PRI echo

Unanswered Question
Feb 13th, 2007

We have a new CCM 5 installation with a pri...the customer has reported problems with echo...we are in the process of getting data from calls that have echo but since the problems are sporatic we are not able to get alot of good data...

This is the output of a show call active voice a call that had a test tone generated on it...

TxDuration=114875 ms

VoiceTxDuration=114875 ms

FaxTxDuration=0 ms

CoderTypeRate=g711ulaw

NoiseLevel=-82

ACOMLevel=63

OutSignalLevel=-15

InSignalLevel=-79

InfoActivity=1

ERLLevel=45

EchoCancellerMaxReflector=4

The setting on voice-port are input gain -3 ...my main issue is why is the

InSignalLevel=-79 such a large number...I would think this would -18...

From my understanding echo on a pri is not common...am I missing something...

Joe

I have this problem too.
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joeharb Thu, 03/15/2007 - 13:35

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dgahm Thu, 03/15/2007 - 16:21

Joe,

The -79 is actually a very low level as the reference is 0db. The OutSignalLevel is your test tone.

On our IOS gateways with PRIs I have found that the worst case erl needs to be changed from the default 6db to 3 in order to eliminate all echo problems. This means that a echo signal 3db or more below the transmit level will be cancelled.

voice-port 1/0:23

echo-cancel erl worst-case 3

It is the far end termination of the call that causes echo. So if you place a call over your PRI that terminates on another PRI it would be unusual for you to hear echo. If you place a call over your PRI that terminates on an analog line with bad return loss (high reflection) you will hear echo.

Here is a good doc:

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

Please rate helpful posts.

Dave

e.huntley Tue, 04/17/2007 - 11:17

Go into your router and do:

show voice dsp detailed. You will see a version of your DSPWare firmware. If it is 4.4.19 or prior, there is a known bug that causes echo under certain conditions.

joeharb Tue, 04/17/2007 - 11:26

I noticed the bug when started troubleshooting this issue...unfortunately we are not affected:

DSP DSP DSPWARE CURR BOOT PAK TX/RX

TYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABRT PACK COUNT

===== === == ======== ======= ===== ======= === == ========= == ==== ============

C5510 001 01 {flex} 4.4.20 alloc idle 0 0 0/0/0 02 0 5734/0

C5510 001 02 {flex} 4.4.20 alloc idle 0 0 0/0/1 06 0 2726/0

C5510 001 03 {flex} 4.4.20 alloc idle 0 0 0/0/2 10 0 2956/0

C5510 001 04 {flex} 4.4.20 alloc idle 0 0 0/0/3 14 0 2394/0

Thanks,

Joe

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