WCDMA Radio Teoria

WCDMA Radio Theory

ZTE University

TD&W&PCS BSS Course Team

Course Objectives

At the end of this course, you will be able to: Master channel encoding of WCDMA Master spread spectrum principle of WCDMA Master modulation of WCDMA

Content

The basic principles of wireless communication

Radio Propagation CharacteristicsRadio Propagation Characteristics

Multi AccessMulti Access

Spread spSpread spectrum ectrum TechnologyTechnology

Channel CodingChannel Coding

InterleavInterleavee Technology Technology

WCDMA wireless technology

Characteristic of Radio Propagation Electromagnetic propagation: direct

radiation reflection diffraction and scattering

Signal attenuation: Path loss Loss of electromagnetic waves in large scope of the

spread reflects the trend of the received signal in the spreading

Slow fading Loss because of being blocked by the building and hill in

the propagation path

Fast fading Electromagnetic signals rapidly decline in a few dozens

wavelength ranges

Description of Fast fading distribution Rayleigh distribution non line-of sight transmission

Rice distribution line-of sight transmission

Radio propagation charactistics

Frequency Frequency off-setoff-set caused by the movement of mobile caused by the movement of mobile that is Doppler effectthat is Doppler effect

Sending signal Accepting signal

Interference Interference

0dB

Sending signal

-25dB

Accepting signal

fadingfading

0 + Sending signal Accepting signal

delaydelay

0 2 3 + Sending signal Accepting signal

ditheringdithering

Characteristics of Radio Propagation


Multi-Path Effects

receiving signalreceiving signal

timetime

strengthstrength

00

sending signalsending signal


Content




SpreadSpread spectrum spectrum Technology Technology


Interleave TechnologyInterleave Technology


Freque

ncyTime

Power

Freque

ncyTime

Power

Freque

ncyTime

Power

FDMA

TDMA

CDMA

Frequency division multiple access technology Channels in different frequency are allocated to different users, e.g. TACS AMPS

Time division multiple access technologychannels in different time are allocated to different users, e.g. GSM DAMPS

Code division multiple access technologyUsers distinguished by scramble code, e.g. CDMA

Multiple Access

Multiple access

Content








Principle of Spreading spectrum

A technology of transmission technology after spreading

frequency of signal.

Theoretical Basis: Shannon theory C=Wlog2(1+S/N)

FastSpreadingSequence

SlowInformation

Sent

TX

SlowInformationRecovered

RX

FastSpreadingSequence

WidebandSignal

Spreading technology

fS f

f0Before spreading

signal

S f

ff0After spreading

signal

S f

ff0After despreading

signalWhite noise

f

S f

f0

Before despreading

signalWhite noise

signal interference White noise

Sketch Map of Spreading


Spreading Mode

Direct sequence spread DS SS Base band data is spreaded by multiplication of pseudo-noise

sequence and base-band pulse, the pseudo-noise sequence generated by the pseudo-noise generator

BER subject to Multiple Access Interference and near-far effect Power control can overcome the near-far effect, but it is limited by

power detection accuracyWCDMA uses DS-SS

Frequency hopping spread FH-SS Data is transmitted in the random channel by the carrier frequency

hopping Before FH again, data is transmitted using traditional narrowband

modulation No near-far effect


Characteristics of Spreading Communication

High anti-multi-path- interference capability

High security

Lower transmitting power

Easy to implement large-capacity Multiple Access

Communication

Occupy band wide

Complex realization


Content




Spread spectrum TechnologySpread spectrum Technology




Purpose of Channel Coding

purpose:

By adding redundant information in the original data stream,

receivers can detect and correct the error signal, and

improve data transmission rates.

Error-correcting ability obtains by adding redundancy in the

original data

Channel coding

W C D M AT U R B OS P E A K

W W C C D D M M A AT T U U R R B B O OS S P P E E A A K K

W C C D D M M A A

T T U R R B B O O

S S P P E E A K K

Principle of Channel Coding

Channel coding

Convolutional coding and Turbo coding 1/2 1/3 are widely applied.

