Post on 04-Jun-2018
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WCDMA Wireless Principle
ZTE University
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Content
The Basic Principles of Wireless Communication Radio Propagation Characteristics
Spreading Technology
Channel Coding
Interleave Technology
Modulation
WCDMA Radio mechanism
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Multi-path characteristics of radio channel
Electromagnetic propagation:
--direct radiationreflectiondiffraction and scattering
Signal attenuation:
Path lossLoss of electromagnetic waves in large scope of the spreadreflects the trend of the received signal in the spreading
Slow fadingLoss because of being blocked by the building and hill in thepropagation path
Fast fadingElectromagnetic signals rapidly decline in a few dozenswavelength ranges
Description of Fast fading distribution
Rayleigh distributionnon line-ofsight(NLOS) transmission
Rician distributionline-ofsight(LOS) transmission
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Multi-Path Effects
eceiving signal
time
strength
0
sending signal
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Frequency of f -set caused by the mo vement of mobi le that
is Dopp ler effect
Sending signal Acceptingsignal
Interference
0dB
Sendingsignal
-25dB
Acceptingsignal
fading
0 +
Sendingsignal Acceptingsignal
delay
0 2 3 +
Sendingsignal Acceptingsignal
dithering
Characteristics of Radio Propagation
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Content
The Basic Principles of Wireless Communication Radio Propagation Characteristics
Spreading Technology
Channel Coding
Interleave Technology
Modulation
WCDMA Radio mechanism
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SHANON Formula
C = Blog2(1+S/N)
Spread Spectrum Principles
Where,C is capacity of channel, b/s
B is signal bandwidth, Hz
S is average power for signal, W
N is average power for noise, W
It is the basic principle and theory for spread spectrum
communications.
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Spread Spectrum Principles
1.25 MHz
30 KHz
Power is Spread Over a Larger Bandwidth
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radio channel
ReceiverTransmitter
Spreading
Despreading
Noise
Spread Spectrum Principles
User information bits are spread over a wide bandwidth by
multiplying high speed spread code(chip) Spread signal bandwidth W wider than original signal
bandwidth Rb
For WCDMA, W=3.84Mchip/sRb(voice)=12kbit/s
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f
Sf
f0
Before spreading
signal
Sf
ff0
After spreading
signal
Sf
ff0
After despreading
signal
White noise
f
Sf
f0
Before despreading
signal
White noise
signal interference White noise
Spread Spectrum Principles
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Spreading Mode
Direct sequence spread spectrumDS-SS Base band data is spread by multiplication of pseudo-noisesequence and base-band pulse, the pseudo-noise sequencegenerated 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 bypower detection accuracy
WCDMA uses DS-SS
Frequency hopping spread spectrumFH-SS
Data is transmitted in the random channel by the carrier frequencyhopping
Before FH again, data is transmitted using traditional narrowbandmodulation
No near-far effect
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DS-SS communication system
A technology of transmission after spreadingsignal spectrum.
FastSpreadingSequence
SlowInformation
Sent
TX
SlowInformat ionRecovered
RX
FastSpreadingSequence
WidebandSignal
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Spread Spectrum Principles
Many code channels are individually
spreadand then added together to
create a composite signal
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Unwanted Power from
Other Resoures
Spread Spectrum Principles
Any Code Channel can be extracted from the receivedcomposite signal by using the right orthogonal code
Energy for transmitting signal can be lower than
interference and noise
Processing Gain
BroadbandInterference
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Concept of orthogonal code
Orthogonal
the result of multiplying
and sum is 0
Code1 +1 -1 +1 +1 -1 +1 -1 -1
Code2 -1 +1 +1 -1 -1 +1 +1 -1
Mul -1 -1 +1 -1 +1 +1 -1 +1
Sum0
Orthogonal
Code1 +1 -1 +1 -1 -1 +1 -1 -1
Code2 +1 +1 -1 +1 -1 -1 +1 -1
Mul +1 -1 -1 -1 +1 -1 -1 +1
Sum -2
Non-orthogonal
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S1
S2
S1xC1
S2XC2
WSpreading
Despreading
(S1xC1)+(S2xC2)
Air Interface
[S1xC1+S2xC2]xC2
=S2
[S1xC1+S2xC2]xC1
=S1N
S
C1xC2=0,
C1,C2,orthogonal
Direct spread technique
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Spreading code =
1 -1 -1 1 -1 1 1 -1
( SF = 8 )
Symbol
Spreading
Despreading
1
-1
1
-1
1-1
1
-1
1-1
Data=010010
Spreading code
Spread signal= Datacode
Data =Spread signalSpreading code
Chip
Sketch map of Spreading and Despreading
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Characteristics of Spreading Communication
High anti-multi-path- interference capabilityAnti-sudden-pulse
High security
Lower transmitting power Easy to implement large-capacity Multiple Access
Communication
Occupy band wide
Complex realization
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Content
The Basic Principles of Wireless Communication Radio Propagation Characteristics
Spreading Technology
Channel Coding
Interleave Technology
Modulation
WCDMA Radio mechanism
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Purpose of Channel Coding
By adding redundant information in the originaldata stream, receivers can detect and correct the
error signal, and improve data transmission rates.
