an underwater wireless sensor network with realistic radio

Hindawi Publishing CorporationInternational Journal of Distributed Sensor NetworksVolume 2013 Article ID 508708 9 pageshttpdxdoiorg1011552013508708

Research ArticleAn Underwater Wireless Sensor Network with Realistic RadioFrequency Path Loss Model

Ghaith Hattab Mohamed El-Tarhuni Moutaz Al-Ali Tarek Joudeh and Nasser Qaddoumi

Department of Electrical Engineering American University of Sharjah United Arab Emirates PO Box 26666 Sharjah UAE

Correspondence should be addressed to Mohamed El-Tarhuni mtarhuniausedu

Received 2 November 2012 Revised 15 January 2013 Accepted 25 January 2013

Academic Editor Nirvana Meratnia

Copyright copy 2013 Ghaith Hattab et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We propose an Underwater Wireless Sensor Network (UWSN) for near-shore applications using electromagnetic waves (EM) Wealso introduce a realistic path lossmodel for estimating the attenuation encountered by EMwaves in underwater environmentsTheproposed model takes into account the variation of the seawater complex-valued relative permittivity with frequency in contrast toprevious work that treats the permittivity as a real-valued constant parameter Furthermore the proposed model accounts for theimpedance mismatch at the seawater-air boundary which results in a more realistic estimate of the signal attenuation Simulationresults show the expected signal levels underwater for different scenarios A prototype implementation to measure the path loss isalso presented

1 Introduction

There has been a great interest in developing under-water wireless communication systems using electromag-netic waves such as Underwater Wireless Sensor Net-works (UWSNs) Such networks could be used for mon-itoring near-shore variations in seawater coastal surveil-lance autonomous underwater vehicle (AUV) operationsenvironmental research and so forth [1] The interest inEM underwater communications is motivated by severalfeatures such as the support of high data rates and thelow propagation delay This will reduce the transmissionduration which will reduce the power consumption andconsequently it will prolong the lifetime of the nodes [2]Also EM waves are insensitive to the disturbances in thephysical environment [1] Moreover the sensor nodes havebecome affordable in very large quantities as well as beingself-operatedThey can be randomly deployed over the regionof interest (eg scattered by an airplane over a hostileenvironment) These advantages incur low installation andmaintenance cost compared to the existing communicationsystems

Acoustic waves on the other hand remain the prevalentexisting underwater communication mechanism in deep

aquatic environments since they can propagate for longerdistances However for near-shore applications significanthuman activities and ambient noise severely affect under-water acoustic communication systems (eg congested envi-ronments like harbours and ports) In addition underwateracoustic channels are characterized by the harsh physicallayer conditions which result in low data rate capabilitieshigh propagation delay and high bit error rate (BER) Forinstance sound waves use very low frequencies for signaltransmission and thus have very limited bandwidth whichresults in very low data rates In addition with a propagationspeed of 1500ms sound waves cause a significant delay insignal transmission These aforementioned challenges limitthe possible applications provided by acoustic systems Thatis it is impractical to implement acoustic systems for bothnear-shore applications and real-time applications [3]

To overcome the problems faced by acoustic wave basedsystems cables are commonly deployed for reliable trans-mission near the shore However cable-based systems sufferfromhigh cost of installation and frequent need of calibrationand maintenance Other solutions based on optical com-munications have also been proposed such as AquaOpticalin [4] where several optical modems are developed forpoint-to-point communications underwater However the

2 International Journal of Distributed Sensor Networks

Table 1 A Comparison between different underwater transmission media

EM waves Acoustic waves Optical wavesPropagation speed High Very slow Very highLine of sight (LOS) Not required Not required Required with precise alignment of nodesImpact of environment

(ambient noise turbidity temperature changes etc) Minimal High High

Achievable data rates High Very low Very highNetwork coverage Short range Very long range Very short rangeImpact on marine life Not known Negative Not known

long-range modem is currently very expensive (it costsaround US$1200) and thus it is implausible to implementfor large-scale networks A cheaper short-range modem isalso developed but it covers few meters and as well it hasworse performance in terms of signal detection Finally it isobserved in [4] that the turbidity of seawater severely limitsthe achievable data rates In general optical communicationsystems suffer from the need for accurate alignment betweenthe optical transmitter and receiver they are susceptible toparticles and marine fouling (ie turbidity of seawater) andoptical waves do not smoothly cross seawater-air boundary[1]

EM waves outperform both acoustic and optical wavesin shallow water applications as they tolerate ambient noiseturbidity and temperature changes Furthermore EM wavesallow for much lower propagation delay and higher data rates(Mbps range) as compared to acoustic waves These featuressupport real-time applications where different forms of datacould be transmitted (text images and videos) and hencenew horizons for underwater applications become possibleFor instance UWSN could be deployed for AUVs whererobots could get faster commands from the base station Itcould be used for coastal surveillance where cameras couldbe distributed all over the shore at certain depths to monitorhuman activities marine life or any physical phenomenonOther applications include monitoring of coastal erosionprediction of natural disasters and many other real-timeapplications that require high data rates In addition thesesensors could be implemented as body area networks fordivers to monitor their health oxygen level equipment andso forth All these features motivate the use of EM wavesfor both near-shore applications and real-time applicationsTable 1 provides a brief comparison of the different underwa-ter wireless communication systems

