FFR Based Joint 3D Beamforming Interference Coordination for Multi-Cell FD-MIMO Downlink Transmission Systems

This paper investigate the downlink transmission, especially the interference coordination for the cell-edge users in multi-cell full-dimension multiple-input multiple-output (FD-MIMO) systems. We assume that each base station (BS) can only obtain statistical channel state information (CSI), so as to reduce the CSI required at each BS. We propose a fractional-frequency-reuse(FFR) scheme for multi-cell FD-MIMO systems, in which all the cell-center users occupy the same frequency band, while all the cell-edge users use the rest of the frequency band. Based on this FFR scheme, two joint three-dimensional (3D) beamforming interference coordination strategies, i.e., the full-cooperative strategy, and a more energy-efficient partial-cooperative strategy, are proposed to alleviate the inter-cell interference for the cell-edge users. Moreover, tractable approximations of the ergodic rate for both cell-center and cell-edge users are derived. Simulations show that the proposed interference coordination strategies can significantly improve the cell-edge performance, while maintain relatively high total throughput. The full-cooperative strategy performs best in the cell-edge performance, and the partial-cooperative strategy performs best in the aspects of total throughput and energy-efficiency.