02 OWA200002 WCDMA RAN Fundamental (With Comments)

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    Internal

    OWA200002 WCDMA RAN

    Fundamental

    ISSUE1.0

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    Upon completion of this course, you will be able to:

    Outline the advantage of CDMA technology

    Outline the fundamentals of UTRAN

    Outline the key technologies of UTRAN

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    Chapter 1 CDMA Technology

    Chapter 2 WCDMA Fundamental

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    Multiple Access Technology and Duplex Technology

    Duplex technology

    Time division duplex (TDD)

    Frequency division duplex (FDD)

    Multiple access technology

    Time division multiple access (TDMA)

    Frequency division multiple access (FDMA)

    Code division multiple access (CDMA)

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    Multiple Access Technology

    power

    FDMA

    power

    TDMA

    power

    CDMA

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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 1 CDMA Technolofy

    Chapter 2 WCDMA Fundamental

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    Source

    codingChannelcoding

    Spreading Modulation

    Source

    decoding

    Channel

    decodingDespreading Demodulation

    Radio channel

    Processing Procedure of WCDMA System

    Transmission

    Reception

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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: Convolutional code1/21/3

    Data service: Turbo code (1/3)

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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

    8

    16

    .

    .

    .

    456

    2

    10

    .

    .

    .

    450

    6

    14

    .

    .

    .

    454

    1

    9

    .

    .

    .

    449

    4

    12

    .

    .

    .

    452

    7

    15

    .

    .

    .

    455

    3

    11

    .

    .

    .

    451

    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}

    First interleaving

    Second interleaving

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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

    (a)

    (b)

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    Spreading

    UE1: 1 1 1

    UE2: 1 1

    c1: 1111 1111

    c2: 1111 1111

    UE1c1 1111 1111UE2c2 1111 1111

    UE1c1 UE2c2 0 2 02 0 2 0 2

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    Despreading

    UE1c1 UE2c2: 0 2 0 2 0 2 0 2

    UE1 Dispreading by c1: 11 11 11 11

    Dispreading result: 0 2 0 2 0 2 0 2

    Integral judgment: 4 (means1) 4 (means1)

    UE2 Dispreading by c2: 11 11 11 11

    Dispreading result: 0 2 0 2 0 2 0 2

    Integral judgment: 4 (means1) 4 (means1)

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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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    WCDMA Spreading Code: OVSF

    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

    Typical service Data rate Downlink SF Uplink SF

    AMR 12.2+3.4

    128 64

    Modem28.8k 28.8+3.4

    64 32

    12.2kAMR & 64k packet data 12.2+64+3.4 32 16

    12.2kAMR & 144k packet data 12.2+144+3.4 16 8

    12.2kAMR & 384k packet data 12.2+384+3.4 8 4

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    Why we need Scrambling Code

    Distinguishing transmitter (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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    Configuration of Gold Sequence Generator

    Gold sequence is used as scrambling code in WCDMA

    clong,1,n

    clong,2,n

    MSB LSB

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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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    Gold Sequence

    The autocorrelation function has multi-value, not so goodas m sequence.

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

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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

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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

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    WCDMA Modulation

    Different modulation methods corresponding to different transmitting abilities in

    air interface

    R99/R4: adopt QPSK

    DL maximum data rate is 2.7Mbps

    HSDPA: adopt 16QAM

    DL maximum 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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    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

    Diversity methods

    Macroscopic diversity

    Soft handover and softer handover

    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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    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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    Performance of Diversity

    5 10 15SNRdB)

    0.0001

    0.001

    0.01

    0.1

    1

    BER

    1 finger

    2 finger

    5 finger

    No fading

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    WCDMA Fast Power Control

    Without power control With power control

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    RAKE receiver is adopted

    Higher interference tolerance and security performance

    Great flexibility in carrying multiple services with different bit rate

    and QoS requirement.

    High spectral efficiency

    Supporting soft handover and softer handover

    Advantages of WCDMA

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    Summary

    Spreading / Despreading principle

    UTRAN Voice Coding

    UTRAN Channel Coding

    UTRAN Spreading Code

    UTRAN Scrambling Code

    UTRAN Modulation

    UTRAN Transmission/Receiving

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