SIST ETS 300 581-4 E1:2003

• Abstract:

  ..

• Status: Published
• Publication Date: 30-Nov-2003
• ICS: 33.070.50 - Global System for Mobile Communication (GSM)
• Technical Committee: SS EIT - Technical Board for the electrotechnical, information technology and telecommunications fields
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Dec-2003
• Due Date: 01-Dec-2003
• Completion Date: 01-Dec-2003
• Mandate: T-172
• Ref Project: ETSI ETS 300 581-4 ed.1 (1995-12) - European digital cellular telecommunications system; Half rate speech; Part 4: Comfort noise aspects for the half rate speech traffic channels (GSM 06.22)

Overview

SIST ETS 300 581-4 E1:2003 sets the requirements for comfort noise aspects in half rate speech traffic channels within the European digital cellular telecommunications system, specifically GSM. This standard is essential for ensuring high-quality user experience during periods of silence in mobile calls when Discontinuous Transmission (DTX) is employed. By defining the evaluation, encoding, and generation of comfort noise, the standard helps prevent abrupt drops in background noise that could otherwise result in perceived call quality degradation.

This standard is mandatory for all GSM Mobile Stations (MS) and Base Station Systems (BSS) supporting half rate speech channels, ensuring consistent implementation and interoperability across the GSM ecosystem.

Key Topics

• Background Acoustic Noise Evaluation: Methods for evaluating and averaging the background noise characteristics during speech inactivity using parameters such as frame energy and autocorrelation coefficients.
• SID Frames and Coding: Specification of the Silence Descriptor (SID) frame, which carries encoded comfort noise parameters to the receiver. SID frame structure is optimized to uniquely identify comfort noise periods.
• TX and RX Functions: Separate procedures for transmit (TX) and receive (RX) sides, detailing how noise parameters are calculated, encoded, transmitted, and decoded.
• Parameter Averaging and Freezing: Requirements for averaging selected parameters (e.g., GS energy tweak) and holding their values steady during comfort noise periods.
• Comfort Noise Generation: Guidelines for synthesizing comfort noise that closely matches the transmitter’s background environment, updating parameters upon receiving new SID frames to maintain a natural user experience.
• Interoperability and Compliance: Ensures that all compatible GSM devices generate, encode, transmit, and interpret comfort noise consistently, regardless of manufacturer.

Applications

SIST ETS 300 581-4 E1:2003 is vital for:

• GSM Mobile Networks: Guarantees a natural audio background during silent periods, preventing sudden and unnatural silences that can occur during DTX.
• Mobile Device Manufacturers: Provides precise technical instructions for implementing comfort noise features in handsets and base station equipment.
• Network Operators: Helps deliver consistently high speech quality and user experience, reducing complaints about call quality related to noise artifacts.
• Telecom System Integrators: Ensures comfort noise handling is aligned across all GSM network elements operating with half rate speech encoders and decoders.

By adhering to this standard, GSM network stakeholders maintain compatibility and superior audio handling, even as network equipment and devices evolve.

Related Standards

For comprehensive implementation and interoperability within the GSM digital cellular system, consider these related standards:

• SIST ETS 300 581-1 (GSM 06.02): Half rate speech processing functions
• SIST ETS 300 581-2 (GSM 06.20): Half rate speech transcoding
• SIST ETS 300 581-3 (GSM 06.21): Substitution and muting of lost frames for half rate speech
• SIST ETS 300 581-5 (GSM 06.41): Discontinuous Transmission (DTX) for half rate speech traffic channels
• SIST ETS 300 581-6 (GSM 06.42): Voice Activity Detection (VAD) for half rate speech channels
• SIST ETS 300 581-7 (GSM 06.06): ANSI-C code for GSM half rate speech codec
• SIST ETS 300 581-8 (GSM 06.07): Test vectors for GSM half rate speech codec

These standards collectively ensure robust, interoperable implementation of GSM half rate speech services, with clear handling of comfort noise in digital mobile telecommunications.

