MIMO OFDM Emulation

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    MIMOw

    irelesschannelem

    ulation

    Ro

    gerPiqueras

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    MIMOwirelessch

    annelem

    ulation

    Overview:

    Wirelesss

    ystems

    Mobilecha

    nnel

    OFDM

    2

    MIMO

    IEEE802.11n

    Channelm

    odels

    Simulation

    /Emulation

    Wirelessc

    hannelemulatio

    n

    Futurework

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    Wireless

    systems

    Whywireless

    systems?

    3

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    Mobilechannel

    Themobilechannelisacomplex

    channel:

    Multipath,scattering

    Dopplerspectrum

    Shadowing

    4

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    Mobilechannel

    MultipathFrequencyselectiv

    echannel

    Timedomain

    responseofthechannelconsistsonvariousrayshavingaco

    mplex

    Gaussiandistribution

    Channelfrequencyresponseisno

    tflat

    Coherencebandwidth

    5

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    Mobilechannel

    Dopplerspectrum

    /fading

    Timevar

    yingchannel

    Changeinthe

    carrierfrequencyduetorelativemovementbetweenthemobileand

    the

    BS

    fDmax=v/C

    oherencetime1/fDma

    x

    Fadingchanne

    l

    severechangesin

    therecievedsignalpo

    wereverycoherencet

    ime

    6

    Howcanweovercomeormitigateth

    enegativeeffectsofthemobilechannel?

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    Mobilechannel

    Newtechniquestohandlefrequencyselectivityand

    fadingchan

    nels,

    suchas...

    OFDM

    MIMO

    7

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    Orthogona

    lFrequenc

    y-Division

    Multiplexin

    g

    (OFDM)

    OFDMconvertsawidebandsignal

    intomultiplenarrowbandsignals

    placedsidebysideinthefrequency

    domain.

    Partofthesignalismodulatedin

    eachsubchannelandtransmitted

    8

    throughanalm

    ostflatfadingchannel.

    Ifoneofthesu

    bchannelsisaffected

    byaseverefading,simplynothingis

    transmittedinthatsubchannel

    Thisresultsinastrongresilency

    againstfrequencyselectivechannels

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    MultipleIn

    put-Multi

    pleOutpu

    t(MIMO)

    Traditionallymultipleantennasplaced

    atthereceiverto

    applydiversity

    Spatialdiversity(eachantennawill

    seeadifferent

    andindependent

    channel)

    Significantimm

    unitytofading

    Resultsimprov

    easthenumberof

    9

    anennasncre

    ase

    Evenbetterresultsareachieved

    whenmultipleant

    ennasplacedalso

    atthetransmitter

    Totalavailabletransmitpowerissplit

    uniformlyacrosstransmitantennas

    Finiteoptimum

    numberoftxantennas

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    IEEE802

    .11n

    OFDM

    Resilencyaganistfre

    quencyselective

    channels

    MIMO

    Res

    ilencyagainstfad

    ingchannels

    Mobilechanne

    lisafadingand

    frequencyselectivechannel

    MIMO+OF

    DMisagoodsolutionformobilecom

    munications

    1

    0

    IEEE802.1

    1nstandard

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    IEEE802

    .11n

    IEEE802.1

    1nstandard

    WLANstandardimprovingthePhysicalLay

    erand

    MACLayerofthe

    traditionalWLANs

    IndoorMIMO/OFDMsystem

    Range~

    100met

    ers

    Maximumbitrate:600Mbps(3x3antennas)(typical

    bitrate74Mbps)

    Carrierfrequency

    :2.4

    or5GHz

    1

    1

    Fullcompatibilityw

    ithcurrentWLANs

    Projecttodevelope

    IEEE802.1

    1nbeganin2003

    Juststartingtobeinacommercialstage

    Intelhasstartedtoadd802.1

    1ninsomeo

    fitsproducts

    Forfuturecommerc

    ialization,manytestsh

    avetobedone

    WirelesschannelonOF

    DM-MIMOsystemssimulation

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    Channel

    models

    MxNMIMOchan

    nelisequivalenttoM

    Nimpulseresponse

    s,

    eachrepresenting

    a

    subchannel

    ModelaSISOch

    annel,thenextendtoMIMO(repeatMNtimesplusaddingoth

    er

    artifacts,

    suchas

    spatialcorrealtionbetweenantennaelem

    ents...)

    1

    2

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    Channel

    models

    StatisticalModel

    forIndoorMultipathPropagation(A.

    Sale

    h,

    R.

