GMSK调制解调系统英文03Word文件下载.docx

GMSK调制解调系统英文03Word文件下载.docx

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BasedonGSMtechnologydevelopedbytheEuropeanTelecommunicationsStandardsInstitute（ETSI）specificationdevelopedbyGlobalCommunications（GSM）digitalcellularmobilesystems;

FormulatedbytheEuropeanPostandTelecommunicationsAssociation（CEPT）,EuropeanTelecommunicationsStandardstheETS1300a175CordlessTelecommunicationsstandard（DECT）;

TheUnitedKingdomandHongKong-basedcommunicationstandardforcordlessphones（CordlessPhones）andtelecommunicationspoints（Telepoint）system,CT-2andCT-3system;

BasedonEricsson'

sMobitexprotocol,Mobitexsystem（Europe）,andRAMMobileDataSystem（U.S.）;

EstablishmentofwirelessdataservicesintheNorthAmericanAdvancedMobilePhoneSystem（AMPS）CellularDigitalPacketData（CDPD）system;

Third-generationpersonalcommunicationssystems（PCs）,thethePCS1900oftheUnitedStatesbasedontheGSMstandard;

andEuropebyETISdevelopmentandestablishmentofpersonalcommunicationsnetwork（PCN）standardDCSI800;

AsthesystemoftheEuropeanwirelessLAN（WLAN）standardHiperLAN/1andmanynowdiscussedasawirelesspersonalareanetwork（WPAN）standardBluetooth（Bluetooth）;

AccordingtotheInternationalCivildirtyOrganization（ICAO）todevelopsatellitecommunications,navigation,search/airtrafficmanagement}ofCNS/ATM）systemandotherproprietarysystems;

GeneralPacketRadioService（GPRS）aswellasimproveddataratesforGSM（EDGE）ascommunicationstandardbythesecondgenerationtothirdgenerationcommunicationstandardtransitionprogramisGMSKasamodulationscheme;

In1999,theITUbegintobuildthird-generationwirelesscommunicationstandardforIMT2000system.Dividedintofivecategoriesaccordingtodifferentapplicationsandtechnologies:

（1）IMT-DS:

DirectSequenceSpreadSpectrumCDMAschemebasedontheETSIW-CDMAtechnology,;

（2）IMT-MC:

NorthAmerica-basedcdma-One（tm）multi-carrierCDMAtechnology;

（3）IMT-TC:

ETSITD-CDMAtechnology,thetimedivisionduplex（TDD）andTDMA/CDMAmultipleaccessmethods;

（4）IMT-SC:

basedontheUWC-136/EDGEnetwork;

（5）IMT-FT:

usingFDM.4-DECTtechnology.WhichthelatterthreetypesofwirelessinterfacemodulationGMSKtechnologyorcompatible.

Asnotedabove,GMSKhasawiderangeofapplications.Therefore,sincethetechnologyfromthe1980s,themajorityofresearcherscarriedoutalotofresearchforitsmodemprogram.

GMSKSignalModulationScheme

MinimumShiftKeying（MSK）

MSKiscontinuousphasefrequencyshiftkeying（CPFSK）inaspecialform.Modulationindexh=0.5,forthequadraturesignal,MSKwithinasymboltimeT,theminimumfrequencyoffset（assumingcoherentdemodulation）.MSKsignalcanalsoberegardedasthesinepulseformationofstaggeredquadraturephaseshiftkeying（ofOQPSK）.

Inordertomeettherequirementsofthewirelesscommunication,amodulationschemerequiresthefollowingfeatures:

Compacttheoutputpowerspectrum;

MeettheClassCnon-linearamplifier;

Hasastrongimmunitytonoiseandinterference;

Easytoimplement.

MSKManypropertiesaresatisfactory.Thismakesitverysuitableasawirelesscommunicationmodulationschemes.Italsohasitsownshortcomings,itspowerspectraldensityofthesidelobe.Inordertomakeitsoutputpowerspectrumismorecompact,weintroducetheconceptofpre-modulationlow-passfilter.

Gaussianminimumshiftkeying（GMSK）

InordertomaketheoutputpowerspectrumoftheMSKsignalismorecompact,theprefabricatedlow-passfiltershouldmeetthefollowingconditions:

Bandwidth,andhighfrequencycomponentsofsharpcut-off;

Correspondinglowerpulseisusedtopreventexcessiveinstantaneousfrequencydeviation;

Abletomaintaintheoutputimpulseresponseareaunderthecurvecorrespondstotheπ/2phase.