Increase redundancy and transmission time

Suitable to correct few non-continuous errors

Channel coding

No correct coding: BER

Content








Principle of Interleave Technology advantage

Interleave is to change the sequence of data to discretize the burst

continuous errors

Advance the correcting validity

disadvantage Increase the processing delay

Especially, Several independent random errors may intertwined for

the unexpected error .

x1 x6 x11 x16 x21x2 x7 x22x3 x8 x23x4 x9 x24x5 x10 x25

Data input A = (x1 x2 x3 x4 x5 x25)

Data output A= (x1 x6 x11 x16 x25)

e.g.

Interleaving technology

Encoding and Interleaving

W C D M AT U R B OS P E A K

W W C C D D M M A AT T U U R R B B O OS S P P E E A A K K

W T S W T SC U P C U PD R E D R EM B A M B AA O K A O K

W ? ? C D D M M A AT ? ? U R R B B O O

S ? ? P E E A A K K

Encoding Interleaving

W T S ? ? ?? ? ? C U PD R E D R EM B A M B AA O K A O K

DeinterleavingDecoding

Interleaving technology

Content



UE Data Encoding & InterleavingSpreading&Scrambling

RF Transmission

RF ReceivingDemodulationDespreading&Descrambling

Decoding & Deinteleaving

UE Data

Data transmission Procedure

Modulation

Baseband

demodulation


Convolutional Code

Mainly used in the voice channel and control signal channel

Coding rate is and 1/3

Output 0 G0 = 557 (octal)

Input D D D D D D D D



Rate 1/3 convolutional coder


Characteristics of Convolutional code

Easy decode

Short delay

Generally use the Viterbi Algorithm

Channel bit error rate is 10 3 magnitude

Suitable to realtime service

e.g. speech and video service.


Turbo Code Used in Data service channel

Code Rate is 1/3

Can be implemented in the transmission for large block and long delay services

Turbo coding structure is based on two or more weak error control code combinations. Turbo coding structure is based on two or more weak error control code combinations.

The information bits are interleaved in the two Encoder, and generate two information The information bits are interleaved in the two Encoder, and generate two information

flow. At last, this information can be multiplexed and puncturedflow. At last, this information can be multiplexed and punctured

Decoding needs cycle iterative calculationDecoding needs cycle iterative calculation

InterleaverEncoder 1

Encoder 2

Mul

tiple

xinputoutput


Characteristics of Turbo Codes

Complex decoding

Use the LOG-MAP arithmetic

Channel bit error rate is 10 6 magnitude

Very suitable to non-realtime package service which is BER

sensitive & delay insensitive , e.g. WWW, FTP, E_mail , multimedia transmission .


Interleaving Technology of WCDMA

Intra-frame interleave

Bits transform in the internal frame

Inter-frame interleave

Data transform among the frames

Intra-Turbo codes interleave

Complex nesting of intra-frame and inter-frame interleave


UE Data Encoding & InterleavingSpreading&Scrambling Modulation

RF Transmission



UE Data



Symbol rate SF = 3.84McpsSymbol rate SF = 3.84McpsWCDMAWCDMA SF of uplink channelized codeSF of uplink channelized code 4~2564~256

SF of downlink channelized code:4~512SF of downlink channelized code:4~512OVSF: Orthogonal Variable Spreading Factor OVSF: Orthogonal Variable Spreading Factor

OVSF Code Scramble Code

Data bitChip after Spreadin

g

Spreading of WCDMA


Despreading of WCDMA

Method of despreading

Input signal

Local PN code

When T=Ts, judge

Output after despreading

integral

0

Ts(*)dt


Symbol

Spreading

Despreading

1-1

1-1

1

-1

1-1

1-1

Data = 010010

Spreading code

Spread signal= Data code

Spreading code =1 -1 -1 1 -1 1 1 -1 ( SF = 8 )

