001 wcdma ran fundamental issue1
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Wcdma Ran FundamentalTRANSCRIPT
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Internal
OWA200002 WCDMA
RAN Fundamental
ISSUE1.0
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Upon completion of this module, you will be able
to:
�Know the development of 3G
�Outline the advantage of CDMA technology
�Outline the fundamentals of UTRAN
�Outline the key technologies of UTRAN
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Section 1 3G Section 1 3G OverviewOverview
Section 2 CDMA Section 2 CDMA FundamentalFundamental
Section 3 WCDMA Key TechnologiesSection 3 WCDMA Key Technologies
Section 4 Performance Section 4 Performance EnhancementEnhancement MethodsMethods
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Different Service, Different Technology
AMPS
TACS
NMT
Others
1G 1980sAnalog
GSMGSM
CDMA CDMA IS-95IS-95
TDMATDMA
IS-136IS-136
PDCPDC
2G 1990sDigital
Technologies drive
3G IMT-2000
UMTSUMTS
WCDMAWCDMA
CDMACDMA
20002000
Demands drive
TD-SCDMA
TD-SCDMA
3G provides compositive services for both operators and subscribers
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Different Service, Different Technology
AMPS
TACS
NMT
Others
1G 1980sAnalog
GSMGSM
CDMA CDMA IS-95IS-95
TDMATDMA
IS-136IS-136
PDCPDC
2G 1990sDigital
Technologies drive
3G IMT-2000
UMTSUMTS
WCDMAWCDMA
CDMACDMA
20002000
Demands drive
TD-SCDMA
TD-SCDMA
3G provides compositive services for both operators and subscribers
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3G Evolution
� Proposal of 3G
� IMT-2000: the general name of third generation mobile
communication system
�The third generation mobile communication was first proposed in
1985,and was renamed as IMT-2000 in the year of 1996
− Commercialization: around the year of 2000
− Work band : around 2000MHz
− The highest service rate :up to 2000Kbps
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3G Objectives
3G is developed to achieve:
� Universal frequency band for standard and seamless global
coverage
� High spectral efficiency
� High quality of service with complete security and reliability
� Easy and smoothly transition from 2G to 3G, compatible with 2G
� Provide multimedia services, with the rates:
�Vehicle environment: 144kbps
�Walking environment: 384kbps
� Indoor environment: 2Mbps
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1850 1900 1950 2000 2050 2100 2150 2200 2250
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 2250
1880 MHz 1980 MHz
UMTSGSM 1800 DECT MSS
1885 MHz 2025 MHz
2010 MHz
IMT 2000
MSSUMTS
Japan MSSIMT 2000MSSIMT 2000PHS
1895
1918
BC
1885
A A’
2170 MHz
IMT 20002110 MHz 2170 MHz
MSS MSS
CDMATDDWLL
FDDWLL
1980
2025MHz
GSM1800
CDMAFDDWLL
1960
1920
1945
China
cellular(1) cellular(2) cellular(2)
1805 MHz
1865
1865
1870
1885
1890
1895
1910
1930
1945
1965
1970
1975
3G Spectrum Allocation
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Bands WCDMA used
� Main bands
�1920 ~ 1980MHz / 2110 ~ 2170MHz
� Supplementary bands: different country maybe different
�1850 ~ 1910 MHz / 1930 MHz ~ 1990 MHz (USA)
�1710 ~ 1785MHz / 1805 ~ 1880MHz (Japan)
�890 ~ 915MHz / 935 ~ 960MHz (Australia)
�……
� Frequency channel number=central frequency×5, for main band:
− UL frequency channel number :9612~9888
− DL frequency channel number : 10562~10838
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Section 1 3G OverviewSection 1 3G Overview
Section 2 CDMA FundamentalSection 2 CDMA Fundamental
Section 3 WCDMA Key TechnologiesSection 3 WCDMA Key Technologies
Section 4 Performance Enhancement MethodsSection 4 Performance Enhancement Methods
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Multiple Access Technology
frequency
time
power
FDMA
frequency
time
power
TDMA
power
time
CDMA
frequency
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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.
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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
+10
-1+10
-1
+10
-1
+10
-1
(a)
(b)
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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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Dispreading
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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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
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Section 1 3G Overview
Section 2 CDMA Fundamental
Section 3 WCDMA Key Technologies
Section 4 Performance Enhancement Methods
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Sourcecoding
Channel coding
Spreading Modulation
Sourcedecoding
Channel decoding
Despreading Demodulation
Radio channelRadio channelRadio channel
Processing Procedure of WCDMA System
Transmission
Reception
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Source decoding
Source
codingInterleaving
deinterleaving
Scrambling spreading
Despreading
Modulation
Demodulation
Transmitting
Receiving
Radio channel
DescramblingDeinterleaving &channel decoding
Channel coding &
interleaving
Processing Procedure of WCDMA System
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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
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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.
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WCDMA Channel Coding
� Purpose:
�Enhance the correlation among symbols so as to recover the signal
when interference occurs.
� Types
�Speech service: Convolution code(1/2、1/3)
�Data service: Turbo code
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� Interleaving is used for continuous bit error correction
WCDMA Interleaving
1 2 3 4 5 6 7 8 ... ... 452 453 454 ……1 2 3 4 5 6 7 8 ... ... 452 453 454 ……
8
16
.
.
.
456
8
16
.
.
.
456
2
10
.
.
.
450
2
10
.
.
.
