1.Wpo-02 Wcdma Radio Theory-53

8/2/2019 1.Wpo-02 Wcdma Radio Theory-53

1/43

WCDMA Radio Theory

ZTE University


2/43

Objectives

At the end of this course, you will be able to:

Master basic radio theory

Understand IMT-2000 spectrum planning

Master principles of Spread SpectrumCommunication


3/43

Content

Radio Basics

3G Spectrum Planning

Principles of Spread Spectrum Communication


4/43

Duplex mode

TDD modeSame frequencybetween uplink and downlink

Adaptable to any frequencyband

Suitable for bothasymmetric and symmetric

services between uplinkand downlink

FDD modeFrequencypairing between uplink anddownlink

Paired frequency bandneeded

Suitable for symmetricservices between uplinkand downlink

TDD ( Time division duplexing

Such as TD-SCDMA)

D U D D D D DD

FDDFrequency division duplexing

Such as WCDMA and CDMA2000

D D D D D DD

U


5/43

Multiple access technologies enable various users access public

communication line but without interference.

Three methods are frequently used: FDMA, TDMA and CDMA

Multiple Access Technologies


6/43

FDMA

Traffic channels are assigned to different users at differentfrequency band, such as TACS, AMPS.

Aim to increase capacity, must partition the frequency spectrummore and more tiny. So the requirement of decode SIR is higherand higher.

Low resource utilization ratio, can not support large capacitysystem.

Users are usingdifferent frequency

Time

Frequency

FDMA

FDMA (Frequency Division Multiple Access)


7/43

Time

Frequency

TDMA

Users are using

different time slot

TDMA (Time Division Multiple Access)

TDMATraffic channels are assigned to different users at different time, suchas GSM, DAMPS.

The disadvantage are interference between different time slot andchannel synchronization.


8/43

Time

Frequency

CDMA

Code

Users are using differentorthogonal code sequence

CDMA (Code Division Multiple Access)

CDMATraffic channels are assigned to users at same time,same frequency band, but with different code.


9/43

Freq. 1

Freq. 1

BS1

BS2

Code D

CDMA Application

Users are distinguished by code

Self-interference system

CDMA is a system subject to interference (GSM is asystem subject to frequency)

UL limited by interferenceDL limited by power, CE, code resource


10/43

GSM900/1800: 3G (WCDMA):

Frequency Reuse


11/43

Wireless Transmission TechnologyRTTRequirements

Data 144 kbps High speed and driving

384 kbps Modest speed and walking

2 Mbps Low speed and indoor

Voice 4.75Kb/s -- 12.2Kb/s

Information transmission at variable rate accordingto bandwidth requirements

Delay requirements of different business


12/43

3G services

Delay

Bit Error

Different QOS requirements


13/43

3G services

Categories Actual Service Delay (One-way) Bearer Speed

Real-time

Voice


14/43

Contents

Radio Basics




15/43

3G Spectrum Planning in China

Main Operating Frequency Band

FDD mode1920-1980 MHz / 2110-2170 MHz

TDD mode1880-1920MHz2010-2025 MHz

Supplementary Operating Frequency Band

FDD mode1755-1785 MHz / 1850-1880 MHz

TDD mode2300-2400MHz

Frequency Band for Satellite Mobile Communication System

1980-2010 MHz / 2170-2200 MHz

The frequency bands, 825 - 835 MHz / 870 - 880 MHz, 885 -

915 MHz / 930 - 960 MHz and 1710 - 1755 MHz / 1805 - 1850MHz, which are currently allocated to public mobilecommunication system are also allocated to expandedfrequency bands of 3G public communication system, butfrequency using mode remains the same for both uplink anddownlink.


16/43

Contents

Radio Basics




17/43

EncodingInterleaving

BasebandModulation Spectrum

Spreading

Scrambling Radio Frequency

Modulation

Radio Channel

DecodingDeinterleaving

Baseband

Demodulation

Desprea

dingDescrambling

Radio Frequency

Demodulation

Transceiver Data Processing

Handset Data

Handset Data


18/43

No ECCBER


19/43

Principles of Channel Encoding

Channel Encoding Channel encoding is to add redundancy information to

original data, and thus gain error correcting capability

Currently, convolution code and Turbo code are

mostly used.1/2, 1/3

Encoding increased invalid load and transmissiontime.

