Hi Raj Kumar,
As u said, u r using 8,4,4 configuration in ur BTS then there must have (8+4+4)*8 channels with u. Now after excluding control channels u ‘ll have TCH only. Suppose if u r using 3 Control channels ( BCCH or SDCCH) then remaining tch will be 125. Now u use ur Erlang B table with blocking = 1%
channels = 125