The idea of underwater EM wave communications wasenvisioned since the 1950s where researchers were interestedin using radio for submarine communications but it wasabandoned because of the limited communication range dueto the very high conductivity in seawater [5] Neverthelessthe recent advancements in electronics and the affordablecost of wireless sensor networks have triggered a new interestin using EM waves for underwater applications Severalexperiments for UWSNs have recently been implemented in[6] to compare different topologies for underwater networksand to obtain experimental data for signal attenuation atdifferent operating frequencies In addition Al-Shammarsquoa

et al present in [6] a very simple attenuation model as afunction of frequency In [7] a channel model for freshwaterenvironment is proposed We remark that the results in [7]are not applicable for the more practical scenario in seawaterapplications because of the relatively low salinity of freshwatercompared to that of seawater In [2] Uribe and Grote presenta simple analytical model based on Maxwellrsquos equationsHowever the model is merely for the attenuation loss due toseawater conductivity (ie the reflection loss at the seawater-air boundary is not considered) and it assumes a fixed valueof seawater permittivity To the best of our knowledge therehas been no other path loss models developed for EM wavespropagating in seawater and most of the channel modelsfor underwater communications are developed for acousticwaves

In this paper we propose a UWSN for near-shore appli-cations We introduce a more realistic path loss model forEM waves propagating in seawater that considers both thevariation of the seawater complex-valued relative permittivitywith frequency and the impedancemismatch at the seawater-air boundary The rest of this paper is organized as followsSection 2 describes the proposed UWSN structure Section 3outlines the electric properties of seawater and their impacton the propagation of EM waves The proposed underwaterpath loss model is developed in Section 4 Simulation andexperimental results are presented in Section 5 Finallyconclusions are summarized in Section 6

2 Proposed UWSN Description

The architecture of the proposed UWSN is shown in Figure 1It is composed of different nodes that communicate usingEM waves to send information from sensor nodes to a sinknode through one or more intermediate nodes The sensornodes might be anchored at the seabed to collect application-specific data or could be moving as the case for AUVs Thedata is then transmitted to the intermediate nodes that arescattered in the coverage area of theUWSNThe intermediatenodes need to be anchored at different locations and heightswithin the area of interest They receive the EM signalamplify it and then retransmit it again to other intermediatenodes Finally a buoy node receives the signal at the seawatersurface and forwards it to the sink node The block diagramof the system is shown in Figure 2

The number and distances between intermediate nodesdepend on the attenuation faced by the EM waves as they

International Journal of Distributed Sensor Networks 3

Intermediatenode

Intermediatenode Direct

line of sight

Seawater

Seabed

Air Buoy nodeSink node

Sensor nodes

Figure 1 The network structure of one of the proposed schemes(Scheme II)

Data processing Tx (modem) Sensing

Memory

Sensor node

Amplification digital processing

memory

Rx (modem) Tx (modem)

Buoyintermediate node

Digital processing memory


Sink node (destination)

Figure 2 A detailed block diagram for the overall system

propagate through seawater To cover the same area ofinterest more nodes are required when using EM wavescompared to acoustic waves (ie higher node density) Thisis due to the signal attenuation which depends on theelectric properties of seawater Another important factor thatalso affects signal attenuation is the implementation of thebuoy node We consider two schemes for the buoy nodedesign

Scheme I uses one antenna at the buoy node that isnot immersed in seawater and hence the signal needs tocross the seawater-air boundary to be received by the buoynode This results in significant attenuation of the signal andhence needsmore amplification at the intermediate nodes Toalleviate such a problem Scheme II uses a buoy node withtwo antennas The first antenna is immersed in seawater andthus it receives the signal underwater from the intermediatenodes Then the buoy node amplifies the signal and thenretransmits it to the sink through the second antenna whichis implemented above seawater Scheme II provides for lessattenuation and therefore it is preferred to implement All ofthese observations are going to be discussed in details in thenext sections

3 Electric Properties of Seawater

The propagation of EM waves in seawater is significantlydifferent from that on air because seawater has distinct elec-trical properties that severely impact the signal propagationThus in order to develop a realistic path loss model for EMwave propagation in seawater these properties need to bediscussed

31 Conductivity The conductivity of a medium affects thetransmission of an EM wave through that medium Specif-ically the transmitted signal will face more attenuation asthe conductivity of the medium increases Seawater has highconductivity that varies depending on the presence of ions init For instance the conductivity of Red Sea is 8 Smwhereas itis only 2 Sm in the Arctic For typical seawater it is commonstandard to use a value of 4 Sm for seawater conductivity[5 8 9] This is 400 times higher than the conductivity offreshwater which is typically around 001 Sm [7]

32 Permeability and Permittivity Permeability is the abilityof the medium to store magnetic energy Since seawater is anonmagnetic medium it has the same permeability as freespace 120583seawater = 120583freespace [8] On the other hand therelative permittivity also known as the dielectric constantdescribes the ability of a medium to transmit an electricfield [8] The relative dielectric permittivity of seawater (120576

