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OWA200002 WCDMA RAN Basic
Principle
ISSUE1.0
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Chapter 1 Radio Transmission Environment Chapter 1 Radio Transmission Environment
Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement MethodsChapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD ModeChapter 4 WCDMA FDD Mode
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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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Frequency Selection of Fading
NarrowbandSystem
NarrowbandSystem
Fading
Transmit Signal Received Signalff
P(f) P(f)
Fading
Transmit Signal Received Signalff
P(f) P(f)
BroadbandSystem
BroadbandSystem
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Chapter 1 Radio Transmission EnvironmentChapter 1 Radio Transmission Environment
Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement MethodsChapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD ModeChapter 4 WCDMA FDD Mode
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Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
2.1 Multiple Access Technology and Duplex Technology2.1 Multiple Access Technology and Duplex Technology
2.2 CDMA Principle and RAKE Technology2.2 CDMA Principle and RAKE Technology
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Multiple Access Technology and Duplex Technology
Multiple access technology
Time division multiple access (TDMA)
Frequency division multiple access (FDMA)
Code division multiple access (CDMA)
Duplex technology
Time division duplex (TDD)
Frequency division duplex (FDD)
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Traffic channels: different users are assigned unique code and transmitted over the same frequency band, for example, WCDMA and CDMA2000
Traffic channels: different frequency bands are allocated to different users,for example, AMPS and TACS
Traffic channels: different time slots are allocated to different users, for example, DAMPS and GSM
FrequencyTime
Power
FrequencyTime
Power
FrequencyTime
Power
FDMA
TDMA
CDMA
User
User
User
User User
User
Multiple Access Technology
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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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Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
2.1 Multiple Access Technology and Duplex Technology2.1 Multiple Access Technology and Duplex Technology
2.2 CDMA Principle and RAKE Technology2.2 CDMA Principle and RAKE Technology
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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
+1 0-1+1 0-1
+1 0-1
+1 0-1
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OVSF&Walsh
Creating the orthogonal Creating the orthogonal code sequencescode sequences
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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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 -1/7Delay time
(chip)
Correlation
1
Example: -1 -1 -1 1 1 -1 1Example: -1 -1 -1 1 1 -1 1
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Configuration of Gold Sequence Generator
Gold sequence is used as scrambling Gold sequence is used as scrambling code in WCDMAcode in WCDMA
clong,1,n
clong,2,n
MSB LSB
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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
Spreading code
Spreading and Despreading (DS-CDMA)
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Desired signal
Other user’s signal
Desired spreadingsignal
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 (DS-CDMA)
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Sourcecoding
Channel coding
Spreading Modulation
Source decoding
Channel decoding Despreading Demodulation
Radio channelRadio channelRadio channelRadio channel
Processing Procedure of CDMA System
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Spectrum Analysis of Spreading & Despreading
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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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
MatchedFilter
PhaseRotator
Channelestimator
DelayEqualizer
I
Q
Path 1
Path 2
Path 3
Input signal
Correlator
Codegenerators Q
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Advantages of CDMA
RAKE receiver is adopted
The time diversity effect generated by channel coherence time is efficiently used.
frequency diversity
Wideband frequency spectrum
Higher interference tolerance and security performance
Low signal transmission power
Great flexibility in carrying multiple services with largely different bit rate and QoS requirement.
Different spreading factors for different services with different data rates
High spectral efficiency
All users can share the same frequency spectrum simultaneously.
Supporting soft handover and softer handover.
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Chapter 1 Radio Transmission Environment Chapter 1 Radio Transmission Environment
Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement MethodsChapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD ModeChapter 4 WCDMA FDD Mode
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HSDPA Key Techniques - OverviewHSDPA Key Techniques - Overview
AMC 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
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
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
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
NodeBNodeB
UEUE Packet1?Packet1? NN
Packet 1Packet 1 Packet 1Packet 1
Packet 1Packet 1
Packet1?Packet1?+
AA
Packet2Packet2
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
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.
Scheduling determines which user
shall be transmitted.
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HSDPA Key Techniques – CDM and TDM
Channelization codes allocatedfor HS-DSCH transmission
8 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 ms20 ms40 ms80 ms
Earlier releases
2 msRel 5 (HS-DSCH)
“sub-frames” (2560 chips)
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HSDPA Key Techniques – 16QAM
HSDPA Modulation
QPKS
16QAM
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Introduction to 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
Macroscopic diversity
Soft handover and softer handover
Reduce large-scale fading
Microscopic diversity
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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
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Basic Combining Methods
Maximal-Ratio Combiner
The multi-path signals are weighted
proportional to their signal SNR and then
summed.
Equal-Gain Combiner
Equal-gain combining is similar to maximal-
ratio combining, but there is no attempt to
weight the signal before addition.
Selection Combiner
Choose the signal with the highest
instantaneous quality, so the output quality is
equal to that of the best incoming signal.
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Smart Antenna Reduce interference
Increase coverage and capacity
Wanted signal
interference
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Smart Antenna
Omni antenna Directional antenna Smart antenna
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Chapter 1 Radio Transmission Environment Chapter 1 Radio Transmission Environment
Chapter 2 CDMA FundamentalChapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement MethodsChapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD ModeChapter 4 WCDMA FDD Mode
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Characteristics of WCDMA FDD
Channel bandwidth: 5MHz
Chip rate: 3.84Mcps
Frame length: 10ms
Voice coding: AMR (Adaptive Multi-Rate)
Uplink and downlink modulation: QPSK/QPSK
Coherence demodulation aided with pilot
Fast closed loop power control: 1500Hz
Handover: soft/hard handover
Support synchronous and asynchronous NodeB
operation
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Characteristics of WCDMA FDD
Satisfy the minimum performance requirement of IMT2000
Compatible with GSM-MAP core network
Comparatively steady version R99 has been released
Support open loop and closed loop transmit diversity mode
Support Common Packet Channel(CPCH) and Downlink
Share Channel, adapt to Internet data access mode
Support macro diversity, selection diversity of NodeB
location
Support different fast power control algorithms and open
loop, out loop power control
Fully support UE locating services
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WCDMA Voice Evolution
Adopt AMR voice coding, and support voice
quality of 4.75Kbps ~ 12.2Kbps
Adopt soft handover and transmit diversity to
improve system capacity
Provide high fidelity voice mode
Fast power control
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Data Service Evolution of WCDMA
Support maximum 2Mbps data service
Support packet switch
Adopt ATM platform currently
Provide QoS
Common Packet Channel(CPCH) and Downlink Share Channel(DSCH) can support Internet packet services better
Provide mobile IP service(dynamic allocation of IP addresses)
TFCI domain provides dynamic data rate
Provide high-quality support for uplink-downlink symmetric data service, such as voice, video phone, conference TV
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