CHANNEL ESTIMATION FOR LTE DOWNLINK

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  • MEE09:58

    CHANNEL ESTIMATION FOR LTE

    DOWNLINK

    AsadMehmood

    WaqasAslamCheema

    ThisthesisispresentedaspartofDegreeofMasterofScienceinElectricalEngineering

    BlekingeInstituteofTechnology

    September2009

    Blekinge Institute of Technology School of Engineering Department of Signal Processing Supervisor Prof. Abbas Mohammed Examiner Prof. Abbas Mohammed

  • Abstract

    3GPPLTEistheevolutionoftheUMTSinresponsetoeverincreasingdemandsfor

    highqualitymultimediaservicesaccordingtousersexpectations.Sincedownlink

    isalwaysan important factor incoverageandcapacityaspects,specialattention

    hasbeengiveninselectingtechnologiesforLTEdownlink.Noveltechnologiessuch

    asorthogonalfrequencydivisionmultiplexing(OFDM)andmultipleinput,multiple

    output (MIMO), can enhance the performance of the current wireless

    communicationsystems.Thehighdataratesandthehighcapacitycanbeattained

    byusing theadvantagesof the two technologies.These technologieshavebeen

    selectedforLTEdownlink.

    Pilotassistedchannelestimationisamethodinwhichknownsignals,calledpilots,

    aretransmittedalongwithdatatoobtainchannelknowledgeforproperdecoding

    of received signals. This thesis aims at channel estimation for LTE downlink.

    ChannelestimationalgorithmssuchasLeastSquares(LS),MinimumMeanSquare

    Error(MMSE)havenbeenevaluatedfordifferentchannelmodelsinLTEdownlink.

    Performanceof these algorithmshasbeenmeasured in termsofBitErrorRate

    (BER)andSymbolErrorRate(SER).

  • ACKNOWLEGEMENT

    All praises and thanks to Almighty ALLAH, themost beneficent and themost

    merciful,who gave us the all abilities and helped us to complete this research

    work.

    We would like to express our sincere gratitude to our supervisor Prof. Abbas

    Mohammed for his support and guidance during the course of this work. His

    encouragementandguidancehasalwaysbeena sourceofmotivation forus to

    explore various aspects of the topic. Discussions with him have always been

    instructiveandinsightfulandhelpedustoidentifyourideas.

    Finally,weareverygratefultoourparents,brotherandsistersfortheirsacrifices,

    unremittingmotivationandeverlasting loveandtheircontinuoussupportduring

    ourstayinBTH.

  • 1

    Table of Contents

    Abstract..................................................................................................................................2

    List of Figures.......................................................................................................................4

    Chapter1Introduction..........................................................................................7

    1.1) Introduction...............................................................................................................7

    1.2) Objectives...................................................................................................................9

    1.3) OutLineoftheMasterThesis..................................................................................10

    Chapter2OverviewofLTEPhysicalLayer...........................................................11

    2.1)Introduction..................................................................................................................11

    2.2)ObjectivesofLTEPhysicalLayer...................................................................................12

    2.3)FrameStructure............................................................................................................12

    2.3.1)Type1FrameStructure.............................................................................................12

    2.3.2)Type2FrameStructure.............................................................................................13

    2.4)PhysicalResourceandSlotstructure............................................................................15

    2.5)LTEDownlinkReferenceSignalsStructure...................................................................16

    2.6)LTEDownlinkParameters............................................................................................17

    2.7)MultipleAntennaTechniques.......................................................................................18

    2.7.1)SpatialDiversity.........................................................................................................19

    2.7.1.1)ReceiveDiversity.....................................................................................................20

    2.7.1.2)TransmitDiversity...................................................................................................21

    2.7.1.3)CyclicDelayDiversity(CDD)....................................................................................23

    2.7.1.4)SpaceFrequencyBlockCoding(SFBC)....................................................................25

    2.7.2)SpatialMultiplexing...................................................................................................26

    2.7.3)Beamforming............................................................................................................28

    Chapter3LTEDownlinkSystemModel..............................................................32

  • 2

    3.1)Introduction..................................................................................................................32

    3.2)GeneralDescription......................................................................................................33

    CHAPTER4RadioPropagationModels....................................................................36

    4.2.1)LargeScalePropagationModel.................................................................................39

    4.2.2)MediumScalePropagationModel............................................................................40

    4.2.3)SmallScalePropagationModel.................................................................................40

    4.3)PropagationaspectsandParameters...........................................................................41

    4.3.1)DelaySpread..............................................................................................................42

    4.3.2)CoherenceBandwidth...............................................................................................42

    4.3.3)DopplerSpread..........................................................................................................43

    4.3.4)CoherenceTime.........................................................................................................43

    4.4)StandardChannelmodels............................................................................................44

    4.4.1)SISO,SIMOandMISOChannelModels.....................................................................44

    4.4.2)MIMOChannelModels..............................................................................................45

    4.4.3)EffectofSpatialCorrelationonMIMOPerformance................................................46

    4.4.4)ITUMultipathChannelModels..................................................................................48

    4.4.4.2)ITUVehicularA(V30,V120andV350)...............................................................50

    4.4.5)ExtendedITUmodels.................................................................................................51

    Chapter5ChannelEstimationinLTE..........................................................................54

    5.1)Introduction..................................................................................................................54

    5.2)SignalModel.................................................................................................................54

    5.3)PilotassistedChannelEstimation.................................................................................56

    5.3.1)LeastSquareEstimation............................................................................................57

    5.3.2)RegularizedLSEstimation..........................................................................................58

    5.3.3)DownSamplingMethod............................................................................................58

    5.3.4)MinimumMeanSquareEstimation...........................................................................59

    5.4)Equalization..................................................................................................................60

    5.5)PerformanceComparisonofChannelEstimation........................................................62

    Schemes...............................................................................................................................62

    Chapter6ChannelEstimationforMultipleAntennaSystems....................................69

  • 3

    6.1)Introduction..................................................................................................................69

    6.2)SFBCinLTE....................................................................................................................70

    6.3)ChannelEstimationandDecoding................................................................................71

    6.4)NumericalResultsandPerformanceanalysis...............................................................73

    Chapter7Conclusions...................................................................................................78

    References.................................................................................................................