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@article{faucris.233242486,
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.},
author = {Morsi, Rania and Jamali, Vahid and Hagelauer, Amelie Marietta and Ng, Derrick Wing Kwan and Schober, Robert},
doi = {10.1109/TCOMM.2019.2951109},
faupublication = {yes},
journal = {IEEE Transactions on Communications},
keywords = {channel capacity; energy harvesting (EH); matched filters; nonlinear circuit analysis; rectennas; rectifiers; Schottky diodes; semiconductor detectors; signal design; Wireless power transmission},
month = {Jan},
note = {CRIS-Team Scopus Importer:2020-02-04},
pages = {582-601},
peerreviewed = {Yes},
title = {{Conditional} {Capacity} and {Transmit} {Signal} {Design} for {SWIPT} {Systems} with {Multiple} {Nonlinear} {Energy} {Harvesting} {Receivers}},
volume = {68},
year = {2020}
}
@inproceedings{faucris.210683054,
abstract = {In this paper, we introduce a low decoding complexity space-time modulation scheme that achieves full transmit diversity without the need of channel knowledge at the transmitter (Tx) nor at the receiver (Rx). The scheme is based on differential encoding of a low-complex quasi-orthogonal space-time block code (STBC). The idea of the differential encoding is based on mapping the original system to an equivalent system which is composed of two orthogonal subsystems. The differential encoding and decoding approach is described and the receiver metric is derived. The described technique is valid for any number of transmit antennas M for which a square orthogonal code of size M/2 exists, and is valid for any number of receive antennas. The proposed scheme is favourable in that it has single complex symbol decoding complexity while achieving a performance close to other differential quasi orthogonal codes of higher complexity and a remarkable performance advantage compared to differential orthogonal schemes especially at high data rates.
transfer (SWIPT) systems employing a practical nonlinear radio frequency (RF) energy harvesting (EH)
receiver. In particular, we consider a three-node system with one transmitter that broadcasts a common
signal to separated information decoding (ID) and EH receivers. Owing to the nonlinearity of the EH
receiver circuit, the efficiency of wireless power transfer depends significantly on the waveform of the
transmitted signal. In this paper, we aim to answer the following fundamental question: What is the
optimal input distribution of the transmit waveform that maximizes the rate of the ID receiver for a
given required harvested power at the EH receiver? In particular, we study the capacity of a SWIPT
system impaired by additive white Gaussian noise (AWGN) under average-power (AP) and peak-power
(PP) constraints at the transmitter and an EH constraint at the EH receiver. Using Hermite polynomial
bases, we prove that the optimal capacity-achieving input distribution that maximizes the rate-energy
region is unique and discrete with a finite number of mass points. Our numerical results show that the
rate-energy region is enlarged for a larger PP constraint and that the rate loss of the considered SWIPT
system compared to the AWGN channel without EH receiver is reduced by increasing the AP budge}, author = {Morsi, Rania and Jamali Kooshkghazi, Vahid and Ng, Derrick Wing Kwan and Schober, Robert}, booktitle = {IEEE International Conference on Communications (ICC)}, date = {2018-05-20/2018-05-24}, doi = {10.1109/ICC.2018.8422269}, faupublication = {yes}, keywords = {AWGN channels;channel capacity;decoding;energy harvesting;optimisation;polynomials;radio receivers;radiofrequency power transmission;telecommunication power supplies;rate-energy region;nonlinear energy harvesting circuit;information-theoretic limits;wireless power transfer;SWIPT system;nonlinear radio frequency energy harvesting receiver;information decoding;additive white Gaussian noise;average-power constraint;peak-power constraint;Hermite polynomial;simultaneous wireless information and power transfer;Receivers;Radio frequency;Integrated circuit modeling;Rectennas;Transmitters;RF signals;AWGN channels}, peerreviewed = {unknown}, title = {{On} the {Capacity} of {SWIPT} {Systems} with a {Nonlinear} {Energy} {Harvesting} {Circuit}}, url = {https://ieeexplore.ieee.org/document/8422269/}, venue = {Kansas City, Missouri}, year = {2018} } @inproceedings{faucris.203892121, abstract = {In this paper, we analyze the performance of a time-slotted multi-antenna wireless powered communication (WPC) system, where a wireless device first harvests radio frequency (RF) energy from a power station (PS) in the downlink to facilitate