  DVB-S2 and DVB-SH satellite broadcasting standards currently deploy 16- and
32-amplitude phase shift keying (APSK) modulation using the consultative
committee for space data systems (CCSDS) mapping. Such standards also include
hierarchical modulation as a mean to provide unequal error protection in highly
variable channels over satellite. Foreseeing the increasing need for higher
data rates, this paper tackles the optimization of 64-APSK constellations to
minimize the mean square error between the original and received symbol.
Optimization is performed according to the sensitivity of the data to the
channel errors, by means of genetic algorithms, a well-known technique
currently used in a variety of application domains, when close form solutions
are impractical. Test results show that through non-uniform constellation and
asymmetric symbol mapping, it is possible to significantly reduce the
distortion while preserving bandwidth efficiency. Tests performed on real
signals based on perceptual quality measurements allow validating the proposed
scheme against conventional 64-APSK constellations and CCSDS mapping.
