Vehicular
Networking
Bookdesign©2014CambridgeUniversityPress
Overview
▪ VehicularNetworking
▪ Part1:...incars▪ Overviewandusecases
▪ Architectures
▪ Bussystems
▪ ElectronicControlUnits
▪ Securityandsafety
▪ Part2:...ofcars▪ Overviewandusecases
▪ Architectures
▪ CommunicaIonsystems
▪ ApplicaIons
▪ Securityandsafety
Vehicular Networking 2
IllustraIon©2010ChristophSommer
Aboutthisslidedeck
▪ Theseslidesaredesignedtoaccompanyalecturebasedonthetextbook“VehicularNetworking”byChristophSommerandFalkoDressler,publishedinDecember2014byCambridgeUniversityPress.
▪ Exceptwhereotherwisenoted(e.g.,logosandcitedworks)thisslidedeckisCopyright©2009-2015ChristophSommer,butmadeavailabletoyouunderaCrea%veCommonsA-ribu%on-ShareAlike4.0Interna%onalLicense.
▪ Inbrief,thismeansyoucanshareandadapttheslidesaslongasyoufollowthetermssetoutinthislicense[1].IfyousplitthisslidedeckintomulIpleparts,makesuretoincludeappropriateaZribuIonineachpart.
▪ ThisslidedeckwouldnothavebeenpossiblewithoutthecontribuIonsofFalkoDressler,DavidEckhoff,ReinhardGerman,andKai-SteffenJensHielscher.
▪ Pleaseleavethisslideintact,butindicatemodificaIonsbelow.▪ Version2015-02
▪ Improvedversionforreleaseonbookwebsite(ChristophSommer)
▪ Updatedversionsoftheoriginalslidedeckareavailableonline[2].
Vehicular Networking 3
[1]hZp://creaIvecommons.org/licenses/by-sa/4.0/
[2]hZp://book.car2x.org/
CourseMaterial
Vehicular Networking 4
Bookdesign©2014CambridgeUniversityPress
Title VehicularNetworking
Authors ChristophSommerandFalkoDressler
Publisher CambridgeUniversityPress
Date December2014
Format Hardback(alsoavailableaseBook)
ISBN-10 1107046718
ISBN-13 9781107046719
Website hZp://book.car2x.org
AShortIntroducIon
…toVehicularNetworking
Vehicular Networking 5
IntroducIon–Electronicsincars
Vehicular Networking 6
DataSource:U.Weinmann:AnforderungenundChancenautomobilgerechterSokwareentwicklung,3.EUROFORUM-Fachkonferenz,StuZgart,Juli2002
1970s
• ElectronicFuelInjecIon• CentralizedWarningLights
• CruiseControl• CentralLocking• ...
1980s
• Electronictransmissioncontrol
• Electronicclimatecontrol
• ASC(AnISlipControl)• ABS(AnIlockBrakingSystem)
• Phone• Seatheatercontrol• AutomaIcallydimmingrearviewmirror
• ...
1990s
• navigaIonsystem
• CDchanger• ACC(AcIveCruiseControl)• Airbags• DSC(DynamicStabilityControl)
• AdapIveTransmissionControl
• RollstabilizaIon• Xenonlight• BMWAssist
• RDS/TMC
• VoiceRecogniIon• Emergencycall
• ...
2000s
• ACCStop&Go• BFD• ALC• KSG• 42voltsystem
• InternetPortal• GPRS,UMTS
• TelemaIcs
• OnlineServices• Bluetooth• CarOffice
• LocalHazardWarning
• IntegratedSafetySystem
• Steer/Brake-By-Wire
• I-Drive• Lanekeepingsupport• PersonalizaIon• SWupdate
• ForceFeedbackPedal• ...
ElectronicsneedcommunicaIon
Vehicular Networking 7
DataSource:U.Weinmann:AnforderungenundChancenautomobilgerechterSokwareentwicklung,3.EUROFORUM-Fachkonferenz,StuZgart,Juli2002
Complexity
EmbeddedControlUnits(n)
Numberofsignals(k*n) NumberofpotenIalcommunicaIonpartners(n*(n-1))
CoordinaIonoverhead(q*n*(n-1))
Componentfailurerate
Vehicular Networking 8
DataSource:ADACVehicleBreakdownStaIsIcs2005-2008
35.0%
18.8%
14.6%
7.7%
6.0%
6.2%
5.6%
4.1%
2.0%
38.6%
14.0%
13.6%
7.9%
6.6%
6.7%
6.0%
4.1%
2.2%
39.7%
13.6%
12.7%
7.8%
6.8%
7.1%
5.8%
4.6%
1.9%
40.0%
16.0%
10.0%
8.0%
8.0%
7.0%
5.0%
4.0%
2.0%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
Electronics
Misce
llaneous
IgniIo
n
Engin
e
FuelinjecI
on
Tiresandw
heels
HeaIng,co
oling,A/C
Clutch
,gearsh
ik
Exhaustsys
tem
2005 2006 2007 2008
Bussystems
▪ UnIltheendofthe80s▪ Cars‘controlunitsareisolated,non-networked▪ dedicatedwiresconnectsensorsandactors
▪ StarIngwiththe90s▪ digitalBussystems
▪ CAN-Bus▪ Today
▪ Risingdemandsonbussystems
▪ networkedfuncIonalityrequiresmorethanonecontrolunit▪ Turnsignal:>8disInctcontrolunits
▪ RealImeconstraints
▪ MulImedia
Vehicular Networking 9
Bussystems
▪ Complexityiseverincreasing
▪ From5ECUsina1997AudiA6
▪ Toover50ECUsina2007AudiA4▪ Currentmiddleandupperclassvehicles
carry80..100networkedElectronicControlUnits(ECUs)
▪ TradiIonally:onetask⬄oneECU
▪ Newtrends:▪ distribuIonoffuncIonsacrossECUs▪ integraIonofmulIplefuncIonsononeECU
Vehicular Networking 10
MulIplebussystems
Gateway
CAN1
RearView ClimateA/C
MulIFuncIonDisplay
CAN2
Engine Airbag
Gearbox LIN
Seatoccupancy
Flexray
Radar Video
ESP
MOST
FrontDisplay DVDPlayer
RadioTuner MP3System
Vehicular Networking 11
Electronicstoday
▪ Upto100ECUs▪ Upto30%ofvaluecreaIon▪ Upto90%ofInnovaIons▪ Upto3kmofwiringforpoweranddata
▪ Upto3800interfacepoints
Vehicular Networking 12
Electronicstomorrow
Vehicular Networking 13
IllustraIon©2010ChristophSommer
▪ Datawillleaveconfinesofsinglecar:inter-vehiclecommunicaIon
VisionaryApplicaIons
▪ Laneassistant▪ SimpleroadsidebeaconssupportlanedetecIon
▪ Lateralcollisionavoidance▪ Moreadvancedbeaconsoncarsandmotorcycleshelpmaintainminimum
separaIon
▪ AccidentreporIng▪ BrokendowncarscanautomaIcallysendsimplereporttocentralserver
▪ IntersecIonassistance▪ PairsofcarsautomaIcallycoordinatecomplexmaneuversatintersecIons
▪ CooperaIvedriving▪ ThefutureevoluIonofautonomousdriving:vehiclesacIvelysupporteach
other’srouteplanning,navigaIng,driving
Vehicular Networking 14
VisionaryApplicaIons
▪ ...andmuch(much)more:Emergency Brake Light Warning, Accident Warning, Emergency Flashlights, Traffic Jam Warning, Weather Warning, Emergency Vehicle, Slow Vehicle, Moving and Static Road Works, Obstacle Warning, Intersection Maneuvering Assistance, Intersection Traffic Lights, Lane Change, Maneuvering Assistance, Longitudinal Maneuvering Assistance, Floating Car Data Collection, Free-Flow Tolling, Breakdown Call, Remote Diagnostics, Theft Detection, Emergency Call, Just-In-Time Repair Notification, Roadside Traffic Camera pull, In-vehicle signing pull, Regional Information pull, Car-specific Software Application Download pull, Electronic Payment pull, Logistic for goods being loaded and unloaded, Traffic Information Service pull, Traffic Information Service push, Electronic Payment push, Roadside Traffic Camera push, In-vehicle signing push, Car specific Software Application Download push, Telemetric Onboard/Off-board Diagnostics, Remote Vehicle Status Control, Fleet Management, Server based navigation, Remote lock-down, Remote entry, Mobile Office, Videophone, Personal Data Synchronization at home, General Map Downloads and Updates, Instant Messaging, General internet services, Internet Audio, continuous feed, Web Browsing, Movie rental, Remote Home Activation/Deactivation pull, Remote Home Control pull, Remote Home Activation/Deactivation push, Remote Home Control push, Voice Chat, Games, Electronic Toll Collection, Parking Unit Fee Payment (drive through payment), Goods and services discovery and payment, Guided Tour, Interactive Lights Dimming, Emergency Traffic Light Pre-emption, Traffic Light Assistant, …
Vehicular Networking 15
Source:C2CCC,AkIv-AS/VM
ChallengesofcommunicaIon
▪ Basicchallenges▪ Timeliness
▪ Throughput▪ CommunicaIoninvehicles:stresses...
