SIST ETS 300 938 E5:2003

• Abstract:

  CR SMG#31

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.070.50 - Global System for Mobile Communication (GSM)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI ETS 300 938 ed.5 (2000-09) - Digital cellular telecommunications system (Phase 2+) (GSM); Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 5.4.1 Release 1996)

Overview

SIST ETS 300 938 E5:2003 specifies the data link (DL) layer protocol for the Mobile Station to Base Station System (MS-BSS) interface within the digital cellular telecommunications system (GSM Phase 2+). Developed by the Slovenski inštitut za standardizacijo (SIST), this standard is harmonized with the European ETS 300 938 and is part of GSM Release 1996, version 5.4.1. The document defines the structures, field formats, and operational procedures that enable reliable peer-to-peer and layer-to-layer data transfer over GSM control and traffic channels.

Key Topics

• Data Link Layer Protocols: The standard defines the Link Access Procedure on the Dm channel (LAPDm), which is the protocol responsible for reliable data link operations between the mobile and the base station.
• Frame Structure: Various frame formats (Types A, B, Bbis, Bter, B4, C) are outlined to address different communication scenarios and channel types within GSM.
• Address and Control Fields: Fields such as the address field (including Service Access Point Identifier, or SAPI), control field (defining commands, responses, and sequencing), and length indicator are standardized.
• Operational Modes: LAPDm supports both acknowledged (using multiple frame procedures) and unacknowledged modes (UI frames). These modes may be implemented independently depending on network requirements.
• Procedure Elements: The standard details commands and responses, such as information transfer, supervisory functions, connection establishment, and release procedures.

Applications

• GSM Radio Interface: The standard is essential for the implementation of the MS-BSS interface in GSM Phase 2+ mobile networks, ensuring interoperability and reliability in mobile communications.
• Signalling Channels: LAPDm is applied to both broadcast control channels (BCCH), common control channels (CCCH), and dedicated control channels (DCCH), facilitating signalling and short message services.
• Telecommunication Infrastructure: Equipment manufacturers, mobile operators, and network integrators use this standard to develop base stations, mobile devices, and associated network components that comply with GSM protocols.

Practical Value

• Interoperability: Uniform data link procedures ensure compatibility between mobile devices and base stations from different vendors.
• Reliable Communication: The specification of error detection, sequencing, and acknowledgement mechanisms within LAPDm is critical for maintaining robust communication links, especially over unreliable radio channels.
• Network Efficiency: By standardizing operational modes and frame structures, the protocol optimizes the usage of GSM network resources for both signalling and data transfer.

Related Standards

• GSM 04.01 & GSM 04.03: Define general aspects and channel structures for MS-BSS interface.
• GSM 04.05: Outlines general requirements for the data link layer.
• GSM 04.07 & GSM 04.08: Specify higher layer signalling requirements for mobile radio interface.
• GSM 05.02: Covers multiplexing and multiple access on the radio path.
• GSM 08.56 & GSM 08.58: Address data link and layer 3 specifications for Base Station Controller-Base Transceiver Station interfaces.

Summary

SIST ETS 300 938 E5:2003 is a foundational GSM standard that ensures the integrity and interoperability of the data link layer of the MS-BSS interface in mobile telecommunications. By closely defining protocol elements, frame structures, and operational procedures, it enables the global deployment of reliable GSM networks, serving as a core reference for professionals in telecommunications engineering, infrastructure deployment, and network device manufacturing. Adherence to this standard is crucial for achieving seamless mobile station and base station communication across diverse GSM infrastructures.

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 5.4.1 Release 1996)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:ETS 300 938 Edition 5SIST ETS 300 938 E5:2003en01-december-2003SIST ETS 300 938 E5:2003SLOVENSKI
STANDARD
EUROPEANETS300938TELECOMMUNICATIONAugust2000STANDARDFifthEditionSource:SMGReference:RE/SMG-030406QR3ICS:33.020Keywords:Digitalcellulartelecommunicationssystem,GlobalSystemforMobilecommunications(GSM)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRDigitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interface;DataLink(DL)layerspecification(GSM04.06version5.4.1Release1996)ETSIEuropeanTelecommunicationsStandardsInstituteETSISecretariatPostaladdress:F-06921SophiaAntipolisCEDEX-FRANCEOfficeaddress:650RoutedesLucioles-SophiaAntipolis-Valbonne-FRANCEInternet:[e-mail]-http://www.etsi.orgTel.:[phone]-Fax:[phone]CopyrightNotification:Nopartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST ETS 300 938 E5:2003

