SIST EN 301 246 V4.0.1:2003

• Abstract:

  EN created for GSM Phase2 MS type approval purposes (a revision of GSM Phase 2+ ETS)

• 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
• Mandate: T-172
• Ref Project: ETSI EN 301 246 V4.0.1 (1997-12) - Digital cellular telecommunications system (Phase 2) (GSM); Substitution and muting of lost frames for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.61 version 4.0.1)

SIST EN 301 246 V4.0.1:2003 is the Slovenian adoption of ETSI EN 301 246 V4.0.1 for GSM Enhanced Full Rate (EFR) speech traffic channels. It specifies how a Receive (RX) Discontinuous Transmission (DTX) handler replaces or mutes lost speech and Silence Descriptor (SID) frames so that GSM equipment can conceal frame loss and then fade the output when losses continue. The document was created for GSM Phase 2 mobile-station type approval purposes and applies to GSM Base Station Systems (BSS) and Mobile Stations (MS) that support EFR speech traffic channels.

What does SIST EN 301 246 V4.0.1:2003 specify?

SIST EN 301 246 V4.0.1:2003 defines the frame substitution and muting procedure used when one or more speech or SID frames are lost from the Radio Sub System (RSS). It also says that the procedure is mandatory for implementation in GSM BSSs and MSs capable of supporting the enhanced Full Rate speech traffic channel.

The document is organized into scope, normative references, definitions and abbreviations, general principles, requirements, an example solution, and history. Clause 6 gives example C-code and a state machine that illustrate one way to implement the required behavior, but the standard says the bit-exact implementation itself is not mandatory.

What are the key requirements of SIST EN 301 246 V4.0.1:2003?

• Clause 4 states the purpose of the procedure: conceal lost frames and mute the output if several frames are lost. In practice, this means the receiver should avoid harsh noise and should show the user that the channel is failing by gradually reducing audio output.

• Clause 5.1 ties error detection to the Bad Frame Indication (BFI) flag. The RSS sets BFI using CRCs and other error checks, and the Transcoding Rate Adaptation Unit (TRAU) also derives a Bad Sub-block Indication obtained from A-bis CRC checks, called BSI_Abis. If one or more relevant flags are set, the speech decoder must perform substitution handling.

• Clause 5.2 requires lost speech frames to be replaced by repetition or extrapolation of previous good speech frames. The output level then has to fall gradually toward silence, which limits the audible effect of burst errors.

• Clause 5.3 requires a single lost SID frame to be replaced by the last valid SID frame, and then the valid-SID procedure from GSM 06.81 is applied. This preserves comfort noise behavior instead of dropping immediately into unnatural silence.

• Clause 5.4 requires muting when SID losses continue. The second lost SID frame starts a muting technique on the comfort noise, and later lost SID frames keep the output muted. For implementation, this means the decoder must keep tracking how long the SID loss lasts.

• Clause 6.1 gives an example state machine for lost speech frames. It uses BFI and PrevBFI to select among seven states, with stronger attenuation as the state rises. The example also limits gains, updates memory values, and reuses past parameters so that the decoder output decays smoothly instead of producing clicks or bursts.

• Clause 6.2 gives an example for lost SID frames. The last valid SID frame is repeated, while the fixed codebook gain is reduced by a constant amount each frame until the minimum is reached. In practice, this is the comfort-noise fade-out method that implementers can follow or adapt.

What terms does SIST EN 301 246 V4.0.1:2003 define?

• Bad Frame Indication (BFI) - the flag that shows the RSS has detected a bad received frame.
• Silence Descriptor (SID) frame - a frame used to carry comfort-noise related information during DTX.
• Discontinuous transmission (DTX) - the transmission mode in which speech activity is reduced and the receiver must handle missing frames.
• Receive (RX) - the receive side of the speech path, where frame loss handling takes place.
• Radio Sub System (RSS) - the part that reports received-frame quality and bad-frame status.
• Transcoding Rate Adaptation Unit (TRAU) - the unit that derives BSI_Abis from A-bis CRC checks.
• 5-point median operation - sorting five values and selecting the middle one as the median.

Who uses SIST EN 301 246 V4.0.1:2003?

SIST EN 301 246 V4.0.1:2003 is used by GSM equipment designers, especially engineers working on BSS and MS speech codecs, DTX handlers, and receive-side error concealment. It also matters for type-approval and conformance testing, because the foreword says it was produced for GSM Phase 2 MS type approval purposes. Buyers and quality teams use it to check whether an EFR-capable GSM product follows the required lost-frame behavior.

What changed in SIST EN 301 246 V4.0.1:2003 from the previous edition?

SIST EN 301 246 V4.0.1:2003 corresponds to GSM technical specification GSM 06.61 version 4.0.0. The history section records V4.0.0 as the one-step approval version and V4.0.1 as the publication version.

Which standards are used with SIST EN 301 246 V4.0.1:2003?

• GSM 05.03 (ETS 300 575) - provides channel coding.
• GSM 06.60 (EN 301 245) - provides Enhanced Full Rate (EFR) speech transcoding.
• GSM 06.81 (EN 301 248) - provides discontinuous transmission (DTX) for EFR speech traffic channels.
• GSM 08.60 (ETS 300 737) - provides in-band control of remote transcoders and rate adaptors for EFR and full rate traffic channels.

What does the SIST EN 301 246 V4.0.1:2003 document contain?

