To support GFSK modulations, a higher modulation index needs to be used.
MSK is defined as a fixed modulation index of 0.25.
However, GFSK is used in many simple ISM (unlicensed) systems, where the
modulation index can vary from 0.5 to 2.0 typically. So, I would ask
how
the existing digital FM modulator blocks (such as GMSK mod) could be
used
in such case as (G)FSK. This is used in low-cost low-power simple
systems, which are not as spectrally efficient.
I have also noticed in gnuradio-companion, under Digital Modulators:
“GMSK Mod” which uses file gr-digital/python/gmsk.py, and
“GMSK Modulator” which uses file gr-digital/lib/digital_gmskmod_bc,
which
just calls digital_cpmmod_bc.cc