SLOVENSKI STANDARD
01-december-2003
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European digital cellular telecommunications system; Half rate speech; Part 4: Comfort
noise aspects for the half rate speech traffic channels (GSM 06.22)
Ta slovenski standard je istoveten z: ETS 300 581-4 Edition 1
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 581-4
TELECOMMUNICATION November 1995
STANDARD
Source: ETSI TC-SMG Reference: DE/SMG-020622
ICS: 33.060.50
European digital cellular telecommunications system, Global System for Mobile communications
Key words:
(GSM)
European digital cellular telecommunications system;
Half rate speech
Part 4: Comfort noise aspects for the half rate
speech traffic channels
(GSM 06.22)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - [e-mail]
X.400: Internet:
Tel.: [phone] - Fax: [phone]
*
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.

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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.

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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Definitions, symbols and abbreviations.7
3.1 Definitions .7
3.2 Symbols .8
4 General.9
5 Functions on the transmit (TX) side .9
5.1 Background acoustic noise evaluation .9
5.2 Modification of the speech encoding algorithm during SID frame generation .11
5.3 SID-frame encoding.12
6 Functions on the receive (RX) side .12
6.1 Averaging of the GS parameters .12
6.2 Comfort noise generation and updating.13
7 Computational details.14
History.15

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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
Foreword
This European Telecommunication Standard (ETS) has been produced by the Special Mobile Group
(SMG) Technical Committee of the European Telecommunications Standards Institute (ETSI).
This ETS specifies the half rate speech traffic channels for the European digital cellular
telecommunications system. This ETS corresponds to GSM technical specification, GSM 06.22, version
4.1.1 and is part 4 of a multi-part ETS covering the half rate speech traffic channels as described below:
GSM 06.02 ETS 300 581-1: "European digital cellular telecommunications system;
Half rate speech Part 1: Half rate speech processing functions".
GSM 06.20 ETS 300 581-2: "European digital cellular telecommunications system;
Half rate speech Part 2: Half rate speech transcoding".
GSM 06.21 ETS 300 581-3: "European digital cellular telecommunications system;
Half rate speech Part 3: Substitution and muting of lost frames for half rate
speech traffic channels".
GSM 06.22 ETS 300 581-4: "European digital cellular telecommunications system;
Half rate speech Part 4: Comfort noise aspects for half rate speech traffic
channels".
GSM 06.41 ETS 300 581-5: "European digital cellular telecommunications system;
Half rate speech Part 5: Discontinuous Transmission (DTX) for half rate speech
traffic channels".
GSM 06.42 ETS 300 581-6: "European digital cellular telecommunications system;
Half rate speech Part 6: Voice Activity Detection (VAD) for half rate speech
traffic channels".
GSM 06.06 ETS 300 581-7: "European digital cellular telecommunications system;
Half rate speech Part 7: ANSI-C code for the GSM half rate speech codec".
GSM 06.07 ETS 300 581-8: "European digital cellular telecommunications system;
Half rate speech Part 8: Test vectors for the GSM half rate speech codec".
NOTE: TC-SMG has produced documents which give the technical specifications for the
implementation of the European digital cellular telecommunications system.
Historically, these documents have been identified as GSM Technical Specifications
(GSM-TS). These TSs may have subsequently become Interim European
Telecommunication Standards (I-ETSs), (Phase 1), or European Telecommunication
Standards (ETSs), (Phase 2), whilst others may become ETSI Technical Reports
(ETRs).
Transposition dates
Date of adoption of this ETS: 27 October 1995
Date of latest announcement of this ETS (doa): 28 February 1996
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 31 August 1996
Date of withdrawal of any conflicting National Standard (dow): 31 August 1996

