1、 ETSI TS 146 021 V14.0.0 (2017-04) Digital cellular telecommunications system (Phase 2+) (GSM); Half rate speech; Substitution and muting of lost frames for half rate speech traffic channels (3GPP TS 46.021 version 14.0.0 Release 14) TECHNICAL SPECIFICATION GLOBAL SYSTEM FOR MOBILE COMMUNICATIONSRET
2、SI ETSI TS 146 021 V14.0.0 (2017-04)13GPP TS 46.021 version 14.0.0 Release 14Reference RTS/TSGS-0446021ve00 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 lucrat
3、if 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 pre
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9、ociation. ETSI ETSI TS 146 021 V14.0.0 (2017-04)23GPP TS 46.021 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
10、ETSI 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:
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12、al 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 interprete
13、d as 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“, “
14、will“, “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 146 021 V14.0.0 (2017-04)33G
15、PP TS 46.021 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 and con
16、cealment in case of unreliable speech or SID frames 6g35.1.1 Error detection 6g35.1.2 Output signal concealment 6g35.2 Frame substitution and muting in case of lost speech or SID frames . 6g35.2.1 First and second lost speech frame . 6g35.2.2 Subsequent lost speech frames 7g35.2.3 First and second l
17、ost SID frame 7g35.2.4 Subsequent lost SID frames 7g36 Example solutions 7g36.1 Example solution for error detection in case of unreliable frames . 7g36.2 Example solution for output signal concealment in case of unreliable frames . 7g36.3 Example solution for substitution and muting of lost speech
18、frames . 7g36.4 Example solution for substitution and muting of lost SID frames 8g3Annex A (informative): Change history . 9g3History 10g3ETSI ETSI TS 146 021 V14.0.0 (2017-04)43GPP TS 46.021 version 14.0.0 Release 14Foreword This Technical Specification has been produced by the 3rdGeneration Partne
19、rship Project (3GPP). The present document defines a frame substitution and muting procedure which shall be used by the Receive (RX) Discontinuous Transmission (DTX) handler for the half rate speech traffic channels within the digital cellular telecommunications system. The present document is part
20、of a series covering the half rate speech traffic channels as described below: GSM 06.02 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Half rate speech processing functions“. GSM 06.20 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Half rate spe
21、ech transcoding“. GSM 06.21 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Substitution and muting of lost frames for half rate speech traffic channels“. GSM 06.22 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Comfort noise aspects for half rate
22、 speech traffic channels“. GSM 06.41 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Discontinuous Transmission (DTX) for half rate speech traffic channels“. GSM 06.42 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Voice Activity Detector (VAD) fo
23、r half rate speech traffic channels“. GSM 06.06 “Digital cellular telecommunications system (Phase 2+); Half rate speech; ANSI-C code for the GSM half rate speech codec“. GSM 06.07 “Digital cellular telecommunications system (Phase 2+); Half rate speech; Test sequences for the GSM half rate speech c
24、odec“. The contents of the present document are subject to continuing work within the TSG and may change 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
25、number as follows: Version x.y.z where: x the first digit: 1 presented to TSG for information; 2 presented 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,
26、 updates, etc. z the third digit is incremented when editorial only changes have been incorporated in the document. ETSI ETSI TS 146 021 V14.0.0 (2017-04)53GPP TS 46.021 version 14.0.0 Release 141 Scope The present document defines a frame substitution and muting procedure which shall be used by the
27、 Receive (RX) Discontinuous Transmission (DTX) handler when one or more lost or unreliable speech or SIlence Descriptor (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 Mobi
28、le Stations (MS)s capable of supporting the half rate speech traffic channel. 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 publication, edition numbe
29、r, 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 the latest version
30、of that document in the same Release as the present document. 1 GSM 01.04: “Digital cellular telecommunication system (Phase 2+); Abbreviations and acronyms“. 2 GSM 05.03: “Digital cellular telecommunications system (Phase 2+); Channel coding“. 3 GSM 06.20: “Digital cellular telecommunications syste
31、m (Phase 2+); Half rate speech; Half rate speech transcoding“. 4 GSM 06.41: “Digital cellular telecommunications system (Phase 2+); Half rate speech; Discontinuous Transmission (DTX) for half rate speech traffic channels“. 5 GSM 06.06: “Digital cellular telecommunications system (Phase 2+); Half rat
32、e speech; ANSI-C code for the GSM half rate speech codec“. 3 Definitions and abbreviations 3.1 Definitions The definitions of terms used in the present document can be found in GSM 06.20 3, GSM 06.41 4, GSM 05.03 2. 3.2 Abbreviations For the purposes of the present document, the following abbreviati