119903)

is usually set to 81 [6 9 10] However this assumptionis not accurate since the relative permittivity is in generalcomplex-valued and depends on other factors such as thesalinity of seawater temperature and carrier frequency [11]Debyersquos model considers all the factors that affect both thereal and the imaginary part of the relative permittivity [12]In this paper salinity is assumed to be a constant value of 35PSU which is the average value measured by Dubai CoastalZone Monitoring at the local shores of Dubai [13] Figure 3illustrates the variation of the real part of the dielectricconstant of seawaterwith frequency at different temperaturesThus the assumption made by pervious work in [6 10] thatthe real dielectric constant is a constant regardless of theseawater temperature is not realistic Figure 3 shows also thatfor all practical frequency range it is safe to assume that thereal part of the dielectric is constantThis statement howeveris not applicable to the imaginary part of the dielectricconstant as shown in Figure 4 Although the imaginarypart is independent of the temperature it is relatively largeat lower frequencies yet it decreases exponentially as thefrequency increases Hence the assumption made in [6] thatthe imaginary part of the dielectric constant is negligibleis again not realistic Thus assuming a constant real part(independent of the temperature) as well as a negligibleimaginary part for the dielectric constant would lead toinaccurate path loss model for EM waves in seawater (see theappendix for permittivity calculations)

33 The Intrinsic Impedance The intrinsic impedance is amedium property that describes the ratio of the electricfield strength (E) to the magnetic field strength (H) [8] The


50

55

60

65

70

75

Real

die

lect

ric co

nsta

nt o

f sea

wat

er

Frequency (Hz)

105

106

107

108

109

1010

Temperature = 15∘CTemperature = 25∘CTemperature = 35∘C

Figure 3The real dielectric constant of seawater (salinity= 35 PSU)

Imag

inar

y di

elec

tric

cons

tant

of s

eaw

ater

Frequency (Hz)

105

105

104

103

102

101

106

106

107

108

109

1010


Figure 4 The imaginary dielectric constant of seawater (salinity =35 PSU)

intrinsic impedance of air is found to be 1205780asymp 377Ω However

the intrinsic impedance of seawater is complex-valued and itis expressed as

120578 =EH= radic

119895120596120583

120590 + 119895120596120576 (1)

where 120583 is the permeability 120576 is the permittivity 120590 is theconductivity and 120596 = 2120587119891 is the angular frequency Acomplex intrinsic impedance indicates a phase difference

between E and H in the transverse electromagnetic wave(TEM) Both the magnitude and the angle of intrinsicimpedance of seawater are demonstrated in Figure 5 Thephase difference is constant for a wide range of frequencies119891 ⩽ 100MHz and it is equal to 1205874 which is a typicalphase difference in a conducting medium [8] Figure 5 showsthat the intrinsic impedance magnitude is relatively smallcompared to the impedance of air Thus the large impedancemismatch between seawater and air would cause significantsignal reflections at the seawater-air boundary as indicatedby the reflection coefficient

The reflection coefficient is expressed as [8]

Γ =119864reflected119864incident

=1205780minus 120578seawater

1205780+ 120578seawater

(2)

and the transmission coefficient for normal incidence isdefined as [8]

119879 =21205780

1205780+ 120578seawater

(3)

The reflection and transmission coefficients for seawaterare demonstrated in Figure 6 Note that we have 119879 = 1 + Γ

4 Channel Model

For proper deployment of any wireless communication sys-tem it is critical to have accurate channel characterizationChannel modeling provides important information aboutthe received signal strength (ie path loss) and multipathstructure In terrestrial WSNs with air as the propagationmedium numerousworks have been done to develop realisticchannel models However due to the aforementioned electricproperties of seawater direct relation between seawater andair cannot be established Hence we aremotivated to proposea new model for the underwater channel

Path loss is a fundamental parameter in characterizingthe wireless channel It represents the difference between thetransmitted signal power and the received signal power [14]Path loss represents a large-scale channel modeling becausein terrestrial wireless systems it is observed for large dis-tances (hundreds of wavelengths) However in the proposedunderwater network structure the distances between thenodes are expected to be very small (few meters) but thepath loss underwater would be comparable with the path lossof hundreds of meters in air as we will demonstrate in thissection The path loss considered in this work is expressed indB as [7]

119875119871 = 119871120572120576+ 119871119877 (4)

where 119871120572120576

is the attenuation loss in seawater due to seawaterconductivity and complex permittivity (in dB) and 119871

119877is the

reflection loss at the seawater-air boundary (in dB) due to theimpedance mismatch between the two mediums

In order to realize the impact of the complex permittivityon the attenuation factor the attenuation loss is derived fromthe propagation constant 120574 which is expressed as [8]

120574 = 119895120596radic120583120576 minus 119895120590120583

120596= 120572 + 119895120573 (5)


0

10

20

30

40

50

Frequency (Hz)

10

0

20

30

40

50

AngleMagnitude

104105106107

108109

1010

Intr

insic

impe

danc

e mag

nitu

de

Intr

insic

impe

danc

e ang

le (d

eg)

Figure 5 Seawater intrinsic impedance with frequency variations

0

05

1

15

2

25

Tran

smiss

ion

coeffi

cien

t mag

nitu

de

0

05

1

15

2

25

Refle

ctio

n co

effici

ent m

agni

tude

Transmission coefficientReflection coefficient

Frequency (Hz)

104105106107

108109

1010

Figure 6 Magnitude of transmission and reflection coefficients atseawater-air boundary

where 120572 is the attenuation factor (in Neperm) and 120573 is thephase constant per unit length Taking the real part of thepropagation constant we obtain the attenuation loss (in dB)as

119871120572120576= R (120574) times

20

ln (10)times 119863 (6)

where 119863 is the separation distance between the transmittingand the receiving nodes Figure 7 illustrates the attenuationloss 119871

120572120576with the variations of the carrier frequency It is

clear that the attenuation loss is very high and this is dueto the very high conductivity of seawater which severelyattenuates the propagating EM wave Such property sets atight constraint on the separation distance between the nodes

