TFNDROP The total number of dropped full-rate TCH in underlaid subcell.
TFNCEDROP The total number of dropped full rate TCH connections in underlaid subcell that occur when a subscriber to subscriber connection has already been established. The establishment of subscriber to subscriber connection is assured if the connection is dropped between the DTAP messages CONNECT ACKNOWLEDGE and RELEASE or DISCONNECT (whichever of RELEASE or DISCONNECT comes first). For inter BSC handovers and inter system handovers, the target BSC assumes that the call connection is already established, and the counter is incremented in the target BSC in case of dropped connection.
TCH drop is considered after sucessful TCH seizure(individually for both ends).TFNCEDROP is considered as call drop during conversation.It can also happen that the seized TCH(MOC ones) gets dropped before the subscriber to subscriber connection takes place.
i guess and according to the data we have and your answer (Bijoy)the TFNDROP will count drops while one connection is established and when both are established, while TFNCEDROP counts only drops while the 2 subscribers are established?