[cisco-voip] Echo on IP Phones through PRI

Thu May 10 02:34:06 EDT 2007

try to increase your output attenuation ( you set it to -3 which is a gain of 3) play with this vlaue but with positive values not negative and it will do it for you, the echo problem is mainly affected by this value as this controls the output power off your gateway, the higher this level the higher is the reflected signal (echo) from teleco. I am assuming that the IP Phone side is the one hearing the echo.

Thanks and Best Regards

Ahmed A. Elnagar
Network Field Engineer

Advanced Computer Technology (ACT)
16 Fawzy Ramah St.Off Shehab St.Mohandessin, Giza, Egypt 
Postal Code:12411 Cairo Egypt

Mob: +2010-2833868
Website: www.act-eg.com
E-mail: aelnagar at act-eg.com

________________________________

From: cisco-voip-bounces at puck.nether.net on behalf of Rhodes, Geoff
Sent: Wed 09-May-07 10:44 PM
To: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] Echo on IP Phones through PRI

Please excuse the newbie question, but how do I determine the DSP
version my MGCP gateway is running?  It's a CMM blade in our 6509
switch.  The IOS on it looks to be 12.4(8a).  I'd like to document what
release we are running for future needs.

We get complaints ever once in a while about echo problems.  Most of the
time we blow them off unless someone is constantly complaining.

Here are our settings in CCMAdmin for the CMM Gateway:
Echo Cancellation Enable = Enable
Echo Cancel Coverage = 32
Input Gain = 3
Output Attenuation = -3

Thanks for your help.

Geoff Rhodes
Director, Information Technology
Robinson, Bradshaw & Hinson, P.A.
704 / 377-8188
grhodes at rbh.com

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Erick Bergquist
Sent: Wednesday, April 18, 2007 9:12 AM
To: Matthew Melbourne; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] Echo on IP Phones through PRI

DSP Fimware 4.4.708 has issues which can cause echo, etc. Many people on
the cisco NetPro forums have ran into echo issues with this DSP
firmware.  I don't have the exact bug id's handy, but you can try
upgrading to a current 12.4 mainline release if your routers DRAM/flash
can take it. 12.4(13a) has 4.4.23 DSP ware. So far, I have not ran into
any issues yet with DSP firmware 4.4.21 or higher in 12.4 mainline but
YMMV.

If you can't update the IOS, and I don't believe there is a newer 12.3T
release with a newer firmware embedded in it, you can get a standalone
DSP firmware image file to put on the router flash that is a newer
version from TAC.

As far as finding out what gateway a call is using, probably the
quickest way is to go to the phones web page while the call is connected
and look at the stream page for the remote IP address. Other then that,
you would need to check out CDR and/or QRT records if they use QRT
softkey, etc and go into each gateway.

----- Original Message ----
From: Matthew Melbourne <matt at melbourne.org.uk>
To: cisco-voip at puck.nether.net
Sent: Wednesday, April 18, 2007 7:50:22 AM
Subject: [cisco-voip] Echo on IP Phones through PRI

We are getting sporadic issues from users on IP phones who are hearing
echo on external calls. From this document is would suggest that echo on
IP Phones is caused by hybrid echo and not any local acoustic echo.

http://www.cisco.com/warp/public/788/voice-qos/echo_ipphone_gateway.html

The MGCP-controlled voice gateways are all running 12.3(14)T7 with DSP
firmware 4.4.708. In CallManager (4.1(3)SR2), echo cancellation is on
for each port, with a "default" echo cancellation coverage of 64ms.
Input gain and output attenuation are set to 0dB.

I have seen suggestions to include the "echo-cancel erl worst-case 3"
command on the voice ports. Can this help in situations of occasional
echo?

Are there any other parameters changes which could help? Could it be a
code/DSP firmware issue? I haven't found a specific echo-related bug
relating to this particular IOS and its embedded DSP firmware.

On occasions, the start of the call is fine but echo comes and goes
during the call.

Is there a quick way of finding out which voice gateway a call is
terminated on (we have 8, and all could be used in a round-robin fashion
for outbound calls).

Cheers,

Matt

--
Matthew Melbourne
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