01- owa200002 wcdma ran basic principle
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OWA200002
WCDMA RAN Basic
Principle
ISSUE1.0
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Chapter 1 Radio Transmission Environment
Chapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement Methods
Chapter 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
Narrowband
System
Fading
Transmit Signal Received Signalff
P(f) P(f)
Fading
Transmit Signal Received Signalff
P(f) P(f)
Broadband
System
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Chapter 1 Radio Transmission Environment
Chapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD Mode
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Chapter 2 CDMA Fundamental
2.1 Multiple Access Technology and Duplex Technology
2.2 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: differentusers 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
Trafficchannels: different time slots
are allocated to different users, for
example, DAMPS and GSM
Power
Power
Power
FDMA
TDMA
CDMA
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 Fundamental
2.1 Multiple Access Technology and Duplex Technology
2.2 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
+10
-1
+1
0
-1
+1
0
-1
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OVSF&Walsh
Creating the orthogonal code 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 1
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Configuration of Gold Sequence Generator
Gold sequence is used as scrambl ing code in WCDMA
clong,1,n
clong,2,n
MSB LSB
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Desired signal
Other users 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 afterintegration
Other signal after
despreading
Spreading and Despreading (DS-CDMA)
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Source
codingChannelcoding
Spreading Modulation
Source
decoding
Channel
decodingDespreading Demodulation
Radio 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
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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Advantages of CDMA
RAKE receiver is adopted
The time diversity effect generated by channelcoherence time is efficiently used.
frequency diversity
Wideband frequency spectrum
Higher interference tolerance and security performanceLow signal transmission power
Great flexibility in carrying multiple services with largelydifferent 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 spectrumsimultaneously.
Supporting soft handover and softer handover.
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Chapter 1 Radio Transmission Environment
Chapter 2 CDMA Fundamental
Chapter 3 Performance Enhancement Methods
Chapter 4 WCDMA FDD Mode
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HSDPA Key Techniques - Overview
AMC Fast SchedulingHARQHybrid 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 conditionHigher rate
Bad channel conditionLower rate
Adjust the coding rate to compensate channel conditions
Good channel condition3/4
Bad channel condition1/3
Adjust the modulation scheme to compensate channel conditions
Good channel condition16QAM
Bad channel conditionQPSK
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 - AMC
High data rate
Low data rate
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HSDPA 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 forretransmission
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 withpreviously 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 Techniques16QAM
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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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 2 CDMA Fundamental
Chapter 3 Performance Enhancement Methods
Chapter 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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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 DownlinkShare Channel(DSCH) can support Internet packetservices better
Provide mobile IP service(dynamic allocation of IPaddresses)
TFCI domain provides dynamic data rate
Provide high-quality support for uplink-downlinksymmetric data service, such as voice, videophone, conference TV
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