Suitable to correct a small amount of non-continuouserror.


20/43

x1 x6 x11 x16 x21x2 x7 x22

x3 x8 x23

x4 x9 x24

x5 x10 x25

A = (x1 x2 x3 x4 x5 x25) A= (x1 x6 x11 x16 x25)

Interleaving Technology

InterleavingDisrupt the original data arrangementrole, and reorder according to certain sequence.

FunctionReduce the effects by fast fading of thechannel.

Input Output

Disadvantages Additional delay caused

In specific circumstance, several independent randomerrors might intertwined to burst error.


21/43

EncodeInterleave

DeinterleaveDecode

The Use of Channel Encoding andInterleaving


22/43

Interleaving Technology

Interleaving Disrupt the original data arrangement role, andreorder according to certain sequence.

Funtion Reduce the effects by fast fading of the channel.

Advantages:

Interleaving is to change the data flow transmission

sequence, and randomize burst errors. Improve the effectiveness of error-correcting codes.

Disadvantages

Due to the transmission sequence change of data flow,error correcting can only be performed after the whole data

package is received, which increased delay time.Therefore, different interleaving depth should be chosen inaccordance with different service requirements.

In specific circumstance, several independent randomerrors might intertwined to burst error.


23/43


Radio

Channel

DecodingDeinterleav

ing

BasebandDemodulati

on

Despre

ading

Descrambli

ng

Radio Frequency

Demodulation

Handset

Data


BasebandModulation

SpectrumSpreading

Scrambling

RadioFrequencyModulation

HandsetData


24/43

Several Forms of CDMA

DS-CDMA:

Multiple users are taking the same frequency resource at exactlythe same time and same place;

FH-CDMASingle user is taking a narrow spectrum bandwidth atsingle moment; the occupied frequency changes over time accordingto certain rules, which was determined by the address code.

TH-CDMASingle user is taking a wide spectrum time to time; theoccupied time changes according to certain rules, which wasdetermined by the address code.


25/43

Spread Spectrum Communication is a technology to transmit

signal after its spectrum was expanded. Its theoretical foundation is Shannon theorem

C=B*log2(1+S/N)

C

Channel Capacity, Unit b/sBSignal BandwidthUnit Hz

SAverage Signal PowerUnit W

NAverage Noise PowerUnit W

ConclusionWhen channel capacity C keeps the same, signalbandwidth B and S/N ratio can definitely be exchanged, whichmeans, a satisfactory transmission quality can be gained byincreasing transmission system bandwidth at a low S/N ratio.

Spread Spectrum Communication Basics


26/43

High speed spread-spectrum sequences

Low speed signal

TX

Demodulated signal

RX

High speed spread-spectrum sequences

Spread-spectrum signal

Speed of spread-spectrum code3.84Mc/sSpread-spectrum code OVSF code

Direct Spread Spectrum Communication


27/43

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)

C

ch,4,1

= (1,1,-1,-1)

Cch,4,2

= (1,-1,1,-1)

Cch,4,3

= (1,-1,-1,1)

OVSF- Orthogonal variable spreading factor

OVSF

Orthogonal variable spreading factor


28/43

Symbol Speed SpreadingFactorChip SpeedSF for uplink channel code4~256

SF for downlink channel code4~512

OVSF Code Scrambling

Code

Data

Symbol

Spread

Spectrum

Chip

Spread Spectrum of WCDMA System


29/43

S1xC1

S2XC2

W

S1

S2

Spread

Despread

(S1xC1)+(S2xC2)