Data = Spread signal Spread code

Chip

Spreading and Despreading


Concept of orthogonal code

Orthogonal

the result of multiplying and sum is 0-1-1+1-1+1+1-1+1Mul

0Sum

Orthogonal

-1+1+1-1-1+1+1-1Code2

+1-1+1+1-1+1-1-1Code1

+1-1-1-1+1-1-1+1Mul

-2Sum

Non-orthogonal

+1+1-1+1-1-1+1-1Code2

+1-1+1-1-1+1-1-1Code1


Code Resource Allocation

Channelization code:

Channelization codes are based on the orthogonal variable

spreading factor (OVSF) technology. Transmission from a

single source are separated by channelization codes.

Scrambling code:

Scrambling codes are used after spreading, which will not

change the signal bandwidth. They are only used to

differentiate different UEs or Node Bs.

In WCDMA, code resources are mainly divided into channelization codes and scrambling codes.


Channelization Code

Adopt OVSF code C ch,SF,k describe channelization code,

SF spread factor

k code number, 0 < k

SF=8

SF=32

SF=16

Characteristic of channelization code

Premise of code allocation:ensure not occupied for the code in the root direction and

downwards subtree

Result of code allocation:block all low rate SC in subtree and high rate in upwards

root direction


Example

SF=64

SF=32

SF=16

SF= 8

0 1 2 3 4 5 6 7` ` ` `

` `0 1 2 3

` 0 1

0

SF=64

SF=32

SF=16

SF= 8

0 1 2 3 4 5 6 7` ` ` `

` `0 1 2 3

` 0 1

0

0 1 2 3 4 5 6 7` ` ` `

` `0 1 2 3

` 0 1

0

0 1 2 3 4 5 6 7` ` ` `

` `0 1 2 3

` 0 1

0

(a) (b)

(c) (d)

`

Idle

Allocated

Blocked


OVSF Code Scramble Code

Data bitChip after Spreadin

g

Scrambling code

In addition to spreading, part of the process in the transmitter is the

scrambling operation. This is needed to separate terminals or base

stations from each other. Scrambling is used on top of spreading, so it

does not change the signal bandwidth but only makes the signals from

different sources separable from each other.


Scrambling code of WCDMA

WCDMA scrambling code is generated from Gold sequence Gold has excellent self_correlation, Mutual_correlation is very small between subsection serial. It is used to identify cell and user for multiple address.

WCDMA Scrambling code is pseudo random binary sequence (PN code)

It has similar noise array character , is that one kind is seemingly random but cyclicity binary system array. Can make the user data a further randomization , strengthened by scrambling a code to keep secret the function, at the same time easy to carry out multiple access communication.


Characteristic of Scrambling code

There are 224 Uplink Scrambling Codes, they are used to distinguish

different users in one cell.

Uplink Scrambling codes include long scrambling codes and short

scrambling codes. The Short Scrambling codes are used for multi-user

detecting

There are 218-1 Downlink Scrambling Codes, used to distinguish different

cells Scrambling codes in common use are 0 1 8191 they are divided

into 512 aggregations each aggregation has 1primary scrambling code and

15 secondary scrambling codes.

512 primary scrambling codes can be divided into 64 scrambling code groups

,there is 8 primary scrambling in each group.


UE Data Encoding & InterleavingSpreading&Scrambling Modulation

RF Transmission



UE Data



WCDMA Modulation

UL: BPSK

DL:QPSK HSDPA introduce 16QAM


Exercise multiple access technolog include ?

pls describe the channel coding purpose and interleaving technology purpose.

WCDMA adopts( ) and( )channel coding technology. the coding rate is( ) ( )

the spreading code of WCDMA is ( ), the sf of ul channelize code is ( ), and the dl is ( )

There are ( ) Uplink Scrambling Codes, they are used to distinguish different( ) in one cell.

There are ( ) Downlink Scrambling Codes, used to distinguish( )

WCDMA modulation technology include ( ) and ( )

WCDMA Radio Teoria

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Transcript of WCDMA Radio Teoria