1、 ETSI TR 102 430 V1.1.1 (2005-06)Technical Report Speech Processing, Transmission and Quality Aspects (STQ);Basic Issues concerning the Quality of Speech over Packet Technology(both Internet and Next Generation Networks)ETSI ETSI TR 102 430 V1.1.1 (2005-06) 2 Reference DTR/STQ-00037 Keywords noise,
2、QoS, speech 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 de Grasse (06) N 7803/88 Important notice Individual copies of the present do
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6、itten permission. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2005. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand the TIPHON logo
7、are Trade Marks currently being registered by ETSI 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 TR 102 430 V1.1.1 (2005-06) 3 Contents Intellectual Property Rights5 Foreword.5 1 Scope 6 2 R
8、eferences 6 3 Definitions and abbreviations.7 3.1 Definitions7 3.2 Abbreviations .8 4 The Market .9 4.1 Overview 9 4.1.1 PSTN 10 4.1.2 NGN11 4.1.3 Corporate VPNs11 4.1.4 Internet11 4.1.5 Voice traffic - Migration towards Internet13 4.2 Competition between NGN and the Internet 15 4.2.1 NGN Developmen
9、ts15 4.2.2 Internet Developments16 4.2.3 Hybrid developments16 4.3 NGN Services.16 4.4 Conclusion18 5 Quality of Service and Network Performance18 6 Impairments in packet networks.20 6.1 Networks 20 6.2 Terminal and codec issues22 6.2.1 Speech coding basics 22 6.2.2 Use of traditional circuit switch
10、ed codecs for voice over IP.23 6.2.3 Speech processing designed for speech over packet networks .24 6.2.3.1 Introduction.24 6.2.3.2 Codec enhancements.24 6.2.3.3 Playout buffer control .25 6.2.3.4 “Traditional“ Playout Buffer .25 6.2.3.5 Packet Loss Concealment .25 6.2.3.6 Clock drift (skew) .26 6.2
11、.3.7 Advanced Algorithms .26 6.2.3.8 Other approaches.27 7 Network design 28 7.1 Introduction 28 7.2 Guarantees28 7.3 Call related Quality of Service signalling.29 7.3.1 Basic concept for call related signalling negotiation 29 7.3.2 Discussion of the usefulness of call related QoS signalling negotia
12、tion.30 7.3.3 Conclusion on call-related QoS signalling negotiation.31 7.4 Signalling for congestion control .31 7.5 Reservation, Segregation and prioritization of traffic type.31 7.5.1 Reservation (RSVP)32 7.5.2 Prioritization (DiffServ)32 7.5.3 Segregation .32 8 Network performance targets .32 9 E
13、nd-to-end QoS classes at the application level.34 10 Testing37 ETSI ETSI TR 102 430 V1.1.1 (2005-06) 4 10.1 “Half channel“ approach.37 10.2 Quick and Indicative Testing Suite 38 10.2.1 General Test Description 38 10.2.2 Tests Based on Instrumental Assessment of Speech Samples 39 10.2.3 Tests Based o
14、n Auditory Assessment of Speech Samples39 10.2.4 Tests Based on Instrumental Computational Assessment Using Speech like (P.501) Test Signals39 10.2.5 Specific Echo Measurements40 10.2.6 Quality of Background Noise Transmission.40 10.2.7 Documentation of Test Results.40 10.3 The VoIP Reference Point
15、concept 41 11 Future work and unanswered questions .42 History 43 ETSI ETSI TR 102 430 V1.1.1 (2005-06) 5 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 public
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17、eb server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the 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
18、 may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by ETSI Technical Committee Speech Processing, Transmission and Quality Aspects (STQ). ETSI ETSI TR 102 430 V1.1.1 (2005-06) 6 1 Scope The present document gives an overview and critique
19、of the current developments in speech quality in packet based networks, including both the Internet and planned Next Generation Networks. The aim is to provide an overview of the main issues and their significance and to identify areas that need further work. The present document is written at a lev
20、el suitable for technical managers and engineers who are relatively new to the subject. It does not cover the issues at the depth that will be needed by a detailed specialist but its breadth should provide a valuable perspective for the specialist. The present document includes a discussion of how t
21、he market for telecommunications is developing and how the issues concerning speech quality in packet based networks will play a pivotal role in the increasing competition between the proposed telco NGN networks and the public Internet. The present document attempts to answer the following questions
