01- owa200002 wcdma ran basic principle

8/13/2019 01- Owa200002 Wcdma Ran Basic Principle

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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved

www.huawei.com

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OWA200002

WCDMA RAN Basic

Principle

ISSUE1.0


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HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 2

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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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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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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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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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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