Table Of ContentModelling and characterisation of antennas and propagation for body-
centric wireless communication
Sani, Andrea
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Modelling and Characterisation of
Antennas and Propagation for
Body-Centric Wireless Communication
Andrea Sani
AthesissubmittedtothefacultyoftheUniversityofLondoninpartial
fulfillmentoftherequirementsforthedegreeof
Doctor of Philosophy
ElectronicEngineering,QueenMary,UniversityofLondon
LondonE14NS,UnitedKingdom
April 2010
2007(cid:176)c QueenMary,UniversityofLondon.Allrightsreserved.
To my family
Abstract
Body-CentricWirelessCommunication(BCWC)isacentralpointinthedevelopment
offourthgenerationmobilecommunications. Thecontinuousminiaturisationofsen-
sors,inadditiontotheadvancementinwearableelectronics,embeddedsoftware,di-
gitalsignalprocessingandbiomedicaltechnologies,haveledtoanewconceptofuser-
centric networks, where devices can be carried in the user’s pockets, attached to the
user’sbodyorevenimplanted.
Body-centricwirelessnetworkstaketheirplacewithinthepersonalareanetworks,
body area networks and body sensor networks which are all emerging technologies
that have a broad range of applications such as healthcare and personal entertain-
ment. The major differencebetween BCWC andconventional wirelesssystemsis the
radiochanneloverwhichthecommunicationtakesplace. Thehumanbodyisahostile
environment from radio propagation perspective and it is therefore important to un-
derstand and characterise the effect of the human body on the antenna elements, the
radio channel parameters and hence the system performance. This is presented and
highlightedinthethesisthroughacombinationofexperimentalandelectromagnetic
numerical investigations, with a particular emphasis to the numerical analysis based
onthefinite-differencetime-domaintechnique.
The presented research work encapsulates the characteristics of the narrowband
(2.4 GHz) and ultra wide-band (3-10 GHz) on-body radio channels with respect to
different digital phantoms, body postures, and antenna types hence highlighting the
effectofsubject-specificmodelling,staticanddynamicenvironmentsandantennaper-
formanceontheoverallbody-centricnetwork. Theinvestigationscoveredextendfur-
ther to include in-body communications where the radio channel for telemetry with
medical implants is also analysed by considering the effect of different digital phan-
toms on the radio channel characteristics. The study supports the significance of de-
veloping powerful and reliable numerical modelling to be used in conjunction with
i
measurement campaigns for a comprehensive understanding of the radio channel in
body-centric wireless communication. It also emphasises the importance of conside-
ringsubject-specificelectromagneticmodellingtoprovideareliablepredictionofthe
networkperformance.
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Contents
Abstract i
Contents iii
Acknowledgement vii
ListofPublications viii
ListofAbbreviations xii
ListofFigures xiv
ListofTables xxii
1 Introduction 1
1.1 Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 ResearchObjectiviesandChallenges . . . . . . . . . . . . . . . . . . . . . 3
1.3 OrganisationoftheThesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
References 6
2 CommunicationStandardsforBody-CentricWirelessNetworks 7
2.1 FrequencyAllocationforBodyandPersonalAreaNetworks . . . . . . . 7
2.2 WPANStandards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.1 Bluetooth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.2 ZigBee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.3 UWBTechnology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 TowardstheStandardizationofWBAN . . . . . . . . . . . . . . . . . . . 17
2.4 MICSstandard. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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References 22
3 Basics of Antenna and Propagation for Body-Centric Wireless Communica-
tions 24
3.1 TheRadioLink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.2 AntennasforBody-CentricWirelessCommunications . . . . . . . . . . . 26
3.2.1 UWBAntennasforOn-BodyApplications . . . . . . . . . . . . . 29
3.2.2 AntennasforMedicalImplants . . . . . . . . . . . . . . . . . . . . 33
3.3 RadioChannelCharacterisation . . . . . . . . . . . . . . . . . . . . . . . . 35
3.3.1 TransientandSpectralCharacterizationofMultipathChannels . 36
3.4 Radio Channel Characterisation for Body-Centric Wireless Communi-
cations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
References 48
4 ElectromagneticPropertiesandModellingoftheHumanBody 53
4.1 ModellingoftheHumanBody . . . . . . . . . . . . . . . . . . . . . . . . 53
4.1.1 ElectricalProprietiesofHumanBodyTissues . . . . . . . . . . . . 54
4.1.2 PhysicalPhantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.1.3 NumericalPhantoms . . . . . . . . . . . . . . . . . . . . . . . . . . 57
