1、 ETSI EG 202 425 V1.1.1 (2007-02)ETSI Guide Speech Processing, Transmission and Quality Aspects (STQ);Definition and implementation of VoIP reference pointETSI ETSI EG 202 425 V1.1.1 (2007-02) 2 Reference DEG/STQ-00070 Keywords QoS, VoIP ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - F
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5、If you find errors in the present document, please send your comment to one of the following services: http:/portal.etsi.org/chaircor/ETSI_support.asp Copyright Notification No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to re
6、production in all media. European Telecommunications Standards Institute 2007. All rights reserved. DECTTM, PLUGTESTSTM and UMTSTM are Trade Marks of ETSI registered for the benefit of its Members. TIPHONTMand the TIPHON logo are Trade Marks currently being registered by ETSI for the benefit of its
7、Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI ETSI EG 202 425 V1.1.1 (2007-02) 3 Contents Intellectual Property Rights5 Foreword.5 1 Scope 6 2 References 6 3 Abbreviations .6 4 Overview of the context .7 5 Concept of V
8、oIP reference point9 6 Architecture of the reference point.10 6.1 General characteristics of the VoIP reference point .10 6.1.1 Network interface .10 6.1.2 Call establishment.10 6.1.3 Registration on VoIP services platforms 10 6.1.4 Performances 11 6.2 Operating modes of the device .11 6.2.1 Connect
9、ion with a terminal.11 6.2.2 Connection with a Gateway11 6.3 Specific characteristics of the VoIP reference point.12 6.3.1 IP Interface12 6.3.1.1 Wire interface12 6.3.1.2 Wireless interface12 6.3.2 Measurement interfaces 12 6.3.2.1 Analog interface12 6.3.2.2 Digital interface.12 6.3.3 Call establish
10、ments .12 6.3.3.1 Configuration 12 6.3.3.2 Registration .12 6.3.3.3 Dialing.13 6.3.4 Signalization protocols .13 6.3.5 Codecs 13 6.3.6 Clock accurracy 13 6.3.7 Jitter buffer14 6.3.8 Delay characteristics .14 6.3.9 Full duplex performances .14 6.3.10 Configuration and control of the device .14 Annex
11、A (informative): Example of an implementation of the VoIP reference point15 A.1 Introduction 15 A.2 Advantages of the implementation.15 A.3 Technical characteristics 15 A.3.1 General architecture .15 A.3.2 Interfaces 16 A.3.3 Registration and configuration .16 A.3.4 Call establishments.16 A.3.5 Sign
12、alization protocols and codecs.16 A.3.6 Jitter buffer .17 A.4 Calibration17 A.4.1 Softphone calibration .17 A.4.2 Reference point calibration.18 ETSI ETSI EG 202 425 V1.1.1 (2007-02) 4 A.5 Use for terminal characterization .19 A.6 Limits of the implementation .20 History 21 ETSI ETSI EG 202 425 V1.1
13、.1 (2007-02) 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 publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intell
14、ectual 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 ETSI IPR Policy, no investi
15、gation, 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. Foreword This ETSI Guide (EG) ha
16、s been produced by ETSI Technical Committee Speech Processing, Transmission and Quality Aspects (STQ). ETSI ETSI EG 202 425 V1.1.1 (2007-02) 6 1 Scope The speech quality perceived by the users is the result of combined impairments generated by the network but also by the terminals. This is why the c
17、haracterization of the terminal performances is a major point in the deployment of telephony services. It is generally agreed that an ISDN access at 0 dBr represents a reference point for the PSTN, on which reference testing suites like TBR 21 1 or TBR 38 2 for instance can be implemented. For IP ne
18、tworks, it is really different, actually there is no reference access. For this reason, the characterization of VoIP end points is usually performed on a configuration using an ISDN access, which requires the use of an IP-PSTN gateway. Thus, the characterizations of VoIP end points performance are i
19、mpacted by the performances of other equipments, generally the gateway. The present document specifies the characteristics of an “IP reference device“ for voice over IP services. The present document provides information about the architecture of the system. The present document describes the differ
20、ent elements constituting the device and specifies the operation of each. Information about a practical implementation of this device is annexed to the present document. 2 References The following documents contain provisions which, through reference in this text, constitute provisions of the presen
21、t document. References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. Referenced documents which are not found to b
22、e publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. 1 ETSI TBR 21: “Terminal Equipment (TE); Attachment requirements f
23、or pan-European approval for connection to the analogue Public Switched Telephone Networks (PSTNs) of TE (excluding TE supporting the voice telephony service) in which network addressing, if provided, is by means of Dual Tone Multi Frequency (DTMF) signalling“. 2 ETSI TBR 38: “Public Switched Teleph
24、one Network (PSTN); Attachment requirements for a terminal equipment incorporating an analogue handset function capable of supporting the justified case service when connected to the analogue interface of the PSTN in Europe“. 3 ITU-T Recommendation G.711: “Pulse Code Modulation (PCM) of voice freque
25、ncies“. 4 ITU-T Recommendation G.712: “Transmission performance characteristics of pulse code modulation channels“. 3 Abbreviations For the purposes of the present document, the following abbreviations apply: ACG Amplitude Control Gain DHCP Dynamic Host Control Protocol EFR Enhanced Full Rate HATS H
26、ead And Torso Simulator IP Internet Protocol ETSI ETSI EG 202 425 V1.1.1 (2007-02) 7 ISDN Integrated Services Digital Network LAN Local Area Network MGCP Media Gateway Control Protocol POTS Plain Old Telephone Service PSTN Public Switched Telephone Network SIP Session Initiation Protocol TDM Time Di
27、vision Multiplexing VLAN Virtual LAN VoIP Voice over Internet Protocol WAN Wide Area Network 4 Overview of the context During performance evaluations of IP terminals or end points, one of problems encountered is the lack of a reference point or reference access on the IP network as the one existing
28、on the PSTN with the ISDN. This lack of reference points on the IP network penalizes and makes it difficult to characterize the performance of IP equipments. Generally, the characterization of an IP terminal is performed through an ISDN access connected to the IP network by a VoIP gateway (figure 1)
