code rates, roll-off factors and constellations in the DVB-S2 extension
specification, DVB-S2X. Note that gr-dvbs2 is transmit only.
https://github.com/drmpeg/gr-dvbs2
https://www.dvb.org/resources/public/standards/a83-2_dvb-s2x_den302307-2.pdf
Since the specification was just released in March 2014, there
are no consumer of prosumer receivers available yet. Therefore,
the new DVB-S2X modes are not fully tested. However,
there are only minor software changes required, so confidence
is high that the new modes will work properly. Regular DVB-S2
modes have been retested to ensure there are no regression
problems.
Here's what one of the 256APSK constellations looks like in GRC.
Ron