SIST EN 300 938 V6.2.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 6.2.1 Release 1997)
- Abstract
CR SMG#31
- Status
- Published
- Publication Date
- 30-Nov-2003
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Dec-2003
- Due Date
- 01-Dec-2003
- Completion Date
- 01-Dec-2003
SIST EN 300 938 V6.2.1:2003 is the Slovenian standard corresponding to ETSI EN 300 938 for GSM. It specifies the data link layer on the Mobile Station - Base Station System (MS-BSS) interface, with the LAPDm frame formats, primitives and procedures used for signalling and related applications between the mobile station and the base station system.
What does SIST EN 300 938 V6.2.1:2003 specify?
SIST EN 300 938 V6.2.1:2003 defines how LAPDm operates on GSM radio-interface channels. The scope covers signalling on the MS-BS interface, and the text notes that LAPDm may also be used for other applications.
The document is organized into general frame structure, field formats, layer-to-layer primitives, peer-to-peer protocol procedures, and a section on special protocol operation for SAPI 0 and SAPI 3. It also includes an annex for random access procedures and an annex for parameter-error handling.
| Annex | What it covers |
|---|---|
| Annex A | Random access procedures and format |
| Annex G | Actions taken on frames with parameter errors in the address, control and length indicator fields |
| Annex H | Change Request History |
What are the key requirements of SIST EN 300 938 V6.2.1:2003?
SIST EN 300 938 V6.2.1:2003 sets out the frame types, field coding and procedures that make LAPDm work reliably over GSM radio channels.
- Clause 2 defines frame formats A, B, Bbis, Bter and B4, plus framing, fill bits and transparency. In practice, implementers must build and parse the right frame type for each channel and transfer mode.
- Clause 3 defines the address, control and length indicator fields. The address field carries the Command/response bit (C/R), Service access point identifier (SAPI) and Link Protocol Discriminator (LPD); this matters because it tells the receiver which layer 3 entity the frame belongs to.
- Clause 3 also distinguishes the Information (I), Supervisory (S) and Unnumbered (U) control formats, and defines the Poll/Final (P/F) bit. That is the basis for acknowledgements, polling and mode-setting commands.
- Clause 4 defines the service primitives between layer 2, layer 3 and the physical layer, including DL-ESTABLISH, DL-RELEASE, DL-DATA, DL-UNITDATA and PH-DATA. These primitives are the interface points an implementation has to expose or call.
- Clauses 5.2 to 5.3 cover unacknowledged operation with UI frames. On BCCH and CCCH, only unacknowledged mode is required, and invalid SAPI values are discarded.
- Clauses 5.4 to 5.5 cover acknowledged multiple-frame operation with SABM, UA, DISC, DM, RR, RNR, REJ and I frames. The protocol uses modulo-8 sequence numbering with V(S), V(A), V(R), T200, N200, k and N201, so implementations must track send, receive and retransmission state.
- Clause 5.4.3 defines suspension, resumption and reconnection during channel change. In practice, this protects layer 3 messages for SAPI 0 during assignment or handover.
- Clause 5.6 and Annex G define error handling and abnormal release conditions. That tells the implementation when to recover locally and when to report an MDL-ERROR indication upward.
What terms does SIST EN 300 938 V6.2.1:2003 define?
- Link Access Procedure on the Dm channel (LAPDm) - The GSM layer 2 protocol defined here for radio-interface signalling.
- Mobile Station - Base Station System (MS-BSS) interface - The radio interface between the mobile station and the base station system.
- Service access point identifier (SAPI) - The value that identifies which layer 3 service endpoint a frame belongs to.
- Poll/Final bit (P/F bit) - The bit used for polling in commands and for final response indication in responses.
- Unnumbered Information (UI) - The frame type used for unacknowledged information transfer.
- Set asynchronous balanced mode (SABM) - The unnumbered command used to establish multiple-frame acknowledged operation.
- Receive ready (RR) - The supervisory frame that acknowledges received I frames and shows readiness to receive more.
- Receive not ready (RNR) - The supervisory frame that reports a busy condition and temporary inability to accept more I frames.
