  Simultaneous wireless information and power transfer (SWIPT) has been
recognized as a promising approach to improving the performance of energy
constrained networks. In this paper, we investigate a SWIPT based three-step
two-way decode-and-forward (DF) relay network with a non-linear energy
harvester equipped at the relay. As most existing works require instantaneous
channel state information (CSI) while CSI is not fully utilized when designing
power splitting (PS) schemes, there exists an opportunity for enhancement by
exploiting CSI for PS design. To this end, we propose a novel heterogeneous PS
scheme, where the PS ratios are dynamically changed according to instantaneous
channel gains. In particular, we derive the closed-form expressions of the
optimal PS ratios to maximize the capacity of the investigated network and
analyze the outage probability with the optimal dynamic PS ratios based on the
non-linear energy harvesting (EH) model. The results provide valuable insights
into the effect of various system parameters, such as transmit power of the
source, source transmission rate, and source to relay distance on the
performance of the investigated network. The results show that our proposed PS
scheme outperforms the existing schemes.
