ETSI TS 102 929 V2.3.1 (2018-03)

Speech and multimedia Transmission Quality (STQ); Procedures for the identification and selection of common modes of de-jitter buffers and echo cancellers

RTS/STQ-267

General Information

• Status: Published
• Publication Date: 15-Mar-2018
• Technical Committee: STQ - Speech and multimedia Transmission Quality
• Current Stage: 12 - Completion
• Due Date: 22-Mar-2018
• Completion Date: 16-Mar-2018

Standards Content (Sample)

TECHNICAL SPECIFICATION
Speech and multimedia Transmission Quality (STQ);
Procedures for the identification and selection of
common modes of de-jitter buffers and echo cancellers

2 ETSI TS 102 929 V2.3.1 (2018-03)

Reference
RTS/STQ-267
Keywords
de-jitter buffer, QoS, quality
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3 ETSI TS 102 929 V2.3.1 (2018-03)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 7
3 Definitions and abbreviations . 9
3.1 Definitions . 9
3.2 Abbreviations . 10
4 Characteristics of de-jitter buffers . 11
4.1 De-Jitter buffers . 11
4.2 Purpose, operation and environment . 12
4.3 External enabling of fixed de-jitter buffers . 12
5 Characteristics of VBD-mode switching of de-jitter buffers . 12
5.1 General . 12
5.2 Detector characteristics . 13
5.2.1 Detector characteristics for frequency range of 2 100 Hz ± 21 Hz . 13
5.2.2 Detector characteristics for dual-frequency tones 1 375 Hz + 2 002 Hz and 1 529 Hz + 2 225 Hz
(Recommendation ITU-T V.8bis) . 14
5.2.3 Detector characteristics for frequencies 980 Hz, 1 180 Hz, 1 650 Hz and 1 850 Hz (V.21). 14
5.2.4 Detector characteristics for 2 100 Hz amplitude-modulated by a sinewave at 15 Hz, 2 100 Hz
amplitude-modulated by a sinewave at 15 Hz with phase reversals, 1 300 Hz and 1 100 Hz (V.8) . 14
5.2.5 Detector characteristics for V.22 . 15
5.2.6 Detector characteristics for 2 100 Hz with phase reversals (V.25) . 17
5.2.7 Detector characteristics for Recommendation ITU-T V.32/V.32bis . 19
5.2.8 Detector characteristics for Recommendation ITU-T T.30 . 19
5.2.9 Noise tolerance . 20
5.2.10 Operate time. 20
5.2.11 False operation due to speech signals . 20
5.2.12 Release time . 21
5.2.13 Other considerations . 21
6 Activation of de-jitter buffer for VBD . 21
7 Activation of de-jitter buffer for 64 kbit/s bit sequence (UDI) . 25
8 Requirements for values of de-jitter buffers . 26
8.1 Fixed de-jitter buffers . 26
8.2 Adaptive de-jitter buffers . 26
8.3 Activation procedure into the fixed mode . 26
8.4 Transition from VBD to Voice mode (Recommendation ITU-T V.152) . 27
8.5 Handling of De-jitter buffer in case of lost or late packets . 28
9 Echo canceller . 29
9.1 Introduction . 29
9.2 Characteristics of an echo canceller tone disabler (Recommendation ITU-T G.168) . 29
9.2.1 General . 29
9.2.2 Detector characteristics . 29
9.2.3 Phase reversal detection . 30
9.2.4 Guard band characteristics . 30
9.2.5 Noise tolerance . 31
9.2.6 Holding-band characteristics . 31
9.2.7 Operate time. 31
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4 ETSI TS 102 929 V2.3.1 (2018-03)
9.2.8 False operation due to speech currents . 32
9.2.9 False operation due to data signals . 32
9.2.10 Release time . 32
9.2.11 Other considerations . 32
10 Transmission Requirements for MGWs with respect to voice and data (VBD) and 64 Kbit/s
transparent data service . 32
10.1 Introduction: considerations on de-jitter buffer settings . 32
10.2 Codec Specific Requirements with respect to voice band data (VBD) . 33
10.2.0 Introduction. 33
10.2.1 Roundtrip delay . 33
10.3 Specific Requirements with respect to 64 kbit/s transparent data service . 34
10.3.1 Roundtrip delay and IP packet loss ratio . 34
Annex A (normative): De-jitter buffer Facsimile tests . 35
A.1 Measurement method . 35
Annex B (normative): Echo canceller Tests . 64
