SIST EN 301 248 V4.1.1:2003
(Main)Digital cellular telecommunications system (Phase 2) (GSM); Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.81 version 4.1.1)
- Abstract
EN created for GSM Phase2 MS type approval purposes (a revision of GSM Phase 2+ ETS)
- 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
- Mandate
- T-172
SIST EN 301 248 V4.1.1:2003 is the Slovenian adoption of ETSI EN 301 248 V4.1.1, a European Standard for GSM Phase 2 discontinuous transmission (DTX) on Enhanced Full Rate (EFR) speech traffic channels. It specifies how GSM Mobile Stations (MS) and Base Station Systems (BSS) handle speech pauses on the transmit and receive sides, including Voice Activity Detection, SID frame handling, comfort noise generation, and frame substitution during errors. It was created for GSM Phase 2 MS type approval purposes, so it is aimed at implementers and test engineers who need DTX behavior to match the GSM air interface and, in some BSS cases, the A-bis interface.
What does SIST EN 301 248 V4.1.1:2003 specify?
SIST EN 301 248 V4.1.1:2003 specifies the general baseband operation of EFR speech traffic channels during DTX in GSM MS and BSS equipment. The document focuses on how frames are classified, passed, repeated, or replaced so that speech pauses do not break call quality.
The structure is simple: Clause 1 gives the scope, Clause 2 lists references, Clause 3 defines terms, symbols, and abbreviations, Clause 4 gives the general DTX model, Clause 5 covers the transmit side, Clause 6 covers the receive side, and Annex A gives change request history.
A key implementation note in the scope is that the exact split of functions between system entities is not mandatory, as long as the air-interface behavior and speech-decoder output stay the same. The exception is a BSS with a remote speech transcoder in the BSC, where the DTX handler to RSS interface and its flags are mandatory as part of A-bis.
What are the key requirements of SIST EN 301 248 V4.1.1:2003?
The standard makes DTX a controlled way to switch off the radio transmitter during speech pauses to save MS power and reduce interference. In practice, the equipment must still keep call quality stable while transmission is reduced.
Transmit side behavior
The TX side uses a Voice Activity Detector (VAD) that runs continuously and drives the TX DTX handler. When VAD indicates speech, the frame is sent directly with SPflag = "1"; when speech ends, the handler uses a 7-frame hangover period before sending the first SID frame. This timing matters because it keeps short pauses from being treated as silence too early.
If fewer than 24 frames have elapsed since the last SID frame, the last SID frame is repeated until a new updated SID frame is ready. The TX radio subsystem then schedules all speech frames, the first SID frame after speech, and SID frames aligned with the SACCH multiframe. This is how the system keeps sending just enough update information for comfort noise while avoiding unnecessary radio use.
Receive side behavior
The RX side classifies each received traffic frame using the Bad Frame Indicator (BFI), SID, and Time Alignment Flag (TAF). Good speech frames go directly to the speech decoder, while lost speech or lost SID frames trigger the substitution and muting procedure from the companion standard on error concealment.
Valid SID frames cause comfort noise generation until the next SID is expected or good speech returns. Invalid SID frames are replaced by the last valid SID frame before the comfort-noise procedure continues. In practice, this keeps background noise from jumping abruptly when the radio link is imperfect.
Interface and conformance points
For BSS implementations with a remote transcoder, the DTX handler and RSS interface, including their flags, are part of the required A-bis behavior. The standard also says the receiver requirements are mandatory for all GSM BSS, while the transmitter requirements apply where downlink DTX is used. That matters for procurement and test planning because not every network element is covered in the same way.
What terms does SIST EN 301 248 V4.1.1:2003 define?
- Bad Frame Indicator (BFI) - A binary flag showing whether a traffic frame is considered meaningful; in this standard, FACCH frames are marked as bad.
- Voice Activity Detector (VAD) - The algorithm that decides, frame by frame, whether speech is present on the transmit side.
- Silence Descriptor (SID) frame - A traffic frame carrying background-noise information for comfort-noise generation.
