On Generalized Downlink Beamforming with NOMA
"Recently, nonorthogonal multiple access (NOMA) has
been studied to increase the spectral efficiency of downlink in a
multiuser system by exploiting the notion of superposition coding
with successive interference cancellation (SIC). NOMA can be
employed with downlink beamforming for downlink transmissions
from a base station (BS) equipped with an antenna array, which
results in NOMA beamforming. In this paper, we formulate a multiuser
NOMA beamforming problem as a semidefinite programming
(SDP) problem and generalize it in order to include the conventional
(multiuser) beamforming. A low-complexity approach to
decide SIC sets for the generalized NOMA beamforming is studied
using the correlation between channel vectors for better performance.
From analysis and simulation results, we show that
the (generalized) NOMA beamforming can outperform the conventional
beamforming, especially under limited scattering environments."