The document describes the fundamentals of WCDMA radio access networks. It covers topics such as wireless signal propagation, CDMA principles including spreading and despreading, channel coding, and modulation techniques used in WCDMA like QPSK. It also discusses concepts like channelization codes, scrambling codes and the use of a RAKE receiver to mitigate multipath fading in WCDMA systems.

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OWA200002 WCDMA
RAN Fundamental
ISSUE1.1
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Upon completion of this course, you will be able to:
[ Describe feature of wireless propagation
[ Outline the advantage of CDMA principle
[ Characterize code sequence
[ Outline the fundamentals of RAN

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Chapter 1 CDMA PrincipleChapter 1 CDMA Principle
Chapter 2 WCDMA FundamentalChapter 2 WCDMA Fundamental
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Wireless Propagation
Time
Received
signal
Transmitted
signal
Transmission Loss:
path loss
multi-path fading

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Propagation Effect
-40
-35
-30
-25
-20
-15
-10
-5
0
dB
Transmitter
Receiver
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Fading Categories

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Multiple Access Technology and Duplex Technology
l Multiple access technology
[ Time division multiple access (TDMA)
[ Frequency division multiple access (FDMA)
[ Code division multiple access (CDMA)
l Duplex technology
[ Time division duplex (TDD)
[ Frequency division duplex (FDD)
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Multiple Access Technology
frequency
time
power
FDMA
frequencytime
power
TDMA
power
time
CDMA
frequency

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Duplex Technology
FDD
Time
Frequency
Power
UL DL
UMTS USER 1
UMTS USER 2
Time
Frequency
Power
TDD
UMTS USER 2
UMTS USER 1
DL
UL
DL
DL
UL
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Chapter 1 CDMA PrincipleChapter 1 CDMA Principle
Chapter 2 WCDMA FundamentalChapter 2 WCDMA Fundamental

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Processing Procedure of WCDMA System
Source
coding
Channel
coding
Spreading Modulation
Source
decoding
Channel
decoding
Despreading Demodulation
Radio channelRadio channelRadio channel
Transmission
Reception
Coding of
information using
the smallest
amount of bits
possible
Adding
redundancy
to protect the
information
Transmission
of a physical
signal
Spreading
chip modulated signal
bit symbol
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Terms
l Bit, Symbol, Chip
[ Bit : data after source coding
[ Symbol: data after channel coding and interleaving
[ Chip: data after spreading
l Process Gain: 10log (chip rate/ bit rate)
[ 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

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WCDMA Source Coding
lAMR (Adaptive Multi-Rate) voice coding
[Multi-rate
− 8 kinds of coding rates
[Adaptation:
− when cell load increases, the system will
decrease speech rate of part of
subscribers automatically so as to
support more subscribers
5.15AMR_5.15
1.8AMR_SID
4.75AMR_4.75
5.9AMR_5.90
6.7 (PDC EFR)AMR_6.70
7.4 (TDMA EFR)AMR_7.40
7.95AMR_7.95
10.2AMR_10.20
12.2 (GSM EFR)AMR_12.20
Bit rate （kbps）CODEC
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WCDMA Channel Coding
l Purpose
[ Enhance the correlation among symbols so as to recover the signal
when interference occurs
l Types
[ Convolutional coding produces ‘redundant’ copies of bits
− Provides better error correction at receiving end
− Increases the delay
[ Turbo Coding

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WCDMA Interleaving
















1110
1.........
............
...000
0100
0 0 1 0 0 0 0 . . . 1 0 1 1 1
















1110
1.........
............
...000
0010
0 0 … 0 1 0 … 1 0 0 … 1 0 … 1 1
Inter-column
permutation
Output bits
Input bits
Interleaving periods:
10, 20, 40, or 80 ms
l Interleaving ‘spreads out’ consecutive bits in time
l Reduces the probability of losing consecutive bits
[ Convolutional encoding is sensitive to consecutive bit loss
l Trades delay time for data protection
[ Longer interleaving periods have better data protection with more delay
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Correlation
l Correlation is a measure of similarity of between any two arbitrary signals
l Auto Correlation is related to the multi-path interference characteristic
l Cross Correlation is related to the multi-user interference characteristic
Time delay

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Channelization Code – OVSF Code
l OVSF Code: Orthogonal Variable Spreading Factor Code
l SF = chip rate / bit rate
[High data rates: low SF
[Low data rates: high SF
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)
SF = 8 to 512
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Purpose of Channelization Code
l For uplink, Channelization code ( OVSF code ) is used to separate
different physical channels of one connection
l For downlink, Channelization code ( OVSF code ) is used to separate
different connections in a cell
32Speech 12.2 + Data 64 kbps DL16Data 128 kbps DL
16Speech 12.2 + Data 64 kbps UL8Data 128 kbps UL
8Data 2048 kbps DL32Data 64 kbps DL
4Data 2048 kbps UL16Data 64 kbps UL
8Data 384 kbps DL256Speech 4.75 DL
4Data 384 kbps UL128Speech 4.75 UL
16Data 144 kbps DL128Speech 12.2 DL
8Data 144 kbps UL64Speech 12.2 UL
SFRadio bearer**SFRadio bearer**
** With 3.4 kbps Signaling

