Optimal design of energy efficient two-tier HetNets with massive MIMO by coordinated multipoint beamforming

This paper presents an energy-efficient (EE) coordinated multipoint beamforming (CMBF) approach that minimizes the total power consumption based on both the dynamic emitted power and static hardware power while maintaining necessary quality of service (QoS) constraints and different coordinated schemes. We deduce expressions the optimal value of each parameter in a two-tier heterogeneous networks (HetNets) from the perspective of energy efficiency (EE), considering a massive multiple-input multiple output (MIMO) system in conjunction with CMBF and small cell deployment. We find that the EE of HetNets is sensitive to the coordinated scheme design, the number of macro-cell and small-cell base station antennas, and QoS constraints. As such, all these factors should be taken into account in system design. Furthermore, we provide promising analytical and simulation results demonstrating that the proposed HetNets generally provides a solution for achieving maximal EE performance with relatively low-complexity CMBF.