B.1 Introduction . 64
B.1.1 Signals used . 64
B.1.2 Preparatory measurements. 64
B.2 Tests with echo simulation at Interface B . 65
B.2.1 Introduction . 65
B.2.2 Tests with test signals based on Composite Source Signal (CSS) . 66
B.2.2.1 Answer tones + C16 . 66
B.2.2.2 Answer tones + first fax frame + C16 . 67
B.2.2.3 Tests with test signals based on the Use of the CI call signal and exchange of CM/JM menu signals
+ C16 . 68
B.2.2.4 Tests with test signals based on DTMF . 69
B.2.2.4.1 Answer tones + D16 . 69
B.2.2.5 Tests with test signals based on the Use of the CI call signal and exchange of CM/JM menu signals
+ D16 . 70
B.3 Tests with echo simulation at Interface A . 71
B.3.1 Introduction . 71
B.3.2 Tests with test signals based on CSS . 72
B.3.2.1 Answer tones + C16 . 72
B.3.2.2 Answer tones + first fax frame + C16 . 73
B.3.2.3 Tests with test signals based on the Use of the CI call signal and exchange of CM/JM menu signals
+ C16 . 74
B.3.2.4 Tests with test signals based on DTMF . 75
B.3.2.4.1 Answer tones + D16 . 75
B.3.2.5 Tests with test signals based on the Use of the CI call signal and exchange of CM/JM menu signals
+ D16 . 76
B.4 Tests with test signals based on the data rate change between V.34 and V.17 Fax Terminals . 77
Annex C (informative): Features of V.17 Fax and V.34 Fax . 79
C.1 Features of V.17 Fax (V.17 Fax Modem) . 79
C.2 V.34 High-Speed Fax . 79
C.2.1 Features . 79
C.2.2 The Recommendation ITU-T V.34 Fax Standard . 79
C.3 The V.34 Fax Connection and Session . 80
C.4 ECM as a Mandatory Feature . 81
History . 82

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5 ETSI TS 102 929 V2.3.1 (2018-03)
Intellectual Property Rights
Essential patents
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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
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Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
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Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Speech and multimedia
Transmission Quality (STQ).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "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.
Introduction
The present document describes the characteristics of a de-jitter buffer, including the requirement for in-band tone
activating and other control mechanisms.
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6 ETSI TS 102 929 V2.3.1 (2018-03)
1 Scope
De-jitter buffers and echo cancellers have a major effect on voice and data transmission quality in telecommunication
networks. They affect the three service categories of PSTN/ISDN voice, voiceband data (due to PSTN modem and fax
calls), and ISDN circuit mode data. Since the requirements for the settings of de-jitter buffers differ for different
services, the present document describes the activation and mode switching procedures of de-jitter buffers and echo
cancellers, including the requirement for in-band tone activating and other control mechanisms.
It is assumed that the clock accuracy of all elements involved is sufficiently high for application of the present
document.
The scope of the present document is considering de-jitter buffer usage in circuit-to-IP media gateways, such as
residential, access or trunking gateways in context of NGN/IMS.
The notion of circuit relates to a PSTN analog line or an ISDN 1x64 bearer channel.
The current version of the present document contains additional de-Jitter Buffer requirements for the transmission of
V.152, Echo Canceller Tests and de-Jitter Buffer Tests.
The requirements for Echo Cancellers and de-Jitter Buffers in for speech transmission are out of scope in the present
document. These requirements are covered in ETSI ES 202 718 [i.27].
