“…The proposal of beamspace mMIMO systems using a lens antenna array, hybrid precoding, and beam selection have considerably reduced the number of RF blocks in mmWave mMIMO systems with no apparent performance loss [ 2 , 3 , 4 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], but the maximum number of MUTs that can be supported at the same time and frequency resources cannot surpass the number of available RF blocks [ 2 , 3 , 4 , 7 , 9 , 13 , 16 ]. To overcome this limitation, NOMA has been incorporated into beamspace mMIMO systems to allow multiple MUTs to be served simultaneously in the same RF block [ 1 , 2 , 3 , 4 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 17 ].…”