User scheduling algorithm for mmWave FDMA Massive MU-MIMO system with hybrid beamforming

In millimeter wave (mmWave) cellular system, the multipath nature of wireless channels and large bandwidth ensure the existence of frequency selective channels. This paper proposes user scheduling for downlink orthogonal frequency division multiple access (OFDMA) massive multi-user multiple input multiple output (MU-MIMO) system with hybrid beamforming (HB) algorithm. The analog beamforming is implemented by employing same phase shifters in the entire frequency band. Therefore the optimization of the wideband analog beamforming should consider the beam direction of multiple OFDMA users scheduled in different frequency resources. For user scheduling, firstly the users with correlated channels constitute an OFDMA user group. For a same OFDMA user group, BS allocates these frequency resources to the user with the best channel gain. Finally, spatial multiplexing users are selected to adequately utilize multiple RF chains. The proposed user scheduling algorithm can adapt to various HB algorithms. Simulation results show that the proposed user scheduling with HB can highly improve the performance of mmWave OFDMA massive MU-MIMO system.