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)
General Information
- 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
Overview
SIST EN 301 709 V7.2.1:2003 is a European standard specifying procedures for link adaptation in the digital cellular telecommunications system (GSM Phase 2+). Developed by SIST and identical to EN 301 709 (version 7.2.1 Release 1998) as published by ETSI, this standard outlines the requirements for implementing link adaptation strategies within both the Mobile Station (MS) and Base Station System (BSS). The main objective is to optimize the transmission quality and efficiency of Adaptive Multi-Rate (AMR) speech channels in GSM networks, ensuring better voice quality, robust performance, and efficient use of radio resources across various frequency bands including GSM900, DCS1800, and PCS1900.
Key Topics
- Link Adaptation Protocols: Specifies algorithms and procedures to dynamically select channel coding and transmission modes according to real-time radio link conditions, aiming to maximize voice quality and minimize transmission errors.
- Adaptive Multi-Rate (AMR) Codec Management: Details the mechanisms for adapting AMR codec modes based on channel quality estimations, supporting smooth transitions and robust operation during varying network states and radio environments.
- In-band Signalling for Codec Control: Describes methods for frequent and robust signalling of codec mode commands, requests, and indications within the traffic channel, allowing real-time adaptation without additional signalling overhead.
- Handling Tandem Free Operation (TFO): Provides procedures for codec mode adaptation in scenarios where speech signals are relayed directly between MSs across multiple links, helping maintain optimal speech quality.
- Robust Control Channels (RATSCCH): Defines in-band control for AMR configuration changes, enabling modifications without interrupting ongoing speech services.
- Thresholds and Hysteresis: Outlines the configuration of switching thresholds and hysteresis to avoid rapid, undesirable changes in codec modes.
Applications
The requirements of SIST EN 301 709 V7.2.1:2003 are mandatory for any GSM system supporting Adaptive Multi-Rate speech channels. Key applications include:
- Mobile Network Equipment Vendors: Ensuring that base stations and mobile stations interoperate seamlessly for adaptive speech transmission.
- Mobile Operators: Enhancing voice service quality by dynamically adjusting speech coding rates based on channel quality, leading to improved user experience and network efficiency.
- Compliance Testing and Certification: Providing a clear benchmark for equipment conformance, vital for market entry and regulatory approval.
- Network Modernization Projects: Assisting in the upgrade of legacy GSM networks with support for advanced speech codecs and adaptive features.
- Research in Mobile Communications: Serving as a technical reference for studies into link adaptation, codec management, and radio resource optimization in GSM systems.
Related Standards
To fully implement and understand the link adaptation procedures in GSM systems, the following related standards should be consulted:
- GSM 01.04: Abbreviations and acronyms used in GSM specifications
- GSM 04.08: Mobile radio interface layer 3 specification
- GSM 05.02: Multiplexing and multiple access on the radio path
- GSM 05.03: Channel coding
- GSM 05.05: Radio transmission and reception requirements
- GSM 08.08: MSC-BSS interface layer 3 specification
- GSM 08.62: In-band Tandem Free Operation (TFO) of Speech Codecs
These interconnected standards ensure comprehensive coverage of all technical aspects needed for high-performance GSM speech services, codec control, and adaptive resource management.
Keywords: GSM standard, link adaptation, Adaptive Multi-Rate (AMR), codec management, speech quality, mobile telecommunications, radio interface, SIST EN 301 709, GSM Phase 2+, in-band signalling, mobile station, base station system, ETSI standard.
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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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