1、 ETSI TS 146 082 V14.0.0 (2017-04) Digital cellular telecommunications system (Phase 2+) (GSM); Voice Activity Detector (VAD) for Enhanced Full Rate (EFR) speech traffic channels (3GPP TS 46.082 version 14.0.0 Release 14) TECHNICAL SPECIFICATION GLOBAL SYSTEM FOR MOBILE COMMUNICATIONSRETSI ETSI TS 1
2、46 082 V14.0.0 (2017-04)13GPP TS 46.082 version 14.0.0 Release 14Reference RTS/TSGS-0446082ve00 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 enregistr
3、e 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 present documen
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9、SI ETSI TS 146 082 V14.0.0 (2017-04)23GPP TS 46.082 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 ETSI members
10、 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:/ipr.etsi.or
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12、esent 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 as being r
13、eferences 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“, “will“, “will
14、 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 146 082 V14.0.0 (2017-04)33GPP TS 46.082
15、 version 14.0.0 Release 14Contents Intellectual Property Rights 2g3Foreword . 2g3Modal verbs terminology 2g3Foreword . 4g31 Scope 5g32 References 5g33 Definitions, symbols and abbreviations . 5g33.1 Definitions 5g33.2 Symbols 5g33.2.1 Variables . 5g33.2.2 Constants 6g33.2.3 Functions 6g33.3 Abbrevia
16、tions . 7g34 General . 7g35 Functional description 7g35.1 Overview and principles of operation 7g35.2 Algorithm description . 7g35.2.1 Adaptive filtering and energy computation 8g35.2.2 ACF averaging 9g35.2.3 Predictor values computation 9g35.2.4 Spectral comparison 10g35.2.5 Information tone detect
17、ion 10g35.2.6 Threshold adaptation. 11g35.2.7 VAD decision . 12g35.2.8 VAD hangover addition 13g35.2.9 Periodicity detection . 13g36 Computational description overview 14g36.1 VAD modules . 14g36.2 Pseudo-floating point arithmetic 14g3Annex A (informative): Simplified block filtering operation . 16g
18、3Annex B (informative): Pole frequency calculation 17g3Annex C (informative): Change history . 18g3History 19g3ETSI ETSI TS 146 082 V14.0.0 (2017-04)43GPP TS 46.082 version 14.0.0 Release 14Foreword This Technical Specification has been produced by the 3rdGeneration Partnership Project (3GPP). The p
19、resent document specifies the Voice Activity Detector (VAD) to be used in the Discontinuous Transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels within the digital cellular telecommunications system. The contents of the present document are subject to continuing work within the TS
20、G 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 for inform
21、ation; 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 been in
22、corporated in the document. ETSI ETSI TS 146 082 V14.0.0 (2017-04)53GPP TS 46.082 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 06.81 5 Discontinuous transmission (DTX) for Enha
23、nced Full Rate (EFR) speech traffic channels. The requirements are mandatory on any VAD to be used either in GSM Mobile Stations (MS)s or Base Station Systems (BSS)s that utilize the enhanced full-rate speech traffic channel. 2 References The following documents contain provisions which, through ref
24、erence in this text, constitute 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
25、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 of that document in the same Release as the present document. 1 GSM 01.04: “Digital cellular telecommunications system (Phase 2+); Abbreviations and acr
26、onyms“. 2 GSM 06.53: “Digital cellular telecommunications system (Phase 2+); ANSI-C code for the GSM Enhanced Full Rate (EFR) speech codec“. 3 GSM 06.54: “Digital cellular telecommunications system (Phase 2+); Test vectors for the GSM Enhanced Full Rate (EFR) speech codec“. 4 GSM 06.60: “Digital cel
27、lular telecommunications system (Phase 2+); Enhanced Full Rate (EFR) speech transcoding“. 5 GSM 06.81: “Digital cellular telecommunications system (Phase 2+); Discontinuous transmission (DTX) for Enhanced Full Rate (EFR) speech traffic channels“. 3 Definitions, symbols and abbreviations 3.1 Definiti
28、ons For the purposes of the present document, the following terms and definitions apply: noise: signal component resulting from acoustic environmental noise. mobile environment: any environment in which mobile stations may be used. 3.2 Symbols For the purposes of the present document, the following
29、symbols apply: 3.2.1 Variables aav1 filter predictor values, see clause 5.2.3 acf the ACF vector which is calculated in the speech encoder (GSM 06.60 4) ETSI ETSI TS 146 082 V14.0.0 (2017-04)63GPP TS 46.082 version 14.0.0 Release 14adaptcount secondary hangover counter, see clause 5.2.6 av0 averaged
30、 ACF vector, see clause 5.2.2 av1 a previous value of av0, see clause 5.2.2 burstcount speech burst length counter, see clause 5.2.8 den denominator of left hand side of equation 8 in annex B, see clause 5.2.5 difference difference between consecutive values of dm, see clause 5.2.4 dm spectral disto
31、rtion measure, see clause 5.2.4 hangcount primary hangover counter, see clause 5.2.8 lagcount number of subframes in current frame meeting periodicity criterion, see clause 5.2.9 lastdm previous value of dm, see clause 5.2.4 lags the open loop long term predictor lags for the two halves of the speec
