SIST EN 300 912 V8.3.1:2003

• Abstract:

  05.10; s31b; CR: A054; R99; 8.2.0; 8.3.0; EGPRS Classic to COMPACT BTS synchronisation 05.10; s31b; CR: A056; R99; 8.2.0; 8.3.0; BTS Synchronisation, Location Accuracy and LMU update rates

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.070.50 - Global System for Mobile Communication (GSM)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Ref Project: ETSI EN 300 912 V8.3.1 (2000-10) - Digital cellular telecommunications system (Phase 2+) (GSM); Radio subsystem synchronization (GSM 05.10 version 8.3.1 Release 1999)

Overview

SIST EN 300 912 V8.3.1:2003 establishes the requirements for radio subsystem synchronization within the Digital Cellular Telecommunications System (Phase 2+) - globally recognized as GSM. Developed by the European Telecommunications Standards Institute (ETSI) and adopted as a Slovenian national standard by SIST, this specification (aligned with GSM 05.10 v8.3.1 Release 1999) addresses the mechanisms and criteria to synchronize various network elements, such as Base Transceiver Stations (BTS), Mobile Stations (MS), and CTS Fixed Parts (CTS-FP), ensuring reliable network timing, location accuracy, and efficient handover operations.

The standard supports both classic EGPRS and COMPACT BTS synchronization, focusing on aspects essential for accurate communication, quick mobility management, and overall network efficiency in GSM 900, DCS 1800, and compatible bands.

Key Topics

• Radio Subsystem Synchronization: Specifies timing and frequency synchronization methods and requirements for GSM network components.
• Base Transceiver Station (BTS) Requirements: Outlines the use of highly accurate frequency sources, timebase counter alignment, timing advance estimation, timeslot management, and delay tracking techniques.
• Mobile Station (MS) Requirements: Details the need for accurate frequency reference, internal timebase maintenance, alignment of uplink transmissions, and use of timing advance signals.
• Location Accuracy and Tracking: Supports enhanced location-based services through precise synchronization and timing measurement procedures, including reporting of Observed Timing Difference (OTD) and Frequency Offset (OFO).
• Synchronization for COMPACT and EGPRS: Facilitates transitions between classic and COMPACT cell types and stipulates extra requirements for pseudo-synchronized and synchronized handovers.
• CTS Support: Defines synchronization processes for the GSM Cordless Telephone System (CTS), including CTS-FP and CTS-MS interactions.
• Delay and Handover Procedures: Describes how devices manage timing adjustments during handovers, channel changes, and in variable network conditions.
• Optional Features: Incorporates flexibility for certain configurations, such as pico-BTS, and supports vendor-defined synchronization algorithms.

Applications

The requirements and guidelines provided by SIST EN 300 912 V8.3.1:2003 are applied in several key GSM network scenarios:

• Mobile Network Deployment: Ensures newly installed BTS and MS equipment can reliably synchronize across a GSM network, minimizing interference and maximizing spectrum efficiency.
• Handover Efficiency: Enhances mobile user experience by supporting accurate timing for smooth handovers between cells, ensuring minimal dropped connections during movement.
• Advanced Services Enablement: Precise synchronization forms the foundation for location-based services, emergency response location, and optimized resource allocation in GSM networks.
• EGPRS and COMPACT Operations: Supports efficient network adaptation for evolving technologies, aiding operators in flexible service deployment.
• Inter-Operator Compatibility: Harmonizes synchronization standards across different manufacturers and operators, enabling interoperability and streamlined network upgrades.

Related Standards

For comprehensive GSM radio subsystem synchronization and related operations, refer to the following standards closely associated with SIST EN 300 912 V8.3.1:2003:

• GSM 05.02 - Multiplexing and Multiple Access on the Radio Path
• GSM 05.05 - Radio Transmission and Reception
• GSM 05.08 - Radio Subsystem Link Control
• GSM 03.60 / GSM 03.64 - General Packet Radio Service (GPRS) procedures and radio interface
• GSM 04.08 - Mobile Radio Interface Layer 3 Specification
• GSM 03.30 - Radio Network Planning Aspects
• GSM 03.52 / GSM 05.56 - GSM Cordless Telephony System (CTS) radio interface specifications

