1 - Introduction to UMTS.pptx

7/28/2019 1 - Introduction to UMTS.pptx

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INTRODUCTION TO UMTSRF Optimization - South


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Contents


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Overview of 3G

3G Spectrum

Multiple Access and Duplex Technology

Characteristics of WCDMA System

CDMA Principle and RAKE technology

Characteristics of WCDMA FDD

Advantages of WCDMA

Performance Enhancement Methods


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Overview of 3G


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We have 4 generations of mobile/data communications:

1G analog cellular mobile communication, ex: AMPS (advanced mobile phone system).

Disadvantages: no high speed services, limited types of services etc..

To Solve these disadvantages 2G was developed.

2G ex: DAMPS or IS-54 of USA using 800MHZ & the IS-95 (CDMA mode) European using

800 or 1900MHZ.2ndG GSM system uses FDD (Frequency Division Duplex) &TDMA modes and each carrier

has 8 channels 200KHZ apart.

Advantages: transmission of voice& low speed data service.

2.5G and 2.75G address the medium rate data transmission using GPRS and EGPRS.

3G system can provide multiple kinds of high quality multimedia services. It has a verylarge capacity which is 10 times that of analog.

4G system that is known as LTE (Long Term Evolution). It is capable of reaching 100Mbps

in the DL and 50Mbps in the UL.


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3G has two standardizing bodies: 3GPP(3G partnership project) &3GPP2.

3GPP adopts the WCDMA technologies to construct a new RAN and a core

switching network.

3GPP2 adopts the cdma2000 which is applied for radio access.


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In 3G there are three types of services:

Circuit Switched: This includes voice and video calls.

Packet Switched (Real Time): Like Streaming sessions.

Packet Switched (Non-Real Time): This includes services like Email and MMS.


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There are four traffic classes in 3G:

Conversational

Streaming

Interactive

Background


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Traffic class Conversational class Streaming class Interactive class Background

- Preserve time

relation (variation)

between information

entities of the stream

- Request

response pattern

- Destination is not

expecting the data

within a certain time

Conversationalpattern (stringent and

low delay )

- Preserve payloadcontent

- Preserve payloadcontent

Example of the

application

- voice,

videotelephone

VOD, Web broadcast - Web browsing,

network games

- background

download of emails

Fundamental

characteristics

- Preserve time

relation (variation)

between information

entities of the stream


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conversational AMR speech service

Video telephony CS64

streaming

interactive

Web-browsing.

Games

background e-mail delivery

SMS ...


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Iu

UTRAN

UE

Uu

CN

UTRANUMTS Terrestrial Radio Access Network

CN Core Network

UE User Equipment

UMTS System Architecture:


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UMTS (Universal Mobile Telecommunications System) is the 3G mobiletelecommunication system that uses WCDMA as air interface. UMTS consists

of UTRAN (UMTS Terrestrial Radio Access Network), CN &UE.

RAN is used to process all radio related functions.

CN is used to process all voice calls and data connections & it implements the

function of external network switching &routing, CN is divided into CS which

covers MSC, VLR, IWF, GMSC, &PS which provides packet data services for

subscribers. This includes the SGSN & GGSN.


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UTRAN System Architecture:


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UTRAN is divided into RNC (radio network controller) it implements connectionestablishment modulation/demodulation and Node B is the base station ofWCDMA system.

UE is divided into ME &USIM (UMTS subscriber module).

R99 network structure has considered the 2G/3G compatibility so as tosupport the smooth transition of GSM/GPRS/3G.

IuR interface has been added that interconnects two RNCs


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GSM and UMTS connectivity:


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3G Spectrum


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-1920-1980 and 2110-2170 MHz (UL / DL) Frequency Division Duplex (FDD,

W-CDMA) Paired uplink and downlink,

-12 paired channels with spacing=5MHZ.

-UARFCN = 5 * (frequency in MHz)


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Multiple Access

and

Duplex Technology


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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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Characteristics of

WCDMA System


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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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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 11 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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Spreading

Despreading

Chip

Symbol

Data

Spreading code

Spreading signal=Datacode

Data

=Spreadingcode

1

-1

1

-1

1

-1

1

-1

1

-1

Spreading code

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 &

DespreadingSpreading 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 helps to overcome the multi-path fading and enhances the receive

performance of the system


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Characteristics of

WCDMA FDD


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Channel bandwidth: 5MHz

Chip rate: 3.84Mcps

Frame length: 10ms

Voice coding: AMR (Adaptive Multi-Rate)

Uplink and downlink modulation: BPSK/QPSK

Coherence demodulation aided with pilot

Fast closed loop power control: 1500Hz

Handover: soft/hard handover

Supports synchronous and asynchronous NodeB operation


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Compatible with GSM-MAP core network

Comparatively steady version R99 has been released

Supports open loop and closed loop transmit diversity mode

Supports Common Packet Channel (CPCH) and Downlink Share Channel.

Supports macro diversity, selection diversity of NodeB location

Supports different fast power control algorithms and open loop, out loop

power control

Fully support UE locating services


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Advantages of WCDMA


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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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Performance Enhancement

Methods

HSDPA K T h i


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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 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 - AMC

High data rate

Low data rate


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HSDPA Key Techniques - HARQConventional 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

HSDPA Ke Te hniq es Fast


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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


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HSDPA Key Techniques 16QAM


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Introduction to Diversity Technique

Diversity technique is used to obtainuncorrelated signals for combining

Reduce the effects of fading fast fading caused by multi-path

Slow fading caused by shadowing

Improve the reliability ofcommunication

Increase the coverage andcapacity

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 andthen summed.

Equal-Gain Combiner

Equal-gain combining is similar tomaximal-ratio combining, but there is noattempt to weight the signal beforeaddition.

Selection Combiner

Choose the signal with the highestinstantaneous quality, so the outputquality is equal to that of the bestincoming signal.


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Smart Antenna

Omni antenna Directional antenna Smart antenna


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Thank You

1 - Introduction to UMTS.pptx

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