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New Member

Struggling with Echo issues

1751v Router w/2 2port DID VIC's

I'm attempting to troubleshoot the sporadic voice issues one of my remote offices are having, but I've read so many support docs that I?ve got myself confused. The most common issue reported is echo. The people on the IP side of the legs are hearing the echo, not the outside (analog).

My voice ports are setup as follows:

voice-port 1/0

input gain -3

echo-cancel coverage 48

no vad

no comfort-noise

timing dialout-delay 300

I've been reading through an impedance troubleshooting doc and I'm concerned about the ERL levels that are being reported.

I make a test call via a typical outside analog line to a DID number in that office. then, I issue a test tone sweep on that particular port and here's what I see:

A-1751#test voice port 1/1 inject-tone network sweep 200 0 0

Freq (hz), ERL (dB), TX Power (dBm), RX Power (dBm)

104 -79 -82 -3

304 -79 -82 -3

504 -79 -82 -3

704 -79 -82 -3

904 -79 -82 -3

1104 -79 -82 -3

1304 -79 -82 -3

1504 -79 -82 -3

1704 -79 -82 -3

1904 -79 -82 -3

2104 -79 -82 -3

2304 -79 -82 -3

2504 -79 -82 -3

2704 -79 -82 -3

2904 -79 -82 -3

3104 -79 -82 -3

3304 -79 -82 -3

3404 -79 -82 -3

Those ERL values aren't even close to what the troubleshooting docs recommend. I've tried all 5 impedance settings as well as changing the input gain, output attenuation, and the echo-coverage to try and eliminate the echo problems..

Do those ERL levels (-79) look normal to anyone?? Any advice on what I should do next to get to the bottom of this echo problem?

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2 REPLIES
Blue

Re: Struggling with Echo issues

ERL needs to be approx. 6db or higher than the signal of the talker for the ECAN to engage. usually 15db-20db is standard'ish.

looks like you have -79db ERL which is WAAAY to low! the ECAN thinks this is voice as far as i can tell so no cancellation is occuring. is this correct? or do you notice some cancelation?

if you can, try the extended echo canceler htat has a tail coverage upto 64ms. (different IOS implement differntly so confirm for your version)

or, try to generate tone to measure out/in & ERL with this method: (sounds like you need to lower inputGain perhaps a bit more and raise outputAttenuation in this case)

Press the Settings button on the IP phone to enter the Settings menu in order to enable the tone generator. This enables the Tone softkey for as long as this phone is registered to Cisco CallManager.

Press **##**3 on the Cisco IP Phone 7940 or 7960 keypad while the phone is not on a call. When you go to Option 5 "STATUS", you should see more debug information (for example, Stack Statistics, and Debug Display).

Note: From Load #P0030301ESP5, you need to unlock the phone first, then you can press **##**3. You need to be careful because if you press **#** consecutively, you reset the phone (because of the **#** sequence).

This enables the Tone softkey for as long as this phone is registered to Cisco CallManager.

Place a call to the source phone with the echo problem.

Once the call is established, press the "i or ?" button twice. This brings up the statistics for the call.

Note: If the **##**3 key sequence works, you should have a Tone softkey available. Press the Tone softkey and the phone begins to generate a 1004 Hz tone at -15 dB. The only way to stop the tone is to end the call.

Set the input and output levels to 0 dB gain/attenuation in order to make sure that you start with a cleared configuration.

Once the tone is generated, keep the call up, then perform the remaining steps to measure the decibel levels.

Use the "show call active voice" Cisco IOS command to view the input and output levels for your call.

This output is a call to a loopback number that echoes back whatever is sent with no attenuation.

Gateway#show call active voice

!--- snip

OutSignalLevel=-15

InSignalLevel=-15

ERLLevel=25

!--- snip

The test tone is output as -15 and is looped back with 0 dB loss. Therefore, it comes back at -15 dB. The ERL value here has no significance at this point since the echo canceler does not consider the input signal to be echo.

Note: The OutSignalLevel shows the value of the level after the output attenuation is applied to the signal. The InSignalLevel shows the value of the level after the input gain is applied.

If you configure 1 dB of attenuation in each direction, as this output shows, the resulting levels decrease, shown in the example immediately after the configuration example.

voice-port 1/1:15

input gain -1

output attenuation 1

Gateway#show call active voice

!--- snip

OutSignalLevel=-16

InSignalLevel=-17

ERLLevel=11

!--- snip

The OutSignalLevel is -16 because you attenuated the -15 dB signal by 1 dB. The InSignalLevel is -17 dB due to the input gain of -1. At this point the real ERL is 2 dB. However, the echo canceler still does not acknowledge the input signal as echo.

see this link for more info: (if you haven't already)

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml

New Member

Re: Struggling with Echo issues

Thanks for the reply.

Yeah, I've been through the link you provided there numerous times.

No matter what I do with th input gain and output attenuations, the ERL from the tone sweep just gets worse. as in -81, -83, and up! Not good! I have no idea why it's so low..

Is there an actual command to view if ecan is indeed in action, or do you just have to determine it via the insignal/outsignal values?

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