1、 International Telecommunication Union ITU-T G.169TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2011) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS International telephone connections and circuits Apparatus associated with long-distance telephone circuitsAutomatic leve
2、l control devices Recommendation ITU-T G.169 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 Transmission planning and the E-model G.100G.109 General Recommendations on the transmission quality fo
3、r an entire international telephone connection G.110G.119 General characteristics of national systems forming part of international connections G.120G.129 General characteristics of the 4-wire chain formed by the international circuits and national extension circuits G.130G.139 General characteristi
4、cs of the 4-wire chain of international circuits; international transit G.140G.149 General characteristics of international telephone circuits and national extension circuits G.150G.159 Apparatus associated with long-distance telephone circuits G.160G.169Transmission plan aspects of special circuits
5、 and connections using the international telephone connection network G.170G.179 Protection and restoration of transmission systems G.180G.189 Software tools for transmission systems G.190G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTE
6、RISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMI
7、SSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERIS
8、TICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T G.169 (05/2011) i Recommendation ITU-T G.169 Automatic level control devices S
9、ummary Recommendation ITU-T G.169 applies to the testing of automatic level control (ALC) devices intended for use in digital network-based equipment. It does not apply to subscriber-based level control devices, devices that operate in the analogue domain, or any means of fixed level control within
10、the network which may be part of an overall network transmission plan. The scope of this Recommendation is to define certain performance constraints for network ALC devices and, where appropriate, to define laboratory tests that may be performed on an ALC device to verify that these constraints are
11、met. An ALC device that satisfies all the constraints and passes all of the tests in this Recommendation should ensure (but will not guarantee) that the pre-existing standard of overall network performance (e.g., the transmission of speech, voiceband data and other voiceband signals, ISDN, etc.) is
12、not degraded when the ALC device is installed in the network. This Recommendation also describes the general characteristics of ALC devices and indicates what characteristics are important to provide acceptable performance in the network. Issues relating to the interaction of ALC devices with other
13、network and subscriber equipment are also discussed in this Recommendation. This Recommendation does not define a standard algorithm. This Recommendation does not define planning rules, deployment aspects, or target levels for ALC devices. History Edition Recommendation Approval Study Group 1.0 ITU-
14、T G.169 1999-07-02 15 2.0 ITU-T G.169 2011-05-14 16 ii Rec. ITU-T G.169 (05/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standar
15、dization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), whic
16、h meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within IT
17、U-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendatio
18、n is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “mu
19、st“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation m
20、ay involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of th
21、is Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent databas
22、e at http:/www.itu.int/ITU-T/ipr/. ITU 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T G.169 (05/2011) iii Table of Contents Page 1 Scope 1 2 References. 1 3 Terms and definitions . 2 4 Abbrevia
23、tions and acronyms 3 5 Characteristics of ALC devices 4 5.1 General . 4 5.2 ALC characteristics 4 5.3 Tandemed operation . 4 5.4 Delay performance . 4 6 Test signals . 5 6.1 Test signal for level and gain checks 5 6.2 Electrical circuit noise 5 6.3 Environmental noise . 5 7 Tests 6 7.1 Stability . 6
24、 7.2 Echo 8 7.3 Noise tolerance . 11 7.4 Signalling tones 13 7.5 Voiceband data and facsimile transmission . 16 7.6 Test to verify the ability of an ALC to estimate the signal level correctly 20 7.7 Test to verify the ability of an ALC to operate on short speech utterances (under study) . 21 Annex A
25、 Guidance for measuring signal levels in networks 22 Appendix I Guidance for the design of automatic level control (ALC) algorithms and their placement in the public switched telephone network (PSTN) . 24 I.1 Introduction 24 I.2 Discussion . 24 I.3 ALC considerations 25 Appendix II Considerations re
26、lating to ALC deployment 28 II.1 Location of ALC . 28 II.2 Tandemed operation . 29 Bibliography. 30 Rec. ITU-T G.169 (05/2011) 1 Recommendation ITU-T G.169 Automatic level control devices 1 Scope This Recommendation applies to the testing of automatic level control (ALC) devices intended for use in
27、digital network-based equipment. An ALC device is defined as any signal processing function located in the digital transmission path which automatically adjusts the level of a signal towards a predetermined value. Devices which modify the frequency response or spectral content of the signal in such
28、a way as to affect the overall level of the signal are also defined as ALC devices for the purpose of this Recommendation. This Recommendation does not apply to subscriber-based level control devices, devices that operate in the analogue domain, or any means of fixed level control within the network
