Wpo-01 Wcdma Radio Theory-53

WCDMA Radio Theory

ZTE University

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 Spectrum

Communication

Content

Radio Basics

3G Spectrum Planning

Principles of Spread Spectrum Communication

Duplex mode

TDD modeSame frequency between uplink and downlinkz Adaptable to any frequency

bandz Suitable for both

asymmetric and symmetric services between uplink and downlink

FDD modeFrequency pairing between uplink and downlinkz Paired frequency band

neededz Suitable for symmetric

services between uplink and downlink

TDD ( Time division duplexingSuch as TD-SCDMA)

D U D D D D DD

FDDFrequency division duplexingSuch as WCDMA and CDMA2000

D D D D D DD

U

9Multiple access technologies enable various users access public communication line but without interference.9Three methods are frequently used: FDMA, TDMA and CDMA

Multiple Access Technologies

Users are using Users are using different frequencydifferent frequency

Time

Frequency

FDMA

FDMA (Frequency Division Multiple Access)

FDMAz Traffic channels are assigned to different users at

different frequency band, such as TACS, AMPS.

Time

Frequency

TDMA

Users are using Users are using different time slotdifferent time slot

TDMA (Time Division Multiple Access)

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

Time

Frequency

CDMA

Code

Users are using different Users are using different orthogonal code sequenceorthogonal code sequence

CDMA (Code Division Multiple Access)

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

Freq. 1

Freq. 1

Code A

Code

B

Code

C

BS1

BS2

Code D

Code E

CDMA Application

Users are distinguished by code Self-interference system CDMA is a system subject to interference (GSM is a

system subject to frequency)

GSM900/1800: 3G (WCDMA):

Frequency Reuse

Wireless Transmission TechnologyRTT Requirements

Dataz 144 kbps High speed and drivingz 384 kbps Modest speed and walkingz 2 Mbps Low speed and indoor

Voicez 4.75Kb/s -- 12.2Kb/s

Information transmission at variable rate according to bandwidth requirements

Delay requirements of different business

3G services

Delay

Bit ErrorDifferent QOS requirements

3G services Categories Actual Service Delay (One-way) Bearer Speed

Voice

Contents

Radio Basics



IMT-2000 Spectrum Allocation

1850 1900 1950 2000 2050 2100 2150 2200

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

UMTSGSM 1800 DECT MSS

1885 MHz 2025 MHz

2010 MHz

IMT 2000

MSSUMTS

Japan MSSIMT 2000MSSIMT 2000PHS

IMT 2000

2110 MHz 2170 MHz

MSS MSS

TDDWLL

1

9

8

0

GSM1800 CDMA

1

9

6

0

1

9

2

0

1

9

4

5

China

1

8

6

5

1

8

6

5

1

8

7

0

1

8

8

5

1

8

9

0

1

9

1

0

1

9

3

0

1

9

4

5

1

9

6

5

1

9

7

0

1

9

7

5

FDDWLL

CDMA

FDDWLL

1850 1900 1950 2000 2050 2100 2150 2200 2250

ITU

1850 1900 1950 2000 2050 2100 2150 2200 2250

1880 MHz 1980 MHz

1885 MHz 2025 MHz

2010 MHz

IMT 2000

2170 MHz

IMT 20002110 MHz 2170 MHz

MSS MSS

China MSSMSS MSSFDDFDD

1920 MHz

TDD TDD

3G Spectrum Allocation in ChinaNov, 2002

3G Spectrum Allocation in China

60 MHz30 MHz

FDD TDD

100 MHz15MHz 40

MHz

155MHz

1785 18501755 1880 1920 1980 2010 2025 2110 2170 2200 2400

Satellite Empty Satellite

2300

3G Spectrum Planning in China

Main Operating Frequency Bandz FDD mode1920-1980 MHz / 2110-2170 MHzz TDD mode1880-1920MHz2010-2025 MHz

Supplementary Operating Frequency Bandz FDD mode1755-1785 MHz / 1850-1880 MHzz TDD mode2300-2400MHz

Frequency Band for Satellite Mobile Communication Systemz 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 - 1850 MHz, which are currently allocated to public mobile communication system are also allocated to expanded frequency bands of 3G public communication system, but frequency using mode remains the same for both uplink and downlink.

