1、 International Telecommunication Union ITU-T G.1020TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (07/2006) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Quality of service and performance Generic and user-related aspects Performance parameter definitions for quality of spe
2、ech and other voiceband applications utilizing IP networks ITU-T Recommendation G.1020 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSM
3、ISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS 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 RADIOTE
4、LEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MED
5、IA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. G.1020 (07/2006) i ITU-T Recommendation G.1020 Performance parame
6、ter definitions for quality of speech and other voiceband applications utilizing IP networks Summary The transmission of speech and other voiceband applications over packet networks brings with it new, sometimes unique, forms of quality degradation. There are many existing definitions for packet net
7、work performance parameters, yet the desire to control the quality of non-elastic isochronous applications requires additional, complementary information. The purpose of this Recommendation is to define packet network and terminal performance parameters that better reflect the perceived quality of t
8、he target applications. It is largely focused on quality impairments resulting from delay variation and packet loss which are peculiar to IP and other packet-based technologies, and which do not appear in traditional TDM networks. It discusses the interactions and trade-offs among these packet impai
9、rments, and describes mechanisms such as de-jitter buffers and packet loss concealment for reducing their effects on the quality of speech and other applications. However, this Recommendation avoids overlap by making reference to existing definitions wherever possible. The parameters defined by this
10、 Recommendation extend beyond the IP layer in many cases. End-to-end packet system (combination of end terminals and network) parameters are also necessary to determine the speech/voiceband quality. Clauses 5, 6 and 7 collect the parameter definitions for source terminals, packet networks, and desti
11、nation terminals, respectively. Overall parameters are defined in clause 8. In this version, the Recommendation adds formal definitions for many of the voice metrics identified in RFC 3611, RTCP Extended Reports (RTCP-XR). Annex A defines the gateway-specific reference points and parameters. Annex B
12、 provides information on packet loss distributions and packet loss models, and defines burst packet loss parameters. Annex C specifies an adaptive de-jitter buffer emulator and defines de-jitter buffer parameters. Appendix I tabulates the RTCP-XR parameters, along with the examination existing Recom
13、mendations and the final action, which typically was the addition of a parameter in this Recommendation. Source ITU-T Recommendation G.1020 was approved on 14 July 2006 by ITU-T Study Group 12 (2005-2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. G.1020 (07/2006) FOREWORD The Inter
14、national Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommenda
15、tions on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The appro
16、val of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administrati
17、on“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance
18、with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is requ
19、ired of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellec
20、tual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. Ho
21、wever, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the
22、prior written permission of ITU. ITU-T Rec. G.1020 (07/2006) iii CONTENTS Page 1 Scope 1 2 References. 3 3 Definitions 3 4 Abbreviations 4 5 Source terminal packet parameters. 5 5.1 Analogue/digital conversion clock accuracy (free-running) 5 5.2 Packet information field size 6 5.3 Packet overhead 6
23、5.4 Source terminal delay. 6 5.5 Source terminal delay variation 6 6 Packet network performance parameters 7 6.1 Summary of network performance parameters 7 6.2 Additional network parameters recommended. 8 7 Destination terminal packet parameters 9 7.1 Discussion of destination packet processing 10
24、7.2 Taxonomy of de-jitter buffer types/parameters and models. 11 7.3 System frequency offset, using destination clock as reference 15 7.4 Packet loss concealment (type, delay) 15 8 Overall performance parameters. 16 8.1 Overall delay (including source, network and destination) 16 8.2 End System Dela
25、y 16 8.3 Round Trip Delay. 16 8.4 Time-scale discontinuities in post-de-jitter and PLC stream . 16 8.5 Overall (frame/packet) loss (including network and destination) 17 Annex A VoIP gateway-specific reference points and performance parameters . 18 A.1 Introduction 18 A.2 Definitions 18 A.3 Source g
26、ateway parameters 18 A.4 Destination gateway parameters. 19 A.5 Overall delay 20 Annex B Packet loss distributions and packet loss models 20 B.1 Introduction 20 B.2 Common packet loss models 20 B.3 Example packet trace 23 B.4 Bibliography to Annex B 24 iv ITU-T Rec. G.1020 (07/2006) Page Annex C Exa
27、mple adaptive de-jitter buffer emulator. 26 C.1 Introduction 26 C.2 Parameter definitions 26 C.3 De-jitter buffer emulation. 27 Appendix I List of RTCP XR metrics. 28 BIBLIOGRAPHY 29 ITU-T Rec. G.1020 (07/2006) v Introduction The transmission of speech and other voiceband applications over packet ne
28、tworks brings with it new, sometimes unique, forms of quality degradation. There are many existing definitions for packet network performance parameters, yet the desire to control the quality of non-elastic isochronous applications requires additional, complementary information. The purpose of this
29、Recommendation is to define packet network and terminal performance parameters that better reflect the perceived quality of the target applications, extending beyond the IP layer in many cases. End-to-end packet system (combination of end terminals and network) parameters are also necessary to deter
