Novel Structure for Uplink mmWave Massive MIMO-HBF-NOMA Systems

Massive multiple-input multiple-output (MIMO), non-orthogonal multiple access (NOMA), and millimeter-wave (mmWave) are key technologies in the upcoming beyond fifth generation (B5G)/sixth generation (6G) era. As mmWave massive MIMO will likely use hybrid beamforming (HBF) to reduce radio frequency (RF) chains without an obvious performance loss to fulfill the urgent requirement for immense connectivity and huge throughput, it is necessary to integrate mmWave massive MIMO-NOMA with HBF structure. This work devises a novel structure for uplink mmWave massive MIMO-HBF-NOMA system based on group-level successive interference cancellation (GSIC), aiming at maximizing the spectrum efficiency (SE) of the whole system. In our paradigm, users are grouped in terms of channel gain. Space division multiple access (SDMA) is deployed between users in the same group, while NOMA is applied among different groups. The analog beamforming vectors are selected through beam sweeping. An iterative algorithm is proposed to optimize the power allocation and the digital beamforming matrix. Therein, a quadratic transform (QT) algorithm is introduced to solve the power allocation and zero forcing (ZF) method is invoked to obtain the digital beamformer. According to the simulation, the novel GSIC-based structure outperforms the benchmark clustering-based successive interference cancellation (SIC) schemes in SE and energy efficiency (EE) measurably.