information transfer to an information receiving station (IRS) in the uplink. The main goal of this paper is to provide insights and guidelines for the design of practical WPC systems. To this end, we adopt a recently proposed parametric non-linear RF energy harvesting (EH) model, which has been shown to accurately model the end-to-end non-linearity of practical RF EH circuits. In order to enhance the RF power transfer efficiency, maximum ratio transmission is adopted at the PS to focus the energy signals on the wireless device. Furthermore, at the IRS, maximum ratio combining is used. We analyze the outage probability and the average throughput of information transfer, assuming Nakagamim fading uplink and downlink channels. Moreover, we study the system performance as a function of the number of PS transmit antennas, the number of IRS receive antennas, the transmit power of the PS, the fading severity, the transmission rate of the wireless device, and the EH time duration. In addition, we obtain a fixed point equation for the optimal transmission rate and the optimal EH time duration that maximize the asymptotic throughput for high PS transmit powers. All analytical results are corroborated by simulations.}, author = {Morsi, Rania and Boshkovska, Elena and Ramadan, Esmat and Ng, Derrick Wing Kwan and Schober, Robert}, booktitle = {International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)}, date = {2017-07-03/2017-07-06}, doi = {10.1109/SPAWC.2017.8227714}, editor = {IEEE}, faupublication = {yes}, peerreviewed = {Yes}, title = {{On} the {Performance} of {Wireless} {Powered} {Communication} {With} {Non}-linear {Energy} {Harvesting}}, url = {https://ieeexplore.ieee.org/document/8227714/}, venue = {Sapporo}, year = {2017} } @inproceedings{faucris.203892381, abstract = {In this paper, we study the downlink multiuser scheduling problem for systems with simultaneous wireless information and power transfer (SWIPT). We design optimal scheduling algorithms that maximize the long-term average system throughput under different fairness requirements, such as proportional fairness and equal throughput fairness. In particular, the algorithm designs are formulated as non-convex optimization problems which take into account the minimum required average sum harvested energy in the system. The problems are solved by using convex optimization techniques and the proposed optimization framework reveals the tradeoff between the long-term average system throughput and the sum harvested energy in multiuser systems with fairness constraints. Simulation results demonstrate that substantial performance gains can be achieved by the proposed optimization framework compared to existing suboptimal scheduling algorithms from the literature.}, author = {Chynonova, Maryna and Morsi, Rania and Ng, Derrick Wing Kwan and Schober, Robert}, booktitle = {EUSIPCO}, date = {2015-08-31/2015-09-04}, doi = {10.1109/EUSIPCO.2015.7362732}, editor = {IEEE}, faupublication = {yes}, isbn = {978-0-9928-6263-3}, keywords = {RF energy harvesting;wireless information and power transfer;optimal multiuser scheduling}, pages = {1989-1993}, peerreviewed = {Yes}, title = {{OPTIMAL} {MULTIUSER} {SCHEDULING} {SCHEMES} {FOR} {SIMULTANEOUS} {WIRELESS} {INFORMATION} {AND} {POWER} {TRANSFER}}, url = {https://ieeexplore.ieee.org/document/7362732/}, venue = {Nice, France}, year = {2015} } @article{faucris.203892646, abstract = {In this paper, we consider a wireless powered communication system, where an energy harvesting (EH) node harvests energy from a radio frequency (RF) signal broadcasted by an access point (AP) in the downlink (DL). The node stores the harvested energy in an energy buffer and uses the stored energy to transmit data to the AP in the uplink (UL). We investigate two simple online transmission policies for the EH node, namely a best-effort policy and an on-off policy, which do not require knowledge of the EH profile nor channel knowledge. In particular, for both policies, the EH node transmits in each time slot with a constant desired power if sufficient energy is available in its energy buffer. Otherwise, the node transmits with the maximumpossible power in the best-effort policy and remains silent in the on-off policy. For both policies, we use the theory of discrete-time continuous-state Markov chains to analyze the limiting distribution of the stored energy for finite-and infinite-size energy buffers. We provide this limiting distribution in closed form for a Nakagami-m fading DL channel and analyze the outage probability for a Nakagami-m fading UL channel. All derived analytical results are not limited to EH via RF WPT but are applicable for any independent and identically distributed EH process from e.g. solar and wind energy. Our results reveal that, for low-to-medium outage probabilities, the best-effort policy is superior to the on-off policy and the optimal UL transmit power of the EH node that minimizes the outage probability is always less than the average harvested power. The opposite behaviour is observed for high outage probabilities. Furthermore, we show that the minimum outage probability of the two proposed policies is near-optimal.