SIST EN 301 709 V7.2.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Link Adaptation (GSM 05.09 version 7.2.1 Release 1998)
- Abstract
CR SMG#30, 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 301 709 V7.2.1:2003 is the Slovenian adoption of ETSI EN 301 709 V7.2.1 for GSM link adaptation. It specifies how Adaptive Multi-Rate (AMR) speech traffic channels in digital cellular telecommunications systems use in-band signalling, codec mode control, and AMR configuration changes between Mobile Stations (MS) and Base Station Systems (BSS). The document is intended for GSM equipment that supports AMR speech traffic channels, especially network-side and mobile-side implementations.
What does SIST EN 301 709 V7.2.1:2003 specify?
SIST EN 301 709 V7.2.1:2003 specifies the detailed procedures for link adaptation and control in GSM MSs and BSSs that support AMR speech services. It focuses on how the two ends measure link quality, select codec modes, exchange in-band control information, and change AMR configuration during a call.
The document is organized into:
- Clause 1 - references and abbreviations
- Clause 2 - general description
- Clause 3 - AMR in-band control and link adaptation
- Annexes A to D - informative examples and history
| Annex | What it covers |
|---|---|
| Annex A | Example solution for link quality estimation |
| Annex B | Example definition of mode command/request decision thresholds |
| Annex C | Principles for AMR codec mode adaptation with TFO |
| Annex D | Change control history |
What are the key requirements of SIST EN 301 709 V7.2.1:2003?
The core of SIST EN 301 709 V7.2.1:2003 is the control loop between measured channel quality, codec mode signalling, and network control. In practice, implementers need to make the MS and BSS measure, signal, and apply codec changes in a synchronized way.
Link quality drives codec selection
Clause 3.3.1 defines a normalized one-dimensional Quality Indicator, referenced as equivalent carrier-to-interferer ratio. The MS and BSS continuously update this estimate and use it to select codec modes. In practice, this means the adaptation logic is based on channel quality, not on subjective speech quality.
Codec modes are changed through thresholds and hysteresis
Clause 3.3.2 defines how Quality Indicator values are mapped to Codec Mode Commands and Codec Mode Requests. The mapping uses lower and upper thresholds with hysteresis to prevent fast toggling between modes. Practically, the device should only switch when quality moves clearly across a decision boundary.
In-band signalling has two layers
Clause 3.2 splits AMR signalling into frequent signalling for Codec Mode Indication, Command, and Request, and robust signalling for configuration changes using RATSCCH. Frequent signalling is aligned to every second speech frame, while RATSCCH is frame-stealing based and less frequent. This matters because mode changes are tightly timed, while configuration changes are slower but more resilient.
AMR configuration is set at call setup and can change during a call
Clause 3.4 says the Active Codec Set (ACS), Initial Codec Mode (ICM), and decision thresholds are defined at call setup and handover, then may be modified during a call. The ACS can contain up to four codec modes. Practically, this tells the implementer which modes are active and which mode is the starting point after setup or handover.
Timing and response behavior are prescribed
Clause 3.3.3 requires the MS to apply a received Codec Mode Command on the next possible speech frame and no later than three speech frames later. The BTS should apply a requested mode as early as possible unless network control overrides it. This keeps both ends synchronized and limits audible delay in adapting to radio conditions.
Tandem Free Operation changes the control path
Clause 3.1.2 and Annex C describe AMR behavior when Tandem Free Operation (TFO) is active. In that case, two radio links are involved and both links influence the effective codec decision. For operators, this means codec changes may depend on both local and remote radio conditions.
What terms does SIST EN 301 709 V7.2.1:2003 define?
- Active Codec Set (ACS) - The set of AMR codec modes used for adaptation, with up to four modes.
- Adaptive Multi-Rate (AMR) - The speech service whose codec mode changes with radio link quality.
- Codec Mode Command (CMC) - The network-side instruction that tells the MS which codec mode to use.
- Codec Mode Request (CMR) - The MS-side request that tells the network which codec mode is preferred.
