1、 ETSI TS 146 032 V14.0.0 (2017-04) Digital cellular telecommunications system (Phase 2+) (GSM); Full rate speech; Voice Activity Detector (VAD) for full rate speech traffic channels (3GPP TS 46.032 version 14.0.0 Release 14) floppy3TECHNICAL SPECIFICATION GLOBAL SYSTEM FOR MOBILE COMMUNICATIONSRETSI
2、 ETSI TS 146 032 V14.0.0 (2017-04)13GPP TS 46.032 version 14.0.0 Release 14Reference RTS/TSGS-0446032ve00 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 prese
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9、iation. ETSI ETSI TS 146 032 V14.0.0 (2017-04)23GPP TS 46.032 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 ET
10、SI 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:/i
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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
13、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“, “wi
14、ll“, “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 146 032 V14.0.0 (2017-04)33GPP
15、 TS 46.032 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 5g31 Scope 6g32 References 6g33 Abbreviations . 6g34 General . 6g35 Functional description 7g35.1 Overview and principles of operation 7g35.2 Algorithm description . 7g35.
16、2.1 Adaptive filtering and energy computation 9g35.2.2 ACF averaging 9g35.2.3 Predictor values computation 9g35.2.4 Spectral comparison 10g35.2.5 Periodicity detection . 10g35.2.6 Information tone detection 11g35.2.7 Threshold adaptation. 12g35.2.8 VAD decision . 15g35.2.9 VAD hangover addition 15g3
17、6 Computational details . 15g36.1 Adaptive filtering and energy computation 17g36.2 ACF averaging . 18g36.3 Predictor values computation . 18g36.3.1 Schur recursion to compute reflection coefficients . 19g36.3.2 Step-up procedure to obtain the aav108 . 19g36.3.3 Computation of the rav108 . 20g36.4 S
18、pectral comparison . 20g36.5 Periodicity detection . 21g36.6 Threshold adaptation 21g36.7 VAD decision . 23g36.8 VAD hangover addition . 23g36.9 Periodicity updating . 24g36.10 Tone detection 24g36.10.1 Windowing . 24g36.10.2 Auto-correlation 24g36.10.3 Computation of the reflection coefficients 25g
19、36.10.4 Filter coefficient calculation . 26g36.10.5 Pole Frequency Test 26g36.10.6 Prediction gain test 26g37 Digital test sequences . 27g37.1 Test configuration. 27g37.2 Test sequences 28g3Annex A (informative): . 29g3A.1 Simplified block filtering operation . 29g3A.2 Description of digital test se
20、quences 29g3A.2.1 Test sequences 29g3A.2.2 File format description . 31g3A.3 VAD performance 33g3ETSI ETSI TS 146 032 V14.0.0 (2017-04)43GPP TS 46.032 version 14.0.0 Release 14A.4 Pole frequency calculation . 34g3Annex B (normative): Test sequences 35g3Annex C (informative): Change history . 36g3His
21、tory 37g3ETSI ETSI TS 146 032 V14.0.0 (2017-04)53GPP TS 46.032 version 14.0.0 Release 14Foreword This Technical Specification has been produced by the 3rdGeneration Partnership Project (3GPP). The present document specifies the Voice Activity Detector (VAD) to be used in the Discontinuous Transmissi
22、on (DTX) for the digital cellular telecommunications system. Archive en_300965v080000p0.zip which accompanies the present document, contains test sequences, as described in clause A.2. en_300965v080000p0.zip Annex B: Test sequences for the GSM Full Rate speech codec; Test sequences files *.inp, *.co
23、d, *.vad. The specification from which the present document has been derived was originally based on CEPT documentation, hence the presentation of the present document may not be entirely in accordance with the ETSI/PNE Rules. The contents of the present document are subject to continuing work withi
24、n 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 number as follows: Version x.y.z where: x the first digit: 1 presented to TSG fo
25、r 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, updates, etc. z the third digit is incremented when editorial only changes have
26、 been incorporated in the document. ETSI ETSI TS 146 032 V14.0.0 (2017-04)63GPP TS 46.032 version 14.0.0 Release 141 Scope The present document specifies the Voice Activity Detector (VAD) to be used in the Discontinuous Transmission (DTX) as described in GSM 06.31. It also specifies the test methods
27、 to be used to verify that a VAD complies with the technical specification. The requirements are mandatory on any VAD to be used either in the GSM Mobile Stations (MS)s or Base Station Systems (BSS)s. 2 References The following documents contain provisions which, through reference in this text, cons
28、titute provisions of the present document. References are either specific (identified by date of publication, 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
29、 reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document. 1 GSM 01.04: “Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms“. 2 GSM 06.10: “Dig
30、ital cellular telecommunications system(Phase 2+); Full rate speech; Transcoding“. 3 GSM 06.12: “Digital cellular telecommunications system(Phase 2+); Full rate speech; Comfort noise aspect for full rate speech traffic channels“. 4 GSM 06.31: “Digital cellular telecommunications system(Phase 2+); Fu
31、ll rate speech; Discontinuous Transmission (DTX) for full rate speech traffic channels“. 3 Abbreviations Abbreviations used in the present document are listed in GSM 01.04 1. 4 General The function of the VAD is to indicate whether each 20 ms frame produced by the speech encoder contains speech or n
32、ot. The output is a binary flag which is used by the TX DTX handler defined in GSM 06.31 4. The ETS is organized as follows. Clause 2 describes the principles of operation of the VAD. In clause 3, the computational details necessary for the fixed point implementation of the VAD algorithm are given.
