  In this work, we study codebook designs for full-dimension multiple-input
multiple-output (FD-MIMO) systems with a multi-panel array (MPA). We propose
novel codebooks which allow precise beam structures for MPA FD-MIMO systems by
investigating the physical properties and alignments of the panels. We
specifically exploit the characteristic that a group of antennas in a vertical
direction exhibit more correlation than those in a horizontal direction. This
enables an economical use of feedback bits while constructing finer beams
compared to conventional codebooks. The codebook is further improved by
dynamically allocating the feedback bits on multiple parts such as beam
amplitude and co-phasing coefficients using reinforcement learning. The
numerical results confirm the effectiveness of the proposed approach in terms
of both performance and computational complexity.
