hi sammi,
i have another ossibilitie in my mind.actually call drops is due to signalling.if u r using 4TRX in a cell and TS0 is always reserve for control channels.if u r using 4TRX its mean u should dedicate 1 more traffic slot for SDDCH on any one frquency.and remain resrve all slots for traffic on all frequency.in onteher mean u should give one more slot to SDDCH.it will increase ur call handling capacity.
regards
mirza