SIST EN 301 709 V8.0.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Link Adaptation (GSM 05.09 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 301 709 V8.0.1:2003 is the SIST adoption of the ETSI European Standard for GSM link adaptation, published as GSM 05.09 version 8.0.1 for Release 1999. It specifies how Adaptive Multi-Rate (AMR) speech traffic channels use in-band signalling, codec mode adaptation, and AMR configuration in GSM Mobile Stations (MS) and Base Station Systems (BSS). It is written for GSM equipment that supports AMR speech traffic channels and is identified here as an upgrade to R99.
What does SIST EN 301 709 V8.0.1:2003 specify?
SIST EN 301 709 V8.0.1:2003 specifies the detailed procedures for in-call link adaptation and control in GSM MSs and BSSs that support AMR speech traffic channels. In practice, it tells implementers how the radio link quality drives codec mode changes, how the two ends signal those changes, and how AMR configuration is set up and modified during a call.
The document is organized into:
- Clause 1 - Scope, references, and abbreviations
- Clause 2 - General description of AMR link adaptation
- Clause 3 - AMR in-band control and link adaptation, including signalling, codec mode adaptation, and setup procedures
- Annexes A to D - informative examples, principles, and change 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 V8.0.1:2003?
SIST EN 301 709 V8.0.1:2003 makes AMR adaptation depend on measured channel quality and network-controlled codec mode selection. The practical result is that both ends must measure link quality, compare it with thresholds, and change codec modes in a controlled way rather than switching freely.
In-band signalling
Clause 3.2 defines two signalling paths:
- Frequent in-band signalling for Codec Mode Indication, Codec Mode Command, and Codec Mode Request
- Robust in-band signalling, based on RATSCCH, for AMR configuration changes
The frequent signalling is sent every second speech frame and aligned to the GSM multiframe structure. For a reader, this means the implementation must keep signalling and speech timing synchronized so the other end decodes the right mode at the right frame.
RATSCCH handling
Clause 3.2.2 defines RATSCCH as the mechanism for changing AMR configuration without interrupting speech. It uses REQuest messages and three acknowledgement messages: ACK_OK, ACK_ERR, and ACK_UNKNOWN. The protocol also defines how retransmission, activation timing, and error handling work, which matters for reliable remote reconfiguration during a call.
Codec mode adaptation
Clause 3.3 requires codec mode adaptation to use a normalized one-dimensional QualityIndicator based on carrier-to-interferer ratio, C/Inorm. The MS and BSS map that quality measure to Codec Mode Commands or Requests using thresholds and hysteresis. This reduces unstable switching and helps keep mode changes tied to real radio conditions.
Active Codec Set, thresholds, and initial mode
Clause 3.4 defines the Active Codec Set (ACS) as the set of up to four codec modes used in a call. It also defines threshold and hysteresis coding, plus the Initial Codec Mode (ICM) used at call setup and after handover. For implementation, this means the network must signal the available modes and the switching boundaries, and the equipment must start from the correct initial mode if one is not explicitly signalled.
Timing and response behavior
Clause 3.3.3 sets response expectations. The MS must apply a Codec Mode Command on the next possible speech frame and no more than three speech frames later. The BTS should apply a requested mode as early as possible unless network control overrides it.
TFO behavior
Annex C gives the operating principles for AMR codec mode adaptation when Tandem Free Operation (TFO) is active. It explains how uplink and downlink decisions interact across two radio links, and why downgrading can be immediate while upgrading needs both links to be good enough.
What terms does SIST EN 301 709 V8.0.1:2003 define?
- Adaptive Multi-Rate (AMR) - the speech service that adapts codec mode to radio conditions.
- Active Codec Set (ACS) - the set of codec modes available for a call.
- Codec Mode Command (CMC) - the network-side instruction telling the MS which uplink codec mode to use.
- Codec Mode Request (CMR) - the MS-side request indicating the preferred downlink codec mode.
- Codec Mode Indication (CMI) - the in-band indication of the codec mode currently applied.
- Initial Codec Mode (ICM) - the starting codec mode used at call setup or handover.
- Robust AMR Traffic Synchronized Control Channel (RATSCCH) - the in-band mechanism for AMR reconfiguration.
- QualityIndicator - the normalized channel-quality measure used to drive codec mode adaptation.
Who uses SIST EN 301 709 V8.0.1:2003?
SIST EN 301 709 V8.0.1:2003 is used by GSM handset, radio, and base-station engineers who implement AMR speech behavior. It is also relevant to network designers and operators who configure ACS values, thresholds, handover behavior, and Tandem Free Operation. Test labs, quality teams, and buyers use it to verify that equipment supports the required in-band signalling, timing, and AMR configuration rules.
What changed in SIST EN 301 709 V8.0.1:2003 from the previous edition?
