Mixed-Timescale Per-Group Hybrid Precoding for Multiuser Massive MIMO Systems

Considering the expensive radio frequency (RF) chain, huge training overhead, and feedback burden issues in massive MIMO, in this letter, we propose a mixed-timescale per-group hybrid precoding scheme under an adaptive partially connected antenna structure, where the RF precoder is implemented using an adaptive connection network (ACN) and M analog phase shifters (APSs), where M is the number of antennas at the base station. Exploiting the mixed time stage channel state information (CSI) structure, the joint-design of ACN, and APSs is formulated as a statistical signal-to-leakage-and-noise ratio maximization problem, and a heuristic group RF precoding algorithm is proposed to provide a near-optimal solution. Simulation results show that the proposed design advances at better energy efficiency and lower hardware cost, CSI signaling overhead and computational complexity than the conventional hybrid precoding schemes.