Special Issue on Wireless Powered Communications Networks
Published online: 30 March 2018
Springer Science+Business Media, LLC, part of Springer Nature 2018
Power supply is a long-standing problem for mobile devices
and sensor nodes. When entering the era of Internet-of-Things
(IoT) and 5G, with the significant growing number of IoT
devices and the increasing dependence on mobile devices, it
is expected that the power supply issue will be more demand-
ing in the future. Wireless power transfer is a technology that
allows replenishing the battery without physical connections.
Compared to the cordless power supply technologies that rely
on pure energy harvesting, wireless power transfer provides
an active and controlled way for power delivery to mobile
devices or sensor nodes. Since the power is targeted for wire-
less communication, jointly considering wireless power trans-
fer and wireless communication is essential, which leads to the
research of wireless powered communication networks.
However, there are several challenges that need to be ad-
dressed for practical design of wireless powered communica-
tion networks, such as the concerns of power transfer efficien-
cy and constraint, delay constraint, resource allocation, relay-
ing, MAC protocols, and prototyping under different network
architectures and various advanced systems.
This special issue includes four papers that provide new
designs and overview for wireless powered communications
networks. In the paper BOptimal-stopping spectrum sensing in
energy harvesting cognitive radio systems^, a cognitive radio
system in which the secondary user (SU) is powered by ener-
gy harvested exclusively from the environment is considered.
Optimizing the SU’s expected achievable throughput leads to
a parametrized optimal stopping problem. An efficient algo-
rithm is proposed to derive the optimal save-ratio and
spectrum sensing rule, which is significantly faster than the
conventional simulated annealing algorithm. A suboptimal
solution is also proposed to further reduce the computational
complexity, in which the problem is formulated as a mixed-
integer non-linear programming problem.
In the paper BSimultaneous wireless information and pow-
er transfer in multi-antenna systems^, a comprehensive liter-
ature survey on simultaneous wireless information and power
transfer (SWIPT) in multi-antenna systems is provided.
Firstly, recent contributions on the theoretical analysis of
SWIPT from the information theoretic standpoint is reviewed.
Secondly, the implementation aspects of multi-antenna
SWIPT are discussed. Then, dynamic SWIPT optimization is
reviewed, followed by the introduction of recent works on
secure SWIPT. Finally, researches on combining SWIPT with
state-of-the- art techniques are overviewed.
In the paper BRobust downlink beamforming for multiuser
SWIPT systems with imperfect CSI^, a multiuser multiple-
input-single-output simultaneous wireless information and
power transfer downlink system with imperfect channel is
considered. The worst-case harvested energy of all users is
maximized with the signal-to-interference and noise ratio re-
quirement satisfied, assuming unknown channel estimate er-
ror. The beamforming vector optimization is formulated as a
semi-definite programming problem transformed by the S-
procedure method. With semidefinite relaxation, optimal
beamforming vector is obtained.
Finally in the paper BThroughput and energy efficiency of
wireless powered multi-tier MIMO HetNetsB, wireless powered
multi-tier multi-input multi-output (MIMO) heterogeneous net-
works (HetNets), where the multi-antenna base stations perform
downlink transmission, are considered. Two cases are consid-
ered: energy harvesting with and without energy beamforming.
By using tools of stochastic geometry, throughput and energy
efficiency are analyzed. Closed-form and tractable results are
obtained to conclude that the proposed wireless-powered
MIMO HetNets can achieve higher energy efficiency compared
to the conventional HetNets without energy harvesting, and the
energy efficiency performance can be further improved by intro-
ducing well-designed energy beamforming across tiers.
* Chia-Han Lee
National Chiao Tung University, 1001 University Rd,
Hsinchu 30010, Taiwan
Beijing University of Posts and Telecommunications, 10 Xitucheng
Rd., Haidian District, Beijing 100876, China
Journal of Signal Processing Systems (2018) 90:805–806