6G 中的太赫茲無人機(jī)：機(jī)遇、挑戰(zhàn)和權(quán)衡

AERIALCOMMUNICATIONS

THz-EmpoweredUAVsin6G:Opportunities,Challenges,andTrade-offs

M.MahdiAzari,SourabhSolanki,SymeonChatzinotas,andMehdiBennis

TheauthorsprovidethepotentialopportunitiesandusecasesofTHz-empoweredUAVs,corre-spondingnoveldesignchallenges,andresultingtrade-offs.Furthermore,theyoverviewrecentadvancesinUAVdeploy-mentregulations,THzstandard-ization,andhealthaspectsrelatedtoTHzbands.

DigitalObjectIdentifier:

10.1109/MCOM.001.2100889

AbstrAct

Envisionedusecasesofunmannedaerialvehi-cles(UAVs)imposenewservicerequirementsintermsofdatarate,latency,andsensingaccuracy,tonameafew.MeetingsuchrequirementsenablehighlyreliableandharmonizedintegrationofUAVsinthe6Gecosystem.Towardthis,terahertz(THz)bandsareperceivedasaprospectivetechnologicalenablerforvariousimprovedfunctionalities,suchasultra-highthroughputcommunication,accuratelocalization,andenhancedsensingcapabilities.Inthisarticle,weprovidethepotentialopportu-nitiesandusecasesofTHz-empoweredUAVs,correspondingnoveldesignchallenges,andresult-ingtrade-offs.Furthermore,weoverviewrecentadvancesinUAVdeploymentregulations,THzstandardization,andhealthaspectsrelatedtoTHzbands.Finally,wetakeUAV-to-UAV(U2U)com-municationasacasestudytoprovidenumericalinsightsintotheimpactofvarioussystemdesignparametersandenvironmentfactors.

IntroductIon

Inherentattributesofunmannedaerialvehicles

(UAVs),suchastheirmobilityandflexibilityin

3Dpositioning,combinedwiththetechnologi-

caladvancementincost-effectivemanufacturing

ofUAVsmotivatethedelegationofmoretasks

toUAVsinthe6Gecosystem[1].Ontheother

hand,tosatisfytheproliferatingdemandsin6G,

terahertz(THz)bandstandsamongthecandi-

dateenablers[1,2].Thisisduetotheunderlying

potentialofTHzbandincharacterizinghigher

throughput,lowerlatency,accuratelocalization,

andprecisesensingandimagingcapabilities.

Recentadvancementsinthefieldofsemiconduc-

torindustriesenabledesignofmorecompactTHz

devices,solvingwhatwastraditionallyoneofthe

majorbarriersinTHzdeployment[3].Therefore,

towardtheprogressionof6Gnetworks,THz-em-

poweredUAVsmayofferseveralopportunities,

openingthedoortonewservicesandnovel

applications[1].Regardingthis,wepresentpro-

spectiveusecasesandopportunitiesenabledby

THz-empoweredUAVs.

DespitethehugepotentialofTHzband,thereisstillalongwaytogobeforeweseeitspracticalapplicationsinwirelesscommunications.However,thepersistenteffortsacrosstheresearchcommuni-tyoverthepastfewyearshavehelpedthisspecula-tivetechnologytobecomeincreasinglyattainable.TheroadmaptowardadvancingTHztechnology

furtherhasalsobeenactivelydiscussedinvarious

scenarios[4,5].THz-empoweredUAVsnotonly

facechallengescomingfromthenatureofsuch

frequencies;theyarealsoaffectedbytheintrica-

ciesofefficientUAVdeployment.Forexample,

molecularnoise,absorptionloss,anduncertain

mediumaremajorissueswithTHztransmissions,

whichbecomemoreaggravatinginoutdoorsce-

narioswithUAVs.Ontheotherhand,UAVs’flexi-

bilityofpositioningtheminlineofsight(LoS)and

adjustingtheirdistanceshavegreatpotentialin

usingTHzbandseffectively.Thisarticlehighlights

importantdesignchallengesofTHz-empowered

UAVsalongwithinducedtrade-offstoproviderele-

vantinsightsintothenewsystemdesign.

