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Hi Jeff,<br>
<br>
Inline, ws.<br>
<br>
Jeff Ruttman wrote:
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<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">Thanks Wes. </font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">Well I've expanded echo
cancellation on the gateway. (PRI with MGCP, CCM6.1) So your first
paragraph is saying that most likely echo is generated too "far away"
(too much delay) from my GW to cancel the tail end echo coming into our
system--even with my expanded echo cancellation in place. So only the
telco might have a chance of cancelling that echo "closer to" the echo
source.</font></span></div>
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ws: echo is generated too far from the ipphone, like at the the other
endpoint. If you call me and hear your own voice then most likely the
echo is being generated in my phone. Your gateway is closest to me so
will have the best chance of canceling the echo as the original signal
and echo signal are closest in time in your network at the gateway.
But, in the end, it really is a problem with my customer premise
equipment (CPE). I should be canceling the echo. The best place to fix
it is in my network. Next best is in the carrier, next is in your CPE.<br>
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<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">As I understand it, I might also
change phone loads (hence my question about 7911s). And I might try
some gain/attenuation settings on the GW as well--or so I've read.</font></span></div>
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ws: Yes, there is tuning on the gateway to get the most out of the
available ecans. If the echo is coming back within the cancellation
coverage then you just need to get levels and ERL in line so the ecans
can do their jobs.<br>
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<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">So in a VOIP system that has
echo, I can:</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">1. Bug the telco</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">2. Expand echo cancellation on
the GW</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">3. Attenuation/gain statements
on GW</font></span></div>
</blockquote>
There are several parameters on gateways for possible tuning. These
include:<br>
ecan coverage<br>
NLP - non linear processor<br>
ERL - echo return loss - primarily affected by Input Gain and Output
Attenuation<br>
Noise - any noise introduced on the circuit causes the echo signal to
not match the original signal. This prevents echo from being detected
and canceled. Examples of noise include any slips or errors on T1's
and electrical cables (60Hz, fluorescent lights especially) located too
close to analog (FXS/FXO) connections. I believe the parameters are
covered pretty well here:<br>
<a class="moz-txt-link-freetext" href="http://www.cisco.com/en/US/customer/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml">http://www.cisco.com/en/US/customer/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml</a><br>
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<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">4. Change phone load</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">At least so far that's all I've
found I can tinker with. Is that about it?</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">Anyone use attenuation or gain
statements on their GWs? I know the statements, but I don't know what
their function really is, whether I would use one or the other or both,
or what I would set them to.</font></span></div>
</blockquote>
ws: see the article above. Use IG and OA to get ERL that works for
ECAN.<br>
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<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">Thanks</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"><font
color="#0000ff" face="Arial" size="2">jeff</font></span></div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<div dir="ltr" align="left"><span class="263310719-31082010"></span> </div>
<br>
<div class="OutlookMessageHeader" dir="ltr" align="left" lang="en-us">
<hr tabindex="-1"><font face="Tahoma" size="2"><b>From:</b> Wes Sisk
[<a class="moz-txt-link-freetext" href="mailto:wsisk@cisco.com">mailto:wsisk@cisco.com</a>] <br>
<b>Sent:</b> Tuesday, August 31, 2010 2:00 PM<br>
<b>To:</b> Jeff Ruttman<br>
<b>Cc:</b> Cisco VOIP<br>
<b>Subject:</b> Re: [cisco-voip] Echo Cancellation and 7911 Phone
Loads<br>
</font><br>
</div>
Talker echo is usually caused by echo at far end tail circuit. With
VOIP that delay is going to be too long for the talker's phone to
cancel. It will have to canceled closer to the source of the echo.<br>
<br>
Otherwise, AFAIK, all cisco phones (except soft) have local ecan to
prevent speaker audio from going back into mic.<br>
<br>
<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.voiptroubleshooter.com/problems/echo.html">http://www.voiptroubleshooter.com/problems/echo.html</a><br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.cisco.com/en/US/partner/docs/ios/solutions_docs/voip_solutions/EA_ISD.html">http://www.cisco.com/en/US/partner/docs/ios/solutions_docs/voip_solutions/EA_ISD.html</a><br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml">http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml</a><br>
<br>
/Wes<br>
<br>
Jeff Ruttman wrote:
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<div><span class="997510914-31082010"><font face="Arial" size="2">Greetings,</font></span></div>
<div><span class="997510914-31082010"></span> </div>
<div><span class="997510914-31082010"><font face="Arial" size="2">Can
someone confirm or deny my memory? I recall reading that phone loads
for 7911 phones don't really contain echo cancellation programming. In
looking now, I can't find much info on echo cancellation in relation to
different phone models/loads in general and nothing on 7911s.</font></span></div>
<div><span class="997510914-31082010"></span> </div>
<div><span class="997510914-31082010"><font face="Arial" size="2">We
have an office mostly full of 7911s recently complaining of talker
echo. There are loads out on cisco.com newer than the ones we're
using, and while it's not hard to change phone loads, it would be
pointless to do it if the phone loads don't contain echo cancellation.</font></span></div>
<div><span class="997510914-31082010"></span> </div>
<div><span class="997510914-31082010"><font face="Arial" size="2">Any
insight?</font></span></div>
<div><span class="997510914-31082010"></span> </div>
<div><span class="997510914-31082010"><font face="Arial" size="2">Thanks</font></span></div>
<div><span class="997510914-31082010"><font face="Arial" size="2">jeff</font></span></div>
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