0

50

100

150

200

250

300

Frequency (Hz)

Atte

nuat

ion

loss

(dB

m)

Uribe and GroteAl-Shammarsquoa et al

104

105

106

107

119871120572120576

Figure 7 Attenuation loss with frequency variations

Also it is evident that the complex permittivity has a directimpact on the signal attenuation in seawater We remark thatthe results of Uribe and Grote in [2] are originally madeas a function of distance and their model is tested for fewfrequencies with 120590 = 1 However we used our parameters tomake the comparison appropriate Also Al-Shammarsquoa et almodel in [6] is independent of seawater permittivity

On the other hand signal reflection due to impedancemismatch has a major impact on the EM wave propagationbetween different mediums Impedance matching is veryimportant to minimize the reflection at the boundary andmaximize power transfer [8] Since we have identified amismatch in intrinsic impedance between seawater and aira high-signal reflection at the boundary is expected Thetransmitted power can be written as [7]

119875119905= R

100381610038161003816100381611986411989410038161003816100381610038162

2120578lowastseawater |119879|2

119890minus2120572119863

(7)

where 119864119894is the incident electric field and 120578

lowast

seawater is theconjugate of the intrinsic impedance of seawater Hence thereflection loss at the seawater-air boundary in dB can beshown to be

119871119877= 10 log(|119879|2R

1205780

120578seawater) (8)

From (4) the total path loss in dB is expressed as

119875119871 = R (120574) times20

ln (10)times 119863 + 10 log(|119879|2R

1205780

120578seawater)

(9)

We remark that (9) assumes a direct link between thesensor node underwater and the buoy node at the surface Incase there is a relay (ie intermediate node) in between then


0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010

Figure 8 Reflection loss with variations of frequency

careful changes must be made Figure 8 illustrates the high-signal attenuation at the seawater-air boundary It shows thatthe reflection loss decreases dramatically as the frequencyincreases from 100KHz to 1GHz and then it remains almostconstant for frequencies higher than 2GHz This could beexplained by noting that the magnitude of the intrinsicimpedance of seawater is directly proportional to the carrierfrequency that is as the frequency increases the impedanceof seawater increases as shown in Figure 5 and hence the gapbetween the impedance of seawater and air decreases whichwill ultimately reduce the reflection losses at the boundaryHowever Figure 5 indicates that the impedance of seawaterconverges to a constant value for further increase in theoperating frequency and hence the reflection loss wouldbe approximately constant at those frequencies (119891 ⩾ 2GHz)We remark that the significant reduction in the reflectionloss (up to 25 dB) could be tempting to operate the networkat the gigahertz range but the total path loss is actuallymuch higher due to the attenuation caused by electricproperties of seawater Figure 9 illustrates that the total pathloss 119875119871 with frequency variations at different separationdistances between the transmitter and the receiver Unlikethe reflection loss the total path loss exponentially increaseswith frequency because of the very high-attenuation lossesunderwater Also it is clear that a small increase of theseparation distance would have a major impact on the totalloss and hence this would put stringent requirements on thedistance between the network nodes

Finally a comparison between our model and the modelpresented in [7] is demonstrated in Figure 10 Both mod-els implement Debyersquos models for seawater and freshwaterrespectively It is observed that the high conductivity ofseawater drastically increases the path loss

5 Simulation and Experimental Results

In this section MATLAB simulations are presented for thepath loss and bit error rate (BER) for the proposed UWSN

0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107

Figure 9 Total path loss with frequency variations at differentdepths

Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109

Seawater (120590 = 4Sm)Freshwater (120590 = 001 Sm)

Figure 10 Total path loss comparison between seawater andfreshwater

We assume that the sensor node is located at the seabed andthe signal is sent directly to the buoy node located at thesurface of the water The buoy node detects the transmitteddata and then retransmits it again to the sink node Both casesfor a buoy node with nonimmersed antenna (scheme I) andimmersed antenna (scheme II) are simulatedWithout loss ofgenerality Quadrature Phase Shift Keying (QPSK) is used asthe modulation scheme with square root-raised cosine pulseshapeTheQPSK signal is then transmitted through a channelwith a path loss according to the model developed in (9)The signal is also assumed to undergo flat fading with Rician


minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107

Figure 11 The estimated received power of the proposed schemes

distribution since there are generally no obstacles betweenthe transmitter and receiver The channel is also assumed tohave very slow variation with time (low Doppler) since themobility of the nodes is limited The movement of the nodescould be caused by the dynamic underwater environmentsuch as the water current or the movement of surroundingobjects Using the data provided by Dubai Coastal ZoneMonitoring the maximum current speed is approximatelyequal to 02ms [13] The Doppler shift is expressed as [14]

Δ119891 =119891 sdot 119907rel119907

(10)

where 119891 is the transmitted signal frequency in Hz 119907rel isthe mobility of the surrounding environment relative to thereceiver inms and 119907 is the speed of the EMwave in seawaterand it is given by [8]

119907 =119888

radic120583119903120576119903

(11)

where 119888 is the speed of light 120583119903and 120576119903are the relative per-

meability and relative permittivity of seawater respectivelyHence the Doppler shift will be limited to about 015Hz ata carrier frequency of 25MHz which leads to slow fadingconditions [14 15]

