Poor inbuilding CSFB Performance

[indoor]

Hello wondered if anyone else has seen the problem below and if what suggestions to fix it?

For some 2G/3G only inbuilding systems I've seen complaints of poor coverage and dropped calls. Local operator has L800 on the macro layer with U900 used for CSFB. The indoor systems then use U2100. The problem seems to be that if there is a little 4G coverage the mobile stays on the macro network and when user makes or receives a call the fall back is to the U900 on the macro. If the coverage or quality is poor they can then get dropped calls. Customer then thinks that the indoor system isn't working.

Are there any tips or tricks that can be used to improve customer perception without upgrading the inbuilding system to 4G?

[tharinduwije]

I think the best way is to isolate the specific L800 cells serving the IBS & then modify Cell Select Reselect parameters so that UEs inside will not clamp to LTE.Since CSFB defined for one specific cell relation it will be hard to match the foot prints.

[indoor]

I think the best way is to isolate the specific L800 cells serving the IBS & then modify Cell Select Reselect parameters so that UEs inside will not clamp to LTE.Since CSFB defined for one specific cell relation it will be hard to match the foot prints.

Hello Tharindwije, please excuse the stupid questions as I'm not an optimisation engineer

Which parameters need to be adjusted?
Also will this impact the L800 macro cell by making it less appealing to mobiles?