ETSI EN 300 961 V6.1.1 (2000-11)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Digital cellular telecommunications system (Phase 2+) (GSM); Full rate speech; Transcoding (GSM 06.10 version 6.1.1 Release 1997)33.070.50Globalni sistem za mobilno telekomunikacijo (GSM)Global System for Mobile Communication (GSM)ICS:Ta slovenski standard je istoveten z:EN 300 961 Version 6.1.1SIST EN 300 961 V6.1.1:2003en01-december-2003SIST EN 300 961 V6.1.1:2003SLOVENSKI
STANDARD



SIST EN 300 961 V6.1.1:2003



ETSI EN 300 961 V6.1.1 (2000-11)European Standard (Telecommunications series) Digital cellular telecommunications system (Phase 2+);Full rate speech;Transcoding(GSM 06.10 version 6.1.1 Release 1997)GLOBAL SYSTEM
FOR MOBILE COMMUNICATIONSR
SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)2(GSM 06.10 version 6.1.1 Release 1997)
Reference REN/SMG-110610Q6R1 Keywords Digital cellular telecommunications system, Global System for Mobile communications (GSM) ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE
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© European Telecommunications Standards Institute 2000. All rights reserved.
SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)3(GSM 06.10 version 6.1.1 Release 1997) Contents Intellectual Property Rights.6 Foreword.6 1 Scope.8 1.1 References.8 1.1.1 Abbreviations.9 1.2 Outline description.9 1.3 Functional description of audio parts.9 1.4 PCM Format conversion.10 1.5 Principles of the RPE-LTP encoder.10 1.6 Principles of the RPE-LTP decoder.11 1.7 Sequence and subjective importance of encoded parameters.11 2 Transmission characteristics.14 2.1 Performance characteristics of the analogue/digital interfaces.14 2.2 Transcoder delay.14 3 Functional description of the RPE-LTP codec.14 3.1 Functional description of the RPE-LTP encoder.14 3.1.1 Offset compensation.15 3.1.2 Pre-emphasis.15 3.1.3 Segmentation.15 3.1.4 Autocorrelation.16 3.1.5 Schur Recursion.16 3.1.6 Transformation of reflection coefficients to Log.-Area Ratios.16 3.1.7 Quantization and coding of Log.-Area Ratios.16 3.1.8 Decoding of the quantized Log.-Area Ratios.17 3.1.9 Interpolation of Log.-Area Ratios.17 3.1.10 Transformation of Log.-Area Ratios into reflection coefficients.17 3.1.11 Short term analysis filtering.17 3.1.12 Sub-segmentation.18 3.1.13 Calculation of the LTP parameters.18 3.1.14 Coding/Decoding of the LTP lags.18 3.1.15 Coding/Decoding of the LTP gains.19 3.1.16 Long term analysis filtering.19 3.1.17 Long term synthesis filtering.19 3.1.18 Weighting Filter.20 3.1.19 Adaptive sample rate decimation by RPE grid selection.20 3.1.20 APCM quantization of the selected RPE sequence.20 3.1.21 APCM inverse quantization.21 3.1.22 RPE grid positioning.22 3.2 Decoder.22 3.2.1 RPE decoding clause.22 3.2.2 Long Term Prediction clause.22 3.2.3 Short term synthesis filtering clause.22 3.2.4 Post-processing.22 4 Codec homing.26 4.1 Functional description.26 4.2 Definitions.26 4.3 Encoder homing.27 4.4 Decoder homing.27 4.5 Encoder home state.28 4.6 Decoder home state.28 5 Computational details of the RPE-LTP codec.28 5.1 Data representation and arithmetic operations.28 5.2 Fixed point implementation of the RPE-LTP coder.30 SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)4(GSM 06.10 version 6.1.1 Release 1997) 5.2.0 Scaling of the input variable.31 5.2.1 Downscaling of the input signal.31 5.2.2 Offset compensation.31 5.2.3 Pre-emphasis.31 5.2.4 Autocorrelation.32 5.2.5 Computation of the reflection coefficients.32 5.2.6 Transformation of reflection coefficients to Log.-Area Ratios.33 5.2.7 Quantization and coding of the Log.-Area Ratios.34 5.2.8 Decoding of the coded Log.-Area Ratios.34 5.2.9 Computation of the quantized reflection coefficients.34 5.2.9.1 Interpolation of the LARpp[1.8] to get the LARp[1.8].34 5.2.9.2 Computation of the rp[1.8] from the interpolated LARp[1.8].35 5.2.10 Short term analysis filtering.35 5.2.11 Calculation of the LTP parameters.36 5.2.12 Long term analysis filtering.37 5.2.13 Weighting filter.37 5.2.14 RPE grid selection.38 5.2.15 APCM quantization of the selected RPE sequence.38 5.2.16 APCM inverse quantization.39 5.2.17 RPE grid positioning.39 5.2.18 Update of the reconstructed short term residual signal dp[-120.