Figure 11 illustrates the received signal power for thetwo schemes for a transmitter at a depth of 1 meter anda transmitted power of 0 dBm It is clear that using animmersed antenna at the buoy node significantly reduces thesignal power loss This could be exploited either to increasethe distance between nodes or use a higher operating fre-quency to achieve higher data rates The improvement in theperformance ismainly due to the elimination of the reflectionlosses at the seawater-air boundary Table 2 compares the pathloss of the two proposed schemes at different frequenciesThe path loss gap between the two schemes decreases as thefrequency increases because the reflection losses decrease at

Table 2 Path loss comparison between the two schemes

Carrier frequency(MHz)

Scheme I(dB)

Scheme II(dB)

Path loss reduction()

005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5

higher frequencies Nonetheless it is evident that at any givenoperating frequency Scheme II is more power efficient Thisis very crucial since power management is one of the majorchallenges in UWSN design and hence by just making thereceiver antenna of the buoy node immersed in seawater wemay prolong the battery life of the nodes which in return willreduce the regular maintenance and the battery replacementprocess On the other hand if we decide to send power at thesame level we can further increase the separation distancebetween the nodes (depending on the receiver sensitivity)which in return will either expand the communication rangeor reduce the number of nodes required to cover the samecoverage area Figure 12 shows the BER performance for thesystem with immersed antenna case The result shows thatthe BER improves as the energy per bit-to-noise power ratio(1198641198871198730) increases

Finally we have implemented a prototype to measure thepath loss for the two schemes A 12 times 10 times 10m3 tank isfilled with seawater mixed with a small portion of freshwaterThe container is made up of Aluminum and covered with aplastic sheet from the inside to ensure that the conductivityof the surface is minimal An antenna which is insulated byNylon sheet is installed on the inner side of the containerat a height of 20 cm from the bottom surface An arbitraryfunction generator is connected to the underwater antennaand a signal is transmitted at different carrier frequencies Inboth schemes the transmitted power is set to 118 dBm andthe separation distance between the transmitter antenna andthe receiver antenna is 12 metersThe signal is detected at thesurface using spectrum analyzer A comparison between thepath loss of Scheme I and Scheme II is shown in Figure 13

The results confirm that the path loss of the externalreceiver antenna is higher than the one with the immersedantenna This is due to the reflection at the surface as sug-gested earlier It is also clear that as the frequency increasesthe path loss increases in agreement with the simulationresults We remark that our experimental results cannotbe compared directly with the simulation results for thefollowing reasons First the range of frequencies used is notprecisely within the available antennasrsquo operational range


5 10 15 20 25 30Energy per bitminustominusnoise ratio (dB)

Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5

Figure 12 The simulated BER of the underwater channel

4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II

Figure 13 The path loss of the two implemented schemes

Second we have mixed a portion of freshwater with seawaterwhich in return will affect the salinity of the medium Thirdthe temperature of the medium is different We assumed atemperature of 25∘C in the simulations Nevertheless theexperiment provides insights on the importance of imple-menting an immersed antenna at the buoy node It is clearfrom the experimental results that immersing the antennasignificantly reduces the path loss (up to 20 dB which isalso demonstrated in the simulation results) Another insightis that at higher frequencies the gap between Scheme Iand Scheme II reduces because the reflection loss is alsodecreased This reduction is due to the fact that the intrinsicimpedance of seawater increases as the frequency increasesThus the mismatch of impedances between seawater and airdecreases This is what we have also demonstrated theoreti-cally and in the simulations

6 Conclusion

In this paper an underwater wireless sensor network usingelectromagnetic waves is proposed A realistic model forthe path loss underwater has been developed The effectof the signal reflection at the seawater-air boundary hasalso been considered Two schemes are proposed for thebuoy node located at the surface of the water one basedon nonimmersed antenna and the other with immersedantenna The proposed schemes are simulated under slowfading channel conditions and both the path loss and biterror rate performance are presented Finally a prototype tomeasure the path loss is implemented

Appendix

Permittivity Calculations

In saline water the real dielectric constant is expressed as [12]

1205761015840

sw = 120576swinfin +120576sw0 minus 120576swinfin

1 + (2120587119891120591sw)2 (A1)

and the imaginary part is expressed as [12]

12057610158401015840

sw =2120587119891120591sw (120576sw0 minus 120576swinfin)

1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840

sw are the real and imaginary dielectricconstants of saline water respectively 120576sw0 is the staticdielectric constant at low frequency 120576swinfin is the dielectricconstant at high-frequency limit 120576

0= 885 times 10

minus12 Fm is thepremittivity of free space 120590 is the conductivity and 120591sw is therelaxation time 120576swinfin is independent of salinity and hence120576swinfin = 120576waterinfin = 49 [12] Whereas 120576sw0 depends on boththe salinity (119878sw) and the temperature (119879) according to thefollowing relation

120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where

120576sw0 (119879 0) = 87134 minus 1949 times 10minus1

119879

minus 1276 times 10minus2

1198792

+ 2491 times 10minus4

1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5

119879 sdot 119878sw minus 3656 times 10minus3

119878sw


1198782

sw minus 4232 times 10minus7

1198783

sw

(A4)

The relaxation time on the other hand is expressed as [12]

120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879

+6938 times 10minus14

1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782

sw + 1105 times 10minus8

1198783

sw

(A6)

The temperature range is 0 le 119879 le 40∘C while the salinity

range is 4 le 119878sw le 35PSU

References

[1] X Che I Wells G Dickers P Kear and X Gong ldquoRe-evaluation of RF electromagnetic communication in underwa-ter sensor networksrdquo IEEE Communications Magazine vol 48no 12 pp 143ndash151 2010

