A joint scheduling and millimeter wave hybrid beamforming system with partial side information

The digital-analog hybrid beamforming technique with a number of antennas is necessary for the millimeter wave (mmWave) communications to overcome both high complexity of large array system and high path loss of mmWave signals. Since the hybrid beamforming system has multiple radio-frequency (RF) chains, the simultaneous transmission is possible which is known as the space division multiple access (SDMA). However, we cannot apply the digital precoding schemes to the hybrid beamforming system due to the hardware constraints of RF beamforming matrix. In this paper, we propose a joint scheduling and hybrid beamforming system with partial side information. Then we provide the achievable sum rate upper bound and the scaling law of the asymptotic sum rate. It is shown that our system can take advantage of the same multi-user diversity gain with the digital system. Interestingly, the proposed hybrid system outperforms the digital system in the low SNR regime which is suitable for mmWave channel.