32、h encoder frame (GSM 06.60 4) num numerator of left hand side of equation 8 in annex B, see clause 5.2.5 oldlagcount previous value of lagcount, see clause 5.2.9 prederr fourth order short term prediction error, see clause 5.2.5 ptch Boolean flag indicating the presence of a periodic signal componen
33、t, see clause 5.2.9 pvad energy in the current filtered signal frame, see clause 5.2.1 rav1 autocorrelation vector obtained from av1, see clause 5.2.3 rc the first four unquantized reflection coefficients calculated in the speech encoder (GSM 06.60 4) rvad autocorrelation vector of the adaptive filt
34、er predictor values, see clause 5.2.6 smallag difference between consecutive lag values, see clause 5.2.9 stat Boolean flag indicating that the frequency spectrum of the input signal is stationary, see clause 5.2.4 thvad adaptive primary VAD threshold, see clause 5.2.6 tone Boolean flag indicating t
35、he presence of an information tone, see clause 5.2.5 vadflag Boolean VAD decision with hangover included, see clause 5.2.8 veryoldlagcount previous value of oldlagcount, see clause 5.2.9 vvad Boolean VAD decision before hangover, see clause 5.2.7 3.2.2 Constants adp number of frames of hangover for
36、secondary VAD, see clause 5.2.6 burstconst minimum length of speech burst to which hangover is added, see clause 5.2.8 dec determines rate of decrease in adaptive threshold, see clause 5.2.6 fac determines steady state adaptive threshold, see clause 5.2.6 frames number of frames over which av0 and a
37、v1 are calculated, see clause 5.2.2 freqth threshold for pole frequency decision, see clause 5.2.5 hangconst number of frames of hangover for primary VAD, see clause 5.2.8 inc determines rate of increase in adaptive threshold, see clause 5.2.6 lthresh lag difference threshold for periodicity decisio
38、n, see clause 5.2.9 margin determines upper limit for adaptive threshold, see clause 5.2.6 nthresh frame count threshold for periodicity decision, see clause 5.2.9 plev lower limit for adaptive threshold, see clause 5.2.6 predth threshold for short term prediction error, see clause 5.2.5 pth energy
39、threshold, see clause 5.2.6 thresh decision threshold for evaluation of stat flag, see clause 5.2.4 3.2.3 Functions + addition - subtraction * multiplication / division | x | absolute value of x AND Boolean AND OR Boolean ORb MULT(x(i) the product of the series x(i) for i=a to b i=a b SUM(x(i) the s
40、um of the series x(i) for i=a to b ETSI ETSI TS 146 082 V14.0.0 (2017-04)73GPP TS 46.082 version 14.0.0 Release 14i=a 3.3 Abbreviations For the purposes of the present document, the following abbreviations apply: ACF Autocorrelation function ANSI American National Standards Institute DTX Discontinuo
41、us Transmission LTP Long Term Predictor TX Transmission VAD Voice Activity Detector For abbreviations not given in this clause, see 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 not. The output is a Boolean fl
42、ag (vadflag) which is used by the Transmit (TX) DTX handler defined in GSM 06.81 5. The present document is organized as follows. Clause 5 describes the principles of operation of the VAD. Clause 6 provides an overview of the computational description of the VAD. The computational details necessary
43、for the fixed point implementation of the VAD algorithm are given in the form of ANSI C program contained in GSM 06.53 2. The verification of the VAD is based on the use of digital test sequences which are described in GSM 06.54 3. 5 Functional description The purpose of this clause is to give the r
44、eader an understanding of the principles of operation of the VAD, whereas GSM 06.53 2 contains the fixed point computational description of the VAD. In the case of discrepancy between the two descriptions, the description in GSM 06.53 2 will prevail. 5.1 Overview and principles of operation The func
45、tion of the VAD is to distinguish between noise with speech present and noise without speech present. This is achieved by comparing the energy of a filtered version of the input signal with a threshold. The presence of speech is indicated whenever the threshold is exceeded. The detection of speech i
46、n a mobile environment is difficult due to the low speech/noise ratios which are encountered, particularly in moving vehicles. To increase the probability of detecting speech the input signal is adaptively filtered (see clause 5.2.1) to reduce its noise content before the voice activity decision is
47、made (see clause 5.2.7). The frequency spectrum and level of the noise may vary within a given environment as well as between different environments. It is therefore necessary to adapt the input filter coefficients and energy threshold at regular intervals as described in clause 5.2.6. 5.2 Algorithm
48、 description The block diagram of the VAD algorithm is shown in figure 1. The individual blocks are described in the following clauses. The variables shown in the block diagram are described in table 1. ETSI ETSI TS 146 082 V14.0.0 (2017-04)83GPP TS 46.082 version 14.0.0 Release 14Table 1: Descripti
49、on of variables in figure 1 Var Description acf The ACF vector which is calculated in the speech encoder (GSM 06.60 4). av0 Averaged ACF vector. av1 A previous value of av0. lags The open loop long term predictor lags for the two halves of the speech encoder frame (GSM 06.60 4). ptch Boolean flag indicating the presence of a periodic signal component. pvad Energy in the current filtered signal frame. rav1 Autocorrelation vector obtained from av1. rc The first four reflection coefficients calculated in the speech encoder (GSM 06.60 4
