SIST EN 300 938 V8.0.1:2003
(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 8.0.1 Release 1999)
- Abstract
upgrade to R99
- 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 V8.0.1:2003 is the Slovenian adoption of ETSI EN 300 938 Version 8.0.1 for GSM Phase 2+ Release 1999. It specifies the Data Link (DL) layer protocol on the Mobile Station - Base Station System (MS-BSS) interface, mainly LAPDm, for signalling and related uses on GSM radio control channels.
What does SIST EN 300 938 V8.0.1:2003 specify?
SIST EN 300 938 V8.0.1:2003 defines the frame formats, field layouts, primitives and procedures for LAPDm on the Dm channel. In practice, it tells implementers how MS and network entities exchange signalling frames over the radio interface, including unacknowledged and acknowledged operation.
The document is organized into:
- Clause 2 - peer-to-peer frame structure
- Clause 3 - field formats and frame elements
- Clause 4 - layer-to-layer primitives and parameters
- Clause 5 - LAPDm procedures
- Clause 6 - special protocol operation for SAPI=0 and SAPI=3
- Annex A - random access procedures
- Annex G - handling of frames with parameter errors
- Annex H - change request history
| Annex | What it covers |
|---|---|
| A | Random access procedures and format |
| G | Actions for errors in the address, control and length indicator fields |
| H | Change request history |
What are the key requirements of SIST EN 300 938 V8.0.1:2003?
Clause 2 defines several frame formats for control channels, including formats for frames with and without an information field, plus a format for random access signals in Annex A. This matters because the channel type and frame type determine how the radio link is interpreted and which fields carry user or signalling data.
Clause 3 defines the address field, control field and length indicator field. The address field carries the Service Access Point Identifier (SAPI) and the Command/Response bit (C/R); the control field selects I, S or U frame operation; and the length indicator field sets the information field length and the segmentation bit M. In practice, this is the core of parsing and building LAPDm frames.
Clause 3.5 and 3.7 define the sequence variables and transfer rules used in acknowledged mode, including the send and receive state variables, the modulus of 8, the Poll/Final (P/F) bit, timer T200, retransmission counter N200, window size k and maximum information field size N201. These values control ordering, acknowledgement and retry behavior, so they are the main parameters for interoperability.
Clause 4 defines primitives between layer 2, layer 3 and the physical layer, such as DL-ESTABLISH, DL-RELEASE, DL-DATA, DL-UNITDATA, DL-SUSPEND, DL-RESUME, DL-RECONNECT, DL-RANDOMACCESS, MDL-ERROR and PH-DATA. This matters because system software uses these primitives to request transmission, report status and recover from errors.
Clause 5 describes unacknowledged and acknowledged procedures. Unacknowledged operation uses UI frames, while acknowledged operation uses SABM, UA, DISC, RR, RNR, REJ and I frames with sequencing, acknowledgement and retransmission rules. For implementers, this is the operational heart of the protocol.
Clause 5.4 also covers establishment, release, suspension, resumption and collision handling. The document distinguishes normal establishment, contention resolution on SAPI=0, normal release, local end release and abnormal release. This is important for call setup, handover and channel change behavior.
Clause 5.5 adds flow control and error recovery, including peer busy handling, own receiver busy handling, timer recovery and preemption of low-priority messages by high-priority ones on SAPI=0. In practice, this affects how voice and signalling traffic are protected during load, loss or handover events.
Clause 6 states special protocol operation for SAPI=0 and SAPI=3. It makes clear that these SAPIs need mandatory special handling in acknowledged mode.
What terms does SIST EN 300 938 V8.0.1:2003 define?
- LAPDm - The Link Access Procedure on the Dm channel, used for GSM radio signalling between MS and BSS.
- SAPI (Service Access Point Identifier) - The identifier that selects which layer 3 entity receives the DL service.
- P/F bit (Poll/Final bit) - A control bit used to poll the peer or indicate the final response.
- T200 - The timer used for waiting on acknowledgements and for retransmission control.
- N201 - The maximum number of octets allowed in the information field.
- N200 - The maximum number of retransmission attempts before abnormal release.
- M bit - The segmentation bit that shows whether an I frame carries a complete message or only a segment.
Who uses SIST EN 300 938 V8.0.1:2003?
This standard is used by GSM mobile station developers, base station and network protocol implementers, and radio resource management designers. It also matters to test laboratories, interoperability teams and quality managers who verify frame handling, retries, handover behavior and channel-change robustness on GSM control channels.
Which standards are used with SIST EN 300 938 V8.0.1:2003?
- GSM01.04 - Provides the abbreviations and acronyms used by the document.
- GSM04.01 - Gives general MS-BSS interface principles.
- GSM04.03 - Defines channel structures and access capabilities.
- GSM04.04 - Defines Layer 1 general requirements.
- GSM04.05 - Gives general aspects of the DL layer.
- GSM04.07 and GSM04.08 - Provide Layer 3 general aspects and Layer 3 specification, including how LAPDm is used.
- GSM04.10 and GSM04.12 - Cover supplementary services and SMS cell broadcast aspects referenced by the protocol.
- GSM05.02 - Covers multiplexing and multiple access on the radio path.
- GSM08.56 and GSM08.58 - Cover BSC-BTS layer 2 and layer 3.
- CCITT Recommendation Z.100 - Supplies the timer terminology used for protocol procedures.
What does the SIST EN 300 938 V8.0.1:2003 document contain?
The document includes frame format figures, field mapping rules, primitive tables and procedure descriptions for establishment, transfer, release and recovery. It also contains the frame and field handling rules for UI, I, S and U frames, plus the special short L2 header type 1 option and the rules for fill frames.
Annex A gives the random access procedure and format used for channel request and handover access. Annex G summarizes how the protocol handles parameter errors in the address, control and length indicator fields, which is useful for implementation checks and conformance testing.
The document also includes a primitive matrix for layer-to-layer communication, showing which primitives apply to DCCH, SACCH, BCCH, CCCH and RACH use cases. For engineers, this is the quickest way to map the specification to software interfaces and test cases.
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Frequently Asked Questions
SIST EN 300 938 V8.0.1:2003 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 8.0.1 Release 1999)". This standard covers: upgrade to R99
upgrade to R99
SIST EN 300 938 V8.0.1:2003 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 V8.0.1:2003 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 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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