SIST EN 301 709 V8.0.1:2003 updates the specification to Version 8.0.1 for publication, following Version 8.0.0 for Release 1999. The change control history also records earlier substance updates such as the transmission phase of AMR in-band information, the introduction of RATSCCH for AMR, and clarification of codec-mode identification within the active codec set.
Which standards are used with SIST EN 301 709 V8.0.1:2003?
The document cites Release 1999 versions of these GSM references:
- GSM01.04 - abbreviations and acronyms used in GSM
- GSM04.08 - Layer 3 signalling used for ACS, thresholds, and ICM setup
- GSM05.02 - multiplexing and multiple access on the radio path
- GSM05.03 - channel coding, including AMR in-band signalling coding
- GSM05.05 - radio transmission and reception, including receiver performance
- GSM08.08 - MSC-BSS interface Layer 3 specification
- GSM08.62 - Tandem Free Operation (TFO) of speech codecs
What does the SIST EN 301 709 V8.0.1:2003 document contain?
SIST EN 301 709 V8.0.1:2003 contains a high-level AMR block diagram, detailed signalling rules, message definitions, and timing behavior for codec changes. It also includes tables for RATSCCH message formats, AMR configuration coding, threshold and hysteresis coding, and example decision thresholds. Annex A gives an example of link quality estimation, Annex B gives example thresholds, and Annex C explains adaptation with TFO. Annex D records the change control history.
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Frequently Asked Questions
SIST EN 301 709 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); Link Adaptation (GSM 05.09 version 8.0.1 Release 1999)". This standard covers: Upgrade to R99
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SIST EN 301 709 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 301 709 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); Link Adaptation (GSM 05.09 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 301 709 Version 8.0.1SIST EN 301 709 V8.0.1:2003en01-december-2003SIST EN 301 709 V8.0.1:2003SLOVENSKI
STANDARD
ETSIEN301709V8.0.1(2000-10)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);LinkAdaptation(GSM05.09version8.0.1Release1999)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 301 709 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)2(GSM05.09version8.0.1Release1999)ReferenceREN/SMG-020509Q8KeywordsDigitalcellulartelecommunicationssystem,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 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)3(GSM05.09version8.0.1Release1999)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 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)4(GSM05.09version8.0.1Release1999)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).ThepresentdocumentspecifiestherelevantproceduresforlinkadaptationimplementedintheMobileStation(MS)andBaseStationSystem(BSS)ofthedigitalmobilecellularandpersonalcommunicationsystemsoperatinginthe900MHz,1800MHzand1900MHzband(GSM900,DCS1800andPCS1900).ThecontentsofthepresentdocumentaresubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocumentitwillthenberepublishedbyETSIwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version8.x.ywhere:8indicatesrelease1999ofGSMPhase2+.xtheseconddigitisincrementedforallchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.NationaltranspositiondatesDateofadoptionofthisEN:1September2000DateoflatestannouncementofthisEN(doa):31December2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):30June2001DateofwithdrawalofanyconflictingNationalStandard(dow):30June2001SIST EN 301 709 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)5(GSM05.09version8.0.1Release1999)1ScopeTherequirementsdescribedinthepresentdocumentaremandatoryforimplementationinallGSMMSsandBSSscapableofsupportingtheAdaptiveMulti-Ratespeechtrafficchannel,unlessotherwisestated.Unlessotherwisespecified,referencestoGSMincludeGSMatanyfrequencyband.1.1ReferencesThefollowingdocumentscontainprovisionswhich,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]GSM04.08:"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".1.2AbbreviationsForthepurposesofthepresentdocument,thefollowingabbreviationsapply.FurtherGSMrelatedabbreviationsarelistedinGSM01.04.AMRAdaptiveMulti-RateACSActiveCodecSetCMCCodecModeCommandCMICodecModeIndicationCMRCodecModeRequestICMInitialCodecModeRATSCCHRobustAMRTrafficSynchronizedControlChannelSIST EN 301 709 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)6(GSM05.09version8.0.1Release1999)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 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)7(GSM05.09version8.0.1Release1999)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 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)8(GSM05.09version8.0.1Release1999)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 V8.0.1:2003
ETSIETSIEN301709V8.0.1(2000-10)9(GSM05.09version8.0.1Release1999)RATSCCHisbasedonframestealing.OnTCH/AFS,onespeechframeisstolenforeachRATSCCHmessage,andonTCH/AHStwospeechframesarestolen.InTCH/AHSRATSCCHismappedontotwoconsecutivespeechframes,theRATSCCH_MARKERandtheRATSCCH_DATA.Bothshallbesentalwaysasonepair.FACCHframeshavehigherprioritythanRATSCCHframes.IfFACCHandRATSCCHarescheduledfortransmissionforthesamespeechframe,thentheFACCHshallbesentfirst,followedbytheRATSCCH.IftheRATSCCHisdelayedduetoFACCH,thentheappropriatecounters(see3.2.2.2)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.Nocountersare
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