Using SIST EN 300 912 in conjunction with these foundational GSM standards ensures that network elements meet synchronization and performance requirements for modern digital cellular systems. This harmonized approach is essential for operators, system integrators, and equipment manufacturers seeking to deliver robust, reliable GSM communications.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2+) (GSM); Radio subsystem synchronization (GSM 05.10 version 8.3.1 Release 1999)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 300 912 Version 8.3.1SIST EN 300 912 V8.3.1:2003en01-december-2003SIST EN 300 912 V8.3.1:2003SLOVENSKI
STANDARD
ETSIEN300912V8.3.1(2000-10)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);Radiosubsystemsynchronization(GSM05.10version8.3.1Release1999)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)2(GSM05.10version8.3.1Release1999)ReferenceREN/SMG-020510Q8R1KeywordsDigitalcellulartelecommunicationssystem,GlobalSystemforMobilecommunications(GSM)ETSI650RoutedesLuciolesF-06921SophiaAntipolisCedex-FRANCETel.:[phone]Fax:[phone]SiretN°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:[e-mail]opartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)3(GSM05.10version8.3.1Release1999)ContentsIntellectualPropertyRights.5Foreword.51Scope.61.1References.61.2Definitionsandabbreviations.72Generaldescriptionofsynchronizationsystem.73Timebasecounters.83.1Timingstateofthesignals.83.2Relationshipbetweencounters.84Timingoftransmittedsignals.95BTSRequirementsforSynchronization.95.1Frequencysource.95.2Timebasecounters.105.3InternalBTScarriertiming.105.4InitialTimingadvanceestimation.105.5Maximumtimingadvancevalue.105.6Delaytracking.105.6.1Forcircuitswitchedchannels.105.6.2Forpacketswitchedchannels.105.6.3Delayassessmenterror.115.6.4Pico-BTSdelaytracking.115.7Timeslotlength.115.8RangeofTimingadvance.116MSRequirementsforSynchronization.116.1MScarrierfrequency.126.2Internaltimebase.126.3AssessmentofBTStiming.126.4Timingoftransmission.126.5ApplicationofTimingAdvance.126.5.1Forcircuitswitchedchannels.126.5.2Forpacketswitchedchannels.126.6AccesstoanewBTS.136.7Temporarylossofsignal.146.8Timingofintracellchannelchange.146.9ApplicationofnewTimingAdvancevalue.146.10Definitionof"readytotransmitwithinxms".146.11DefinitionofadditionalreactiontimesforGPRSmobilestations.146.11.1Uplinkanddownlinkassignmentreactiontimes.146.11.2Changeinchannelcodingschemecommandedbynetwork.146.11.3Contentionresolutionreactiontime.156.11.4Reactiontimeinresponsetoothercommandingmessages.156.12ObservedFrequencyOffset(OFO)reportedbytheCTS-MS.157CTS-FPRequirementsforSynchronization.157.1Frequencysourcedefaultrequirements.157.2FrequencysourceforaCTS-FPassistedbyaCTS-MS.157.3InternalCTS-FPcarriertiming.157.4Timeslotlength.157.5AssessmentofCTS-MSdelay.16SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)4(GSM05.10version8.3.1Release1999)AnnexA(normative):Additionalrequirementsforpseudo-synchronization,synchronizedhandoversandpseudo-synchronizedhandovers.17A.1Generaldescriptionsanddefinitions.17A.1.1Conventions.17A.1.2Definitions.17A.1.3Detailsofoperations.17A.2BTSrequirements.18A.2.1Thepseudo-synchronizationscheme.18A.2.1.1BTSatimedifferenceestimate.18A.2.1.2Thereceptionepochcriterion.18A.2.1.3Pseudo-synchronizedhandover.18A.2.2Thesynchronizationrequirement.18A.3MSrequirements.19A.3.1Provisionoftimedifferenceinformation.19A.3.2Aftereachsuccessfulhandover.19A.3.3Synchronizedorapseudosynchronizedhandover.19AnnexB(informative):CTSBCHtimeslotshiftingpropertiesforCTS-MSsynchronization.20B.1DeterminationofTNbytheCTS-MSwhenCTSBCHshiftingisnotactive.20B.2DeterminationofTNbytheCTS-MSwhenCTSBCHshiftingisactive.20AnnexC(informative):BTSfrequencysourcestabilityandE-OTDLMUreportingperiodsforLCS.21C.1BTSfrequencysourcestabilityandE-OTDLMUreportingperiods.21C.2Frequencysourcestability.21C.3RelationshiptoE-OTDreportingperiods.21AnnexD(informative):Changecontrolhistory.23History.24SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)5(GSM05.10version8.3.1Release1999)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).ThepresentdocumentdefinestherequirementsforsynchronizationontheGSMradiosub-systemofthedigitalmobilecellularandpersonalcommunicationsystemsoperatinginthe900MHzand1800MHzband(GSM900andDCS1800).ThecontentsofthepresentdocumentmaybesubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocumentitwillthenbere-submittedforformalapprovalproceduresbyETSIwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version8.x.ywhere:8GSMPhase2+Release1999.xtheseconddigitisincrementedforchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.;ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.NationaltranspositiondatesDateofadoptionofthisEN:29September2000DateoflatestannouncementofthisEN(doa):31December2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):30June2001DateofwithdrawalofanyconflictingNationalStandard(dow):30June2001SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)6(GSM05.10version8.3.1Release1999)1ScopeThepresentdocumentdefinestherequirementsforsynchronizationontheradiosub-systemofthedigitalcellulartelecommunicationssystemsGSM.However,itdoesnotdefinethesynchronizationalgorithmstobeusedintheBaseTransceiverStation(BTS),CTSFixedPart(CTS-FP)andMobileStation(MS).Theseareuptothemanufacturertospecify.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]GSM03.60:"Digitalcellulartelecommunicationssystem(Phase2+);GeneralPacketRadioService(GPRS);ServiceDescriptionStage2".[3]GSM03.64:"Digitalcellulartelecommunicationssystem(Phase2+);GeneralPacketRadioService(GPRS);GPRSRadioInterfaceStage2".[4]GSM04.08:"Digitalcellulartelecommunicationssystem(Phase2+);Mobileradiointerfacelayer3specification".[5]GSM04.60:"Digitalcellulartelecommunicationssystem(Phase2+);GeneralPacketRadioService(GPRS);MobileStation(MS)-BaseStationSystem(BSSinterface;RadioLinkControl(RLC)andMediumAccessControl(MAC)LayerSpecification".[6]GSM05.02:"Digitalcellulartelecommunicationssystem(Phase2+);Multiplexingandmultipleaccessontheradiopath".[7]GSM05.05:"Digitalcellulartelecommunicationssystem(Phase2+);Radiotransmissionandreception".[8]GSM05.08:"Digitalcellulartelecommunicationssystem(Phase2+);Radiosubsystemlinkcontrol".[9]GSM03.30:"Digitalcellulartelecommunicationssystem(Phase2+);Radionetworkplanningaspects".[10]GSM03.52:"Digitalcellulartelecommunicationssystem(Phase2+);GSMCordlessTelephonySystem(CTS),Phase1;LowerlayersoftheCTSRadioInterface;Stage2".[11]GSM05.56:"Digitalcellulartelecommunicationssystem(Phase2+);GSMCordlessTelephonySystem(CTS),Phase1;CTS-FPRadiosubsystem".SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)7(GSM05.10version8.3.1Release1999)1.2DefinitionsandabbreviationsInadditiontothosebelow,abbreviationsusedinthepresentdocumentarelistedinGSM01.04.Forthepurposesofthepresentdocument,thefollowingtermsanddefinitionsapply:BTS:BaseTransceiverStation.CTS-FP:CTSFixedPart.CTS-MS:MSoperatinginCTSmode.TimingAdvance:signalsentbytheBTStotheMSwhichtheMSusestoadvanceitstimingsoftransmissionstotheBTSsoastocompensateforpropagationdelay.Quartersymbolnumber:timingofquartersymbolperiods(12/13µs)withinatimeslot.Symbolperiodcanbe1or3bitperiodsdependinguponmodulation.Timeslotnumber:timingoftimeslotswithinaTDMAframe.TDMAframenumber:countofTDMAframesrelativetoanarbitrarystartpoint.CurrentServingBTS:BTSononeofwhosechannels(TCH,DCCH,CCCHorPDCH)theMSiscurrentlyoperating.CurrentServingCTS-FP:CTS-FPononeofwhosechannels(TCHorCTScontrolchannels)theCTS-MSiscurrentlyoperating.Timebasecounters:setofcounterswhichdeterminethetimingstateofsignalstransmittedbyaBTSorMS.MStimingoffset:delayofthereceivedsignalrelativetotheexpectedsignalfromanMSatzerodistanceunderstaticchannelconditionswithzerotimingadvance.Thisisaccurateto±1symbol,andreportedonceperSACCHorafteraRACHas.required(i.e.atthesamerateastimingadvance).Forexample,foranMSwitharoundtrippropagationdelayofPsymbols,butwithatimingadvanceofTsymbols,thereportedtimingoffsetwillbeP-Tquantizedtothenearestsymbol.ForGPRStheMStimingoffsetisnotreported.TimingAdvanceIndex:TimingAdvanceIndexTAIusedforGPRS,whichdeterminesthepositionofthesubchannelonPTCCH(seeGSM05.02)usedbytheMStosendanaccessburst,fromwhichthenetworkcanderivethetimingadvance.ObservedFrequencyOffset(OFO):differenceoffrequencyofsignalsreceivedbyaCTS-MSfromaCTS-FPandaBTS.TheObservedFrequencyOffsetismeasuredandreportedbytheCTS-MSonCTS-FPrequirement.TheObservedFrequencyOffsetisexpressedinppmwithanaccuracyof1/64ppm(i.e.about0,016ppm).Timegroup(TG):usedforcompact,timegroupsshallbenumberedfrom0to3andaparticulartimegroupshallbereferredtobyitstimegroupnumber(TG)(seeGSM05.02).2GeneraldescriptionofsynchronizationsystemThisclausegivesageneraldescriptionofthesynchronizationsystem.Detailedrequirementsaregiveninclauses3to7.TheBTSsendssignalsontheBCCHor,forCOMPACTontheCPBCCH,toenabletheMStosynchronizeitselftotheBTSandifnecessarycorrectitsfrequencystandardtobeinlinewiththatoftheBTS.ThesignalssentbytheBTSforthesepurposesare:a)Frequencycorrectionbursts;b)Synchronizationbursts.Thetimingsoftimeslots,TDMAframes,TCHframes,controlchannelframes,and(forCOMPACT)therotationoftimegroupsareallrelatedtoacommonsetofcounterswhichruncontinuouslywhethertheMSandBTSaretransmittingornot.Thus,oncetheMShasdeterminedthecorrectsettingofthesecounters,allitsprocessesaresynchronizedtothecurrentservingBTS.SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)8(GSM05.10version8.3.1Release1999)TheMStimesitstransmissionstotheBTSinlinewiththosereceivedfromtheBTS.TheBTSsendstoeachMSa"timingadvance"parameter(TA)accordingtotheperceivedroundtrippropagationdelayBTS-MS-BTS.TheMSadvancesitstimingbythisamount,withtheresultthatsignalsfromdifferentMS'sarrivingattheBTSandcompensatedforpropagationdelay.Thisprocessiscalled"adaptiveframealignment".Additionally,synchronizationfunctionsmaybeimplementedinboththeMSandtheBTStosupporttheso-calledpseudosynchronizationscheme.ThesupportofthisschemeisoptionalexceptthatMSshallmeasureandreporttheObservedTimingDifference(OTD),whichisamandatoryrequirement.Thedetailedspecificationsofthepseudo-synchronizationschemeareincludedinannexA.InCTS,theCTS-FPsendssignalsontheCTSBCHtoenabletheMStosynchronizeitselftotheCTS-FPandifnecessarycorrectitsfrequencystandardtobeinlinewiththatoftheCTS-FP.ThesignalssentbytheCTS-FPforthesepurposesare:a)Frequencycorrectionbursts;b)Synchronizationbursts.Thetimingsoftimeslots,TDMAframes,CTSBCH,CTSARCH,CTSAGCHandCTSPCHframesareallrelatedtoafirstcommonsetofcounterswhichruncontinuouslywhethertheCTS-MSandCTS-FParetransmittingornot.Thus,oncetheCTS-MShasdeterminedthecorrectsettingofthesefirstcounters,theCTS-MSisabletoattachtothecurrentservingCTS-FP.Inaddition,duringCTS-MSattachment,theCTS-FPsendstotheCTS-MStheremainingcountersforSACCHandTCHframes.Then,allprocessesoftheCTS-MSaresynchronizedtothecurrentservingCTS-FP.TheCTS-MStimesitstransmissionstotheCTS-FPinlinewiththosereceivedfromtheCTS-FP.ThetimingadvanceparameterissettozeroforCTS.Additionally,theCTS-FPmaybeassistedbyaCTS-MStoadjustitsfrequencysource.WhenrequiredbytheCTS-FP,theCTS-MSestimatesifpossibleandreportstheObservedFrequencyOffsetoftheCTS-FPwithaspecifiedBTS.TheCTS-FPmaythenadjustitsfrequencysourceaccordingtothisvalue.3Timebasecounters3.1TimingstateofthesignalsThetimingstateofthesignalstransmittedbyaBTS,aMS,aCTS-FP,oranCompactBTSandMSisdefinedbythefollowingcounters:-QuartersymbolnumberQN(0-624)-SymbolnumberBN(0-156);-TimeslotnumberTN(0-7);-TDMAframenumberFN(0to(26x51x2048)-1=2715647);or-foranonattachedCTS-MS,TDMAframenumbermodulo52T4(0-51);or-forCompact,TDMAframenumberFN(0to(52x51x1024)-1=2715647).InCTS,theCTS-MSshallmanagedifferentsetsofcountersforCTSoperationandGSMoperation.3.2RelationshipbetweencountersTherelationshipbetweenthesecountersisasfollows:-QNincrementsevery12/13µs;-BN=IntegerpartofQN/4;-TNincrementswheneverQNchangesfromcount624to0;-FNincrementswheneverTNchangesfromcount7to0;orSIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)9(GSM05.10version8.3.1Release1999)-foraCTS-MS,T4incrementswheneverTNchangesfromcount7to0.4TimingoftransmittedsignalsThetimingofsignalstransmittedbytheMS,BTSandCTS-FParedefinedinGSM05.02.TheMScanusethetimingofreceiptofthesynchronizationbursttosetupitstimebasecountersasfollows:QNissetbythetimingofthetrainingsequence;TN=0whenthesynchburstisreceived;FN=51((T3-T2)mod(26))+T3+51x26xT1whenthesynchburstisreceived,(whereT3=(10xT3')+1,T1,T2andT3'beingcontainedininformationfieldsinsynchronizationburst).ForCompact,theMScanusethetimingofreceiptofthesynchronizationbursttosetupitstimebasecountersasfollows:QNissetbythetimingofthetrainingsequence;FN=(R1x51+R2)x52+51whenthesynchburstisreceived(whereR1andR2arecontainedininformationfieldsinsynchronizationburst);TNisdeterminedfromTGasdescribedinGSM05.02,whereTGiscontainedininformationfieldsinsynchronizationburst.ForCTS,thetimebasecountersaresetasfollows:QNissetbythetimingofthetrainingsequence;TNissetaccordingtotheCTSBCH-SBposition(seeAnnexC);T4=51whentheCTSBCH-SBisreceived(priortoattachment);FN=(51((T3-T2)mod(26))+T3+51x26xT1)mod(2715648)whentheCTS-MSreceivesthelastCTSAGCHburstofthenon-hoppingaccessprocedure,whereT2=T4mod(26),andT1andT3beingcontainedinthisCTSimmediateassignmentmessage.Thereafter,thetimebasecountersareincrementedasinclause3.2.(WhenadjacentBTS'sarebeingmonitoredforhandoverpurposes,orforcellreselectionpurposesingroupreceivemode,theMSmaychoosetostorethevaluesofQN,TNandFNforalltheBTS'swhosesynchronizationburstshavebeendetectedrelativetoQN,TNandFNforitscurrentservingBTS).5BTSRequirementsforSynchronizationTheconditionsunderwhichtherequirementsofclauses5.4and5.6mustbemetshallbe3dBbelowthereferencesensitivitylevelorinputlevelforreferenceperformance,whicheverapplicable,inGSM05.05and3dBlesscarriertointerferenceratiothanthereferenceinterferenceratiosinGSM05.05.5.1FrequencysourceTheBTSshalluseasinglefrequencysourceofabsoluteaccuracybetterthan0.05ppmforbothRFfrequencygenerationandclockingthetimebase.ThesamesourceshallbeusedforallcarriersoftheBTS.ForthepicoBTSclasstheabsoluteaccuracyrequirementisrelaxedto0.1ppm.NOTE:BTSfrequencysourcestabilityisonefactorrelatingtoE-OTDLCSperformanceandthereaderisreferredtoAnnexCfortherelationshipbetweenBTSfrequencysourcestabilityandE-OTDLCSperformancecharacteristics.SIST EN 300 912 V8.3.1:2003