CertainbarriersinthedeploymentofTHz-em-poweredUAVsincluderegulatoryandhealthaspectspertainingtotheuseofTHzfrequen-cies,whichareoverlookedinmostacademicreports.Suchchallengesareelaborated,wheretheadvancementofregulations,standardization,andsafetyaspectsarereviewed.ThissectionisfollowedbyanotherwhereseveralsystemdesignparametersandenvironmentfactorsforqualitycommunicationbetweenUAVsarerecognizedandtheirimpactsinvestigated.AfewworkshaveanalyzedtheperformanceofTHzcommunica-tionsforUAV-groundlinks[6,7],buttheunderly-ingintricaciesofcombiningthetwotechnologieswerenotdiscussed.Toourbestknowledge,thisworkisthefirstonethatprovidesacomprehensivestudyonUAVsempoweredbyTHzfunctionalitieswherepotentialusecases,newchallenges,designtrade-offs,regulatoryandhealthaspects,aswellasnumericalinsightsarediscussed.

FundAmentAlFeAturesoFterAhertzcommunIcAtIons

THzpropagationexhibitscertaindistinctattributesthatarereviewedhere.

chAnnelAndProPAgAtIonchArActerIstIcsUnlikelowerfrequencies,wavelengthsofTHzarecomparabletothesizeofrain,dust,orsnow,whichmakesattenuationduetomolecularabsorptionmoresevere.Specifically,theatmo-sphericabsorptionduetoO2andH2OmoleculesissignificantintheTHzchannel.Sincethisabsorp-tionisdependentontheconcentrationandcom-positionofthemoleculesalongthepathofthewaves,thelossescanvarybasedonthemeteoro-

M.MahdiAzari,SourabhSolanki,andSymeonChatzinotasarewiththeUniversityofLuxembourg;MehdiBennisiswiththeUniversityofOulu,Finland

240163-6804/22/$25.00?2022IEEEIEEECommunicationsMagazine?May2022

IEEECommunicationsMagazine?May202225

logicalconditions,therebymakingTHzbandhigh-

lyfrequency-selective.THzwavesalsoencounter

spreadinglossduetoexpansionofelectromag-

netic(EM)wavesalongthemedium.Thepath

lossduetoabsorptionandspreadingaccountfor

theLoSpropagationoftheTHzwaves.Thepath

lossbecomesmoresignificantwithincreasein

thetransmissiondistance;however,themolecu-

larabsorptionlosscanbeminimizedbyselect-

ingasuitablebandwidth(e.g.,0.38–0.44THz)

wherethelossesarewellbelow10dB/km[4].

Inadditiontoaggravatingtheattenuation,molec-

ularabsorptionalsointroducesnon-whitenoise

dependingonthemixtureofmolecules.

Ontheotherhand,whenLoSpropagationisnotfeasibleduetoobstacles,THzwavesundergodiffusescattering,specularreflections,diffraction,andsoon,whichaccountfornon-LoS(NLoS)propagation.ThesecharacteristicsaredependentonthegeometryandmaterialoftheimpingingsurfaceaswellastheincidentangleofEMwave.Essentially,theTHzchannelmodelsshouldencap-sulatethefreespaceandabsorptionlosses,whicharedependentonfrequency,distance,altitudes,andrelativeaircomposition.Also,thepathlossremarkablydiffersunderLoSandNLoScondi-tions.Nonetheless,channelmodelingforTHzpropagationisyettobefullyunderstood.Severalmeasurementcampaignsandresearcheffortsareongoingforitscharacterization[5].

lArgeAntennAArrAysForPencIlbeAmFormIngTomitigatethehightransmissionlossatTHz,theadoptionoflargeantennaarraysfordirectionalbeamformingisinevitable.Infact,extremelysmallwavelengthscanfacilitatethesmall-sizedantennadesignthatcanbedeployedonalargescaletoformhugeantennaarraysforsharppencilbeams.Suchdirectionaltransmissioncancompensatefortheattenuationuptoacertainextent.Howev-er,itbringsaboutadditionalchallengessuchasmobilityandhandovermanagementandefficientbeamtrackingandalignment.Further,widebandbeamformingisalsoacriticalproblemprimarilycausedbythespatial-widebandeffectduetotheuseoflargeantennaarraysandfrequencyselec-tivityduetomultipathdelay[8].Widebandeffectsarealsoprevalentatmillimeter-wave(mmWave)band,buttheyaremoreprominentatTHzandrequireextensiveresearcheffortstoexploretheappropriatesolutions.

