Energy Efficiency Maximization with Per-Antenna Power Constraints for Heterogeneous Networks

This paper considers energy efficiency (EE) optimization in downlink multiple-input multiple-output (MIMO) heterogeneous networks (HetNets) in which one macro base station (MBS) and multiple small cell base stations (SBSs) communicate with multiple MIMO users. The primary objective is to design the precoders to maximize the network EE under the constraints on per-antenna and per-base-station transmit power and acceptable interference levels at each user in the macro cell. The design problem results in nonconvex fractional program whose optimal solutions cannot be found directly. In this paper, the relationship between the achievable data rates and the minimum mean square error (MMSE) is adopted to reformulate the design problem into amenable one. Then, an iterative algorithm based the Dinklebach and the block coordinate ascent (BCA) methods is employed for finding optimal precoders. We conduct the numerical simulations to examine the achievable EE performance of the considered HetNets.