Page2ETS300938(GSM04.06version5.4.1Release1996):August2000Whilsteverycarehasbeentakeninthepreparationandpublicationofthepresentdocument,errorsincontent,typographicalorotherwise,mayoccur.Ifyouhavecommentsconcerningitsaccuracy,pleasewriteto"ETSIStandardsMakingSupportDept."attheaddressshownonthetitlepage.SIST ETS 300 938 E5:2003

Page3ETS300938(GSM04.06version5.4.1Release1996):August2000ContentsIntellectualPropertyRights.7Foreword.70Scope.90.1Normativereferences.90.2Abbreviations.91General.101.1Options.102Framestructureforpeer-to-peercommunication.112.1General.112.2Framedelimitationandfillbits.132.3Addressfield.142.4Controlfield.142.5Lengthindicatorfield.142.5aShortL2headertype1.142.6Informationfield.142.7Transparency.142.8Formatconvention.142.8.1Numberingconvention.142.8.2Orderofbittransmission.152.8.3Fieldmappingconvention.153ElementsofproceduresandformatsoffieldsforDataLinkLayerpeer-to-peercommunication.153.1General.153.2Addressfieldformat.163.3Addressfieldvariables.163.3.1Addressfieldextensionbit(EA).163.3.2Command/responsefieldbit(C/R).163.3.3Serviceaccesspointidentifier(SAPI).163.4Controlfieldformats.173.4.1Informationtransferformat-I.173.4.2Supervisoryformat-S.173.4.3Unnumberedformat-U.173.4aShortL2headertype1.183.5Controlfieldparametersandassociatedstatevariables.183.5.1Poll/Finalbit.183.5.2Multipleframeoperation-variablesandsequencenumbers.183.5.2.1Modulus.183.5.2.2SendstatevariableV(S).183.5.2.3AcknowledgestatevariableV(A).183.5.2.4SendsequencenumberN(S).193.5.2.5ReceivestatevariableV(R).193.5.2.6ReceivesequencenumberN(R).193.5.2.7Otherparametersandvariables.193.5.3Unacknowledgedoperationvariablesandparameters.193.6Lengthindicatorfieldformat.193.7Lengthindicatorfieldvariables.203.7.1Lengthindicatorfieldextensionbit(EL).203.7.2Moredatabit(M).203.7.3Lengthindicator(L).203.8Commandsandresponses.203.8.1Information(I)commands.203.8.2Setasynchronousbalancedmode(SABM)command.21SIST ETS 300 938 E5:2003

Page4ETS300938(GSM04.06version5.4.1Release1996):August20003.8.3Disconnect(DISC)command.223.8.4Unnumberedinformation(UI)command.223.8.5Receiveready(RR)command/response.223.8.6Reject(REJ)command/response.233.8.7Receivenotready(RNR)command/response.233.8.8Unnumberedacknowledgement(UA)response.233.8.9Disconnectedmode(DM)response.234Elementsforlayer-to-layercommunication.244.1Definitionofprimitivesandparameters.244.1.1Genericnames.244.1.1.1DL-ESTABLISH.244.1.1.2DL-RELEASE.244.1.1.3DL-DATA.244.1.1.4DL-UNITDATA.244.1.1.5DL-SUSPEND.244.1.1.6DL-RESUME.244.1.1.7DL-RECONNECT.254.1.1.8DL-RANDOMACCESS.254.1.1.9MDL-RELEASE.254.1.1.10MDL-ERROR.254.1.1.11PH-DATA.254.1.1.12PH-RANDOMACCESS.254.1.1.13PH-CONNECT.254.1.1.14PH-READY-TO-SEND.254.1.1.15PH-EMPTY-FRAME.254.1.2Primitivestypes.254.1.2.1REQUEST.254.1.2.2INDICATION.264.1.2.3RESPONSE.264.1.2.4CONFIRM.264.1.3Parameterdefinition.264.1.3.1Messageunit.264.1.3.2Channeltype.274.1.3.3ServiceAccessPoint.274.1.3.4Releasemode.274.1.3.5Errorcause.274.1.3.6Establishmode.274.1.3.7L2headertype.274.2Primitiveprocedures.315Definitionofthepeer-to-peerprotocolLAPDm.325.1General.325.2GeneralProtocolProcedures.335.2.1Unacknowledgedinformationtransfer.335.2.2Acknowledgedmultipleframeinformationtransfer.335.3Proceduresforunacknowledgedinformationtransfer.335.3.1General.335.3.2Transmissionofunacknowledgedinformation.335.3.3Receiptofunacknowledgedinformation.335.4Proceduresforestablishmentandreleaseofmultipleframeoperation.345.4.1Establishmentofmultipleframeoperation.345.4.1.1General.345.4.1.2Normalestablishmentprocedures.345.4.1.3ProcedureonexpiryoftimerT200:Normalestablishment355.4.1.4Contentionresolutionestablishmentprocedure.355.4.1.5ProcedureonexpiryoftimerT200:contentionresolution(MSonly).375.4.2Informationtransfer.375.4.2.1Generalrequirements.375.4.2.2Errorconditions.385.4.2.3Fillframes.395.4.3Suspensionandresumptionofmultipleframeoperation.39SIST ETS 300 938 E5:2003

