Telecom Operators related Dept

Hi! please any one can explain the difference between the following terminologies or departments in more details that will my pleasure:

  1. IN Operation
  2. MSC Operation
  3. NOC Operation

    … etc.

NOC Operation would be responsible for network performance monitoring.
Usually you would have bunch of guys divided per regions and they are monitoring 24h/7/365 all alarms and major quality degradation.
If issue is simple and on small scale - they can try to solve it by their own. In all other cases they are forwarding ticket to proper team - infrastructure maintenance, transmission, RAN backoffice etc.
Usually people here may be also responsible for tracking on site activities.

Thanks, Mr. @sztab27h , for your kind information.