- SP flag - The transmit-side flag that marks a frame as speech (
1) or SID (0). - Time Alignment Flag (TAF) - A flag showing whether a traffic frame is aligned with the SACCH multiframe and when the next SID frame is expected.
- valid SID frame - A good traffic frame marked
SID="2"by the radio subsystem, usable for updating comfort-noise parameters at any time. - hangover period - The 7-frame period after speech ends during which VAD has gone to zero but speech frames are still sent.
Who uses SIST EN 301 248 V4.1.1:2003?
SIST EN 301 248 V4.1.1:2003 is used by GSM handset designers, base-station engineers, and speech codec implementers who need DTX behavior to match the rest of the GSM speech chain. It is also used by conformance and type-approval teams checking MS behavior, and by BSS integrators working with A-bis interfaces and remote transcoders.
Network and quality teams use it to understand how call quality should behave during pauses, handover, and radio errors. Test labs use it when verifying frame handling, SID processing, and comfort-noise continuity.
What changed in SIST EN 301 248 V4.1.1:2003 from the previous edition?
The foreword says this edition corresponds to GSM technical specification GSM 06.81 version 4.1.0, and Annex A records a change request for a DTX synchronization problem at handover. The published version then updates the document to version 4.1.1.
Which standards are used with SIST EN 301 248 V4.1.1:2003?
- GSM01.04 - Provides abbreviations and acronyms used in the GSM series.
- GSM04.08 - Supplies mobile radio interface Layer 3 context, including network control relevant to DTX operation.
- GSM05.03 - Covers channel coding.
- GSM05.05 - Covers radio transmission and reception and defines the BFI behavior used here.
- GSM05.08 - Covers radio subsystem link control and SACCH multiframe alignment.
- GSM06.51 - Gives the general description of EFR speech processing.
- GSM06.53 - Provides ANSI-C code for the EFR speech codec.
- GSM06.54 - Provides test vectors for the EFR speech codec.
- GSM06.60 - Defines EFR speech transcoding, including internal variables used by DTX functions.
- GSM06.61 - Defines substitution and muting for lost frames.
- GSM06.62 - Defines comfort-noise aspects and the SID codeword.
- GSM06.82 - Defines the VAD algorithm used on the transmit side.
- GSM08.60 - Defines in-band control of remote transcoders and rate adaptors for EFR and full-rate traffic channels.
What does the SIST EN 301 248 V4.1.1:2003 document contain?
The document contains a transmit-side block diagram, a receive-side block diagram, and two timing examples that show normal hangover behavior and short speech-burst handling. It also includes a frame-classification table on the receive side that maps BFI, SID, and TAF combinations to frame types.
The body of the standard describes the TX DTX handler, the TX radio subsystem, the RX radio subsystem, and the RX DTX handler. These sections are used for implementation, conformance testing, and troubleshooting of GSM DTX behavior.
Annex A provides the change request history, so users can trace the update that led to version 4.1.1.
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Frequently Asked Questions
SIST EN 301 248 V4.1.1:2003 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Digital cellular telecommunications system (Phase 2) (GSM); Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.81 version 4.1.1)". This standard covers: EN created for GSM Phase2 MS type approval purposes (a revision of GSM Phase 2+ ETS)
EN created for GSM Phase2 MS type approval purposes (a revision of GSM Phase 2+ ETS)