▪ Robustness▪ Cost
▪ CommunicaIonacrossvehicles:alsoneeds...▪ Interoperability▪ Reachability▪ Security▪ Privacy
Vehicular Networking 16
Part2Car-to-XNetworking
Car-to-X(C2X)communicaIonpaZerns
▪ Vehicle-to-X
(V2X),
▪ Inter-VehicleCommunicaIon
(IVC),
▪ Vehicular
ad-hocnetwork
(VANET),
▪ …
Vehicular Networking 18
IllustraIon:ETSI
…toinfrastructure
…tocar
…tohome
UseCases
Vehicular Networking 19
IllustraIon:CVIS
Illustration: CVIS
TaxonomyofUseCases
Vehicular Networking 20
Vehicle-to-X
Non-Safety
Comfort
ContextualInformaIon Entertainment
TrafficInformaIonSystems
OpImalSpeedAdvisory
CongesIon,Accident
InformaIon
Safety
SituaIonAwareness
AdapIveCruiseControl
BlindSpotWarning
WarningMessages
TrafficLightViolaIon
ElectronicBrakeLight
TaxonomyofUseCases
Vehicular Networking 21
Vehicle-to-X
Non-Safety
Comfort
ContextualInformaIon Entertainment
TrafficInformaIonSystems
OpImalSpeedAdvisory
CongesIon,Accident
InformaIon
Safety
SituaIonAwareness
AdapIveCruiseControl
BlindSpotWarning
WarningMessages
TrafficLightViolaIon
ElectronicBrakeLight
Vehicle-to-X
Non-Safety
Manymessages
Highdatarate
Lowlatencydemands
Lowreliabilitydemands
Safety
Fewmessages
Smallpacketsize
Highlatencydemands
Highreliabilitydemands
TaxonomyofUseCases
Vehicular Networking 22
Diversityofusecases
Applica@on Distance Time Recipient
Hazardwarning 250m 10s All
LocaIonbasedservice 1..5km Weeks Subscribers
Citywidealarm 20km Hours All
TravelImeinformaIon 5km Minutes All
Filesharing 250mMinutes(Index)Days(Content)
Subscribers(Index)Peers(Content)
InteracIveServices 1..5km Minutes Subscribers
Vehicular Networking 23
[1]Bai,F.andKrishnamachari,B.,"ExploiIngtheWisdomoftheCrowd:Localized,DistributedInformaIon-CentricVANETs,"IEEECommunicaIonsMagazine,vol.48(5),pp.138-146,May2010
Diversityofrequirements
Applica@on Latency Reliability #Vehicles Area Persistence
InformaIonQuery � � ��� ���
HazardWarning
ACC,el.BrakeLight
CooperaIveAwareness
IntersecIonAssistance
Platooning
Vehicular Networking 24
[1]T.L.Willke,P.Tientrakool,andN.F.Maxemchuk,"ASurveyofInter-VehicleCommunicaIonProtocolsandTheirApplicaIons,"IEEECommunicaIonsSurveysandTutorials,vol.11(2),pp.3-20,2009
Diversityofrequirements
Applica@on Latency Reliability #Vehicles Area Persistence
InformaIonQuery � � ��� ���
HazardWarning ��� �� �� ���
ACC,el.BrakeLight
��� �� � �
CooperaIveAwareness
IntersecIonAssistance
Platooning
Vehicular Networking 25
[1]T.L.Willke,P.Tientrakool,andN.F.Maxemchuk,"ASurveyofInter-VehicleCommunicaIonProtocolsandTheirApplicaIons,"IEEECommunicaIonsSurveysandTutorials,vol.11(2),pp.3-20,2009
Diversityofrequirements
Applica@on Latency Reliability #Vehicles Area Persistence
InformaIonQuery � � ��� ���
HazardWarning ��� �� �� ���
ACC,el.BrakeLight
��� �� � �
CooperaIveAwareness
IntersecIonAssistance
Platooning
Vehicular Networking 26
[1]T.L.Willke,P.Tientrakool,andN.F.Maxemchuk,"ASurveyofInter-VehicleCommunicaIonProtocolsandTheirApplicaIons,"IEEECommunicaIonsSurveysandTutorials,vol.11(2),pp.3-20,2009
Diversityofrequirements
Applica@on Latency Reliability #Vehicles Area Persistence
InformaIonQuery � � ��� ���
HazardWarning ��� �� �� ���
ACC,el.BrakeLight
��� �� � �
CooperaIveAwareness
�� ��� � � �
IntersecIonAssistance
�� ��� �� �� �
Platooning ��� ��� �� � �
Vehicular Networking 27
[1]T.L.Willke,P.Tientrakool,andN.F.Maxemchuk,"ASurveyofInter-VehicleCommunicaIonProtocolsandTheirApplicaIons,"IEEECommunicaIonsSurveysandTutorials,vol.11(2),pp.3-20,2009
MoIvaIon
▪ 1970s:boldideas▪ Veryvisionary,infrastructure-lesssoluIons
▪ Unsupportedbycurrenttechnology
▪ Earlyinterestofgovernmentandindustry▪ workingprototypesin:JapanCACS(1973–1979),
EuropePrometheus(1986–1995),U.S.PATH(1986–1992)▪ Nocommercialsuccess
▪ 1980s:paradigmshik▪ FromcompletehighwayautomaIon�driver-advisoryonly▪ Infrastructure-less�infrastructure-assisted▪ chicken-and-eggtypeofstandoff
▪ Newtechnologyre-ignitesinterest▪ latest-generaIoncellularcommunicaIon�early“Car-to-X”systems
▪ e.g.,OnStar(1995),BMWAssist(1999),FleetBoard(2000),andTomTomHDTraffic(2007).▪ SharpincreaseincompuIngpower
▪ Supportsfully-distributed,highlyreacIveadhocsystems
Vehicular Networking 28
[1]W.Zimdahl,“GuidelinesandsomedevelopmentsforanewmodulardriverinformaIonsystem,”in34thIEEEVehicularTechnologyConference(VTC1984),vol.34.,PiZsburgh,PA:IEEE,May1984,pp.178–182.
Renewedinterestofgovernmentandindustry
▪ NumerousfieldoperaIonaltests▪ simTD(€69M),AkIv(€60M),SmartHighway(€57M),
DriveC2X(€19M),TeleFOT(€15M),SafeTrip(€10M),…
▪ DedicatedspectruminU.S.,Europe,Asia
Vehicular Networking 29
IllustraIon:FOT-NETWiki
?
MoIvaIon
▪ TradiIonalNetwork▪ ConnecIon:wired▪ Nodes:non-moving
▪ ConfiguraIon:staIc
▪ MobileAdHocNetwork(MANET)▪ ConnecIon:wireless
▪ Nodes:mobile
▪ ConfiguraIon:dynamic
▪ (Infrastructure:opIonal)
▪ VehicularAdHocNetwork(VANET)▪ Not:“MANETonwheels”
▪ Differenttopologydynamics,communicaIonpaZerns,infrastructure,...
Vehicular Networking 30
[1]M.ScoZCorsonandJosephMacker,"MobileAdhocNetworking(MANET):RouIngProtocolPerformanceIssuesandEvaluaIonConsideraIons,“RFC2501,January1999
IMPORTANTINFORMATION
▪ ThemissedClasswillbegiveninEarlyNovember(Date
TBD)
▪ PleaseSignupwithyoure-mailonthePaper
▪ YouwillbesubscribedtoaGoogleGroup
Vehicular Networking 31
Freeway�Urban
Vehicular Networking 32
Freeway�Urban
▪ 1Dmobility
▪ BimodalconnecIvity
▪ StableconnecIon(vehiclesonsamelane)
▪ AND▪ unstableconnecIon(vehiclesonoppositelane)
▪ Highspeed▪ …
Vehicular Networking 33
• 2Dmobility
• BipolarconnecIvity– Manyneighbors
(whenstanding)
– OR– Fewneighbors(whendriving)
• Obstacles• …
Levelsofinfrastructuresupport
▪ PureadhoccommunicaIon
▪ StaIonarySupportUnits(SSU)▪ Radio-equippedautonomouscomputer
▪ InexhausIblestorage,energysupply▪ KnownposiIon,highreliability
▪ RoadsideUnits(RSU)▪ SSUplus…▪ EthernetNIC,UMTSradio,...
▪ ConnectedtootherRSUs
▪ TrafficInformaIonCenter(TIC)▪ CentralserverconnectedtoRSUs
Vehicular Networking 34
Infrastructure�NoInfrastructureHERE!!!!!!!!!
▪ CentralcoordinaIon▪ Resourcemanagement
▪ Security▪ Highlatency▪ Highloadoncorenetwork
▪ …
Vehicular Networking 35
• Selforganizingsystem
– Channelaccess– AuthenIcaIon
• Lowlatency• Lowdatarate• …
Source: AKTIV CoCar
Convergencetowardsheterogeneousapproaches
▪ SamesystemneedstoworkinmulIpleenvironments
▪ Vehiclestartstodriveincitywithinfrastructuresupport▪ ConInuesdrivingonfreeway(sIllwithinfrastructuresupport)▪ Losesinfrastructuresupportwhenturningontolocalhighway▪ Finishesdrivingincitywithoutinfrastructuresupport
Vehicular Networking 36
AdopIon
▪ Prognosis(ofproviders!)inGermanyandtheU.S.
▪ 14..15yearsto100%marketpenetraIon
▪ ComparetonavigaIonsystemsinGermancars
▪ 13yearsto14%marketpenetraIon
▪ And:itisveryeasytoretrofitasatnav!
Vehicular Networking 37
[1]Bai,F.andKrishnamachari,B.,"ExploiIngtheWisdomoftheCrowd:Localized,DistributedInformaIon-CentricVANETs,"IEEECommunicaIonsMagazine,vol.48(5),pp.138-146,May2010
[2]UlrichDietz(ed.),“CoCarFeasibilityStudy:Technology,BusinessandDisseminaIon,”CoCarConsorIum,PublicReport,May2009.
[3]VerbandderAutomobilindustriee.V.,“Auto2007–JahresberichtdesVerbandsderAutomobilindustrie(VDA),“,July2007.
ChallengesofC2XcommunicaIon
Vehicular Networking 38
• HighlyvaryingchannelcondiIons• HighcongesIon,contenIon,interference• Tightlylimitedchannelcapacity
CommunicaIon
• UnidirecIonalLinks• MulI-Radio/MulI-Network
• HeterogeneousequipmentNetworking
• Highlydynamictopology
• But:predictablemobility
• HeterogeneousenvironmentMobility
• No(ornoreliable)uplinktocentralinfrastructure• Ensuringprivacy• Heterogeneoususerbase
Security
Technology
Vehicular Networking 39
CommunicaIonparadigmsandmedia
WirelessCommunicaIonTechnologies
Infrastructure-based
Broadcast
FMRadio,DAB/DVB,
…
Cellular
GSM
2GCellular
UMTS3G
Cellular
LTE/WiMAX
4GCell.
