Conditional Capacity and Transmit Signal Design for SWIPT Systems with Multiple Nonlinear Energy Harvesting Receivers

Morsi R, Jamali V, Hagelauer AM, Ng DWK, Schober R (2020)

Publication Type: Journal article

Publication year: 2020

Journal

IEEE Transactions on Communications Institute of Electrical and Electronics Engineers (IEEE)

Book Volume: 68

Pages Range: 582-601

Article Number: 8890696

Journal Issue: 1

DOI: 10.1109/TCOMM.2019.2951109

Abstract

In this paper, we study information-theoretic limits for simultaneous wireless information and power transfer (SWIPT) systems employing practical nonlinear radio frequency (RF) energy harvesting (EH) receivers (Rxs). In particular, we consider a SWIPT system with one transmitter that broadcasts a common signal to an information decoding (ID) Rx and multiple EH Rxs. Owing to the nonlinearity of the EH Rxs' circuitry, the efficiency of wireless power transfer depends on the waveform of the transmitted signal. We aim to answer the following fundamental question: What is the optimal input distribution of the transmit signal waveform that maximizes the information transfer rate at the ID Rx conditioned on individual minimum required direct-current (DC) powers to be harvested at the EH Rxs? Specifically, we study the conditional capacity problem of a SWIPT system impaired by additive white Gaussian noise subject to average-power (AP) and peak-power (PP) constraints at the transmitter and nonlinear EH constraints at the EH Rxs. To this end, we develop a novel nonlinear EH model that captures the saturation of the harvested DC power by taking into account not only the forward current of the rectifying diode but also the reverse breakdown current. Then, we derive a novel semi-closed-form expression for the harvested DC power, which simplifies to closed form for low input RF powers. The derived analytical expressions are shown to closely match circuit simulation results. We solve the conditional capacity problem for real- and complex-valued signalling and prove that the optimal input distribution that maximizes the rate-energy (R-E) region is unique and discrete with a finite number of mass points. Furthermore, we show that, for the considered nonlinear EH model and a given AP constraint, the boundary of the R-E region saturates for high PP constraints due to the saturation of the harvested DC power for high input RF powers. In addition, we devise a suboptimal input distribution whose R-E tradeoff performance is close to optimal. All theoretical findings are verified by numerical evaluations.

Authors with CRIS profile

Rania Morsi Lehrstuhl für Digitale Übertragung Amelie Marietta Hagelauer Lehrstuhl für Technische Elektronik Robert Schober Lehrstuhl für Digitale Übertragung

Involved external institutions

University of New South Wales (UNSW)

Australia (AU)

How to cite

APA:

Morsi, R., Jamali, V., Hagelauer, A.M., Ng, D.W.K., & Schober, R. (2020). Conditional Capacity and Transmit Signal Design for SWIPT Systems with Multiple Nonlinear Energy Harvesting Receivers. IEEE Transactions on Communications, 68(1), 582-601. https://dx.doi.org/10.1109/TCOMM.2019.2951109

MLA:

Morsi, Rania, et al. "Conditional Capacity and Transmit Signal Design for SWIPT Systems with Multiple Nonlinear Energy Harvesting Receivers." IEEE Transactions on Communications 68.1 (2020): 582-601.

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