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@article{faucris.266975367,
abstract = {In this paper, we study multi-user multi-antenna wireless power transfer
(WPT) systems, where each antenna at the energy harvesting (EH) nodes
is connected to a dedicated non-linear rectifier. We propose optimal
transmit strategies which maximize a weighted sum of the average
harvested powers at the EH nodes subject to a constraint on the power
budget of the transmitter. First, for multiple-input single-output
(MISO) WPT systems, we prove that the optimal strategy employs maximum
ratio transmission (MRT) beamforming and scalar symbols with arbitrary
phases and discrete amplitudes following a probability density function
(pdf) with at most two mass points. Then, we prove that for single-input
multiple-output (SIMO) WPT systems, the optimal transmit symbol
amplitudes are discrete random variables, whose pdf also has no more
than two mass points. For general multi-user MIMO WPT, we show that the
optimal transmit strategy employs scalar unit-norm symbols with
arbitrary phases and at most two beamforming vectors. To determine these
vectors, we formulate a non-convex optimization problem and obtain an
optimal solution based on monotonic optimization. Since the
computational complexity of the optimal solution is high, we propose a
low-complexity iterative algorithm to obtain a suboptimal solution,
which achieves near-optimal performance. Our simulation results reveal
that the proposed transmit strategy for multi-user MIMO WPT systems
outperforms baseline schemes based on a linear EH model and a single
beamforming vector. For a given transmit power budget, we show that the
harvested power saturates when increasing the number of transmit
antennas. Finally, we observe that the harvested power region spanned by
multiple EH nodes is convex and the power harvested at one EH node can
be traded for a higher harvested power at the other node},
author = {Shanin, Nikita and Schober, Robert and Cottatellucci, Laura},
doi = {10.1109/TCOMM.2021.3134690},
faupublication = {yes},
journal = {IEEE Transactions on Communications},
pages = {1726 - 1741},
peerreviewed = {Yes},
title = {{Optimal} {Transmit} {Strategy} for {Multi}-{User} {MIMO} {WPT} {Systems} {With} {Non}-{Linear} {Energy} {Harvesters}},
volume = {70},
year = {2022}
}