OPTICOM ECHO Datasheet

Advanced Perceptual
ECHO Measurement Tool
OPTICOM's Advanced ECHO measurement tool
provides accurate and repeatable estimates of
multiple audio signal echoes in a telephony net-
work. Each detected echo is characterized by an
Echo Return Loss (ERL) and its echo delay plus it
is tested whether each echo is likely to be per-
ceived as acceptable or annoying by a customer.
The ERLs and the echo delays are measured by
analyzing audio signals sent (reference audio
signal) to and received (echo audio signal) from a
network.
Principle
Echo caused by conversion
from 4-wire to 2-wire
A coupling and vice versa
near end side
IN
(electrical or
acoustical)
OUT
(electrical or
acoustical)
Sidetone -
Echo which is supposed
to improve the talking quality
OPTICOM's Advanced ECHO algorithm deter-
mines the echoes with the help of long term cor-
relations of the speech signals at a voice net-
work's input and output (see figure above). One
advantage of using real voice signals over ordi-
nary sine tones – as other algorithms propose –
is that a voice signal is closer to the real world
telephony situation. Sine tones might be treated
more or less rigid by a network compared to real
voice signals. For example echo cancellation
devices employed in the network might be able
to easily filter out detected sine tones but they
might have difficulties handling a complex voice
PEVQ™, 3SQM™ and the OPTICOM logo are registered trademarks of OPTICOM GmbH; the 'single-sided speech quality measure' and
'the perceptual quality experts' are trademarks of OPTICOM GmbH. This information may be subject to change.
All brand and product names are trademarks and/or registered trademarks of their respective owners.
All rights reserved. Copyright © 2005 OPTICOM GmbH – www.opticom.de
The Advanced ECHO measurement technology is
the latest out of OPTICOM's family of products
for network quality assessment tools. Compared
to other echo measurement algorithms OPTI-
COM's approach is unique because it uses real
voice signals for the measurement rather than
e.g. sine tones. OPTICOM's ECHO tool can be
widley used in active testing in both lab environ-
ments and in network test equipment.
sending path
2-wire /
2-wire /
Network
4-wire
4-wire
receiving path
like signal. Using real speech signals for the
measurement becomes even more valuable in
digital e.g. VoIP networks, where signal delays
increase due to the additional requirement for
signal processing and without active echo can-
cellation methods or suppressors the echo signal
would return to the talker annoyingly unattenuat-
ed. Another advantageous side effect is that
through the speech signal's natural modulation a
best match of the two correlated signals can be
found with higher accuracy than with sine tones.
Therefore the results become more robust
against clipping and noise.
Voice
Quality Testing
OPTICOM Product Line:
Voice/Audio Quality
PESQ ITU-T P.862
3SQM ITU-T P.563
PSQM ITU-T P.861
ECHO
PEAQ ITU-T BS.1387
Video Quality
PEVQ
Network Quality
VQmon
Key Features:
• Echo Return Loss (ERL)
B
and echo delays
far end side
• OEM product available as
DLL/Library optimized in
performance and memory
requirements
• Detailed statistics of the
occurrence of echoes for
e.g. comprehensive graph-
ical display and further
analysis
Echo caused by
acoustical coupling
• Robust measurements
at site B
even if the echoes are
heavily distorted
• Multiple echo detection