selectedusecAsesAndoPPortunItIesInthefollowing,wediscussseveralimportantapplicationsofTHz-empoweredUAVsasillustrat-edinFig.1.

SafeandReliableOperationofUAVs:LargeantennaarraysinsmallsizesatTHzcanenablecentimeter-levellocalizationaccuracyandsensingsolutionswithfiner-rangeDopplerandangularresolutions[9].Thus,THz-empoweredUAVspos-sessthecapabilityofaccuratelocalizationandsensing,whichcanfacilitatetheinstantaneousperceptionoftheenvironment.Suchfunction-alitiesleadtosafeandreliablenavigationofTHz-empoweredUAVs.NotethatsafeoperationofUAVsiscrucialforcomplyingwiththeregula-tionsinair-spaceandalsofortheirpracticalappli-cation.EmpoweringUAVswithTHzcanhelpinachievingthisobjective.Forinstance,leveraging

mmWave/Sub-6GHz

Control

AR

THzViewing

AdvancedUAVsSwarm

NLoSControl

/Navigation

MECServer

6G

THz-EmpoweredUAVs

High-SpeedInterconnections

AccurateLocalization

ReliableOperation

FIGURE1.RepresentativeusecasesofTHz-empoweredUAVs.

accuratesensingandlocalization,THz-empow-

eredUAVscanflexiblypositionthemselveswith

theintendedtransmitters/receiverstoimprove

reliabilityandsafety.Moreover,bydetectingthe

locationandpresenceofanyobstaclesorother

aerialnodes,theycanbesafelynavigatedwhile

seamlesslyavoidinganyconflictoraccident.

InteractiveAerialTelepresence:Itispossible

todeployUAVsandcontrolthemremotelyto

performunsafe,costly,ortime-sensitivetasksfor

humans.Thisisreferredtoasaerialtelepresence,

anditbecomesevenmorepowerfulwhenaug-

mentedreality(AR)isused,whichcanoffer3D

visualsandreal-timetele-interactionwiththeenvi-

ronment.Infact,suchhapticguidanceenhanc-

esUAVcapability,opensupnewapplications,

and,perhapsmostimportantly,providesaccess

toexpertsfromanywhereatanytime.Forsuch

applications,THzdeploymentisessential,par-

ticularlyforreal-timeinteractionswhereARdata

cannotbecompressed[2]andhighdataratesare

desired.Forhighlypreciseinteractivetasksand

immersiveexperience,UAVswithTHzsensorscan

provideaccurateinstantaneousperceptionofthe

environment,therebyofferingremotecognitive

capabilities.

AdvancedSwarmofUAVs:Toenhancethe

performanceofUAVnetworksandtacklethelim-

itsofanindividualUAV,UAVsmayperformina

swarm[10].Inthesescenarios,UAVsmayneed

toexchangelargeamountsofdata,particularly

giventhesignificantgrowthof6Gdatademand

andincreasingnumberofsensorsperUAVfor

integratedservicesin6G(sensing,localization,

mapping,etc.).Accordingly,UAVsneedtoboost

theirinterconnectionratecapacitybeyondthe

currenttechnology,compatiblewiththeupcom-

26IEEECommunicationsMagazine?May2022

Providingasufficientlyhigh-

speeddatalinkimproves

thetime-criticalremote

computationcapability,

enhancesthefreshnessof

data,andeventuallyenables

instantaneousenvironmental

cognition.

inggenerationsandservices.Anultra-high-throughputUAV-to-UAV(U2U)communicationlinkcanbeprovidedinTHzgiventhefavorableLoSdominantpropagationandthefactthatUAVscanestablishsufficientlyclosecommunicationrangetomitigatehighpathlossandmolecularabsorption.