Page5ETS300938(GSM04.06version5.4.1Release1996):August20005.4.3.1General.395.4.3.2Suspension.405.4.3.3Resumption.405.4.3.3.1Procedureafterchannelchange.405.4.3.3.2Procedureafterreturningtotheoldchannel(MSonly).415.4.4Terminationofmultipleframeoperation.425.4.4.1General.425.4.4.2Normalreleaseprocedure.425.4.4.3ProcedureonexpiryoftimerT200fornormalrelease.425.4.4.4Localendreleaseprocedure.435.4.5Idlestate.435.4.6Collisionofunnumberedcommandsandresponses.435.4.6.1Identicaltransmittedandreceivedcommands.435.4.6.2Differenttransmittedandreceivedcommands.445.4.6.3UnsolicitedDMresponseandSABMorDISCcommand.445.5Proceduresforinformationtransferinmultipleframeoperation.445.5.1TransmittingIframes.445.5.2ReceivingIframes.455.5.2.1PbitofthereceivedIframesetto"1".455.5.2.2PbitofthereceivedIframesetto"0".455.5.3Receivingacknowledgement.465.5.3.1OnreceiptofavalidIframe.465.5.3.2ReceivingsupervisorycommandframeswiththePbitsetto"1".465.5.4ReceivingREJframes.465.5.4.1ReceiptofavalidREJframe.465.5.4.2Transmittingframes.475.5.5ReceivingRNRframe.475.5.6Datalinklayerownreceiverbusycondition.495.5.7Waitingacknowledgement.495.6Abnormalreleaseandre-establishmentofmultipleframeoperation.505.6.1Criteriaforre-establishment.505.6.2Criteriaforabnormalrelease.505.6.3Proceduresforre-establishment.505.6.4Proceduresforabnormalrelease.505.7Exceptionconditionreportingandrecoveryformultipleframeoperation.515.7.1N(S)sequenceerror.515.7.2Timerrecovery.515.7.3Invalidframecondition.525.7.4N(R)sequenceerror.525.8Listofsystemparameters.525.8.1TimerT200.525.8.1.1ForSAPI=0andSAPI=3.525.8.1.2ForSAPIsotherthan0or3.535.8.2Maximumnumberofretransmissions(N200).535.8.2.1ForSAPI=0and3.535.8.2.2ForSAPIsotherthan0or3.535.8.3MaximumnumberofoctetsinanI,UI,SABMandUAframepartiallyorentirelyavailablefortheinformationfield(N201).535.8.4MaximumnumberofoutstandingIframes(k).535.8.5MaximumnumberofoctetsinaLayer3message.545.9Systemperformancerequirements.546SpecialprotocoloperationonSAPI=0andSAPI=3.55AnnexA(normative):Randomaccessprocedures.56A.1Descriptionoftheprocedure.56A.1.1ProcedureintheMS.56A.1.2ProcedureintheBS.56A.2Format.56SIST ETS 300 938 E5:2003