Contents

Radio Basics



Encoding Interleaving

Baseband Modulation Spectrum

Spreading

Scrambling Radio Frequency

Modulation

Radio Channel

Decoding Deinterleaving

Baseband Demodulation

Despreading Descrambling

Radio Frequency Demodulation

Transceiver Data Processing

Handset Data

Handset Data

No ECCBER

Principles of Channel Encoding

Channel Encodingz Channel encoding is to add redundancy information to

original data, and thus gain error correcting capabilityz Currently, convolution code and Turbo code are

mostly used.1/2, 1/3z Encoding increased invalid load and transmission

time.z Suitable to correct a small amount of non-continuous

error.

x1 x6 x11 x16 x21

x2 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 arrangement role, and reorder according to certain sequence.

FunctionReduce the effects by fast fading of the channel.

Input Output

Disadvantagesz Additional delay causedz In specific circumstance, several independent random

errors might intertwined to burst error.

Encode Interleave

DeinterleaveDecode

The Use of Channel Encoding and Interleaving

Interleaving Technology

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

Funtion Reduce the effects by fast fading of the channel. Advantages:

z Interleaving is to change the data flow transmission sequence, and randomize burst errors.

z Improve the effectiveness of error-correcting codes. Disadvantages

z 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 in accordance with different service requirements.

z In specific circumstance, several independent random errors might intertwined to burst error.


Radio Channel

Decoding Deinterleav

ing

Baseband Demodulati

onDespreading

Descrambling


Handset Data


Baseband Modulation

Spectrum Spreading

Scrambling

Radio Frequency Modulation

Handset Data

Definition of Spread Spectrum Communication

Spread SpectrumSS: Spread Spectrum) Communication is referred as SS Communication.

SS Communication: To modulate at sending terminal with spread spectrum code, and make the occupied frequency bandwidth of the signal is more larger than the essential bandwidth; while at the receiving terminal, same spread spectrum code will be used to demodulate and despread, thus to recover the information and data that been transferred.

Direct Sequence Spread Spectrum (DSSS)z CDMA uses a direct sequence spread spectrum, which is to

directly mix the signals that need to transfer with pseudo-random sequence code (spreading code) whose speed is much higher than information speed. This way, the spectrum bandwidth of the modulated signal becomes much bigger than the original one.

Frequency Hopping (FH) Time Hopping (TH)

Several Forms of CDMA

DS-CDMA:z Multiple users are taking the same frequency resource at exactly

the same time and same place; FH-CDMASingle user is taking a narrow spectrum bandwidth at

single moment; the occupied frequency changes over time according to certain rules, which was determined by the address code.

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

Spread Spectrum Communication is a technology to transmit signal after its spectrum was expanded.

Its theoretical foundation is Shannon theoremC=B*log2(1+S/N)

CChannel Capacity, Unit b/sBSignal BandwidthUnit HzSAverage Signal PowerUnit WNAverage Noise PowerUnit W

ConclusionWhen channel capacity C keeps the same, signal bandwidth B and S/N ratio can definitely be exchanged, which means, a satisfactory transmission quality can be gained by increasing transmission system bandwidth at a low S/N ratio.

Spread Spectrum Communication Basics

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

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

Direct Spread Spectrum Communication

Orthogonality of Code SequencesAccumulation of 0 indicates orthogonality

The Orthogonality of Code Sequences

WCDMA System Spreading Code (Channelization Code)

WCDMA spreading code is generated by Walsh function, which is called OVSF code (Orthogonal Variable Spreading Factor code), OVSF codes becomes zero when cross-correlating with each other, and they are completely orthogonal.