22、: - What are the main issues? - Which issues are being solved satisfactorily? - How useful are the various approaches? - Can end-end quality be guaranteed? - How vulnerable is voice quality in a packet environment? - How do you design for good quality? - Do we need end-end signalling or lower layer
23、class based treatment or both? The present document is applicable to all forms of real-time 2-way conversational speech communications over packet based networks, including both telco NGN networks and the public Internet. 2 References For the purposes of this Technical Report (TR), the following ref
24、erences apply: 1 ETSI TS 101 329-2 (V2.1.3): “Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON) Release 3; End-to-end Quality of Service in TIPHON systems; Part 2: Definition of speech Quality of Service (QoS) classes“. 2 ITU-T Recommendation E.164: “The international pub
25、lic telecommunication numbering plan“. 3 ITU-T Recommendation E.800: “Terms and definitions related to quality of service and network performance including dependability“. 4 ITU-T Recommendation G.168: “Digital network echo cancellers“. 5 ITU-T Recommendation G.711: “Pulse code modulation (PCM) of v
26、oice frequencies“. 6 ITU-T Recommendation G.723.1: “Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s“. 7 ITU-T Recommendation G.726: “40, 32, 24, 16 kbit/s adaptive differential pulse code modulation (ADPCM)“. 8 ITU-T Recommendation G.729A: “Coding of speech at
27、 8 kbit/s using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP)“. 9 ITU-T Recommendation G.1000: “Communications Quality of Service: A framework and definitions“. ETSI ETSI TR 102 430 V1.1.1 (2005-06) 7 10 ITU-T Recommendation H.323: “Packet-based multimedia communications sy
28、stems“. 11 ITU-T Recommendation P.64: “Determination of sensitivity/frequency characteristics of local telephone systems“. 12 ITU-T Recommendation P.501: “Test signals for use in telephonometry“. 13 ITU-T Recommendation P.862: “Perceptual evaluation of speech quality (PESQ), an objective method for
29、end-to-end speech quality assessment of narrowband telephone networks and speech codecs“. 14 ITU-T Recommendation Y.1540: “Internet protocol data communication service - IP packet transfer and availability performance parameters“. 15 ITU-T Recommendation Y.1541: “Network performance objectives for I
30、P-based services“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: 3,1 kHz handset telephony: real-time two-way speech communication within the frequency range approximately from 300 Hz to 3 400 Hz using one or more
31、 telecommunication networks with suitable terminal equipment connected to the network termination points, characterized by: presentation of an acoustical speech signal to the mouthpiece of a traditionally shaped handset: - either analogue transport of said speech signal under real-time conditions th
32、rough and by telecommunication networks: said networks being intended for telephony applications between network termination points; or - filtering of said speech signal to the frequency range approximately from 300 Hz to 3 400 Hz; transformation of said speech signal either by waveform or by non-wa
33、veform (speech analysis) encoder; transport and processing of said speech signal under real-time conditions through and by telecommunication networks: said networks being intended for telephony applications between network termination points; back transformation (speech synthesis) of said speech sig
34、nal by the respective decoder; acoustical presentation of said speech signal in the frequency range approximately from 300 Hz to 3 400 Hz by the earpiece of a traditionally shaped handset. instant messaging service: proprietary service that provides peer-peer communications over the Internet and may
35、 also provide the ability to make calls to the PSTN or to receive calls from the PSTN NOTE: Most instant messaging services provide presence indications for the users on the subscribers contact list. quality of service: collective effect of service performances which determine the degree of satisfac
