SIST EN 300 912 V8.2.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Radio subsystem synchronization (GSM 05.10 version 8.2.1 Release 1999)
- Abstract
R99 @ SMG#30, CR SMG#30bis, 31
- Status
- Published
- Publication Date
- 30-Nov-2003
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Dec-2003
- Due Date
- 01-Dec-2003
- Completion Date
- 01-Dec-2003
SIST EN 300 912 V8.2.1:2003 is the Slovenian adoption of ETSI EN 300 912 Version 8.2.1 for GSM radio subsystem synchronization. It specifies how GSM equipment keeps frequency and timing aligned across the Base Transceiver Station (BTS), Mobile Station (MS), and CTS Fixed Part (CTS-FP), so radio transmission, access, and handover can work in a controlled way. The document is written for equipment designers, network engineers, and test teams working on GSM Phase 2+ systems.
What does SIST EN 300 912 V8.2.1:2003 specify?
SIST EN 300 912 V8.2.1:2003 specifies synchronization requirements for the GSM radio subsystem, including BTS, MS, and CTS-FP operation. Clause 1 sets the scope and Clause 2 gives the system overview; Clauses 3 to 7 cover counters, transmission timing, BTS requirements, MS requirements, and CTS-FP requirements. Annex A adds pseudo-synchronization and synchronized handover rules, Annex B explains CTSBCH timeslot shifting for CTS-MS synchronization, and Annex C records change control history.
| Annex | What it covers |
|---|---|
| Annex A | Additional requirements for pseudo-synchronization, synchronized handovers, and pseudo-synchronized handovers |
| Annex B | CTSBCH timeslot shifting properties for CTS-MS synchronization |
| Annex C | Change control history |
What are the key requirements of SIST EN 300 912 V8.2.1:2003?
SIST EN 300 912 V8.2.1:2003 defines how GSM equipment must keep timing and frequency aligned so signals from different devices remain usable together. In practice, this affects transmitter clock accuracy, timing advance handling, handover behavior, and packet access procedures.
BTS synchronization
Clause 5 requires the BTS to use a single frequency source for RF generation and timebase clocking. The source accuracy is better than 0.05 ppm, or 0.1 ppm for pico-BTS, which matters because frequency error affects burst timing and reception quality.
Clause 5 also requires internal BTS carrier timing to be tightly aligned. Different carriers under one BTS must be driven by the same counters, with only small timing differences allowed, so a network does not create avoidable inter-carrier timing errors.
Clause 5.4 to 5.8 cover initial timing advance, maximum timing advance, delay tracking, and timing advance range. The BTS measures access delay, limits timing advance to TAmax, and keeps tracking movement and propagation changes, which is how uplink bursts stay centered in the correct receive window.
MS synchronization
Clause 6 requires the MS to match the BTS carrier frequency and internal timebase. The MS must keep its transmit timing tied to the received BTS timing and apply timing advance values at the specified moments, which helps the network receive bursts from many mobiles without overlap.
Clause 6.5 and 6.6 cover how the MS applies timing advance in circuit switched and packet switched operation, including access to a new BTS and handover cases. This matters because the MS may need to use TA 0 for access bursts, then switch to the received timing advance or a handover-derived value once the network provides it.
Clause 6.7 to 6.11 set reaction times after signal loss, channel change, and packet radio events. These limits tell implementers how quickly the MS must be ready to transmit or receive after network commands, which is important for call continuity and packet scheduling.
CTS and handover support
Clause 7 sets CTS-FP synchronization requirements, including its frequency source accuracy, internal carrier timing, and CTS-MS delay assessment. For CTS, the timing rules are similar to GSM but adapted to CTS operation, and the CTS-FP may also use CTS-MS reported Observed Frequency Offset (OFO) to correct its frequency source.
Annex A adds the pseudo-synchronization scheme and the special handover calculations. This annex matters where a handover uses timing information from both the old and new BTS, so the MS can set an initial timing advance from measured time differences.
What terms does SIST EN 300 912 V8.2.1:2003 define?
- Base Transceiver Station (BTS) - The radio base station that transmits and receives GSM signals and provides timing information to the MS.
- Mobile Station (MS) - The user equipment that synchronizes to the BTS and times its uplink transmissions accordingly.
