Performance of Fully Digital Zero-Forcing Precoding in mmWave Massive MIMO-NOMA with Antenna Reduction

Fully digital precoding has superior performance for millimeter wave (mmWave) multiple input and multiple output (MIMO) system. In fully digital precoding, each antenna is connected to one RF chain which results in high hardware complexity and high cost. Non-orthogonal multiple access (NOMA) is one of the promising techniques in future mobile communication. In this paper, we propose a fully digital mmWave massive MIMO system with a reduced hardware complexity and reduced energy consumption. The proposed system reduces the number of antennas and consequently the number of RF chains by applying a three stages antenna reduction algorithm. Moreover, a clustering algorithm is proposed in which users within same group are highly correlated, and users in different groups have low correlation with each other. The performance of the proposed system is evaluated in terms of energy efficiency and spectral efficiency. Numerical results show that the proposed system has superior performance in terms of energy efficiency at the expense of slight decrease in spectral efficiency.