ETSI TS 146 061-2017 Digital cellular telecommunications system (Phase 2+) (GSM) Substitution and muting of lost frames for Enhanced Full Rate (EFR) speech traffic channels (V14 0 .pdf

1、 ETSI TS 146 061 V14.0.0 (2017-04) Digital cellular telecommunications system (Phase 2+) (GSM); Substitution and muting of lost frames for Enhanced Full Rate (EFR) speech traffic channels (3GPP TS 46.061 version 14.0.0 Release 14) TECHNICAL SPECIFICATION GLOBAL SYSTEM FOR MOBILE COMMUNICATIONSRETSI

2、ETSI TS 146 061 V14.0.0 (2017-04)13GPP TS 46.061 version 14.0.0 Release 14Reference RTS/TSGS-0446061ve00 Keywords GSM ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif

3、enregistre la Sous-Prfecture de Grasse (06) N 7803/88 Important notice The present document can be downloaded from: http:/www.etsi.org/standards-search The present document may be made available in electronic versions and/or in print. The content of any electronic and/or print versions of the presen

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6、 present document, please send your comment to one of the following services: https:/portal.etsi.org/People/CommiteeSupportStaff.aspx Copyright Notification No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm except as aut

7、horized by written permission of ETSI. The content of the PDF version shall not be modified without the written authorization of ETSI. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2017. All rights reserved. DECTTM, P

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9、ation. ETSI ETSI TS 146 061 V14.0.0 (2017-04)23GPP TS 46.061 version 14.0.0 Release 14Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETS

10、I members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (https:/ip

11、r.etsi.org/). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential

12、to the present document. Foreword This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP). The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or GSM identities. These should be interpreted a

13、s being references to the corresponding ETSI deliverables. The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under http:/webapp.etsi.org/key/queryform.asp. Modal verbs terminology In the present document “shall“, “shall not“, “should“, “should not“, “may“, “need not“, “wil

14、l“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. ETSI ETSI TS 146 061 V14.0.0 (2017-04)33GPP

15、TS 46.061 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Definitions and abbreviations . 5g33.1 Definitions 5g33.2 Abbreviations . 5g34 General . 6g35 Requirements 6g35.1 Error detection 6g35.2 Los

16、t speech frames . 6g35.3 First lost SID frame 6g35.4 Subsequent lost SID frames 6g36 Example solution 6g36.1 Example solution for substitution and muting of lost speech frames . 7g36.2 Example solution for substitution and muting of lost SID frames 9g3Annex A (informative): Change history . 10g3Hist

17、ory 11g3ETSI ETSI TS 146 061 V14.0.0 (2017-04)43GPP TS 46.061 version 14.0.0 Release 14Foreword This Technical Specification has been produced by the 3rdGeneration Partnership Project (3GPP). The present document defines a frame substitution and muting procedure which is used by the Receive (RX) Dis

18、continuous Transmission (DTX) handler when one or more lost speech or Silence Descriptor (SID) frames are received from the Radio Sub System (RSS) within the digital cellular telecommunications system. The contents of the present document are subject to continuing work within the TSG and may change

19、following formal TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an identifying change of release date and an increase in version number as follows: Version x.y.z where: x the first digit: 1 presented to TSG for information; 2 presente

20、d to TSG for approval; 3 or greater indicates TSG approved document under change control. y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the

21、 document. ETSI ETSI TS 146 061 V14.0.0 (2017-04)53GPP TS 46.061 version 14.0.0 Release 141 Scope The present document defines a frame substitution and muting procedure which shall be used by the Receive (RX) Discontinuous Transmission (DTX) handler when one or more lost speech or Silence Descriptor

22、 (SID) frames are received from the Radio Sub System (RSS). The requirements of the present document are mandatory for implementation in all GSM Base Station Systems (BSS)s and Mobile Stations (MS)s capable of supporting the enhanced Full Rate speech traffic channel. It is not mandatory to follow th

