Article
UAV Based Relay for Wireless Sensor Networks in
5G Systems
Shu Fu
1,
*
ID
, Lian Zhao
2
ID
, Zhou Su
3
and Xin Jian
1
1
The College of Communication Engineering, Chongqing University, Chongqing 400044, China;
jianxin@cqu.edu.cn
2
The Department of Electrical and Computer Engineering, Ryerson University, Toronto, ON M5B 2K3,
Canada; lzhao@ee.ryerson.ca
3
The School of Mechatronic Engineering and Automation, Shanghai University, Shanghai 200444, China;
zhousu@ieee.org
* Correspondence: shufu@cqu.edu.cn
Received: 29 June 2018; Accepted: 21 July 2018; Published: 25 July 2018
Abstract:
Relay is one of the most significant issues in smart industrial wireless sensor networks
(WSN) due to the low transmitting power of sensors. By relay, the signals of sensors can
be concentrated at the relay and further transmitted to the base station for decreasing energy
consumption in the system. In the past decades, the relay in WSN is generally one super
sensor with large transmitting power. However, the placement of the super sensor is static,
which leads to the instability of performance in WSN under the time-varying wireless environment.
Fortunately, unmanned aerial vehicles (UAV) can provide an effective leverage to improve the
environment-adaptation in WSN compared to the static relay in WSN. In this paper, we employ
UAV as the relay in WSN, which can move in three-dimensional space to possess a better position to
minimize the system power consumption. We use a simple case study to demonstrate the effectiveness
of UAV in WSN. Extended simulations are also given to verify the preferable performance of the
UAV based relay in WSN.
Keywords: wireless sensor networks; unmanned aerial vehicle; relay; power consumption
1. Introduction
Smart industrial wireless sensor networks (WSN) [
1
–
3
] have been widely laid out to meet
the ever-increasing demands of the next generation of wireless communication. Smart industrial
wireless sensor networks can provide real-time service of smartphones, road condition information
for vehicle networks, video-game consoles, surveillance cameras, augmented reality devices and
wearable electronics, etc. [
4
], which can effectively support the implementation of an Internet of Things
(IoT) based on the fifth generation of the wireless network (5G) [
5
]. Most types of sensors possess
simplification features and low transmitting power to cut down on the investment cost in practice.
However, when the sensors transmit signals to the base station (BS) over a long distance, the low
power of the sensors may lead to a poor received signal to interference plus noise ratio (SINR) at the
BS side. Relay [
6
–
10
] is a useful technology to receive and retransmit the signals of sensors to the BS,
where the relay can enhance the strength of signals received at the BS side. In reference [
5
], the authors
pointed out that a relay can achieve anti-fading capability in WSN. In reference [
6
–
9
], power splitting
is investigated in a relay. In reference [10], relay-based routing protocol techniques are considered.
Most of the existing works regarding a relay in WSN employ a static or semi-static relay to
retransmit the signal of the sensors to the BS. This lacks flexibility of the relay position to better adapt
to the time-varying wireless environment. Unmanned aerial vehicles (UAV) [
11
–
15
] provide a useful
Sensors 2018, 18, 2413; doi:10.3390/s18082413 www.mdpi.com/journal/sensors
