Beam Rotating Precoding Scheme for Millimeter-wave Massive MIMO Systems

In beam space millimeter-wave massive Multi-Input Multi-Output (MIMO) system, the power leakage problem will lead to energy loss. To mitigate this problem, Minimum Phase Error based Beam Rotating(MPE-BR) precoding scheme is proposed. Firstly, the phase shifter-based beam selection network is adopted,the beam selection set is constructed such that each Radio Frequency (RF) chain selects multiple beams collect the leaked power in system. Then, the beam rotation combination scheme based on minimum phase is proposed. Maximum gain beam is taken as reference. The phases of the beam selection set are determined by minimum phase error criterion such that the channel gains of the selected beams are approximatively aligned in the same direction for maximizing the Signal-to-Noise Ratio (SNR) of each user. System performance is improved. Furthermore, the proposed precoding algorithm is theoretically analyzed. The expression of the upper bound of spectrum efficiency and energy efficiency are given. The correctness of the theoretical derivation is verified in experiment and the performance of proposed method is close to the ideal case of no-leakage power. The proposed scheme obtains better spectrum efficiency and energy efficiency performance than the existing algorithms.