In case if it is one site
More than one site and it happens intermittently
On Zte its very rare you get mute call. If it is you can check packet loss, any issue of transmission.
Most probably transmission issues
Can transmission issues like high BER cause it?
Yes, they can
Or faulty stm
And on what scenarios these happens?
At times one way at times 2 way
is this GSM?
Yes it is GSM
Are those mute calls made within the home network or are made inter-network?
I think yon need to check is the AMR codec mode sets are aligned.
It is also possible that there is some problem on MGW side, so ask CN guys to help investigate this issue.
Dear experts,
What are the main causes for LTE silent call and how to analyze cases?
They are most often caused by transmission issues. Approach your RAN and Tx team to help out.
Is there any tool for analyze single user trace cases?
What are the main reason behind Silent calls on BSC level (Ericsson)?
Please how can i troubleshoot silent calls using U2020 for nodeB?
Please check my reply here (for your same query): KPIs/Counters to check mute call - #26 by CarlosFuente
Have you checked Null NRI values , is pilot site and some rollout ?