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Vehicular Communication Technology. Motivation. Safety and transport efficiency In Europe around 40 , 000 people die and more than 1.5 millions are injured every year on the roads Traffic jams generate a tremendous waste of time and of fuel

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vehicular communication technology

Vehicular Communication Technology

Vehicular Communication Technology

motivation
Motivation
  • Safetyandtransportefficiency
    • InEuropearound 40,000 peopledieandmore than 1.5 millionsare injuredeveryyearontheroads
    • Trafficjamsgenerate a tremendouswasteoftimeandoffuel
  • Mostoftheseproblemscanbesolvedbyprovidingappropriateinformationtothedriverortothevehicle

Vehicular Communication Technology

vehicle communication vc
VehicleCommunication (VC)
  • VC promisessaferroads,
  • … more efficient driving,

Vehicular Communication Technology

vehicle communication vc4
VehicleCommunication (VC)
  • … more fun,
  • … and easier maintenance.

Vehicular Communication Technology

smart vehicle
Smart Vehicle

Vehicular Communication Technology

approaches to vehicular communication
Approaches to vehicular communication

Communication using Communication using

dedicated infrastructures cellular systems

Direct Communication

Vehicular Communication Technology

vehicular ad hoc network vanet
Vehicular Ad Hoc Network (VANET)
  • Ad-Hoc Network:
    • A networkwithminimalornoinfrastructure
    • Self-organizing
    • Eachnodecanactasthesourceofdata, the destinationfordataandanetwork router
  • VehicularAdHocnetwork (VANET)
    • Usesequippedvehiclesasthenetworknodes
    • Nodesmoveatwillrelativetoeachotherbut withintheconstraintsoftheroadinfrastructure

Vehicular Communication Technology

differences vanets from manets
Differences VANETs from MANETs
  • RapidTopologyChanges
    • Highrelativespeedofvehicles => short link life
  • FrequentFragmentation
    • Chunks of the net are unable to reach nodes in nearby regions
  • SmallEffectiveNetworkDiameter
    • Apathmaycease toexistalmostasquicklyasitwasdiscovered (reactive routing)
  • LimitedRedundancy
    • The redundancy in MANETs is critical to providing additional bandwidth
    • In VANETs the redundancy is limited both in time and in function

Vehicular Communication Technology

vehicular ad hoc network vanet9
Vehicular Ad Hoc Network (VANET)
  • Messagepropagatestodestinationusing a numberofintermediatelinks

Vehicular Communication Technology

vehicular ad hoc network vanet10
Vehicular Ad Hoc Network (VANET)
  • If vehicle mobility causes links to break, message rerouted using a different path

Vehicular Communication Technology

why use vanets
Why use VANETS?
  • Easierdeployment
    • Decreased dependency on fixed infrastructure
  • Sparsenetworkofroadsidebeacons
  • Permitgradualintroductionoftechnology
  • Location-orientedservicescanbeprovidedwithlittleor norunningcoststotheusers

Vehicular Communication Technology

lot of involved parties
Lot of Involved Parties

Vehicular Communication Technology

major problems in this area
Major problems in this area
  • Communication / Networking
  • Localization

Vehicular Communication Technology

requirements on vehicular communication
Requirements on vehicular communication
  • Mobility
  • Delaybounded (real-time)
  • Scalability
  • Bandwidth efficiency
  • Cost
  • Fairness
  • Any time, any place, any hosts (GPS unequipped vehicles, standardization between cars’ manufactures)

Vehicular Communication Technology

addressing the challenges
Addressing the challenges
  • PhysicalLayer
    • limited bandwidth
  • Link Layer
    • congestioncontrol, latency, throughput, fairness andscalability
  • Network (Routing) Layer
    • rapidtopology changesandnetwork fragmentation

Vehicular Communication Technology

dedicated short range communications dsrc
Dedicated ShortRangeCommunications(DSRC)
  • DSRC operates at 5.9 GHz