Page6ETS300938(GSM04.06version5.4.1Release1996):August2000AnnexG(normative):Handlingofframeswithparametererrorsintheaddress,controlandlengthindicatorfields.57G.1General.57G.2Parametererrorsintheaddressfield.57G.2.1UnallocatedSAPI.57G.2.2WrongvalueoftheC/Rbit.57G.2.3EAbitsetto"0".57G.3Parametererrorsinthecontrolfield.57G.3.1Supervisoryframes.57G.3.2Unnumberedframes.58G.4Parametererrorsinthelengthindicatorfield.58G.4.1ELbiterror.58G.4.2Informationframes.58G.4.3Supervisoryframes.58G.4.4DISCandDMframes.58G.4.5SABMUAandUIframes.58AnnexH(informative):Documentchangehistory.59History.60SIST ETS 300 938 E5:2003

Page7ETS300938(GSM04.06version5.4.1Release1996):August2000IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.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.ForewordThisEuropeanTelecommunicationStandard(ETS)hasbeenproducedbyETSITechnicalCommitteeSpecialMobileGroup(SMG).ThisETSdefinesthedatalinklayerprotocoloftheMobileStation-BaseStationSystem(MS-BSS)interfacewithinthedigitalcellulartelecommunicationssystem.ThecontentsofthepresentdocumentmaybesubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocumentitwillthenbere-submittedforformalapprovalproceduresbyETSIwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version5.x.ywhere:5GSMPhase2+Release1996.xtheseconddigitisincrementedforchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.;ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.ThespecificationfromwhichthisETShasbeenderivedwasoriginallybasedonCEPTdocumentation,hencethepresentationofthisETSmaynotbeentirelyinaccordancewiththeETSIdraftingrules.AnnexesBtoFweredeletedfromtheoriginalspecification,however,forreferencingpurposestheannexnumberinghasbeenmaintained.TranspositiondatesDateofadoptionofthisETS:21July2000DateoflatestannouncementofthisETS(doa):31October2000DateoflatestpublicationofnewNationalStandardorendorsementofthisETS(dop/e):30April2001DateofwithdrawalofanyconflictingNationalStandard(dow):30April2001SIST ETS 300 938 E5:2003

Page8ETS300938(GSM04.06version5.4.1Release1996):August2000BlankpageSIST ETS 300 938 E5:2003

Page9ETS300938(GSM04.06version5.4.1Release1996):August20000ScopeThisEuropeanTelecommunicationStandard(ETS)definesadatalinklayerprotocoltobeusedforsignalling,andpossiblyalsoforotherapplications,ontheMS-BSinterface.0.1NormativereferencesThisETSincorporatesbydatedandundatedreference,provisionsfromotherpublications.Thesenormativereferencesarecitedattheappropriateplacesinthetextandthepublicationsarelistedhereafter.Fordatedreferences,subsequentamendmentstoorrevisionsofanyofthesepublicationsapplytothisETSonlywhenincorporatedinitbyamendmentorrevision.Forundatedreferences,thelatesteditionofthepublicationreferredtoapplies.[1]GSM01.04(ETR350):"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(ETS300936):"Digitalcellulartelecommunicationssystem;Layer1Generalrequirements".[5]GSM04.05(ETS300937):"Digitalcellulartelecommunicationssystem;DataLink(DL)layerGeneralaspects".[6]GSM04.07(ETS300939):"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacesignallinglayer3;Generalaspects".[7]GSM04.08(ETS300940):"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacelayer3specification".[8]GSM04.10(ETS300941):"Digitalcellulartelecommunicationssystem;Mobileradiointerfacelayer3Supplementaryservicesspecification;Generalaspects".[9]GSM04.12(ETS300943):"Digitalcellulartelecommunicationssystem(Phase2+);ShortMessageServiceCellBroadcast(SMSCB)supportonthemobileradiointerface".[10]GSM05.02(ETS300908):"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)".0.2AbbreviationsAbbreviationsusedinthisETSarelistedinGSM01.04.SIST ETS 300 938 E5:2003

Page10ETS300938(GSM04.06version5.4.1Release1996):August20001GeneralThisETSdescribestheframestructure,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.ThispartoftheETSisdescriptiveanddoesnotconstraintheimplementationoftherandomaccessfunction.TheprocedureisusedforCHANNELREQUESTontheRACHandHANDOVERACCESSonthemainDCCH.(AnnexesBtoFaredeleted).AnnexGgivesanoverviewofactionstakenonframescontainingparametererrors.1.1OptionsSupportofshortL2headertype1isanoptioninboththemobilestationandthenetwork;undercertainconditionsthesupportismandatory,asspecifiedinotherSpecifications.Alayer2protocolentitynotimplementingshortL2headertype1shalldiagnoseanE/AbiterrorandproceedasdefinedinannexG.2.3.SIST ETS 300 938 E5:2003