23、e bit exact implementation outlined in the present document and the corresponding C-source code. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the present document. References are either specific (identified by date of publica

24、tion, edition number, version number, etc.) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to

25、the latest version of that document in the same Release as the present document. 1 GSM 05.03: “Digital cellular telecommunications system (Phase 2+); Channel coding“. 2 GSM 06.60: “Digital cellular telecommunications system (Phase 2+); Enhanced Full Rate (EFR) speech transcoding“. 3 GSM 06.81: “Digi

26、tal cellular telecommunications system (Phase 2+); Discontinuous transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels“. 4 GSM 08.60: “Digital cellular telecommunications system (Phase 2+); Inband control of remote transcoders and rate adaptors for Enhanced Full Rate (EFR) and full

27、 rate traffic channels“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following term and definition applies: 5-point median operation: consists of sorting the 5 elements belonging to the set for which the median operation is to be performed in an asce

28、nding order according to their values, and selecting the third largest value of the sorted set as the median value. Further definitions of terms used in the present document can be found in GSM 06.60 2, GSM 06.81 3, GSM 05.03 1 and GSM 08.60 4. 3.2 Abbreviations For the purposes of the present docum

29、ent, the following abbreviations apply: BFI Bad Frame Indication from Radio Sub System BSI_Abis Bad Sub-block Indication obtained from A-bis CRC checks CCU Channel Coding Unit CRC Cyclic Redundancy Check DTX Discontinuous transmission ETSI ETSI TS 146 061 V14.0.0 (2017-04)63GPP TS 46.061 version 14.

30、0.0 Release 14median5 5-point median operation PrevBFI Bad Frame Indication of Previous frame RSS Radio Sub System RX Receive SID SIlence Descriptor frame TRAU Transcoding Rate Adaptation Unit 4 General The purpose of frame substitution is to conceal the effect of lost frames. The purpose of muting

31、the output in the case of several lost frames is to indicate the breakdown of the channel to the user and to avoid generating possible annoying sounds as a result from frame substitution procedure. The RSS indicates lost speech or SID frames by setting its Bad Frame Indication flag (BFI) based on it

32、s 3-bit and 8-bit CRCs and possibly other error detection mechanisms. The TRAU calculates from the CRCs inserted by the CCU in the TRAU frames one BSI_Abis flag for every sub-block of speech parameters. If either one or more of these flags is set, the speech decoder shall either perform frame substi

33、tution or subframe substitution. The example solution provided in clause 6 applies only for bad frame handling on a complete speech frame basis. However some parts could be modified for substitution of bad sub-blocks. 5 Requirements 5.1 Error detection An error is detected and the BFI-flag is set-by

34、 the RSS according to the principle described in clause 4. 5.2 Lost speech frames Normal decoding of lost speech frames would result in very unpleasant noise effects. In order to improve the subjective quality, lost speech frames shall be substituted with either a repetition or an extrapolation of t

35、he previous good speech frame(s). This substitution is done so that it will gradually decrease the output level, resulting in silencing of the output. Clause 6.1 gives an example solution. 5.3 First lost SID frame A single lost SID frame shall be substituted by the last valid SID frame and the proce

36、dure for valid SID frames be applied as described in GSM 06.81 3. 5.4 Subsequent lost SID frames For the second lost SID frame, a muting technique shall be used on the comfort noise that will gradually decrease the output level (-3 dB/frame), resulting in silencing of the output of the decoder. For

37、subsequent lost SID frames, the muting of the output shall be maintained. Clause 6.2 gives an example solution. 6 Example solution The C-code of the following example is embedded in the bit exact software of the enhanced full rate codec. ETSI ETSI TS 146 061 V14.0.0 (2017-04)73GPP TS 46.061 version

38、14.0.0 Release 146.1 Example solution for substitution and muting of lost speech frames This example solution for substitution and muting is based on a state machine with seven states (figure 1). The system starts in state 0. Each time a bad frame is detected, the state counter is incremented by one