Infrastructureless
ShortRange
Millimeter,Infrared,Visible
802.15.1Bluetooth
802.15.4ZigBee
MediumRange
802.11Wi-Fi
DSRC/WAVE
Vehicular Networking 40
[1]Dar,K.etal.,"WirelessCommunicaIonTechnologiesforITSApplicaIons,"IEEECommunicaIonsMagazine,vol.48(5),pp.156-162,May2010
BroadcastMedia
▪ TrafficMessageChannel(TMC)
▪ CentralmanagementoftrafficinformaIon
▪ Datasourcesarevaried▪ Federal/local/citypolice,roadoperator,radio,…
▪ TransmissioninRDSchannelofFMradio
▪ BPSKmodulatedsignalat57KHz,datarate1.2kBit/s
▪ RDSgroupidenIfier8A(TMC),approx.10bulleInsperminute
Vehicular Networking 41
[1]ISO62106,„SpecificaIonoftheradiodatasystem(RDS)forVHF/FMsoundbroadcasInginthefrequencyrangefrom87,5to108,0MHz“
f (in KHz) l+r l-r l-r
0 15 19 23 38 53 57
BroadcastMedia
▪ TrafficMessageChannel(TMC)▪ Contents(ALERT-Ccoded):
▪ Validityperiod▪ Re-rouIngrequired?▪ North-eastorsouth-west?▪ SpaIalextent▪ Codeineventtable
▪ InternaIonal▪ CodeinlocaIontable
▪ Country/regionspecific▪ Mustbeinstalledinend
device
▪ No(real)securitymeasures
Vehicular Networking 42
[1]ISO14819-1,„TrafficandTravellerInformaIon(TTI)-TTImessagesviatrafficmessagecoding-Part1:CodingprotocolforRadioDataSystem(RDS-TMC)usingALERT-C“
[2]ISO14819-2,„TrafficandTravellerInformaIon(TTI)-TTImessagesviatrafficmessagecoding-Part2:EventandinformaIoncodesforRadioData
System-TrafficMessageChannel(RDS-TMC)“
101 Standingtraffic(generic)
102 1kmofstandingtraffic
103 2kmofstandingtraffic
394 Brokendowntruck
1478 Terroristincident
1 Deutschland
264 Bayern
12579 A8AnschlussstelleIrschenberg
BroadcastMedia
▪ TrafficMessageChannel(TMC)▪ Regionalvalueaddedservices
▪ NavteqTrafficRDS(U.S.),trafficmaster(UK),V-Trafic(France)
▪ Ex:TMCpro▪ PrivateserviceofNavteqServicesGmbH
▪ Financedbyper-decoderlicensefee▪ DatacollecIonandprocessing
▪ FullyautomaIc
▪ Deploymentof4000+sensorsonoverpasses
▪ UseoffloaIngcardata▪ DownlinkfromtrafficinformaIoncenters
▪ EventpredicIon▪ Expertsystems,neuronalnetworks
▪ Earlywarningsofpredictedevents▪ Restrictedtomajorroads
Vehicular Networking 43
BroadcastMedia
▪ TransportProtocolExpertsGroup(TPEG)▪ PlannedsuccessorofRDS-TMC/Alert-C
▪ PublishedApril2000▪ Principles:
▪ Extensibility▪ Mediaindependence
▪ Goals:▪ Builtfor“DigitalAudioBroadcast”(DAB)▪ UnidirecIonal,byteorientedstream
▪ Modularconcept
▪ Hierarchicalapproach▪ Integratedsecurity
Vehicular Networking 44
[1]ISO18234-x,„TrafficandTravelInformaIon(TTI)—TTIviaTransportProtocolExpertsGroup(TPEG)data-streams“
BroadcastMedia
▪ TransportProtocolExpertsGroup(TPEG)▪ InformaIontypesdefinedby“TPEGApplicaIons”
▪ RTM-RoadTrafficMessage
▪ PTI-PublicTransportInformaIon▪ PKI-ParkingInformaIon
▪ CTT-CongesIonandTravel-Time
▪ TEC-TrafficEventCompact
▪ WEA-WeatherinformaIonfortravelers
▪ Modularconcept:
Vehicular Networking 45
TransportProtocolExpertsGroup(TPEG)
Vehicular Networking 46
[1]ISO24530-x,„TrafficandTravelInformaIon(TTI)—TTIviaTransportProtocolExpertsGroup(TPEG)ExtensibleMarkupLanguage(XML)“
▪ tpegML:XMLvariantofregular(binary)TPEG
TransportProtocolExpertsGroup(TPEG)
▪ Hybridapproachtogeo-referencing:oneormoreof
▪ WGS84basedcoordinates
▪ ILOC(IntersecIonLocaIon)▪ Normalized,shortenedtextualrepresentaIonof
streetnamesintersecIngatdesiredpoint
▪ Humanreadableplaintext
▪ CodeinhierarchicallocaIontable
Vehicular Networking 47
CommunicaIonparadigmsandmedia
WirelessCommunicaIonTechnologies
Infrastructure-based
Broadcast
FMRadio,DAB/DVB,
…
Cellular
GSM
2GCellular
UMTS3G
Cellular
LTE/WiMAX
4GCell.
Infrastructureless
ShortRange
Millimeter,Infrared,Visible
802.15.1Bluetooth
802.15.4ZigBee
MediumRange
802.11Wi-Fi
DSRC/WAVE
Vehicular Networking 48
[1]Dar,K.etal.,"WirelessCommunicaIonTechnologiesforITSApplicaIons,"IEEECommunicaIonsMagazine,vol.48(5),pp.156-162,May2010
CellularNetworks
▪ Concept▪ Divideworldintocells,eachservedbybasestaIon▪ Allows,e.g.,frequencyreuseinFDMA
f0
f1
f2
f0
f2
f1
f2
f0
f1
f0
f1
f2
f0
f1
f2
f0
f1
f2
f0
f2
f0
f2
f0
f2
f0
f1
f2
f0
Vehicular Networking 49
Concept
▪ Stricthierarchyofnetworkcomponents
UE
Core Network
RNC
Cell
NodeB
Cell Cell Cell Cell
NodeB
Cell
RNC
Cell
NodeB
Cell Cell Cell Cell
NodeB
Cell
Vehicular Networking 50
CellularNetworks
▪ CanUMTSsupportCar-to-XcommunicaIon?▪ Ex:UTRAFDDRelease99(W-CDMA)
▪ SpeedofvehiclesnotalimiIngfactor▪ FieldoperaIonaltestsat290km/hshowsignaldropsonlyakersuddenbraking(�handoverpredicIonfailures)
▪ OpenquesIons▪ Delay▪ Capacity
▪ ChannelsinUMTS▪ Sharedchannels
▪ E.g.RandomAccessChannel(RACH),uplinkandForwardAccessChannel(FACH),downlink
▪ Dedicatedchannels▪ E.g.DedicatedTransportChannel(DCH),up-/downlink
Vehicular Networking 51
CellularNetworks
▪ FACH▪ TimeslotsmanagedbybasestaIon
▪ Delayontheorderof10msper40ByteandUE
▪ Capacityseverelylimited(innon-mulIcastnetworks)
▪ NeedtoknowcurrentcellofUE▪ RACH
▪ SloZedALOHA–randomaccessbyUEs▪ PowerrampingwithAcquisiIonIndicaIon
▪ Delayapprox.50msper60ByteandUE
▪ MassiveinterferencewithotherUEs
Vehicular Networking 52
CellularNetworks
▪ DCH▪ Delay:approx.250ms/2s/10sforchannelestablishment
▪ Dependsonhowfine-grainedUEposiIonisknown▪ MaintainingaDCHisexpensive
▪ Closed-LoopPowerControl(nointerferenceofotherUEs)▪ Handoverbetweencells▪ ...
▪ Upperlimitofapprox.100UEs
Vehicular Networking 53
CellularNetworks
▪ So:canUMTSsupportCar-to-XcommunicaIon?
▪ AtlowmarketpenetraIon:yes
▪ Eventually:▪ Needtoinvestinmuchsmallercells(e.g.,alongfreeways)
▪ NeedtoimplementmulIcastfuncIonality(MBMS)
▪ MainusecaseforUMTS:centralizedservices
▪ Ex.:GoogleMapsTraffic
▪ CollectinformaIonfromUMTSdevices
▪ Storageofdataoncentralserver▪ DisseminaIonviaInternet(�idealforcellularnetworks)
Vehicular Networking 54
IEEE802.11p
▪ IEEE802.11{a,b,g,n}forCar-to-XcommunicaIon?▪ Can’tbeininfrastructuremodeandadhocmodeatthesameIme
▪ SwitchingImeconsuming
▪ AssociaIonImeconsuming
▪ Nointegralwithin-networksecurity▪ (Massively)sharedspectrum(�ISM)
▪ NointegralQoS▪ MulI-patheffectsreducerangeandspeed
Vehicular Networking 55
IEEE802.11p
▪ IEEE802.11p▪ PHYlayermostlyidenIcaltoIEEE802.11a
▪ VariantwithOFDMand16QAM
▪ Higherdemandsontolerances
▪ ReducIonofintersymbolinterferencebecauseofmulI-patheffects
▪ DoubleImingparameters
▪ Channelbandwidthdownto10MHz(from20MHz)
▪ Throughputdownto3...27Mbit/s(from6...54Mbit/s)
▪ Rangeupto1000m,speedupto200km/h
▪ MAClayerofIEEE802.11aplusextensions▪ RandomMACAddress
▪ QoS(EDCApriorityaccess,cf.IEEE802.11e,...)▪ MulI-FrequencyandMulI-RadiocapabiliIes
▪ NewAdHocmode
▪ ...
