In this paper, the downlink beamforming algorithms for
multi-user hybrid MISO-NOMA systems is considered.
Firstly, the concept of quasi-degradation and the closedform
H-NOMA precoding algorithm are revisited concisely.
Secondly, by combining ZFBF and the H-NOMA precoding
algorithm, an intra-cluster beamforming algorithm, termed
PH-NOMA, is introduced, to minimize both inter and intra
cluster interference. Thirdly, by adopting the properties of
quasi-degradation, two user pairing algorithms, termed PBPA
and IBPA, are proposed, to handle the cases N ≥ K − 1 and
N ≥ K, respectively, where N is the number of transmit
antennas at the base station (BS), and K is the number of
users (assumed to be a even number). Consequently, the proposed
low-complexity beamforming algorithms are obtained,
by combining PH-NOMA and PBPA/IBPA. Moreover, the
performance analysis is provided to show that the proposed
beamforming algorithms are superior to conventional ZFBF
in terms of outage performance as well as diversity. Finally,
simulation results demonstrate the efficiency of the proposed
beamforming algorithms and the correctness of the performance
analysis. The contributions of this paper are listed as
follows: