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ITU-T G.168 (08/2004)

Annuleurs d'écho pour les réseaux numériques

L'écho exerce une grande influence sur la qualité de la voix dans les réseaux de télécommunication. Son effet désagréable est dû aux réflexions par les composants de réseau tels que les convertisseurs de deux à quatre fils, qui s'ajoutent au traitement du signal et au temps de transmission. L'écho peut rendre difficile la parole ou l'écoute des usagers en communication téléphonique. Il peut aussi affecter la transmission des données, de la télécopie et de la textophonie dans la bande des fréquences vocales.
Les annuleurs d'écho de réseau numérique sont conçus pour supprimer l'écho perçu par l'usager et pour assurer une transmission correcte des données et de la télécopie dans la bande des fréquences vocales. La présente Recommandation décrit les caractéristiques d'un annuleur d'écho, y compris les spécifications relatives à l'annulation par tonalité dans la bande et à d'autres mécanismes de commande. Elle décrit aussi un certain nombre d'essais en laboratoire que l'annuleur d'écho devrait subir afin que soit évaluée sa performance dans des conditions susceptibles de se produire dans le réseau.
La présente version de la Rec. UIT-T G.168 est une révision de la version précédente publiée en juin 2002. Toutes les ambiguïtés et les erreurs contenues dans cette version précédente ont été supprimées. Un essai de reconvergence a été ajouté dans l'essai 2 et une spécification a été définie pour la partie c) de l'essai 2C. Des précisions ont été apportées concernant la définition du "temps de convergence", car ce terme est souvent mal utilisé dans la littérature relative aux annuleurs d'écho. L'essai 3 (parole simultanée) a été modifié afin d'examiner à la fois la convergence et la stabilité en période de parole simultanée et de nouvelles spécifications ont été ajoutées dans l'essai 3B. Un nouvel Appendice IV contient quelques lignes directrices concernant l'utilisation de paramètres par tous ceux qui procèderont à des essais d'annuleur d'écho conformément à la présente Recommandation. Certains essais restent à l'étude, à savoir l'essai 10C (télécopie), l'essai 11 (annuleurs d'écho en cascade), l'essai 12 (écho acoustique résiduel) et l'essai 13 (codeurs à bas débit). Il est prévu que ces essais soient définis dans une future révision de la présente Recommandation.

Citation:	https://handle.itu.int/11.1002/1000/7318
Series title:	G series: Transmission systems and media, digital systems and networks G.100-G.199: International telephone connections and circuits G.160-G.169: Apparatus associated with long-distance telephone circuits
Approval date:	2004-08-06
Provisional name:	G.iec
Approval process:	AAP
Status:	Superseded
Maintenance responsibility:	ITU-T Study Group 21
Further details:	Patent statement(s) Development history

Ed.	ITU-T Recommendation	Status	Summary	Table of Contents	Download
8.1	G.168 (2015) Cor. 1 (12/2022)	In force	here	here	here
8	G.168 (04/2015)	In force	here	here	here
7.1	G.168 (2012) Amd. 1 (05/2012)	Superseded	here	here	here
7.0	G.168 (2012) Err. 1 (11/2012)	Superseded	-	-	here
7	G.168 (02/2012)	Superseded	here	here	here
6	G.168 (03/2009)	Superseded	here	here	here
5	G.168 (01/2007)	Superseded	here	here	here
4	G.168 (08/2004)	Superseded	here	here	here
3	G.168 (06/2002)	Superseded	here	here	here
2	G.168 (04/2000)	Superseded	here	here	here
1	G.168 (04/1997)	Superseded	-	-	here


