Parameters which influenced SD drops : SDCCH Drop HO + SDCCH Drop radio + SDCCH Drop BSS
How to reduce SD Drops : you have to find out whether it is from radio, HO or BSS.
For radio, you should try to check first the TRE which has SDCCH Channel (ussually TRX 1). Then try to change SDC allocation to another TS.
What equipment do you handle? ALcatel, Ericsson?
Unfortunately, in Alcatel, I haven’t found an indicator that shows us the most SD Drops TRX contributor.
Also please check the Interference Level, either in UL or DL.
Paul C s