SIST EN 300 912 V8.3.1:2003
(Main)Digital cellular telecommunications system (Phase 2+) (GSM); Radio subsystem synchronization (GSM 05.10 version 8.3.1 Release 1999)
- 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
- 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 V8.3.1:2003 is the Slovenian adoption of ETSI EN 300 912 Version 8.3.1 for GSM Phase 2+ Release 1999. It specifies synchronization requirements for the GSM radio subsystem - including BTS, MS, CTS-FP and CTS-MS operation - so designers, test labs and operators can keep frequency and timing aligned in practice.
What does SIST EN 300 912 V8.3.1:2003 specify?
SIST EN 300 912 V8.3.1:2003 specifies synchronization on the GSM radio subsystem and on CTS. It sets requirements for timing, frequency accuracy, timing advance, handover-related synchronization and CTS observed-frequency reporting.
The document does not define the synchronization algorithms to be used in the BTS, CTS-FP or MS. Those implementation details are left to the manufacturer.
The standard is organized into general synchronization concepts, timebase counters, transmitted-signal timing, BTS requirements, MS requirements, CTS-FP requirements, and normative Annex A plus informative Annexes B to D.
| 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 | BTS frequency source stability and E-OTD LMU reporting periods for LCS |
| Annex D | Change control history |
What are the key requirements of SIST EN 300 912 V8.3.1:2003?
The standard builds synchronization around common timebase counters and defines how they relate to one another. Clause 3 uses QN, BN, TN, FN and, for CTS, T4; clause 4 explains how received synchronization bursts are used to initialize those counters. In practice, this is the timing model that keeps all later procedures consistent.
BTS synchronization requirements
Clause 5 requires a BTS to use a single frequency source for RF generation and timebase clocking, with tight absolute accuracy. The BTS also has to keep its carriers aligned and, where required, keep inter-BTS timing close enough that the difference is less than one symbol period at the antenna. For a network, this means oscillator quality and site timing matter directly to uplink and handover behavior.
Clause 5 also requires the BTS to measure the delay of access bursts, round the value to the nearest symbol period, and signal timing advance back to the MS when needed. It must keep tracking delay on circuit-switched and packet-switched channels, with separate handling for packet channels through PTCCH. In practice, the BTS continually corrects the mobile’s uplink timing as propagation changes.
MS synchronization requirements
Clause 6 requires the MS to keep its carrier frequency accurate and to align its internal timebase with the BTS. If the timing difference grows too large, the MS must adjust in small steps rather than making a large jump. The MS then transmits at the BTS-referenced timing advance so that bursts from different users arrive in the correct window.
Clause 6 also separates circuit-switched and packet-switched behavior. For packet transfer mode, the MS uses Timing Advance Index (TAI), PTCCH and the continuous timing advance procedure; for circuit-switched channels it applies new timing advance values from SACCH. This matters because packet and voice/data operation do not use the same timing messages or update points.
The MS also has defined reaction times for access, handover, channel coding changes and other network commands. Those reaction times tell implementers how quickly the terminal must be ready after a control message.
CTS synchronization requirements
Clause 7 sets CTS-FP frequency and timing rules, and it allows the CTS-FP to be assisted by a CTS-MS. When assistance is used, the CTS-MS computes the Observed Frequency Offset (OFO) and reports it so the CTS-FP can correct its source. This is the control loop that keeps CTS behavior aligned over time.
Annex A adds rules for pseudo-synchronization and synchronized handover. It defines how observed time difference, real time difference and timing advance are combined so the target BTS can start with a better timing estimate after handover.
What terms does SIST EN 300 912 V8.3.1:2003 define?
- BTS - Base Transceiver Station, the radio site that communicates with the MS.
- CTS-FP - CTS Fixed Part, the fixed network side of CTS synchronization.
- CTS-MS - MS operating in CTS mode, used in the CTS timing procedures.
- Timing Advance - the value the BTS sends so the MS advances its transmission timing to compensate for propagation delay.
- Observed Time Difference (OTD) - the timing difference between two BTSs as measured by the MS.
- Timing Advance Index (TAI) - the GPRS value that selects the PTCCH subchannel used for access bursts and timing advance derivation.
- Observed Frequency Offset (OFO) - the frequency difference measured by a CTS-MS between a CTS-FP and a specified BTS.
Who uses SIST EN 300 912 V8.3.1:2003?
SIST EN 300 912 V8.3.1:2003 is used by GSM and CTS equipment manufacturers, especially teams designing BTS, MS and CTS-FP implementations. Test laboratories use it to check timing advance behavior, frequency accuracy and handover timing. Network engineers and planners use it when they need synchronization behavior to fit radio planning, packet operation, mobility and location services.
What changed in SIST EN 300 912 V8.3.1:2003 from the previous edition?
SIST EN 300 912 V8.3.1:2003 is Version 8.3.1. The recorded history identifies it as an update for publication following Version 8.3.0.
Which standards are used with SIST EN 300 912 V8.3.1:2003?
- GSM01.04 - provides abbreviations and acronyms used throughout the document.
- GSM03.30 - supplies radio network planning aspects, including the handling of extended timing advance.
- GSM03.52 and GSM05.56 - provide CTS lower-layer and CTS-FP radio subsystem context.
- GSM03.60 and GSM03.64 - provide GPRS service and radio interface stage definitions used in packet timing procedures.
- GSM04.08 and GSM04.60 - define Layer 3 and GPRS MAC/RLC procedures used for assignments, handover and packet control messages.
- GSM05.02 - defines multiplexing and multiple access, and supports the counter and CTSBCH timing model.
- GSM05.05 - provides radio transmission and reception reference levels used for applicability conditions.
- GSM05.08 - provides radio subsystem link control and timing advance reporting context.
What does the SIST EN 300 912 V8.3.1:2003 document contain?
The document contains the counter relationships, timing formulas and signaling procedures that define GSM radio synchronization. It gives the BTS, MS and CTS timing rules for synchronization bursts, access bursts, timing advance updates, temporary loss of signal and handover. Annex A contains the timing relations for pseudo-synchronization and synchronized handover messages.
It also includes an informative annex on CTSBCH shifting, which explains how a CTS-MS derives TN in different shifting cases. Annex C gives the relationship between BTS frequency stability and E-OTD LMU reporting periods, which is used for location services planning.
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Frequently Asked Questions
SIST EN 300 912 V8.3.1:2003 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 8.3.1 Release 1999)". This standard covers: 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
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
SIST EN 300 912 V8.3.1:2003 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 V8.3.1:2003 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 8.3.1 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.:+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 V8.3.1:2003
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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