02-OWA200002 WCDMA RAN Fundamental (with comments) .ppt

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OWA200002 WCDMA RAN
Fundamental
ISSUE1.0

HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 2
Upon completion of this course, you will be able to:
Outline the advantage of CDMA technology
Outline the fundamentals of UTRAN
Outline the key technologies of UTRAN

Chapter 1 CDMA Technology
Chapter 2 WCDMA Fundamental

Multiple Access Technology and Duplex Technology
 Duplex technology
Time division duplex (TDD)
 Frequency division duplex (FDD)
 Multiple access technology
Time division multiple access (TDMA)
Frequency division multiple access (FDMA)
Code division multiple access (CDMA)

Multiple Access Technology
power
FDMA
power
TDMA
power
CDMA

Characteristics of CDMA System
 High Spectral Efficiency
 Frequency multiplex coefficient is 1.
 Soft capacity
Quality
Coverage
Interference
 Self-interference system
A UE transmission power is interference for another UE.

Chapter 1 CDMA Technolofy
Chapter 2 WCDMA Fundamental

Source
coding
Channel
coding
Spreading Modulation
Source
decoding
Channel
decoding
Despreading Demodulation
Radio channel
Processing Procedure of WCDMA System
Transmission
Reception

Terms
 Bit, Symbol, Chip
Bit: data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
Process Gain: 10log (cps/bps); 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

WCDMA Source Coding
 AMR (Adaptive Multi-Rate) voice coding
Multi-rate:
− 8 kinds of coding rates
− Benefit multi-mode terminal design
Adaptation: when cell load increases, the system will decrease
speech rate of part of subscribers automatically so as to support
more subscribers.

WCDMA Channel Coding
 Purpose:
Enhance the correlation among symbols so as to recover the signal
when interference occurs.
 Types
Speech service: Convolutional code（1/2、1/3）
Data service: Turbo code (1/3)

 Interleaving is used for continuous bit error correction
WCDMA Interleaving
1 2 3 4 5 6 7 8 ... ... 452 453 454 ……
8
16
.
.
.
456
2
10
.
.
.
450
6
14
.
.
.
454
1
9
.
.
.
449
4
12
.
.
.
452
7
15
.
.
.
455
3
11
.
.
.
451
5
13
.
.
.
453
.... ....
B0 B1 B2 B3 B4 B5 B6 B7
{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}
First interleaving
Second interleaving

Correlation
 Correlation is a measure of similarity of between any two arbitrary signals.
 EXAMPLE:
-1 1 -1 1
1 1 1 1
-1 1 -1 1
Zero correlation
Orthogonal signals
-1 1 -1 1
-1 1 -1 1
1 1 1 1
1 correlation
Identical signals
+1
0
-1
+1
0
-1
+1
0
-1
+1
0
-1
(a)
(b)

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

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)

Spectrum Analysis of Spreading & Dispreading
Spreading code
Spreading code
Signal
Combination
Narrowband signal
f
P(f)
Broadband signal
P(f)
f
Noise
P(f)
f
Noise+Broadband signal
P(f)
f
Recovered signal
P(f)
f

WCDMA Spreading Code: OVSF
 OVSF: Orthogonal Variable Spreading Factor, generated by Walsh matrix
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)

Purpose of OVSF
 For uplink, OVSF is used to separate different services of one connection
 For downlink, OVSF is used to separate different connections
Typical service Data rate Downlink SF Uplink SF
AMR 12.2+3.4 128 64
Modem28.8k 28.8+3.4 64 32
12.2kAMR & 64k packet data 12.2+64+3.4 32 16

Why we need Scrambling Code
Distinguishing transmitter (cells or users)
Downlink
Scrambling code is used for distinguishing cells
OVSF code is used for distinguishing users
Uplink
Scrambling code is used for distinguishing users
OVSF code is used for distinguishing channels of one user

Configuration of Gold Sequence Generator
Gold sequence is used as scrambling code in WCDMA
clong,1,n
clong,2,n
MSB LSB

Autocorrelation
 Autocorrelation is related to the muti-path interference characteristic.
Delay time sequence correlation
0 -1 -1 -1 1 1 -1 1 1
1 -1 -1 1 1 -1 1 -1 -1/7
2 -1 1 1 -1 1 -1 -1 -1/7
3 1 1 -1 1 -1 -1 -1 -1/7
4 1 -1 1 -1 -1 -1 1 -1/7
5 -1 1 -1 -1 -1 1 1 -1/7
6 1 -1 -1 -1 1 1 -1 -1/7
Delay time (chip)
Correlation
1
 Example: -1 -1 -1 1 1 -1 1

Gold Sequence
 The autocorrelation function has multi-value, not so good
as m sequence.
0
0.2
0.4
0.6
0.8
1
1.2

Spreading
Despreading
Chip
Symbol
Data
Spreading code
Spreading signal
=Data×code
Data
=Spreading×code
1
-1
1
-1
1
-1
1
-1
1
-1
Spreading code
Spreading and Despreading

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

WCDMA Modulation
 Different modulation methods corresponding to different transmitting abilities in
air interface
R99/R4: adopt QPSK
DL maximum data rate is 2.7Mbps
HSDPA: adopt 16QAM
DL maximum data rate is 14.4Mbps

Multi-path Environment
Time
Received
signal
Transmitted
signal

Fading
Distance(m)
Received Power (dBm)
10 20 30
-20
-40
-60
Slow fading
Fast fading

Diversity Technique
 Diversity technique is used to obtain uncorrelated signals for combining
Reduce the effects of fading
− Fast fading caused by multi-path
− Slow fading caused by shadowing
Improve the reliability of communication
Increase the coverage and capacity
 Diversity methods
Macroscopic diversity
− Soft handover and softer handover
Microscopic diversity

Microscopic Diversity
 Time diversity
Channel coding, Block interleaving, error-correction
 Frequency diversity
The user signal is distributed on the whole bandwidth frequency
spectrum
 Space diversity
Receive diversity
Transmit diversity
 Polarization diversity
Vertical polarization
Horizontal polarization

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
t
t
s(t) s(t)
RAKE receiver help to overcome on the multi-path fading and enhance the receive
performance of the system

Performance of Diversity
5 10 15
SNR（dB)
0.0001
0.001
0.01
0.1
1
BER
1 finger
2 finger
5 finger
No fading

WCDMA Fast Power Control
Without power control With power control

 RAKE receiver is adopted
 Higher interference tolerance and security performance
 Great flexibility in carrying multiple services with different bit rate
and QoS requirement.
 High spectral efficiency
 Supporting soft handover and softer handover
Advantages of WCDMA

Summary
 Spreading / Despreading principle
 UTRAN Voice Coding
 UTRAN Channel Coding
 UTRAN Spreading Code
 UTRAN Scrambling Code
 UTRAN Modulation
 UTRAN Transmission/Receiving

02-OWA200002 WCDMA RAN Fundamental (with comments) .ppt

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