SIST EN 300 938 V7.1.2:2003
(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 7.1.2 Release 1998)
- 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 V7.1.2:2003 is the Slovenian adoption of EN 300 938 Version 7.1.2, published by SIST and aligned with ETSI. It specifies the GSM Link Access Procedure on the Dm channel, called LAPDm, for the Mobile Station - Base Station System (MS - BSS) interface. In practice, it defines the frame formats, control fields, primitives, and procedures used to move signalling data between a mobile station and the base station system.
What does SIST EN 300 938 V7.1.2:2003 specify?
SIST EN 300 938 V7.1.2:2003 specifies the data link layer protocol used for signalling, and possibly other applications, on the MS-BS interface. The document covers both unacknowledged transfer and acknowledged multiple-frame transfer, and it also defines how LAPDm behaves on different GSM control channels.
The document is organized into:
- Clause 1 - general description and options
- Clause 2 - frame structure for peer-to-peer communication
- Clause 3 - procedure elements and field formats
- Clause 4 - layer-to-layer communication primitives
- Clause 5 - LAPDm peer-to-peer protocol procedures
- Clause 6 - special protocol operation on SAPI=0 and SAPI=3
- Annex A - random access procedures
- Annex G - handling frames with parameter errors
- Annex H - change request history
What are the key requirements of SIST EN 300 938 V7.1.2:2003?
SIST EN 300 938 V7.1.2:2003 defines two operating modes: unacknowledged operation using UI frames, and acknowledged operation using multiple-frame procedures. BCCH and CCCH use only unacknowledged operation, while DCCHs can use both modes. That matters because implementers must choose the right procedure set for each channel type.
The frame structure in clause 2 uses several format types, including A, B, Bbis, Bter and B4. The document also defines fill bits, frame delimitation by the physical layer, and a transparency method that allows any bit sequence without extra escaping. This is important for radio implementation because the physical layer, not LAPDm, marks frame boundaries.
Clause 3 defines the key frame fields:
- The address field carries EA, C/R, SAPI and LPD.
- The control field carries I, S and U formats.
- The length indicator field carries the information-field length and the M bit for segmentation.
These fields control who a frame is for, whether it is a command or response, and how much user data is inside. In practice, they drive parsing, multiplexing and segmentation.
Clause 4 defines the service primitives between layer 2, layer 3 and the physical layer, including DL-ESTABLISH, DL-RELEASE, DL-DATA, DL-UNITDATA, DL-SUSPEND, DL-RESUME, DL-RECONNECT, MDL-ERROR, PH-DATA, PH-RANDOMACCESS and PH-READY-TO-SEND. These primitives are the interface points software uses to request transfer, report errors, and synchronize transmission.
Clause 5 gives the main LAPDm procedures for:
- UI transfer without error recovery
- Establishment of multiple-frame operation with SABM and UA
- Release with DISC, UA and DM
- Information transfer with I, RR, RNR and REJ frames
- Busy handling, timer recovery and retransmission
- Suspension, resumption and reconnection for channel changes
This is the core of the document. It tells designers how to establish a link, carry Layer 3 messages reliably, and recover from lost or delayed frames.
The special operation in clause 6 applies to SAPI=0 and SAPI=3. That matters because call control, mobility management, radio resource management and short message service use those SAPIs.
What terms does SIST EN 300 938 V7.1.2:2003 define?
- LAPDm - Link Access Procedure on the Dm channel; the GSM layer 2 protocol defined here for signalling on the MS-BSS interface.
- SAPI - Service Access Point Identifier; it selects which layer 3 entity a frame belongs to.
- P/F bit - Poll/Final bit; in commands it polls the peer, and in responses it indicates the answer to that poll.
- T200 - the main retransmission timer for acknowledged operation; it triggers recovery when a response does not arrive in time.
- N201 - the maximum number of octets available for the information field in a frame.
- UI command - Unnumbered Information frame; used for unacknowledged transfer.
- SABM - Set Asynchronous Balanced Mode; used to establish multiple-frame operation.
Who uses SIST EN 300 938 V7.1.2:2003?
SIST EN 300 938 V7.1.2:2003 is used by GSM radio engineers, mobile station implementers, base station system and BSS controller developers, and signalling protocol test teams. It is also used by quality, interoperability and acceptance teams that need to verify frame handling, link establishment, release, retransmission, and behaviour on control channels such as BCCH, CCCH, SACCH, SDCCH and FACCH.
Which standards are used with SIST EN 300 938 V7.1.2:2003?
- GSM01.04 - provides abbreviations and acronyms used in the document.
- GSM04.01 - gives MS-BSS general aspects and principles.
- GSM04.03 - defines channel structures and access capabilities.
- GSM04.04 - defines Layer 1 general requirements, including bit transmission order.
- GSM04.05 - gives general aspects of the data link layer.
- GSM04.07 / GSM04.08 / GSM04.10 / GSM04.12 - provide Layer 3 signalling context, including call control, mobility, radio resource management, supplementary services and SMSCB.
