Downlink Transmission Strategies in Power-Splitting SWIPT Distributed MISO Systems

This paper investigates the joint beamforming and power splitting factor optimization in distributed multiple input single output systems with power-splitting simultaneous wireless information and power transfer (SWIPT). We assume that all the user equipment (UEs) perform data transmission, whereas only UEs with sufficient large scale fading, defined as SWIPT UEs, also conduct energy harvesting. System total power consumption minimization problem is formulated with per-UE quality of service (QoS) constraints and minimal harvesting power constraints for SWIPT UEs with the consideration of RAU selection. First, we classify the UEs into two groups according to the large scale fading criterion. Then for perfect channel state information (CSI), the optimal problem is formulated and approximated by transforming RAU mode indicator function into reweighted ℓ₀-norm. Semi-definite relaxed method is used and an iterative algorithm is proposed. Furthermore, we consider the optimization with imperfect CSI and change the constraints to the worst case. To guarantee the rank-one constraint, an iterative function based on penalty function is proposed. Simulations show that the proposed algorithms with RAU selection can significantly reduce system total power consumption and also reveal that the RAU closest to SWIPT UEs tends to be active.