It’s been a long time, but now I am back!
Dear Pix you are right about tch drop and congestion when we talk from Alcatel point of view. But in ericsson the counter of TCH Drop [TNDROP] increment with another counter [TNRELCONG] that increment upon congestion on TCH Transcoder or Ater during assignment to better or worst cell. so the correct equation for call drop rate must be adjusted to be as following: 100 * (TNDROP – TNRELCONG)/(TCASSALL + ((SUMIHOSUCC – SUMIABSUCC – SUMIAWSUCC ) – (SUMOHOSUCC – SUMOABSUCC – SUMOAWSUCC))))
to reply for Sam questions:
subscriber tch drop must be the above equation, while the other tch drop rate is calculated without taking into consideration the TNRELCONG and HO and AB and AW.
also note tch drop due to sudden loss is not related to tch congestion… as i mentioned above, counter TNDROP increases with TNRELCONG.
I hope i made it clear.