Unhappy modem for I9305


This rom is super but I have some problems with wifi and data.
I leave in France and Spain.
Wifi : to connect it I need to have close to the router. Both country.
Data: no problem in France, but when a spent the frontier, I lost data access. I try with a different SIM card. But 3 weeks before I had data...??¿¿¿

Its a problem of modem or kernel?