Holographic MIMO NOMA Communications: A Power Saving Design

The downlink non-orthogonal multiple access (NOMA) transmissions from a holographic multi-input multi-output surface (HMIMOS) transmitter to multiple single-antenna users are investigated in this work. And we focus on the power saving design when the HMIMOS has a massive number of elements. For single-cluster NOMA transmissions implemented by a single-RF-chain HMIMOS-based transmitter, the required transmit power to maintain the quality of service (QoS) of all users are derived and two holographic beamforming schemes aiming at minimizing the required transmit power are developed. For multi-cluster NOMA transmissions implemented by a multi-RF-chain HMIMOS-based transmitter, a two-layer partitioning problem is formulated and solved to minimize the power consumption. Numerical results are provided to validate our theoretical analysis. It is shown that the NOMA scheme has lower power consumption than orthogonal multiple access (OMA) based multi-user transmission schemes when the number of RF chains is limited, and our proposed holographic beamforming schemes achieve lower power consumption than other holographic beamforming schemes.