29、 which may be part of an overall network transmission plan. The scope of this Recommendation is to define certain performance constraints for network ALC devices and, where appropriate, to define laboratory tests that may be performed on an ALC device to verify that these constraints are met. An ALC
30、 device that satisfies all the constraints and passes all of the tests in this Recommendation should ensure (but will not guarantee) that the pre-existing standard of overall network performance (e.g., the transmission of speech, voiceband data and other voiceband signals, ISDN, etc.) is not degrade
31、d when the ALC device is installed in the network. This Recommendation also describes the general characteristics of ALC devices and indicates what characteristics are important to provide acceptable performance in the network. Issues relating to the interaction of ALC devices with other network and
32、 subscriber equipment are also discussed in this Recommendation. This Recommendation does not define a standard algorithm. This Recommendation does not define planning rules, deployment aspects, or target levels for ALC devices. This information may be found in ITU-T G.136. 2 References The followin
33、g ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommen
34、dation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not giv
35、e it, as a stand-alone document, the status of a Recommendation. ITU-T G.115 Recommendation ITU-T G.115 (1996), Mean active speech level for announcement and speech synthesis systems. ITU-T G.121 Recommendation ITU-T G.121 (1993), Loudness ratings (LRs) of national systems. ITU-T G.122 Recommendatio
36、n ITU-T G.122 (1993), Influence of national systems on stability and talker echo in international connections. ITU-T G.136 Recommendation ITU-T G.136 (1999), Application rules for automatic level control devices. 2 Rec. ITU-T G.169 (05/2011) ITU-T G.160 Recommendation ITU-T G.160 (2008), Voice enhan
37、cement devices. ITU-T G.164 Recommendation ITU-T G.164 (1988), Echo suppressors. ITU-T G.165 Recommendation ITU-T G.165 (1993), Echo cancellers. ITU-T G.168 Recommendation ITU-T G.168 (2009), Digital network echo cancellers. ITU-T G.763 Recommendation ITU-T G.763 (1998), Digital circuit multiplicati
38、on equipment using G.726 ADPCM and digital speech interpolation. ITU-T P.56 Recommendation ITU-T P.56 (1993), Objective measurement of active speech level. ITU-T P.501 Recommendation ITU-T P.501 (2007), Test signals for use in telephonometry. ITU-T P.561 Recommendation ITU-T P.561 (2002), In-service
39、 non-intrusive measurement device Voice service measurements. ITU-T Q.24 Recommendation ITU-T Q.24 (1988), Multifrequency push-button signal reception. ITU-T T.4 Recommendation ITU-T T.4 (2003), Standardization of Group 3 facsimile terminals for document transmission. ITU-T T.30 Recommendation ITU-T
40、 T.30 (2005), Procedures for document facsimile transmission in the general switched telephone network. ITU-T V.8 Recommendation ITU-T V.8 (2000), Procedures for starting sessions of data transmission over the public switched telephone network. ITU-T V.25 Recommendation ITU-T V.25 (1996), Automatic
41、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. 3 Terms and definitions This Recommendation defines the following ter
42、ms: 3.1 ALC device: A signal processing function located in the digital transmission path which automatically adjusts the level of a signal towards a predetermined value. Devices which modify the frequency response or spectral content of the signal in such a way as to affect the overall level of the
43、 signal are also defined as ALC devices for the purpose of this Recommendation. An ALC device is designed to process signals in one direction of transmission. See Figure 1. Rec. ITU-T G.169 (05/2011) 3 T1530230-98RinRoutSoutSinReceive or non-processing pathALC DeviceReceive inReceive outALCProcessin
44、gSend or processing pathSend out Send inFigure 1 Block diagram of an ALC device 3.2 disabled ALC device: An ALC device that has been forced into a 64 kbit/s bit-sequence integrity mode of operation, by whatever means. 3.3 echo canceller: A device placed in the 4-wire portion of a circuit and used fo
45、r reducing cancelled-end echo present on the send path by subtracting an estimation of that echo from the cancelled-end echo. 3.4 full ALC device: An ALC device designed to process signals in both directions of transmission. 3.5 full echo canceller: An echo canceller designed to cancel echoes in bot
46、h directions (i.e., near-end and far-end echoes). 3.6 laboratory tests: Tests which may be performed in a laboratory or any environment where the ALC device is not installed in the network and is therefore not in service. 3.7 Target level: For a particular signal type, the input signal level for whi
47、ch an active (enabled) ALC device will progress to unity gain. At other input signal levels, the output level of the ALC device will be adjusted towards the target level. NOTE With some ALC devices, the target level may be different for different types of signals, e.g., the target level for speech m
48、ay be different from the target level for a tone. Also, the treatment of signals which are above the target level may be different from the treatment of signals which are below the target level. In principle, an advanced ALC device may feature more than one target level, depending on the transmitted
49、 signal (e.g., speech, data, or DTMF tones). 4 Abbreviations and acronyms This Recommendation uses the following abbreviations: ALC Automatic Level Control A/D Analogue-to-Digital converter CSS Composite Source Signal D/A Digital-to-Analogue converter DCME Digital Circuit Multiplication Equipment DTMF Dual-Tone Multi-Frequency ERL Echo Return Loss ISDN Integrated Services Digital Network 4 Rec. ITU-T G.169 (05/2011) PSTN Public Switched Telephone Network 5 Characteristics of ALC devices 5.1 Gener