- Codec Mode Indication (CMI) - The in-band information that reports the codec mode currently being applied.
- Initial Codec Mode (ICM) - The codec mode used to start speech coding at call setup or after handover.
- RATSCCH - Robust AMR Traffic Synchronized Control Channel, the in-band mechanism for AMR configuration changes.
Who uses SIST EN 301 709 V7.2.1:2003?
SIST EN 301 709 V7.2.1:2003 is used by GSM handset and base-station designers, radio software developers, network engineers, and interoperability test teams. It is also relevant to operators and quality managers who need to configure AMR behavior, thresholds, handover behavior, and TFO-related codec control. Buyers use it to check whether equipment supports AMR link adaptation at the MS and BSS sides.
What changed in SIST EN 301 709 V7.2.1:2003 from the previous edition?
SIST EN 301 709 V7.2.1:2003 is Version 7.2.1 and the change control history records updates for publication, clarification of codec mode identification within the Active Codec Set, introduction of RATSCCH for AMR, and transmission phase handling for AMR in-band information.
Which standards are used with SIST EN 301 709 V7.2.1:2003?
The document cites these companion and referenced GSM standards:
- GSM01.04 - provides abbreviations and acronyms used with GSM terms.
- GSM04.08 - supplies layer 3 signalling used for call setup, handover, and configuration.
- GSM05.02 - defines multiplexing and multiple access on the radio path, including frame alignment.
- GSM05.03 - defines channel coding for the in-band signalling and RATSCCH messages.
- GSM05.05 - covers radio transmission and reception, including receiver performance.
- GSM08.08 - covers the MSC-BSS interface layer 3 specification.
- GSM08.62 - defines Tandem Free Operation behavior for speech codecs.
What does the SIST EN 301 709 V7.2.1:2003 document contain?
SIST EN 301 709 V7.2.1:2003 contains a high-level AMR block diagram, message formats for Codec Mode Indication, Command, Request, and RATSCCH messages, and the rules for timing those messages on speech frames. It also includes threshold and hysteresis definitions for codec adaptation, including how the network signals them and how the MS uses them to decide on the next mode. Annex A gives an example link-quality estimation method, Annex B gives example decision thresholds, and Annex C explains how AMR codec adaptation works when TFO is active. Annex D records the change control history.
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Frequently Asked Questions
SIST EN 301 709 V7.2.1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Digital cellular telecommunications system (Phase 2+) (GSM); Link Adaptation (GSM 05.09 version 7.2.1 Release 1998)". This standard covers: CR SMG#30, 31
CR SMG#30, 31
SIST EN 301 709 V7.2.1:2003 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 301 709 V7.2.1:2003 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); Link Adaptation (GSM 05.09 version 7.2.1 Release 1998)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 301 709 Version 7.2.1SIST EN 301 709 V7.2.1:2003en01-december-2003SIST EN 301 709 V7.2.1:2003SLOVENSKI
STANDARD