Asapulseformingfilter,GMSKmeettheaboveconditions,theGaussianfilter.DataflowthroughaGaussianlow-passfilter,andthentheMSKmodulation.Thefilterbandwidthisdeterminedbythetime-bandwidthconstantBT.Nocarrierdriftandadjacent-channel-bandradiatedpowerrelativetothetotalpowerlessthan-60dB,BT=0.28ismoresuitableforconventional（IEEE-definedbandof300~1,000MHz）mobilewirelesscommunicationsystems.Theintroductionofthepre-modulationfilterthesignalspectrumismorecompact,buthealsointhetimedomainbroadeningofthesignalpulse,theintroductionofinter-symbolinterference（ISI）.Specifically,themodulationfiltermakesthepulsebroadening,makingthewaveforminthetimedomainisgreaterthanthesymboltimeT,sowesometimesGMSKsignalinthepartoftheresponsesignal.

Gaussianlow-passfilterimpulseresponseh（t）canbeexpressedas：

（2-1）

Gaussianlow-passfiltersquarewavepulseresponseg（t）：

（2-2）

Rectangularfunctionrectis（x）isdefinedas：

（2-3）

Calculation,theimpulseresponseg（t）canbeexpressedas：

（2-4）

Amongthem,theQ（t）fortheQfunction：

（2-5）

Modulatedsignalphaseiswritten：

（2-6）

Whereisthemodulationofnon-zerocode（NRZ）.Modulationindexh=0.5.Thisensuresthatthegreatestchangeinvolumeofthephasewithinasymbol

.Therefore,theultimateexpressionoftheGMSKsignalis：

（2-7）

Amongthem,thesignalenergyperbitis

therandominitialphaseis

.Inordertofacilitatetheanalysis,undernormalcircumstances,wecanassumethat

=0.

GMSKmodulationsignalphasepath

Bytheformula2-5,wecaneasilyseethatthephaseoftheGMSKsignalpathimpulseresponsewaveformshapeofthedecision.Inotherwords,thevalueofasymbolofthemodulatedwavephasechangedependsonthepulseoftheareathemeantime.DuetotheintroductionoftheGaussianlow-passfilter,thebroadeningofthepulsewaveforminthetimedomain,makingtheoverlapbetweenadjacentpulses,indeterminingasymbolpulseareaistheneedtoconsidertheimpactoftheadjacentcode.Inthisway,differentstreampatterns,theareaof​​thepulsewithinasymbolcorrespondingtothephasepathisalsodifferent.

Therulesfordeterminingthephasepathis:

Codewithinoneyardsforthechangetoincreaseordecrease,dependingontheareaof​​positiveandnegativepolaritypulsewaveformsuperimposedcode.Iftheareaispositive,thisphaseincrease,andviceversareduced.

Acodephasechangedependsonthepulseareathesizeofthiscodewithintheoverlay.（Pulsewidthforthe3T,forexample）whentheadjacentthreeyardsof+1,+1,+1,acodephasebyπ/2;

adjacent3yardsto-1,phasetoreducethesymbolπ/2;

otherstreammap,superimposeduponthepulseareaissmallerthantheabovetwocases,duetothepolarityoffsetislessthanπ/2phasechanges.

Digitalsignalpowerspectraldensity

Makeadigitalphasemodulationsignalsasfollows：

（2-8）

Amongthem,

isarandomprocesscontainsinformation,whichisthephasepath.

istheinitialphase（theanalysiscanbesetto0）.Thepowerspectrumanalysismethodmoreandhavetheirowncharacteristicsanduses.Themainmethodisprobablythefollowing:

ThedirectFouriertransformmethod.ThroughdirectDerivingZ（t）theFouriertransformofthetruncatedsignalforitsamplitudespectrum.Andthenusethestatisticalcharacteristicsofsymbolsaswellasthebasicprincipleofstationaryrandomprocesstobetranslatedintothepowerspectrum.Thisisthewaytodeterminethedirectclassicalmethodsofsignalspectralanalysisofthetransitiontotherandomsignal.

Correlationfunctionmethod.Wiener-XinXinTheoremFouriertransformtoobtainthepowerspectrumusingtheautocorrelationfunctionisestimatedworth.

Thetransitionprobabilitymethod（signalflowgraphmethod）.Listedfirstsymbolofthetransferofstateandcalculatethecorrespondingtransitionprobabilitymatrix,andthenusethatcontainsthetransitionprobabilityofthepowerspectraldensityanalysistypedirectlytocalculatethepowerspectraldistribution.

Othermodernspectrumestimation.Maximumentropymethod,likethenaturalspectrumestimation,autoregressivespectralestimation.

Describedabove,thedirectmethod.ThemethodusesatruncatedformofbandpasssignalZ（t）obtaineddirectlybilateralpowerspectrumofthedegreeofZ（t）.GMSKsignalpowerspectraldensityisthesame,withthedecreaseofBTco