- CTS Fixed Part (CTS-FP) - The fixed part of GSM Cordless Telephony System operation, which plays the network-side timing role for CTS.
- Timing Advance (TA) - The parameter the BTS sends to shift MS transmission timing to compensate for propagation delay.
- Timing Advance Index (TAI) - The GPRS value that determines which PTCCH subchannel the MS uses for access bursts.
- Observed Frequency Offset (OFO) - The measured frequency difference between signals received by a CTS-MS from a CTS-FP and a BTS.
- Observed Time Difference (OTD) - The timing difference between two BTSs as measured by the MS for pseudo-synchronized handover.
- Timebase counters - The counter set that defines the timing state of transmitted GSM signals.
Who uses SIST EN 300 912 V8.2.1:2003?
SIST EN 300 912 V8.2.1:2003 is used by GSM radio equipment manufacturers, especially teams designing BTS, MS, CTS-FP, and CTS-MS implementations. It is also used by network engineers and planners who need timing advance, handover, and synchronization behavior to fit the radio network design. Test and quality teams use it to verify frequency accuracy, timing alignment, and reaction times in GSM and CTS equipment.
What changed in SIST EN 300 912 V8.2.1:2003 from the previous edition?
SIST EN 300 912 V8.2.1:2003 is the publication update to version 8.2.1 from version 8.2.0. Annex C records changes covering clarification of TAI use, GPRS timing advance updates on PTCCH, correction of GPRS timing advance procedures, CTS synchronization and CTS service range control, reaction times, extended range TA information, GSM400 MS carrier frequency accuracy, 8-PSK modifications, and Compact-related synchronization updates.
Which standards are used with SIST EN 300 912 V8.2.1:2003?
SIST EN 300 912 V8.2.1:2003 references several GSM standards that provide the surrounding procedures and definitions:
- GSM01.04 - abbreviations and acronyms used across the GSM series.
- GSM03.60 and GSM03.64 - GPRS service and radio interface context for packet-mode timing and access.
- GSM04.08 - mobile radio interface Layer 3 signaling, including handover and assignment messages.
- GSM04.60 - GPRS MS-BSS interface procedures for RLC and MAC.
- GSM05.02 - multiplexing, multiple access, timeslot structure, and CTS timing elements.
- GSM05.05 - radio transmission and reception performance references used for sensitivity and interference conditions.
- GSM05.08 - radio subsystem link control, including timing advance and neighbor measurement context.
- GSM03.30 - radio network planning, including handling of larger propagation delay cases.
- GSM03.52 and GSM05.56 - CTS lower layers and CTS-FP radio subsystem behavior.
What does the SIST EN 300 912 V8.2.1:2003 document contain?
SIST EN 300 912 V8.2.1:2003 contains counter definitions, counter relationships, and formulas for initializing timing from synchronization bursts. It also contains step-by-step procedures for BTS and MS timing advance handling in circuit switched and packet switched operation, including GPRS-specific reaction times. Annex A gives the handover timing logic for pseudo-synchronized and synchronized handovers, Annex B explains how CTS-MS derives timeslot number during CTSBCH shifting, and Annex C lists the version history.