The present document is:
a) applicable:
a1) to circuit-to-IP media gateways and communication services with a gateway interworking function
operating at the level of a synchronous byte-stream, such as:
service "voice-over-IP" (VoIP) without or with silence suppression;
service "voiceband data-over-IP" (VBDoIP); and
service "circuit-mode data-over-IP" (CMDoIP);
a2) to IP-to-IP media gateways for dedicated interworking services between two IP domains, such as:
service "IPDV reduction between two IP domains" with different Grade of Service (GoS) as e.g.
described in Recommendation ITU-T G.799.3 [i.22];
service "RTP IPDV reduction between two RTP domains", which may be subject of an "RTP
transport translator" topology (see IETF RFC 5117 [i.23] and Recommendation
ITU-T H.248.88 [i.24]);
but IP-to-IP media gateways are basically out of scope of the present document due to its focus on circuit-to-IP
gateway types;
and is:
b) not applicable, because de-jitter buffers are not required:
b1) to circuit-to-IP media gateways and communication services with a gateway interworking function
operating at the level of individual packets as atomic units (i.e. an asynchronous packet-stream), such as:
service "facsimile-over-IP" (FoIP) according to [i.7];
service "text-over-IP" (ToIP) according to [i.25]; and
service "data-over-IP" (MoIP) according to [i.26];
b2) to IP-to-IP media gateways in general.
Additionally the present document contains Transmission Requirements for Media Gateways (MGWs) with respect to
voiceband data (VBD) and 64 kbit/s transparent data service.
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7 ETSI TS 102 929 V2.3.1 (2018-03)
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] Recommendation ITU-T V.8 (11/2000): "Procedures for starting sessions of data transmission
over the public switched telephone network".
[2] Recommendation ITU-T V.8bis (11/2000): "Procedures for the identification and selection of
common modes of operation between data circuit-terminating equipments (DCEs) and between
data terminal equipments (DTEs) over the public switched telephone network and on leased point
to-point telephone-type circuits".
[3] Recommendation ITU-T G.168: "Digital network echo cancellers".
[4] Recommendation ITU-T V.21 (1988): "300 bits per second duplex modem standardized for use in
the general switched telephone network".
[5] Recommendation ITU-T V.22 (1988): "1200 bits per second duplex modem standardized for use
in the general switched telephone network and on point-to-point 2-wire leased telephone-type
circuits".
[6] Recommendation ITU-T V.25 (1996): "Automatic answering equipment and general procedures
for automatic calling equipment on the general switched telephone network including procedures
for disabling of echo control devices for both manually and automatically established calls".
[7] Recommendation ITU-T V.32 (1993): "A family of 2-wire, duplex modems operating at data
signalling rates of up to 9600 bit/s for use on the general switched telephone network and on
leased telephone-type circuits".
[8] Recommendation ITU-T V.32bis (1991): "A duplex modem operating at data signalling rates of up
to 14 400 bit/s for use on the general switched telephone network and on leased point-to-point
2-wire telephone-type circuits".
[9] Recommendation ITU-T V.152 (2010): "Procedures for supporting voiceband data over IP
Networks".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T G.164: "Echo Suppressors".
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8 ETSI TS 102 929 V2.3.1 (2018-03)
[i.2] Recommendation ITU-T G.165: "Echo Cancellers".
[i.3] Recommendation ITU-T V.2 (1988): "Power levels for data transmission over telephone lines".
[i.4] Void.
[i.5] Recommendation ITU-T G.131 (1996): "Control of talker echo".
[i.6] Recommendation ITU-T Q.115.1 (1999): "Logic for the control of echo control
devices/functions".
[i.7] Recommendation ITU-T T.38 (2010): "Procedures for real-time Group 3 facsimile communication
over IP networks".
[i.8] Introduction to V.34 High-Speed Fax.
NOTE: Available at: http://www.gaoresearch.com/V34Fax/V34Fax.php.
[i.9] Recommendation ITU-T V.34 (1998): "A modem operating at data signalling rates of up to
33 600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire
telephone-type circuits".
[i.10] Recommendation ITU-T T.30: "Procedures for document facsimile transmission in the general
switched telephone network".
[i.11] Recommendation ITU-T V.150.1: "Modem-over-IP networks: Procedures for the end-to-end
connection of V-series DCEs".
[i.12] Recommendation ITU-T V.18: "Procedures for starting sessions of data transmission over the
public switched telephone network".
[i.13] Recommendation ITU-T G.711: "Pulse code modulation (PCM) of voice frequencies".
[i.14] Recommendation ITU-T G.1020 (11/2003): "Performance parameter definitions for quality of
speech and other voiceband applications utilizing IP networks".
