Think: NR with different number of slots per frame depending on mu.
The name 'subframes_per_frame' is a bit ambiguous. It is valid for LTE,
but for NR it should be 'slots_per_frame'.
For example, for sub-carrier spacing of 30KHz, we have 20 slots per
frame, so in this case subframes_per_frame = 20. In reality whatever
the numerology, there is always 10 subframes per frame in NR.
But how to name this variable which is used both for LTE and NR cases?
'subframes_or_slots_per_frame'? It's a bit long and also ambiguous.
Conclusion: no big deal I think. 'subframes_per_frame' and so be it.