  We propose a novel nonorthogonal multiple access (NOMA) scheme referred as
adaptive constellation multiple access (ACMA) which addresses key limitations
of existing NOMA schemes for beyond 5G wireless systems. Unlike the latter,
that are often constrained in choices of allocation of power, modulations and
phases to allow enough separation of clusters from users combined signals, ACMA
is power, modulation and phase agnostic forming unified constellations instead
where distances of all possible neighbouring points are optimized. It includes
an algorithm at basestation (BS) calculating phase offsets for users signals
such that, when combined, it gives best minimum Euclidean distance of points
from all possibilities. The BS adaptively changes the phase offsets whenever
system parameters change. We also propose an enhanced receiver using a modified
maximum likelihood (MML) method that dynamically exploits information from the
BS to blindly estimate correct phase offsets and exploit them to enhance data
rate and error performances. Superiority of this scheme, which may also be
referred to as AC NOMA, is verified through extensive analyses and simulations.
