1 Scope
2 References
3 Terms and definitions
4 Abbreviations
5 Test signals
6 Characteristics of echo cancellers
6.1 General
6.2 Purpose, operation and environment
6.3 External enabling/disabling
6.4 Tests and requirements for performance with input signals applied to
the send and receive paths
7 Characteristics of an echo canceller tone disabler
7.1 General
7.2 Detector characteristics
7.3 Guardband characteristics
7.4 Holding-band characteristics
7.5 Operate time
7.6 False operation due to speech currents
7.7 False operation due to data signals
7.8 Release time
7.9 Other considerations
8 NLPs for use in echo cancellers
8.1 Scope
8.2 General principles and guidelines
Annex A – Description of an echo canceller reference
tone disabler
Annex B – Description of a reference NLP
B.1 General
B.2 Suppression threshold (TSUP)
B.3 Static characteristics of activation control
B.4 Dynamic characteristics of activation control
B.5 Frequency limits of control paths
B.6 Testing
Annex C – Composite source signals for testing of
speech echo cancellers – Signal, description and analysis
C.1 Introduction
C.2 Composite Source Signal – General considerations
C.3 Bandlimited Composite Source Signal with speech like power density
spectrum – Practical realization for measurements of echo cancellers
C.4 Appropriate analyses to determine convergence characteristics of
speech echo cancellers using the Composite Source Signal
Annex D – Echo-path models for testing of speech echo
cancellers
D.1 Introduction
D.2 Echo path models from network hybrid simulator
D.3 Echo path models measured from telephone networks in North
America
D.4 Echo path models measured from telephone networks in Europe
Appendix I – Guidance for application of echo
cancellers
I.1 Scope
I.2 Echo control in the
PSTN
I.3 Application rules and
operational constraints
I.4 Effect of cancellers
on voice and data services
I.5 High-level speech
I.6 Network and service
evolutionary considerations
I.7 Considerations
regarding echo canceller performance during double talk
I.8 Bibliography
Appendix II – Measurement methods for characteristics
of echo paths
II.1 Introduction
II.2 Measurement procedure
II.3 Analysis of echo-path characteristics
II.4 Examples of echo path measurements from real networks
II.5 Conclusions
II.6 Bibliography
Appendix III – Multiple tail circuits
Appendix IV – Guidelines
on the use of parameters for testing echo cancellers