}, author = {Morsi, Rania and Michalopoulos, Diomidis and Schober, Robert}, doi = {10.1109/TWC.2017.2772230}, faupublication = {yes}, journal = {IEEE Transactions on Wireless Communications}, keywords = {Energy harvesting;energy storage;Markov processes;wireless power transmission}, pages = {863-881}, peerreviewed = {Yes}, title = {{Performance} {Analysis} of {Near}-{Optimal} {Energy} {Buffer} {Aided} {Wireless} {Powered} {Communication}}, url = {https://ieeexplore.ieee.org/document/8107546/}, volume = {17}, year = {2017} } @inproceedings{faucris.203892915, abstract = {In this paper, we consider an energy harvesting (EH) node which harvests energy from a radio frequency (RF) signal broadcasted by an access point (AP) in the downlink (DL). The node stores the harvested energy in an energy buffer and uses the stored energy to transmit data to the AP in the uplink (UL). We consider a simple transmission policy, which accounts for the fact that in practice the EH node may not have knowledge of the EH profile nor of the UL channel state information. In particular, in each time slot, the EH node transmits with either a constant desired power or a lower power if not enough energy is available in its energy buffer. For this simple policy, we use the theory of discrete-time continuous-state Markov chains to analyze the limiting distribution of the stored energy for finite-and infinitesize energy buffers. Moreover, we take into account imperfections of the energy buffer and the circuit power consumption of the EH node. For a Rayleigh fading DL channel, we provide the limiting distribution of the energy buffer content in closed form. In addition, we analyze the average error rate (AER) and the outage probability of a Rayleigh faded UL channel and show that the diversity order is not affected by the finite capacity of the energy buffer. Our results reveal that, except for high outage probabilities and high AERs, the optimal transmit power by the EH node is less than the average harvested power and increases with the capacity of the energy buffer.}, author = {Morsi, Rania and Michalopoulos, Diomidis and Schober, Robert}, booktitle = {International Conference on Communications ICC}, date = {2015-06-08/2015-06-12}, doi = {10.1109/ICC.2015.7248695}, editor = {IEEE}, faupublication = {yes}, keywords = {Buffer storage, Limiting, Energy storage, Fading, Probability density function, Approximation methods, Wireless communication}, pages = {2469-2475}, peerreviewed = {Yes}, title = {{Performance} {Analysis} of {Wireless} {Powered} {Communication} with {Finite}/{Infinite} {Energy} {Storage}}, url = {https://ieeexplore.ieee.org/document/7248695/}, venue = {London, UK}, year = {2015} } @inproceedings{faucris.203893177, abstract = {In this paper, we design a resource allocation algorithm for multiuser simultaneous wireless information and power transfer systems for a realistic non-linear energy harvesting (EH) model. In particular, the algorithm design is formulated as a non-convex optimization problem for the maximization of the long-term average total harvested power at EH receivers subject to quality of service requirements for information decoding receivers. To obtain a tractable solution, we transform the corresponding non-convex sum-of-ratios objective function into an equivalent objective function in parametric subtractive form. This leads to a computationally efficient iterative resource allocation algorithm. Numerical results reveal a significant performance gain that can be achieved if the resource allocation algorithm design is based on the non-linear EH model instead of the traditional linear model.}, author = {Boshkovska, Elena and Morsi, Rania and Ng, Derrick Wing Kwan and Schober, Robert}, booktitle = {International Conference on Communications ICC}, date = {2016-05-22/2016-06-27}, doi = {10.1109/ICC.2016.7511403}, editor = {IEEE}, faupublication = {yes}, peerreviewed = {Yes}, title = {{Power} {Allocation} and {Scheduling} for {SWIPT} {Systems} with {Non}-linear {Energy} {Harvesting} {Model}}, url = {https://ieeexplore.ieee.org/document/7511403/}, venue = {Kuala Lumpur}, year = {2016} }