[i.15] Recommendation ITU-T T.4: "Standardization of Group 3 facsimile terminals for document
transmission".
[i.16] Recommendation ITU-T T.6: "Facsimile coding schemes and coding control functions for Group 4
facsimile apparatus".
[i.17] ETSI TR 183 072 (V3.1.1):"Telecommunications and Internet converged Services and Protocols
for Advanced Networking (TISPAN); Emulation Services for PSTN Modem Calls".
[i.18] Recommendation G.161.1: "Do-no-harm testing".
[i.19] Recommendation ITU-T I.231.1: "Circuit-mode bearer service categories : Circuit-mode 64 kbit/s
unrestricted, 8 kHz structured bearer service".
[i.20] IETF RFC 4040: "RTP Payload Format for a 64 kbit/s Transparent Call".
[i.21] Recommendation ITU-T Q.931: "ISDN user-network interface layer 3 specification for basic call
control".
[i.22] Recommendation ITU-T G.799.3: "Signal processing functionality and performance of an IP-to-IP
voice gateway optimised for the transport of voice and voiceband data".
[i.23] IETF RFC 5117: "RTP Topologies".
[i.24] Recommendation ITU-T H.248.88: "Gateway control protocol: RTP topology dependent RTCP
handling by ITU-T H.248 media gateways with IP terminations".
[i.25] Recommendation ITU-T V.151: "Procedures for the end-to-end connection of analogue PSTN text
telephones over an IP network utilizing text relay".
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[i.26] Recommendation ITU-T V.150.1: "Modem-over-IP networks: Procedures for the end-to-end
connection of V-series DCEs".
[i.27] ETSI ES 202 718: "Speech and multimedia Transmission Quality (STQ); Transmission
Requirements for IP-based Narrowband and Wideband Home Gateways and Other Media
Gateways from a QoS Perspective as Perceived by the User".
[i.28] Recommendation ITU-T P.501: "Test signals for use in telephonometry".
[i.29] Recommendation ITU-T G.826: "End-to-end error performance parameters and objectives for
international, constant bit-rate digital paths and connections".
[i.30] Recommendation ITU-T V.17 (02/1991): "A 2-wire modem for facsimile applications with rates
up to 14 400 bit/s".
[i.31] Recommendation ITU-T V.27 (11/1988): "4800 bits per second modem with manual equalizer
standardized for use on leased telephone-type circuits".
[i.32] Recommendation ITU-T V.29 (11/1988): "9600 bits per second modem standardized for use on
point-to-point 4-wire leased telephone-type circuits".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
acoustic echo: acoustic echoes consist of reflected signals caused by acoustic environments
NOTE: In these acoustic environments, an echo path is introduced by the acoustic path from the loudspeaker or
earpiece to the microphone, e.g. echo created from hands-free speakerphones [3].
de-jitter buffer [i.14]: buffer designed to remove the delay variation (i.e. jitter) in packet arrival times
NOTE: Data is put into the de-jitter buffer at a variable rate (i.e. whenever they are received from the network),
and taken out at a constant rate.
Echo Canceller (EC): voice-operated device placed in the 4-wire portion of a circuit and used for reducing the
cancelled end echo present on the send path by subtracting an estimation of that echo from the cancelled end echo [3]
G3 facsimile equipment (G3FE) [i.7]: G3FE refers to any entity which presents a communications interface
conforming to Recommendation ITU-T T.30 [i.10], Recommendation ITU-T T.4 [i.15] and optionally Recommendation
ITU-T T.6 [i.16]
NOTE: A G3FE may be a traditional G3 facsimile machine, an application with a Recommendation
ITU-T T.30 [i.10] protocol engine, or any of the other possibilities mentioned in the network model for IP
facsimile.
Non-Linear Processor (NLP): device having a defined suppression threshold level and in which:
a) signals having a level detected as being below the threshold are suppressed; and
b) signals having a level detected as being above the threshold are passed although the signal may be distorted.