ETSIEN301709V7.2.1(2000-10)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);LinkAdaptation(GSM05.09version7.2.1Release1998)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)2(GSM05.09version7.2.1Release1998)ReferenceREN/SMG-020509Q7R1KeywordsDigitalcellulartelecommunicationssystem,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 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)3(GSM05.09version7.2.1Release1998)ContentsIntellectualPropertyRights.4Foreword.41Scope.51.1References.51.2Abbreviations.52General.63AdaptiveMulti-Rateinbandcontrolandlinkadaptation.63.1Generaloperation.63.1.1OperationwithoutTandemFreeOperation.63.1.2OperationwithongoingTandemFreeOperation.73.1.3OperationathandoverwithongoingTandemFreeOperation.73.2InbandSignalling.73.2.1FrequentinbandsignallingforAMRcodecmodeadaptation.83.2.1.1Generalaspects.83.2.1.2OperationwithDTXenabled.83.2.1.3Transmitter/ReceiverSynchronisation.83.2.2RobustinbandsignallingforAMRconfigurationmodification.83.2.2.1Generalaspects.83.2.2.2RATSCCHprotocol.93.2.2.3RATSCCHmessages.103.2.2.3.1ACK_OKmessage.103.2.2.3.2ACK_ERRmessage.103.2.2.3.3ACK_UNKNOWNmessage.103.2.2.3.4CMI_PHASE_REQmessage.103.2.2.3.5AMR_CONFIG_REQmessage.113.2.2.3.6THRESH_REQmessage.123.3Codecmodeadaptation.123.3.1Channelqualitymeasure.123.3.2GenerationofCodecModeCommandsandRequests.133.3.3Performancerequirements.133.3.3.1MSresponsetotheCodecModeCommand.133.3.3.2BTSresponsetotheCodecModeRequest.133.3.3.3PerformanceoftheCodecModeRequestGeneration.133.4Setupprocedures.143.4.1DefinitionoftheAMRActiveCodecSet.143.4.2DefinitionofCodecModeCommand/Requestdecisionthresholds.143.4.3InitialCodecModeSelectionatCallSetupandHandover.15AnnexA(informative):ExampleSolutionforLinkqualityestimation.16AnnexB(informative):ExampleDefinitionofModeCommand/Requestdecisionthresholds.17AnnexC(informative):PrinciplesforAMRcodecmodeadaptationwithTFO.18C.1Downgrading.18C.1.1Uplinkdowngrading.18C.1.2Downlinkdowngrading.19C.2Upgrading.20C.2.1Downlinkupgrading.20C.2.2Uplinkupgrading.21AnnexD(informative):Changecontrolhistory.22History.23SIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)4(GSM05.09version7.2.1Release1998)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).ThepresentdocumentspecifiestherelevantproceduresforlinkadaptationimplementedintheMobileStation(MS)andBaseStationSystem(BSS)ofthedigitalmobilecellularandpersonalcommunicationsystemsoperatinginthe900MHz,1800MHzand1900MHzband(GSM900,DCS1800andPCS1900).ThecontentsofthepresentdocumentaresubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocumentitwillthenberepublishedbyETSIwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version7.x.ywhere:7indicatesrelease1998ofGSMPhase2+.xtheseconddigitisincrementedforallchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.NationaltranspositiondatesDateofadoptionofthepresentdocument:1September2000Dateoflatestannouncementofthepresentdocument(doa):31December2000DateoflatestpublicationofnewNationalStandardorendorsementofthepresentdocument(dop/e):30June2001DateofwithdrawalofanyconflictingNationalStandard(dow):30June2001SIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)5(GSM05.09version7.2.1Release1998)1ScopeTherequirementsdescribedinthepresentdocumentaremandatoryforimplementationinallGSMMSsandBSSscapableofsupportingtheAdaptiveMulti-Ratespeechtrafficchannel,unlessotherwisestated.Unlessotherwisespecified,referencestoGSMincludeGSMatanyfrequencyband.1.1ReferencesThefollowingdocumentscontainprovisionswhich,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]GSM04.08:"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacelayer3specification".