Who uses SIST EN 300 938 V6.2.1:2003?
SIST EN 300 938 V6.2.1:2003 is used by GSM equipment designers, protocol developers, test laboratories and interoperability engineers working on mobile stations, base station systems and channel control signalling. It is also relevant to quality and purchasing teams checking whether an implementation supports the expected GSM data link behavior on BCCH, CCCH and DCCH channels.
Which standards are used with SIST EN 300 938 V6.2.1:2003?
The document refers to GSM01.04 for abbreviations, GSM04.01 for general MS-BSS aspects, GSM04.03 for channel structures and access capabilities, GSM04.04 for layer 1 requirements, and GSM04.05 for general data link layer aspects. It also uses GSM04.07 and GSM04.08 for layer 3, GSM04.10 and GSM04.12 for supplementary services and SMSCB, GSM05.02 for multiplexing and multiple access, GSM08.56 and GSM08.58 for the BSC-BTS interface, and CCITT Recommendation Z.100 for SDL terminology and timer handling.
What does the SIST EN 300 938 V6.2.1:2003 document contain?
The document contains frame diagrams, field formats, primitive definitions, procedure descriptions and state-oriented handling rules for LAPDm. Clause 2 shows the peer-to-peer frame structures, clause 3 defines the frame fields, clause 4 defines the layer-to-layer primitives, and clause 5 gives the operational procedures for establishment, transfer, suspension, resumption, release and recovery. Annex A adds random access procedures, and Annex G summarizes how to treat frames with parameter errors.
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Frequently Asked Questions
SIST EN 300 938 V6.2.1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Digital cellular telecommunications system (Phase 2+) (GSM); Mobile Station - Base Station System (MS - BSS) interface; Data Link (DL) layer specification (GSM 04.06 version 6.2.1 Release 1997)". This standard covers: CR SMG#31
CR SMG#31
SIST EN 300 938 V6.2.1:2003 is classified under the following ICS (International Classification for Standards) categories: 33.070.50 - Global System for Mobile Communication (GSM). The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 300 938 V6.2.1:2003 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
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 6.2.1 Release 1997)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 6.2.1SIST EN 300 938 V6.2.1:2003en01-december-2003SIST EN 300 938 V6.2.1:2003SLOVENSKI
STANDARD
ETSIEN300938V6.2.1(2000-09)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interface;DataLink(DL)layerspecification(GSM04.06version6.2.1Release1997)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)2(GSM04.06version6.2.1Release1997)ReferenceREN/SMG-020406Q6R2KeywordsDigitalcellulartelecommunicationssystem,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 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)3(GSM04.06version6.2.1Release1997)ContentsIntellectualPropertyRights.7Foreword.70Scope.80.1References.80.2Abbreviations.81General.91.1Options.92Framestructureforpeer-to-peercommunication.102.1General.102.2Framedelimitationandfillbits.122.3Addressfield.132.4Controlfield.132.5Lengthindicatorfield.132.5aShortL2headertype1.132.6Informationfield.132.7Transparency.132.8Formatconvention.132.8.1Numberingconvention.132.8.2Orderofbittransmission.142.8.3Fieldmappingconvention.143ElementsofproceduresandformatsoffieldsforDataLinkLayerpeer-to-peercommunication.143.1General.143.2Addressfieldformat.143.3Addressfieldvariables.153.3.1Addressfieldextensionbit(EA).153.3.2Command/responsefieldbit(C/R).153.3.3Serviceaccesspointidentifier(SAPI).153.4Controlfieldformats.163.4.1Informationtransferformat-I.163.4.2Supervisoryformat-S.163.4.3Unnumberedformat-U.163.4aShortL2headertype1.173.5Controlfieldparametersandassociatedstatevariables.173.5.1Poll/Finalbit.173.5.2Multipleframeoperation-variablesandsequencenumbers.173.5.2.1Modulus.173.5.2.2SendstatevariableV(S).173.5.2.3AcknowledgestatevariableV(A).173.5.2.4SendsequencenumberN(S).183.5.2.5ReceivestatevariableV(R).183.5.2.6ReceivesequencenumberN(R).183.5.2.7Otherparametersandvariables.183.5.3Unacknowledgedoperationvariablesandparameters.183.6Lengthindicatorfieldformat.183.7Lengthindicatorfieldvariables.193.7.1Lengthindicatorfieldextensionbit(EL).193.7.2Moredatabit(M).193.7.3Lengthindicator(L).193.8Commandsandresponses.193.8.1Information(I)commands.193.8.2Setasynchronousbalancedmode(SABM)command.203.8.3Disconnect(DISC)command.203.8.4Unnumberedinformation(UI)command.213.8.5Receiveready(RR)command/response.21SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)4(GSM04.06version6.2.1Release1997)3.8.6Reject(REJ)command/response.213.8.7Receivenotready(RNR)command/response.213.8.8Unnumberedacknowledgement(UA)response.223.8.9Disconnectedmode(DM)response.224Elementsforlayer-to-layercommunication.224.1Definitionofprimitivesandparameters.224.1.1Genericnames.224.1.1.1DL-ESTABLISH.224.1.1.2DL-RELEASE.234.1.1.3DL-DATA.234.1.1.4DL-UNITDATA.234.1.1.5DL-SUSPEND.234.1.1.6DL-RESUME.234.1.1.7DL-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.244.1.1.13PH-CONNECT.244.1.1.14PH-READY-TO-SEND.244.1.1.15PH-EMPTY-FRAME.244.1.2Primitivestypes.244.1.2.1REQUEST.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.264.1.3.5Errorcause.264.1.3.6Establishmode.264.1.3.7L2headertype.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).355.4.2Informationtransfer.365.4.2.1Generalrequirements.365.4.2.2Errorconditions.365.4.2.3Fillframes.375.4.3Suspensionandresumptionofmultipleframeoperation.375.4.3.1General.375.4.3.2Suspension.385.4.3.3Resumption.38SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)5(GSM04.06version6.2.1Release1997)5.4.3.3.1Procedureafterchannelchange.385.4.3.3.2Procedureafterreturningtotheoldchannel(MSonly).395.4.4Terminationofmultipleframeoperation.395.4.4.1General.395.4.4.2Normalreleaseprocedure.395.4.4.3ProcedureonexpiryoftimerT200fornormalrelease.405.4.4.4Localendreleaseprocedure.405.4.5Idlestate.405.4.6Collisionofunnumberedcommandsandresponses.415.4.6.1Identicaltransmittedandreceivedcommands.415.4.6.2Differenttransmittedandreceivedcommands.415.4.6.3UnsolicitedDMresponseandSABMorDISCcommand.415.5Proceduresforinformationtransferinmultipleframeoperation.415.5.1TransmittingIframes.415.5.2ReceivingIframes.425.5.2.1PbitofthereceivedIframesetto"1".425.5.2.2PbitofthereceivedIframesetto"0".425.5.3Receivingacknowledgement.435.5.3.1OnreceiptofavalidIframe.435.5.3.2ReceivingsupervisorycommandframeswiththePbitsetto"1".435.5.4ReceivingREJframes.435.5.4.1ReceiptofavalidREJframe.435.5.4.2Transmittingframes.445.5.5ReceivingRNRframe.445.5.6Datalinklayerownreceiverbusycondition.465.5.7Waitingacknowledgement.465.6Abnormalreleaseandre-establishmentofmultipleframeoperation.475.6.1Criteriaforre-establishment.475.6.2Criteriaforabnormalrelease.475.6.3Proceduresforre-establishment.475.6.4Proceduresforabnormalrelease.475.7Exceptionconditionreportingandrecoveryformultipleframeoperation.485.7.1N(S)sequenceerror.485.7.2Timerrecovery.485.7.3Invalidframecondition.485.7.4N(R)sequenceerror.495.8Listofsystemparameters.495.8.1TimerT200.495.8.1.1ForSAPI=0andSAPI=3.495.8.1.2ForSAPIsotherthan0or3.495.8.2Maximumnumberofretransmissions(N200).505.8.2.1ForSAPI=0and3.505.8.2.2ForSAPIsotherthan0or3.505.8.3MaximumnumberofoctetsinanI,UI,SABMandUAframepartiallyorentirelyavailablefortheinformationfield(N201).505.8.4MaximumnumberofoutstandingIframes(k).505.8.5MaximumnumberofoctetsinaLayer3message.505.9Systemperformancerequirements.516SpecialprotocoloperationonSAPI=0andSAPI=3.52AnnexA(normative):Randomaccessprocedures.53A.1Descriptionoftheprocedure.53A.1.1ProcedureintheMS.53A.1.2ProcedureintheBS.53SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)6(GSM04.06version6.2.1Release1997)A.2Format.53AnnexG(normative):Handlingofframeswithparametererrorsintheaddress,controlandlengthindicatorfields.54G.1General.54G.2Parametererrorsintheaddressfield.54G.2.1UnallocatedSAPI.54G.2.2WrongvalueoftheC/Rbit.54G.2.3EAbitsetto"0".54G.3Parametererrorsinthecontrolfield.55G.3.1Supervisoryframes.55G.3.2Unnumberedframes.55G.4Parametererrorsinthelengthindicatorfield.55G.4.1ELbiterror.55G.4.2Informationframes.55G.4.3Supervisoryframes.56G.4.4DISCandDMframes.56G.4.5SABMUAandUIframes.56AnnexH(informative):ChangeRequestHistory.57History.58SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)7(GSM04.06version6.2.1Release1997)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:Version6.x.ywhere:6indicatesRelease1997ofGSMPhase2+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 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)8(GSM04.06version6.2.1Release1997)0ScopeThepresentdocumentdefinesadatalinklayerprotocoltobeusedforsignalling,andpossiblyalsoforotherapplications,ontheMS-BSinterface.0.1ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.• ForthisRelease1997document,referencestoGSMdocumentsareforRelease1997versions(version6.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 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)9(GSM04.06version6.2.1Release1997)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 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)10(GSM04.06version6.2.1Release1997)2Framestructureforpeer-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 EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)11(GSM04.06version6.2.1Release1997)Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Informationfield:NN+1:Fillbits:N201+nFormattypeBBit87654321OctetNo1:::Informationfield:::N201FormattypeBbisFigure1/GSM04.06(sheet2of3):GeneralframeformatsSIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)12(GSM04.06version6.2.1Release1997)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.SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)13(GSM04.06version6.2.1Release1997)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.Theformatoftheaddressfieldisdefinedinsubclause3.2.2.4ControlfieldThecontrolfieldconsistsofoneoctet.Theformatofthecontrolfieldisdefinedinsubclause3.4.2.5LengthindicatorfieldThelengthindicatorfieldmayconsistofavariablenumberofoctets.However,forapplicationsoncontrolchannelsthefieldconsistsofonlyoneoctet.Theformatofthefieldisdefinedinsubclause3.6.2.5aShortL2headertype1TheshortL2headertype1consistsoftwobits.Itscontentsaredefinedinsubclause3.4a.2.6InformationfieldTheinformationfieldofaframe,whenpresent,hasthepositionintheframedefinedinsubclause2.1.Themaximumnumberofoctetsintheinformationfield(N201)isdefinedinsubclause5.8.3.2.7TransparencyBecauseoftheframedelimitationtechniqueused(seesubclause2.2),theframecanincludeanypossiblesequenceofbitswithouttheneedforadditionaltransparencymechanisms.2.8Formatconvention2.8.1NumberingconventionThebasicconventionusedinthisTechnicalSpecificationisillustratedinfigure2.Thebitsaregroupedintooctets.Thebitsofanoctetareshownhorizontallyandarenumberedfrom1to8.Multipleoctetsareshownverticallyandarenumberedfrom1ton.SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)14(GSM04.06version6.2.1Release1997)Bit87654321Octetno12;;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.3.2AddressfieldformatThefieldconsistsof:-theaddressfieldextensionbitEA;-thecommand/responsebitC/R;-theSAPI;SIST EN 300 938 V6.2.1:2003
ETSIETSIEN300938V6.2.1(2000-09)15(GSM04.06version6.2.1Release1997)-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 EN 300 938 V6.2.1:2003
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