ETSI EN 300 938 V8.0.1 (2000-09)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2+) (GSM); Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 8.0.1 Release 1999)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 300 938 Version 8.0.1SIST EN 300 938 V8.0.1:2003en01-december-2003SIST EN 300 938 V8.0.1:2003SLOVENSKI
STANDARD
ETSIEN300938V8.0.1(2000-09)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interface;DataLink(DL)layerspecification(GSM04.06version8.0.1Release1999)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)2(GSM04.06version8.0.1Release1999)ReferenceREN/SMG-020406Q8KeywordsDigitalcellulartelecommunicationssystem,GlobalSystemforMobilecommunications(GSM)ETSI650RoutedesLuciolesF-06921SophiaAntipolisCedex-FRANCETel.:+33492944200Fax:+33493654716SiretN°34862356200017-NAF742CAssociationàbutnonlucratifenregistréeàlaSous-PréfecturedeGrasse(06)N°7803/88ImportantnoticeIndividualcopiesofthepresentdocumentcanbedownloadedfrom:http://www.etsi.orgThepresentdocumentmaybemadeavailableinmorethanoneelectronicversionorinprint.Inanycaseofexistingorperceiveddifferenceincontentsbetweensuchversions,thereferenceversionisthePortableDocumentFormat(PDF).Incaseofdispute,thereferenceshallbetheprintingonETSIprintersofthePDFversionkeptonaspecificnetworkdrivewithinETSISecretariat.Usersofthepresentdocumentshouldbeawarethatthedocumentmaybesubjecttorevisionorchangeofstatus.InformationonthecurrentstatusofthisandotherETSIdocumentsisavailableathttp://www.etsi.org/tb/status/Ifyoufinderrorsinthepresentdocument,sendyourcommentto:editor@etsi.frCopyrightNotificationNopartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)3(GSM04.06version8.0.1Release1999)ContentsIntellectualPropertyRights.7Foreword.70Scope.80.1References.80.2Abbreviations.81General.91.1Options.92Framestructureforpeer-to-peercommunication.102.1General.102.2Framedelimitationandfillbits.122.3Addressfield.122.4Controlfield.132.5Lengthindicatorfield.132.5aShortL2headertype1.132.6Informationfield.132.7Transparency.132.8Formatconvention.132.8.1Numberingconvention.132.8.2Orderofbittransmission.132.8.3Fieldmappingconvention.133ElementsofproceduresandformatsoffieldsforDataLinkLayerpeer-to-peercommunication.143.1General.143.2Addressfieldformat.143.3Addressfieldvariables.153.3.1Addressfieldextensionbit(EA).153.3.2Command/responsefieldbit(C/R).153.3.3Serviceaccesspointidentifier(SAPI).153.4Controlfieldformats.153.4.1Informationtransferformat-I.153.4.2Supervisoryformat-S.163.4.3Unnumberedformat-U.163.4aShortL2headertype1.163.5Controlfieldparametersandassociatedstatevariables.163.5.1Poll/Finalbit.163.5.2Multipleframeoperation-variablesandsequencenumbers.173.5.2.1Modulus.173.5.2.2SendstatevariableV(S).173.5.2.3AcknowledgestatevariableV(A).173.5.2.4SendsequencenumberN(S).173.5.2.5ReceivestatevariableV(R).173.5.2.6ReceivesequencenumberN(R).173.5.2.7Otherparametersandvariables.183.5.3Unacknowledgedoperationvariablesandparameters.183.6Lengthindicatorfieldformat.183.7Lengthindicatorfieldvariables.183.7.1Lengthindicatorfieldextensionbit(EL).183.7.2Moredatabit(M).183.7.3Lengthindicator(L).183.8Commandsandresponses.193.8.1Information(I)commands.193.8.2Setasynchronousbalancedmode(SABM)command.193.8.3Disconnect(DISC)command.203.8.4Unnumberedinformation(UI)command.203.8.5Receiveready(RR)command/response.20SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)4(GSM04.06version8.0.1Release1999)3.8.6Reject(REJ)command/response.213.8.7Receivenotready(RNR)command/response.213.8.8Unnumberedacknowledgement(UA)response