NOTE: The present document assumes an echo canceller is equipped with an NLP function that can be enabled or
disabled when performing the tests defined in the present document. An NLP function can be enabled or
disabled by the user (for the purpose of performing a particular test), or may also be disabled upon
detection of an appropriate disabling tone (e.g. 2 100 Hz) [3].
pseudo-VBDoIP emulation service: XoIP emulation service, trying to support voiceband data in audio mode (see
clause 3.2.1 of Recommendation ITU-T V.152 [9]), also known as non-V.152 VBDoIP service
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10 ETSI TS 102 929 V2.3.1 (2018-03)
PSTN modem call [i.17]: voiceband data call originating/terminating in a PSTN domain
NOTE: The term voiceband data (VBD) is an umbrella term for all kind of teleservices which using a "data-
oriented transport" in the frequency band of the narrowband voice spectrum (which is a 3,1-kHz-band).
The data-oriented transport is realized by modem protocols (definition as in clause 3.13 of
Recommendation ITU-T V.152 [9]), as defined e.g. within the Recommendations ITU-T V.x-series.
Teleservices may be categorized into three major applications areas: facsimile, text-based communication
and general data services.
T.38/G3 [i.7]: Recommendation ITU-T T.38/G3 refers to an ITU-T T.38 endpoint that supports G3FE, but excludes the
Recommendation ITU-T T.30/V.34 procedures.
T.38/V.34G3 [i.7]: Recommendation ITU-T T.38/G3 refers to an ITU-T T.38 endpoint that supports G3FE and
includes the Recommendation ITU-T T.30/V.34 half-duplex procedures.
VBD gateway [9]: media gateway that is compliant with Recommendation ITU-T V.152 [9]
VBDoIP emulation service: XoIP emulation service compliant to Recommendation ITU-T V.152 [9]
voiceband data mode [9]: transport of voiceband data over a voice channel of a packet network with the encoding
appropriate for modem signals as defined in section 6 of Recommendation ITU-T V.152 [9]
XoIP emulation service (for PSTN modem calls) [i.17]: emulation service in IP networks, based on appropriated
gateway technologies for interworking voiceband data information between the PSTN and IP networks
NOTE: Example emulation services for the three main VBD application areas, which may be summarized as (by
using notation "application/transport"):
Facsimile/modem: Gateway technologies for PSTN-to-IP interworking see e.g. Recommendation
ITU-T V.152 [9] for pass-through mode and Recommendation ITU-T T.38 [i.7] as packet-relay
mode;
Text/modem: Gateway technologies for PSTN-to-IP interworking see e.g. Recommendation ITU-T
V.152 [9] for pass-through mode and Recommendation ITU-T V.151 [i.25] as packet-relay mode;
and
Data/modem: Gateway technologies for PSTN-to-IP interworking see e.g. Recommendation ITU-T
V.152 [9] for pass-through mode and Recommendation ITU-T V.150.1 [i.11] as packet-relay mode.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ANM Answer Message
ANS Answer Tone
ATA Analog Terminal Adapter
CED Called station identification tone
CM Call Menu signal
CM/JM Call Menu signal/Joint Menu signal
CMD Circuit-Mode Data
CNG Calling Tone
CSS Composite Source Signal
CT Calling Tone
DCE Data Communication Equipment
DJB De Jitter Buffer
DTMF Dual-Tone Multi-Frequency signalling
EC Echo Canceller
ECM Error Correction Mode
ERL Echo Return Loss
ERLE Echo Return Loss Enhancement
GSTN General Switched Telephone Network
IAD Integrated Access Device
IP Internet Protocol
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11 ETSI TS 102 929 V2.3.1 (2018-03)
IPDV IP Delay Variation
ISDN Integrated Services Digital Network
ISUP ISDN User Part
ITU-T International Telecommunication Union - Telecommunication Standardization Sector
JB de-Jitter Buffer
JBD de-Jitter Buffer Delay
JBS de-Jitter Buffer Size
JM Joint Menu signal
MGC Media Gateway Controller
MGW Media Gateway
MSAN Multi Service Access Nodes
NGN New Generation Network
NLP Non-Linear Processor
NNI Network Network Interface
PCM Pulse Code Modulation
PLC Packet Loss Concealment
PSTN Public Switched Telephone Network
QAM Quadrature Amplitude Modulation
RCV Received
RTP Real Time Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
SSND Signal - Send
TDM Time Division Multiplexing
UDI Unrestricted Digital Information
UNI User Network Interface
VBD VoiceBand Data
4 Characteristics of de-jitter buffers
4.1 De-Jitter buffers
The present document describes the activation procedures of a de-jitter buffer, including the requirement for in-band
tone activating and other control mechanisms. The de-jitter buffers are assumed to be dynamic de-jitter buffers and
fixed de-jitter buffers. Fixed de-jitter buffers shall be provided for fax and voiceband data and 64 kbit/s bit sequence
(UDI).