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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
1 Scope
This European Telecommunication Standard (ETS) gives the detailed requirements for the correct operation
of the background acoustic noise evaluation, noise parameter encoding/decoding and comfort noise
generation in GSM Mobile Stations (MS)s and Base Station Systems (BSS)s during Discontinuous
Transmission (DTX) on half rate speech traffic channels.
The requirements described in this ETS are mandatory for implementation in all GSM MSs capable of
supporting the half rate speech traffic channel.
The receiver requirements are mandatory for implementation in all GSM BSSs capable of supporting the
half rate speech traffic channel, the transmitter requirements are only for those where downlink DTX will
be used.
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references, the
latest edition of the publication referred to applies.
[1] GSM 01.04 (ETR 100): "European digital cellular telecommunication system
(Phase 2); Abbreviations and acronyms".
[2] GSM 06.20 (ETS 300 581-2): "European digital cellular telecommunications
system; Half rate speech Part 2: Half rate speech transcoding".
[3] GSM 06.41 (ETS 300 581-5): "European digital cellular telecommunications
system; Half rate speech Part 5: Discontinuous transmission (DTX) for half rate
speech traffic channels".
[4] GSM 06.42 (ETS 300 581-6): "European digital cellular telecommunications
system; Half rate speech Part 6: Voice Activity Detector (VAD) for half rate
speech traffic channels".
[5] GSM 06.06 (ETS 300 581-7): "European digital cellular telecommunications
system; Half rate speech Part 7: ANSI-C code for the GSM half rate speech
codec".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purpose of this ETS, the following definition apply.
frame: Time interval of 20 ms corresponding to the time segmentation of the half rate speech transcoder,
also used as a short term for a traffic frame.
SID frame: Rame characterised by the SID (Silence Descriptor) codeword. It conveys information on the
acoustic background noise.
SID codeword: Fixed bit pattern for labelling a traffic frame as a SID frame.
SID field: The bit positions of the SID codeword within a SID frame.
speech frame: Traffic frame that cannot be classified as a SID frame.
VAD flag: Voice Activity Detector flag.
SP flag: SPeech flag.
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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
W(Z): Spectral weighting filter of the GSM half rate speech codec.
H(Z): Combination of the short term (spectral) filter A(z) and the spectral weighting filter W(z).
Other definition of terms used in this ETS can be found in GSM 06.20 (ETS 300 581-2) [2] and
GSM 06.41 (ETS 300 581-5) [3]. The overall operation of DTX is described in
GSM 06.41 (ETS 300 581- 5) [3].
3.2 Symbols
For the purpose of this ETS, the following symbols apply.
GS Energy tweak parameter.
R0 Frame energy value.
R(i) Unquantised (normalised) autocorrelation sequence.
r Optimal reflection coefficient.
j
b
SUM ( x(n) ) = x(a) + x(a+1) + . + x(b-1) + x(b);  (Accumulation)
n=a
GSP0 codeword Vector quantization index, joint vector quantization of the parameters GS and
P0.
P0 Power contribution of the first excitation vector as a fraction of the total
excitation power at a subframe.
3.3 Abbreviations
For the purpose of this ETS, the following abbreviations apply:
AFLAT Autocorrelation Fixed Point LAttice Technique (used in the GSM half rate
speech codec for the vector quantization of the LPC coefficients)
BSS Base Station System
DTX Discontinuous Transmission
ETS European Telecommunication Standard
GSM Global System for Mobile communications
MS Mobile Station
SID SIlence Descriptor
RX Receive
TX Transmit
VAD Voice Activity Detector
VQ Vector Quantization
For abbreviations not given in this subclause, see GSM 01.04 (ETR 100) [1].

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ETS 300 581-4: November 1995 (GSM 06.22 version 4.1.1)
4 General
A problem when using DTX is that the background acoustic noise, which is transmitted together with the
speech, would disappear when the radio transmission is switched off, resulting in a modulation of the
background noise. Since the DTX switching can take place rapidly, it has been found that this effect may be
annoying for the listener, especially in a car environment with high background noise levels. In bad cases,
the speech may be hardly intelligible.
This ETS specifies a solution to overcome this problem by generating s
...