SIP Devices on 3300 & Distorted Voice

[LSP5400]

Hey there;

First post on this forum but have been an avid reader since installing our 3300 a while back.

We are experiencing some distortion when placing calls to external recipients using either a Spectralink 8020 on our internal WiFi or BlackBerry MVS over a SIP trunk using the mobile network. The distortion is similar to a vocoder effect and seems to only affect the person on the SIP device and not the person on the other end of the call. Often times the distortion doesn't occur until 2 or 3 minutes into the call. Sometimes a DTMF tone will cause the effect to start happening immediately thereafter. You can always get back to normal by placing the person on hold and resuming the call.

Any ideas what could be the culprit? Our external trunk is a standard Bell Canada PRI (partial T1). Calls using our Mitel sets do not exhibit this behaviour (5330's). MVS calls or 8020 calls to internal recipients are not affected either.

We have:
MCD Release 5.0 SP2 PR1
Active software load: 11.0.2.19
Platform MXe-III, 512MB RAM

30 or so SIP extensions (wireless and MVS)
60 or so internal extensions.

Thanks for any insight!

 

[ChrisvanT]

Have you taken a look at QoS?

 

[ChrisMitel]

There are some really good QOS guides on the spectralink website for different WIFI vendors. Guides you through step by step how to setup QOS properly for the 8020 handsets. I have used it for Trapeze and Cisco WIFI.

http://support.polycom.com/PolycomService/support/us/support/voice/wi-fi/view_certified.html

 

[LSP5400]

Thanks for the link. We are running a Cisco wireless environment and I have verified that the QoS and all other configuration as described in the document for the wireless network has been implemented. I'm having my network guy check out the core switch environment for voice (HP Procurve) as well to make sure that QoS is turned on properly. Are there any documents that go through the proper configuration on a Procurve switch for a Mitel environment?

Just another note that voice is completely segregated from data on our network. The only data that will be across the voice network is BlackBerry traffic to our BES from the MVS clients of which there are 20 or so connected at any one time.

One other thing, the problem came to my attention only recently and the last major change was an update to software load 11.0.2.19...apparently .24 is available. Could it be an issue with this software version? Would upgrading again be something worth trying?

 

[ChrisMitel]

It is worth checking out the release notes for known bugs and fixes. If it there is a fix it will tell you in there. Out of curiosity, I know it is a get out IT answer but have you tried a reset of the system?

 

[LSP5400]

Yes, funny enough a reset of the system tends to clear the problem up for a little while - although we've only reset once since the firmware upgrade since we are 24/7/365 shop. I'm still not convinced that this is not just a coincidence since we can't replicate the problem 100% of the time so the system reset may coincide with a period that everything works OK.

Still checking on QoS...

 

[ChrisvanT]

As i said, take a look at QoS but also double check your SIP setings as i noticed you say it only happens with the SIP clients.