A de-jitter buffer is designed to remove the effects of jitter from the decoded voice stream, buffering each arriving
packet for a short interval before playing it out synchronously. A fixed de-jitter buffer maintains a constant size
whereas an adaptive de-jitter buffer has the capability of adjusting its size dynamically in order to optimize the
delay/discard trade-off. The disadvantage of adaptive de-jitter buffer is that a part of the jitter budget is transferred to
the user. While the human perception of audio delay variation is low, modem and fax applications are extremely
sensitive to delay variation in the audio path. For this reason adaptive de-jitter buffer are not applicable for fax and
modem transmission. Fixed de-jitter buffers try to maintain a constant End-to-End audio delay.
Jitter Buffer Size
Packets, irregulary arriving
Steady voice flow
from the network
Excess Buffer Jitter Buffer Delay

Figure 1: De-jitter buffer Size and Delay
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12 ETSI TS 102 929 V2.3.1 (2018-03)
De-jitter buffer Size (JBS): The maximum amount of time packets can stay in the buffer.
De-jitter buffer Delay (JBD): The de-jitter buffer delay is also called de-jitter delay, holding time or play-out delay. It
corresponds to the time packets stay in the buffer, which is less than the de-jitter buffer size. The time of departure of
each packet is determined by reading out the timestamp information provided by RTP.
4.2 Purpose, operation and environment
For proper operation for VBD-services, De-jitter buffers have the following fundamental requirements:
1) fast and correct switching between dynamic and fix de-jitter buffer mode;
2) proper operation during facsimile and data transmissions.
For proper operation of speech services in good quality, false detection of tones (e.g. from answering machines, call
centres or speech) has to be minimized.
NOTE: It may be necessary to make a balancing between quality requirements of VBD and speech services.
4.3 External enabling of fixed de-jitter buffers
The fixed de-jitter buffer for 64 kbit/s bit sequence (UDI) and V.152 VBD shall be activated directly by signalization.
5 Characteristics of VBD-mode switching of de-jitter
buffers
5.1 General
The de-jitter buffer covered by the present document should be equipped with a tone detector that conforms to this
clause.
• The change of the de-jitter buffer to VBD-mode should be based on the following signals (mostly taken out of
Recommendation ITU-T V.152 [9]) For Facsimile applications:
- CED as per Recommendation ITU-T T.30 [i.10]
- ANSam as per Recommendation ITU-T V.8 [1]
- Preamble as per Recommendation ITU-T T.30 [i.10], section 5.3.1
- CNG as per Recommendation ITU-T T.30 [i.10]
• For Modem applications:
- ANS as per Recommendation ITU-T V.8 [1]
- ANSam as per Recommendation ITU-T V.8 [1]
- /ANS as per Recommendation ITU-T V.25 [6]
- 2 225 Hz answer tone as per Recommendation ITU-T V.150.1 [i.11], appendix VI
- Unscrambled binary ones signal as per Recommendation ITU-T V.22 [5]
- CI signals that precede ANSam, as per Recommendations ITU-T V.8 [1] and V.21 [4]
- Dual-frequency tones (1 375 Hz + 2 002 Hz and 1 529 Hz + 2 225 Hz) as per Recommendation
ITU-T V.8bis [2]
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13 ETSI TS 102 929 V2.3.1 (2018-03)
• For Text Telephony applications:
- ANS as per Recommendation ITU-T V.8 [1]
- ANSam as per Recommendation ITU-T V.8 [1]
- Text telephone signals as defined by Recommendation ITU-T V.18 [i.12], section 5.1.1
- CI signals that precede ANSam, as per Recommendation ITU-T V.8 [1]
- CT (Calling Tone) signals that precede ANS, as per Recommendation ITU-T V.25 [6]
- Initiating Segment 1 dual tones (1 375 Hz & 2 002 Hz) as per Recommendation ITU-T V.8bis [2]
5.2 Detector characteristics
5.2.1 Detector characteristics for frequency range of 2 100 Hz ± 21 Hz
The tone detector shall detect a tone in the frequency range of 2 100 Hz ± 21 Hz (see Recommendation
ITU-T V.21 [4]). The detection channel bandwidth should be chosen wide enough to encompass this tone (and possibly
other tones used within national networks). At the same time, the detection channel bandwidth should be such that, in
conjunction with guard action and timing, adequate protection is provided against false operation of the detector by
speech signals. The detector channel sensitivity (threshold level) should be such that the detector will operate on the
lowest expected power of the tone. The band characteristics shown in figure 2 will permit changing the de-jitter buffer
behaviour by the 2 100 Hz tone as well as others used in North America. The figure indicates that in the frequency band
2 079 Hz to 2 121 Hz detection shall be possible whilst in the band 1 900 Hz to 2 350 Hz detection may be possible.
