Practical Nonlinear Energy Harvesting Model in MIMO DF Relay System with Channel Uncertainty

In this paper, we aim to maximize the end-to-end achievable rate of multiple-input multiple-output (MIMO) decode-and-forward (DF) where the relay is an energy harvesting (EH) node using the time switching (TS) scheme. The relay first harvests the energy from the source, then uses its harvested energy to forward the information carrying signal from the source to the destination. The EH model at the relay is a nonlinear model. Also, we assume that the channel knowledge is imperfect at the relay and destination. We propose the structure of the optimal covariance matrices at the source (during EH and information decoding periods), the optimal covariance matrix at the relay and the optimal EH time ratio. Through the simulation results, we compare between different linear/nonlinear EH models and we show the gain/loss performance of the linear model compared to other nonlinear EH models.