Energy-efficient configuration of frequency resources in multi-cell MIMO-OFDM networks

In this paper, we investigate the configuration of frequency resources from the perspective of maximizing the energy efficiency (EE) of downlink multi-cell multi-carrier multi-antenna systems. We first formulate an optimization problem of subcarrier assignment to minimize the total power consumption at the base stations under the constraints of spectral efficiency (SE) requirements from multiple users. Then we find its closed-form solution by analyzing different cases. Analytical and simulation results show that when the SE requirement is low, using non-overlapped frequency resources is more energy efficient than using overlapped frequency resources and the EE increases with the SE. To support high SE, more spatial resources should be configured but a trade-off between SE and EE appears. Serving cell-center users will provide higher EE, while when serving the cell-edge users maximizing the EE will lead to a minor loss of the SE.