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Question 8/15 - Interaction aspects of signal processing network equipment

(Continuation of part of Question 8/15 and additional aspects)

Background and justification

Signal Processing Network Equipment (SPNE) is an integral part of communication networks. SG 15 has developed Recommendations on Circuit Multiplication, Speech Enhancement (Network Echo Cancellers and Automatic Level Control), and GSTN/IP Gateway Equipment. This Question deals with the study of interoperability of SPNE, between different SPNE, and between SPNE and existing and/or new voice-band traffic technologies, including interactions between acoustic echo controllers and network equipment. Its main purpose is to ensure the correctness of Recommendations in the area of Signal Processing Network Equipment, and to provide a discussion platform for interoperability and interaction concerns.

Responsibility under this Question includes those Signal Processing Recommendations not covered by Questions 5, 6, 7/15.


  • What interactions occur between similar and different SPNE?
  • What interactions occur between voice-band signals and SPNE?
  • What interactions occur between SPNE and end-terminal equipment?
  • What techniques should be used to ensure high-quality SPNE recommendations?

Study items

Study items to be considered include:

  • The availability of general evaluation procedures
  • Interaction concerns between similar and different SPNE, and between SPNE and/or existing new voice-band traffic technologies
  • The evaluation of corresponding ITU-T Recommendations
  • The interaction of acoustic echo control devices with SPNE
  • The effect of tandem coding avoidance (vocoder bypass or TFO) on in-path SPNE

Specific tasks

  • The coordination of any activities verifying the quality of the Recommendations
  • Addressing performance concerns between Recommendations involving SPNE and new or existing voice-band traffic types


  • Other questions of ITU-T SG 15 as relevant
  • ITU-T SG 2 on dimensioning
  • ITU-T SG 8 on facsimile
  • ITU-T SG 11 on signalling interfaces
  • ITU-T SG 12 on speech performance
  • ITU-T SG 13 on network implications
  • ITU-T SG 16 on modems and encoding algorithms
  • ATM Forum and IETF
  • ITU-R SG4 WP4B on voice on mixed terrestrial/satellite networks


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Updated : 2004-10-21