.213.8.9Disconnectedmode(DM)response.214Elementsforlayer-to-layercommunication.224.1Definitionofprimitivesandparameters.224.1.1Genericnames.224.1.1.1DL-ESTABLISH.224.1.1.2DL-RELEASE.224.1.1.3DL-DATA.224.1.1.4DL-UNITDATA.224.1.1.5DL-SUSPEND.224.1.1.6DL-RESUME.224.1.1.7DL-RECONNECT.234.1.1.8DL-RANDOMACCESS.234.1.1.9MDL-RELEASE.234.1.1.10MDL-ERROR.234.1.1.11PH-DATA.234.1.1.12PH-RANDOMACCESS.234.1.1.13PH-CONNECT.234.1.1.14PH-READY-TO-SEND.234.1.1.15PH-EMPTY-FRAME.234.1.2Primitivestypes.234.1.2.1REQUEST.244.1.2.2INDICATION.244.1.2.3RESPONSE.244.1.2.4CONFIRM.244.1.3Parameterdefinition.254.1.3.1Messageunit.254.1.3.2Channeltype.254.1.3.3ServiceAccessPoint.254.1.3.4Releasemode.254.1.3.5Errorcause.254.1.3.6Establishmode.264.1.3.7L2headertype.264.1.3.8Priority.264.2Primitiveprocedures.305Definitionofthepeer-to-peerprotocolLAPDm.305.1General.305.2GeneralProtocolProcedures.315.2.1Unacknowledgedinformationtransfer.315.2.2Acknowledgedmultipleframeinformationtransfer.325.3Proceduresforunacknowledgedinformationtransfer.325.3.1General.325.3.2Transmissionofunacknowledgedinformation.325.3.3Receiptofunacknowledgedinformation.325.4Proceduresforestablishmentandreleaseofmultipleframeoperation.325.4.1Establishmentofmultipleframeoperation.325.4.1.1General.325.4.1.2Normalestablishmentprocedures.335.4.1.3ProcedureonexpiryoftimerT200:Normalestablishment.345.4.1.4Contentionresolutionestablishmentprocedure.345.4.1.5ProcedureonexpiryoftimerT200:contentionresolution(MSonly).365.4.2Informationtransfer.365.4.2.1Generalrequirements.365.4.2.2Errorconditions.365.4.2.3Fillframes.375.4.3Suspensionandresumptionofmultipleframeoperation.385.4.3.1General.385.4.3.2Suspension.38SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)5(GSM04.06version8.0.1Release1999)5.4.3.3Resumption.395.4.3.3.1Procedureafterchannelchange.395.4.3.3.2Procedureafterreturningtotheoldchannel(MSonly).395.4.4Terminationofmultipleframeoperation.405.4.4.1General.405.4.4.2Normalreleaseprocedure.405.4.4.3ProcedureonexpiryoftimerT200fornormalrelease.405.4.4.4Localendreleaseprocedure.415.4.5Idlestate.415.4.6Collisionofunnumberedcommandsandresponses.415.4.6.1Identicaltransmittedandreceivedcommands.415.4.6.2Differenttransmittedandreceivedcommands.425.4.6.3UnsolicitedDMresponseandSABMorDISCcommand.425.5Proceduresforinformationtransferinmultipleframeoperation.425.5.1TransmittingIframes.425.5.2ReceivingIframes.435.5.2.1PbitofthereceivedIframesetto"1".435.5.2.2PbitofthereceivedIframesetto"0".435.5.3Receivingacknowledgement.445.5.3.1OnreceiptofavalidIframe.445.5.3.2ReceivingsupervisorycommandframeswiththePbitsetto"1".445.5.4ReceivingREJframes.445.5.4.1ReceiptofavalidREJframe.445.5.4.2Transmittingframes.455.5.5ReceivingRNRframe.455.5.6Datalinklayerownreceiverbusycondition.465.5.7Waitingacknowledgement.475.5.8Preemption.475.5.8.1SenderRequirements.485.5.8.2ReceiverRequirements.485.6Abnormalreleaseandre-establishmentofmultipleframeoperation.485.6.1Criteriaforre-establishment.485.6.2Criteriaforabnormalrelease.485.6.3Proceduresforre-establishment.495.6.4Proceduresforabnormalrelease.495.7Exceptionconditionreportingandrecoveryformultipleframeoperation.495.7.1N(S)sequenceerror.495.7.2Timerrecovery.505.7.3Invalidframecondition.505.7.4N(R)sequenceerror.505.8Listofsystemparameters.505.8.1TimerT200.515.8.1.1ForSAPI=0andSAPI=3.515.8.1.2ForSAPIsotherthan0or3.515.8.2Maximumnumberofretransmissions(N200).515.8.2.1ForSAPI=0and3.515.8.2.2ForSAPIsotherthan0or3.515.8.3MaximumnumberofoctetsinanI,UI,SABMandUAframepartiallyorentirelyavailablefortheinformationfield(N201).515.8.4MaximumnumberofoutstandingIframes(k).525.8.5MaximumnumberofoctetsinaLayer3message.525.9Systemperformancerequirements.526SpecialprotocoloperationonSAPI=0andSAPI=3.53AnnexA(normative):Randomaccessprocedures.54A.1Descriptionoftheprocedure.54A.1.1ProcedureintheMS.54A.1.2ProcedureintheBS.54SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)6(GSM04.06version8.0.1Release1999)A.2Format.54AnnexG(normative):Handlingofframeswithparametererrorsintheaddress,controlandlengthindicatorfields.55G.1General.55G.2Parametererrorsintheaddressfield.55G.2.1UnallocatedSAPI.55G.2.2WrongvalueoftheC/Rbit.55G.2.3EAbitsetto"0".55G.3Parametererrorsinthecontrolfield.56G.3.1Supervisoryframes.56G.3.2Unnumberedframes.56G.4Parametererrorsinthelengthindicatorfield.56G.4.1ELbiterror.56G.4.2Informationframes.56G.4.3Supervisoryframes.57G.4.4DISCandDMframes.57G.4.5SABMUAandUIframes.57AnnexH(informative):ChangeRequestHistory.58History.59SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)7(GSM04.06version8.0.1Release1999)IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinETSISR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinETSISR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbyETSITechnicalCommitteeSpecialMobileGroup(SMG).ThepresentdocumentdefinesthedatalinklayerprotocoloftheMobileStation-BaseStationSystem(MS-BSS)interfacewithinthedigitalcellulartelecommunicationssystem.ThecontentsofthepresentdocumentissubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocument,itwillbere-releasedwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version8.x.ywhere:8indicatesRelease1999ofGSMPhase2+.xtheseconddigitisincrementedforallchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.ThespecificationfromwhichthepresentdocumenthasbeenderivedwasoriginallybasedonCEPTdocumentation,hencethepresentationofthepresentdocumentmaynotbeentirelyinaccordancewiththeETSIdraftingrules.AnnexesBtoFweredeletedfromtheoriginalspecification,however,forreferencingpurposestheannexnumberinghasbeenmaintained.NationaltranspositiondatesDateofadoptionofthisEN:25August2000DateoflatestannouncementofthisEN(doa):30November2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31May2001DateofwithdrawalofanyconflictingNationalStandard(dow):31May2001SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)8(GSM04.06version8.0.1Release1999)0ScopeThepresentdocumentdefinesadatalinklayerprotocoltobeusedforsignalling,andpossiblyalsoforotherapplications,ontheMS-BSinterface.0.1ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.• ForthisRelease1999document,referencestoGSMdocumentsareforRelease1999versions(version8.x.y).[1]GSM01.04:"Digitalcellulartelecommunicationssystem(Phase2+);Abbreviationsandacronyms".[2]GSM04.01:"Digitalcellulartelecommunicationssystem;MobileStation-BaseStationSystem(MS-BSS)interface;Generalaspectsandprinciples".[3]GSM04.03:"Digitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interfaceChannelstructuresandaccesscapabilities".[4]GSM04.04:"Digitalcellulartelecommunicationssystem;Layer1Generalrequirements".[5]GSM04.05:"Digitalcellulartelecommunicationssystem;DataLink(DL)layerGeneralaspects".[6]GSM04.07:"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacesignallinglayer3;Generalaspects".[7]GSM04.08:"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacelayer3specification".[8]GSM04.10:"Digitalcellulartelecommunicationssystem;Mobileradiointerfacelayer3Supplementaryservicesspecification;Generalaspects".