First point is to check coverage and signal strength. You may have a change with your "anchor" (G)MSC. As you have a secured TCH end users may be suffering from fading, etc..
Check if there was any recent Cell Planning and whether any changes were made to the RF Network.
As you have ZTE, Ericsson and Nortel (CDMA??) check for the last set of integration / Handover test results and whether any issues were flagged.
Topi - 1st February 2017 (05:23 GMT)
I have three networks,viz. Zte,erisson both are 3g,nortel2g in a closed locality .. Here there are always handover probs,missing part of a call during a conversation etc. , where should i check for the anomalies ?