33、ons apply: BFI Bad Frame Indication BSS Base Station System DTX Discontinuous Transmission GSM Global System for Mobile communications LPC Linear Predictive Coding MS Mobile Station RSS Radio Sub System RX Receive SID SIlence Descriptor UFI Unreliable Frame Indication ETSI ETSI TS 146 021 V14.0.0 (2
34、017-04)63GPP TS 46.021 version 14.0.0 Release 14For abbreviations not given in this clause, see GSM 01.04 1. 4 General The RSS indicates lost speech or SID frames by setting the Bad Frame Indication (BFI) flag and unreliably decoded speech or SID frames by setting the Unreliable Frame Indication (UF
35、I) flag. If the BFI flag is set, the speech decoder performs frame substitution and muting of the speech output. The purpose of frame substitution is to conceal the effect of lost frames. The purpose of muting the speech output in case of several lost frames is to indicate the breakdown of the chann
36、el to the Mobile Station (MS) user in a way that avoids excessively unpleasant sounds. If the UFI flag is set, the speech decoder performs a plausibility analysis of the received frame parameters and of the output signal aiming at the detection and concealment of erroneous frames which are not marke
37、d with the BFI flag. 5 Requirements 5.1 Error detection and concealment in case of unreliable speech or SID frames A cleared BFI flag (BFI= “0“) and a set UFI flag (UFI=“1“) indicate a probably erroneous speech or SID frame. To improve the subjective quality, the probability of decoding erroneous fr
38、ames shall be decreased by additional error detection which is based on both the exploitation of the frame parameters properties and the decoder output signals properties. 5.1.1 Error detection By investigating the frame parameter properties, it shall be decided whether the frame is to be considered
39、 as usable or unusable. In the latter case, the BFI flag is set and substitution and muting is performed (clause 5.2). Clause 6.1 gives an example solution for error detection in case of unreliable frames. 5.1.2 Output signal concealment If the frame is considered as usable, properties of the decode
40、r output signal shall be compared to the corresponding signal properties of the previous valid frames. In case of large differences, the output signal shall be modified such that these differences are limited. Clause 6.2 gives an example solution for output signal concealment in case of unreliable f
41、rames. 5.2 Frame substitution and muting in case of lost speech or SID frames A set BFI flag (BFI=“1“) indicates a lost speech or SID frame. Normal decoding of these frames would result in a degradation of the subjective quality of the speech. To improve the subjective quality of the speech, the fra
42、me parameters shall be appropriately modified prior to the execution of the speech decoder functions. 5.2.1 First and second lost speech frame The first and second lost speech frame shall be partly or completely substituted with the last valid speech frame. For the first and second lost speech frame
43、, the output shall not be muted directly. ETSI ETSI TS 146 021 V14.0.0 (2017-04)73GPP TS 46.021 version 14.0.0 Release 145.2.2 Subsequent lost speech frames For subsequent lost speech frames, a muting technique shall be used that will gradually decrease the output level, resulting in silencing of th
44、e output after a maximum of 80 ms. For subsequent lost speech frames, the muting of the output shall be maintained. Clause 6.3 gives an example of such a method. 5.2.3 First and second lost SID frame The first and second lost SID frame shall be substituted with the last good SID frame. For the first
45、 and second lost SID frame, the output shall not be muted directly. 5.2.4 Subsequent lost SID frames For subsequent lost SID frames, a muting technique shall be used that will gradually decrease the output level, resulting in silencing of the output after a maximum of 320 ms. For subsequent lost SID
46、 frames, the muting of the output shall be maintained. Clause 6.4 gives an example of such a method. 6 Example solutions The C code of the following example solutions are given in GSM 06.06 5. 6.1 Example solution for error detection in case of unreliable frames With the parameter R0, the average si
47、gnal energy is transmitted. Except at the beginning or the end of a talk spurt, this parameter shows a smooth behaviour from frame to frame. For error detection purposes, the difference of the R0-value between the actual and the last good frame is computed. If this difference exceeds a level depende
48、nt threshold and the frame is marked as unreliable, it is declared unusable by setting the BFI flag equal to “1“. 6.2 Example solution for output signal concealment in case of unreliable frames In the speech decoder, the output signal is created by processing an excitation sequence through an LPC sy
49、nthesis filter. The output signal energy of each subframe is calculated and compared to the output signal energy of the previous subframes. If the difference exceeds a level dependent threshold, the excitation sequence is attenuated such that the output signal energy corresponds to the output signal energy of the previous subframes. 6.3 Example solution for substitution and muting of lost speech frames For the half rate speech decoder, a possible substitution and muting strategy is based on an 8-state machine. The state, with the exception of state
