1、 International Telecommunication Union ITU-T G.776.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2008) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS Digital terminal equipments Operations, administration and maintenance features of transmission equipment SPNE mechanis
2、ms/auxiliary functions Recommendation ITU-T G.776.2 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-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUA
3、L 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 RADIOTELEPHONY AND LINE TELEPHONY G.450G.4
4、99 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARACTERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 General G.700G.709 Coding of analogue signals by pulse code modulation G.710G.719 Coding of analogue signals by methods other than PCM G.720G.729 Principal characteristics of primary multiplex
5、 equipment G.730G.739 Principal characteristics of second order multiplex equipment G.740G.749 Principal characteristics of higher order multiplex equipment G.750G.759 Principal characteristics of transcoder and digital multiplication equipment G.760G.769 Operations, administration and maintenance f
6、eatures of transmission equipment G.770G.779 Principal characteristics of multiplexing equipment for the synchronous digital hierarchy G.780G.789 Other terminal equipment G.790G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 QUALITY OF SERVICE AND PERFORMANCE GEN
7、ERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA 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. Rec. ITU-T G.776.
8、2 (06/2008) i Recommendation ITU-T G.776.2 SPNE mechanisms/auxiliary functions Summary Signal processing functions (SPFs) designed for speech quality, when located in the network, may interact with in-band signalling (e.g., tandem free operation) and non-voice services (e.g., high speed circuit swit
9、ched data). The platform that carries these SPFs is called signal processing network equipment (SPNE) and may therefore need to provide mechanisms/auxiliary functions to support in-band signalling and non-voice services depending on where in the network the SPNE is going to be deployed and what serv
10、ices and/or in-band signalling are present. This Recommendation defines these mechanisms/auxiliary functions of a signal processing network equipment (SPNE) designed for the use in the circuit switched part of a network (mobile, fixed and hybrid). Source Recommendation ITU-T G.776.2 was approved on
11、13 June 2008 by ITU-T Study Group 16 (2005-2008) under Recommendation ITU-T A.8 procedure. Keywords Codec, echo cancellation, HSCSD, SPF, SPNE, TFO, VAD/CNG, VED, V.21. ii Rec. ITU-T G.776.2 (06/2008) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency i
12、n the field of telecommunications, information and communication technologies (ICTs). 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 Recommendations on them with a view to s
13、tandardizing 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 approval of ITU-T Recommendations i
14、s 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 “Administration“ is used for conciseness to
15、 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 with the Recommendation is ac
16、hieved 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 required of any party. INTELLECTU
17、AL 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 Intellectual Property Rights, whether
18、 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. However, implementers are cauti
19、oned 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 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of I
20、TU. Rec. ITU-T G.776.2 (06/2008) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Term defined in this Recommendation 2 4 Abbreviations and acronyms 2 5 Conventions 3 6 SPNEs in typical network scenarios. 3 6.1 ISDN/PSTN 3 6.2 Mobile network 3 6.3 Hybrid
21、(TDM/IP) network . 4 7 Types and functional entities of the SPNE. 5 7.1 Types A and B 5 7.2 The signal processing functions . 6 7.3 SPNE mechanisms/auxiliary functions 6 Appendix I Example of an SPNE serving one E1/T1. 9 I.1 SPNE:VED. 9 Bibliography. 10 iv Rec. ITU-T G.776.2 (06/2008) Introduction S
22、ignal processing functions designed for speech quality are normally provided on a platform called signal processing network equipment. Since these signal processing functions may either not be required on all calls or not be applied to digital media, additional mechanisms/auxiliary functions are req
23、uired which are not necessarily part of the specific signal processing functions as such. Therefore, these auxiliary functions/mechanisms are considered to be provided by a signal processing network equipment. Rec. ITU-T G.776.2 (06/2008) 1 Recommendation ITU-T G.776.2 SPNE mechanisms/auxiliary func
24、tions 1 Scope This Recommendation defines mechanisms/auxiliary functions for a signal processing network equipment (SPNE) designed for the use in the circuit switched part of a network (mobile, fixed and hybrid). The SPNE addressed in this Recommendation is a physical entity that contains one or mor
25、e of the following signal processing functions (SPFs) optimized for speech quality, acoustic echo control, electric echo cancellation, noise reduction and automatic level control. The SPNE can be designed as stand-alone equipment or can be integrated in some other network equipment. The SPNE provide
26、s the SPFs permanent associated to the circuits or arranged in a pool. Depending on where in the network the SPNE is going to be provided, the mechanisms/auxiliary functions identified in this Recommendation include appropriate interfaces to allow external control of the SPFs and the support of in-b
27、and signalling such as tandem free operation (TFO) and of services such as high speed circuit switched data (HSCSD). 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 ti
28、me of publication, the editions indicated were valid. 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
29、 list of the currently valid ITU-T Recommendations 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 G.703 Recommendation ITU-T G.703 (2001), Physical/electrical characteristics of hierarc