[3]GSM05.02:"Digitalcellulartelecommunicationssystem(Phase2+);Multiplexingandmultipleaccessontheradiopath".[4]GSM05.03:"Digitalcellulartelecommunicationssystem(Phase2+);ChannelCoding".[5]GSM05.05:"Digitalcellulartelecommunicationssystem(Phase2+);Radiotransmissionandreception".[6]GSM08.08:"Digitalcellulartelecommunicationssystem(Phase2+);Mobile-servicesSwitchingCentre-BaseStationSystem(MSC-BSS)interface,Layer3specification".[7]GSM08.62:"Digitalcellulartelecommunicationssystem;InbandTandemFreeOperation(TFO)ofSpeechCodecs".1.2AbbreviationsForthepurposeofthepresentdocumrnt,thefollowingabbreviationsapply.FurtherGSMrelatedabbreviationsarelistedinGSM01.04.ACSActiveCodecSetAMRAdaptiveMulti-RateCMCCodecModeCommandCMICodecModeIndicationCMRCodecModeRequestICMInitialCodecModeRATSCCHRobustAMRTrafficSynchronizedControlChannelSIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)6(GSM05.09version7.2.1Release1998)2GeneralThepresentdocumentgivesthedetailedrequirementsforthecorrectoperationofincallservicespecificlinkadaptationandcontrolforGSMservicesimplementedinGSMMobileStations(MS)sandBaseStationSystems(BSS)s.FortheAdaptiveMulti-Rate(AMR)speechservice,thedetaileddescriptionandrequirementsfortheassociatedinbandsignaling,AMRcodecmodeadaptation,andAMRcodecconfigurationaregiven.AninbandsignalingchannelisdefinedforAMRwhichenablestheMSandtheBTStoexchangemessagesonappliedorrequestedspeechandchannelcodecmodes.CodecmodeadaptationforAMRisbasedonreceivedchannelqualityestimationinbothMSandBTS,followedbyadecisiononthemostappropriatespeechandchannelcodecmodetoapplyatagiventime.TheoveralloperationofAMR,intermsofusedcodecmodesaswellasgeneraladaptationbehaviouriscontrolledbythenetwork.3AdaptiveMulti-Rateinbandcontrolandlinkadaptation3.1Generaloperation3.1.1OperationwithoutTandemFreeOperationAhigh-levelblockdiagramofthecompleteAMRsystemisdepictedinfigure1.ThesystemconsistsofthemajorcomponentsTRAUandBTSonthenetworksideandtheMS.Onthenetworkside,speechencoder(SPE)andchannelencoder(CHE)aswellaschanneldecoder(CHD)andspeechdecoder(SPD)areconnectedviatheserialA-bisinterface.Foreachlink,qualityinformationisderivedbyestimatingthecurrentchannelstate.Basedonthechannelstate,andalsotakingintoconsiderationpossibleconstraintsfromnetworkcontrol,thecodecmodecontrol,whichislocatedonthenetworkside,selectsthecodecmodestobeapplied.Thechannelmodetouse(TCH/AFSorTCH/AHS)iscontrolledbythenetwork.Uplinkanddownlinkalwaysapplythesamechannelmode.Forcodecmodeadaptationthereceivingsideperformslinkqualitymeasurementsoftheincominglink.ThemeasurementsareprocessedyieldingaQualityIndicator.Foruplinkadaptation,theQualityIndicatorisdirectlyfedintotheULmodecontrolunit.ThisunitcomparestheQualityIndicatorwithcertainthresholdsandgenerates,alsoconsideringpossibleconstraintsfromnetworkcontrol,aCodecModeCommandindicatingthecodecmodetobeusedontheuplink.TheCodecModeCommandisthentransmittedinbandtothemobilesidewheretheincomingspeechsignalisencodedinthecorrespondingcodecmode.Fordownlinkadaptation,theDLModeRequestGeneratorwithinthemobilecomparestheDLQualityindicatorwithcertainthresholdsandgeneratesaCodecModeRequestindicatingthepreferredcodecmodeforthedownlink.TheCodecModeRequestistransmittedinbandtothenetworksidewhereitisfedintotheDLModeControlunit.Thisunitgenerallygrantstherequestedmode.However,consideringpossibleconstraintsfromnetworkcontrol,itmayalsooverridetherequest.Theresultingcodecmodeisthenappliedforencodingoftheincomingspeechsignalindownlinkdirection.Bothforuplinkanddownlink,thepresentlyappliedcodecmodeistransmittedinbandasCodecModeIndicationtogetherwiththecodedspeechdata.Atthedecoder,theCodecModeIndicationisdecodedandappliedfordecodingofthereceivedspeechdata.SIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)7(GSM05.09version7.2.1Release1998)MSBTSTRAUULcodecmode(received)UL-ModeCtrlUL-Meas.SPESPECHECHDSPDCHDCHESPDDL-Meas.DL-ModeCtrlDLcodecmodeULModeCommandULQualityIndicatorULModeCommand(received)DLModeRequest(received)speechdataspeechdataDLcodecmode(received)networkcontrolDL-Req.GenDLQualityIndicatorDLModeRequestFigure1:HighlevelAMRblockdiagramCodecmodeselectionisdonefromasetofcodecmodes(ACS,ActiveCodecSet),whichmayinclude1to4AMRcodecmodes.Associatedwiththissetisalistof1to3switchingthresholdsandhysteresisesusedbytheDLModeRequestGeneratorandtheULmodecontrolunittogeneratetheCodecModeRequestsandCodecModeCommands.Theseconfigurationparameters(ACS,thresholds,hysteresises)aredefinedatcallsetupandcanbemodifiedathandoverorduringacall.3.1.2OperationwithongoingTandemFreeOperationIftandemfreeoperationisongoing(seeGSM08.62)thenthespeechsignalhastobetransmittedovertworadiolinks,firstuplink(MS1toBTS1)andthendownlink(BTS2toMS2),respectivelysymmetricallyinthereversedirection.TheoptimalCodecModeindirectionMS1toMS2shallbederivedfromtheCodecModeRequestforthefirstuplink(CMC1,withinBTS1)andtheCodecModeRequestderivedfortheseconddownlink(CMR2withinMS2)inthefollowingway:MS2shallsendtheCMR2backtoBTS2intheusualway.BTS2shalleitheracceptthisCMR2(default)ormaymodifyitaccordingtonetworkcontrolneeds:CMR2´.ThenBTS2shallsendtheCMR2´furtheruplinktoitsTRAU2,toTRAU1anddownlinktoBTS1(seeGSM08.62onhowthistransmissionshallbehandledonAbisandAinterfaces).BTS1combinesthereceivedCMR2´withitsownderivedCMC1bytakingtheminimumofbothvalues.Ifneeded,BTS1maymodifythisminimumvalueaccordingtoownnetworkcontrol(-->CMC1´´)andshallsenditfinallydownlinktoMS1asCMC.Theidenticalprocedureshallbeperformedinthereversedirection.AnnexCgivesaninformativedescription.3.1.3OperationathandoverwithongoingTandemFreeOperationBeforeandduringanhandoveratoneorbothsidesoftheMS-to-MSconnection,itmaybeneededtofreezethecodecmodeadaptationforashortwhile,e.g.tooptimisethecommonActiveCodecSet,ortoallowfast(re-)synchronisationbetweenBTSandTRAUortooptimisetheCMIPhaseindownlink.BothBTSsmaythereforeenableordisablethecodecmodeadaptation(seeGSM08.62).Aslongasthecodecmodeadaptationisfrozentoaspecificcodecmode,thenthiscodecmodeshallbeusedinbothdirectionsaslongastandemfreeoperationisongoing,ortandemfreeoperationshallbediscontinued.TheCodecModeRequestsfromtheMSsmaybetakenintoaccounttodecidewhethertocontinueTFOornot,butnotforcodecmodeadaptation.3.2InbandSignallingTheAMRinbandsignallingconsistsoftwoparts:-Frequentsignalling,usedforCodecModeIndicationandCodecModeCommand/Request.