4.2 NumericalModellingforOn-BodyApplications. . . . . . . . . . . . . . . 59
4.3 FundamentalsoftheFDTDMethod . . . . . . . . . . . . . . . . . . . . . 63
4.3.1 DispersiveFDTD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References 71
5 NumericalModellingofWearableAntennasandRadioChannelat2.4GHz 74
5.1 Homogeneousvs. InhomogeneousPhantom . . . . . . . . . . . . . . . . 75
5.2 PathLossCharacterisationIncludingDifferentBodyPostures . . . . . . 78
5.3 Subject-SpecificStudyoftheOn-BodyRadioChannel . . . . . . . . . . . 83
5.3.1 DigitalPhantomsAdoptedintheSimulations . . . . . . . . . . . 83
5.3.2 PathLossCharacterisation . . . . . . . . . . . . . . . . . . . . . . 84
iv
5.4 ImplementationoftheEquivalencePrincipleinFDTD . . . . . . . . . . . 86
5.4.1 FieldEquivalencePrinciple: Huygen’sPrinciple . . . . . . . . . . 87
5.4.2 DescriptionoftheNumericalTechnique . . . . . . . . . . . . . . . 89
5.5 WearableAntennasfor2.4GHzISMBand . . . . . . . . . . . . . . . . . . 95
5.5.1 MicrostripPatchAntenna . . . . . . . . . . . . . . . . . . . . . . . 96
5.5.2 PlanarMonopoleAntenna. . . . . . . . . . . . . . . . . . . . . . . 97
5.5.3 PlanarInvertedLAntenna . . . . . . . . . . . . . . . . . . . . . . 97
5.6 EffectofDifferentAntennasonthePathLossAlongtheBodyTorso. . . 100
5.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
References 105
6 UltraWide-BandforBody-CentricWirelessCommunications 107
6.1 UWBWearableAntennas . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.1.1 PlanarInvertedConeAntenna . . . . . . . . . . . . . . . . . . . . 108
6.1.2 TaperedSlotAntenna . . . . . . . . . . . . . . . . . . . . . . . . . 114
6.2 RadioPropagationforUWBBody-CentricWirelessNetworksinIndoor
Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.2.1 PathLossCharacterisation . . . . . . . . . . . . . . . . . . . . . . 120
6.2.2 TransientCharacterisation . . . . . . . . . . . . . . . . . . . . . . . 121
6.3 EffectoftheBodyMovementsontheUWBOn-BodyRadioChannel . . 128
6.3.1 PathLossCharacterisation . . . . . . . . . . . . . . . . . . . . . . 131
6.3.2 TimeDelayCharacterisation . . . . . . . . . . . . . . . . . . . . . 134
6.4 NumericalStudyoftheUWBOn-BodyRadioChannel . . . . . . . . . . 137
6.4.1 PathLossCharacterisationIncludingDifferentBodyPostures . . 137
6.4.2 Subject-SpecificUWBOn-BodyRadioChannel . . . . . . . . . . . 139
6.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
References 143
7 WirelessTelemetryforMedicalImplants 145
7.1 RadiationCharacteristicsofWirelessSourcesConsideringDifferentDi-
gitalPhantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
7.1.1 ComputationalModels . . . . . . . . . . . . . . . . . . . . . . . . 147
v
7.1.2 RadiationCharacterization . . . . . . . . . . . . . . . . . . . . . . 149
7.2 CardiacImplantedLoopAntennas . . . . . . . . . . . . . . . . . . . . . . 154
7.3 LinkBudgetCalculationforMICSStandard . . . . . . . . . . . . . . . . . 155
7.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
References 167
8 ConclusionsandFutureWork 170
8.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
8.2 KeyContributions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
8.3 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
A ImplementationoftheParallelFDTD 176
B ImpedanceMatchingofthePresentedNarrowbandPlanarAntennas 180
C Post-ProcessingofMeasuredChannelData 182
D StatisticsDistributions 184
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Acknowledgement
My most sincere and deep gratitude goes to my supervisor Prof. Yang Hao, whose
support, guidance and encouragement have given me the strength and confidence
necessary for the development of the work. I would like also to thank Prof. Clive
Parini for his positive and fruitful comments, and Mr. John Dupuy for his assistance
intheexperimentalpartofthework.
AspecialmentiongoestomycolleaguesDr. AkramAlomainyandDr. YanZhao.
Their friendship, knowledge, and willingness to help have facilitated not only my
research,buteveryaspectofmyPhD.
Many thanks also to the Engineering and Physical Research Council (EPSRC) for
thefinancialsupport. IwouldlikealsotothankProf. PeterHall(UniversityofBirmin-
gham)forthefruitfuldiscussions. ManyappreciationstomycolleaguesMr. Christos
Argyropolus,Mr. AnestisKatsounaros,Mr. GeorgePalikaras,Dr. RobFoster,Dr. The-
mos Kallos, Mr. Max Munoz and Dr. Rostylav Dubrovka for having created such a
pleasantatmospherewithintheresearchgroup.
Aboveall,iwouldliketothankmyfamilyandmyfriends. Regardlessofphysical
distance,theirsupportandaffectionhavealwaysbeenwithme.
AndreaSani
London,April2010
vii
Description:discussed, as well as the fundamentals of radio propagation for body-centric wireless communications. 3.1 The Radio Link. The radio link can be represented as three distinct blocks, namely, the transmitting antenna (with transfer function HTx(ω)), the radio channel (with transfer function. HCh(ω)