33、This clause uses the same notation as used for computational details in GSM 06.10. The verification of the VAD is based on the use of digital test sequences. Clause 4 defines the input and output signals and the test configuration, whereas the detailed description of the test sequences is contained
34、in clause A.2. The performance of the VAD algorithm is characterized by the amount of audible speech clipping it introduces and the percentage activity it indicates. These characteristics for the VAD defined in the present document have been established by extensive testing under a wide range of ope
35、rating conditions. The results are summarized in clause A.3. ETSI ETSI TS 146 032 V14.0.0 (2017-04)73GPP TS 46.032 version 14.0.0 Release 145 Functional description The purpose of this clause is to give the reader an understanding of the principles of operation of the VAD, whereas the detailed descr
36、iption is given in clause 3. In case of discrepancy between the two descriptions, the detailed description of clause 3 shall prevail. In the following subclauses of clause 2, a Pascal programming type of notation has been used to describe the algorithm. 5.1 Overview and principles of operation The f
37、unction of the VAD is to distinguish between noise with speech present and noise without speech present. The biggest difficulty for detecting speech in a mobile environment is the very low speech/noise ratios which are often encountered. The accuracy of the VAD is improved by using filtering to incr
38、ease the speech/noise ratio before the decision is made. For a mobile environment, the worst speech/noise ratios are encountered in moving vehicles. It has been found that the noise is relatively stationary for quite long periods in a mobile environment. It is therefore possible to use an adaptive f
39、ilter with coefficients obtained during noise, to remove much of the vehicle noise. The VAD is basically an energy detector. The energy of the filtered signal is compared with a threshold; speech is indicated whenever the threshold is exceeded. The noise encountered in mobile environments may be con
40、stantly changing in level. The spectrum of the noise can also change, and varies greatly over different vehicles. Because of these changes the VAD threshold and adaptive filter coefficients must be constantly adapted. To give reliable detection the threshold must be sufficiently above the noise leve
41、l to avoid noise being identified as speech but not so far above it that low level parts of speech are identified as noise. The threshold and the adaptive filter coefficients are only updated when speech is not present. It is, of course, potentially dangerous for a VAD to update these values on the
42、basis of its own decision. This adaptation therefore only occurs when the signal seems stationary in the frequency domain but does not have the pitch component inherent in voiced speech. A tone detector is also used to prevent adaptation during information tones. A further mechanism is used to ensur
43、e that low level noise (which is often not stationary over long periods) is not detected as speech. Here, an additional fixed threshold is used. A VAD hangover period is used to eliminate mid-burst clipping of low level speech. Hangover is only added to speech-bursts which exceed a certain duration
44、to avoid extending noise spikes. 5.2 Algorithm description The block diagram of the VAD algorithm is shown in figure 2.1. The individual blocks are described in the following subclauses. ACF, N and sof are calculated in the speech encoder. ETSI ETSI TS 146 032 V14.0.0 (2017-04)83GPP TS 46.032 versio
45、n 14.0.0 Release 14PredictorvaluescomputationACFaveragingSpectralcomparisonPeriodicitydetectionvvadthvadstatrvadpvadACFNav1rav1ptchav0vadAdaptive filtering and energy computationsoftoneTonedetectionVADhangoveradditionVADdecisionThresholdadaptationFigure 2.1: Functional block diagram of the VAD The g
46、lobal variables shown in the block diagram are described as follows: - ACF are auto-correlation coefficients which are calculated in the speech encoder defined in GSM 06.10 (subclause 3.1.4, see also clause A.1). The inputs to the speech encoder are 16 bit 2s complement numbers, as described in GSM
47、06.10, subclause 4.2.0; - av0 and av1 are averaged ACF vectors; - rav1 are autocorrelated predictor values obtained from av1; - rvad are the autocorrelated predictor values of the adaptive filter; - N is the long term predictor lag value which is obtained every sub-segment in the speech coder define
48、d in GSM 06.10; - ptch indicates whether the signal has a steady periodic component; - sof is the offset compensated signal frame obtained in the speech coder defined in GSM 06.10; - pvad is the energy in the current frame of the input signal after filtering; - thvad is an adaptive threshold; - stat
49、 indicates spectral stationarity; - vvad indicates the VAD decision before hangover is added; - vad is the final VAD decision with hangover included. ETSI ETSI TS 146 032 V14.0.0 (2017-04)93GPP TS 46.032 version 14.0.0 Release 145.2.1 Adaptive filtering and energy computation Pvad is computed as follows: Pvad rvad acf rvad acfiii=+=00182 This corresponds to performing an 8th order block filtering on the input samples to the speech encoder, after zero offset compensation and pre-emphasis. This is explained in clause A.1. 5.2.2 ACF averaging Spectral cha
