1、 ETSI EG 202 086 V2.0.0 (2008-07)ETSI Guide Speech Processing, Transmission and Quality Aspects (STQ);Objectives and principles for the transmission performance ofmultiple interconnected networks that aim to provide“traditional quality“ telephony servicesETSI ETSI EG 202 086 V2.0.0 (2008-07) 2 Refer
2、ence REG/STQ-00126 Keywords interworking, QoS, quality, speech, telephony, transmission ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16 Siret N 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-Prfecture d
3、e Grasse (06) N 7803/88 Important notice Individual copies of the present document can be downloaded from: http:/www.etsi.org The present document may be made available in more than one electronic version or in print. In any case of existing or perceived difference in contents between such versions,
4、 the reference version is the Portable Document Format (PDF). In case of dispute, the reference shall be the printing on ETSI printers of the PDF version kept on a specific network drive within ETSI Secretariat. Users of the present document should be aware that the document may be subject to revisi
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6、 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 2008. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTM, TIPHONTM, the TIPHON
7、logo and the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI EG 202 086 V2.0.0 (2008-07) 3 Contents Intellectual Property Rights4 Foreword.4 1 Scop
8、e 5 2 References 5 2.1 Normative references .6 2.2 Informative references6 3 Definitions and abbreviations.7 3.1 Definitions7 3.2 Abbreviations .7 4 Principles7 4.1 Responsibility.7 4.2 Technical requirements 7 4.2.1 Loudness.8 4.2.2 Encoding and Low Bit Rate Coding .8 4.2.3 Voice activity detection
9、 and speech multiplexing 8 4.2.4 Bit integrity.8 4.2.5 Absolute delay 8 4.2.6 Echo control9 4.2.7 Noise, crosstalk and group delay distortion 9 4.2.8 Error performance.9 4.2.9 Synchronization 9 4.3 Provision of Information 9 4.4 Future developments 10 Annex A (informative): Bibliography.11 History 1
10、2 ETSI ETSI EG 202 086 V2.0.0 (2008-07) 4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
11、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 server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the
12、ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Forew
13、ord This ETSI Guide (EG) has been produced by ETSI Technical Committee Speech Processing, Transmission and Quality Aspects (STQ). ETSI ETSI EG 202 086 V2.0.0 (2008-07) 5 1 Scope The present document specifies a simple set of objectives, principles and responsibilities for the transmission performanc
14、e of multiple interconnected networks that provide “traditional quality (POTS)“ circuit switched telephony services. The objectives, principles and responsibilities take account of the liberalization of telephony services and the interconnection of several separate networks, each with different topo
15、logies, in the provision of telephony connections. The present document applies to: national and international networks; Digital Networks and Integrated Digital Networks (i.e. networks where the only analogue component may be the local loop). The present document applies in the cases where the telep
16、hony service is: contracted between the network operator and the customer/end user; and contracted through a service provider. It applies where: the caller pays for the call; the recipient pays for the call (e.g. the 800 service); or the cost of the call is shared by the caller and the recipient. Th
17、e present document does not apply to any segment of calls where either the calling or called terminal is a mobile “terminating network“. 2 References References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific reference,
18、subsequent revisions do not apply. Non-specific reference may be made only to a complete document or a part thereof and only in the following cases: - if it is accepted that it will be possible to use all future changes of the referenced document for the purposes of the referring document; - for inf
19、ormative references. Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. For online referenced documents, information sufficient to identify and locate the source shall be provided. Preferably, the primary sour
20、ce of the referenced document should be cited, in order to ensure traceability. Furthermore, the reference should, as far as possible, remain valid for the expected life of the document. The reference shall include the method of access to the referenced document and the full network address, with th
21、e same punctuation and use of upper case and lower case letters. NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. ETSI ETSI EG 202 086 V2.0.0 (2008-07) 6 2.1 Normative references The following referenced document
22、s are indispensable for the application of the present document. For dated references, only the edition cited applies. For non-specific references, the latest edition of the referenced document (including any amendments) applies. 1 ITU-T Recommendation G.113 (1996): “Transmission impairments“. 2 ITU
23、-T Recommendation G.114 (1996): “One -way transmission time“. 3 ITU-T Recommendation G.126 (1993): “Listener echo in telephone networks“. 4 ITU-T Recommendation G.131 (1996): “Control of talker echo“. 5 ITU-T Recommendation G.168 (1997): “Digital network echo cancellers“. 6 ITU-T Recommendation G.17
24、5 (1997): “Transmission planning for private/public network interconnection of voice traffic“. 7 ITU-T Recommendation G.711 (1988): “Pulse code modulation (PCM) of voice frequencies“. 8 ITU-T Recommendation G.821 (1996): “Error performance of an international digital connection operating at a bit ra
25、te below the primary rate and forming part of an integrated services digital network“. 9 ITU-T Recommendation G.822 (1988): “Controlled slip rate objectives on an international digital connection“. 10 ITU-T Recommendation G.826 (1996): “Error performance parameters and objectives for international,
26、constant bit rate digital paths at or above the primary rate“. 11 ITU-T Recommendation Q.551 (1996): “Transmission characteristics of digital exchanges“. 12 ITU-T Recommendation Q.552 (1996): “Transmission characteristics at 2-wire analogue interfaces of digital exchanges“. 13 ETSI EG 201 050: “Spee
27、ch Processing, Transmission and Quality Aspects (STQ); Overall Transmission Plan Aspects for Telephony in a Private Network“. 14 ETSI EN 300 462-1-1: “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 1-1: Definitions and terminology for synchronization netw
