  Non-orthogonal multiple access (NOMA) has been recently considered in
millimeter-wave (mmWave) massive MIMO systems to further enhance the spectrum
efficiency. In addition, simultaneous wireless information and power transfer
(SWIPT) is a promising solution to maximize the energy efficiency. In this
paper, for the first time, we investigate the integration of SWIPT in mmWave
massive MIMO-NOMA systems. As mmWave massive MIMO will likely use hybrid
precoding (HP) to significantly reduce the number of required radio-frequency
(RF) chains without an obvious performance loss, where the fully digital
precoder is decomposed into a high-dimensional analog precoder and a
low-dimensional digital precoder, we propose to apply SWIPT in HP-based
MIMO-NOMA systems, where each user can extract both information and energy from
the received RF signals by using a power splitting receiver. Specifically, the
cluster-head selection (CHS) algorithm is proposed to select one user for each
beam at first, and then the analog precoding is designed according to the
selected cluster heads for all beams. After that, user grouping is performed
based on the correlation of users' equivalent channels. Then, the digital
precoding is designed by selecting users with the strongest equivalent channel
gain in each beam. Finally, the achievable sum rate is maximized by jointly
optimizing power allocation for mmWave massive MIMO-NOMA and power splitting
factors for SWIPT, and an iterative optimization algorithm is developed to
solve the non-convex problem. Simulation results show that the proposed
HP-based MIMO-NOMA with SWIPT can achieve higher spectrum and energy efficiency
compared with HP-based MIMO-OMA with SWIPT.