Vehicular Communication Technology

dsrc operating characteristics
DSRC – Operating Characteristics
  • IEEE 802.11p protocol (802.11a modification for VC)
  • Maximumrange: 1000m
  • Vehicle speeds up to 100 mph
  • Low latency: 50 ms
  • Application priority: 8 levels
  • Channel 172: vehicle safety only

Vehicular Communication Technology

how does dsrc work
Howdoes DSRC work?
  • Road-Side Unit (RSU)
    • Announces to OBUs 10 times per second applicationsitsupportson whichchannel
  • On-Board Unit (OBU)
    • Listenson Channel 172
    • Executessafetyapplicationsfirst
    • Then switches channels
    • Executes non-safety applications
    • Returns to Channel 172 and listens

Vehicular Communication Technology

channel allocation mac
Channel allocation (MAC)
  • Existing MAC protocols (CSMA/CA, MACA, MACA-BI) are contention-based => not delay bounded
  • Proposed MCS/CDMA
    • Each vehicle senses all the spreading codes, finds a code that is not used by nearby vehicles, and transmits data using the selected code
    • Search for free code, contention for free code (if vehicles > codes) => large delays

Vehicular Communication Technology

channel allocation mac20
Channel allocation (MAC)
  • Location-based Channel Access (LCA)
    • The geographical area is divided into a cellular structure
    • Each cell has a unique channel associated with it
    • Multiple access scheme, such as CSMA/CA and MCS/CDMA, can be used within each cell
    • Maindesignparameters: cellsizeandchannelreuse distance
    • Advantages: no central station for channel assignment, no wait before transmit, no contention for free channels, reuse of channels => delay bounded, fairness, bandwidth efficiency, scalability and mobility

Vehicular Communication Technology

routing schemes
Routing Schemes
  • Proactive (table-driven)
    • Eachnodeattempts tomaintainacurrent representationofthenetworktopology
    • Advantage: lowermessagelatency (routes are immediately available)
    • Disadvantage: bandwidth overhead (to maintain routes), restricted scalability
  • Reactive (source-driven, on-demand)
    • Routesarerequestedbysourcenodesonlywhen needed
    • Advantage: bandwidth economy (no control messages for non-active routes)
    • Disadvantage: latency (establishing a route)
  • Hybrid
    • ZRP – proactive within zone, reactive outside zone

Vehicular Communication Technology

major problems in this area22
Major problems in this area
  • Communication / Networking
  • Localization

Vehicular Communication Technology

slide23
GPS

Vehicular Communication Technology

space segment
Space Segment

Vehicular Communication Technology

how does gps work
How does GPS work?

Vehicular Communication Technology

how do we compute position
How do we compute Position?
  • GPS is a Distance (Range) Measuring System
  • Stable Frequency Standards in the Satellites and Receivers
  • Able to compute a Clock Offset
  • Velocity of Radiowave is known
  • Thus Distance = V x T
  • Since the coordinates of the Satellites are known at any point of time, with 4 ranges the position of the GPS Antenna can be computed
  • 3-D Trilateration: Distance, Distance, Distance and Distance Intersection

Vehicular Communication Technology

slide27
DGPS
  • Differential GPS can improve accuracy from several meters to a fewcentimeters

Vehicular Communication Technology

however
However…
  • Vehicles may be unequipped with GPS or sometimes cannot obtain line-of-sight access to satellites (in tunnels)
  • In order to discover their position (or at least driving direction), GPS-U vehicles can use communication with GPS-E vehicles
    • GPS-U periodically broadcasts PREQ message to its one-hop neighbors
    • When GPS-E receives PREQ, it sends back PREP message including its current position
    • The knowledge of the exact position depends on the number of neighbors sending PREP messages
    • GPS-U can compute its exact position if it receives at least three PREP from three different vehicles (by triangulation)

Vehicular Communication Technology

thank you
Thank You!

Vehicular Communication Technology