Vehicular Networking 56
IEEE802.11p
▪ ClassicIEEE802.11BasicServiceSet(BSS)▪ Dividesnetworksintologicalunits
▪ Nodesbelongto(exactlyone)BSS▪ PacketscontainBSSID▪ Nodesignorepacketsfrom“foreign”BSSs
▪ ExcepIon:Wildcard-BSSID(-1)forprobes
▪ Adhocnetworksemulateinfrastructuremode
▪ JoiningaBSS▪ AccessPointsendsbeacon▪ AuthenIcaIondialogue▪ AssociaIondialogue▪ NodehasjoinedBSS
BSS SSID “A”
BSS SSID “B”
BSS SSID “C”
Vehicular Networking 57
IEEE802.11p
▪ New:802.11WAVEMode
▪ Defaultmodeofnodesin
WAVE
▪ Nodesmayalwaysuse
WildcardBSSinpackets
▪ NodeswillalwaysreceiveWildcardBSSpackets
▪ MayjoinBSSandsIlluse
WildcardBSS
Vehicular Networking 58
BSS SSID “A”
BSS SSID “B”
IEEE802.11p
▪ New:802.11WAVEBSS▪ NostrictseparaIonbetweenHostandAccessPoint(AP)▪ Instead,looseclassificaIonaccordingto:
▪ Equipment:RoadsideUnit(RSU)/On-BoardUnit(OBU)
▪ Roleindataexchange:Provider/User▪ NotechnicaldifferencebetweenProviderandUser▪ ProvidersendsOn-DemandBeacon
▪ Analogoustostandard802.11-Beacon▪ BeaconcontainsallinformaIonandparametersneededtojoin
▪ Userconfigureslowerlayersaccordingly▪ Startsusingprovidedservice▪ NoaddiIonalexchangeofdataneeded
▪ BSSmembershipnowonlyimplied▪ BSSconInuestoexistevenakerproviderleaves
Vehicular Networking 59
WAVEBSSInternalstatemachine
▪ NodewillnotjoinmorethanoneWAVEBSS
Vehicular Networking 60
[1]IEEEVehicularTechnologySociety,"IEEE1609.3(NetworkingServices),"IEEEStd,April,2007
WAVE Mode only
in WAVE BSS
§ ApplicaIonlayerstartsnewservice§ On-Demand-Beaconreceived
§ ApplicaIonlayerstopsservice§ Timeout
§ Securityerror
§ ApplicaIonlayerstartsnew,higherpriorityservice§ On-Demand-Beaconforknown,higherpriorityservicerecvd
IEEE802.11p
▪ IEEE802.11DistributedCoordinaIonFuncIon(DCF)▪ aka“ContenIonPeriod”
▪ PriorityaccessviaSIFS(ACK,CTS,...)andDIFS(payload)▪ WaitunIlmediumhasbeenfreeforduraIonofDIFS
▪ Ifmediumbusy,waitunIlidle,thenwaitDIFSplusrandombackoffIme
Mediumbusy TXstarts
SIFS, PIFS, DIFS
Time slots in contention period
Vehicular Networking 61
IEEE802.11p
▪ IEEE802.11DistributedCoordinaIonFuncIon(DCF)▪ Backoffif
a) Nodeisreadytosendandchannelbecomesbusy
b) Ahigherpriorityqueue(�nextslides)becomesreadytosend
c) Unicasttransmissionfailed(noACK)
d) Transmissioncompletedsuccessfully
▪ Backoff:Randomslotcountfrominterval[0,CW]
▪ Decrementbyoneakerchannelwasidleforoneslot(onlyincontenIonperiod)
▪ Incasesb)andc),doubleCW(butnolargerthanCWmax)
▪ Incased),setCWtoCWmin
Vehicular Networking 62
IEEE802.11p
▪ QoSin802.11p(HCF)▪ cf.IEEE802.11eEDCA▪ DIFS�AIFS(ArbitraIonInter-FrameSpace)
▪ DCF�EDCA(EnhancedDistributedChannelAccess)
▪ Classifyuserdatainto4ACs(AccessCategories)▪ AC0(lowestpriority)▪ …▪ AC3(highestpriority)
▪ EachACshasdifferent...▪ CWmin,CWmax,AIFS,TXOPlimit(max.conInuoustransmissions)
▪ ManagementdatausesDIFS(notAIFS)
Vehicular Networking 63
IEEE802.11p
▪ QoSin802.11p(HCF)▪ Map8userprioriIes�4accesscategories�4queues
▪ Queuescompeteindependentlyformediumaccess
AC0
AC1
AC2
AC3
virtu
al c
ollis
ion
Vehicular Networking 64
IEEE802.11p
▪ QoSin802.11p(HCF)▪ ParameterizaIon
▪ SamplequeueconfiguraIon
Parameter Value
SlotTime 13µs
SIFS 32µs
CWmin 15
CWmax 1023
Bandwidth 3..27mbit/s
Parameter AC_BK AC_BE AC_VI AC_VO
CWmin CWmin CWmin (CWmin+1)/2-1 (CWmin+1)/4-1
CWmax CWmax CWmax CWmin (CWmin+1)/2-1
AIFSn 9 6 3 2
Vehicular Networking 65
AC_VO AC_VI AC_BE AC_BK
ChannelAccess
Backoff:0 0 0 0
IEEE802.11p
Vehicular Networking 66
AC_VO AC_VI AC_BE AC_BK
Backoff:0 0 0 0
Channelbusy?
StartContenIon
WaitforIdle
IEEE802.11p
ChannelAccess
Vehicular Networking 67
AC_VO AC_VI AC_BE AC_BK
0 0 0
Backoff0?
WaitAIFS(SIFS+AIFSn*Slotlen)
Waitforbackoff=0
Backoff:0
IEEE802.11p
ChannelAccess
Vehicular Networking 68
Backoff:0
AC_VO AC_VI AC_BE AC_BK
Backoff:2 0 0 0
TransmissionOver
PostTransmitBackoff
IEEE802.11p
ChannelAccess
Vehicular Networking 69
2
AC_VO AC_VI AC_BE AC_BK
Backoff:2 0 0 0
AC_VIQueuereadytosend…waitAIFS Backoff
Chbecomesbusy
IEEE802.11p
ChannelAccess
Vehicular Networking 70
Backoff:2 21
AC_VO AC_VI AC_BE AC_BK
Backoff:1 0 0Channelidle
Channelbusy
[SlotImepassed]/DecrementBackoff
Channelstatechanges
Backoff:0 0
IEEE802.11p
ChannelAccess
Vehicular Networking 71
3Backoff:0 0
AC_VO AC_VI AC_BE AC_BK
0 0
Queuereadytosend
InternalContenIon
Backoff
Higherpriority
queueready
IEEE802.11p
ChannelAccess
Vehicular Networking 72
IEEE802.11p
▪ QoSinWAVE▪ meanwaiIngImeforchannelaccess,given
sampleconfiguraIon(andTXOPLimit=0�singlepacket)
▪ whenchannelidle:
▪ whenchannelbusy:
Vehicular Networking 73
FigureSource:Eichler,S.,"PerformanceevaluaIonoftheIEEE802.11pWAVEcommunicaIonstandard,"Proceedingsof66thIEEEVehicularTechnologyConference(VTC2007-Fall),BalImore,USA,October2007,pp.2199-2203
AC CWmin CWmax AIFS TXOP tw(inμs)
0 15 1023 9 0 264
1 7 15 6 0 152
2 3 7 3 0 72
3 3 7 2 0 56
UMTS/LTEvs.802.11p
▪ ProsofUMTS/LTE+ Easyprovisionofcentralizedservices+ QuickdisseminaIonofinformaIoninwholenetwork
+ Pre-deployedinfrastructure+ EasymigraIonto(andintegraIoninto)smartphones
▪ ConsofUMTS/LTE- Highshortrangelatencies(mightbetoohighforsafety)
- Networkneedsfurtherupgrades(smallercells,mulIcastservice)
- Highdependenceonnetworkoperator- Highloadincorenetwork,evenforlocalcommunicaIon
Vehicular Networking 74
UMTS/LTEvs.IEEE802.11p
▪ Prosof802.11p/Adhoc+ Smallestpossiblelatency
+ CansustainoperaIonwithoutnetworkoperator/provider+ Networkloadhighlylocalized+ BeZerprivacy(�laterslides)
▪ Consof802.11p/Adhoc- Needsgatewayforprovisionofcentralservices(e.g.,RSU)
- Nopre-deployedhardware,andhardwareissIllexpensive
▪ ThesoluIon?▪ hybridsystems:
deploybothtechnologiestovehiclesandroad,decidedependingonapplicaIonandinfrastructureavailability
Vehicular Networking 75
HigherLayerStandards:CALM
▪ Mixed-mediacommunicaIon
▪ „CommunicaIonsaccessforlandmobiles“
▪ ISOTC204WorkingGroup16
▪ IniIaIvetotransparentlyusebestpossiblemedium
▪ Integrates:▪ GPRS,UMTS,WiMAX
▪ Infrared,MillimeterWave
▪ Wi-Fi,WAVE
▪ UnidirecIonaldatasources(DAB,GPS,...)▪ WPANs(BlueT,W-USB,...)
▪ AutomoIvebussystems(CAN,Ethernet,...)
Vehicular Networking 76
[1]ISO21210,“Intelligenttransportsystems--CommunicaIonsaccessforlandmobiles(CALM)--IPv6Networking“
HigherLayerStandardsforIEEE802.11p
▪ Channelmanagement▪ Dedicatedfrequencybandat5.9GHzallocatedtoWAVE
▪ ExclusiveforV2VundV2IcommunicaIon
▪ Nolicensecost,butstrictrules▪ 1999:FCCreserves7channelsof10MHz(“U.S.DSRC”)
▪ 2reservedchannels,1+4channelsforapplicaIons▪ ETSIEuropereserves5channelsof10MHz
Vehicular Networking 77
[1]ETSIES202663V1.1.0(2010-01):IntelligentTransportSystems(ITS);EuropeanprofilestandardforthephysicalandmediumaccesscontrollayerofIntelligentTransportSystemsoperaInginthe5GHzfrequencyband
U.S.allocaIon …
CriIcalSafetyof
LifeSCH SCH
ControlChannel(CCH)
SCH SCH
Hi-PowerPublicSafety
…
EuropeanallocaIon SCH SCH SCH SCH CCH SCH SCH
IEEEChannel 172 174 176 178 180 182 184
Centerfrequency 5.860GHz 5.870GHz 5.880GHz 5.890GHz 5.900GHz 5.910GHz 5.920GHz
HigherLayerStandardsforIEEE802.11p
▪ Needforhigherlayerstandards▪ Unifiedmessageformat
▪ UnifiedinterfacestoapplicaIonlayer
▪ U.S.▪ IEEE1609.*▪ WAVE(„WirelessAccessinVehicularEnvironments“)
▪ Europe▪ ETSI▪ ITSG5(“IntelligentTransportaIonSystems”)
Vehicular Networking 78
IEEE1609.*upperlayers(buildingonIEEE802.11p)
▪ IEEE1609.2:Security
▪ IEEE1609.3:Networkservices
▪ IEEE1609.4:Channelmgmt.