Time-CriticalMEC-EmpoweredOperation:

Duetolimitedonboardcomputationcapaci-ty,UAVsmayrelyonmobileedgecomputing(MEC)servers,whichimposesignificantdelayinobtainingrequiredinformation.Providingasuffi-cientlyhigh-speeddatalinkimprovesthetime-crit-icalremotecomputationcapability,enhancesthefreshnessofdata,andeventuallyenablesinstanta-neousenvironmentalcognition.MEC-empoweredoperationthroughTHzlinksallowsreducingtheUAV’spayloadresultinginlowerpropulsionener-gyconsumptionandlongeroperationallifetime.Areal-timeremoteprocessinginturncreatesnewmeansofonlineNLoSUAVscontrolandnavigationthroughinstantaneousperceptionoftheenviron-ment.Inthisapplication,whentheenvironmentisunknown,threesteps—sensing,processing,andnavigating—canbeperformedinreal-timethankstoultra-high-throughputTHzlinksbetweenUAVsandthecomputing-and-controllingservers.

PollutionMonitoringandTracking:FrequencyscanningspectroscopyatTHzbandallowsairqual-itymonitoringanddetectionofsomechemicalssincevariousmaterialsatcertainfrequencieshavevibrationalabsorption.Thespecificabsorptioncharacteristicsofdifferentgaseousmediasignifi-cantlyboosttheTHz’ssensingcapability.THz-spec-troscopycoupledwithUAVs’flexibilitycanoffereffectivesolutionsforpollutionmonitoringandtracking.Forinstance,UAVsequippedwithTHzspectrometerscanflynearthesourceofpollution(e.g.,industrialchimneys)todetecttheconcentra-tionofvariouspollutants.Also,THz-empoweredUAVscanflyuptomountainpeakstodetectwatervaporconcentrations.SuchutilitiesofTHz-empow-eredUAVscanhelpincombatingairpollutionandassistinkeepingtrackofclimatechange.

RescueandSurveillance:THzcharacteristicscombinetheadvantagesofmicrowavesandvisiblelightforapracticalimplementationofanNLoSimagingsystem.Theyinvolvelargebandwidthsandsmallwavelengthsforhighspatialresolutions,andalsomoderatescatteringfeaturesforimagerecon-structionalgorithmsthatarecomputationallylessexpensivethanopticalsystems[5].AlthoughtherangeofTHzNLoSimagingmightstillbeshort,UAVs’flexibilityin3Dportioningcanaddressthislimitationbyhoveringintheproximityofatargetarea.UAVsequippedwithTHzwavescanviewNLoSobjectsduringrescueandsurveillance,expandingthebenefitsofTHzimagingcapability.

desIgnchAllengesAndtrAde-oFFs

THzcommunicationencountersseveralchalleng-esrelatedtothetechnologyitself.Forexample,thenoisepowernotonlyincreaseswithlargerbandwidth,butisalsoaccompaniedbymolecularabsorptionnoise.Themolecularabsorptionnoiseintensifiestheoverallnoiseinadditiontoitsdetri-mentaleffectonthereceivedsignalpower.Inthefollowing,welistspecificchallengesandpotentialtrade-offsinthedeploymentofTHz-empoweredUAVsfordifferentservices.

chAllenges

UAVWobblingandMotion:EffectiveuseofTHzfrequenciesrequireshighlydirectionalanten-nasatbothtransmitterandreceivertocompen-sateforthelargepropagationloss.However,UAVwobbling/fluctuationduetowindcanresultinbeammisalignment,whichdeterioratesthecommunicationquality.Also,duetouncontrolledtiltsandrotationsfromUAVmotion,maintainingaperfectbeamalignmentwouldbeintricate,thusresultinginseveralbeamhoppingandhandoverissues.Thisimpactgetsworseastheantennafoot-printshrinkswithlargerantennagain.