30、hical digital interfaces. ITU-T G.704 Recommendation ITU-T G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/s hierarchical levels. ITU-T G.711 Recommendation ITU-T G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T Q.115.0 Recommendation IT
31、U-T Q.115.0 (2002), Protocols for the control of signal processing network elements and functions. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 in path equipment (IPE) b-3GPP TS 28.062: The term “in path equipment“ is used for any te
32、lecommunication equipment within the (64 kbit/s) transmission path for the speech signal between two entities, which want to communicate via IS messages, i.e., the IS partners. 2 Rec. ITU-T G.776.2 (06/2008) 3.2 Term defined in this Recommendation This Recommendation defines the following terms: 3.2
33、.1 hybrid network: A combined circuit switched and packet switched network, e.g., IP trunking. 3.2.2 signal processing function (SPF): An SPF designed/optimized for speech quality is a function (realized in hardware, silicon or software) that performs voice processing such as electric and acoustic e
34、cho control, noise reduction or automatic level control. 3.2.3 signal processing network equipment (SPNE): A type of network equipment or element that contains one or more signal processing functions or devices. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and ac
35、ronyms: BSC Base Station Controller CNG Comfort Noise Generation EC Echo Cancellation ECD Echo Control Device FFS For further study HSCSD High Speed Circuit Switched Data If Interface IP Internet Protocol IPE In-Path Equipment IS In-band Signalling ISC International Switching Centre ISDN Integrated
36、Services Digital Network L Linear conversion (combination of coder and decoder) LE Local Exchange MG Media Gateway MGC Media Gateway Controller MS Mobile Station MSC Mobile Switching Centre PSTN Public Switched Telephone Network RNC Radio Network Controller SPF Signal Processing Function SPNE Signal
37、 Processing Network Equipment SPNE:ECD Signal Processing Network Equipment containing an Echo Control Device SPNE:MG Signal Processing Network Equipment providing signal processing functions of a Media Gateway SPNE:VED Signal Processing Network Equipment containing a Voice Enhancement Device/functio
38、n Rec. ITU-T G.776.2 (06/2008) 3 TCH Traffic CHannel TDM Time-Division Multiplexing TE Transit Exchange TFO Tandem Free Operation VAD Voice Activity Detection VED Voice Enhancement Device/Function (acoustic echo control and noise reduction) 5 Conventions None. 6 SPNEs in typical network scenarios Th
39、e following clauses describe some exemplary network scenarios with SPNEs. 6.1 ISDN/PSTN A typical example in an ISDN/PSTN network would be a SPNE:ECD associated with an international switching centre (ISC). The SPNE:ECD provides echo control devices for a number of E1/T1 circuits. The SPNE:ECD can b
40、e deployed either as stand-alone equipment or integrated in an exchange/switch; see Figure 1. Figure 1 SPNE:ECD associated with an ISC 6.2 Mobile network In the mobile network, the so called SPNE:VED provides acoustic echo control and noise reduction to reduce the speech quality degradation due to a
41、coustic echo and noise injected into the network by the mobile station (MS). Some possible locations of the SPNE:VED (either as stand-alone equipment or as integrated version) in a mobile network are shown in Figure 2. LE TE ISC Possible locations for SPNE:ECD E1/T1 4 Rec. ITU-T G.776.2 (06/2008) Fi
42、gure 2 Possible locations of a SPNE:VED in a mobile network 6.3 Hybrid (TDM/IP) network The media gateway includes an SPNE:MG providing signal processing functions such as echo cancellation, transcoding and VAD/CNG. The SPNE:MG is normally integrated in a media gateway; see Figure 3. Figure 3 SPNE:M
43、G BSC/RNC MSC possible locations for SPNE:VED MS radio network core network E1/T1 E1/T1 IP LE/TE MG MGC SPNE:MG TDM network IP network E1/T1 Rec. ITU-T G.776.2 (06/2008) 5 7 Types and functional entities of the SPNE SPNE as described in this Recommendation is a physical equipment that can be located
44、 in several places in a circuit switched network. The SPFs contained in the SPNE process the voice/voiceband signals carried on the bearer to improve their quality. In addition to these SPFs, the SPNE needs to have mechanisms/auxiliary functional entities, depending on where in the network the SPNE
45、is going to be deployed and what services the network supports. 7.1 Types A and B SPNE types A and B can be designed as either stand-alone equipment or as an integrated device. 7.1.1 Type A: SPNE with a control plane interface for SPNE The SPFs of this type of SPNE are controlled (enabled/disabled)
46、on a per-call basis. A specific control plane interface is required, whereby the control plane is either embedded in the bearer carrying the media or has its own bearer. For a stand-alone SPNE, the protocols used at the control plane interface are described in ITU-T Q.115.0, whereas for an integrate
47、d SPNE this is an implementation matter. 7.1.2 Type B: SPNE without a control plane interface for SPNE This type of SPNE can adopt the IS_Passive behaviour of an in-path equipment (IPE) for its SPFs, if required. An IS_Passive IPE shall never actively initiate the exchange of IS messages. The active
48、 initiation is only done by terminals or their “representatives“. They need not and do not understand the IS protocol, but let it pass unaltered. This type of SPNE requires detection mechanisms for in-band signalling, any kind of non-voice information and a protocol entity to communicate with other
49、SPNEs in order to optimize the provisioning of the SPFs. This applies for the stand-alone version as well as for the integrated version. The following auxiliary functional entities are identified: A control plane interface that allows the SPFs to be controlled by the corresponding call control/bearer control entity (network logic/resource control) on a per-call basis. A TFO functional entity that allows the disabling/bypass of the SPFs. An HSCSD functional entity that a
