Article
Analysis of Throughput and Delay for an Underwater
Multi-DATA Train Protocol with Multi-RTS
Reception and Block ACK
Ho Young Hwang
School of Computer and Information Engineering, Kwangwoon University, Seoul 01897, Korea;
hyhwang@kw.ac.kr; Tel.: +82-2-940-8265
Received: 28 September 2020; Accepted: 10 November 2020; Published: 12 November 2020
Abstract:
We propose an underwater multi-DATA train protocol with multi-RTS reception and block
ACK (BACK) for underwater acoustic sensor networks. Due to long underwater acoustic propagation
delay, some RTS frames may not overlap at a sink node, even if the RTS frames were sent to the sink
node simultaneously by different sensor nodes. We consider that our underwater sink node can
recover these nonoverlapping RTS frames. Since our RTS frame contains ID of the RTS sending node
and a timestamp, the sink node calculates the propagation delay between the RTS sending node and
the sink node, then broadcasts a CTS frame. Since our CTS frame contains when each RTS sending
node can transmit a DATA frame to the sink node, multiple DATA frames transmitted by different
sensor nodes can be formed as a train at the sink node. We also propose an underwater BACK
protocol which is analogous to our proposed underwater multi-DATA train protocol. We analyze
normalized throughput and mean access delay of our proposed protocols and the conventional
protocols. The analytical and simulation results show that our analysis is accurate and our proposed
protocols outperform the conventional protocols. Our proposed protocol can shorten the delay and
increase the throughput via the multi-DATA train, multi-RTS reception, and BACK.
Keywords:
underwater wireless sensor networks; underwater acoustic propagation delay; medium access
control protocol
1. Introduction
In recent years, underwater communications and networking technologies for underwater wireless
sensor networks (UWSNs) and the Internet of Underwater Things (IoUT) have been studied and
developed actively by academia and industrial researchers due to their challenges and applications
[1–4]
.
Felemban et al. [
1
] provided a comprehensive survey on UWSN applications including water quality
monitoring, habitat monitoring, fish farming, natural resource explorations, oil and gas pipeline monitoring,
disaster forecasting (such as volcanoes and earthquakes), military surveillance, mine detection, and assistive
navigation. Kao et al. [
2
] presented a comprehensive study on IoUT applications, challenges for IoUT,
and UWSN channel models. For the main challenges for IoUT, they discussed the differences between
UWSNs and territorial (or terrestrial) wireless sensor networks (TWSNs) including transmission media,
rate, range, and propagation speed.
Jouhari et al.
[
3
] provided a survey on localization protocols
and enabling technologies for UWSNs and IoUT including magneto-inductive communications and
acoustic communications. In [
3
], the magneto-inductive communications can be used for short range
and high data rate while the acoustic communications can be used for long range and low data rate.
Ali et al. [
4
] presented a survey of technical issues and future directions for electromagnetic, optical,
and acoustic communications in underwater environments. They also presented related issues of
UWSNs and emerging technologies in underwater environmental communications.
Sensors 2020, 20, 6473; doi:10.3390/s20226473 www.mdpi.com/journal/sensors