Evenifsuchphenomenadonotheavilyreducetheoverallrate,morefrequenthandoversresultinsignificantdelayandadverselyimpactthelinkreliability.Toguaranteeacertainlevelofreliabilityunderdelayconstraint,somehandoversmaybeskippedattheexpenseofratereduction.Further,sensingandlocalizationcapabilityinTHzcanassistUAVstooperatereliablybypreciselypositioningtheintendedtransmitters/receivers.Inaddition,intelligentreflectivesurface(IRS)-enabledTHzarchitecturecaneaseeffectivebeamalignmentbyofferingenhancedsensingandlocalization[11].

Power-HungryPayload:HighhardwarepowerconsumptioninTHz,essentiallycorrespondingtotheanalog-to-digitalconverters(ADCs),isoneofthemainchallengesforUAVswithlimitedpowerbudget.Althoughultra-widebandwidthsinTHzbandappeartobethemajormotivationtomovetowardhigherfrequencies,thepowerconsump-tionofADCsremarkablyincreaseswhensamplingratesurpasses100MHz,whichgrowsexponen-tiallywithresolution[12].Atlowerfrequencies,itiswidelyacceptedthatthepropulsionpowerconsumptionisdominantovertheelectricalpart,whichfacilitatesseveralenergy-efficientdesigns.InTHz,giventhehighnumberofantennaswiththecorrespondingRFchainsandADCsthetotalpayloadpowerconsumptionmaynotbenegligi-bleascomparedtothatofpropulsion.Therefore,itisimportanttoupdatethedesignguidelinesforTHz-empoweredUAVs.Furthermore,toplantheTHz-empoweredUAVtrajectory,longertravelingisneededforameaningfuldatatransferincon-trasttolowerfrequencies.

LimitedDesignSpace:OptimalheightofUAVsinlowfrequenciescanbeprimari-lyachievedbytransitionsfromNLoStoLoSformorefavorablepropagationconditions,whichcompensatefortheadverseimpactoflongerlinklengthsataltitudes[1].However,suchfindingsshouldberevisitedforTHzcommunicationsincethecommunicationqualitydrasticallydropswiththelinklength.Forinstance,althoughtheTHzbandcansupportterabit-per-secondlinksfordesigninganintegratedaccessandbackhaulforaUAVBS,thebenefitsareonlyreachablewith-inashortrangeofcommunication,whichlimitsthespaceforefficientandoptimalUAVplace-ment.Accordingly,morestrategicandopportu-nisticplanningof3Dplacementsisneeded.Thenewstrategicplanningcouldtakeadvantageofaccuratesensing,mapping,andlocalizationcapabilitiesofTHztoplanasmarterdeploymentandestablishamorefavorablecommunicationenvironment.Forinstance,high-resolutionsens-inginTHzcanbeexploitedtoprovidepredictive

IEEECommunicationsMagazine?May202227

controloftheservingusers’mobility.Although

sensinginTHzishighlyaccurate,therangeof

sensingisshort.Toovercometheshortrangeof

THzwave,multi-frequencyoperationcanbehelp-

ful.UAVsmayexploitmmWavesensingcapability

todetectmajorenvironmentalchangesinlonger

rangeandrelyonTHzforhigh-resolutionsensing

capabilitytotracksubtlechangesinshorterrange.

DenseDeploymentofUAVs:UAVshavetobeclosertoreceivers/transmittersinTHz;hence,ahigherdensityofUAVsmaybeneededforspe-cifictaskaccomplishmentsuchasmonitoringorsensing.However,eachUAVcanoffload/dissem-inatelargerdata;hence,higherthroughputcanbeachievedbyeachUAV,makingahighersum-ratecapacity.Furthermore,althoughmolecularabsorptionandhighpathlossforcethedensedeploymentofUAVs,itmaycreateconsiderableLoSinterference(gettingworseunderfrequentbeammisalignment)andhandovers.