36、tion of a user of a service. It is characterized by the combined aspects of performance factors applicable to all services, such as: service operability performance; service accessibility performance; service retainability performance; service integrity performance; other factors specific to each se
37、rvice. NOTE: From ITU-T Recommendations E.800 3 and G.1000 9. ETSI ETSI TR 102 430 V1.1.1 (2005-06) 8 speech quality: expression of the degree of customer satisfaction with conversational speech transmission NOTE: Speech quality depends on the quality of the whole speech path from the talker at one
38、end of the connection to the listener at the other, and can be categorized into two types of quality: quality which is mainly dependent on handset acoustics and quality which is mainly dependent on the transmission medium. Telecommunications services where special attention needs to be paid to speec
39、h quality, such as audio teleconferencing and voice mail, should also be considered. telco: telecommunications organization (e.g. company, operator, provider) 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: 3GPP 3rdGeneration Partnership Project ADSL As
40、ymmetric Digital Subscriber Line/Loop API Applications Programming Interface ATM Asynchronous Transfer Mode AVT Audio/Visual Transport BICC Bearer Independent Call Control DiffServ Differentiated Service GSM Global System for Mobile communication IETF Internet Engineering Task Force iLBC internet Lo
41、w Bitrate Codec IN Intelligent Network IP Internet ProtocolIPDV IP Packet Delay variation IPER IP packet error ratio IPLR IP Packet Loss Ratio IPTD IP Packet Transfer Delay ISDN Integrated Services Digital Network ISP Internet Service Provider ISUP Integrated Services User Part ITU International Tel
42、ecommunication Union MPLS Multi-Protocol Label Switching NAT Network Address Translator NGN Next Generation Network NNI Network-Node Interface PCM Pulse Code Modulation PSTN Public Switched Telephone Network QoS Quality of Service QSIG Q reference point Signalling RSVP Resource reSerVation Protocol
43、RTP Real Time Protocol SIP Session Initialization Protocol UNI User Network Interface VoIP Voice over Internet Protocol VPN Virtual Private Network WLAN Wireless Local Area Network xDSL (Undefined) Digital Subscriber Line/Loop ETSI ETSI TR 102 430 V1.1.1 (2005-06) 9 4 The Market 4.1 Overview Overall
44、 the telecommunications market currently lacks direction. After a period of diverse investments, many of which have not been profitable, the top priority for many operators is to manage their short term financial objectives. In terms of fundamental resources: local physical infrastructure remains ex
45、pensive; transmission costs has fallen and is falling very rapidly thanks to a combination of absolute costs (cost per bit) and coding that enables more use to be made of a bit, i.e. more information may be transmitted via the same amount of bits (e.g. voice coding); NOTE 1: Transmission bit (not in
46、formation bit). switching costs are falling but faster for packet-based switching than for circuit-based switching, because packet based technology is benefiting from large economies of scale from its use in corporate networks and the public Internet? billing costs are falling only slowly, and the o
47、verheads of running a telecommunications business are increasing as a result of increased regulatory compliance costs including areas such as data protection. This situation leaves telcos re-focusing on core business and in particular developing broadband access networks. There is a great deal of di
48、scussion and confusion about how telecommunications networks will develop at a technical level in the next few years. Three years ago everyone was expecting the rapid and near universal adoption of IP technology but since then the whole investment climate has changed and the current situation is muc
49、h less clear. Some established operators are formulating plans for a fairly rapid migration to packet technology whilst others are waiting and planning to extend the lifetime of their existing switched infrastructure for as long as possible. In the Internet world, there is substantial growth in VoIP services, the most well known being Skype. Figure 1 shows a credible view of how networks will change. The diagram(see note) is best viewed in colour as the colours are significant. The blue rectangle covering the whole diagram