29、. IP Network PSTNISDN AccessMeasurement deviceVoIP GWTerminal to characterizeFigure 1: Standard configuration for performance evaluations of IP terminals The implementation of an ISDN access for the characterization of a terminal involves contaminations of results by the performances of the VoIP gat
30、eway used to connect the IP network to the PSTN. Indeed the sending characteristics of a terminal to be evaluated are seen as a whole with the characteristics of the VoIP gateway in the IP to PSTN direction. In the same way, the receiving characteristics of the terminal are seen as a whole with the
31、characteristics of the VoIP gateway in the PSTN to IP direction. It is obvious that this situation creates some problems when the performances of the gateway are badly known or out of control. The idea to improve the situation is to bring back the reference point at the level of the IP side the voic
32、e over IP gateway (figure 2). So with the implementation of a “reference gateway“, the reference point moves from the switched network to the IP network. ETSI ETSI EG 202 425 V1.1.1 (2007-02) 8 Figure 2: Proposed configuration for performance evaluations of IP end points: use a reference point on th
33、e IP network If the characterization of VoIP services or telephony architectures does not generate major difficulties, for the characterization of VoIP equipments, there are several reasons to develop a reference point on IP networks: The increase of development and marketing of IP terminals like IP
34、phones, videophones or domestic gateways introduced an important need of characterization for these new equipments. For this reason it becomes urgent to be able to evaluate the performances of these terminals compared to a same measurement point, whose performance is perfectly controlled. For VoIP s
35、ervices, a dissymmetry between the behaviour and characteristics of the two transmission ways is frequently noticed. This is particularly true when different kinds of terminals (e.g. an IPphone and an IP to PSTN network gateway) are implemented on the same link. An IP reference point must give the p
36、ossibility to determine, absolutely and independently, the sending and receiving performances of terminals. So with the reference device it should be possible to identify the differences of behaviour or characteristics. Similarly, on IP communications problems on the speech signal level are frequent
37、ly noticed. These problems often come from a bad implementation of the telephony applicative part and in particular a bad implementation of the codecs. The implementation of a reference element on the IP network makes it possible to check the compliance of sending and receiving loudness ratings. Fre
38、quency responses, loudness ratings, sidetone, distortions, noise levels are essential characteristics for telephony terminals. Therefore, a reference point on an IP network is a device which allows this type of characterization independently of any other equipment performance (Network gateway for ex
39、ample). For VoIP termination equipment, the evaluation of intrinsic speech quality (distortion of the voice signal, reduction and delay of acoustic echo, etc.) is currently very difficult or impossible. The evaluation of the performance of this equipment is impacted by the characteristics of the voi
40、ce over IP system present at the other end of the IP segment of the transmission path. The development of a reference point makes it possible to get rid of this difficulty and to determine specific performances to the tested terminal. ETSI ETSI EG 202 425 V1.1.1 (2007-02) 9 5 Concept of VoIP referen
41、ce point When you move the reference point from the PSTN to the IP network, the reference point became a sort of “reference gateway“. The concept of the VoIP reference point is presented on figure 3. IP NetworkReceiving Packet flowSending Packet flowIP domain Electric domainFigure 3: Presentation of
42、 the concept of the VoIP reference point It is an interface between 2 domains, interface with controlled and well known characteristics. The reference point is a device making the connection between an IP packet domain and an electric domain for speech signals. This reference device is characterized
43、 by four important characteristics: Compliance codec implementations. Conform amplitudes for speech signals. Control of the processing delays. Tracing any characteristic modification. These four characteristics ensure: no specific impairments due to a bad implementation of codecs; a correct amplitud
44、e for the speech signals send on the IP network and no amplitude modification for the speech signals receive from the IP network; the knowledge of the respective processing delay of the sending and receiving parts to make possible the determination of the processing delays of terminals to be tested;
45、 a recording of all events linked with characteristic modifications to make possible a correct interpretation of terminal evaluation results. ETSI ETSI EG 202 425 V1.1.1 (2007-02) 106 Architecture of the reference point 6.1 General characteristics of the VoIP reference point 6.1.1 Network interface
46、As IP telephony terminal, the reference point must have an interface to allow connection to IP networks. It must be able to reach with a wire connection to different types of network: dedicated LAN, company LAN, WAN, etc. The privileged interface to comply with these requirements is the Ethernet int
47、erface. The specificity of this device as a reference element in IP network implies having only one type of interface and excluded wireless interfaces like Wifi. 6.1.2 Call establishment This device must be able to establish a communication with any VoIP terminal. In particular, it must be able to b
48、e in communication with IP terminals such as IPphones, softphones and the domestic gateways. The reference point must also communicate with terminals of the PSTN like POTS and ISDN equipment. It must also be able to be in communication with 2G and 3G mobile. At the opposite of IP to IP calls, these
49、communications are established via VoIP network gateways. IP NetworkManagement Platform(Gatekeeper, Call Manager, IP Centrex )VoIP TerminalVoIP Reference PointPSTNRadio NetworkAnalog or ISDN terminal2G or 3G mobileFigure 4: Inter connection of the VoIP reference point with other terminals 6.1.3 Registration on VoIP services platforms This device must be able to be registered on any VoIP platform. To be used under the greatest possible number of conditions, it is essential that the VoIP reference point has the functionalities of regis