SIST EN 301 248 V4.1.1:2003 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 301 248 V4.1.1:2003 is associated with the following European legislation: Standardization Mandates: T-172. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
SIST EN 301 248 V4.1.1:2003 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); Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.81 version 4.1.1)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 301 248 Version 4.1.1SIST EN 301 248 V4.1.1:2003en01-december-2003SIST EN 301 248 V4.1.1:2003SLOVENSKI
STANDARD
ETSIEN301248V4.1.1(2000-04)EuropeanStandard(Telecommunicationsseries)Digitalcellulartelecommunicationssystem(Phase2);DiscontinuousTransmission(DTX)forEnhancedFullRate(EFR)speechtrafficchannels(GSM06.81version4.1.1)GLOBALSYSTEMFORMOBILECOMMUNICATIONSRSIST EN 301 248 V4.1.1:2003
ETSIETSIEN301248V4.1.1(2000-04)2(GSM06.81version4.1.1)ReferenceREN/SMG-110681PR1KeywordsDigitalcellulartelecommunicationssystem,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 301 248 V4.1.1:2003
ETSIETSIEN301248V4.1.1(2000-04)3(GSM06.81version4.1.1)ContentsIntellectualPropertyRights.4Foreword.41Scope.52References.53Definitions,symbolsandabbreviations.63.1Definitions.63.2Symbols.73.3Abbreviations.74General.74.1Generalorganization.75Transmit(TX)side.85.1Generaloperation.85.1.1FunctionsoftheTXDTXhandler.85.1.2FunctionsoftheTXRadioSubsystem.106Receive(RX)side.116.1Generaloperation.116.1.1FunctionsoftheRXradiosubsystem.116.1.2FunctionsoftheRXDTXhandler.12AnnexA(informative):ChangeRequestHistory.13History.14SIST EN 301 248 V4.1.1:2003
ETSIETSIEN301248V4.1.1(2000-04)4(GSM06.81version4.1.1)IntellectualPropertyRightsIPRsessentialorpotentiallyessentialtothepresentdocumentmayhavebeendeclaredtoETSI.TheinformationpertainingtotheseessentialIPRs,ifany,ispubliclyavailableforETSImembersandnon-members,andcanbefoundinSR000314:"IntellectualPropertyRights(IPRs);Essential,orpotentiallyEssential,IPRsnotifiedtoETSIinrespectofETSIstandards",whichisavailablefromtheETSISecretariat.LatestupdatesareavailableontheETSIWebserver(http://www.etsi.org/ipr).PursuanttotheETSIIPRPolicy,noinvestigation,includingIPRsearches,hasbeencarriedoutbyETSI.NoguaranteecanbegivenastotheexistenceofotherIPRsnotreferencedinSR000314(ortheupdatesontheETSIWebserver)whichare,ormaybe,ormaybecome,essentialtothepresentdocument.ForewordThisEuropeanStandard(Telecommunicationsseries)hasbeenproducedbytheSpecialMobileGroup(SMG).ThepresentdocumentdescribesthegeneralbasebandoperationofEnhancedFullRatespeechtrafficchannelsinthetransmitterandinthereceiverofGSMMobileStationsandBaseStationSystemsduringDiscontinuousTransmission(DTX)withinthedigitalcellulartelecommunicationssystem.ThepresentdocumentcorrespondstoGSMtechnicalspecification,GSM06.81,version4.1.0.NationaltranspositiondatesDateofadoptionofthisEN:31March2000DateoflatestannouncementofthisEN(doa):30June2000DateoflatestpublicationofnewNationalStandardorendorsementofthisEN(dop/e):31December2000DateofwithdrawalofanyconflictingNationalStandard(dow):31December2000SIST EN 301 248 V4.1.1:2003
