Cell Splitting for Energy-Efficient Massive MIMO

In this paper, we propose a novel cell splitting approach for massive multiple-input multiple-output (MIMO) base stations to improve energy efficiency. The user equipments (UEs) in the cell are divided into two groups based on their distances to the base station. These two UE groups are scheduled at different time slots, which effectively splits a cell into inner and outer cells. The number of transmitting and receiving antennas together with the downlink and uplink transmission powers are adapted according to the number of cell edge and center UEs to maximize energy efficiency. We propose two algorithms to optimize the number of antennas and transmission powers. Cell splitting is able to reach energy efficiency (EE) gain of 11-41 % depending on the UE density when compared to a conventional load-adaptive massive MIMO system. The inevitable loss of cell edge UE rates can be controlled by setting a target UE rate, which also reduces the search space of the optimization algorithm.