Page11ETS300938(GSM04.06version5.4.1Release1996):August20002Framestructureforpeer-to-peercommunication2.1GeneralAlldatalinklayerpeer-to-peerexchangesareinframesconformingtooneoftheformatsshowninfigure1.Severalformattypesareshowninthefigure:-FormatAisusedonDCCHsforframeswherethereisnoinformationfield.-FormatsB,BterandB4areusedonDCCHsforframescontaininganinformationfield:-formatBterisusedonrequestofhigherlayersifandonlyifshortL2headertype1issupportedandaUIcommandistobetransmittedonSAPI0;-formatB4isusedforUIframestransmittedbythenetworkonSACCH;-formatBisappliedinallothercases.-FormatBbisisusedonlyonBCCH,PCH,NCH,andAGCH.-InadditionthereisaFormatCfortransmissionofrandomaccesssignals.FormatCframesaredescribedinannexA.FormatA,B,Bbis,BterandB4framesaredescribedintheremainderofthisETS.Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Fillbits:N201+nFormattypeAFigure1/GSM04.06(sheet1of3):GeneralframeformatsSIST ETS 300 938 E5:2003

Page12ETS300938(GSM04.06version5.4.1Release1996):August2000Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Informationfield:NN+1:Fillbits:N201+nFormattypeBBit87654321OctetNo1:::Informationfield:::N201FormattypeBbisFigure1/GSM04.06(sheet2of3):GeneralframeformatsSIST ETS 300 938 E5:2003

Page13ETS300938(GSM04.06version5.4.1Release1996):August2000Bit87654321OctetNo1: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.SIST ETS 300 938 E5:2003

Page14ETS300938(GSM04.06version5.4.1Release1996):August2000Theendoftheusefulpartoftheframe,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.Theformatoftheaddressfieldisdefinedinsubclause3.2.2.4ControlfieldThecontrolfieldconsistsofoneoctet.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.SIST ETS 300 938 E5:2003

Page15ETS300938(GSM04.06version5.4.1Release1996):August2000Bit87654321Octetno12;;nFigure2/GSM04.06:Formatconvention2.8.2OrderofbittransmissionTheorderofbittransmissionisdefinedinGSM04.04.2.8.3FieldmappingconventionWhenafieldiscontainedwithinasingleoctet,thelowestbitnumberofthefieldrepresentsthelowestordervalue.Whenafieldspansmorethanoneoctet,theorderofbitvalueswithineachoctetprogressivelydecreasesastheoctetnumberincreases.Inthatpartofthefieldcontainedinagivenoctetthelowestbitnumberrepresentsthelowestordervalue.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.SIST ETS 300 938 E5:2003

Page16ETS300938(GSM04.06version5.4.1Release1996):August20003.2AddressfieldformatThefieldconsistsof:-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:Addressfieldformat3.3Addressfieldvariables3.3.1Addressfieldextensionbit(EA)Theaddressfieldrangeisextendedbyreservingthefirsttransmittedbitoftheaddressfieldoctetstoindicatethefinaloctetoftheaddressfield.Thepresenceofa"1"inthefirstbitofanaddressfieldoctetsignalsthatitisthefinaloctetoftheaddressfield.Figure4showsthecasewherethefieldconsistsofoneoctet.3.3.2Command/responsefieldbit(C/R)TheC/Rbitidentifiesaframeaseitheracommandoraresponse.TheMSsideshallsendcommandswiththeC/Rbitsetto"0",andresponseswiththeC/Rbitsetto"1".TheBSsideshalldotheopposite;thatiscommandsaresentwithC/Rsetto"1",andresponsesaresentwithC/Rsetto"0".ThecombinationsfortheBSsideandMSsideareshownintable1.Table1/GSM04.06:C/RfieldbitusageTypeDirectionC/RvalueCommandBSsidetoMSside1MSsidetoBSside0ResponseBSsidetoMSside0MSsidetoBSside13.3.3Serviceaccesspointidentifier(SAPI)Theserviceaccesspointidentifier(SAPI)identifiesapointatwhichdatalinklayerservicesareprovidedbythedatalinklayertoalayer3entity(seeGSM04.05).TheSAPIallows8serviceaccesspointstobespecifiedinitially,wherebit3oftheaddressfieldoctetcontainingtheSAPIistheleastsignificantbinarydigitandbit5isthemostsignificant.TheSAPIvaluesareallocatedasshownintable2.SIST ETS 300 938 E5:2003

