Performance Analysis for BDPSK Modulated SWIPT Cooperative Systems With Nonlinear Energy Harvesting Model

In this paper, we investigate the performance of simultaneous wireless information and power transfer cooperative amplify-and-forward communication systems with binary differential phase-shift keying modulation. The piece-wise linear energy harvesting (EH) model that captures the nonlinear input-output characteristic of the EH circuit is considered. We derive a novel and closed-form expression of the probability density function (PDF) for the harvested power of the nonlinear EH receiver. Based on this, we further derive the expressions for the PDF of the received signal-to-noise ratio of the cooperative link and the average biterror-rate of the systems. Numerical results confirm the validity of the proposed analytical results. It is shown that the system performance is significantly overestimated when the ideal linear EH model is used in the place of the practical nonlinear EH model. An opposite result to the linear EH model that the system performance is monotonically improved with the increase of the distance between the location of the relay node and the source node is also demonstrated.