[2] C Uribe and W Grote ldquoRadio communication model forunderwater WSNrdquo in Proceedings of the 3rd InternationalConference on New Technologies Mobility and Security (NTMSrsquo09) Cairo Egypt December 2009

[3] J-H Cui J Kong M Gerla and S Zhou ldquoThe challenges ofbuilding scalable mobile underwater wireless sensor networksfor aquatic applicationsrdquo IEEE Network vol 20 no 3 pp 12ndash182006

[4] M Doniec I Vasilescu M Chitre C Detweiler M Hoffmann-Kuhnt and D Rus ldquoAquaOptical a lightweight device for high-rate long-range underwater point-to-point communicationrdquo inProceedings of the MTSIEEE Biloxi-Marine Technology for OurFuture Global and Local Challenges (OCEANS rsquo09) BiloxiMiss USA October 2009

[5] R KMoore ldquoRadio communication in the seardquo IEEE Spectrumvol 4 no 11 pp 42ndash51 1967

[6] A I Al-Shammarsquoa A Shaw and S Saman ldquoPropagation ofelectromagnetic waves at MHz frequencies through seawaterrdquoIEEE Transactions on Antennas and Propagation vol 52 no 11pp 2843ndash2849 2004

[7] S Jiang and S Georgakopoulos ldquoElectromagnetic wave propa-gation into fresh waterrdquo Journal of Electromagnetic Analysis andApplications vol 3 no 7 pp 261ndash266 2011

[8] M Sadiku Elements of Electromagnetics Oxford UniversityPress New York NY USA 2007

[9] A G MiquelUWB antenna design for underwater communica-tions [MS thesis] Universitat Politecnica de Catalunya 2009


[11] R Somaraju and J Trumpf ldquoFrequency temperature and salin-ity variation of the permittivity of seawaterrdquo IEEE Transactionson Antennas and Propagation vol 54 no 11 pp 3441ndash34482006

[12] F Ulaby R Moore and A Fung Microwave Remote SensingRadar Remote Sensing and Surface Scattering and EmissionTheory Remote Sensing Addison-Wesley ReadingMass USA1981

[13] ldquoDubai coastal zone monitroingrdquo 2012 httpwwwdubaicoastae

[14] T RappaportWireless Communications Principles and PracticePrentice Hall PTR 2002

[15] B Sklar Digital Communications Fundamentals and Applica-tions Prentice-Hall PTR 2001

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

RoboticsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Active and Passive Electronic Components

Control Scienceand Engineering

Journal of



RotatingMachinery


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Submit your manuscripts athttpwwwhindawicom

VLSI Design



Shock and Vibration


Civil EngineeringAdvances in

Acoustics and VibrationAdvances in



Electrical and Computer Engineering

Journal of

Advances inOptoElectronics


Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

SensorsJournal of


Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014


Chemical EngineeringInternational Journal of Antennas and

Propagation




Navigation and Observation



DistributedSensor Networks



Table 1 A Comparison between different underwater transmission media

EM waves Acoustic waves Optical wavesPropagation speed High Very slow Very highLine of sight (LOS) Not required Not required Required with precise alignment of nodesImpact of environment

(ambient noise turbidity temperature changes etc) Minimal High High

Achievable data rates High Very low Very highNetwork coverage Short range Very long range Very short rangeImpact on marine life Not known Negative Not known

long-range modem is currently very expensive (it costsaround US$1200) and thus it is implausible to implementfor large-scale networks A cheaper short-range modem isalso developed but it covers few meters and as well it hasworse performance in terms of signal detection Finally it isobserved in [4] that the turbidity of seawater severely limitsthe achievable data rates In general optical communicationsystems suffer from the need for accurate alignment betweenthe optical transmitter and receiver they are susceptible toparticles and marine fouling (ie turbidity of seawater) andoptical waves do not smoothly cross seawater-air boundary[1]

EM waves outperform both acoustic and optical wavesin shallow water applications as they tolerate ambient noiseturbidity and temperature changes Furthermore EM wavesallow for much lower propagation delay and higher data rates(Mbps range) as compared to acoustic waves These featuressupport real-time applications where different forms of datacould be transmitted (text images and videos) and hencenew horizons for underwater applications become possibleFor instance UWSN could be deployed for AUVs whererobots could get faster commands from the base station Itcould be used for coastal surveillance where cameras couldbe distributed all over the shore at certain depths to monitorhuman activities marine life or any physical phenomenonOther applications include monitoring of coastal erosionprediction of natural disasters and many other real-timeapplications that require high data rates In addition thesesensors could be implemented as body area networks fordivers to monitor their health oxygen level equipment andso forth All these features motivate the use of EM wavesfor both near-shore applications and real-time applicationsTable 1 provides a brief comparison of the different underwa-ter wireless communication systems

The idea of underwater EM wave communications wasenvisioned since the 1950s where researchers were interestedin using radio for submarine communications but it wasabandoned because of the limited communication range dueto the very high conductivity in seawater [5] Neverthelessthe recent advancements in electronics and the affordablecost of wireless sensor networks have triggered a new interestin using EM waves for underwater applications Severalexperiments for UWSNs have recently been implemented in[6] to compare different topologies for underwater networksand to obtain experimental data for signal attenuation atdifferent operating frequencies In addition Al-Shammarsquoa

et al present in [6] a very simple attenuation model as afunction of frequency In [7] a channel model for freshwaterenvironment is proposed We remark that the results in [7]are not applicable for the more practical scenario in seawaterapplications because of the relatively low salinity of freshwatercompared to that of seawater In [2] Uribe and Grote presenta simple analytical model based on Maxwellrsquos equationsHowever the model is merely for the attenuation loss due toseawater conductivity (ie the reflection loss at the seawater-air boundary is not considered) and it assumes a fixed valueof seawater permittivity To the best of our knowledge therehas been no other path loss models developed for EM wavespropagating in seawater and most of the channel modelsfor underwater communications are developed for acousticwaves