Air Interface

[S1xC1+S2xC2]xC2=S2

[S1xC1+S2xC2]xC1=S1

N

S

Orthogonality of C1

and C2C1xC2=0

Example of Spread/Despread


30/43

Signals from other users

Eb/NoPGPG=Wc/RWc is chip rate

R is informationrate

Quality Factor of Spread Spectrum Eb/No


31/43

Eb =Signal Power

Bit Rate=

S

R

E / t

B / t= N0 =

Noise Power

Bandwidth=

N

W

EbN0

=

S

R

N

W

=S

R XW

N=

S

N XW

R

Signal to Noise

Processing Gain

The more the expansion multiples, the higher the

processing gain, the stronger the anti-jamming capability

Relation between Eb/N0 and PG


32/43

f

Sf

f0

Signal spectrum before spreading

Signal

Sf

ff0

Signal spectrum after spreading

Signal

Sf

ff0

Signal spectrum after despreading

Signal

Interference noise

f

Sf

f0

Signal spectrum before despreading

Signal

Interference noise

Signal Narrow-band interference Broad-band interference

SS Communication Illustration


33/43

Features of SS Communication

Strong anti-jamming capability High privacy

Low emission power

Easy practice of larger-capacity and multi-access

communication Broad frequency band


34/43


Radio

Channel


BasebandModulation

SpectrumSpreading

Scrambling


DecodingDeinterleav

ing

Baseband

DemodulationDespreading

Descrambli

ng

Radio Frequency

Demodulation

HandsetData

Hands

etData


35/43

OVSF code Scrambling

Data

Bit

Chip after

spreading

Introduction to Scrambling

Scrambling make user information pseudo-randomized, whichraised information privacy

WCDMA scrambling is a Gold code sequence generated fromthe superimposition of two m sequences (the maximum-lengthlinear shift register sequences)

Scrambling is made up of uplink scrambling and downlinkscrambling, with different functions respectively


36/43

Scrambling in WCDMA System

WCDMA Scrambling code is Sequence generated by GOLDGold sequence is of wonderful auto-correlating property, and its

sub-sequences are of small correlation, which is used in CDMAfor distinguishing cells and users to conduct multiple access

Scrambling in WCDMA system is a kind of pseudo-random

sequence (PN code)

It has the properties similar to noise sequence, apparently

random but actually a binary sequence with regular

periodic manner. By scrambling, user data are further

randomized, which strengthened privacy, and meanwhile,made multiple access communication more convenient.


37/43

Functions of Uplink/Downlink Scrambling

Uplink scrambling contains 2

24

codes, which areused to distinguish different users in same cell.

There are long scrambling codes and shortscrambling codes, in which, short scrambling codesare used for multiple user detection.

Downlink scrambling contains 218-1 codes, whichare used to distinguish different cells.

The frequently used scrambling codes are 018191made up of totally 512 collections, and each

collection contains one primary scrambling code and15 secondary scrambling codes.

512 primary scrambling codes make 64 scramblingcode groups, and each group contains 8 primaryscrambling codes.


38/43


Radio

Channel


BasebandModulation

Spectrum

Spreading

Scrambling


Decoding

Deinterleaving

BasebandDemodulation

Despreading

Descrambli

ng

Radio Frequency

Demodulation

HandsetData

Hands

etData


39/43

WCDMA Modulation

Uplink Modulation BPSK

Downlink Modulation QPSK (16QAM modulationwas introduced in HSDPA stage)

Ph i l Ch l S d S


40/43

Separation of real parts and imaginary parts

PulseForming

Pulse

Forming

Serial-Parallel Switch

Serial-Parallel Switch

Downlink physical

channel 1

Cch,SF,m

j

I+jQSdl,n

G1

Cch,SF,m

j

I+jQ

Sdl,n

G2

Downlink physicalchannel 2

Gp

Gp

P-SCH

S-SCH

cos(wt)

-sin(wt)

Re(T)

Im(T)

Physical Channel Spread-SpectrumModulation Process-Downlink

Ph i l Ch l S d S


41/43

Separation of real parts and imaginary parts

Pulse

Forming

Pulse

Forming

cos(wt)

-sin(wt)

Sdpch,n

Re(S)

Im(S)

Cd,1 d

I

cc

Q

j

I+jQ

DPDCH1Cd,3 d

DPDCH3Cd,5 d

DPDCH5

Cd,2 dDPDCH2

Cd,4 dDPDCH4

Cd,6 dDPDCH6

ccCc c

DPCCH

Q

Physical Channel Spread-SpectrumModulation Process-Uplink


42/43

Questions

1Channel, Multiple Access and Multiplexing

2 Functions of Encoding and Interleaving

3 Principles of Spread Spectrum

4 Realization of Spread Spectrum in WCDMA


43/43

1.Wpo-02 Wcdma Radio Theory-53

Documents

Transcript of 1.Wpo-02 Wcdma Radio Theory-53