ETSIETSIEN301248V4.1.1(2000-04)5(GSM06.81version4.1.1)1ScopeThepresentdocumentgivesadescriptionofthegeneralbasebandoperationofEnhancedFullRatespeechtrafficchannelsinthetransmitterandinthereceiverofGSMMobileStations(MS)sandBaseStationSystems(BSS)sduringDiscontinuousTransmission(DTX).Forclarity,thedescriptionisstructuredaccordingtotheblockdiagramsinfigures1and4.Exceptinthecasedescribednext,thisstructureofdistributingthevariousfunctionsbetweensystementitiesisnotmandatoryforimplementation,aslongastheoperationontheairinterfaceandonthespeechdecoderoutputremainsthesame.InthecaseofBSSswherethespeechtranscoderislocatedremotelyintheBaseStationController(BSC),theimplementationoftheinterfacesbetweentheDTXhandlersandtheRadioSubSystem(RSS)asdescribedinthepresentdocumenttogetherwithalltheirflagsismandatory,beingpartoftheA-bisinterfaceasdescribedinGSM08.60(ETS300737)[13].TheDTXfunctionsdescribedinthepresentdocumentaremandatoryforimplementationintheGSMMSs.ThereceiverrequirementsaremandatoryforimplementationinallGSMBSSs,thetransmitterrequirementsonlyforthosewheredownlinkDTXwillbeused.2ReferencesThefollowingdocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthepresentdocument.• Referencesareeitherspecific(identifiedbydateofpublication,editionnumber,versionnumber,etc.)ornon-specific.• Foraspecificreference,subsequentrevisionsdonotapply.• Foranon-specificreference,thelatestversionapplies.• Anon-specificreferencetoanETSshallalsobetakentorefertolaterversionspublishedasanENwiththesamenumber.[1]GSM01.04(ETR100):"Digitalcellulartelecommunicationssystem(Phase2);Abbreviationsandacronyms".[2]GSM04.08(ETS300557):"Digitalcellulartelecommunicationssystem(Phase2);Mobileradiointerfacelayer3specification".[3]GSM05.03(ETS300575):"Digitalcellulartelecommunicationssystem(Phase2);Channelcoding".[4]GSM05.05(ETS300577):"Digitalcellulartelecommunicationssystem(Phase2);Radiotransmissionandreception".[5]GSM05.08(ETS300578):"Digitalcellulartelecommunicationssystem(Phase2);Radiosubsystemlinkcontrol".[6]GSM06.51(EN301243):"Digitalcellulartelecommunicationssystem;EnhancedFullRate(EFR)speechprocessingfunctions;Generaldescription".[7]GSM06.53(EN301244):"Digitalcellulartelecommunicationssystem;ANSI-CcodefortheGSMEnhancedFullRate(EFR)speechcodec".[8]GSM06.54(EN301250):"Digitalcellulartelecommunicationssystem(Phase2);TestvectorsfortheGSMEnhancedFullRate(EFR)speechcodec".[9]GSM06.60(EN301245):"Digitalcellulartelecommunicationssystem;EnhancedFullRate(EFR)speechtranscoding".SIST EN 301 248 V4.1.1:2003
ETSIETSIEN301248V4.1.1(2000-04)6(GSM06.81version4.1.1)[10]GSM06.61(EN301246):"Digitalcellulartelecommunicationssystem;SubstitutionandmutingoflostframeforEnhancedFullRate(EFR)speechtrafficchannels".[11]GSM06.62(EN301247):"Digitalcellulartelecommunicationssystem;ComfortnoiseaspectsforEnhancedFullRate(EFR)speechtrafficchannels".[12]GSM06.82(EN301249):"Digitalcellulartelecommunicationssystem;VoiceActivityDetector(VAD)forEnhancedFullRate(EFR)speechtrafficchannels".[13]GSM08.60(ETS300737):"Digitalcellulartelecommunicationssystem(Phase2+);InbandcontrolofremotetranscodersandrateadaptorsforEnhancedFullRate(EFR)andfullratetrafficchannels".3Definitions,symbolsandabbreviations3.1DefinitionsForthepurposesofthepresentdocument,thefollowingtermsanddefinitionsapply:acceptedSIDframe:AtrafficframewhichisflaggedwithSID="1"orSID="2"bytheRadioSubsystem.badtrafficframe:AtrafficframeflaggedBFIflag="1"(BadFrameIndication)bytheRadioSubsystem.frame:Timeintervalof20msec.correspondingtothetimesegmentationoftheEnhancedFullRatespeechtranscoder(GSM06.60(EN301245)[9]),alsousedasashorttermforatrafficframe.goodspeechframe:AgoodtrafficframewhichisnotanacceptedSIDframe.goodtrafficframe:AtrafficframeflaggedBFIflag="0"bytheRadioSubsystem.hangoverperiod:Aperiodof7framesaddedattheendofaspeechburstinwhichVADflag="0"andSPflag="1".invalidSIDframe:AnacceptedSIDframewhichwasnotclassifiedasvalidSIDframe.Thisframeisnotvalidforupdatingcomfortnoiseparameters,buttheframeconveysinformationthatcomfortnoisegenerationsshouldbestartedorcontinued.lostSIDframe:AnunusableframereceivedwhentheRXDTXhandlerisgeneratingcomfort
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