Energy-Efficient Hybrid Precoding for mmWave MIMO Systems With Phase Modulation Array

The hybrid precoding technique targeted at reducing the number of RF chains without obvious performance loss becomes a promising candidate in 5G communication. In this paper, an energy efficient hybrid precoding is proposed for the mmWave MIMO systems, in which phase modulation array (PMA) based analog precoding is adopted instead of phase shifters to reduce the power consumption and improve the energy efficiency. Specifically, PMA, consisting of delay lines and switches, enables to control phase and amplitude simultaneously, thus imposes additional constraint on the analog precoding. On this basis, the hybrid precoding problem is formulated for the PMA-based mmWave systems. Furthermore, an enhanced orthogonal constraint algorithm and an alternating optimization algorithm are proposed for the full-connected and sub-connected hybrid precoders, respectively. In addition, a more realistic situation, that there exists a minimum switch-on duration when the RF switch turns on, is considered for the proposed PMA-based hybrid precoder. Finally, simulation results have verified that, the PMA-based precoding can achieve higher spectral efficiency and energy efficiency when compared with the phase shifters based counterparts. More importantly, the proposed PMA-based hybrid precoder can significantly reduce the number of radio frequency chains, resulting in low energy consumption for its application in 5G green communication.