Page17ETS300938(GSM04.06version5.4.1Release1996):August2000Table2/GSM04.06:AllocationofSAPIvaluesSAPIvalueRelatedentity0Callcontrolsignalling,mobilitymanagementsignallingandradioresourcemanagementsignalling(seeGSM04.08and04.10)3ShortmessageserviceAllothersReservedforfuturestandardization3.4ControlfieldformatsThecontrolfieldidentifiesthetypeofframe,whichwillbeeitheracommandoraresponse.Thecontrolfieldwillcontainsequencenumbers,whereapplicable.Threetypesofcontrolfieldformatsarespecified:numberedinformationtransfer(Iformat),supervisoryfunctions(Sformat),andunnumberedinformationtransferandcontrolfunctions(Uformat).ThecontrolfieldformatsforLAPDmareshownintable3.3.4.1Informationtransferformat-ITheIformatshallbeusedtoperformaninformationtransferbetweenlayer3entities.ThefunctionsofN(S),N(R)andP(definedin3.5)areindependent;thatis,eachIframehasanN(S)sequencenumber,anN(R)sequencenumberwhichmayormaynotacknowledgeadditionalIframesreceivedbythedatalinklayerentity,andaPbitthatmaybesetto"0"or"1".TheuseofN(S),N(R)andPisdefinedinclause5.3.4.2Supervisoryformat-STheSformatshallbeusedtoperformdatalinksupervisorycontrolfunctionssuchas:acknowledgeIframes,requestretransmissionofIframes,andrequestatemporarysuspensionoftransmissionofIframes.ThefunctionsofN(R)andP/Fareindependent;thatis,eachsupervisoryframehasanN(R)sequencenumberwhichmayormaynotacknowledgeadditionalIframesreceivedbythedatalinklayerentity,andaP/Fbitthatmaybesetto"0"or"1".TheuseofN(R)andtheP/Fbitisdescribedinclause5.3.4.3Unnumberedformat-UTheUformatshallbeusedtoprovideadditionaldatalinkcontrolfunctionsandunacknowledgedinformationtransfer.Thisformatdoesnotcontainsequencenumbers.ItdoesincludeaP/Fbitthatmaybesetto"0"or"1".Table3/GSM04.06:ControlfieldformatControlfieldbits87654321IformatN(R)PN(S)0SformatN(R)P/FSS01UformatUUUP/FUU11N(S)Transmittersendsequencenumber.N(R)Transmitterreceivesequencenumber.SSupervisoryfunctionbit.UUnnumberedfunctionbit.P/FPollbit,whenissuedasacommand,finalbit,whenissuedasaresponse.Fordefinitionofvaluesforsupervisoryfunctionbitsandunnumberedfunctionbits,seetable4.SIST ETS 300 938 E5:2003

