thanks for this information ! that is tricky 🙂 cyclic hopping with 13 frequencies means that the SACCH is transmitted always on the same frequency.
however, the measurements by the MS are most of the time “FULL”, on all timeslots. The SUB measures are done only when the DTX is “on”.
I think the main issue is to send and receive the SACCH always on the same freq. If by any chance this frequency is interfered, then the SACCH will be lost ==> Call drop.