Relation of SDCCH Drops with N200

Hi Everyone,

I have a query related to SDCCH Drops. In my network (ZTE BSC ZXUR-9000), I increased value of N200 from 1 to 4 for SACCH, FACCH F/H, Establish and Release to optimize TCH Call drops due to T200 expiry. Significant improvement in TCH drops has been observed but on other hand SDCCH drops have been increased. I changed N200 for SDCCH from 1 to 4 as well but no improvement. All SDCCH drops are due to Radio link Timeout. In addition, I have also observed 1s increase in TCH Mean holding time and SDCCH mean holding time is stable.

Some timers values in my network:

T3101: 2sec
T3103: 10 sec
T3107: 10 sec

Can you please guide me that why increase in N200 is impacting SDCCH drops? any additional timer I am missing?