[9]GSM04.12:"Digitalcellulartelecommunicationssystem(Phase2+);ShortMessageServiceCellBroadcast(SMSCB)supportonthemobileradiointerface".[10]GSM05.02:"Digitalcellulartelecommunicationssystem(Phase2+);Multiplexingandmultipleaccessontheradiopath".[11]GSM08.56:"Digitalcellulartelecommunicationssystem;BaseStationController-BaseTransceiverStation(BSC-BTS)interface;Layer2specification".[12]GSM08.58:"Digitalcellulartelecommunicationssystem(Phase2+);BaseStationController-BaseTransceiverStation(BSC-BTS)interface;Layer3specification".[13]CCITTRecommendationZ.100:"Specificationanddescriptionlanguage(SDL)".0.2AbbreviationsAbbreviationsusedinthepresentdocumentarelistedinGSM01.04.SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)9(GSM04.06version8.0.1Release1999)1GeneralThepresentdocumentdescribestheframestructure,elementsofprocedure,formatoffieldsandproceduresfortheproperoperationoftheLinkAccessProcedureontheDmchannel,LAPDm.NOTE1:ThetermDmchannelisusedforconveniencetodesignatethecollectionofallthevarioussignallingchannelsrequiredintheGSMsystem.SeealsoGSM04.03.Theconcepts,terminology,overviewdescriptionofLAPDmfunctionsandprocedures,andtherelationshipwithotherTechnicalSpecificationsaredescribedingeneraltermsinGSM04.05.TheframeformatsdefinedforLAPDmarebasedonthosedefinedforLAPD.However,thereareimportantdifferencesbetweenLAPDmandLAPD,inparticularwithregardtoframedelimitationmethodsandtransparencymechanisms.Thesedifferencesarenecessaryforoperationwithintheconstraintssetbytheradiopath.LAPDmsupportstwomodesofoperation:-unacknowledgedoperationusingUIframes;-acknowledgedoperationusingthemultipleframeprocedure.Asachoiceofimplementation,thetwomodesofoperationmaybeimplementedindependentlyofeachother.Thisispossiblesincethereisnointeractionsbetweenthetwomodes,otherthanqueuingatthetransmitter,evenwhentheycoexistonthesamephysicalchannel.ForBCCHsandCCCHsonlytheunacknowledgedmodeofoperationneedstobeimplemented.LAPDmisusedforinformationsentonthecontrolchannelsBCCH,AGCH,NCH,PCH,FACCH,SACCHandSDCCHasdefinedinGSM04.03.NOTE2:AGCH,NCHandPCHaresometimesreferredtobythecollectivenameCCCHandFACCH,SACCHandSDCCHare,similarly,referredtobythecollectivenameDCCH.LAPDmmayalsobeusedonothertypesofchannel.NOTE3:AsstatedinGSM04.05,theterm"datalinklayer"isusedinthemaintextofthisTechnicalSpecification.However,mainlyinfiguresandtables,theterms"layer2"and"L2"areusedasabbreviations.Furthermore,inaccordancewithGSM04.07andGSM04.08,theterm"layer3"isusedtoindicatethelayerabovethedatalinklayer.ThisTechnicalSpecificationisorganizedasfollows:Theframestructureforpeer-to-peercommunicationisgiveninclause2.Theelementsofprocedureandformatsoffieldsaregiveninclause3.Theelementsoflayer-to-layercommunicationarecontainedinclause4.Thedetailsofthepeer-to-peerproceduresaregiveninclause5.Section6summarizesthespecialprotocoloperationsusedmandatorilywithSAPI=0andSAP=3.ThespecificationfortherandomaccesschanneliscontainedinannexA,eventhoughitisnotaLAPDmfunction.Thepresentdocumentisdescriptiveanddoesnotconstraintheimplementationoftherandomaccessfunction.TheprocedureisusedforCHANNELREQUESTontheRACHandHANDOVERACCESSonthemainDCCH.(AnnexesBtoFaredeleted).AnnexGgivesanoverviewofactionstakenonframescontainingparametererrors.1.1OptionsSupportofshortL2headertype1isanoptioninboththemobilestationandthenetwork;undercertainconditionsthesupportismandatory,asspecifiedinotherSpecifications.Alayer2protocolentitynotimplementingshortL2headertype1shalldiagnoseanE/AbiterrorandproceedasdefinedinannexG.2.3.SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)10(GSM04.06version8.0.1Release1999)2Framestructureforpeer-to-peercommunication2.1GeneralAlldatalinklayerpeer-to-peerexchangesareinframesconformingtooneoftheformatsshowninfigure1.Severalformattypesareshowninthefigure:-FormatAisusedonDCCHsforframeswherethereisnoinformationfield.