Feedback Energy Reduction in Massive MIMO Systems

The availability of channel state information (CSI) at the transmitter plays a central role to provide high system performance in massive multiple-input multiple-output (MIMO) systems. In a frequency division duplexing (FDD) system, acquiring this information requires a prohibitive amount of feedback and a significant feedback energy, since it increases with the number of transmit antenna. In this paper, we address the issue of significant energy consumed to feedback all CSI to the base station (BS). To this end, we propose a novel feedback routing scheme based on transmit antenna selection for massive MIMO systems. The proposed scheme aims to jointly reduce the energy needed to feedback the CSI to the BS and the complexity of the transmit antenna selection. We formulate the problem of finding the feedback routing that minimizes the energy consumption as a least cost Hamiltonian path problem. To solve the formulated problem, we propose both an integer linear programming formulation to find the optimal solution and a heuristic dynamic programming algorithm to find a suboptimal solution with reasonable computational complexity. Computer simulations show that our scheme offers enormous reduction in feedback energy while ensuring low computational complexity.