  Hybrid precoding is a cost-effective approach to support directional
transmissions for millimeter wave (mm-wave) communications, and its design
challenge mainly lies in the analog component which consists of a network of
phase shifters. The partially-connected structure employs a small number of
phase shifters and therefore serves as an energy efficient solution for hybrid
precoding. In this paper, we propose a double phase shifter (DPS)
implementation for the phase shifter network in the partially-connected
structure, which allows more tractable and flexible hybrid precoder design. In
particular, the hybrid precoder design is identified as an eigenvalue problem.
To further enhance the performance, dynamic mapping from radio frequency (RF)
chains to antennas is proposed, for which a greedy algorithm and a modified
K-means algorithm are developed. Simulation results demonstrate the performance
gains of the proposed hybrid precoding algorithms with the DPS implementation
over existing ones. Given its low hardware complexity and high spectral
efficiency, the proposed structure is a promising candidate for 5G mm-wave
systems.