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Scrambling Code – Gold Sequence
l Scrambling codes Properties
[ 38 400 chip long sequences
[ Repeated every 10 ms
[ Coming from Pseudo Noise sequences
l For uplink, Scrambling code ( Gold sequence ) is used to separate
different connection
l For downlink, Scrambling code ( Gold sequence ) is used to separate
different cell
clong,1,n
clong,2,n
MSB LSB
scrambling sequence generator
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Code Multiplexing
l Downlink Transmission on a Cell Level
Scrambling code
Channelization code 1
Channelization code 2
Channelization code 3
User 1 signal
User 2 signal
User 3 signal
NodeB

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Code Multiplexing
l Uplink Transmission on a Cell Level
NodeB
Scrambling code 3
User 3 signal
Channelization code
Scrambling code 2
User 2 signal
Channelization code
Scrambling code 1
User 1 signal
Channelization code
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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

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Despreading
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)
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Spreading
Despreading
Chip
Symbol
Data
Spreading code
Spreading signal
=Data×code
Data
=Spreading×code
1
-1
1
-1
1
-1
1
-1
1
-1
Known code
at receiver
Spreading and Despreading
Correlation at a CDMA receiver
Correlation at a CDMA receiver

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Desired signal
Other user’s
signal
Desired spreading
signal
Spreading code
Data after
despreading
Other spreading
signal
Other signal after
integration
1
-1
1
-1
1
-1
8
-8
1
-1
8
-8
Data after
integration
Other signal after
despreading
Spreading and Despreading
Correlation at a CDMA receiver
Correlation with incorrect code
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Modulation Overview
1 00 1
time
Basic steady radio
wave:
carrier = A.cos(2πFt+φ)
Amplitude Shift
Keying:
A.cos(2πFt+φ)
Frequency Shift
Keying:
A.cos(2πFt+φ)
Phase Shift Keying:
A.cos(2πFt+φ)
Data to be transmitted:
Digital Input

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Modulation Overview
l Digital Modulation - BPSK
1
t
1 10
1
t
-1
NRZ coding
fo
BPSK
Modulated
BPSK
signal
Carrier
Information
signal
φ=0 φ=π φ=0
1 102 3 4 9875 6
1 102 3 4 9875 6
Digital Input
High Frequency
Carrier
BPSK Waveform
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Modulation Review
l Digital Modulation - QPSK
-1 -1
1 102 3 4 9875 6
1 102 3 4 9875 6
NRZ Input
I di-Bit Stream
Q di-Bit Stream
I
Component
Q
Component
QPSK Waveform
1
1
-1
1
-1
1
1
-1
-1
-1
1 1 -1 1 -1 1 1 -1

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Modulation Review
NRZ
coding
90o
NRZ
coding
QPSK
Q(t)
I(t)
fo
±A
±A ±Acos(ωot)
±Acos(ωot + π/2)
φ
1 1 π/4
1 -1 7π/4
-1 1 3π/4
-1 -1 5π/4
)cos(2: φω +oAQPSK
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Demodulation
l QPSK Constellation Diagram
1 102 3 4 9875 6
QPSK Waveform
1,1
-1,-1
-1,1
1,-1
1 -11 -1 1 -1-11-1 1
-1,1
NRZ Output

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Principle of RAKE Receiver
Receive set
Correlator 1
Correlator 2
Correlator 3
Searcher correlator Calculate the
time delay and
signal strength
Combiner
The
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
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Principle of RAKE Receiver
l The RAKE receiver take advantage of multi-path diversity
l The RAKE receiver processes the received signal
[ Identify the time delay positions at which significant energy arrives
[ Allocate correlation receivers (RAKE fingers) to those peaks
[ Within each Rake finger, track the fast-changing phase and amplitude values
[ Adjust the phase, remove the values originating from fast-fading
[ Combine the demodulated and phase-adjusted symbols across all active fingers
[ Present them to the decoder for further processing
l This processing is called Maximal Ratio Combining

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Demodulation
Frequency
translation
Matched
filter
Finger
combination
Despreading Symbol
decision
Fi
Σ
Delay (τn)
Delay (τ1)
Delay (τ0)
Estimated
chips
-1,1
x
Rake receiver
1,1
1,-1-1,-1
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