Research Of Multi-antenna Hybrid Precoding In Millimeter-wave Massive Multiuser Mimo Systems

The research hotspots of the fifth-generation wireless mobile communication systems mainly focus on millimeter-wave massive multiple-input-multiple-output(mmWave massive MIMO)technology at present.On one hand,mmWave with high frequencies and short wavelengths enables a number of antenna array to be packed in small physical dimension.On the other hand,massive MIMO can effectively overcome the free-space pathloss of mmWave signals and simultaneously serve dozens of users,which achieve orders of magnitude increase in channel capacity and spectrum efficiency.The integration of mmWave and MIMO technique is promising.Hybrid precoding technology has attracted attention with its excellent spectral efficiency and reliability in mmWave massive MIMO systems.However,hybrid precoding in mmWave massive MIMO systems has the disadvantages of high implementation cost and high computational complexity.There is currently a lack of research based on multiuser and multi-receiver antennas.It is also impossible to solve inter-user and intra-user interference.In this paper,we study and propose a low-complexity multi-receiver antennas hybrid block diagonalization precoding and combining(MU-HBD)scheme for the downlink of mmWave massive multiuser MIMO(MU-MIMO)systems.The uniform linear array(ULA)is extended to a uniform planar array(UPA)for multiuser millimeter-wave channels.And the performance of the MU-HBD algorithm is compared with the existing traditional SVD,BD,MMSE,hybrid MMSE,MRT,ZF and PZF hybrid precoding algorithms.The simulation results show that the MU-HBD algorithm can support multi-stream transmission and multireceiver antenna,overcome the shortcomings of poor performance under low SNR and guarantee system performance at high SNR in addition to lower implementation costs and computational complexity.Nevertheless,the above algorithms still require a large number of phase shifters,resulting in high hardware implementation costs.In order to further reduce the hardware implementation cost,this paper further studies the hybrid precoding and combining algorithm based on split sub-connected architecture in mmWave massive MUMIMO systems.The model based on split sub-connected architecture is introduced in detail and the formula of analog RF precoding based on split sub-connected architecture is derived.The simulation results show that the Sub MU-HBD algorithm enjoy better performance in massive MIMO systems.And the number of radio frequency(RF)links and phase shifters can be reduced exponentially.Therefore,the algorithm is expected to be applied to future wireless communication systems.