that’s an interesting issue..
can you do an A trace ? it could be interesting to see which part in the SDCCH phase is “slow” for that BSC.
Could you perhaps isolate some specific cells with high SD duration within this BSC ? Or are all cells having the same SD duration ?
If only few cells :
do you face TCH CONGESTION ?
could you check your TCH QUEUING counters ? (duration, usage, etc.)
what is your setting for T11 and T11 forced ?
If all cells :
I think the A trace is the only way to understand what is bugging the BSC.
– could you check processor load ?
– N7 load ?
I’m out of idea…
the SDCCH HO is not a good idea (i think), because it doesn’t take into account that the problem is on the whole BSC.
If only on few cells, yeah, that’ might worth a shot.