1、 International Telecommunication Union ITU-T Q.115.2TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2007) SERIES Q: SWITCHING AND SIGNALLING Clauses applicable to ITU-T standard systems Logic and protocols for the control of signal processing network elements and functions Logic for the control
2、of voice enhancement devices and functions ITU-T Recommendation Q.115.2 ITU-T Q-SERIES RECOMMENDATIONS SWITCHING AND SIGNALLING SIGNALLING IN THE INTERNATIONAL MANUAL SERVICE Q.1Q.3 INTERNATIONAL AUTOMATIC AND SEMI-AUTOMATIC WORKING Q.4Q.59 FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THE ISDN Q.
3、60Q.99 CLAUSES APPLICABLE TO ITU-T STANDARD SYSTEMS Q.100Q.119 General clauses Q.100Q.109 Transmission clauses for signalling Q.110Q.114Logic and protocols for the control of signal processing network elements and functions Q.115 Abnormal conditions Q.116Q.119 SPECIFICATIONS OF SIGNALLING SYSTEMS No
4、. 4, 5, 6, R1 AND R2 Q.120Q.499 DIGITAL EXCHANGES Q.500Q.599 INTERWORKING OF SIGNALLING SYSTEMS Q.600Q.699 SPECIFICATIONS OF SIGNALLING SYSTEM No. 7 Q.700Q.799 Q3 INTERFACE Q.800Q.849 DIGITAL SUBSCRIBER SIGNALLING SYSTEM No. 1 Q.850Q.999 PUBLIC LAND MOBILE NETWORK Q.1000Q.1099 INTERWORKING WITH SATE
5、LLITE MOBILE SYSTEMS Q.1100Q.1199 INTELLIGENT NETWORK Q.1200Q.1699 SIGNALLING REQUIREMENTS AND PROTOCOLS FOR IMT-2000 Q.1700Q.1799 SPECIFICATIONS OF SIGNALLING RELATED TO BEARER INDEPENDENT CALL CONTROL (BICC) Q.1900Q.1999 BROADBAND ISDN Q.2000Q.2999 SIGNALLING REQUIREMENTS AND PROTOCOLS FOR THE NGN
6、 Q.3000Q.3999 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Q.115.2 (01/2007) i ITU-T Recommendation Q.115.2 Logic for the control of voice enhancement devices and functions Summary ITU-T Recommendation Q.115.2 describes the network logic for the control of voice
7、 enhancement devices/functions (VEDs) to be deployed in the network(s). A VED is defined as certain signal processing (acoustic echo control and noise reduction) in the digital transmission path. Mobile networks, where acoustic echo and noise is a common problem, are examples of where VEDs are deplo
8、yed. The signal processing network equipment for VED (SPNE:VED) is the platform that incorporates the VED. The network logic described in ITU-T Recommendation Q.115.2 avoids multiple provisioning of voice enhancement devices/functions in the same digital transmission path of a connection. Source ITU
9、-T Recommendation Q.115.2 was approved on 13 January 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. Keywords Acoustic echo control, noise reduction, signal processing network equipment, signalling. ii ITU-T Rec. Q.115.2 (01/2007) FOREWORD The International Tel
10、ecommunication 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 Recommendations on the
11、m 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 approval of ITU-T
12、 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 “Administration“ is used
13、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 with the Rec
14、ommendation 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 required of any
15、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 Intellectual Propert
16、y 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. However, imple
17、menters 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 prior writte
18、n permission of ITU. ITU-T Rec. Q.115.2 (01/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 4 Abbreviations and acronyms 2 5 Conventions 2 6 Voice enhancement control logic . 3 6.1 Abstract model 3 6.2 SPNE:VED. 4 6.3 Voice enhancement control logic . 4 Bibliography. 11 ITU-T Rec.