Page18ETS300938(GSM04.06version5.4.1Release1996):August20003.4aShortL2headertype1TheshortL2headertype1fieldisusedinformatBterframes,seesubclause2.1.Itconsistsof2bits,bothshalltakevalue0.NOTE:IntroductionoffurthershortL2headertypes(longerthan2bits,settingbit2to"1"andbit1to"0")isforfurtherstudy.TheshortL2headertype1implicitlydefinesaUIcommandframebelongingtoSAPI=0,withlengthN201.AllotherparametersofaL2frameheaderareirrelevant.3.5ControlfieldparametersandassociatedstatevariablesThevariousparametersassociatedwiththecontrolfieldformatsaredescribedinthisclause.Thecodingofthebitswithintheseparametersissuchthatthelowestnumberedbitwithintheparameterfieldistheleastsignificantbit.3.5.1Poll/FinalbitAllframescontainP/F,thePoll/Finalbit.ThePoll/Final(P/F)bitservesafunctioninbothcommandframesandresponseframes.IncommandframestheP/FbitisreferredtoasthePbit.InresponseframesitisreferredtoastheFbit.ThePbitsetto"1"isusedbyadatalinklayerentitytocreate(poll)aresponseframefromthepeerdatalinklayerentity.TheFbitsetto"1"isusedbyadatalinklayerentitytoindicatetheresponseframetransmittedasaresultofasoliciting(poll)command.TheuseoftheP/Fbitisdescribedinclause5.3.5.2Multipleframeoperation-variablesandsequencenumbers3.5.2.1ModulusEachIframeissequentiallynumberedbyasequencenumberwhichmayhavethevalue0through7.Arithmeticsactingonvariableswhicharerelatedtosuchsequencenumbers(i.e.N(S),N(R),V(S),V(R),V(A);seefollowingsubclauses)operatemodulo8.NOTE:Modulo8operationonnegativenumbersisperformedbyaddingmultiplesof8tothenegativenumberuntiltheresultbecomesnonnegative.Thencommonmodulo8operationisapplied.3.5.2.2SendstatevariableV(S)Eachpoint-to-pointdatalinkconnectionendpointshallhaveanassociatedsendstatevariable(V(S))whenusingIframecommands.Thesendstatevariabledenotesthesequencenumberofthenextin-sequenceIframetobetransmitted.Thesendstatevariablecantakeonthevalue0through7.Thevalueofthesendstatevariableshallbeincrementedby1witheachsuccessiveIframetransmission,andshallnotexceedV(A)bymorethanthemaximumnumberofoutstandingIframesk(Thewindowsizekisdefinedinsubclause5.8.4).Thevalueofkmaybeintherangeof1=
Page19ETS300938(GSM04.06version5.4.1Release1996):August2000Theacknowledgestatevariableidentifiesthelastframethathasbeenacknowledgedbyitspeer(V(A)-1equalstheN(S)ofthelastacknowledgedIframe).Theacknowledgestatevariablecantakeonthevalue0through7.ThevalueoftheacknowledgestatevariableshallbeupdatedbythevalidN(R)valuesreceivedfromitspeer(seesubclause3.5.2.6).AvalidN(R)valueisonethatisintherangeV(A)=
Page20ETS300938(GSM04.06version5.4.1Release1996):August20003.7Lengthindicatorfieldvariables3.7.1Lengthindicatorfieldextensionbit(EL)Thelengthindicatorfieldisextendedbyreservingthefirsttransmittedbitofthelengthindicatorfieldoctetstoindicatethefinaloctetofthefield.Presenceofa"1"inthefirstbitofalengthindicatorfieldoctetsignalsthatitisthefinaloctetofthefield.Figure5showsthecasewherethefieldconsistsofoneoctet.3.7.2Moredatabit(M)Themoredatabit,M,isusedtoindicatesegmentationoflayer3messageunitsondatalinklayerframes.Layer3messages,whichneedtobesegmented,shallonlybetransportedbyI-frames.WhentheMbitissetto"1",itindicatesthattheinformationfieldoftheframecontainsonlyasegmentofthelayer3messageunit.TheMbitsetto"0"indicates:i)thattheinformationfieldcontainsacompletelayer3messageunitprovidedthattheMbitofthepreviousframewassetto"0";ii)thattheinformationfieldcontainsthelastsegmentofalayer3messageunitiftheMbitofthepreviousframewassetto"1".WhentheMbitissetto"1",theinformationfieldshallcontainthemaximumnumberofoctets,N201,thataninformationframecancontain,seesubclause5.8.3forthevalueofN201.Inframesotherthaninformation(I)framestheMbitshallbesetto"0".3.7.3Lengthindicator(L)Thelengthindicatorconsistsof6bitsandisusedtoindicatethenumberofoctetscontainedintheinformationfieldofUI,SABM,UAorIframes,ieanyvaluefrom0toN201inclusive.TheL=0shallbeusedinframesnotcontaininganinformationfield.3.8CommandsandresponsesThefollowingcommandsandresponsesareusedbyeithertheMSortheBSdatalinklayerentitiesandarerepresentedintable4.Eachdatalinkconnectionsupportstheappropriatesetofcommandsandresponsesforthetypeofoperationdesired(seeclause5).ForpurposesoftheLAPDmprocedures,frameswiththesupe
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