30、mine the speech/voiceband quality, and this Recommendation defines them as well. ITU-T Rec. G.1020 (07/2006) 1 ITU-T Recommendation G.1020 Performance parameter definitions for quality of speech and other voiceband applications utilizing IP networks 1 Scope This Recommendation defines a set of perfo
31、rmance parameters for packet networks and end terminals that can assist in quantifying the end-to-end quality of speech and other voiceband applications. It is largely focused on quality impairments resulting from delay variation and packet loss which are peculiar to IP and other packet-based techno
32、logies, and which do not appear in traditional TDM networks. It discusses the interactions and trade-offs among these packet impairments, and describes mechanisms such as de-jitter buffers and packet loss concealment for reducing their effects on the quality of speech and other applications. This Re
33、commendation recognizes existing performance parameter definitions, and avoids duplication. Many factors that determine the quality of speech and voiceband applications are common to both TDM and IP-based networks, and are addressed in existing Recommendations. In the parlance of ITU-T Rec. I.350, t
34、he scope of this Recommendation is limited to the information transfer function of the 3 3 matrix, and only to the bearer channel. Call processing aspects of connection access and disengagement (e.g., dialtone delay and post-dialling delay) are not considered in this Recommendation. Furthermore, thi
35、s Recommendation does not specify numerical objectives for packet networks or end terminals, although this will be the subject of follow-on work. Figure 1 illustrates this scope, along with some other specifications with their areas of coverage. This Recommendation only defines parameters that descr
36、ibe packet terminal and packet transmission impairments that are unique to speech and voiceband application quality assessment. 2 ITU-T Rec. G.1020 (07/2006) Figure 1/G.1020 Scope of ITU-T Rec. G.1020 as it relates to other performance specifications Note that the number of IP networks between termi
37、nals is not limited in these definitions. Other ITU-T Recommendations supplement the parameters provided in this Recommendation. For example, transmission planning over hybrid Internet/PSTN connections is covered in ITU-T Rec. G.177. Still, other Recommendations specify such parameters in the contex
38、t of assessing the performance of IP packet transfer on international data communication services (e.g., ITU-T Rec. Y.1540). Network performance objectives for different QoS classes of IP-based services are described in ITU-T Rec. Y.1541, and end-to-end one-way delay objectives are specified in ITU-
39、T Rec. G.114. New Recommendations that complement ITU-T Rec. G.1020 are anticipated. Call processing aspects of the connection are in development. The ITU-T is also currently working on new Recommendations dealing with situations where the network is mainly an IP network with islands of PSTN, and wh
40、ere the network is mainly a PSTN network with islands of IP. ITU-T work to specify the performance objectives for VoIP terminals and gateways was recently completed in ITU-T Rec. P.1010. Finally, there is work on methods to assess the performance by measuring metrics related to the end-to-end qualit
41、y of VoIP. The definitions of packet transmission parameters that are unique to ATM networks are explicitly out of the scope of this Recommendation. This Recommendation should be particularly useful to those new to the area of Voice over IP (VoIP) who want to gain a better understanding of the facto
42、rs affecting the quality of these telecommunication systems. Developers of telecommunication equipment can use the parameters defined in this Recommendation to specify relevant aspects of their contribution to end-to-end performance. Service providers can use these parameters to effectively summariz
43、e performance of IP network solutions. ITU-T Rec. G.1020 (07/2006) 3 2 References The following 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 v
44、alid. All Recommendations and other references are subject to revision; users of this Recommendation 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 Recommendatio
45、ns is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T Recommendation G.107 (2005), The E-model, a computational model for use in transmission planning. ITU-T Recommendation G.113 (2001), Tr
46、ansmission impairments due to speech processing. ITU-T Recommendation G.114 (2003), One-way transmission time. ITU-T Recommendation G.177 (1999), Transmission planning for voiceband services over hybrid Internet/PSTN connections. ITU-T Recommendation I.356 (2000), B-ISDN ATM layer cell transfer perf
47、ormance. ITU-T Recommendation P.51 (1996), Artificial mouth. ITU-T Recommendation P.57 (2005), Artificial ears. ITU-T Recommendation P.1010 (2004), Fundamental voice transmission objectives for VoIP terminals and gateways. ITU-T Recommendation Y.1540 (2002), Internet protocol data communication serv
48、ice IP packet transfer and availability performance parameters. ITU-T Recommendation Y.1541 (2006), Network performance objectives for IP-based services. IETF RFC 3611 (2003), RTP Control Protocol Extended Reports (RTCP XR). 3 Definitions This Recommendation defines the following terms: 3.1 ear refe
49、rence point: A virtual point for geometric reference located at the entrance to the listeners ear, traditionally used for calculating telephonometric loudness ratings P.57. 3.2 terminal input measurement point: A measurement point in the physical medium connecting a terminal to an IP network that is crossed as IP packets leave the IP network and enter the terminal. This measurement point is as close to the terminal as possible. 3.3 IP terminal: An endpoint device intended for connecting to an IP network to support speech communicat