19、Q.115.2 (01/2007) 1 ITU-T Recommendation Q.115.2 Logic for the control of voice enhancement devices and functions 1 Scope Acoustic echo and noise is a common problem in many networks, e.g., mobile networks. Special signal processing network equipment (SPNE) containing voice enhancement devices/funct
20、ions (VEDs) has been designed to enhance voice quality. This SPNE:VED can be provided as a stand-alone version or integrated into other network equipment. This Recommendation defines a network logic that provides the optimal placement (nearest to the source) of, and avoids multiple provisioning of,
21、VEDs in a connection. This voice enhancement control logic (VECL) is applicable to network entities that control a VED on a per-call basis. As VEDs will normally be deployed in mobile networks, the VECL described in this Recommendation is considered to be applicable in any network that provides VED.
22、 NOTE Multiple VEDs in a connection would waste resources and the interaction between VEDs could impair the voice quality (in the sense of VEDs processing a signal that has already been processed by a VED). 2 References The following ITU-T Recommendations and other references contain provisions whic
23、h, through reference in this text, constitute provisions of this Recommendation. At the time 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 ap
24、plying the most recent edition of the Recommendations and other references listed below. A 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
25、-T Q.115.0 ITU-T Recommendation Q.115.0 (2002), Protocols for the control of signal processing network elements and functions. 3 Definitions This Recommendation defines the following terms: 3.1 acoustic echo: The reflected signal resulting from the acoustic path between the earphone/loudspeaker and
26、microphone of a hand-held or hands-free mobile station. 3.2 noise: In the context of voice enhancement, noise is defined as a slowly varying stochastic process appearing additive to the desired speech signal. Specifically, the variation in the characteristics of the noise process is such that it can
27、 be considered approximately stationary over much longer time intervals than a typical speech signal. 3.3 signal processing function (SPF): A software function that performs voice processing such as electric and acoustic echo control, noise reduction or automatic level control. 3.4 signal processing
28、 network equipment (SPNE): Type of network equipment which contains one or more signal processing function(s). In this Recommendation, the focus is on the SPNE:VED (a SPNE that incorporates VED). 3.5 voice enhancement: Combination of acoustic echo cancellation and noise reduction in order to improve
29、 voice quality. 2 ITU-T Rec. Q.115.2 (01/2007) 3.6 voice enhancement device/function (VED): The combination of acoustic echo cancellation and noise reduction in the digital transmission send path provided on a hardware/software basis. NOTE b-ITU-T G.160 defines a VED for mobile networks. 3.7 voice e
30、nhancement control logic (VECL): A network control logic that provides the optimal placement (nearest to the source) of VEDs and avoids multiple provisioning of VEDs in a connection. 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: AEC Acoustic Echo Con
31、trol CS MGW Circuit Switched Media Gateway DB Database (data administered by the network operator) EC (network) Echo Canceller GMSC Gateway Mobile Switching Centre IPE Incoming Protocol Entity MSC Mobile Switching Centre NR Noise Reduction OPE Outgoing Protocol Entity SDL Specification and Descripti
32、on Language SPF Signal Processing Function SPNE Signal Processing Network Equipment/Function SPNE:VED SPNE that incorporates VED TFO Tandem Free Operation VE Voice Enhancement VECL Voice Enhancement Control Logic VED Voice Enhancement Device/Function VEDb i. Voice Enhancement Device in backward dire
33、ction included VEDb n.i. Voice Enhancement Device in backward direction not included VEDCF Voice Enhancement Device Control Function VEDCI Voice Enhancement Device Control Info VEDf i. Voice Enhancement Device in forward direction included VEDf n.i. Voice Enhancement Device in forward direction not
34、included VEDIB Voice Enhancement Device Information backward VEDIF Voice Enhancement Device Information forward VEDSF Voice Enhancement Device Switching Function 5 Conventions None. ITU-T Rec. Q.115.2 (01/2007) 3 6 Voice enhancement control logic 6.1 Abstract model Voice enhancement control logic (V
