DSRC VANET Research Proposal

18-843: Mobile Computing Systems & Applications

Section A: Executive Summary

Thepurposeofthisproposalistobringtoattentionthephysicallayerissues,challenges,and

research opportunities relatedto theuseof theDedicatedShort RangeCommunications(DSRC)

systeminthevariouswirelesscommunicationsapplicationsofvehicularadhocnetworks

(VANETs).The AntennaandRadioCommunicationsGroupinCarnegieMellonUniversity’s

DepartmentofElectricalandComputerEngineeringcurrentlyhasfullyfunctionalproofof

concept VANET of five vehicles;

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however, very little has been done to evaluate the performance

These different applications have different throughput and quality of service requirements and the

quality of the DSRC VANET communications channel must be evaluated to determine whether or

not it is suitable for each application.

TherearethreeprimaryareaswhichmuchberesearchedanddocumentedbeforeDSRCcanbe

commerciallydeployedforanyoftheseapplications.First,there areseveraldifferent

environmentsinwhichavehiclemaytravelandthenetworkmustmeetthevariousminimum

performancethresholdsofeachapplicationineverysituation.Second,thereisatradeoff

between transmitting many small packets with a relatively large overhead vs. fewer large packets

with a relatively small overhead and we must determine the packet size which optimizes network

performance. Finally, there are several possible rates at which the data can be transmitted and we

Section B: Overview of DSRC

TheDedicatedShortRangeCommunications(DSRC)systemisageneralpurposeshortto

medium range RF communications link that supports both public safety and private operations in

roadsidetovehicleandvehicletovehiclecommunicationenvironmentsutilizingtheIEEE

802.11pprotocol.DSRC is meanttobeacomplementtocellularcommunicationsby providing

veryhighdatatransferratesincircumstanceswhereminimizinglatencyinthecommunication

link and isolating relatively small communication zones are important.

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The 802.11a protocol, which is only months old, improves on the range and speed of transmission

on the dedicated 5.85 – 5.925 GHzlicensed band, promising a transmission range of about 1,000

DSRC VANET Research Proposal

18-843: Mobile Computing Systems & Applications

With theincreasing popularityofwireless communications technologiesandtheirrapid

expansion into most other technology sectors, the automotive industry is actively seeking ways to

use wireless communicationsto create acompetitiveadvantage inthemarketplace. Researchers

haveidentifiedthreemajorcategoriesofapplicationswhichwillincreaseconsumerdemandfor

the automobiles with wireless technology – increased safety, driver information, and multi-media

distribution.Thesedifferentapplicationseachhavedifferentthroughputandqualityofservice

each application is unknown. This raises the following research questions about DSRC VANETs:

The primary goal of our research effort will be to determine whether or not DSRC VANETs are

suitable for safety, driver information, and multi-media applications in vehicles.

The first major step toward achieving this goal will be to determine the effects of different driving

environmentsonthesignalpropagationwithinthewirelesscommunicationschannel.Wewill

linksaredirectly relatedtotheenvironment in whichthelinkisformed andwecannotestablish

the usefulness of DSRC VANETs if we cannot demonstrate that they meet minimum performance

requirements in ALL environments.

DSRC VANET Research Proposal

18-843: Mobile Computing Systems & Applications

Thesecondmajorsteptowardachievingourprimarygoalwillbetodeterminetheeffectsof

packetsizeontheoverallperformanceofthewirelessnetwork.Ingeneral,thereisatradeoff

between transmitting many small packets with a relatively large overhead vs. fewer large packets

witha relativelysmalloverhead.Thenetwork’sabilitytotolerateandcorrecterrors isdirectly

relatedtotheamountofdatathatislost and theeasewithwhichitcanberetransmitted. If one

largepacketislost,theeffectismuchmoredetrimentalthanitwouldbeifonesmallpacketis

lost. On the other hand, the size of the packet header is independent of the size of the packet. As

rate on the overall performance of the wireless network. There are several possible rates at which

thedatacanbetransmitted;however,increasesindataratetypicallyresultinadecreaseinthe

effectiverangeofthetransmissionswithinthenetworkandthesignalbecomesmuchmore

vulnerabletodispersion,multi-patheffects,fading,andotherwirelesscommunicationschannel

effects.Wemustdetermine the dataratewhichoptimizesdatathroughput inthenetworkwhile

meeting minimum performance requirements in sub-optimal environments.

