Energy-efficient Optimization Scheme for SWIPT-based Distributed Antenna System

In this paper, an energy efficient optimization scheme with low complexity for simultaneous wireless information and power transfer (SWIPT)-based distributed antenna system (DAS) is presented. The aim is to optimize energy efficiency (EE) with the constraints on maximum transmit power of each distributed antenna (DA) port and minimum harvested energy. By analyzing the structure of the objective problem, it is found that the EE optimization problem, which combines transmit power allocation (PA) with power splitting (PS) problem, can be predigested to an optimized one of PA. Based on this, utilizing Karush-Kuhn-Tucker (KKT) conditions and Lambert function, we can obtain the general form of optimal PA and corresponding closed-form solution. Finally, a low-complexity algorithm without iteration is put forward to attain the optimal number of valid DA ports and the homologous PA, as well as the power splitting ratio. Through Monte Carlo simulations, the validity of the proposed scheme and algorithm for SWIPT-based DAS are well verified.