Concealment Frames and so on

Unanswered Question
Oct 24th, 2008
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Hi eXpert,

I need your help to solve a problem,

or better "understand" that problem.

We have a Cluster Toip based on CCM 5 and it works so good, but we are in trouble with this kind of phone calls:

we have a VoiceGateway that support 2 PRI channel towards PSTN network, ending

into Carrier network that provide us connectivity to the cellular (umts and gsm) network; well, every calls directed to an enterprise cellular phone number is redirected by CCM toward this VG and all the other ip phone calls are managed in different manner.

So, we have a quality problem with all calls directed to enterprise cellular number. Mos is near 2 or 3 maximum and inspecting CDR and low quality reason we have no evidence about data network issue.

What I mean is that, if you inspect CMR regarding a single very bad cellular call phone you will not find Jitter or Packet Loss or Latency-Delay issue.

They are all near to 0, in the same way

as the other "normal" calls to non-mobile devices.

But MOS is very different and low.

What I can understand is that a parameter called "Concealment Frames" is crucial for this analisys, cause is the only one who change in a negative manner

if compared to normal calls to ip phone non-mobile.

So, we have a great amount of these Concealment Frames, and now, what does it mean ? which are the possible reasons for that ? what king of troubleshooting can we fire to find the originating device or path or other ?

Thank you very much 4 your appreciated answers in advance.


Federico

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sbilgi Sun, 11/02/2008 - 17:26
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Mean Opinion Score (MOS) Listening Quality K-factor (LQK) is the calculated score based onconcealment frames within an initial 8-secondinterval that is updated each succeeding second during a single voice stream.The DSP plays concealment frames to mask frame loss in the voice packet streaTo measure the voice quality of calls that are sent and received within the network, Cisco Unified IP Phones use these statistical metrics that are based on concealment events.



_cisco4ever Sun, 11/02/2008 - 22:17
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Thank you sbligi,

your explanation is clear but what do you think

about packet loss ? If there is "frame loss", and we are sure cause to high concealment frames value, would not we see increasing "packet loss" in the same conversation ?


regards

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