Walsh function is a non-sinusoidal but completely orthogonal function system, which can be constituted through recurrence relations of Hadamard matrix H. Because its possible values can only be +1 and -1 (or 0 and 1), thus makes it suitable to express and process digital signals.

Walsh function is of the ideal cross-correlation properties. In Walsh function, the cross-correlation function of each two is 0, which means they are orthogonal for each other.

SF = 1 SF = 2 SF = 4

C ch,1,0 = (1)

C ch,2,0 = (1,1)

C ch,2,1 = (1,-1)

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

C ch,4,1 = (1,1,-1,-1)

C ch,4,2 = (1,-1,1,-1)

C ch,4,3 = (1,-1,-1,1)

OVSF- Orthogonal variable spreading factor

OVSFOrthogonal variable spreading factor

Symbol Speed Spreading FactorChip Speed

SF 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

User data-1+1-1-1+1-1

SS code+1-1-1+1-1+1+1-1

SS signalUser dataSS code

Despread dataUser dataSS code

1

1

1

1

1

1

1

1

1

1

Despread

Spread spectrum

WCDMA Spread Spectrum Illustration

Input signal

Local PN code

Judge at the time when T=Ts

Despread output

Integration

0

Ts(*)dt

WCDMA Despread

Despread method

-1 1 -11-1 -11 1 -1 -1 11-1 1-1 1Despread-1 1 -11-1 -11 1

1 -1 1 -11 1 1 1

-4 40 0

Judge -1 1

1 -1 1 -1

-1 1 Spread

Integration

Example of Spread/Despread Process

Different users are using different spread spectrum code

S1xC1S1xC1

S2XC2S2XC2

WW

S1S1

S2S2

Spread

Despread(S1xC1)+(S2xC2)(S1xC1)+(S2xC2)

Air InterfaceAir Interface

[S1xC1+S2xC2]xC2=[S1xC1+S2xC2]xC2=S2S2

[S1xC1+S2xC2]xC1=[S1xC1+S2xC2]xC1=S1S1

NN

SS

Orthogonality of C1 and C2C1xC2=0

Example of Spread/Despread

Signals from other users

Eb/NoPGPG=Wc/RWc is chip rateR is information rate

Quality Factor of Spread Spectrum Eb/No

Eb =Signal Power

Bit Rate =SR

E / tB / t

= N0 =Noise PowerBandwidth =

NW

EbN0

=

SR

NW

=SR X

WN =

SN X

WR

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

fSf

f0Signal spectrum before spreading

Signal

Sf

ff0Signal spectrum after spreading

Signal

Sf

ff0Signal spectrum after despreading

SignalInterference noise

f

Sf

f0

Signal spectrum before despreading

SignalInterference noise

Signal Narrow-band interference Broad-band interference

SS Communication Illstration

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


Radio Channel


Baseband Modulation

Spectrum Spreading

Scrambling


Decoding Deinterleav

ing

Baseband Demodulation Despre

ading

Descrambling


Handset Data

Handset

Data

OVSF code

Scrambling

Data Bit

Chip after spreading

Introduction to Scrambling

Scrambling make user information pseudo-randomized, which raised information privacy

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

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

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 CDMA for distinguishing cells and users to conduct multiple access

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 CDMA for distinguishing cells and users to conduct multiple access

Scrambling in WCDMA system is a kind of pseudo-random sequence (PN code)

z 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.

Scrambling in WCDMA system is a kind of pseudo-random sequence (PN code)

z 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.

Functions of Uplink/Downlink Scrambling

Uplink scrambling contains 224 codes, which are used to distinguish different users in same cell.z There are long scrambling codes and short

scrambling codes, in which, short scrambling codes are used for multiple user detection.

Downlink scrambling contains 218-1 codes, which are used to distinguish different cells.z The frequently used scrambling codes are 01

8191made up of totally 512 collections, and each collection contains one primary scrambling code and 15 secondary scrambling codes.

z 512 primary scrambling codes make 64 scrambling code groups, and each group contains 8 primary scrambling codes.