28、orks“. 15 ETSI EN 300 462-6-1: “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 6-1: Timing characteristics of primary reference clocks“. 16 ISO/IEC 11573 (1994): “Information technology - Telecommunications and information exchange between systems - Synch
29、ronization methods and technical requirements for Private Integrated Services networks“. 2.2 Informative references The following referenced documents are not essential to the use of the present document but they assist the user with regard to a particular subject area. For non-specific references,
30、the latest version of the referenced document (including any amendments) applies. Not applicable. ETSI ETSI EG 202 086 V2.0.0 (2008-07) 7 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: network operator: organizatio
31、n that runs a network (switches and transmission) on which a service is provided service provider: organization that offers and provides the telephony service to the customer NOTE: This may be the same organization that is the network operator. 3.2 Abbreviations For the purposes of the present docum
32、ent, the following abbreviations apply: A/D Analogue to Digital ADPCM Adaptive Differential Pulse Code Modulation ATM Asynchronous Transfer Mode D/A Digital to Analogue NTP Network Termination Point QDU Quantizing Distortion Units RLR Receive Loudness Rating SLR Send Loudness Rating VAD Voice Activi
33、ty Detection 4 Principles 4.1 Responsibility With the development of competition so that a substantial proportion of calls pass across more than one network, it is no longer realistic to consider that any operator has overall responsibility for the quality of a call from one user-network interface t
34、o the other unless the call remains wholly on-net. Responsibility implies choice and control, but in many cases this choice and control do not exist. EXAMPLE 1: Call termination, where normally there is only one operator who serves a given number and the operator who is paid to handle the call has n
35、o choice over its delivery. EXAMPLE 2: Call origination for carrier selection or pre-selection, where the subscriber chooses their access operator and their call handling operator separately such that the call handling operator has no control over the choice of access operator. In both these cases t
36、he operator who is paid to handle the call may have to pay the other operator but has no effective control since the other operator is in a monopoly position. Furthermore the calling user/subscriber has no control over the terminating operator selected by their correspondents. In this situation, ade
37、quate end-to-end quality can be achieved only by all operators following standards and where there are choices that might involve incompatibilities by exchanging information and cooperating so that incompatibilities can be avoided. 4.2 Technical requirements The following technical requirements appl
38、y to the segment of the call for which the operator is responsible, in accordance with clause 4.1. ETSI ETSI EG 202 086 V2.0.0 (2008-07) 8 4.2.1 Loudness The transmission level point at the digital exchange should be 0 dBr. Loss in analogue access sections (i.e. local exchange lines) should be such
39、that the SLR at the A/D conversion point is in the range 7 dB to 10 dB and the RLR in the range 1 dB to 4 dB, when analogue telephones with the nominal SLR/RLR values defined in national or harmonized standards are attached to the NTPs. Wherever possible, signal level adjustment should be made in th
40、e analogue domain. Digital loss or gain pads limit the available level range and increase signal distortion and should not be used if possible. 4.2.2 Encoding and Low Bit Rate Coding The encoding method used at interconnection points should be agreed bilaterally and conform to an ITU-T or European s
41、tandard. NOTE 1: The most common method is the one specified in ITU-T Recommendation G.711 7. Consideration should be given to the ability of the network to carry in-band data, facsimile and modem access to Internet providers. Particular consideration should be given to the trend towards increasing
42、data rates. Low bit rate coding adversely affects speech quality. The number of these devices should be limited and the impairments introduced should be minimized. NOTE 2: The effects of transcoding and compression are given as equipment impairment factors described in ITU-T Recommendation G.113 1.
43、The use of quantizing distortion units (QDU) is restricted to the effects of encoding and decoding in accordance with ITU-T Recommendation G.711 7. QDUs should not be used for other coding methods. Guidance for planners can be found in ITU-T Recommendation G 175 6 and EG 201 050 13. 4.2.3 Voice acti
44、vity detection and speech multiplexing Some systems are especially designed to provide a flexible “bandwidth on demand“ feature, utilizing a number of 64 kbit/s-channels in part of the connection in a more economical way, mainly for data transmission. For speech channels “Voice Activity Detection“ (
45、VAD) will reduce costs in a way similar to low bit-rate coding. The reduction of the transmitted bit-rate is performed by detecting speech pauses (VAD). The additional delay introduced by VAD should be taken into account. Systems that introduce significant delay may already be equipped with integrat
46、ed echo cancellers. The transmission parameters of VAD devices should be considered carefully during planning, mainly in conjunction with echo cancelling in other sections of the connection. VAD devices generally introduce a measure of temporal clipping of speech signals. Care should be taken with t
47、andeming of such devices in order to minimize degradation to the intelligibility of the speech. NOTE: Some non-standard VAD systems that include integrated echo cancellers may also insert loss. 4.2.4 Bit integrity Bit integrity is possible across a network only where the path is wholly digital. It m
48、ay be required for services such 64 kbit/s unrestricted but is not required for speech. Signalling processing devices such as echo cancellers, low bit rate coders and digital loss and gain pads corrupt bit integrity. If there is to be an option for bit integrity then is should be possible to disable
49、 such devices. 4.2.5 Absolute delay Irrespective of the effect of delay on echo, absolute delay should be minimized. Absolute delay does not impair the intelligibility of speech but if the total delay exceeds around 150 ms from mouth to ear, it begins to affect the interactivity of conversations. Therefore if practicable large delays of this magnitude should be avoided for speech. Detailed guidance is given in ITU-T Recommendation G.114 2. NOTE: Some low bit rate coders introduce high values of delay. Some terminal e
