Two-stage hybrid precoding for massive MIMO systems

Massive multiple-input multiple-output (MIMO) systems are expected to significantly enhance the energy efficiency (EE) and spectrum efficiency (SE). However, RF transceivers introduce huge cost of high complexity of the hardware with the antennas increasing. In this paper, considering the low-complexity hybrid structure, we propose a hybrid precoding scheme to approach the performance of the traditional full-complexity baseband digital zero-forcing (FD-ZF) precoding. The proposed scheme, named two-stage hybrid precoding, essentially applies phase-only control at the RF domain and then performs a low-dimensional baseband digital ZF precoding based on the effective channels seen from baseband. Meanwhile, quantized RF phase (no more than 3bits) is considered. The proposed scheme is simulated in ideal Rayleigh fading channels and the results are nearly equal to FD-ZF.