Numbering Rule of Downlink Scrambling Code

Downlink scrambling codetotals 218-1 (0..262142)

No. 511 scrambling code group

81768177

8191

8176 : primary scrambling code8177 : secondary scrambling code8191 : secondary scrambling code

No. 510 scrambling group

81608161

8175


No. 504 scrambling group

80648065

8079



112113

127

8176: primary scrambling code8177: secondary scrambling code8191 : secondary scrambling code


1617

31



01

15


No.0 scrambling code cluster

No. 63 scrambling code cluster


Radio Channel


Baseband Modulation

Spectrum Spreading

Scrambling


Decoding Deinterleavi

ng

Baseband Demodulation

Despreading

Descrambling


Handset Data

Handset

Data

WCDMA Modulation

Uplink Modulation BPSK Downlink Modulation QPSK (16QAM modulation

was introduced in HSDPA stage)

Separation of real parts and imaginary parts

PulseForming

PulseForming

Serial-Parallel Switch

Serial-Parallel Switch

Downlink physicalchannel 1

Cch,SF,m

j

I+jQSdl,n

G1

Cch,SF,m

j

I+jQSdl,n

G2

Downlink physicalchannel 2 Gp

Gp

P-SCH

S-SCH

cos(wt)

-sin(wt)

Re(T)

Im(T)

Physical Channel Spread-Spectrum Modulation Process-Downlink

Separation of real parts and imaginary parts

PulseForming

PulseForming

cos(wt)

-sin(wt)

Sdpch,n

Re(S)

Im(S)

Cd,1 d

I

cc

Q

j

I+jQ

DPDCH1Cd,3 d

DPDCH3 Cd,5 dDPDCH5

Cd,2 dDPDCH2Cd,4 d

DPDCH4 Cd,6 dDPDCH6

ccCc c

DPCCH

Q

Physical Channel Spread-Spectrum Modulation Process-Uplink

Questions

1Channel, Multiple Access and Multiplexing 2 Functions of Encoding and Interleaving 3 Principles of Spread Spectrum 4 Realization of Spread Spectrum in WCDMA

WCDMA Radio TheoryObjectivesContentDuplex modeMultiple Access TechnologiesFDMA (Frequency Division Multiple Access)TDMA (Time Division Multiple Access)CDMA (Code Division Multiple Access)CDMA ApplicationFrequency ReuseWireless Transmission TechnologyRTT Requirements3G services 3G services ContentsIMT-2000 Spectrum Allocation3G Spectrum Allocation in ChinaNov, 20023G Spectrum Allocation in China3G Spectrum Planning in ChinaContentsTransceiver Data ProcessingChannel EncodingPrinciples of Channel EncodingInterleaving TechnologyThe Use of Channel Encoding and InterleavingInterleaving TechnologyTransceiver Data ProcessingDefinition of Spread Spectrum CommunicationSeveral Forms of CDMASpread Spectrum Communication BasicsDirect Spread Spectrum CommunicationThe Orthogonality of Code SequencesWCDMA System Spreading Code (Channelization Code)OVSF- Orthogonal variable spreading factorSpread Spectrum of WCDMA SystemWCDMA Spread Spectrum IllustrationWCDMA DespreadExample of Spread/Despread ProcessDifferent users are using different spread spectrum codeExample of Spread/DespreadQuality Factor of Spread Spectrum Eb/NoRelation between Eb/N0 and PGSS Communication IllstrationFeatures of SS CommunicationTransceiver Data ProcessingIntroduction to ScramblingScrambling in WCDMA SystemFunctions of Uplink/Downlink ScramblingNumbering Rule of Downlink Scrambling CodeTransceiver Data ProcessingWCDMA ModulationPhysical Channel Spread-Spectrum Modulation Process-DownlinkPhysical Channel Spread-Spectrum Modulation Process-UplinkQuestions

Wpo-01 Wcdma Radio Theory-53

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