-1].40 5.3 Fixed point implementation of the RPE-LTP decoder.40 5.3.1 RPE decoding clause.40 5.3.2 Long term synthesis filtering.40 5.3.3 Computation of the decoded reflection coefficients.41 5.3.4 Short term synthesis filtering clause.41 5.3.5 De-emphasis filtering.42 5.3.6 Upscaling of the output signal.42 5.3.7 Truncation of the output variable.42 5.4 Tables used in the fixed point implementation of the RPE-LTP coder and decoder.42 6 Digital test sequences.44 6.1 Input and output signals.44 6.2 Configuration for the application of the test sequences.44 6.2.1 Configuration 1 (encoder only).44 6.2.2 Configuration 2 (decoder only).45 6.3 Test sequences.45 6.3.1 Test sequences for configuration 1.45 6.3.2 Test sequences for configuration 2.46 6.3.3 Additional Test sequences for Codec Homing.50 6.3.3.1 Codec homing frames.50 6.3.3.2 Sequence for an extensive test of the decoder homing.50 6.3.3.3 Sequences for finding the 20 ms framing of the GSM full rate speech encoder.50 6.3.3.4 Formats and sizes of the synchronization sequences.51 Annex A (informative): Codec performance.53 A.1 Performance of the RPE-LTP.53 A.1.1 Introduction.53 A.1.2 Speech performance.53 A.1.2.1 Single encoding.53 A.1.2.2 Speech performance when interconnected with coding systems on an analogue basis.54 A.1.2.2.1 Performance with 32 kbit/s ADPCM (G.721, superseded by G.726).54 A.1.2.2.2 Performance with another RPE-LTP codec.54 A.1.2.2.3 Performance with encoding other than RPE-LTP and 32 kbit/s ADPCM (G.721, superseded by G.726).54 A.1.3 Non-speech performance.55 A.1.3.1 Performance with single sine waves.55 A.1.3.2 Performance with DTMF tones.55 A.1.3.3 Performance with information tones.55 A.1.3.4 Performance with voice-band data.55 A.1.4 Delay.55 A.1.5 Bibliography.57 SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)5(GSM 06.10 version 6.1.1 Release 1997) A.2 Subjective relevance of the speech coder output bits.57 A.3 Format for test sequence distribution.59 A.3.1 Type of files provided.59 A.3.2 File format description.60 Annex B (informative): Test sequence disks.62 Annex C (informative): Change Request History.63 History.64
SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)6(GSM 06.10 version 6.1.1 Release 1997) Intellectual 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 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 (http://www.etsi.org/ipr). 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 to the present document. Foreword This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Special Mobile Group (SMG). The present document specifies the full rate speech transcoding within the digital cellular telecommunications system. NOTE: The present document is a reproduction of recommendation T/L/03/11 "13 kbit/s Regular Pulse Excitation - Long Term Prediction - Linear Predictive Coder for use in the digital cellular telecommunications system". Archive en_300961v060101p0.ZIP which accompanies the present document, contains test sequences, as described in clause 6 and annex A.3. The archive contains the following: Disk1.zip Annex B: Test sequences for the GSM Full Rate speech codec; Test sequences SEQ01.xxx to SEQ05.xxx. (Disk1.zip contains LHA compressed files.) Disk2.zip Annex B: Test sequences for the GSM Full Rate speech codec with homing frames; Test sequences SEQ01H.* to SEQ02H.*. Disk3.zip Annex B: Test sequences for the GSM Full Rate speech codec with homing frames; Test sequences SEQ03H.* to SYNC159.COD. Disk4.zip Annex B: 8 bit A-law test sequences for the GSM Full Rate speech codec with and without homing frames (Disk4.zip contains self-extracting files). Disk5.zip Annex B: 8 bit µ-law test sequences for the GSM Full Rate speech codec with and without
homing frames (Disk5.zip contains self-extracting files). The contents of the present document is subject to continuing work within SMG and may change following formal SMG approval. Should SMG modify the contents of the present document it will be re-released with an identifying change of release date and an increase in version number as follows: Version 6.x.y where: 6 indicates Release 1997 of GSM Phase 2+. x the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections, updates, etc. y the third digit is incremented when editorial only changes have been incorporated in the specification.
SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)7(GSM 06.10 version 6.1.1 Release 1997) National transposition dates Date of adoption of this EN: 24 November 2000 Date of latest announcement of this EN (doa): 28 February 2001 Date of latest publication of new National Standard or endorsement of this EN (dop/e):
31 August 2001 Date of withdrawal of any conflicting National Standard (dow): 31 August 2001
SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)8(GSM 06.10 version 6.1.1 Release 1997) 1 Scope The transcoding procedure specified in the present document is applicable for the full-rate Traffic Channel (TCH) in the digital cellular telecommunications system. The use of this transcoding scheme for other applications has not been considered. In GSM 06.01, a reference configuration for the speech transmission chain of the digital cellular telecommunications system is shown. According to this reference configuration, the speech encoder takes its input as a 13 bit uniform PCM signal either from the audio part of the mobile station or on the network side, from the PSTN via an 8 bit/A-law to 13 bit uniform PCM conversion. The encoded speech at the output of the speech encoder is delivered to a channel encoder unit which is specified in GSM 05.03. In the receive direction, the inverse operations take place. The present document describes the detailed mapping between input blocks of 160 speech samples in 13 bit uniform PCM format to encoded blocks of 260 bits and from encoded blocks of 260 bits to output blocks of 160 reconstructed speech samples. The sampling rate is 8000 sample/s leading to an average bit rate for the encoded bit stream of 13 kbit/s. The coding scheme is the so-called Regular Pulse Excitation - Long Term prediction - Linear Predictive Coder, here-after referred to as RPE-LTP. The present document also specifies the conversion between A-law PCM and 13 bit uniform PCM. Performance requirements for the audio input and output parts are included only to the extent that they affect the transcoder performance. The present document also describes the codec down to the bit level, thus enabling the verification of compliance to the present document to a high degree of confidence by use of a set of digital test sequences. These test sequences are described and are contained in archive en_300961v060101p0.ZIP which accompanies the present document. 1.1 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 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. • A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same number. • For this Release 1997 document, references to GSM documents are for Release 1997 versions (version 6.x.y). [1] GSM 01.04: "Digital cellular telecommunications system (Phase 2+); Abbreviations and acronyms". [2] GSM 05.03: "Digital cellular telecommunications system (Phase 2+); Channel coding". [3] GSM 06.01: "Digital cellular telecommunications system (Phase 2+); Full rate speech; Processing functions". [4] GSM 11.10: "Digital cellular telecommunications system (Phase 2+); Mobile Station (MS) conformity specification". [5] ETS 300 085: "Integrated Services Digital Network (ISDN); 3,1kHz telephony teleservice; Attachment requirements for handset terminals (Candidate NET 33)". [6] ITU-T Recommendation G.711: "Pulse code modulation (PCM) of voice frequencies". [7] ITU-T Recommendation G.712: "Transmission performance characteristics of pulse code modulation". SIST EN 300 961 V6.1.1:2003



ETSI ETSI EN 300 961 V6.1.1 (2000-11)9(GSM 06.10 version 6.1.1 Release 1997) [8] ITU-T Recommendation G.726: "40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM)". [9] ITU-T Recommendation Q.35: "Technical characteristics of tones for the telephone service". [10] ITU-T Recommendation V.21: "300 bits per second duplex modem standardized for use in the general switched telephone network". [11] ITU-T Recommendation V.23: "600/1 200-band modem standardized for use in the general switched telephone network". [12] GSM 06.32: "Digital cellular telecommunications system (Phase 2+); Voice Activity Detector (VAD)". 1.1.1 Abbreviations Abbreviations used in the present document are listed in GSM 01.04. 1.2 Outline description The present document is structured as follows: Subclause 1.3 contains a functional description of the audio parts including the A/D and D/A functions. Subclause 1.4 describes the conversion between 13 bit uniform and 8 bit A-law samples. Subclauses 1.5 and 1.6 present a simplified description of the principles of the RPE-LTP encoding and decoding process respectively. In clause 1.7, the sequence and subjective importance of encoded parameters are given. Clause 2 deals with the transmission characteristics of the audio parts that are relevant for the performance of the RPE-LTP codec. Some transmission characteristics of the RPE-LTP codec are also specified in clause 2. Clause 3 presents the functional description of the RPE-LTP coding and decoding procedures, whereas clause 4 describes the computational details of the algorithm. Procedures for the verification of the correct functioning of the RPE-LTP are described in clause 5. Performance and network aspects of the RPE-LTP codec are contained in annex A. 1.3 Functional description of audio parts The analogue-to-digital and digital-to-analogue conversion will in principle comprise the following elements: 1) Analogue to uniform digital: - microphone; - input level adjustment device; - input anti-aliasing filter; - sample-hold device sampling at 8 kHz; - analogue-to-uniform digital conversion to 13 bits representation. The uniform format shall be represented in two’s complement. 2) Uniform digital to analogue: - conversion from 13 bit /8 kHz uniform PCM to analogue; - a hold device; - reconstruction filter including x/sin x correction; - output level adjustment device; SIST EN
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