In this paper we propose a UWSN for near-shore appli-cations We introduce a more realistic path loss model forEM waves propagating in seawater that considers both thevariation of the seawater complex-valued relative permittivitywith frequency and the impedancemismatch at the seawater-air boundary The rest of this paper is organized as followsSection 2 describes the proposed UWSN structure Section 3outlines the electric properties of seawater and their impacton the propagation of EM waves The proposed underwaterpath loss model is developed in Section 4 Simulation andexperimental results are presented in Section 5 Finallyconclusions are summarized in Section 6

2 Proposed UWSN Description

The architecture of the proposed UWSN is shown in Figure 1It is composed of different nodes that communicate usingEM waves to send information from sensor nodes to a sinknode through one or more intermediate nodes The sensornodes might be anchored at the seabed to collect application-specific data or could be moving as the case for AUVs Thedata is then transmitted to the intermediate nodes that arescattered in the coverage area of theUWSNThe intermediatenodes need to be anchored at different locations and heightswithin the area of interest They receive the EM signalamplify it and then retransmit it again to other intermediatenodes Finally a buoy node receives the signal at the seawatersurface and forwards it to the sink node The block diagramof the system is shown in Figure 2

The number and distances between intermediate nodesdepend on the attenuation faced by the EM waves as they


Intermediatenode


line of sight

Seawater

Seabed


Sensor nodes



Memory

Sensor node


memory













119903)




50

55

60

65

70

75

Real

die

lect

ric co

nsta

nt o

f sea

wat

er

Frequency (Hz)

105

106

107

108

109

1010



Imag

inar

y di

elec

tric

cons

tant

of s

eaw

ater

Frequency (Hz)

105

105

104

103

102

101

106

106

107

108

109

1010





120578 =EH= radic

119895120596120583

120590 + 119895120596120576 (1)






1205780+ 120578seawater

(2)


119879 =21205780

1205780+ 120578seawater

(3)


4 Channel Model



119875119871 = 119871120572120576+ 119871119877 (4)

where 119871120572120576


119877is the



120574 = 119895120596radic120583120576 minus 119895120590120583

120596= 120572 + 119895120573 (5)


0

10

20

30

40

50

Frequency (Hz)

10

0

20

30

40

50

AngleMagnitude

104105106107

108109

1010

Intr

insic

impe

danc

e mag

nitu

de

Intr

insic

impe

danc

e ang

le (d

eg)


0

05

1

15

2

25

Tran

smiss

ion

coeffi

cien

t mag

nitu

de

0

05

1

15

2

25

Refle

ctio

n co

effici

ent m

agni

tude


Frequency (Hz)

104105106107

108109

1010



119871120572120576= R (120574) times

20

ln (10)times 119863 (6)




0

50

100

150

200

250

300

Frequency (Hz)

Atte

nuat

ion

loss

(dB

m)


104

105

106

107

119871120572120576




119875119905= R

100381610038161003816100381611986411989410038161003816100381610038162


119890minus2120572119863

(7)


lowast


119871119877= 10 log(|119879|2R

1205780

120578seawater) (8)


119875119871 = R (120574) times20

ln (10)times 119863 + 10 log(|119879|2R

1205780

120578seawater)

(9)



0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010






0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107


Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109





minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










Intermediatenode


line of sight

Seawater

Seabed


Sensor nodes



Memory

Sensor node


memory













119903)




50

55

60

65

70

75

Real

die

lect

ric co

nsta

nt o

f sea

wat

er

Frequency (Hz)

105

106

107

108

109

1010



Imag

inar

y di

elec

tric

cons

tant

of s

eaw

ater

Frequency (Hz)

105

105

104

103

102

101

106

106

107

108

109

1010





120578 =EH= radic

119895120596120583

120590 + 119895120596120576 (1)






1205780+ 120578seawater

(2)


119879 =21205780

1205780+ 120578seawater

(3)


4 Channel Model



119875119871 = 119871120572120576+ 119871119877 (4)

where 119871120572120576


119877is the



120574 = 119895120596radic120583120576 minus 119895120590120583

120596= 120572 + 119895120573 (5)


0

10

20

30

40

50

Frequency (Hz)

10

0

20

30

40

50

AngleMagnitude

104105106107

108109

1010

Intr

insic

impe

danc

e mag

nitu

de

Intr

insic

impe

danc

e ang

le (d

eg)


0

05

1

15

2

25

Tran

smiss

ion

coeffi

cien

t mag

nitu

de

0

05

1

15

2

25

Refle

ctio

n co

effici

ent m

agni

tude


Frequency (Hz)

104105106107

108109

1010



119871120572120576= R (120574) times

20

ln (10)times 119863 (6)




0

50

100

150

200

250

300

Frequency (Hz)

Atte

nuat

ion

loss

(dB

m)


104

105

106

107

119871120572120576




119875119905= R

100381610038161003816100381611986411989410038161003816100381610038162


119890minus2120572119863

(7)


lowast


119871119877= 10 log(|119879|2R

1205780

120578seawater) (8)