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Frequently Asked Questions
SIST EN 300 912 V8.2.1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Digital cellular telecommunications system (Phase 2+) (GSM); Radio subsystem synchronization (GSM 05.10 version 8.2.1 Release 1999)". This standard covers: R99 @ SMG#30, CR SMG#30bis, 31
R99 @ SMG#30, CR SMG#30bis, 31
SIST EN 300 912 V8.2.1:2003 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 300 912 V8.2.1:2003 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); Radio subsystem synchronization (GSM 05.10 version 8.2.1 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 8.2.1SIST EN 300 912 V8.2.1:2003en01-december-2003SIST EN 300 912 V8.2.1:2003SLOVENSKI
STANDARD
ETSIEN300912V8.2.1(2000-09)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2+);Radiosubsystemsynchronization(GSM05.10version8.2.1Release1999)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)2(GSM05.10version8.2.1Release1999)ReferenceREN/SMG-020510Q8KeywordsDigitalcellulartelecommunicationssystem,GlobalSystemforMobilecommunications(GSM)ETSI650RoutedesLuciolesF-06921SophiaAntipolisCedex-FRANCETel.:+33492944200Fax:+33493654716SiretN°34862356200017-NAF742CAssociationàbutnonlucratifenregistréeàlaSous-PréfecturedeGrasse(06)N°7803/88ImportantnoticeIndividualcopiesofthepresentdocumentcanbedownloadedfrom:http://www.etsi.orgThepresentdocumentmaybemadeavailableinmorethanoneelectronicversionorinprint.Inanycaseofexistingorperceiveddifferenceincontentsbetweensuchversions,thereferenceversionisthePortableDocumentFormat(PDF).Incaseofdispute,thereferenceshallbetheprintingonETSIprintersofthePDFversionkeptonaspecificnetworkdrivewithinETSISecretariat.Usersofthepresentdocumentshouldbeawarethatthedocumentmaybesubjecttorevisionorchangeofstatus.InformationonthecurrentstatusofthisandotherETSIdocumentsisavailableathttp://www.etsi.org/tb/status/Ifyoufinderrorsinthepresentdocument,sendyourcommentto:editor@etsi.frCopyrightNotificationNopartmaybereproducedexceptasauthorizedbywrittenpermission.Thecopyrightandtheforegoingrestrictionextendtoreproductioninallmedia.©EuropeanTelecommunicationsStandardsInstitute2000.Allrightsreserved.SIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)3(GSM05.10version8.2.1Release1999)ContentsIntellectualPropertyRights.5Foreword.51Scope.61.1References.61.2Definitionsandabbreviations.72Generaldescriptionofsynchronizationsystem.73Timebasecounters.83.1Timingstateofthesignals.83.2Relationshipbetweencounters.84Timingoftransmittedsignals.95BTSRequirementsforSynchronization.95.1Frequencysource.95.2Timebasecounters.95.3InternalBTScarriertiming.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 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)4(GSM05.10version8.2.1Release1999)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):Changecontrolhistory.21History.22SIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)5(GSM05.10version8.2.1Release1999)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).ThecontentsofthepresentdocumentaresubjecttocontinuingworkwithinSMGandmaychangefollowingformalSMGapproval.ShouldSMGmodifythecontentsofthepresentdocumentitwillthenberepublishedbyETSIwithanidentifyingchangeofreleasedateandanincreaseinversionnumberasfollows:Version8.x.ywhere:8indicatesrelease1999ofGSMPhase2+.xtheseconddigitisincrementedforallchangesofsubstance,i.e.technicalenhancements,corrections,updates,etc.ythethirddigitisincrementedwheneditorialonlychangeshavebeenincorporatedinthespecification.NationaltranspositiondatesDateofadoptionofthepresentdocument:25August2000Dateoflatestannouncementofthepresentdocument(doa):30November2000DateoflatestpublicationofnewNationalStandardorendorsementofthepresentdocument(dop/e):31May2001DateofwithdrawalofanyconflictingNationalStandard(dow):31May2001SIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)6(GSM05.10version8.2.1Release1999)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 