35、ECL) is associated with call/bearer control and has an interface to the incoming and outgoing protocol entities as well as to the voice enhancement device switching function (VEDSF). The VEDSF is either associated with the incoming or outgoing protocol entity. This allows the incoming/outgoing proto
36、col entity to take into consideration the call state when actually controlling the VED (e.g., enabling the VED only after the call has been answered and not during call set-up). In case of a stand-alone SPNE:VED the control protocols used on the interface between VEDSF and the voice enhancement devi
37、ce control function (VEDCF) are those defined in ITU-T Q.115.0, whereas, in case of an integrated SPNE:VED, this interface is an implementation matter. The VECL process can run in addition to other signal processing control logic, e.g., echo control logic (as defined in b-ITU-T Q.115.1), if a node p
38、rovides those signal processing functions in addition to VED. An example of such a node could be a gateway mobile switching centre (GMSC) that provides the VED for its mobile subscribers as well as the echo canceller (EC) for the interconnection to the fixed network. Figure 1 shows the functional en
39、tities and their interrelation. SignallingIncomingprotocolentityOutgoingprotocolentityCall/bearer control Routing etc.VEDIFSignallingVoice enhancementcontrol logic (VECL)VEDIBVEDCIVEDIFVEDIBVEDCIVEDSF VEDSFControl ControlVED control functionNRAECSPNE:VEDFor a specific call, theassociation is either
40、with theincoming or outgoing side.ITU-T Rec. Q.115.0 for stand-alone SPNE:VED; implementation-dependent for integrated SPNE:VEDBearer BearerThis RecommendationFigure 1 Voice enhancement control 4 ITU-T Rec. Q.115.2 (01/2007) 6.2 SPNE:VED The SPFs of a VED can be controlled by the VECL described in t
41、his Recommendation, if the SPNE:VED does provide a VEDCF. This applies to stand-alone as well as integrated SPNE:VEDs. Figure 2 shows a block diagram of a SPNE:VED with a control interface. Environment andterminal characteristicsNoiseAcousticechoAEC NRSPF1 SPF2VEDCFSinSoutRoutRinRRSSinoutinoutReceiv
42、e in portSend out portSend in portReceive out portControl interface: Integrated VED: control is implementation-dependent. Stand-alone VED: see ITU-T Rec. Q.115.0.Figure 2 SPNE:VED (AEC and NR controlled by VECL) 6.3 Voice enhancement control logic 6.3.1 General principles The voice enhancement contr
43、ol logic (VECL) is invoked for voice calls during call set-up, when recognizing the need for the provisioning of a voice enhancement device/function. The need for providing voice enhancement may be based on specific information, e.g., the subscriber profile, origin/destination-dependent responsibili
44、ties (agreements) or simply on the fact that voice enhancement devices/functions are available. The network operator can administer the use of TFO or VED for connections where both mechanisms TFO and VED are available. The voice enhancement control logic analyses the voice enhancement control inform
45、ation received via the signalling systems/protocols (if none is received, information from a local database or subscriber profile may be used instead), as well as origin/destination-related information that is stored in the database of the call/bearer control node. Based on all these data, the voice
46、 enhancement control logic determines: a) VED-related actions (i.e., enable/disable) on the VED under control; and b) the VED information that has to be transmitted by the signalling systems/protocols in their call set-up messages. The voice enhancement control logic does not directly control the VE
47、D. It is the task of the VED switching function which communicates the result of the voice enhancement control logic to the VED control function (master-slave relation). Protocols to be used between the VED switching function and the VED control function are described in ITU-T Q.115.0. ITU-T Rec. Q.
48、115.2 (01/2007) 5 The voice enhancement control logic is applicable to any mobile-originating or mobile-terminating call, irrespective of the peer entity connected to the same network (arrow 2 in Figure 3) or another (mobile) network (arrow 1 in Figure 3). A VED may be provided not only for the own
49、mobile subscriber(s), based on e.g., the subscriber profile, but also for a (mobile) subscriber connected to another network, based on origin- and destination-related information respectively. Access network signalling Core network signallingRadio subsystemaccess networkNetwork subsystemcore network(1)(2)* Possible locations for VED(1) Connection between a mobile subscriber and a (mobile) subscriber belonging to another (mobile) network(2) Connection between two mobile subscribers belonging to the same service provider*MSCCS-MGWFigure 3 Ba
