Multi-User Hybrid Precoding and Decoding Design for mm-Wave Large Antenna Systems

Hybrid digital to analog (D-A) precoding and decoding design has recently been the focus of considerable fascination for reducing the number of costly radio-frequency (RF) chains in millimeter-wave (mm-Wave) systems. This paper investigates multi-user joint hybrid D-A precoding and decoding design for mm-Wave large antenna systems. The intrinsic focus of this work is to reduce the interference caused by users sharing the same scatterers during simultaneous uplink transmission. The analog precoder and decoder, firstly, are jointly designed using a Riemannian optimisation method based on Stiefel manifold (ROSt) in order to maximise the desired signal while reducing the interference. Then, the digital decoder is also designed jointly using Minimum Mean-Square Error (MMSE) based on effective channels. To significantly enhance the performance, an iterative algorithm is further presented that employs uplink and downlink effective channels. To accomplish this, the analog precoder and decoder are jointly designed based on downlink effective channels and steepest descent (SD) algorithm. Once again MMSE is applied for the digital decoder by exploiting effective channels. Extensive simulations demonstrate that the achievable rate of our proposed ROSt and SD algorithms surpasses the achievable rate of the existing algorithms in hybrid D-A paradigms.