▪ IEEE1609.11:ApplicaIon“electronicpayment”
Vehicular Networking 79
[1]Jiang,D.andDelgrossi,L.,"IEEE802.11p:TowardsaninternaIonalstandardforwirelessaccessinvehicularenvironments,"Proceedingsof67thIEEEVehicularTechnologyConference(VTC2008-Spring),MarinaBay,Singapore,May2008
[2]Uzcátegui,RobertoA.andAcosta-Marum,Guillermo,"WAVE:ATutorial,"IEEECommunicaIonsMagazine,vol.47(5),pp.126-133,May2009
TCP/UDP
WAVEPHY
ChannelCoordinaIon,WAVEMAC
IPv6WSMP
Management
Security
LLC
802.
11p 16
09.4
16
09.3
1609
.2
WAVEPHY
IEEE1609
▪ Channelmanagement▪ WAVEallowsforbothsingleradiodevices&mulIradiodevices
▪ DedicatedControlChannel(CCH)formgmtandsafetymessages�singleradiodevicesneedtoperiodicallylistentoCCH
▪ Timeslots▪ SynchronizaIonenvisionedviaGPSreceiverclock▪ Standardvalue:100mssyncinterval(with50msonCCH)▪ ShortguardintervalatstartofImeslot
▪ Duringguard,mediumisconsideredbusy(�backoff)
CCH interval
CCH interval
“SCH” interval
“SCH” interval
[1] IEEE Vehicular Technology Society, "IEEE 1609.4 (Multi-channel Operation)," IEEE Std, November, 2006
t = n × 1s
Vehicular Networking 80
IEEE1609
▪ Packettransmission▪ SortintoACqueue,basedonWSMP(orIPv6)EtherTypefield,desInaIonchannel,anduserpriority
▪ Switchtodesiredchannel,setupPHYpoweranddatarate
▪ Startmediumaccess
CC
H
SC
H
AC0
AC1
AC2
AC3 virt.
Col
lisio
n
AC0
AC1
AC2
AC3 virt.
Col
lisio
n
Cha
nnel
Rou
ter
Cha
nnel
sel
ectio
n an
d se
tup
Cha
nnel
acc
ess
Vehicular Networking 81
IEEE1609
▪ Channelmanagement
▪ ControlChannel(CCH):▪ DefaultchanneluponiniIalizaIon▪ WAVEserviceadverIsements(WSA),
WAVEshortmessages(WSM)
▪ Channelparameterstakefixedvalues
▪ ServiceChannel(SCH):▪ OnlyakerjoiningWAVEBSS
▪ WAVEshortmessages(WSM),
IPdatatraffic(IPv6)
▪ Channelparameterscanbechangedasneeded
Vehicular Networking 82
IEEE1609
▪ WAVEserviceadverIsement(WSA)▪ BroadcastonControlChannel(CCH)▪ IdenIfiesWAVEBSSsonServiceChannels(SCHs)
▪ CanbesentatarbitraryImes,byarbitrarynodes
▪ OnlypossibilitytomakeothersawareofdatabeingsentonSCHs,aswellastherequiredchannelparameterstodecodethem
NodeA NodeB WSA (on CCH)
Data (on S-CH)
Data (on S-CH)
Vehicular Networking 83
IEEE1609
▪ WAVEserviceadverIsement(WSA)▪ WAVEVersion(=0)
▪ ProviderServiceTable(PST)▪ n×ProviderServiceInfo
▪ ProviderServiceIdenIfier(PSID,max.0x7FFFFFFF)
▪ ProviderServiceContext(PSC,max.31chars)
▪ ApplicaIonpriority(maxpriority:63)▪ (opt.:IPv6addressandport,ifIPservice)▪ (opt.:SourceMACaddress,ifsender≠datasource)
▪ Channelnumber(max.200)
▪ 1..n×ChannelInfo(foreachchannelusedinPSTtable)▪ Datarate(fixedorminimumvalue)▪ Transmissionpower(fixedormaximumvalue)
▪ (opt.:WAVERouIngAnnouncement)
[1] IEEE Vehicular Technology Society, "IEEE 1609.3 (Networking Services)," IEEE Std, April, 2007
Vehicular Networking 84
WAVEserviceadverIsement(WSA)
0x0000000 system 0x000000D private 0x0000001 automaIc-fee-collecIon 0x000000E mulI-purpose-payment 0x0000002 freight-fleet-management 0x000000F dsrc-resource-manager 0x0000003 public-transport 0x0000010 aker-thek-systems 0x0000004 traffic-traveler-informaIon 0x0000011 cruise-assist-highway-system 0x0000005 traffic-control 0x0000012 mulI-purpose-informaIonsystem 0x0000006 parking-management 0x0000013 public-safety 0x0000007 geographic-road-database 0x0000014 vehicle-safety 0x0000008 medium-range-preinformaIon 0x0000015 general-purpose-internet-access 0x0000009 man-machine-interface 0x0000016 onboarddiagnosIcs 0x000000A intersystem-interface 0x0000017 securitymanager 0x000000B automaIc-vehicle-idenIficaIon 0x0000018 signedWSA 0x000000C emergency-warning 0x0000019 ACI
Vehicular Networking 85
▪ ProviderServiceIdenIfier(PSID)definedinIEEEStd1609.3-2007
IEEE1609
▪ WAVEShortMessage(WSM)
▪ Header(11Byte)▪ Version(=0)▪ Contenttype:plain,signed,encrypted▪ Channelnumber(max.200)
▪ Datarate▪ Transmissionpower
▪ ProviderServiceIdenIfier(Servicetype,max.0x7FFFFFFF)
▪ Length(max.typ.1400Bytes)
▪ Payload
Vehicular Networking 86
IEEE1609
▪ IPtraffic(UDP/IPv6orTCP/IPv6)▪ Header(40+nByte)
▪ Version▪ TrafficClass
▪ FlowLabel▪ Length▪ NextHeader▪ HopLimit
▪ Sourceaddress,desInaIonaddress▪ (opt.:ExtensionHeaders)
▪ Payload
▪ NoIPv6-Neighbor-Discovery(Highoverhead)▪ AllOBUslistentohostmulIcastaddress,
allRSUslistentoroutermulIcastaddress
Vehicular Networking 87
IEEE1609
▪ Channelqualitymonitoring▪ NodesstorereceivedWSAs,knowSCHoccupancy
▪ ReceivedChannelPowerIndicator(RCPI)polling▪ NodescansendRCPIrequests▪ ReceiveranswerswithReceivedSignalStrength(RSS)ofpacket
▪ TransmitPowerControl(TPC)▪ NodescansendTPCrequests▪ ReceiveranswerswithcurrenttransmissionpowerandLQI
▪ DynamicFrequencySelecIon(DFS)▪ Nodesmonitortransmissionsonchannel(acIvelyandpassively)
▪ Ifhigherprioritythirdpartyuse(e.g.,RADAR)isdetected,nodesceasetransmiçng
Vehicular Networking 88
IEEE1609
▪ SecurityinWAVE▪ NatureofWAVEmessagesmandatestrustbetweennodes
▪ Ex:Greenwaveforemergencyvehicles
▪ SecurityisbuiltintoWAVE(IEEE1609.2)
▪ WAVEcantransparentlysign,verify,encrypt/decryptmessageswhensendingandreceiving
▪ Ex:WSAàSecureWSA
▪ AuthorizaIonofmessagesneeded▪ Byrole:CA,CRL-Signer,RSU,PublicSafetyOBU(PSOBU),OBU▪ ByapplicaIonclass(PSID)and/orinstance(PSC)▪ ByapplicaIonpriority▪ BylocaIon▪ ByIme
[1] IEEE Vehicular Technology Society, "IEEE 1609.2 (Security Services)," IEEE Std, July, 2006
Vehicular Networking 89
IEEE1609
▪ Securityconcepts▪ Basicsecuritygoals
▪ Integrity,ConfidenIality,AuthenIcity▪ Non-RepudiaIon
▪ Mechanisms▪ SymmetricencrypIon
▪ SecretKeyCryptography▪ Ex:Caesarcipher,Enigma,AES
▪ AsymmetricencrypIon▪ PublicKeyCryptography▪ Ex:RSA,ElGamal,ECC
▪ (cryptographic)hashing▪ Ex:MD5,SHA-1
m E(m)
K
K
m E(m)
K+
K-
m h(m)
Vehicular Networking 90
IEEE1609
▪ AsymmetricCryptography▪ ReliesoncertainmathemaIcalproceduresbeingveryhardtoinvert▪ Product⬄factorizaIon(RSA)
▪ Nthpower⬄Nthlogarithm(DH,ElGamal)
▪ Twokeys:PublicKey(K+),PrivateKey(K-)
▪ CanbeusedinbothdirecIons▪ EncrypIon:E(K+,m),Signing:E(K-,h(m))
▪ Drawback:▪ Muchslowerthansymmetriccryptography
m
E(K-,m) K+
E(K+,m)
K-
K-
K+
Vehicular Networking 91
IEEE1609
▪ AsymmetricCryptographyExample:RSA▪ Chosetwoprimes:q,pwithq!=p
▪ Calculaten=p·q▪ Calculateφ(n)=(p−1)·(q−1) φ(x)givesnumberof(smaller)co-primesforx.
Basedonφ(a·b)=φ(a)·φ(b)·(d/φ(d))withd=gcd(a,b)
Ifxisprime,thisisx−1.