-FormatsB,BterandB4areusedonDCCHsforframescontaininganinformationfield:-formatBterisusedonrequestofhigherlayersifandonlyifshortL2headertype1issupportedandaUIcommandistobetransmittedonSAPI0;-formatB4isusedforUIframestransmittedbythenetworkonSACCH;-formatBisappliedinallothercases.-FormatBbisisusedonlyonBCCH,PCH,NCH,andAGCH.-InadditionthereisaFormatCfortransmissionofrandomaccesssignals.FormatCframesaredescribedinannexA.FormatA,B,Bbis,BterandB4framesaredescribedintheremainderofthepresentdocument.Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Fillbits:N201+nFormattypeAFigure1/GSM04.06(sheet1of3):GeneralframeformatsSIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)11(GSM04.06version8.0.1Release1999)Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Informationfield:NN+1:Fillbits:N201+nFormattypeBBit87654321OctetNo1:::Informationfield:::N201FormattypeBbisFigure1/GSM04.06(sheet2of3):GeneralframeformatsSIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)12(GSM04.06version8.0.1Release1999)Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Informationfield:N201+k+1FormattypeB4Bit87654321OctetNoshortL2headertype112:Informationfield:::N201FormattypeBterFigure1/GSM04.06(sheet3of3):GeneralframeformatsTheparameterN201isthemaximumnumberofoctetswhicharepartiallyorentirelyavailablefortheinformationfieldofaframe.Itdependsonthetypeofchannelandtheformat,seesubclause5.8.3.2.2FramedelimitationandfillbitsFramedelimitationisprovidedbythephysicallayer:-informattypeA,BandB4framesatthebeginningoftheframefordeterminingthestartofthefirstoctetintheaddressfield,informattypeBterframesfordeterminingthestartoftheoctetcontainingtheshortL2headertype1(whichisalsothefirstoctetusedfortheinformationfield),andinformattypeBbisframesfordeterminingthestartofthefirstoctetfortheinformationfield;-attheendoftheframefordeterminingthelastbitoftheframe.Theendoftheusefulpartoftheframe,i.e.theendofthelengthindicatorfieldintypeAframesandtheendoftheinformationfieldintypeBframes,isdeterminedbyalengthindicatorcontainedinthelengthindicatorfield.TheusefulpartofaBbisframestakesallN201octetsofthatframe.TheusefulpartofaBterframetakesallN201octetsofthatframeexceptthosebitsofoctet1whichcontaintheshortL2headertype1.TheusefulpartofaB4frametakesallN201octetsofthatframeexceptthoseoctetswhichcontaintheaddressfieldandthecontrolfield.IfaframecontainsalengthindicatorhasavaluelessthanN201,theframecontainsfillbits.Octetscontainingfillbitsshalltakethebinaryvalue"00101011",whensentbythenetwork.Octetscontainingfillbitsshalltakethevalue"00101011"or"11111111",whensentbythemobilestation.NOTE:Thevalue"00101011"ischosenduetothemodulationandinterleavingschemeusedintheGSMsystem.2.3AddressfieldTheaddressfieldmayconsistofavariablenumberofoctets.However,forapplicationsoncontrolchannelsthefieldconsistsofonlyoneoctet.TheaddressfieldidentifiestheSAPforwhichacommandframeisintendedandtheSAPtransmittingaresponseframe.Theformatoftheaddressfieldisdefinedinsubclause3.2.SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)13(GSM04.06version8.0.1Release1999)2.4ControlfieldThecontrolfieldconsistsofoneoctet.Theformatofthecontrolfieldisdefinedinsubclause3.4.2.5LengthindicatorfieldThelengthindicatorfieldmayconsistofavariablenumberofoctets.However,forapplicationsoncontrolchannelsthefieldconsistsofonlyoneoctet.Theformatofthefieldisdefinedinsubclause3.6.2.5aShortL2headertype1TheshortL2headertype1consistsoftwobits.Itscontentsaredefinedinsubclause3.4a.2.6InformationfieldTheinformationfieldofaframe,whenpresent,hasthepositionintheframedefinedin2.1.Themaximumnumberofoctetsintheinformationfield(N201)isdefinedinsubclause5.8.3.2.7TransparencyBecauseoftheframedelimitationtechniqueused(seesubclause2.2),theframecanincludeanypossiblesequenceofbitswithouttheneedforadditionaltransparencymechanisms.2.8Formatconvention2.8.1NumberingconventionThebasicconventionusedinthisTechnicalSpecificationisillustratedinfigure2.Thebitsaregroupedintooctets.Thebitsofanoctetareshownhorizontallyandarenumberedfrom1to8.Multipleoctetsareshownverticallyandarenumberedfrom1ton.Bit87654321Octetno12;;nFigure2/GSM04.06:Formatconvention2.8.2OrderofbittransmissionTheorderofbittransmissionisdefinedinGSM04.04.2.8.3FieldmappingconventionWhenafieldiscontainedwithinasingleoctet,thelowestbitnumberofthefieldrepresentsthelowestordervalue.Whenafieldspansmorethanoneoctet,theorderofbitvalueswithineachoctetprogressivelydecreasesastheoctetnumberincreases.Inthatpartofthefieldcontainedinagivenoctetthelowestbitnumberrepresentsthelowestordervalue.SIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)14(GSM04.06version8.0.1Release1999)Forexample,abitnumbercanbeidentifiedasacouple(o,b)whereoistheoctetnumberandbistherelativebitnumberwithintheoctet.Figure3illustratesafieldthatspansfrombit(1,3)tobit(2,7).Thehighorderbitofthefieldismappedonbit(1,3)andtheloworderbitismappedonbit(2,7).Bit876543214321stoctetfield222102ndoctetfield22Figure3/GSM04.06:Fieldmappingconvention3ElementsofproceduresandformatsoffieldsforDataLinkLayerpeer-to-peercommunication3.1GeneralTheelementsofproceduresdefinethecommandsandresponsesthatareusedonthedatalinkconnectionscarriedontheDmchannel.Proceduresarederivedfromtheseelementsofproceduresandaredescribedinclause5.Ifabitpositionismarkedas"spare",itshallbecodedas"0".Forfuturecompatibilityreasons,anentityreceivingframes,wheresparebitpositionsarecodedotherwise,shallignorethosevalueswithoutnotificationofanyerror.3.2AddressfieldformatThefieldconsistsof:-theaddressfieldextensionbitEA;-thecommand/responsebitC/R;-theSAPI;-andtheLinkProtocolDiscriminatorLPD.Theformatoftheaddressfieldforcontrolchannelsisshowninfigure4.Theaddressfieldextensionbit,EA,enablesextensionofthefieldtospanmorethanoneoctet.Thevalue"0"isusedtoindicateanextension,thevalue"1"shallbeusedforthefinaladdressfieldoctet.TheLinkProtocolDiscriminator(LPD)correspondingtotheuseinthisTechnicalSpecificationshalltakethevalue"00",allothervaluesarereserved.NOTE:LPD="01"correspondstothedatalinkprotocolusedforSMSCB(seeGSM04.12).Bit87654321SpareLPDSAPIC/REA=1Figure4/GSM04.06:AddressfieldformatSIST EN 300 938 V8.0.1:2003

ETSIETSIEN300938V8.0.1(2000-09)15(GSM04.06version8.0.1Release1999)3.3Addressfieldvariables3.3.1Addressfieldextensionbit(EA)Theaddressfieldrangeisextendedbyreservingthefirsttransmittedbitoftheaddressfieldoctetstoindicatethefinaloctetoftheaddressfield.Thepresenceofa"1"inthefirstbitofanaddressfieldoctetsignalsthatitisthefinaloctetoftheaddressfield.Figure4showsthecasewherethefieldconsistsofoneoctet.3.3.2Command/responsefieldbit(C/R)TheC/Rbitidentifiesaframeaseitheracommandoraresponse.TheMSsideshallsendcommandswiththeC/Rbitsetto"0",andresponseswiththeC/Rbitsetto"1".TheBSsideshalldotheopposite;thatiscommandsaresentwithC/Rsetto"1",and
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