ETSIETSIEN300912V8.3.1(2000-10)10(GSM05.10version8.3.1Release1999)5.2TimebasecountersItisoptionalwhetherthetimebasecountersofdifferentBTS'saresynchronizedtogether.ForCOMPACTinterbasestationtimesynchronizationisrequiredsuchthattimeslotnumber(TN)=i(i=0to7)andframenumber(FN)withFNmod208=0shalloccuratthesametimeinallcells.ThetimebasecountersofdifferentBTSsshallbesynchronizedtogethersuchthatthetimingdifferencebetweendifferentBTSsshallbelessthan1symbolperiod,48/13µs(whichcanbe1or3bitsdependinguponmodulation)measuredattheBTSantenna.IfacelldefinesaCOMPACTcellinitsneighborlist,timesynchronizationisrequiredsuchthattimeslotnumber(TN)=i(i=0to7)andframenumber(FN)withFNmod208=0shalloccuratthesametimeinbothcells.5.3InternalBTScarriertimingThechannelsofdifferentcarrierstransmittedbyaBTSshallbesynchronizedtogether,i.e.controlledbythesamesetofcounters.Thetimingdifferencebetweenthedifferentcarriersshallbelessthan1/4symbolperiods,measuredattheBTSantenna.Forpico-BTS,thetimingdifferencebetweendifferentcarriersshallbelessthan2symbolperiods,measuredattheBTSantenna.5.4InitialTimingadvanceestimationWhentheBTSdetectsanaccessbursttransmissiononRACHorPRACH,itshallmeasurethedelayofthissignalrelativetotheexpectedsignalfromanMSatzerodistanceunderstaticchannelconditions.Thisdelay,calledthetimingadvance,shallberoundedtothenearestsymbolperiodandincludedinaresponsefromtheBTSwhenapplicable.Forthepico-BTSthereisnorequirementtomeasurethistimingadvance.However,eitherthismeasuredvalueoraprogrammablevalueoftimingadvanceshallbeincludedintheresponsefromtheBTSwhenatimingadvancevalueneedstobesent.5.5MaximumtimingadvancevalueThemaximumtimingadvancevalueTAmaxshallbe63.IftheBTSmeasuresavaluelargerthanthis,itshallsetthetimingadvanceto63.InthecaseofGSM400theextendedtimingadvanceinformationelementissupportedandthemaximumtimingadvancevalueTAmaxshallbe219.IftheBTSmeasuresavaluelargerthanthis,itshallsetthetimingadvanceto219.(GSM03.30defineshowthePLMNdealswithMS'swherethedelayexceedstimingadvancevalue63).5.6Delaytracking5.6.1ForcircuitswitchedchannelsTheBTSshallthereaftercontinuouslymonitorthedelayofthenormalburstssentbyfromtheMS.Ifthedelaychangesbymorethanonesymbolperiod,thetimingadvanceshallbeadvancedorretarded1andthenewvaluesignalledtotheMS.Restrictingthechangeintimingadvanceto1symbolperiodatatimegivesthesimplestimplementationoftheBTS.HowevertheBTSmayusealargerchangethanthisbutgreatcaremustthenbeusedintheBTSdesign.5.6.2ForpacketswitchedchannelsTheBTSshallperformthecontinuousupdatetimingadvancemechanismforallMSworkinginpackettransfermodeforwhichanPTCCHsubchannelisassigned,exceptforMSclassAindedica
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