    Valenzuela)

    Channelmeas

    urement

    1

    3

    Results(Powe

    rDelayProfile)

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    Channel

    models

    Wirelessindoorch

    annelmodeling

    Multipath:cluste

    ringofarrivingrays(angularclusters)

    Channelmodele

    dasanFIR

    1

    4

    TX

    v

    RX

    ArrivalTimes

    t

    Doubleexponentialdecayoftheimpulses(

    clustersandrayswithina

    cluster)

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    Channel

    models

    Clusteringofr

    ays

    Dopplerspectrum/Fading

    Shadowfading

    Pathlossmod

    el

    Freespacelo

    ss(LFS

    )uptoabrea

    kpointdistance(dBP

    )

    1

    5

    Slopeof3.5

    afterdBP

    Addingthesee

    lementstogether

    SISOchanne

    lmodel

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    Channel

    models

    Setofchannelm

    odelsapplicabletoindoorWLAN

    systems

    1

    6

    Channelmode

    lisaFIR

    Exte

    ndtoMIMO(matrixofMxNFIRs)

    OtherMIMOchannelartifactsshouldbeadded

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    Channel

    models(

    MIMO)

    MIMOmatrixformulation(foreachtap)

    1

    7

    P

    owerof

    eachtap

    RiceanK-factor(0

    forNLOSt

    aps)

    LOS

    [S](constantRice

    Steeringmatrix)

    NLOS

    [X](timeva

    rying

    Rayleigh

    and

    Correlationmatrix)

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    Channel

    models(

    MIMO)

    LOS

    RiceS

    teeringmatrix

    Differenceinp

    hasebetweenthera

    ysarriving/leavingth

    etxandrxantenna

    elements

    Constantmatrix

    Onlyfirsttap(

    LOS)

    1

    8

    T

    Tx

    Tx

    Tx

    Tx

    Tx

    Rx

    Rx

    R

    x

    Rx

    Rx

    AoD

    n

    d

    j

    AoD

    d

    j

    AoA

    n

    dj

    AoA

    d

    j

    S

    =

    ]}

    )1

    sin[(

    2

    exp{

    ...

    )}

    sin(

    2

    exp{

    1

    ]}

    )1

    sin[(

    2

    exp{

    ...

    )}

    sin(

    2

    exp{

    1

    ]

    [

    Rxantennaelements

    Txantennaelements

    MxNmatrix

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    Channel

    models(

    MIMO)

    NLOS

    RayleighandCorrelationm

    atrix(I)

    Correlationbetweentxantennasand

    rxantennas([Rtx]and

    [Rrx]matrixes)

    Fromanten

    naspacingstotheoreticalcapacities(L.

    Schumacher,K.

    Pedersen,

    P.

    Morgensen)

    PowerAngularSpectrum(PAS):Uniform,

    GaussianorLaplacia

    n

    1

    9

    d

    A

    A

    PAS

    e

    j

    i

    kd

    j

    ij

    )

    (

    )

    (

    )

    (

    )

    sin(

    2

    =

    Uniformline

    arantennaarray

    corre

    lationofrx/txsignalsbetw

    eenantennaelements

    Spacingbetween

    antennas

    Elementelectromagnetic

    pattern

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    Channel

    models(

    MIMO)

    NLOS

    RayleighandCorrelationm

    atrix(II)

    Correlationbetweentxantennasand

    rxantennas([Rtx]and

    [Rrx]matrixes)

    Generation

    ofthecorrelationmatrixes

    2

    0

    Example:4x4MIMOchannel

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    Channel

    models(

    MIMO)

    NLOS

    RayleighandCorrelationm

    atrix(III)

    Rayleighfading

    Generation

    ofaRayleighvector

    ShapingofthevectorwithaFIR(order=7)togeneratetheadequateDopplerspectrum

    Combinationo

    ftheCorrelationandth

    eRayleighfading

    Kronecke

    rroduct

    Raleihvector

    2

    1

    Addingotherar

    tifacts

    Shadowfading

    Dopplercom

    ponentduetoamoving

    vehicle(optional)

    Dopplercom

    ponentsdueto

    fluorescentlights(optional)

    Bellshaped

    oppler

    spectrumw

    itha

    200HzDoppler

    component

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    Simulatio

    n/Emula

    tion

    IEEE802.1

    1nstill

    intestingstage(alread

    ybeingimplementedb

    yIntel)

    Performanceofad

    vancedwirelesstechniquessuchasMIMOis

    highlydependantonth

    e

    channel

    Necessityofrealisingcredibletestsandvalidationsunderrealisticconditions

    Inefficiencyofre

    almeasurements(moving

    therxalongaspecificindoorlocation)

    2

    2

    D.P.McNam

    ara,M.A.Beach,P.N.

    Fletcher,P.Karlsson,Initial

    InvestigationofMIMOChannelsin

    Indo

    orEnviroments

    Necessityofreplicatingthe

    wirelesschannelin

    thelaboratory

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    Simulatio

    n/Emula

    tion

    Wirelesschannelreplicationinthelaboratory

    Traditionaloption

    Simulation

    Easysolution

    ,but...

    2

    3

    MIMOsystems

    Thechannelmatrix