Intermittent no Audio on Inbound calls from certin cellular carriers to 3300Mxe with PRI

[Hawaii5O]

Has any one experienced issues with inbound calls from Cellular networks to an 3300Mxe MCD 8.1 Controller with PRI? Users have reported Intermittent no audio on inbound calls from people on cell phones. An inbound call is made to a DID on the system, the Mitel user answers the call but no audio both ways. The outside caller does not even hear ringing when placing the call. Both parties assume no one is there and they hangup. Outside caller calls back in and gets connected normally. We had assumed it was a particular trunk but causing the issue but found that it happened on multiple trunks. Also found that issue could be duplicated by calling in with certain Cellular carriers. Could not duplicate issue when calling in with a Landline. Reported issue to telco and they said it was the PBX. Reported issue to Mitel Support and they said could be internal IP network related.

 

[Billz66]

how is the ISDN delivered ?
is it via a SIP IAD ?
might be a codec issue
carriers in AU are replacing ISDN with SIP delivered to a SIP-ISDN convertor which is then connected to the Pabx
if its only happening on cellular calls and calls from landlines are ok , its sounding like a carrier issue

If I never did anything I'd never done before , I'd never do anything.....

 

[Hawaii5O]

Type II PRI from Telco smart jack.
Telco NOC mentioned the same thing about the CODEC mismatch. Is there a way to force a particular codec on the PRI?

 

[Billz66]

as far as i am aware on the MIVb the codec is fixed for ISDN based on location
- in AU it would be g711 alaw

the only reason i mentioned the codecs is that with sip there are lots of issues with mismatched codecs

if it was TELCO----sip-----IAD--isdn--MIVB
the the sip leg could be using G729 or another compressed codec that was causing the issue

if its direct ISDN then thats not really a viable reason for the problem
I still think its sounding like a carrier issue - perhaps some of their calls are routing internally in their network via different equipment( and causing the issue)

long shot but it could be a faulty ISDN card in the MIVB - doesnt really explain why its only Mobile calls


If I never did anything I'd never done before , I'd never do anything.....

 

[nytalkin]

We had a similar problem with PRI delivered on IAD. Carrier had to make changes to config in IAD.

I suppose you're entitled to your opinion, I'm just not going to suppose very hard.

 

[Hawaii5O]

So by Carrier do you mean my telco provider to the PBX or Carrier of the Mobile phones? Is it possible to see the codec negotiation in the ISDN messages during a cal setup?