Optimal time allocatio n for multi-antenna wireless powered
heterogeneous sensor network communications under
imperfect CSI
Feng Zhao, Lina Wei, Hongbin Chen
n
Key Laboratory of Cognitive Radio and Information Processing (Guilin University of Electronic Technology), Ministry of Education, Guilin
541004, China
article info
Article history:
Received 14 May 2015
Received in revised form
25 June 2015
Accepted 26 June 2015
Keywords:
Sensor networks
Energy harvesting
Wireless power transfer
Energy beamforming
Channel estimation
Time allocation
abstract
Energy harvesting is a promising technology to overcome the energy bottleneck in battery-
powered heterogeneous sensor networks (HSNs). In an energy harvesting HSN, hetero-
geneous sensor nodes harvest energy to power themselves, and use the harvested energy
for data transmission. This paper investigates a multiple-input single-output wireless
powered HSN with imperfect channel state information (CSI). The receiver harvests energy
from the power transmitter via radio-frequency wireless power transfer (WPT) in the
downlink to support wireless information transfer (WIT) in the uplink. To improve WPT
efficiency, the power transmitter employs energy beamforming by using instantaneous CSI.
Under imperfect CSI, the receiver performs channel estimation and feeds the CSI back to the
transmitter. We focus on balancing the time duration for channel estimation, WPT, and WIT,
so as to maximize the throughput while satisfying the time duration constraint. By solving
this optimizing problem, we derive the optimal time resource allocation scheme. Numerical
simulation results demonstrate the effectiveness of the proposed scheme.
& 2015 Elsevier B.V. All rights reserved.
1. Introduction
Recently, energy harvesting wireless communications
has been viewed as a safe and promising technique [1–3],
which is especially important for energy-constrained wire-
less communication systems such as HSNs. A radio-
frequency (RF) signal is a viable new source for wireless
energy harvesting, since it has clear advantage in effective
energy transfer distance. Therefore, the RF energy harvest-
ing technique has applied in various areas, such as wireless
sensor networks [4,5],bodyareanetworks[6,7].Inaddition,
RF energy harvesting should be used to provide charging
capability for a variety of low-power mobile devices [8].
Since a RF signal carry energy and information at the
same time, the topic of simultaneous wireless information
and power transfer (SWIPT) has drawn significant attention
in recent years. Varshney first proposed the idea of SWIPT
in [9], where a capacity-energy function was proposed to
characterize the fundamental performance tradeoff for
SWIPT in single-input single-output (SISO) systems. It was
done under additive white Gaussian noise (AWGN) channel
with amplitude-constrained input. Ref. [10] investigated a
coupled-inductor circuit in a special case of average power-
constrained AWGN channel with frequency-selective fad-
ing, and presented an optimal tradeoff between the infor-
mation and power transfer. In order to address that
practical circuits for harvesting energy from radio signals
are not yet able to decode the carried information directly
in SWIPT, [11] proposed a dynamic power splitting scheme.
This scheme considered that the received signal is dynami-
cally splitted into two streams, while one portion is for
energy harvesting and the remaining part is for information
decoding. Different from [9–11] which studied the
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journal homepage: www.elsevier.com/locate/sigpro
Signal Processing
http://dx.doi.org/10.1016/j.sigpro.2015.06.022
0165-1684/ & 2015 Elsevier B.V. All rights reserved.
n
Corresponding author.
E-mail address: chbscut@guet.edu.cn (H. Chen).
Signal Processing ] (]]]]) ]]] –]]]
Please cite this article as: F. Zhao, et al., Optimal time allocation for multi-antenna wireless powered heterogeneous
sensor network communications under imperfect CSI, Signal Processing (2015), http://dx.doi.org/10.1016/j.
sigpro.2015.06.022i