▪ Chooseeco-primetoφ(n)with1<e<φ(n)
▪ CalculatedusingEEA,sothate·dmodφ(n)=1
▪ PublicKey:K+={e,n},PrivateKey:K-={d,n}.▪ En/DecrypIon: Memodn=C
Cdmodn=M
Vehicular Networking 92
IEEE1609
▪ CerIficates▪ EncrypIonisuselesswithoutauthenIcaIon
▪ Alice⬄Eve⬄Bob
▪ EvecanpretendtobeAlice,replaceK+AwithownkeyK
+E
▪ SoluIon:useTrustedThirdParty(TTP)andcerIficates▪ TTPsigns(Name,Key)tuple,vouchesforvalidityandauthorizaIon:“AlicehasPublicKeyK+A,mayparIcipateasOBUunIl2019”
▪ not:“whoeversendsthispacketisAlice”▪ not:“whoeversendsthispackethasPublicKeyK+A”
▪ SendK+AtogetherwithcerIficatevouchingfortuple
Vehicular Networking 93
IEEE1609
▪ ImplementaIoninWAVE▪ CerIficatesignaturechains
▪ RootcerIficate�cerIficate�cerIficate�payload▪ RootcerIficatespre-installedwithsystem▪ OthercerIficatescannotbeassumedtobepresent
▪ NodesmustdownloadcerIficatesalongwithsignedmessage▪ IncludechainofcerIficates▪ …orSHA-256offirstcerIficateinchain(ifreceivercanbeassumedtohaveallrequiredcerIficates)
Vehicular Networking 94
IEEE1609
▪ ImplementaIoninWAVE▪ X.509formatstoolarge�newWAVEcerIficateformat
▪ Version▪ CerIficate
▪ Role(RSU,PSOBU,OBU,...)▪ IdenIty(dependentonrole)▪ RestricIons(byapplicaIonclass,priority,locaIon,…)▪ ExpiraIondate▪ ResponsibleCRL▪ PublicKeys
▪ Signature
▪ New:RestricIonbylocaIone.g.:none,inheritedfromCA,circle,polygon,setofrectangles
▪ PublicKeyalgorithms(moIvatedbykeysize):ECDSA(NISTp224),ECDSA(NISTp256),ECIES(NISTp256),...
Vehicular Networking 95
CompletepacketformatofaWSM:
Vehicular Networking 96
Length Field
1 WSMversion
1 SecurityType=signed(1)
1 ChannelNumber
1 DataRate
1 TxPwr_Level
4 PSID
1 PSCFieldLength
7 PSC
2 WSMLength
1
WSMData
signertype=cerIficate
125 cerIficate
2
unsigned_wsm
messageflags
32 applicaIon_data
8 transmission_Ime
4
transmission_locaIon
laItude
4 longitude
3 elevaIon_and_confidence
28signature ecdsa_signature
r
28 s
� next slide
Ex: Signed WSM of an OBU, Certificate issuer is known
CompletepacketformatofaWSM(cerIficatepart):
Vehicular Networking 97
Length Field
1 cerIficate_version=1
1
unsigned_cerIficate
subject_type=obu_idenIfied
8 signer_id
1
scope
subject_namelength
8 subject_name
2applicaIons
lengthofapplicaIonsfield
1 type=from_issuer
4 expiraIon
4 crl_series
1
public_key
lengthofpublickeyfield
1 algorithm=ecdsanistp224..
29 public_key point
32signature ecdsa_signature
r
32 s
DrawbacksofChannelSwitching
▪ 1)Goodput▪ UserdatamustonlybesentonSCH,i.e.duringSCHinterval
�goodputcutinhalf
Vehicular Networking 98
Picturesource:DavidEckhoff,ChristophSommerandFalkoDressler,"OntheNecessityofAccurateIEEE802.11pModelsforIVCProtocolSimulaIon,"Proceedingsof75thIEEEVehicularTechnologyConference(VTC2012-Spring),Yokohama,Japan,May2012.
Goo
dput
>
Road traffic density >
DrawbacksofChannelSwitching
▪ 2)Latency▪ UserdatageneratedduringCCHintervalisdelayedunIlSCHintv.
Vehicular Networking 99
Picturesource:DavidEckhoff,ChristophSommerandFalkoDressler,"OntheNecessityofAccurateIEEE802.11pModelsforIVCProtocolSimulaIon,"Proceedingsof75thIEEEVehicularTechnologyConference(VTC2012-Spring),Yokohama,Japan,May2012.
DrawbacksofChannelSwitching
▪ 3)Collisions▪ DelayofdatatonextstartofSCHinterval�increasedfrequencyofchannelaccessesdirectlyakerswitch
�increasedcollisions,packetloss
Vehicular Networking 100
Picturesource:DavidEckhoff,ChristophSommerandFalkoDressler,"OntheNecessityofAccurateIEEE802.11pModelsforIVCProtocolSimulaIon,"Proceedingsof75thIEEEVehicularTechnologyConference(VTC2012-Spring),Yokohama,Japan,May2012.
Msggenerated
Msgsent
ETSIITSG5
▪ MoIvaIon
▪ EuropeanstandardizaIoneffortbasedonIEEE802.11p▪ StandardizaIontoincludelessonslearnedfromWAVE
▪ DifferentinstrumentaIonoflowerlayers
▪ Differentupperlayerprotocols▪ Fine-grainedservicechannelassignment
▪ ITS-G5A(safety)▪ IST-G5B(nonsafety)
Vehicular Networking 101
ETSIITSG5
▪ Protocolstack▪ PHYandMACbasedonIEEE802.11p
▪ Mostprominentchange:
crosslayerDecentralizedCongesIonControl(DCC)
Vehicular Networking 102
AccessLayer
Networking&TransportLayer
FaciliIesLayer
ApplicaIonsLayer
Management
DCC
Security
ETSIITSG5
▪ Channelmanagement▪ MulIradio,mulIantennasystem
▪ NoalternaIngaccess�CircumventsproblemswithsynchronizaIon�NoreducIoningoodput
▪ DirectresultofexperienceswithWAVE
▪ OneradiotunedtoCCH▪ ServiceAnnouncementMessage(SAM)
▪ Periodic:CooperaIveAwarenessMessages(CAM)
▪ Eventbased:DecentralizedEnvironmentNoIficaIonMessage(DENM)
▪ Addl.radiotunedtoSCH▪ Userdata
Vehicular Networking 103
ETSIITSG5
▪ Mediumaccess▪ SeparateEDCAsystems
▪ Differentdefaultparameters:
▪ Conten%onWindow–lessdistancetolowerpriorityqueues�lessstarvaIonoflowerpriorityqueues
Parameter AC_BK AC_BE AC_VI AC_VO
CWmin CWmin (CWmin+1)/2-1 (CWmin+1)/4-1 (CWmin+1)/4-1
CWmax Cwmax CWmax (CWmin+1)/2-1 (CWmin+1)/2-1
AIFSn 9 6 3 2
Vehicular Networking 104
ETSIITSG5
▪ DCC▪ CorefeatureofETSIITSG5▪ AdapIveparameterizaIontoavoidoverload
▪ ConfigurableparametersperAC:▪ TXpower▪ Minimumpacketinterval
▪ SensiIvityofCCA(ClearChannelAssessment)
▪ Datarate▪ Statemachinedetermineswhichparametersareselected;availablestates:
▪ Relaxed▪ AcIve(mulIplesubstates)
▪ RestricIve
Vehicular Networking 105
▪ DCC▪ StatemachineforControlChannel:
▪ min/maxChannelLoad(x):recordfracIonofImein[tnow-x..tnow]thatchannelwassensedbusysubdivideintervalintoequalparts(e.g.50ms),takemin/max
▪ Channelbusy⬄measuredreceivedpower(signalornoise)aboveconfiguredsensibility
ETSIITSG5
Vehicular Networking 106
relaxed acIve restricIve
minChannelLoad(1s) >= 15% minChannelLoad(1s) >= 40%
maxChannelLoad(5s) < 15% maxChannelLoad(5s) < 40%
ETSIITSG5
▪ DCC▪ SelecIonofparameterswhenchangingstates
▪ ServiceChannel:AcIvestatehasfoursub-configuraIons▪ ControlChannel:SingleconfiguraIonforacIvestate▪ Example(“ref”:Valueremainsunchanged)
StateRelaxed AcIve RestricIve
AC_VI AC_VO AC_BE AC_BK
TXpower 33dBm ref 25dBm 20dBm 15dBm -10dBm
Minpktinterval 0,04s ref ref ref ref 1s
Datarate 3Mbit/s ref ref ref ref 12Mbit/s
SensiIvity -95dBm ref ref ref ref -65dBm
Vehicular Networking 107
ETSIITSG5
▪ CooperaIveAwarenessMessage▪ Periodic(upto10Hz)safetymessage
▪ InformaIononstateofsurroundingvehicles:▪ Speed,locaIon,…
▪ Messageagehighlyrelevantforsafety▪ Needmechanismstodiscardoldmessages
▪ SafetyapplicaIonsrelyonCAMs:▪ Tailendofjam
▪ Rearendcollision▪ IntersecIonassistance…
▪ SentonCCH▪ Generatedevery100ms..1s,butonlyif∆angle(>4°),∆posiIon(>5m),∆speed(>1m/s)
Vehicular Networking 108
ETSIITSG5
▪ CAMformatLength[byte] Field
1 messageId(0=CAM,1=DENM)
8 generaIonTime
4 StaIonId
1
StaIonCharacterisIcs
mobileITSStaIon
1 privateITSStaIon
1 physicalRelevantITSStaIon
8+8+4
ReferencePositon
Longitude/Longitude/ElevaIon
4 Heading
32+4 Streetname/RoadSegmentID
1 PosiIon/HeadingConfidence
1
CamParameters vehicleCommonParameters
vehicleType
2+2 Length/Width
4 Speed
2 AcceleraIon
1 AcceleraIonControl(break,throZle,ACC)…
1 exteriorLights
1 Occupancy
1+1 crashStatus/dangerousGoods
Vehicular Networking 109
ETSIITSG5
▪ DecentralizedEnvironmentalNoIficaIonMessage(DENM)
▪ Eventtriggered(e.g.,byvehiclesensors)▪ Hardbraking▪ Accident▪ Tailendofjam
▪ ConstrucIonwork▪ Collisionimminent
▪ Lowvisibility,highwind,icyroad,…▪ Messageshave(Ight)localscope,relaybasedon
▪ Area(definedbycircle/ellipse/rectangle)▪ Roadtopology▪ DrivingdirecIon
Vehicular Networking 110
DENMformat(excerpt)
Vehicular Networking 111
Length[byte] Field
1 messageId(0=CAM,1=DENM)
6 generaIonTime
4
Management
OriginatorID Whosentthis?
