Beamforming for Combating Inter-cluster and Intra-cluster Interference in Hybrid NOMA Systems

Abstract

In this paper, downlink beamforming (BF) for hybrid
non-orthogonal multiple access (NOMA) systems is considered,
in order to combat inter and intra cluster interference.
Firstly, to minimize the inter and intra cluster interference,
the Projection Hybrid NOMA (PH-NOMA) beamforming algorithm
is introduced, by combining conventional zero-forcing
beamforming (ZFBF) and Hybrid NOMA (H-NOMA) precoding.
Secondly, to further reduce the overall interference, two user
pairing algorithms, termed Projection Based Pairing Algorithm
(PBPA) and Inversion Based Pairing Algorithm (IBPA), are
also proposed, by adopting the properties of quasi-degradation
developed previously. Consequently, the proposed beamforming
algorithm is obtained by combining PH-NOMA and PBPA/IBPA.
Moreover, the system performance in terms of outage probability
and diversity is analyzed for both the proposed beamforming
algorithms and conventional ZFBF. Finally, computer simulations
are conducted to demonstrate the efficiency of the proposed
beamforming algorithms and to validate the correctness of the
performance analysis.