The document contains the requirement text for bad-frame handling, plus an example implementation that includes a seven-state control machine, a figure for the state flow, and C-code style logic. It also includes formulas and processing rules for gain attenuation, LSF handling, LTP lag handling, and reuse of excitation pulses. For SID loss, it provides an example of repeated SID handling with stepwise muting.

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2) (GSM); Substitution and muting of lost frames for Enhanced Full Rate (EFR) speech traffic channels (GSM 06.61 version 4.0.1)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 301 246 Version 4.0.1SIST EN 301 246 V4.0.1:2003en01-december-2003SIST EN 301 246 V4.0.1:2003SLOVENSKI
STANDARD
European Telecommunications Standards InstituteEN 301 246 V4.0.1 (1997-12)European Standard (Telecommunications series)Digital cellular telecommunications system (Phase 2);Substitution and muting of lost frames for EnhancedFull Rate (EFR) speech traffic channels(GSM 06.61 version 4.0.1)GLOBAL SYSTEM
FOR MOBILE COMMUNICATIONSRSIST EN 301 246 V4.0.1:2003

EN 301 246 V4.0.1 (1997-12)2GSM 06.61 version 4.0.1ReferenceDEN/SMG-110661P (bjc0200o.PDF)KeywordsDigital cellular telecommunications system,Global System for Mobile communications (GSM)ETSI SecretariatPostal addressF-06921 Sophia Antipolis Cedex - FRANCEOffice address650 Route des Lucioles - Sophia AntipolisValbonne - FRANCETel.: [phone]
Fax: [phone]Siret N° 348 623 562 00017 - NAF 742 CAssociation à but non lucratif enregistrée à laSous-Préfecture de Grasse (06) N° 7803/88X.400c= fr; a=atlas; p=etsi; s=[e-mail]://www.etsi.frCopyright NotificationNo part may be reproduced except as authorized by written permission.The copyright and the foregoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1997.All rights reserved.SIST EN 301 246 V4.0.1:2003

EN 301 246 V4.0.1 (1997-12)3GSM 06.61 version 4.0.1ContentsIntellectual Property Rights.4Foreword.41Scope.52Normative references.53Definitions and abbreviations.53.1Definitions.53.2Abbreviations.54General.65Requirements.65.1Error detection.65.2Lost speech frames.65.3First lost SID frame.65.4Subsequent lost SID frames.66Example solution.66.1Example solution for substitution and muting of lost speech frames.66.2Example solution for substitution and muting of lost SID frames.9History.10SIST EN 301 246 V4.0.1:2003

EN 301 246 V4.0.1 (1997-12)4GSM 06.61 version 4.0.1Intellectual Property RightsIPRs essential or potentially essential to the present document may have been declared to ETSI. The informationpertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be foundin ETR 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect ofETSI standards", which is available free of charge from the ETSI Secretariat. Latest updates are available on the ETSIWeb server (http://www.etsi.fr/ipr).Pursuant to the ETSI Interim IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. Noguarantee can be given as to the existence of other IPRs not referenced in ETR 314 (or the updates onhttp://www.etsi.fr/ipr) which are, or may be, or may become, essential to the present document.ForewordThis European Standard (Telecommunications series) has been produced by the Special Mobile Group (SMG)Technical Committee of the European Telecommunications Standards Institute (ETSI.This EN defines a frame substitution and muting procedure which is used by the Receive (RX) DiscontinuousTransmission (DTX) handler when one or more lost speech or Silence Descriptor (SID) frames are received from theRadio Sub System (RSS) within the digital cellular telecommunications system.This EN corresponds to GSM technical specification, GSM 06.61, version 4.0.0.National transposition datesDate of adoption of this EN:19 December 1997Date of latest announcement of this EN (doa):31 March 1998Date of latest publication of new National Standardor endorsement of this EN (dop/e):30 September 1998Date of withdrawal of any conflicting National Standard (dow):30 September 1998SIST EN 301 246 V4.0.1:2003

EN 301 246 V4.0.1 (1997-12)5GSM 06.61 version 4.0.11ScopeThis EN defines a frame substitution and muting procedure which shall be used by the Receive (RX) DiscontinuousTransmission (DTX) handler when one or more lost speech or Silence Descriptor (SID) frames are received from theRadio Sub System (RSS).The requirements of this EN are mandatory for implementation in all GSM Base Station Systems (BSS)s and MobileStations (MS)s capable of supporting the enhanced Full Rate speech traffic channel. It is not mandatory to follow the bitexact implementation outlined in this EN and the corresponding C-source code.2Normative referencesThis EN incorporates by dated and undated reference, provisions from other publications. These normative referencesare cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequentamendments to or revisions of any of these publications apply to this EN only when incorporated in it by amendment orrevision. For undated references, the latest edition of the publication referred to applies.[1]GSM 05.03 (ETS 300 575): "Digital cellular telecommunications system (Phase 2); Channelcoding".[2]GSM 06.60 (EN 301 245): "Digital cellular telecommunications system; Enhanced Full Rate(EFR) speech transcoding".[3]GSM 06.81 (EN 301 248): "Digital cellular telecommunications system; Discontinuoustransmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels".[4]GSM 08.60 (ETS 300 737): "Digital cellular telecommunications system (Phase 2+); Inbandcontrol of remote transcoders and rate adaptors for Enhanced Full Rate (EFR) and full rate trafficchannels".3Definitions and abbreviations3.1Defi
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