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)7(GSM05.10version8.2.1Release1999)1.2DefinitionsandabbreviationsInadditiontothosebelow,abbreviationsusedinthepresentdocumentarelistedinGSM01.04.BTS:BaseTransceiverStationCTS-FP:CTSFixedPartCTS-MS:MSoperatinginCTSmodeTimingAdvance:signalsentbytheBTStotheMSwhichtheMSusestoadvanceitstimingsoftransmissionstotheBTSsoastocompensateforpropagationdelayQuartersymbolnumber:timingofquartersymbolperiods(12/13µs)withinatimeslot.Symbolperiodcanbe1or3bitperiodsdependinguponmodulationTimeslotnumber:timingoftimeslotswithinaTDMAframeTDMAframenumber:countofTDMAframesrelativetoanarbitrarystartpointCurrentServingBTS:BTSononeofwhosechannels(TCH,DCCH,CCCHorPDCH)theMSiscurrentlyoperatingCurrentServingCTS-FP:CTS-FPononeofwhosechannels(TCHorCTScontrolchannels)theCTS-MSiscurrentlyoperatingTimebasecounters:setofcounterswhichdeterminethetimingstateofsignalstransmittedbyaBTSorMSMStimingoffset:delayofthereceivedsignalrelativetotheexpectedsignalfromanMSatzerodistanceunderstaticchannelconditionswithzerotimingadvance.Thisisaccurateto±1symbol,andreportedonceperSACCHorafteraRACHas.required(i.e.atthesamerateastimingadvance).Forexample,foranMSwitharoundtrippropagationdelayofPsymbols,butwithatimingadvanceofTsymbols,thereportedtimingoffsetwillbeP-Tquantizedtothenearestsymbol.ForGPRStheMStimingoffsetisnotreportedTimingAdvanceIndex:TimingAdvanceIndexTAIusedforGPRS,whichdeterminesthepositionofthesubchannelonPTCCH(seeGSM05.02)usedbytheMStosendanaccessburst,fromwhichthenetworkcanderivethetimingadvanceObservedFrequencyOffset(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 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)8(GSM05.10version8.2.1Release1999)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);orforanonattachedCTS-MS,TDMAframenumbermodulo52T4(0-51);orforCompact,TDMAframenumberFN(0to(52x51x1024)-1=2715647).InCTS,theCTS-MSshallmanagedifferentsetsofcountersforCTSoperationandGSMoperation.3.2RelationshipbetweencountersTherelationshipbetweenthesecountersisasfollows:-QNincrementsevery12/13µs;-BN=IntegerpartofQN/4;-TNincrementswheneverQNchangesfromcount624to0;-FNincrementswheneverTNchangesfromcount7to0;orSIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)9(GSM05.10version8.2.1Release1999)-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,thetimebasecountersareincrementedasinsubclause3.2.(WhenadjacentBTS'sarebeingmonitoredforhandoverpurposes,orforcellreselectionpurposesingroupreceivemode,theMSmaychoosetostorethevaluesofQN,TNandFNforalltheBTS'swhosesynchronizationburstshavebeendetectedrelativetoQN,TNandFNforitscurrentservingBTS).5BTSRequirementsforSynchronizationTheconditionsunderwhichtherequirementsofsubclauses5.4and5.6mustbemetshallbe3dBbelowthereferencesensitivitylevelorinputlevelforreferenceperformance,whicheverapplicable,inGSM05.05and3dBlesscarriertointerferenceratiothanthereferenceinterferenceratiosinGSM05.05.5.1FrequencysourceTheBTSshalluseasinglefrequencysourceofabsoluteaccuracybetterthan0,05ppmforbothRFfrequencygenerationandclockingthetimebase.ThesamesourceshallbeusedforallcarriersoftheBTS.ForthepicoBTSclasstheabsoluteaccuracyrequirementisrelaxedto0,1ppm.5.2TimebasecountersItisoptionalwhetherthetimebasecountersofdifferentBTS'saresynchronizedtogether.SIST EN 300 912 V8.2.1:2003
ETSIETSIEN300912V8.2.1(2000-09)10(GSM05.10version8.2.1Release1999)ForCOMPACTinterbasestationtimesynchronizationisrequiredsuchthattimeslotnumber(TN)=i(i=0to7)andframenumber(FN)withFNmod208=0shalloccuratthesametimeinallcells.ThetimebasecountersofdifferentBTSsshallbesynchronizedtogethersuchthatthetimingdifferencebetweendifferentBTSsshallbelessthan1symbolperiod,48/13µs(whichcanbe1or3bitsdependinguponmodulation)measuredattheBTSantenna.5.3InternalBTScarriertimingThechannelsofdifferentcarrierstransmittedbyaBTSshallbesynchronizedtogether,i.e.controlledbythesamesetofcounters.Thetimingdifferencebetweenthedifferentcarriersshallbelessthan1/4symbolperiods,measuredattheBTSantenna.Forpico-BTS,thetimingdifferencebetweendifferentcarriersshallbelessthan2symbolperiods,measuredattheBTSantenna.5.4InitialTimingadvanceestimationWhentheBTSdetectsanaccessbursttransmissiononRACHorPRACH,itshallmeasurethedelayofthissignalrelativetotheexpectedsignalfromanMSatzerodistanceunderstaticchannelconditions.Thisdelay,calledthetimingadvance,shallberoundedtothenearestsymbolperiodandincludedinaresponsefromtheBTSwhenapplicable.Forthepico-BTSthereisnorequirementtomeasurethistimingadvance.However,eitherthismeasuredvalueoraprogrammablevalueoftimingadvanceshallbeincludedintheresponsefromtheBTSwhenatimingadvancevalueneedstobesent.5.5MaximumtimingadvancevalueThemaximumtimingadvanc
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