-Robust,lessfrequentsignalling,basedonframestealing,usedforchangingtheAMRconfiguration(RATSCCH).SIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)8(GSM05.09version7.2.1Release1998)3.2.1FrequentinbandsignallingforAMRcodecmodeadaptation3.2.1.1GeneralaspectsThecodecmodeinformation,whichhastobetransmittedoneachlink,consistsofCodecModeIndicationsandCodecModeCommandsinthedownlink,respectivelyCodecModeIndicationsandCodecModeRequestsintheuplink.CodecModeIndicationsinformthereceiveraboutthecurrentlyappliedcodecmode.CodecModeCommandsinformtheotherendaboutthecodecmodetobeappliedontheotherlink.CodecModeRequestsinformtheotherendaboutthepreferredcodecmodeontheotherlink.Codecmodeinformationistransmittedinbandinthespeechtrafficchannel,usingapartofitstransmissioncapacity.Thecodingofcodecmodesintheinbandsignallingisgiveninsubclause3.4.1.ChannelcodingofcodecmodeinformationisspecifiedinGSM05.03[4]forallframetypes.Codecmodesareconstrainedtochangeonlyeverysecondspeechframe.CodecModeCommands/RequestsandCodecModeIndicationsaresub-sampledsuchthattheyoccuronlyeverysecondframe.CodecModeIndicationsandCodecModeCommands/Requestsshallbetransmittedalternatingwithinconsecutivespeechframes.Both,CodecModeIndicationandCodecModeCommand/Request,shallbetransmittedtogetherwithineveryRATSCCHframe.3.2.1.2OperationwithDTXenabledForSID_FIRSTframes,theCodecModeIndicationorCodecModeCommand/Requestinphasewiththealternatingtransmissionshallbetransmitted(samephaseasinspeechframes).Both,CodecModeIndicationandCodecModeCommand/Request,shallbetransmittedtogetherineverySID_UPDATEframe(asinRATSCCHframes).ForONSETframestheCodecModeIndicationforthesubsequentspeechframeshallbetransmitted,regardlessofthephaseoftheinbandsignalling.Thegeneralphaseoftheinbandsignallingshallnotbechangedbythat.3.2.1.3Transmitter/ReceiverSynchronisationThealternatingtransmissionofthecodecmodeinformationrequiressynchronisationoftransmittingandreceivingends,suchthatCodecModeIndicationsandCodecModeCommands/Requestsaredecodedincorrectorder.Toensurepropersynchronisation,thecodecmodeinformationshallbetransmittedalignedtothe(SACCH)multi-framestructureoftheGSMsystem.ForTCH/AFS,thedefaulttransmissionphaseshallbesuchthatCodecModeIndicationsaresentalignedwithTDMAframe0intheuplinkandwithTDMAframe4inthedownlinkasdefinedinGSM05.02[3].ForTCH/AHS,thedefaulttransmissionphaseshallbesuchthatModeIndicationsaresentalignedwithTDMAframe0or1dependingonthesubchannelintheuplinkandwithTDMAframe4or5dependingonthesubchannel,inthedownlink,asdefinedinGSM05.02[3].ThisdefaultphaseoftheCodecModeIndicationindownlinkdirectioniscalled"odd",thealternativephase,onespeechframeshifted,iscalled"even".Thephaseinuplinkisalwaysthesameandisneverchanged.Atcallsetupandaftereveryhandoverthedefaultphase(odd)shallbeusedindownlinkdirection.Duringacall,thephaseofCodecModeIndicationmaybechangedindownlinkbyusingaRATSCCHmessage.IncaseofhandoverfailureandfallbacktotheBTSbeforethehandoverattempt,thephasebeforethehandoverattemptshallbeusedagain.3.2.2RobustinbandsignallingforAMRconfigurationmodification3.2.2.1GeneralaspectsTheRATSCCHmechanismmaybeusedincaseofTandemFreeOperationtomodifytheAMRConfigurationontheradiointerfacewithoutinterruptionofthespeechtransmission.ItsapplicationforTFOisdescribedinGSM08.62.ThisrecommendationdefinestheRATSCCHprotocolandtheRATSCCHmessages.ThechannelcodingisdefinedinGSM05.03andthereceiverperformanceinGSM05.05.RATSCCHhandlingismandatoryforMSandoptionalforBTS.SIST EN 301 709 V7.2.1:2003