ITU-T Supplement	Title	Status	Summary	Table of contents	Download
G-100 series Suppl. 31 (03/1993)	Principles of determining an impedance strategy for the local network	In force	-	here	here
G-100 series Suppl. 32 (03/1993)	Transmission aspects of digital mobile radio systems	In force	-	here	here
G Suppl. 4 (12/1972)	Certain methods of avoiding the transmission of excessive noise between interconnected systems	In force	-	-	here
G Suppl. 5 (10/1984)	Measurement of the load of telephone circuits under field conditions	In force	-	-	here
G Suppl. 7 (12/1972)	Loss-frequency response of channel-translating equipment used in some countries for international circuits	In force	here	here	here
G Suppl. 8 (12/1972)	Method proposed by the Belgian telephone administration for interconnection between coaxial and symmetric pair systems	In force	-	-	here
G Suppl. 17 (10/1984)	Group-delay distortion performance of terminal equipment	In force	-	-	here
G Suppl. 19 (10/1984)	Digital crosstalk measurement (method used by the Administrations of France, the Netherlands and Spain)	In force	-	-	here
G Suppl. 22 (10/1984)	Mathematical models of multiplex signals	In force	-	-	here
G Suppl. 26 (10/1984)	Estimating the signal load margin of FDM wideband amplifier equipment and transmission systems	In force	-	-	here
G Suppl. 27 (10/1984)	Interference from external sources	In force	-	-	here
G Suppl. 28 (10/1984)	Application of transmultiplexers, FDM codecs, data-in-voice (DIV) systems and data-over-voice (DOV) systems during the transition from an analogue to a digital network	In force	-	-	here
G Suppl. 32 (11/1988)	Transfer of alarm information on 60-channel transmultiplexing equipment	In force	-	-	here
G Suppl. 34 (11/1988)	Temperature in underground containers for the installation of repeaters	In force	-	-	here
G Suppl. 35 (11/1988)	Guidelines concerning the measurement of wander	In force	-	-	here
G Suppl. 36 (11/1988)	Jitter and wander accumulation in digital networks	In force	-	-	here
G Suppl. 39 (03/2025)	Optical system design and engineering considerations	In force	here	here	here
G Suppl. 40 (07/2024)	Optical fibre and cable Recommendations and standards guideline	In force	here	here	here
G Suppl. 41 (07/2024)	Design guidelines for optical fibre submarine cable systems	In force	here	here	here
G Suppl. 42 (10/2018)	Guide on the use of the ITU-T Recommendations related to optical fibres and systems technology	In force	here	here	here
G Suppl. 43 (02/2011)	Transport of IEEE 10GBASE-R in optical transport networks (OTN)	In force	here	here	here
G Suppl. 44 (06/2007)	Test plan to verify B-PON interoperability	In force	here	here	here
G Suppl. 45 (09/2022)	Power conservation in optical access systems	In force	here	here	here
G Suppl. 46 (05/2009)	G-PON interoperability test plan between optical line terminations and optical network units	In force	here	here	here
G Suppl. 47 (03/2025)	General aspects of optical fibres and cables	In force	here	here	here
G Suppl. 48 (06/2010)	10-Gigabit-capable passive optical networks: Interface between media access control with serializer/deserializer and physical medium dependent sublayers	In force	here	here	here
G Suppl. 49 (09/2020)	Rogue optical network unit (ONU) considerations	In force	here	here	here
G Suppl. 50 (09/2011)	Overview of digital subscriber line Recommendations	In force	here	here	here
G Suppl. 51 (06/2017)	Passive optical network protection considerations	In force	here	here	here
G Suppl. 52 (09/2012)	Ethernet ring protection switching	In force	here	here	here
G Suppl. 53 (12/2014)	Guidance for Ethernet OAM performance monitoring	In force	here	here	here
G Suppl. 54 (07/2015)	Ethernet linear protection switching	In force	here	here	here
G Suppl. 55 (12/2023)	Radio-over-fibre (RoF) technologies and their applications	In force	here	here	here
G Suppl. 56 (02/2016)	OTN transport of CPRI signals	In force	here	here	here