No correct coding: BER
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Principle of Channel Coding
Channel coding Error-correcting ability obtains by adding redundancy in the
original data
Convolutional coding and Turbo coding 1/21/3arewidely applied.
Increase noneffective load and transmission time
Suitable to correct few non-continuous errors
W C D M A
T U R B O
S P E A K
W W C C D D M M A AT T U U R R B B O O
S 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
Decoding
Encod ing
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Content
The Basic Principles of Wireless Communication Radio Propagation Characteristics
Spreading Technology
Channel Coding
Interleave Technology
Modulation
WCDMA Radio mechanism
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Principle of Interleave Technology
advantage
Interleave is to change the sequence of data to random the
unexpected 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 x1 x25
ata inputA = (x1 x2 x3 x4 x5 x25)
Data outputA= (x1 x6 x11 x16 x25)
e.g.
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Encoding and Interleaving
W C D M A
T U R B O
S P E A K
W W C C D D M M A A
T T U U R R B B O O
S S P P E E A A K K
W T S W T S
C U P C U P
D R E D R E
M B A M B AA O K A O K
W ? ?C D D M M A ?T ? ?U R ??B O O
S ? ?P ?E A A K K
Encoding Interleaving
W T S ? ? ?
? ? ?C U P
D R ?D ?E
M ?A M B A
A O K ? O K
DeinterleavingDecoding
Encod ing + Inter leaving can c orrect bo th
cont inuo us and non -cont inuo us errors
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Content
The Basic Principles of Wireless Communication Radio Propagation Characteristics
Spreading Technology
Channel Coding
Interleave Technology
Modulation
WCDMA Radio mechanism
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Principle of Modulation
Definition Modulation is the process where the amplitude,
frequency, or phase of an electronic or optical signal
carrier is changed in order to transmit information.
Using symbol stand for one or more bits to improvecommunication effectiveness
Classification
Analog Modulation
Digital Modulation
Symbolbi tModulat ion
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Analog Modulation
The purpose of analog modulation is to impressan information-bearing analog waveform onto a
carrier for transmission.
Common analog modulation methods include:
Amplitude modulation (AM) Frequency modulation (FM)
Phase modulation (PM)
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Digital Modulation
The purpose of digital modulation is to convert aninformation-bearing discrete-time symbol
sequence into a continuous-time waveform
(perhaps impressed on a carrier).
Basic analog modulation methods include Amplitude shift Keying (ASK)
Frequency shift Keying (FSK)
Phase shift Keying (PSK)
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WCDMA Data transmission Procedure
RF ReceivingDemodulationDespreading
Decoding &
De-inteleavingUE Data
UE Data Spreading
RF Transmitting
Modulation
Baseband
demodulation
Baseband
modulation
Encoding &
Interleaving
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Content
The Basic Principles of Wireless Communication WCDMA Radio mechanism
WCDMA Data transmission Procedure
Channel Coding of WCDMA Spreading Technology of WCDMA
Modulation of WCDMA
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Convolutional Code
Characteristics Mainly used in the voice channel and control signal
channel
Coding rate : 1/2 & 1/3
Channel bit error rate is 10-3 magnitude Easy decoding
Short delay
Suitable for realtime service
e.g. speech and video service.