ETSIETSIEN301709V7.2.1(2000-10)9(GSM05.09version7.2.1Release1998)RATSCCHisbasedonframestealing.OnTCH/AFS,onespeechframeisstolenforeachRATSCCHmessage,andonTCH/AHStwospeechframesarestolen.InTCH/AHSRATSCCHismappedontotwoconsecutivespeechframes,theRATSCCH_MARKERandtheRATSCCH_DATA.Bothshallbesentalwaysasonepair.FACCHframeshavehigherprioritythanRATSCCHframes.IfFACCHandRATSCCHarescheduledfortransmissionforthesamespeechframe,thentheFACCHshallbesentfirst,followedbytheRATSCCH.IftheRATSCCHisdelayedduetoFACCH,thentheappropriatecounters(seesubclause3.2.2.2)shallalsobestartedone(TCH/AFS)respectivelytwo(TCH/AHS)frameslater.IfinthecaseofTCH/AHS,FACCHstealsthesecondframeofoneRATSCCHmessage(RATSCCH_DATA),thecompleteRATSCCHmessage(RATSCCH_MARKERandRATSCCH_DATA)shallbesentfollowingtheFACCHframe.3.2.2.2RATSCCHprotocolTheRATSCCHprotocolelementsconsistofanumberofREQuestMessagesandthreeACKnowledgementMessages.OneinformationexchangeconsiststypicallyofoneREQ-ACKcyclebetweenthe"Initiator"andthe"Addressee".WhiletheInitiatoriswaitingforanACK,itshallnotsendanynewREQmessage,i.e.transmissionandacknowledgementofoneREQ-ACKcycleshallbecompletedbeforethenextcycleisstarted.ACKmessages,asreactiontoreceivedREQmessages,shallalwaysbesentbackassoonaspossible,andlatestwithin3speechframes.BothsidesshallcontinuouslymonitortheradioreceptionfortheRATSCCHpatternanddecodetheRATSCCHmessage.ThetypicalREQ-ACKcycleisdefinedas:1)Ifoneside("Initiator")wantstoinitiatetheinformationexchange,itshallsendthedesiredREQmessage.AtthesametimetheInitiatorshallstarttwocounters:ACK_Timeoutthatshallcounttheelapsedspeechframes(afterREQ)inreceivedirectionandREQ_ActivationthatshallcounttheelapsedspeechframesafterREQinsenddirection.2)IftheREQmessagewasdecodederror-free(byCRCcheck,seeGSM05.03[4])andisdefined(seesubclause3.2.2.3)atreceiverside("Addressee"),thentheAddresseeshallsendanACK_OKmessageback.AtthesametimetheAddresseeshallstart(orrestart)twoowncounters:REQ_ActivationthatshallcounttheelapsedspeechframesafterREQinreceivedirectionandACK_ActivationthatshallcounttheelapsedspeechframesafterACKinsenddirection.3)IftheInitiatorreceivesanACK_OK,thenitshallignoreitsACK_TimeoutcounterandshallstartanACK_ActivationcounterinsteadthatshallcounttheelapsedspeechframesafterACK_OKinreceivedirection.4)ThecontentsoftheREQmessagesshallbecomevalidinthedirectionfromInitiatortoAddresseeexactlyinthatframe,wheretheREQ_Activationcountersreachthevalue12andforallfollowingframes.ThecontentsoftheREQmessageshallbecomevalidinthedirectionfromAddresseetoInitiatorexactlyinthatframe,wheretheACK_Activationcountersreachthevalue12andforthefollowingframes.NOTE:DuetothetransmissiondelayandthereactiontimewithintheAddressee(REQtoACK)theactivationtakesplaceingeneralatfourdifferentpointsintime,butexactlysynchronisedanddefinedinbothdirections.ErrorHandling:1)IftheREQmessagewasdecodederror-free(noCRCerror),butthemessageisnotdefinedattheAddresseeside,thentheAddresseeshallsendanACK_UNKNOWNmessageback.Nocountersareneededinthiscase.TheInitiator,whenreceivingthisACK_UNKNOWNmessageshallterminatetheexchangeforthistypeofREQmessage.2)IftheRATSCCHmessagewasdetected,butcouldnotbedecodedcorrectly(CRCfailure),oritscontentswasnotconsistent,thentheAddresseeshallsendanACK_ERRmessageback.Nocountersareneededinthiscase.3)IftheI
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