Half‐ZF beamforming scheme for downlink two‐user multiple input single output‐based non‐orthogonal multiple access systems

Abstract

The authors investigate the beamforming (BF) problem to minimise the power consumption for the downlink 2-user multiple input single output-based non-orthogonal multiple access system. Inspired from the conventional zero-forcing (ZF) scheme, they propose the Half-ZF scheme which only mitigates the interference introduced by the signal of the cell-interior user through the ZF method. Meanwhile, the interference introduced by the signal of the cell-edge user is removed through the SIC technology. We derive the closed-form expression for the BF vectors of the two users under the Half-ZF scheme. The optimal power consumption for the Half-ZF scheme is analysed and the corresponding solution of the BF factors are also obtained. Compared with the conventional ZF scheme, both the Half-ZF scheme and the existing quasi-degradation (QD) scheme can achieve lower power consumption than the ZF scheme. However, the Half-ZF scheme can achieve this advantage under more relaxed conditions. Consequently, the Half-ZF scheme consumes lower power than the QD scheme when combined with the ZF scheme in practical systems.