2 SequenceNumber
1 DataVersion IsthisanupdateonasituaIon?
6 ExpiryTime IsthissIllvalid?
1 Frequency WhencanIexpectanupdate?
1 Reliability ShouldItrustasinglenoIficaIon?
IsNegaIon DoesthiscancelanearliernoIficaIon?
1
SituaIon
CauseCode
1 SubCauseCode
1 Severity
4
LocaIonContainer
SituaIon_LaItude
4 SituaIon_Longitude
2 SituaIon_AlItude
4 Accuracy
N-40 RelevanceArea
ETSIITSG5
▪ ServiceAnnouncement
▪ MessageonControlChanneltoadverIseservicesofferedon
ServiceChannels
▪ Channelnumber
▪ Typeofservice▪ …
▪ SimilartoWAVEServiceAnnouncement(WSA)
▪ Receivercantune(itssecondradio)toadverIsedchannel
Vehicular Networking 112
ETSIITSG5
▪ Securityandprivacy▪ NopublishedspecificaIon(yet)
▪ KerberosorWAVE-likePKI
▪ RestrictparIcipaIontoauthorizedvehicles▪ Signmessages
▪ LimitV2IandI2Vtrafficwherepossible
▪ Usepseudonymstoprotectprivacy
▪ UsebaseidenIty(inpermanentstorage)toauthenIcatewith
infrastructure
▪ Infrastructuregeneratespseudonymforvehicle
Vehicular Networking 113
ETSIITSG5:AnalysisandProblems
▪ OscillaIngchannelload(bothlocalandglobal!)▪ …causedbychannelaccessbeingtoorestricIve(standardparameters)
Vehicular Networking 114
Picturesource:DavidEckhoff,NikoleZaSofraandReinhardGerman,"APerformanceStudyofCooperaIveAwarenessinETSIITSG5andIEEEWAVE,"Proceedingsof10thIEEE/IFIPConferenceonWirelessOndemandNetworkSystemsandServices(WONS2013),Banff,Canada,March2013.
ETSIITSG5:AnalysisandProblems
▪ Latencies▪ Choosingminimumpacketintervals(TRC)toohighcan
introducehighlatencies
Vehicular Networking 115
Picturesource:DavidEckhoff,NikoleZaSofraandReinhardGerman,"APerformanceStudyofCooperaIveAwarenessinETSIITSG5andIEEEWAVE,"Proceedingsof10thIEEE/IFIPConferenceonWirelessOndemandNetworkSystemsandServices(WONS2013),Banff,Canada,March2013.
ETSIITSG5:AnalysisandProblems
▪ Updatefrequency▪ StandardparametersaretoorestricIve
▪ ChannelresourcesarenotusedopImally
Vehicular Networking 116
Picturesource:DavidEckhoff,NikoleZaSofraandReinhardGerman,"APerformanceStudyofCooperaIveAwarenessinETSIITSG5andIEEEWAVE,"Proceedingsof10thIEEE/IFIPConferenceonWirelessOndemandNetworkSystemsandServices(WONS2013),Banff,Canada,March2013.
MainTakeaways
▪ BroadcastMedia▪ TMC,TPEG
▪ UMTS▪ Channels,Pros/Cons
▪ DSRC/WAVElowerlayers▪ 802.11pvs.old802.11:commonaliIesanddifferences
▪ HCF(EDCAQoS)
▪ IEEE1609.*upperlayers▪ Channelmanagement
▪ Security/CerIficates
▪ ETSIITSG5▪ Channelmanagement
▪ DCC:DecentralizedCongesIonControl
▪ Messagetypes▪ CommonaliIesanddifferenceswrt.IEEE1609.*
Vehicular Networking 117
Broadcast,Geocast,RouIng
Vehicular Networking 118
RouIng
▪ ClassicalapproachestorouIng▪ DistanceVectorRouIng
▪ NodeskeepvectorofknowndesInaIons,storedistanceandnexthop
▪ Ex:DSDV
▪ LinkStateRouIng▪ Nodeskeeptrackofofalllinksinnetwork
▪ Pro:fastandguaranteedconvergence
▪ Con:highoverhead▪ Ex:OLSR
Vehicular Networking 119
RouIng
▪ ClassicalapproachestorouIng(II)▪ ReacIve(ondemand)rouIng
▪ Routesestablishedwhenneeded▪ RouIngmessagesonlyexchangedif(orwhile)userdataisexchanged
▪ Unusedroutesexpire▪ Ex:AODV,DYMO
▪ ProacIve(tabledriven)rouIng▪ RoutesareestablishedandmaintainedconInuously
▪ Noroutesetupdelaywhendataneedstobesent
▪ Highoverhead▪ Ex:OLSR,DSDV
i
?
i i
? ?
Vehicular Networking 120
RouIng
▪ ClassicalapproachestorouIng(III)▪ Hop-by-HopRouIng
▪ EachpacketcontainsdesInaIonaddress
▪ DuringrouIng,eachhopchosesbestnexthop
▪ Ex:AODV
▪ SourceRouIng▪ EachpacketcontainscompleteroutetodesInaIon
▪ DuringrouIng,nodesrelyonthisinformaIon
▪ Ex:DSR
Vehicular Networking 121
RouIng
▪ GeorouIng▪ Primarymetrics:posiIon/distancetodesInaIon
▪ RequiresnodeposiIonstobeknown(atleastforthedesInaIon)
▪ TwooperaIonmodes(typ.):▪ Greedymode:choosenexthopaccordingtomaxprogress▪ Recoverymode:escapedeadends(localmaxima)
▪ Mustensurethatmessagenevergetslost
Vehicular Networking 122
RouIng
▪ GeorouIng:CBF▪ „ContenIonBasedForwarding“▪ ReducIon(orcompleteavoidance)ofduplicates
▪ Outline▪ Given:posiIonofmessagedesInaIon,posiIonoflasthop
▪ Donotforwardmessageimmediately,butwaitforImeT
▪ ChoosewaitImeTaccordingtosuitabilityofnode
▪ Donotforwardmessageifanotherforwardwasoverheard
▪ Problem▪ PotenIalforwardersmustbeabletooverheareachothers’transmissions
Vehicular Networking 123
[1]Füßler,HolgerandWidmer,JörgandKäsemann,MichaelandMauve,MarInandHartenstein,Hannes,"Conten@on-basedforwardingformobileadhocnetworks,"AdHocNetworks,vol.1(4),pp.351-369,2003
RouIng
▪ GeorouIng:CBF▪ PotenIalforwardersarecontainedinReuleauxtriangle(1)(useesImatedcommunicaIonrangeforthicknessoftriangle)
▪ WaiIngImeisT=1-P�(z:desInaIon,f:lasthopforwarder)
▪ Iflasthopoverhearsnonodeforwardingthemessage,messageisre-sentfornodesin(2),then(3)
Vehicular Networking 124
IllustraIonsource:Füßler,HolgerandWidmer,JörgandKäsemann,MichaelandMauve,MarInandHartenstein,Hannes,"Conten@on-basedforwardingformobileadhocnetworks,"AdHocNetworks,vol.1(4),pp.351-369,2003
RouIng
▪ ReflecIononclassicalrouIngapproaches▪ Q:Can(classical)rouIngworkinVANETs?
▪ A:Onlyinsomecases.