Providing that only the recommended 2 100 Hz tone is used internationally, interference with signalling equipment will
be avoided. The dynamic range of the detector should be consistent with the input levels as specified in
Recommendation ITU-T V.2 [i.3] with allowances for variation introduced by the public switched telephone network.

Figure 2: Required band characteristics
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14 ETSI TS 102 929 V2.3.1 (2018-03)
5.2.2 Detector characteristics for dual-frequency tones 1 375 Hz +
2 002 Hz and 1 529 Hz + 2 225 Hz (Recommendation ITU-T V.8bis)
The tone detector shall detect two tone segments. The first segment consists of a dual-frequency tone held for 400 ms.
The specific frequencies 1 375 Hz + 2 002 Hz are used from the initiator, the specific frequencies
1 529 Hz + 2 225 Hz from the responder in a transaction. When using the telephone-event payload, the V8bISeg and
V8bRSeg events in table 1 represent the first segment of any V.8bis signal in the initiating and responding case,
respectively.
Table 1: Events for V.8bis signals
Signal Frequency
V8bISeg 1 375 Hz + 2 002 Hz
V8bRSeg 1 529 Hz + 2 225 Hz
The tolerance of the frequency of all tones shall be ±250 ppm of the nominal value.
The tolerance of the duration of the tone segments shall be ±2 %.
The detection channel bandwidth should be chosen wide enough to encompass this tones (and possibly other tones used
within national networks). At the same time, the detection channel bandwidth should be such that, in conjunction with
guard action and timing, adequate protection is provided against false operation of the detector by speech signals. The
detector channel sensitivity (threshold level) should be such that the detector will operate on the lowest expected power
of the tone.
5.2.3 Detector characteristics for frequencies 980 Hz, 1 180 Hz, 1 650 Hz
and 1 850 Hz (V.21)
The tone detector shall detect the frequencies 980 Hz for '1' (mark) and 1 180 Hz for '0' (space) (low channel uses) and
the frequencies 1 650 Hz for '1' and 1 850 Hz for '0' (high channel uses). The frequency deviation is ±100 Hz.
The detection channel bandwidth should be chosen wide enough to encompass this tones (and possibly other tones used
within national networks). At the same time, the detection channel bandwidth should be such that, in conjunction with
guard action and timing, adequate protection is provided against false operation of the detector by speech signals. The
detector channel sensitivity (threshold level) should be such that the detector will operate on the lowest expected power
of the tone.
Table 2: Events for V.21 Signals
Signal Frequency (Hz)
V.21 channel 1,
1 180
'0' bit
V.21 channel 1,
'1' bit
V.21 channel 2,
1 850
'0' bit
V.21 channel 2,
1 650
'1' bit
5.2.4 Detector characteristics for 2 100 Hz amplitude-modulated by a
sinewave at 15 Hz, 2 100 Hz amplitude-modulated by a sinewave at
15 Hz with phase reversals, 1 300 Hz and 1 100 Hz (V.8)
To activate the De-jitter buffer at calling end respectively called end for procedures according to Recommendation
ITU-T V.8 [1], the tone detector shall detect frequencies described in table 3.
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15 ETSI TS 102 929 V2.3.1 (2018-03)
Tab
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