Exploring the Design and Implementation of Vehicul

ExploringtheDesignandImplementationofVehicularNetworkedSystemsLiviuIftodeDepartmentofComputerScience,RutgersUniversityCristianBorceaDepartmentofComputerScience,NewJerseyInstituteofTechnologyNishkamRaviDepartmentofComputerScience,RutgersUniversityTamerNadeemDepartmentofComputerScience,UniversityofMaryland,CollegePark1IntroductionInanincreasinglycomputerizedandconnectedworld,oneofthemostubiquitoustechnologicalpresencesinourlife,thecar,hasbeen“resisting”thisinvasion.Atatimewhengadgetsexploitingcomputingandwirelessnetworkingbombardusfromeverydirection,carsremainaconservativetechnologicalislandwiththeinter-carcommunicationmostlyvisual(breakandreverselights,turnsignals,horn,etc),executedbythedriverandinventedalmostacenturyago1.Whenvisibilityislimited,suchasonafoggyday,aroundthecorner,orjustfurtheraheadonacongestedroad,thereisnoalternativesourceofinformationtoassistthedriverinhisdecisions.Moreover,beyondpassivesafetytechnologiessuchasseatbeltsandairbags,whichhavebeensubstantiallyimprovedoverthelastdecade,thereisatremendousopportunitytomoveforwardtoactivesafetyusingactiveaccidentavoidancetechnologies.Inspiteofcurrentadvancementsinvehiculartechnology,today,thetailoftrafficsafetyremainsthesame.AccordingtoarecentlyreleasedU.S.TrafficSafetyFactsReportbetween1973and2003thenumberofreportedtrafficaccidentshasremainedrelativelyconstant.Furthermore,thenumberofreportedfatalitieshasdecreasedbyonly10percentbetween1988and2003(42,130vs.38,252).Notsurprisingly,thismirrorscloselywithsimilarstatisticsrecentlyreleasedbytheEU.Beyondthecostinhumanlives,thefinancialimpactofthisisstaggering.Theannualcostsassociatedwithtrafficaccidentsarenearly1TrillionUSdollars.Thisisequivalenttoalmost3percentoftheworld’sGrossDomesticProduct(GDP).Thepictureisclear,asmorevehiclesareaddedtotheworld’sroadways,thesituationcanonlygetworseunlessthetechnologyimprovesdramatically.Forthistohappen,theadoptionofwirelesscommunicationtechnologytosupportcomputer-basedinter-carcommunicationprotocolsisrequired.Thevisionisanintelligenttransportationsystemcomposedofsmartvehiclesexchangingdata.Thisexchangeofdataenablesthesevehiclestoexecuteapplicationsforsafedriving,trafficconditionmonitoring,dynamicrouteplanning,e-commerce,etc.TherecentlyadoptedDedicatedShort-RangeCommunication(DSRC)spectrumforvehicle-to-vehicleandvehicle-to-infrastructuremulti-channelcommunicationisanindicationoftheincreasinginterestandexpectationsfromthisemergingtechnology.Atfirstglance,theresearchcommunityseemstohavealreadyaccumulatedthenecessaryresultstosolvethischallenge.TheAdhocnetworkingresearchcommunityfinallyappearstohavealongawaitedkillerapplicationdomain,towhichanimpressivebodyofworkcanbedirectlyapplied.Therearealsosignificantresultsinotherareassuchashuman-computerinteraction,security,andcomputervisionthatseemrelevant1Yellowbrakelightswereintroducedin1915;Thereverselightwasinventedin1921andmandatedonlyinthe1960s;Buickintroducedthefirstelectricturnsignalsin1938;thirdbrakelightwasinventedin1974andmandatedin1986)1inthiscase.Ifindeedthisisthecase,whatholdsuprapidtechnologicaladvancestowardthedesirednewgenerationofvehicles?Webelievethattheanswerismulti-dimensional:social,legal,psychological,butultimatelytechnical.Thereisstillanimmenseengineeringgapbetweentheresearchstudiesandtheirimplementation.Wirelesscommunicationisubiquitousyetextremelyunreliable,withseriousbottlenecks,predisposedtocongestion,causingnon-negligibledelaysandconnectionfailures.Node/carheterogeneity,shortyetrealtimecar-to-carinteractions,trustandprivacyareadditionalproblemswhichseriouslyconflictwiththestrongguaranteesexpectedbythemanufacturersandthedrivers;consequently,theymakeadoptionofthistechnologymorecomplicated.Vehicularcomputingandnetworkingisanareathatbenefitsfromallofthesepre-existentresearchfields,butitismuchmorethanasimplisticintegrationoftheirresults.Inthispaper,wedescribeourvisionofainter-vehicularnetworkingsystemfocussedoncar-to-carcommunication.Wepointoutthekeychallengesandobstaclesthatstandinthewayofvehicularcomputingbecomingareality.Inparticular,wepresentthedesignofanetworkprotocolstackconsistingofseveralnew,vehicle-specificlayerssuchas(i)DataValidationandCaching,(ii)StoreandForwardMessageRouting,(iii)In-NetworkProcessing,and(iv)aLocation-awarePublish-Subscribeframework,whichusesGPRS/3Glinkstoefficientlyroutehigh-prioritymessagesbetweendisconnectedad-hocnetworks.Thedesigndecisionsinthispaperarebasedonourexperiencewithreal-lifeexperimentsoverTrafficView[32,13],whichisasimplesystemfortrafficdatadisseminationandvisualizationoverwirelessadhocnetworks.Restofthepaperisorganizedasfollows.WediscussrelatedworkinSection2.InSection3wepresentthedesignofahybridvehicularnetworkarchitecture.Section4describesaprototypeimplementationofthenetworkstackthatiscurrentlyunderway.WedrawpreliminaryconclusionsinSection5.2RelatedWorkSeveralmajorautomobilemanufactureshavealreadybeguntoinvestigateinter-vehicularnetworks:GMresearchcenterinCMU[1],BMWResearchLabs[11],andFordResearchLabs[30].InEurope,alargeconsortiumofcarmanufacturersanduniversitieshavereceivedsignificantres