▪ CommonlyneedmulIcastcommunicaIon,lowload,lowdelay
▪ AddiIonalchallengesandopportuniIes:networkparIIoning,dynamictopology,complexmobility,…
Vehicular Networking 125
[1]Toor,YasserandMühlethaler,PaulandLaouiI,AnisandFortelle,ArnauddeLa,"VehicleAdHocNetworks:Applica@onsandRelatedTechnicalIssues,"IEEECommunicaIonsSurveysandTutorials,vol.10(3),pp.74-88,2008
Car-to-X
Non-Safety
Comfort
ContextualInformaIon Entertainment
TrafficInformaIonSystems
OpImalSpeedAdvisory
CongesIon,Accident
InformaIon
Safety
SituaIonAwareness
AdapIveCruiseControl
BlindSpotWarning
WarningMessages
TrafficLightViolaIon
ElectronicBreakLight
<!> <!>
<!>
<!>
<!>
<!>
<!>
<!>
idle send
rcv dup
Flooding
▪ Flooding(MulI-HopBroadcast)▪ Simplestprotocol:„SmartFlooding“:
▪ Problem:BroadcastStorm▪ Superfluousre-broadcastsoverloadchannel
Vehicular Networking 126
Flooding
▪ Consequencesofabroadcaststorm
▪ Interference àimpactonothersystems
▪ Collision àimpactonotherusers
▪ ContenIon àimpactonotherapplicaIons
Vehicular Networking 127
Flooding
▪ Solvingthebroadcaststormproblem
▪ Classicalapproaches▪ LightweightsoluIons(e.g.,probabilisIcflooding)▪ ExchangeofneighborinformaIon,cost/benefitesImaIons
▪ TopologycreaIonandmaintenance(Cluster,Cord,Tree,…)
▪ Drawbacks▪ Blindguessing(orscenariodependentparameterizaIon)
▪ AddiIonalcontrolmessageoverhead
▪ ConInuousmaintenanceoftopology
Vehicular Networking 128
Flooding
▪ VANETspecificsoluIon:BroadcastSuppression▪ NeedsnoneighborinformaIon
▪ Needsnocontrolmessages
▪ Maximizesdistanceperhop
▪ Minimizespacketloss
▪ Approach▪ Nodereceivesmessage,esImatesdistancetosender
▪ SelecIvelysuppressesre-broadcastofmessage
▪ AlternaIves▪ weightedp-persistence▪ sloZed1-persistence▪ sloZedp-persistence
Vehicular Networking 129
[1]Wisitpongphan,NawapornandTonguz,OzanK.andParikh,J.S.andMudalige,PriyanthaandBai,FanandSadekar,Varsha,"BroadcastStormMi@ga@onTechniquesinVehicularAdHocNetworks,"IEEEWirelessCommunicaIons,vol.14(6),pp.84-94,December2007
Flooding
▪ BroadcastSuppression▪ EsImatedistancetosenderasbasedon("approximate
transmissionradius")
▪ Variant1:GPSbased
▪ Variant2:RSSbased
Vehicular Networking 130
Flooding
▪ BroadcastSuppression▪ Weightedp-persistence
▪ ProbabilisIcfloodingwithvariablepijforre-broadcast▪ Thus,higherprobabilityforlargerdistanceperhop
pij
Vehicular Networking 131
Flooding
▪ BroadcastSuppression▪ Weightedp-persistence
▪ WaitWAIT_TIME(e.g.,2ms)
▪ choosep=min(pij)=min(ρij)ofallreceivedpackets
(probabilityforre-broadcastofpacket)
▪ Ensurethatatleastoneneighborhasre-broadcastpacket
idle wait 2ms rcv
dup
send p
wait 2.1ms
¬p
dup expired
dup
Vehicular Networking 132
Flooding
▪ BroadcastSuppression▪ SloZed1-persistence
▪ SuppressionbasedonwaiIngandoverhearing▪ Dividelengthofroadintoslots▪ Moredistantslotssendsooner
▪ Closerslotssendlater(orifmoredistantslotsdidnotre-broadcast)
▪ Thus,higherprobabilitytotransmitoverlongerdistance
pij t=0 t=τ t=2τ t=3τ
Vehicular Networking 133
Flooding
▪ BroadcastSuppression▪ SloZed1-persistence
▪ Divide“communicaIonrange“intoNsslotsoflengthτ
▪ Nodeswaitbeforere-broadcast,waiIngImeTij=τ×⎡Ns(1-ρij)⎤
▪ DuplicateeliminaIontakescareofsuppressionofbroadcasts
idle wait Tij rcv
dup
send ¬dup
dup
Vehicular Networking 134
Flooding
▪ BroadcastSuppression▪ SloZedp-persistence
▪ Cf.sloZed1-persistence▪ Fixedforwardingprobabilityp(insteadof1)
pij t=0 t=τ t=2τ t=3τ
Vehicular Networking 135
Flooding
▪ BroadcastSuppression▪ SloZedp-persistence
▪ WaitforTij(insteadoffixedWAIT_TIME)
▪ Useprobabilityp(insteadof1)▪ Ensurethatatleastoneneighborhasre-broadcastthepacketbywaiIngforδ’>max(Tij)
idle wait Tij rcv
dup
send p
wait δ’
¬p
dup expired dup
Vehicular Networking 136
Flooding
▪ BroadcastSuppression▪ SolvesBroadcastStormProblem
▪ Maximizesdistanceperhop
▪ Minimizespacketloss
▪ But:Muchhigherper-messagedelay
Vehicular Networking 137
Remainingproblems
▪ TemporarynetworkfragmentaIon
▪ UndirectedmessagedisseminaIon
Vehicular Networking 138
Vehicular Networking 139
<!>
Flooding+X
▪ DV-CAST▪ Idea:detectcurrentscenario,switchbetweenprotocols▪ Checkforfragmentednetwork
▪ Networkconnectedàperformbroadcastsuppression
▪ NetworkfragmentedàperformStore-Carry-Forward
[1]Tonguz,OzanK.andWisitpongphan,N.andBai,F.,"DV-CAST:Adistributedvehicularbroadcastprotocolforvehicularadhocnetworks,"IEEEWirelessCommunicaIons,vol.17(2),pp.47-57,April2010
Flooding+X
▪ DV-CAST:Mechanism▪ NodesperiodicallysendHellobeaconscontainingposiIon,speed▪ Nodesmaintain3neighbortables
▪ SamedirecIon,ahead
▪ SamedirecIon,drivingbehind
▪ OppositedirecIon▪ MessagescontainsourceposiIonandRegionofInterest(ROI)
▪ Foreachmessagereceived,evaluate3Flags:▪ DesInaIonFlag(DFlg):VehicleinROI,approachingsource
▪ MessageDirecIonConnecIvity(MDC):�neighbordrivinginsamedirecIon,furtherawayfromsource
▪ OppositeDirecIonConnecIvity(ODC):�neighbordrivinginoppositedirecIon
Vehicular Networking 140
Flooding+X
Vehicular Networking 141
Picturesource:Tonguz,OzanK.andWisitpongphan,N.andBai,F.,"DV-CAST:Adistributedvehicularbroadcastprotocolforvehicularadhocnetworks,"IEEEWirelessCommunicaIons,vol.17(2),pp.47-57,April2010
▪ DV-CAST▪ Algorithm:
Flooding+X
Vehicular Networking 142
▪ DV-CAST▪ Decisionmatrix:
MDC ODC DFlg DerivedScenario Ac@onsTakenbyDV-CASTProtocol
1 × 1 WellConnected BroadcastSuppression
1 × 0 WellConnected Helprelaythepacketbydoingbroadcastsuppression
0 1 1 SparselyConnected
RebroadcastandassumethattheODNwillhelprelayorrebroadcast
0 1 0 SparselyConnected
Rebroadcastandhelpcarry&forwardthepackettothefirstnewneighborintheoppositedirecIonorin
themessagedirecIonencountered
0 0 × TotallyDisconnected WaitandforwardthepackettothefirstneighborintheoppositedirecIonorinthemessagedirecIon
encountered.
Flooding+X
▪ DV-CAST▪ SimulaIonresultsshowthat(onfreewayswithlowtomedium
nodedensiIes)DV-CASTbeatssimplefloodingintermsofbroadcastsuccessrateanddistancecovered
Vehicular Networking 143
IntermediateSummary
▪ Remainingproblems
▪ TemporarynetworkfragmentaIon(solved)
▪ UndirectedmessagedisseminaIon
✓
Vehicular Networking 144
Geocast
▪ TO-GO▪ „Topology-AssistedGeo-OpportunisIcRouIng“▪ NodesperiodicallysendHellobeacons;Contents:
▪ Numberofneighbors
▪ BloomfilterofneighborIDs
▪ IDsofneighborsfurthestdowntheroad/roads▪ Thus,nodesknowaboutall2-hopneighbors
Vehicular Networking 145
[1]Lee,K.C.andLee,U.andGerla,M.,"Geo-Opportunis@cRou@ngforVehicularNetworks,"IEEECommunica%onsMagazine,vol.48(5),pp.164-170,May2010
Geocast
▪ BloomFilter▪ Idea:
▪ BloomfilterisabitfieldX
▪ HashfuncIonsh1tohkmapinputdataxàonebit(each)inX
▪ InserIonofx:Set X[hi(x)]←1 �i�[1..k]
▪ Testforx�X:Check X[hi(x)]�1 �i�[1..k]
▪ ProbabilisIctestfor“x�X”▪ Possibleresults:no/maybe(àchanceoffalseposiIves)
▪ AllowsforverycompactrepresentaIonofX
Vehicular Networking 146
[1]Bloom,BurtonH.,"Space/@metrade-offsinhashcodingwithallowableerrors,"Communica%onsoftheACM,vol.13(7),pp.422-426,1970
0 1 0 0 0 1 0 1
“foo”
h1 h2 h3
Geocast
▪ TO-GO▪ Step1:Findbestnexthop(TargetNode,T)
▪ FindN:FurthestneighbortowardsdesInaIon▪ FindJ:FurthestneighbortowardsdesInaIon,currentlyonjuncIon▪ FindNJ:FurthestneighbortowardsdesInaIon,asseenbyJ
▪ ifN,NJareonthesameroad(andrunningingreedymode),pickNelse,pickJ
N
NJ
J
Vehicular Networking 147
Geocast
▪ TO-GO▪ Step2:FindForwardingSet(FS)
▪ NodesintheFSwillcompeteforrelayingofthemessage
▪ OnlyonenodeinFSshouldrelaythus,allnodesinFSmustheareachother
▪ FindingopImalsoluIonisNPcomplete▪ TO-GOusesapproximaIon:
▪ Bloomfilterentriesindicatewhocanhearwhom
▪ GiventhetargetnodeT,finditsneighborMwiththemaximumnumberofneighbors
▪ IncludeallthoseneighborsinFS,which▪ canhearM,and
▪ areheardbyM,and▪ areheardbyallcurrentmembersofFS
Vehicular Networking 148
Geocast
▪ TO-GO▪ Step3:MulIcastmessagetoallnodesinFS
▪ NodesintheFScompeteforrelayingofthemessage
▪ EnsuremaximumprogresswithinFS
▪ Delayre-broadcastbyt▪ Suppressre-broadcastifanothernodesforwardswithint▪ t=τ×dT/dmax
with:
▪ τ:Maximumdelayperhop
▪ dT:DistancetoTargetNode▪ dmax:DistancefromlasthoptoTargetNode
Vehicular Networking 149
IntermediateSummary
▪ Remainingproblems
▪ TemporarynetworkfragmentaIon(solved)
▪ UndirectedmessagedisseminaIon(solved)
✓ ✓
Vehicular Networking 150
Scalability
▪ Dothepresentedapproachesscale?▪ AnalyIcalevaluaIon[1]:
▪ Capacityofwirelesschannelislimited
▪ AmountofinformaIontransportedacrossany(arbitrary)bordermustbeupper-bounded
Vehicular Networking 151
[1]B.Scheuermann,C.Lochert,J.Rybicki,andM.Mauve,“AFundamentalScalabiliyCriterionforDataAggrega@oninVANETs,”inACMMobiCom2009.Beijing,China:ACM,September2009
Σ≤ξr
Scalability
▪ SoluIon?▪ DefinemaximumdisseminaIonrangeofanyinformaIon
▪ Reduceupdatefrequencywithincreasingdistance▪ AggregateinformaIonasdistanceincreases
▪ Pre-condiIonforscalabilityofdisseminaIonapproach?▪ Usedbandwidthreducesasdistancetosourceincreases▪ Upperbound:1/d2
distance d
used bandwidth B � 1 / d2
Vehicular Networking 152
MainTakeaways
▪ ClassicinformaIondisseminaIon
▪ Distancevs.link-state▪ ReacIvevs.proacIve▪ Hop-by-hopvs.sourcerouIng▪ Geo-rouIng(CBF)
▪ ExamplesofVANET-centricinformaIondisseminaIon
▪ Flooding(Weighted/SloZed1/p-Persistence)
▪ FragmentaIon(DV-Cast)
▪ Directedness(To-Go)▪ Scalability
Vehicular Networking 153