Article
A Feasibility Analysis of an Application-Based Partial
Initialization (API) Protocol for Underwater Wireless
Acoustic Sensor Networks
Changho Yun
1
and Suhan Choi
2,
*
1
Division of Ocean System Engineering, Korea Research Institute of Ships & Ocean Engineering (KRISO), 32,
Yuseong-daero 1312beon-gil, Yuseong-gu, Daejeon 34103, Korea; sgn0178@kriso.re.kr
2
Department of Mobile System Engineering, Dankook University, 152, Jukjeon-ro, Suji-gu, Yongin-si,
Gyeonggi-do 16890, Korea
* Correspondence: suhanc@dankook.ac.kr; Tel.: +82-31-8005-3243
Received: 24 August 2020; Accepted: 30 September 2020; Published: 2 October 2020
Abstract: Initialization methods for underwater wireless acoustic sensor networks (UWASNs) have
been proposed as a subset of other network protocols under the simple assumption that all the
nodes in the network can be initialized at once. However, it is generally time- and energy-intensive
to initialize all nodes in a UWASN due to unstable underwater channel conditions. To improve
network efficiency, we propose the Application-based Partial Initialization (API) protocol, which
initializes only the same number of nodes as the number of activated nodes required to run a specific
application. Reducing the number of active nodes is also particularly advantageous underwater since
the replacement of batteries is costly. To the best of our knowledge, the API is the first approach that
initializes nodes partially according to applications. Thus, we investigate the feasibility of the API for
a UWASN by analyzing its performance via simulations. From the results, it is shown that the API
provides similar data statistics compared with the conventional full initialization that initializes all
nodes. Moreover, the API outperforms the full initialization in terms of the initialization time and
message overhead performances.
Keywords:
initialization protocol; underwater wireless acoustic sensor network; partial
initialization; application
1. Introduction
Underwater wireless acoustic sensor networks (UWASNs) are considered adequate communication
infrastructures because acoustic communications can guarantee more reliable communication with
a longer propagation distance than optical and radio-frequency (RF) counterparts [
1
] in underwater
environments. Therefore, UWASNs have been adopted widely for diverse applications including
scientific observation, the exploitation of ocean resources, disaster detection, military surveillance and
subsea construction monitoring [2,3].
In our study, we focus on observation-based applications that deploy multiple nodes underwater
and constantly obtain sensed data from them. By using the statistics of the data set sensed and collected
by multiple underwater nodes, we can derive the desired information and predict future trends of
underwater phenomena.
Let us consider two cases in terms of the method to obtain data from nodes. One is to obtain
data from all the nodes in the network. We call this “Case 1”. The other is to obtain data from only
some of them: “Case 2”. When the sensed data varies significantly depending on region and time,
for example, when investigating ship accidents, searching for drowned persons, or engaging in military
surveillance, all nodes must be activated as in Case 1. On the other hand, in the case of observing the
Sensors 2020, 20, 5635; doi:10.3390/s20195635 www.mdpi.com/journal/sensors
