Beamforming and power allocation designs for energy efficiency maximization in MISO distributed antenna systems

In this paper, we present a beamforming and power allocation algorithm for a downlink multiple-input single-output distributed antenna system which maximizes energy efficiency (EE). To reduce the computational complexity of conventional joint optimization approaches relying on an iterative method, we propose a near optimal scheme based on a closed-form solution. Employing the decomposition property of the joint optimization problem, the EE problem is solved in two steps. First, we determine the beamforming strategy for the EE maximization exposing the structure of beamforming vectors. Then, the optimal power allocation is presented as a closed-form solution by solving Karush-Kuhn-Tucker conditions. Through numerical simulations, we confirm that the proposed solution shows the performance almost identical to the jointly optimum method with much reduced complexity.