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Home : ITU-T Home : Study Groups : Study Group 16
Question 18/16 – Interaction aspects of signal processing network equipment
(Continuation of Question 18/16)


Signal processing network equipment (SPNE) forms an integral part of communication networks. Recommendations have been developed covering circuit multiplication, speech enhancement (network echo cancellers, voice enhancement devices, and automatic level control), and GSTN/IP gateway equipment. This Question deals a) the logic and protocol requirements needed for the control and coordination of signal processing functionalities in the networks and terminals; b) with the study of interaction of SPNE, between different SPNE, between SPNE and terminals, and between SPNE and transmission systems; and c) with the consistency of Recommendations developed by Questions 15 and 16/16 in the area of SPNE.

The Question will attempt to work electronically where possible and to make full use of e-mail and conferencing facilities in an attempt to reduce its carbon footprint.

Study items

Study items to be considered include, but are not limited to:

  • Interactions between similar and different SPNE
  • Interactions between voiceband signals and SPNE
  • Interactions between SPNE and end-terminal equipment
  • Interactions between SPNE and transmission systems
  • Techniques to ensure high-quality SPNE Recommendations
  • Enhancement of existing Recommendations or development of new Recommendations to ensure that these interactions do not impair service
  • Logic and protocol requirements needed for control and coordination of signal processing functionalities in the networks and terminals. Such logic may be used to get the optimal arrangements of signal processing functionalities in the networks and terminals in a connection, or to configure their parameters for optimum performance
  • The availability of general evaluation procedures
  • Interaction between similar and different SPNE
  • Interaction between SPNE and other voiceband traffic technologies, including text telephony
  • The interaction of acoustic echo control devices with SPNE
  • Interaction between SPNE and transport systems
  • Interaction between SPNE in networks that include satellite links
  • The effect of tandem signal processing avoidance (e.g. codec bypass or tandem-free operation) on in-path SPNE
  • The methodology and technique to minimize the undesirable interaction of SPNE to achieve better voice quality
  • Study for SPNE used in next generation networks (SPNE interworking between GSTN and packet/IP networks)
  • Evaluation of the corresponding ITU-T Recommendations
  • To consider any additions to Recommendations that may help to measure and reduce the impact of climate change. Examples include reduced power consumption of hardware and hardware tools, and reduced complexity of algorithms


Tasks include, but are not limited to:

  • The coordination of activities verifying the consistency of SPNE Recommendations
  • Develop guidelines on the preferred locations of SPNE in networks
  • Addressing performance issues between SPNE and other voiceband traffic types including text telephony
  • Develop draft new Recommendation(s) on control logic for SPNE and between SPNE and terminals; on mechanism for dynamic coordination of SPNE to achieve optimal end-to-end voice quality; and on provision of information and requirements for SPNE
  • Maintain and further develop ITU-T Recommendations G.161, Q.115.x-series and G.776.1

An up-to-date status of work under this Question is found in the SG 16 work programme (




  • G.108.2, G.114, G.131, G.136, G.16x-series, G.173, G.175, G.177, G.72x-series, G.76x-series, G.799.1/Y.1451.1, G.827, G.828, P.330, P.340, P.342, P.501, P.502, P.82, P.84, P.800, P.831, P.835, P.840, Q.50-series, S.1522, T.30, V.18, V.2x-series, V.32, V.34, V.150.1


  • 15, 16/16 on network signal processing
  • 3/16 on media gateway control
  • 7, 9, 10/16 on speech coding algorithms
  • 14/16 on voiceband signal compression protocols

Study Groups:

  • ITU-T SG 2 on operational aspects of networks and performance and network management
  • ITU-T SG 11 on signalling requirements and protocols
  • ITU-T SG 12 on speech performance
  • ITU-T SG 13 on IP-based networks, NGN and internetworking
  • ITU-T SG 15 on core network architecture, and management and control of transport systems and equipment
  • ITU-R SGs 4 and 5 on voice on mixed terrestrial/satellite networks

Other Bodies:

  • ETSI
  • IP/MPLS Forum on ATM, MPLS and frame relay transport
  • IETF on IP transport, applications, speech service control, and operation and management


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Updated : 2008-12-05