To improve the energy efficiency of multi-cell massivemultiple-input-multiple-outputsystem while guaranteeing the information transmission quality, this study proposes a dual-layer coordinated beamforming scheme. In...
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To improve the energy efficiency of multi-cell massivemultiple-input-multiple-outputsystem while guaranteeing the information transmission quality, this study proposes a dual-layer coordinated beamforming scheme. In the proposed scheme, the beamformer at each evolved node B (eNB) is divided into a cell-layer beamformer and a user-layer beamformer. The cell-layer beamformer is used to mitigate inter-cell interference (ICI) by exchanging long-term channel state information (CSI) among eNBs. The user-layer beamformer serves user according to the local real-time CSI at each eNB. On the basis of the dual-layer structure, the cell-layer beamformers, the user-layer beamformers, and power allocation are jointly optimised in order to minimise the total transmit power across all the eNBs subject to the signal-to-interference-plus-noise ratio requirements and single-antenna power constraints. To make the original problem solvable, the ICI is replaced by its upper bound. Then, the problem is partitioned into two convex sub-problems, and two iterative algorithms are proposed in order to find the sub-optimal solution to the original optimisation problem. Simulation results show that the proposed scheme performs better than two reference schemes including the existing zero-forcing scheme and coordinative multiple point schemes.
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