Multi-FunctionalityDesign:Asdiscussedear-lier,THz-empoweredUAVssignificantlybenefitfromtheintegrationofvariousfunctionalitiessuchascommunication,sensing,localization,andcomputing.However,theco-designofsuchamulti-functionsystemisnotaneasytask.Inaddi-tiontothegeneralchallengessuchaswaveformdesignforintegratedsensingandcommunication[11],thedevelopmentofnovelmodelsandpow-erfulalgorithmswithlowcomplexitythatcanbeexecutedonUAVswithlimitedpowerandcom-putationcapabilityisamajorchallenge.Further-more,thealgorithmsshouldtakeintoaccountthesensitivityofseveralUAVapplicationstodelaycausedbytheintegrateddesign.

UncertainMediumCondition:Aircomposi-tionanditsdependencyonthemeteorologicalconditionmaketheTHzchannelhighlyuncertainandunreliable,particularlyinanuncontrolledout-doorscenario.Themolecularabsorptionishighlydependentonthepercentageofwatervaporintheairandthelevelofhumidity.Therefore,offlineoptimalnetworkdeploymentanddesignaspectscanonlybevalidundercertaincircumstanc-es,limitingthebenefits.Tosomeextent,onlineinstantaneoussensingandcommunicationcanalleviatesuchissue.

trAde-oFFs

SinceTHztransmittersrequirehighlydirectionaltransmission,theycompriselargeantennaarraystohavepencil-sizedbeams.UAVmotionandwob-blingcanleadtofrequentbeammisalignmentandthusrequirefrequenthandovers.Suchfrequenthandoverscancausedelayandhenceadverselyaffectthelatencyaswellasreliabilityperformance.Ononehand,higherantennagainleadstohigh-erdatarate,whileontheother,itmayunfavor-ablyaffectthelatencyandreliability.Moreover,largeantennaarraysalsoresultinhighenergycon-sumptionduetoalargenumberofADCsandRFchains.Further,longerflightsaredesirableforameaningfuldatatransferinTHz-empoweredUAVsatthecostofincreasedenergyconsumption.Tocounterbalancetheshortercommunicationrange,theUAVscanbedenselydeployed,butthismayleadtohighinterferenceandthusaffectthereli-ability.Asaconsequence,theunderlyingtrade-offsbetweenlatency,datarate,energyconsumption,andreliabilitycanbeestablished.

Consumption

UAVs

Wobbling

and

Beam

MisalignmentandHandover

Motion

Longer

UAV

Flight

Latency

PencilBeams

Multi-

functionality

Design

Directional

Power-

hungryPayload

Transmission

Large

Antenna

Arrays

Multi-

LongerUAVFlight

LargeRF

Chains

functionality

Design

andADCs

Large

Antenna

Arrays

THz-

Energy

DataRate

empowered

UAVs

ShorterRange

Large

Bandwidth

Sensingand

Commun.

Longer

UAVFlight

Multi-

Uncertain

functionalityDesign

Medium

Condition

Shorter

Range

Dense

DeploymentofUAVs

Sensing

and

Commun.

Reliability

HighLoSInterference

Uncertain

Medium

Condition

UAVs

Wobbling

and

Motion

FIGURE2.Challenges,trade-offs,andKPIsinTHz-empoweredUAVs.

Furthermore,integrationofvariousfunctional-

itiessuchascommunication,sensing,andlocal-

izationcanimprovethereliabilityanddatarate

byhavingabetterperceptionoftheenvironment

andbeamtracking.However,suchmulti-func-

tionalitydesigncanalsoleadtoanincreased

payloadenergyconsumption.Thus,trade-off

betweenenergyconsumption,datarate,andreli-

abilityexists.Inaddition,thisintegrateddesign

mayalsocontributesomewhattolatencyasvari-

ousoperationsareinvolved.Hence,reliabilitycan

beincreasedattheexpenseoflatency,resulting

inatrade-off.Alltheseinterlinkedchallengesand

trade-offsarealsoillustratedinFig.2.Considering

theuniquefeaturesofTHz-empoweredUAVs,

theirperformancecanbecharacterizedbyana-

lyzingvariousperformancemetricsviz.rate-en-

ergy,delay-rate,delay-reliabilitytrade-offs,andso

on,inadditiontothetraditionalindividualkey

performanceindicators(KPIs).

