  In this paper, we study the hybrid precoding structures over limited feedback
channels for massive multiuser multiple-input multiple-output (MIMO) systems.
We focus on the system performance of hybrid precoding under a more realistic
hardware network model, particularly, with inevitable dissipation. The effect
of quantized analog and digital precoding is characterized. We investigate the
spectral efficiencies of two typical hybrid precoding structures, i.e., the
sub-connected structure and the fully-connected structure. It is revealed that
increasing signal power can compensate the performance loss incurred by
quantized analog precoding. In addition, by capturing the nature of the
effective channels for hybrid processing, we employ a channel correlation-based
codebook and demonstrate that the codebook shows a great advantage over the
conventional random vector quantization (RVQ) codebook. It is also discovered
that, if the channel correlation-based codebook is utilized, the sub-connected
structure always outperforms the fully-connected structure in either massive
MIMO or low signal-to-noise ratio (SNR) scenarios; otherwise, the
fully-connected structrue achieves better performance. Simulation results under
both Rayleigh fading channels and millimeter wave (mmWave) channels verify the
conclusions above.