- GSM05.02 - covers multiplexing and multiple access on the radio path.
- GSM08.56 / GSM08.58 - cover the BSC-BTS interface layer 2 and layer 3.
- CCITT Recommendation Z.100 - provides the timer handling terminology used for procedures such as T200.
What does the SIST EN 300 938 V7.1.2:2003 document contain?
The document contains frame-format figures, bit-field layouts, tables of commands and responses, primitive definitions, and step-by-step procedures for establishment, transfer, suspension, resumption and release. It also includes parameter definitions for state variables, timers and window size, plus the rules for segmentation and fill frames. Annex A gives the random access procedure format, and Annex G summarizes what to do when address, control or length-indicator fields contain parameter errors.
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Frequently Asked Questions
SIST EN 300 938 V7.1.2:2003 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 7.1.2 Release 1998)". This standard covers: CR SMG#31
CR SMG#31
SIST EN 300 938 V7.1.2:2003 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 V7.1.2:2003 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 7.1.2 Release 1998)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 7.1.2SIST EN 300 938 V7.1.2:2003en01-december-2003SIST EN 300 938 V7.1.2:2003SLOVENSKI
STANDARD
ETSIEN300938V7.1.2(2000-09)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);MobileStation-BaseStationSystem(MS-BSS)interface;DataLink(DL)layerspecification(GSM04.06version7.1.2Release1998)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 938 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)2(GSM04.06version7.1.2Release1998)ReferenceREN/SMG-020406Q7R1KeywordsDigitalcellulartelecommunicationssystem,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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)3(GSM04.06version7.1.2Release1998)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.132.8.3Fieldmappingconvention.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.153.4.1Informationtransferformat-I.163.4.2Supervisoryformat-S.163.4.3Unnumberedformat-U.163.4aShortL2headertype1.163.5Controlfieldparametersandassociatedstatevariables.163.5.1Poll/Finalbit.173.5.2Multipleframeoperation-variablesandsequencenumbers.173.5.2.1Modulus.173.5.2.2SendstatevariableV(S).173.5.2.3AcknowledgestatevariableV(A).173.5.2.4SendsequencenumberN(S).173.5.2.5ReceivestatevariableV(R).183.5.2.6ReceivesequencenumberN(R).183.5.2.7Otherparametersandvariables.183.5.3Unacknowledgedoperationvariablesandparameters.183.6Lengthindicatorfieldformat.183.7Lengthindicatorfieldvariables.183.7.1Lengthindicatorfieldextensionbit(EL).183.7.2Moredatabit(M).183.7.3Lengthindicator(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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)4(GSM04.06version7.1.2Release1998)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.264.1.3.8Priority.274.2Primitiveprocedures.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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)5(GSM04.06version7.1.2Release1998)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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)6(GSM04.06version7.1.2Release1998)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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)7(GSM04.06version7.1.2Release1998)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:Version7.x.ywhere:7indicatesRelease1998ofGSMPhase2+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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)8(GSM04.06version7.1.2Release1998)0ScopeThepresentdocumentdefinesadatalinklayerprotocoltobeusedforsignalling,andpossiblyalsoforotherapplications,ontheMS-BSinterface.0.1ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.• ForthisRelease1998document,referencestoGSMdocumentsareforRelease1998versions(version7.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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)9(GSM04.06version7.1.2Release1998)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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)10(GSM04.06version7.1.2Release1998)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 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)11(GSM04.06version7.1.2Release1998)Bit87654321OctetNo1:Addressfield:kControlfieldk+1k+2:Lengthindicatorfield:nn+1:Informationfield:NN+1:Fillbits:N201+nFormattypeBBit87654321OctetNo1:::Informationfield:::N201FormattypeBbisFigure1/GSM04.06(sheet2of3):GeneralframeformatsSIST EN 300 938 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)12(GSM04.06version7.1.2Release1998)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.SIST EN 300 938 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)13(GSM04.06version7.1.2Release1998)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.Bit87654321Octetno12;;nFigure2/GSM04.06:Formatconvention2.8.2OrderofbittransmissionTheorderofbittransmissionisdefinedinGSM04.04.SIST EN 300 938 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)14(GSM04.06version7.1.2Release1998)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;-andtheLinkProtocolDiscriminatorLPD.Theformatoftheaddressfieldforcontrolchannelsisshowninfigure4.Theaddressfieldextensionbit,EA,enablesextensionofthefieldtospanmorethanoneoctet.Thevalue"0"isusedtoindicateanextension,thevalue"1"shallbeusedforthefinaladdressfieldoctet.TheLinkProtocolDiscriminator(LPD)correspondingtotheuseinthisTechnicalSpecificationshalltakethevalue"00",allothervaluesarereserved.NOTE:LPD="01"correspondstothedatalinkprotocolusedforSMSCB(seeGSM04.12).SIST EN 300 938 V7.1.2:2003
ETSIETSIEN300938V7.1.2(2000-09)15(GSM04.06version7.1.2Release1998)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",an
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