stAndArdIzAtIon,regulAtIons,AndheAlthIssues

Thissectionreviewsstandardizationandregulation

aspectsofUAVdeploymentandstandardization

andhealthissuesrelatedtoTHzdeployment.

uAVsdePloyment

StandardizationeffortsforUAVdeploymentstart-

edin2017whenthe3rdGenerationPartnership

Project(3GPP),initsRelease15,studiedLTE-sup-

portedUAVs.Underthisrelease,itpublished

atechnicalreport,TR36.777,whichidentified

theproblemsofuplink/downlinkinterference

andprovideduserequipment(UE)-andnet-

work-basedsolutionsforperformanceenhance-

ments.InRelease17,technicalspecificationTS

22.125identifiedUAVs’operationrequirements

28IEEECommunicationsMagazine?May2022

TheIEEEstandardization

bodyhasalsobeenactively

involvedintheregulationof

UAVcommunicationsandits

applications.Forinstance,

thedraftstandardIEEE

P1936.1establishedaframe-

worktosupportthedrone

applications,specifying

typicalapplicationclasses

andscenariosandrequired

executionenvironments.

viathe3GPPsystem.InthecontinuationofTS

22.125,TR22.829definednewservicerequire-

mentsandKPIsforvarious3GPPsupportedUAV

applications.Further,TR23.754addressedthe

mechanismstosupportunmannedaerialsystems

(UASs)connectivity,identification,andcoverage,

TR23.755identifiedtheapplicationlayersupport

forUASsandprovidedrelevantarchitecturalsolu-

tions,andTR33.854studiedthesecurityaspects

ofUASs.TR22.261fromReleases17and18dis-

cussesthe5GenhancementsforUAV.Specifical-

ly,itdescribestheUAVs’applicationbasedonthe

laidoutKPIsinTS22.125andalsoplanforthe

enhancedarchitecturetosupportUASs.

Ontheotherhand,theInternationalTelecom-municationUnion(ITU)hasalsoprovidedvariousRecommendationstofacilitateUAV-basedoper-ationsandapplications.Forexample,ITUTele-communicationsStandardization(ITU-T)F.749.10specifiedtherequirementsforcommunicationservicesofcivilianUAVs,whileITU-TY.4421(ex.Y.UAV.arch)determinedtherecommendationforfunctionalarchitectureofUAVcontrollersusingIMT-2020networks.Further,ITU-TX.677speci-fiedtheidentificationmechanismforUAVsusingobjectidentifiers,andITU-TY.4559identifiedthefunctionalarchitectureandotherrequirementsofbasestationinspectionservicesusingUAVs.Anoth-erRecommendation,ITU-TQ.3060,describestheapplicationofUAVsforfastdeploymenttelecom-municationnetworksincaseofnaturaldisaster.

TheIEEEstandardizationbodyhasalsobeenactivelyinvolvedintheregulationofUAVcom-municationsanditsapplications.Forinstance,thedraftstandardIEEEP1936.1establishedaframe-worktosupportthedroneapplications,specify-ingtypicalapplicationclassesandscenariosandrequiredexecutionenvironments.IEEEP1939.1definesalow-altitudestructureforefficientUAVtrafficmanagement.Furthermore,IEEEP1920.1definestheair-to-aircommunicationfortheself-organizedaerialadhocnetworkswhereaerialplatformscanformanetworktocommunicatewitheachotherwithoutrequiringthesupportingcellular/satelliteinfrastructure.Anotherproject,IEEEP1920.2,identifiestheprotocoltoexchangetheinformationbetweenthevehiclesforUASs.

OneoftheadditionalchallengesforUAVdeploymentisthelegislativeprocess.Untilafewyearsago,theoperationofsmallUAVswasnotstrictlyregulated,andtheywerelegallyclassifiedasremotecontrolledtoys.ButincreasingnumbersofUAVsandtheirpotentialapplicationsdemandstrictregulationinlow-altitudeairspacetoensuresafeoperationandavoidconflictwithmannedair-craft.WhilelargeUAVsoperatinginhigh-altitudeairspacecanbegovernedbythesameairtrafficcontrol(ATC)mechanismasforconventionalai