Afterachievingeachofthesegoals,willprovideourresearchsponsorswiththedetailsofour

findings and suggest a future course of action based on those findings.

thethreeprimaryresearchareas.Theexecutionofthisresearchstrategyiscontingentonthree

urbanenvironments.RecentdatacollectioneffortsdemonstratethatGPStechnologyisnota

sufficient means of making reliable location measurements in urban environments due to satellite

signal blockages, multi-path signal reflections, and other factors which limit its ability to maintain

a consistent communications link with enough satellites.

The second major effort will be to conduct the numerous data collection drives required to collect

enoughdatatothoroughlyevaluateeachpossiblecombinationofdrivingenvironment,packet

size,anddatarate.Ourinitialemphasiswillbeondataratesof3,6,and24Mbpsandpacket

sizes of 50, 100, and 250 bytes in each of the three environments. We estimate that twenty hours

DSRC VANET Research Proposal

18-843: Mobile Computing Systems & Applications

ofdrivingineachscenariooughttobesufficienttomakeawell-substantiateddeterminationof

networkperformance.Theactualdatacollectionstrategyisfairlysimple–beginwithone

combination(i.e.adatarateof3Mbpsandapacketsizeof50bytesinaruralenvironment)

rotate through the various combinations until all have been accounted for.

Thethird andfinalmajoreffort willbeto analyzethe data,evaluatethe network performancein

eachofthescenarios,andmakeafinaldeterminationofwhetherornotDSRCVANETsare

possible applications and the minimum performance levels of the empirical network data for ALL

Section F: Research Metrics

onhisownandthesafetyapplicationwillaccomplishnothing.Currentsystemdesigns

callfor redundancy insafetymessages,so a linkisconsideredto bedependableifithas

an overall bit error rate of 0.005 or less. The average human reaction time is estimated to

beabout500msec,sototalsystemlatenciesof less than250msecareconsidered small

enough that the application will benefit the driver.

The primary limitingfactor for multi-mediaapplications is transmissionbandwidth. The

applicationwiththe greatestbandwidthdemandsatthispointis videoconferencing,and

depending on the type of application used, video conferencing requires a bandwidth of at

least32kbps.Voiceapplicationsanddriverinformationapplicationsfitsomewhere

between the two extremes.

performance as described above.

DSRC VANET Research Proposal

18-843: Mobile Computing Systems & Applications

Section G: Required Resources

Thesuccessfulcompletionofthisresearchprojectwillrequirehardware,software,and

manpower.Wewillrequireaminimumoffivevehicles,completewithVANET

communicationstestkits,toevaluatethenetwork.Muchofthesoftwarethatwillbe

required can be developed by the research group; however, we anticipate some expense in

purchasingadditionalsoftwareandlicenses.Inaddition,wewillrequireatleastone

universityfacultyadvisor,twoPhDprogramstudents,twoMasterofScienceprogram

students, and four technical staff to maintain and drive the vehicles.

Section H: Future Research Opportunities

Thefocusofthisresearchproposalhasbeenonthephysicallayerissues,challenges,and

addressestheneedsofVANETsandexpandsthecapability,performance,andefficiencyofthe

network.Finally,theexpansionofwirelesscapabilitiestotheautomotiveworldcreatesagreat

opportunitytodevelopnewapplicationsthatgoaboveandbeyondthoseofthepotential

applications which motivate this research work.

Wearecertainthatourresearcheffortwillmakesignificantcontributionstotheongoingand

Section J: References