Dynamic Power Splitting for SWIPT with Nonlinear Energy Harvesting in Ergodic Fading Channel
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We study the dynamic power splitting for simultaneous wireless information and power transfer (SWIPT) in the ergodic fading channel. Considering the nonlinearity of practical energy harvesting circuits, we adopt the realistic nonlinear energy harvesting (EH) model rather than the idealistic linear EH model. To characterize the optimal rate-energy (R-E) tradeoff, we consider the problem of maximizing the R-E region, which is nonconvex. We solve this challenging problem for two different cases of the channel state information (CSI): (i) when the CSI is known only at the receiver (CSIR case) and (ii) when the CSI is known at both the transmitter and the receiver (CSIT case). First, for the case of CSIR, we develop the optimal dynamic power splitting scheme. To address the complexity issue of the optimal scheme, we also propose a suboptimal scheme with low complexity. Comparing the proposed schemes to the existing schemes, we provide various useful and interesting insights into the dynamic power splitting for the nonlinear EH. Second, we present the optimal and suboptimal schemes for the case of CSIT, and we obtain further insights. Numerical results demonstrate that the proposed schemes significantly outperform the existing schemes and the proposed suboptimal scheme works very close to the optimal scheme at a much lower complexity.
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