119875119871 = R (120574) times20

ln (10)times 119863 + 10 log(|119879|2R

1205780

120578seawater)

(9)



0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010






0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107


Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109





minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










50

55

60

65

70

75

Real

die

lect

ric co

nsta

nt o

f sea

wat

er

Frequency (Hz)

105

106

107

108

109

1010



Imag

inar

y di

elec

tric

cons

tant

of s

eaw

ater

Frequency (Hz)

105

105

104

103

102

101

106

106

107

108

109

1010





120578 =EH= radic

119895120596120583

120590 + 119895120596120576 (1)






1205780+ 120578seawater

(2)


119879 =21205780

1205780+ 120578seawater

(3)


4 Channel Model



119875119871 = 119871120572120576+ 119871119877 (4)

where 119871120572120576


119877is the



120574 = 119895120596radic120583120576 minus 119895120590120583

120596= 120572 + 119895120573 (5)


0

10

20

30

40

50

Frequency (Hz)

10

0

20

30

40

50

AngleMagnitude

104105106107

108109

1010

Intr

insic

impe

danc

e mag

nitu

de

Intr

insic

impe

danc

e ang

le (d

eg)


0

05

1

15

2

25

Tran

smiss

ion

coeffi

cien

t mag

nitu

de

0

05

1

15

2

25

Refle

ctio

n co

effici

ent m

agni

tude


Frequency (Hz)

104105106107

108109

1010



119871120572120576= R (120574) times

20

ln (10)times 119863 (6)




0

50

100

150

200

250

300

Frequency (Hz)

Atte

nuat

ion

loss

(dB

m)


104

105

106

107

119871120572120576




119875119905= R

100381610038161003816100381611986411989410038161003816100381610038162


119890minus2120572119863

(7)


lowast


119871119877= 10 log(|119879|2R

1205780

120578seawater) (8)


119875119871 = R (120574) times20

ln (10)times 119863 + 10 log(|119879|2R

1205780

120578seawater)

(9)



0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010






0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107


Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109





minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

10

20

30

40

50

Frequency (Hz)

10

0

20

30

40

50

AngleMagnitude

104105106107

108109

1010

Intr

insic

impe

danc

e mag

nitu

de

Intr

insic

impe

danc

e ang

le (d

eg)


0

05

1

15

2

25

Tran

smiss

ion

coeffi

cien

t mag

nitu

de

0

05

1

15

2

25

Refle

ctio

n co

effici

ent m

agni

tude


Frequency (Hz)

104105106107

108109

1010



119871120572120576= R (120574) times

20

ln (10)times 119863 (6)




0

50

100

150

200

250

300

Frequency (Hz)

Atte

nuat

ion

loss

(dB

m)


104

105

106

107

119871120572120576




119875119905= R

100381610038161003816100381611986411989410038161003816100381610038162


119890minus2120572119863

(7)


lowast


119871119877= 10 log(|119879|2R

1205780

120578seawater) (8)


119875119871 = R (120574) times20

ln (10)times 119863 + 10 log(|119879|2R

1205780

120578seawater)

(9)



0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010






0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107


Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109





minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










0

5

10

15

20

25

30

Refle

ctio

n lo

ss (d

B)

Frequency (Hz)

105

104

106

107

108

1091010






0

100

200

300

400

500

600

700

800

Tota

l pat

h lo

ss (d

B)

119863 = 05m119863 = 1m119863 = 2m

119863 = 3m119863 = 5

Frequency (Hz)105

104

106

107


Tota

l pat

h lo

ss (d

Bm

)

Frequency (Hz)

104

104

103

102

101

10

105

106

107

108

109





minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










minus180

minus160

minus140

minus120

minus100

minus80

minus60

minus40

minus20

0

Rece

ived

pow

er (d

Bm)

Scheme 1Scheme 2

Frequency (Hz)

105

106

107



Δ119891 =119891 sdot 119907rel119907

(10)


119907 =119888

radic120583119903120576119903

(11)






Scheme I(dB)

Scheme II(dB)


005 372 109 7101 402 154 6202 451 218 5205 558 345 381 686 488 292 873 690 215 1253 1090 1310 1688 1540 915 2023 1884 720 2306 2173 625 2554 2426 5






Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











Bit e

rror

rate

10minus1

10minus2

10minus3

10minus4

10minus5


4 6 8 10 12 14 165

10

15

20

25

30

35

Frequency (MHz)

Tota

l pat

h lo

ss (d

B)

Scheme IScheme II



6 Conclusion


Appendix



1205761015840


1 + (2120587119891120591sw)2 (A1)


12057610158401015840


1 + (2120587119891120591sw)2

+120590

21205871198911205760

(A2)

where 1205761015840

sw and 12057610158401015840


0= 885 times 10


120576sw0 (119879 119878sw) = 120576sw0 (119879 0) sdot 119886 (119879 119878sw) (A3)

where


119879


1198792


1198793

119886 (119879 119878sw) = 1 + 1613 times 10minus5


119878sw


1198782


1198783

sw

(A4)


120591sw (119879 119878sw) = 120591sw (119879 0) sdot 119887 (119879 119878sw) (A5)


where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










where

120591sw (119879 0) =1

2120587(111 times 10

minus10


119879


1198792


1198793

)

119887 (119879 119878sw) = 1 + 2282 times 10minus2


119878sw


1198782


1198783

sw

(A6)



References


















RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









an underwater wireless sensor network with realistic radio

Documents