Three-Dimensional Beamforming for Large-Scale FD-MIMO Systems Exploiting Statistical Channel State Information

Abstract

In this paper, we provide a practical downlink transmission approach for single-cell full-dimension multiple-input–multiple-output (FD-MIMO) systems with large-scale uniform planar antenna array at the base station (BS). Under the assumption of only statistical channel state information (CSI) at the BS, we derive the optimal beamforming vector of each user by maximizing a lower bound on the average signal-to-leakage-plus-noise ratio. Some main guidelines for user scheduling are also derived under this criterion. Based on these results, a low-complexity 3-D beamforming space-division multiple-access (SDMA) transmission algorithm exploiting only the statistical CSI of each user is proposed. Furthermore, the ergodic sum rate of the proposed algorithm is analyzed, and a closed-form expression, as well as a low signal-to-noise ratio (SNR) approximation and a high-SNR approximation, are derived. Simulation results show that the proposed algorithm performs well in terms of achievable sum rate, and the analytical results on its achievable sum rate are validated.