G.168

G.168
Title	G.168
Organization	International Telecommunication Union
Publication	ITU-T Recommendation
Status	Approved
First published	1988
Domain	Telecommunications, Signal Processing

G.168 G.168 is an ITU-T Recommendation specifying echo cancellers for telecommunication networks. It defines algorithmic, performance, and testing requirements for echo cancellation equipment used by British Telecommunications, Deutsche Telekom, Nippon Telegraph and Telephone, AT&T, Verizon Communications, Orange S.A., Telstra, Telefónica, Vodafone Group, China Mobile and other carriers. The Recommendation informs interoperability among vendors such as Siemens, Alcatel-Lucent, Ericsson, Huawei Technologies, Nortel Networks, Cisco Systems, Mitel Networks and Avaya.

Overview

G.168 addresses echo that occurs in analog and hybrid circuits, and in packet-based systems interconnecting with British Telecom's public switched telephone network, MCI Communications infrastructures, and national networks like France Télécom and Deutsche Telekom AG. It sets criteria for echo return loss enhancement and tail processing for devices deployed by operators including T-Mobile, Sprint Corporation, Bell Canada, SK Telecom, Telecom Italia, Rogers Communications, BT Group, and KDDI Corporation. The Recommendation is referenced by regulatory authorities such as the Federal Communications Commission, European Commission, Ofcom, Australian Communications and Media Authority, and standards bodies like ETSI and ANSI.

Technical Specifications

G.168 specifies parameters including convergence time, echo return loss enhancement (ERLE), double-talk performance, and non-linear processing thresholds for implementations by manufacturers such as Lucent Technologies and Rockwell Collins. It defines test signals, measurement methods, and filter structures usable by developers at Bell Labs, Fraunhofer Society, Massachusetts Institute of Technology, Stanford University, University of California, Berkeley, Carnegie Mellon University, Tsinghua University, Indian Institute of Technology, and University of Cambridge. The Recommendation details algorithms that may use adaptive finite impulse response filters, echo path modeling, and residual echo suppression as in products from Hewlett-Packard, Texas Instruments, Analog Devices, Intel Corporation, and Xilinx.

Testing and Certification

Conformance to G.168 is verified through laboratory tests commonly run by test houses like UL Solutions, Intertek, SGS, and TÜV Rheinland. Telecommunications carriers including Verizon Business, CenturyLink, Comcast, Deutsche Telekom Global Carrier, Tata Communications, and Orange Business Services require vendor devices to pass echo performance tests derived from G.168. Certification programs may involve interoperability events sponsored by GSMA, IETF, 3GPP, and IEEE working groups. Governments and agencies such as National Institute of Standards and Technology and European Telecommunications Standards Institute reference G.168 for procurement specifications.

Implementation and Use Cases

G.168 implementations appear in analog-to-digital gateways, voice over IP gateways, media gateways from vendors like Dialogic, Broadcom, Mindspeed Technologies, Genesys, and Asterisk (PBX), and in customer premises equipment sold by Siemens AG, Huawei, Cisco Systems, and Panasonic Corporation. Use cases include international trunking between Level 3 Communications and national carriers, enterprise PBX interconnects at Goldman Sachs trading floors, call centers operated by Concentrix, Teleperformance, and Sitel Group, and emergency service platforms used by Federal Emergency Management Agency. G.168 guidance informs deployment in legacy TDM networks and transitions to packet networks managed by Amazon Web Services, Microsoft Azure, Google Cloud Platform, Facebook (Meta), and service providers such as Orange S.A. and BT Global Services.

History and Revisions

The Recommendation originated in the late 1980s with contributions from national administrations and industry consortia including CCITT, European Conference of Postal and Telecommunications Administrations, ITU, and vendor groups from Nortel, Alcatel, Siemens, and Bell Communications Research. Revisions in the 1990s and 2000s updated test methodologies to address packet loss, jitter, and codec interactions with standards like G.711, G.729, G.723.1, RFC 3550, and echo mitigation techniques studied at Bell Labs Research. Later amendments integrated requirements relevant to VoIP interoperability tested at events organized by Interop, CTIA, and ETSI TISPAN.

Regulatory and Standards Context

G.168 is referenced in regulatory frameworks and procurement rules of national regulators such as Ofcom, FCC, TRAI, ARCEP, BNetzA, and ACMA and aligns with complementary ITU-T Recommendations and IETF RFCs including G.711, G.722, RFC 2833, RFC 3389, and RFC 3261. It interacts with standards from IEEE 802.3 for Ethernet transport, IETF SIP work for signaling, and with multimedia profiles developed by 3GPP for mobile voice services. International carriers, vendors, and research institutions continue to use G.168 as a baseline for echo control in interoperability testing and regulatory compliance.

Category:ITU-T recommendations