G Suppl. 57 (07/2015)	Smart home profiles for 6LoWPAN devices	In force	here	here	here
G Suppl. 58 (07/2024)	Optical transport network module framer interfaces	In force	here	here	here
G Suppl. 59 (02/2018)	Guidance on optical fibre and cable reliability	In force	here	here	here
G Suppl. 60 (09/2016)	Ethernet linear protection switching with dual node interconnection	In force	here	here	here
G Suppl. 62 (02/2018)	Gfast certification	In force	here	here	here
G Suppl. 64 (02/2018)	PON transmission technologies above 10 Gb/s per wavelength	In force	here	here	here
G Suppl. 65 (10/2018)	Simulations of transport of time over packet networks	In force	here	here	here
G Suppl. 66 (09/2020)	5G wireless fronthaul requirements in a passive optical network context	In force	here	here	here
G Suppl. 67 (07/2019)	Application of optical transport network Recommendations to 5G transport	In force	here	here	here
G Suppl. 68 (12/2023)	Synchronization operations, administration and maintenance requirements	In force	here	here	here
G Suppl. 69 (09/2020)	Migration of a pre-standard network to a metro transport network	In force	here	here	here
G Suppl. 70 (09/2020)	Supplement on sub 1 Gbit/s services transport over optical transport network	In force	here	here	here
G Suppl. 71 (12/2023)	Optical line termination capabilities for supporting cooperative dynamic bandwidth assignment	In force	here	here	here
G Suppl. 72 (03/2025)	Modelling consideration for optical media networks	In force	here	here	here
G Suppl. 73 (10/2021)	Influencing factors on quality of experience for multiview video (MVV) services	In force	here	here	here
G Suppl. 74 (12/2021)	Network slicing in a passive optical network context	In force	here	here	here
G Suppl. 75 (12/2021)	5G small cell backhaul/midhaul over TDM-PON	In force	here	here	here
G Suppl. 76 (12/2021)	Optical transport network security	In force	here	here	here
G Suppl. 77 (06/2022)	Supplement 77 to ITU-T G-series of Recommendations - Influencing factors on quality of experience (QoE) for video customized alerting tone (CAT) and video customized ringing signal (CRS) services	In force	here	here	here
G Suppl. 78 (09/2022)	Use case and requirements of fibre-to-the-room for small business applications	In force	here	here	here
G Suppl. 79 (12/2023)	Latency control and deterministic capability over a PON system	In force	here	here	here
G Suppl. 80 (07/2024)	Use case and requirements of fibre-based in-premises networking for home application (FIP4H)	In force	here	here	here
G Suppl. 81 (07/2024)	Practical aspects of PON security	In force	here	here	here
G Suppl. 82 (07/2024)	Enhanced optical line termination with information technology functions	In force	here	here	here
G Suppl. 83 (07/2024)	Supplement on the use of options in the precision time protocol profile with full timing support from the network	In force	here	here	here
G Suppl. 84 (03/2025)	Operational aspects of optical access	In force	here	here	here
G Suppl. 85 (03/2025)	FgODUflex over point-to-multipoint networks	In force	here	here	here
G Suppl. 86 (03/2025)	Fibre to the power grid (FTTGrid) use cases and network requirements	In force	here	here	here
G Suppl. 87 (03/2025)	Standardization framework for optical fibres for space division multiplexing	In force	here	here	here
G Suppl. 29 (03/1993)	Planning of mixed analogue-digital circuits (chains, connections)	In force	-	here	here

Title	Approved on	Download
Roadmap for QoS and QoE in the ITU-T Study Group 12 context (TR-RQ)	2023	here
Considerations on the use of GNSS as a primary time reference in telecommunications	2020	here
Use of G.hn in industrial applications	2020	here
The composite source signal as a measuring signal and a summary of various investigations on speech echo cancellers	2010	here
ISDN field trial guidelines	1991	here

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ITU-T Recommendations

ITU-T G.168 (08/2004)