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Turbo Code
Characteristics Used in Data service channel
Code Rate is 1/3
Channel bit error rate is 10-6 magnitude
Can be implemented in the transmission for large blockand long delay services
Complex decoding, needs cycle iterative calculation
Very suitable for non-realtime package service which is
BER sensitive & delay insensitive e.g. WWW, FTP, E-mail , multimedia transmission .
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Content
The Basic Principles of Wireless Communication WCDMA Radio mechanism
WCDMA Data transmission Procedure
Channel Coding of WCDMA
Spreading Technology of WCDMA
Modulation of WCDMA
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Symbol rate SF = Chip rate=3.84Mcps
For WCDMASF of uplink channelization code4~256
SF of downlink channelization code: 4~512
OVSF: Orthogonal Variable Spreading Factor
OVSF Code Scrambling Code
Data Spread Data
Spreading Process of WCDMA
Symbol Chip
3.84Mcps
3.84Mcps
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Channelization Code
Adopt OVSF code Definition: Cch,SF,k, describe channelization code, where
SF : spread factork : code number, 0 < k
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Scrambling Code
WCDMA Scrambling code is pseudo randombinary sequence (PN code) It has similar noise array character, seemingly random
but with regularity.
Can make the user data further random , strengthenedby scrambling a code to keep secret the user data, atthe same time easy to carry out multiple accesscommunication.
WCDMA scrambling code is generated from Gold
sequence Gold sequence has excellent self-correlation.
Cross-correlation is very week between two codes.
It is used to identify cell and user for multiple access.
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Characteristic of Scrambling code
There are 224 Uplink Scrambling Codes, they areused to distinguish different users in one cell.
There are 218-1 Downlink Scrambling Codes,
used to distinguish different cells
Scrambling codes usually used are the first 8192 codes,which are code 018191. They are dividedinto 512 aggregationseach aggregation has 1 primaryscrambling code (PSC) and 15 secondary scrambling
codes (SSC). The 512 primary scrambling codes are divided further
into 64 primary scrambling code groups , with 8 primary
scrambling codes in each group.
N b i l f D li k S bli
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Numbering rule for Downlink Scrambling
Codes
218-1 Downlink Scrambling Codes in all0..262142)
No. 511 Scrambling Code
Group
8176
8177
8191
8176PSC
8177SSC
8191SSC
No. 510 Scrambling Code
Group
8160
8161
8175
8160
8161
8175
No. 504 Scrambling Code
Group
8064
8065
8079
8064
8065
8079
No. 7 Scrambling Code
Group
112
113
127
8176PSC
8177
8191
No. 1 Scrambling Code
Group
16
17
31
16PSC
17SSC
31SSC
No. 0 Scrambling Code
Group
01
15
0PSC1SSC
15SSC
No.63 Primary Scrambling ode Group
No.0 Primary Scrambling ode Group
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Code Functions
Channelization code ---- for separation of physicalchannels in the uplink and separation of users in
the downlink
Scrambling code ---- for separation ofusers/terminals in the uplink and cells/sectors in
the downlink.
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Despreading procedure
Method of despreading
Inputsignal
Local PN code
When T=Ts, judge
Outputafterdespreading
integral
0
Ts(*)dt
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Content
The Basic Principles of Wireless Communication WCDMA Radio mechanism
WCDMA Data transmission Procedure
Channel Coding of WCDMA
Spreading Technology of WCDMA
Modulation of WCDMA
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Modulation Methods in WCDMA
BPSK (Binary Phase Shift Keying) in Uplink channles
QPSK (Quadrature Phase Shift Keying) in Downlink channels
16QAM (16-state Quadrature Amplitude Modulation) in HSDPA
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summary
Principle of WCDMA
All users are simultaneously transmitted in the same frequency band
Users interfere with each other
Adjacent cells use the same frequency
Cells, users (terminals), and physical channels are separated by codes
Channel coding
Convolutional code Turbo code
Codes
Channelization code
Scrambling code
Modulation BPSK
QPSK
16QAM
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