Sensors2020,20,6473;doi:10.3390/s20226473 www.mdpi.com/journal/sensors
Article
AnalysisofThroughputandDelayforan
UnderwaterMulti‐DATATrainProtocolwith
Multi‐RTSReceptionandBlockACK
HoYoungHwang
SchoolofComputerandInformationEngineering,KwangwoonUniversity,Seoul01897,Korea;
hyhwang@kw.ac.kr;Tel.:+82‐2‐940‐8265
Received:28September2020;Accepted:10November2020;Published:12November2020
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
propagationdelay,someRTSframesmaynotoverlapatasinknode,eveniftheRTSframeswere
senttothesinknodesimultaneously
bydifferent sensornodes.Weconsiderthatourunderwater
sinknodecan recoverthesenonoverlapping RTSframes.Sinceour RTS frame containsIDof the
RTS sending node and a timestamp, the sink node calculates the propagationdelay between the
RTSsendingnodeandthesinknode,thenbroadcastsa
CTSframe.SinceourCTSframecontains
wheneachRTSsendingnodecantransmitaDATAframetothesinknode,multipleDATAframes
transmittedbydifferentsensornodescanbeformedasatrainatthesinknode.Wealsoproposean
underwater BACK protocol which is analogous to our
proposed underwater multi‐DATA train
protocol.Weanalyzenormalizedthroughputandmeanaccessdelayofourproposedprotocolsand
theconventionalprotocols.Theanalyticalandsimulationresultsshowthatouranalysisisaccurate
and our proposed protocols outperform the conventional protocols. Our proposed protocol can
shortenthedelayandincrease
thethroughputviathemulti‐DATAtrain,multi‐RTSreception,and
BACK.
Keywords:underwaterwirelesssensornetworks;underwateracousticpropagationdelay;medium
accesscontrolprotocol
1.Introduction
In recent years, underwater communications and networking technologies for underwater
wirelesssensornetworks(UWSNs)andtheInternetofUnderwaterThings(IoUT)havebeenstudied
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
includingwaterqualitymonitoring,habitatmonitoring,fishfarming,naturalresourceexplorations,
oilandgaspipeline monitoring,disaster forecasting(suchas volcanoesandearthquakes),military
surveillance,minedetection,andassistivenavigation.Kaoetal.[2]presentedacomprehensivestudy
onIoUTapplications,challengesforIoUT,andUWSNchannelmodels.For
themainchallengesfor
IoUT,theydiscussedthedifferencesbetweenUWSNsandterritorial(orterrestrial)wirelesssensor
networks(TWSNs)includingtransmissionmedia,rate,range,andpropagationspeed.Jouharietal.
[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 canbe used forlong range and lowdata rate. Ali et al.[4] presented a survey of
technical issues andfuturedirectionsfor electromagnetic,optical,andacousticcommunicationsin