450
6
14
.
.
.
454
6
14
.
.
.
454
1
9
.
.
.
449
1
9
.
.
.
449
4
12
.
.
.
452
4
12
.
.
.
452
7
15
.
.
.
455
7
15
.
.
.
455
3
11
.
.
.
451
3
11
.
.
.
451
5
13
.
.
.
453
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}{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}
First interleaving
Second interleaving
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WCDMA Spreading Code: OVSF(Walsh)
� 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)
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Purpose of OVSF
� For uplink, OVSF is used to separate different services of one connection
� For downlink, OVSF is used to separate different connections
6412812.2+3.4AMR
4
8
16
32
Uplink SF
812.2+384+3.412.2kAMR & 384k packet data
1612.2+144+3.412.2kAMR & 144k packet data
3212.2+64+3.412.2kAMR & 64k packet data
6428.8+3.4Modem28.8k
Downlink SFData rateTypical service
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Why we need scrambling code
�Distinguishing 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
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WCDMA Scrambling Code: Gold Sequence
�Gold sequence is made by two m sequence.
�Advantage: No need to use GPS as the system clock, NodeB
can work in asynchronous mode, and it is also convenient for
indoor coverage
�Disadvantage: the interference between code is larger than m
sequence
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WCDMA Modulation
� Different modulation methods corresponding to different transmitting
abilities in air interface
�R99/R4: adopt QPSK
�DL max data rate is 2.7Mbps
HSDPA: adopt 16QAM
DL max data rate is 14.4Mbps
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Multi-path Environment
Time
Received
signal
Transmitted
signal
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Fading
Distance(m)
Received Power(dBm)
10 20 30
-20
-40
-60
Slow fading
Fast fading
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Introduction to Diversity Technique
� Diversity technique is used to obtain uncorrelated signals for combining
�Reduce the effects of fading
� Improve the reliability of communication
� Increase the coverage and capacity
� Diversity methods
�Time diversity
�Frequency diversity
�Space diversity
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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
CombinerThe
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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Structure of RAKE Receiver
∑∑∑∑Q
∑∑∑∑ I
Combiner
I
Matched
Filter
Phase
Rotator
Channel
Estimator
Delay
Equalizer
I
Q
Path 1
Path 2
Path 3
Input signal
Correlator
Code
Generators Q
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WCDMA Fast Power Control – Control Fast Fading
Without power control With power control
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Section 1 3G Overview
Section 2 CDMA Fundamental
Section 3 WCDMA Key Technologies
Section 4 Performance Enhancement Methods
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HSDPA Key Techniques - OverviewHSDPA Key Techniques - Overview
AMC (Adaptive modulation and code )
Fast SchedulingHARQ((((Hybrid ARQ))))
16QAMSF16, 2ms and CDM/TDM 3 New Physical Channels
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� AMC (Adaptive Modulation & Coding) based on Channel Quality Feedback
� Adjust data rate to compensate channel conditions
− Good channel condition – Higher rate
− Bad channel condition – Lower rate
� Adjust the coding rate to compensate channel conditions
− Good channel condition –3/4
− Bad channel condition –1/3
� Adjust the modulation scheme to compensate channel conditions
− Good channel condition –16QAM
− Bad channel condition – QPSK
� Channel Quality Feedback (CQI)
� UE measures the channel quality (SNR) reports (every 2ms or more cycle) to Node-B
� Node-B choose modulation and block size, data rate primarily based on CQI
HSDPA Key Techniques - AMCHSDPA Key Techniques - AMC
High data rate
Low data rate
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HSDPA Key Techniques - HARQHSDPA Key Techniques - HARQ
Conventional ARQ
–Received Transmitted blocks are decoded
–Checked for CRC errors on decoded blocks
–If errors
•discard the error bolcks
•Request the trasmitter for retransmission
Hybrid ARQ
–Received Transmitted blocks are decoded
–Checked for CRC errors on decoded blocks
–If errors
•Store the erroneous block without discarding
•Request the trasmitter for retransmission
•Combine the received re-trasmission with previously received trasnmisison
HARQ with Soft Combining
NodeB
UE Packet1? N
Packet 1 Packet 1
Packet 1
Packet1?
+A
Packet2
Transmitter
Receiver
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HSDPA Key Techniques - Fast scheduling
� Scheduler may be based on
� CDM, TDM
� Channel condition
� Amount of data waiting in the queue (delay)
� Fairness (satisfied users)
� Cell throughput, etc
Scheduling determines which user
shall be transmitted.
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HSDPA Key Techniques – CDM and TDM
Channelization codes allocated
for HS-DSCH transmission8 codes (example)
SF=16
SF=8
SF=4
SF=2
SF=1
User #1 User #2 User #3 User #4
TTI
Shared channelization
codes
10 ms
20 ms
40 ms
80 ms
Earlier releases
2 ms
Rel 5 (HS-DSCH)
“sub-frames” (2560 chips)
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HSDPA Key Techniques – 16QAM
� HSDPA Modulation
�QPKS
�16QAM
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Smart Antenna
Omni antenna Directional antenna Smart antenna
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Smart Antenna
� Reduce interference
� Increase coverage and capacity
Wanted signal
interference
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Summary
� Spreading/Dispreading principle
� UTRAN Voice Coding
� UTRAN Channel Coding
� UTRAN Spreading Code
� UTRAN Scramble Code
� UTRAN Modulation
� UTRAN Transmission/Receiving
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