39、 and is saturated when it reaches 6. Each time a good speech frame is detected, the state counter is reset to zero, except when we are in state 6, where we set the state counter to 5. The state indicates the quality of the channel: the bigger the state counter, the worse the channel quality is. The

40、control flow of the state machine can be described with the following C-code (BFI = bad frame indicator, State = state variable): if(BFI != 0 ) State = State + 1; else if(State = 6) State = 5; else State = 0; if(State 6 ) State = 6; In addition to this state machine, the Bad Frame Flag from the prev

41、ious frame is checked (PrevBFI). The processing depends on the value of the State-variable. In states 0 and 5, the processing depends also on the two flags BFI and PrevBFI. ETSI ETSI TS 146 061 V14.0.0 (2017-04)83GPP TS 46.061 version 14.0.0 Release 14The procedure can be described as follows: STATE

42、 = 0BFI = 0PrevBFI = 0 or 1STATE = 1BFI = 1PrevBFI = 0STATE = 2BFI = 1PrevBFI = 1STATE = 3BFI = 1PrevBFI = 1STATE = 5BFI = 0 or 1PrevBFI = 1STATE = 6BFI = 1PrevBFI = 0 or 1Good frame (BFI=0) Bad frame (BFI=1) STATE = 4BFI = 1PrevBFI = 1Figure 1: State machine for controlling the bad frame substituti

43、on BFI = 0, PrevBFI = 0, State = 0 No error is detected in the received or in the previous received speech frame. The received speech parameters are used normally in the speech synthesis. The current frame of speech parameters is saved. BFI = 0, PrevBFI = 1, State = 0 or 5 No error is detected in th

44、e received speech frame but the previous received speech frame was bad. The LTP-gain and fixed codebook gain are limited below the values used for the last received good subframe: ()() ()gggggggppppppp=,111(1) where gp= current decoded LTP-gain, ()gp1 = LTP-gain used for the last good subframe (BFI

45、= 0), and ()() ()gggggggccccccc=,111(2) ETSI ETSI TS 146 061 V14.0.0 (2017-04)93GPP TS 46.061 version 14.0.0 Release 14where gc= current decoded fixed codebook-gain and ()gc1 = fixed codebook gain used for the last good subframe (BFI = 0). The rest of the received speech parameters are used normally

46、 in the speech synthesis. The current frame of speech parameters is saved. BFI = 1, PrevBFI = 0 or 1, State = 1.6 An error is detected in the received speech frame and the substitution and muting procedure is started. The LTP-gain and fixed codebook gain are replaced by attenuated values from the pr

47、evious subframes: gP state g g median g gP state median g g g median g gppppppp p pp= ( ) (), () (), ()( ) ( ( ),., ( ), ( ) ( ( ),., ( )1151551 5 1 51 5(3) where gp= current decoded LTP-gain, ggnpp( ),., ( )1 = LTP-gains used for the last n subframes, median5() = 5-point median operation, P(state)

48、= attenuation factor (P(1) = 0.98, P(2) = 0.98, P(3) = 0.8, P(4) = 0.3, P(5) = 0.2, P(6) = 0.2), state = state number, and gC state g g median g gC state median g g g median g gcccccccc cc= ( ) (), () (),()( ) ( ( ), ., ( ), ( ) ( ( ), ., ( )1151551 5 1 51 5(4) where gc= current decoded fixed codebo

49、ok gain, ggncc( ),., ( )1 = fixed codebook gains used for the last n subframes, median5() = 5-point median operation, C(state) = attenuation factor (C(1) = 0.98, C(2) = 0.98, C(3) = 0.98, C(4) = 0.98, C(5) = 0.98, C(6) = 0.7), and state = state number. The higher the state value is, the more the gains are attenuated. Also the memory of the predictive fixed codebook gain is updated by using the average value of the past four values in the memory: () ()ener ener ii01414=(5)The past