High energy efficiency dynamic connected hybrid precoding for mmWave massive MIMO systems

This paper considers a high energy efficiency dynamic connected (HEDC) structure, which promotes the practicability and reduces the power consumption of hybrid precoding system by low-resolution phase shifters (PSs). Based on the proposed structure, a new hybrid precoding algorithm is presented to optimize the energy efficiency, namely, HP-HEDC algorithm. Firstly, via a new defined effective optimal precoding matrix, the problem of optimizing the analog switch precoding matrix is formulated as a sparse representation problem. Thus, the optimal analog switch precoding matrix can be readily obtained by the branch-and-bound method. Then, the digital precoding matrix optimization problem is modeled as a dictionary update problem and solved by the method of optimal direction (MOD). Finally, the diagonal entries of the analog PS precoding matrix are optimized by exhaustive search independently since PS and antenna is one-to-one. Simulation results show that the HEDC structure enjoys low power consumption and satisfactory spectral efficiency. The proposed algorithm presents at least 50% energy efficiency improvement compared with other algorithms when the PS resolution is set as 3-bit.