Recovered signal

P(f)

f


Section 1 3G Overview

Section 2 CDMA Fundamental

Section 3 WCDMA Key Technologies

Section 4 Performance Enhancement Methods


Sourcecoding

Channel coding

Spreading Modulation

Sourcedecoding

Channel decoding

Despreading Demodulation

Radio channelRadio channelRadio channel

Processing Procedure of WCDMA System

Transmission

Reception


Source decoding

Source

codingInterleaving

deinterleaving

Scrambling spreading

Despreading

Modulation

Demodulation

Transmitting

Receiving

Radio channel

DescramblingDeinterleaving &channel decoding

Channel coding &

interleaving

Processing Procedure of WCDMA System


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 decrease

speech 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 signal

when 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 ……

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, NodeB

can 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 correlator Calculate the time delay and signal strength

CombinerThe

combined signal

tt

s(t) s(t)

RAKE receiver help to overcome on the multi-path fading and enhance the receive

performance 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 Key Techniques - OverviewHSDPA Key Techniques - Overview

AMC (Adaptive modulation and code )

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 - AMC

High 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 for retransmission

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 with previously 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

Scheduling determines which user

shall be transmitted.


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

Shared channelization

codes

10 ms

20 ms

40 ms

80 ms

Earlier releases

2 ms

Rel 5 (HS-DSCH)

“sub-frames” (2560 chips)


HSDPA Key Techniques – 16QAM

� HSDPA Modulation

�QPKS

�16QAM


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 Issue1

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