VADD: Vehicle-Assisted Data Delivery in Vehicular Ad-hoc Networks

All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
of 21

Please download to get full document.

View again

VADD: Vehicle-Assisted Data Delivery in Vehicular Ad-hoc Networks. Jing Zhao Guohong Cao The Pennsylvania State University. The Big Picture. Vehicular ad hoc networks - VANET Moving vehicles Stationary sites Local broadcasting infostations Sensors Hotspots Task
VADD:Vehicle-Assisted Data Delivery in Vehicular Ad-hoc NetworksJing ZhaoGuohong CaoThe Pennsylvania State UniversityThe Big Picture
  • Vehicular ad hoc networks - VANET
  • Moving vehicles
  • Stationary sites
  • Local broadcasting infostations
  • Sensors
  • Hotspots
  • Task
  • Delivery a message from mobile vehicle to the fixed site besides street miles away.
  • For delay tolerant applications (DTN)
  • Multi-hop forwarding through VANET
  • Challenges
  • Partitions
  • Large scale sparse networks
  • Uneven vehicle distribution
  • High mobility
  • End-to-end connection through multi-hop hard to set up
  • Most current Ad hoc routing protocols implicitly rely on the existence of end-to-end connectivity; otherwise, drop packets.
  • DSR
  • AODV
  • DSDV
  • Store, Carry and Forward
  • Mobility creates opportunities
  • Buffer and carry the packet when no routes
  • Forward the packet to the nodes moves into the vicinity which can help packet delivery
  • Possible to deliver the packet without an end-to-end connection
  • Current “Store, Carry and Forward” protocols
  • No control on mobility - Epidemic packet exchange
  • A. Vahdat and D. Becker, “Epidemic Routing for Partially Connected Ad Hoc Networks”.
  • J. Davis, A. Fagg and B. Levine, “Wearable Computers As Packet Transport Mechanisms In Highly-partitioned Ad-hoc Networks”
  • Controlled mobility
  • W. Zhao, M. Ammar and E. Zegura, "A Message Ferrying Approach for Data Delivery in Sparse Mobile Ad Hoc Networks”, ACM MobiHoc 04’.
  • Vehicle-Assisted Data Delivery (VADD)
  • Approach
  • Adopt the idea of “carry and forward”
  • Use predictable traffic pattern and vehicle mobility to assist efficient data delivery
  • Objective
  • Delivery ratio
  • Delay
  • Network traffic
  • Assumptions
  • A vehicle knows its own location via GPS, knows its neighbors’ location by beacon message.
  • Vehicles are equipped with pre-loaded digital maps
  • Road information and traffic statistics available
  • VADD
  • Key issue
  • Select a forwarding path with smallest packet delivery delay
  • Why not GPSR?
  • Guidelines
  • Transmit through wireless channel
  • as much as possible
  • Forward the packet via high density
  • area
  • Use intersection as an opportunity to switch the forwarding direction and optimize the forwarding path
  • Geographically shortest pathFast speed wireless communicationVADD: Three Modes
  • Intersection Mode
  • Optimize the packet forwarding direction
  • StraightWay Mode
  • Geographically greedy forwarding towards next target intersection
  • Destination Mode
  • broadcast packet to destination
  • VADD: Intersection Mode
  • Problem
  • Which direction to go?
  • VADD Model
  • Which carrier to take?
  • VADD Protocols
  • Carrier: The node who can forward the packet as the next hopVADD Model
  • Find out the next forwarding direction with probabilisticallythe shortest delay
  • Probabilistic Method
  • Estimate the expected delivery delay from current intersectionto the destination for each possible forwarding directions
  • Compute The Optimal Forwarding Direction
  • Computation Steps
  • 1. Place a boundary including source and destination 2. Derive a linear equation for each intersection within the boundary usingEquation (1). 3. Generate a Linear equation system
  • Can be proved to have unique solution
  • 4. Solve the equation systems by Gaussian Elimination
  • Complexity is
  • Output: Priority list of the outgoing directions for the packet forwardingIntersection Forwarding Protocol
  • Known the priority list of outgoing directions, check the available carriers to ensure packet is forwarded to the preferred directions
  • Not trivial, need to consider
  • Location
  • Mobility
  • VADD Intersection Protocols
  • Location First VADD (L-VADD)
  • Direction First VADD (D-VADD)
  • Multi-Path D-VADD (M-VADD)
  • Hybrid VADD (H-VADD)
  • Use Priority 2Use Priority 1Location First VADD (L-VADD)
  • Simple L-VADD
  • The closest carrier towards the preferred direction in term of location as the next hop, whatever the moving direction of the chosen carrier.
  • e.g. AB
  • Vulnerable to Forwarding Loop
  • Loop-free L-VADD
  • Detection: Check previous hop
  • Recovery: Mark suspect node
  • Drawback
  • Due to mobility, a lot of loops can be self-released with node still marked. Thus many valid carrier cannot be used
  • Drawback
  • Negative on delivery ratio
  • Direction First VADD (D-VADD)
  • Basic Idea
  • Only probe the carrier moving towards the preferred direction.
  • Pick the one closest towards the preferred direction as the next hop.
  • e.g. AC
  • Can be proved no Forwarding Loop
  • Drawback
  • Delay may be higher
  • Multi-path D-VADD (MD-VADD)
  • Basic idea
  • Continue holds the packet after the packet is forwarded to sub-optimal direction
  • Record dsent as the moving direction
  • Extends the staying time of a packet at the intersection to increase the opportunity of meeting contact towards better direction.
  • Pros:
  • Higher delivery ratio
  • Lower delay
  • Cons:
  • Duplicated packet
  • More overhead
  • Hybrid VADD (H-VADD)
  • Basic Idea
  • Hybrid of L-VADD and D-VADD/MD-VADD
  • “Try and Error”
  • Try L-VADD first, switch to D-VADD/MD-VADD when L-VADD fails.
  • Pros:
  • Capture the advantages of both L-VADD and D-VADD.
  • Performance Evaluation
  • Packet level simulation by ns2
  • Metrics
  • Delivery ratio
  • Delay
  • Network traffic
  • Compare the performance with:
  • Epidemic Routing
  • GPSR (with buffer)
  • Mobility Scenario
  • Traffic model derived from from TIGER database
  • Map data are transformed into ns-2 readable data
  • Delivery ratio
  • Low node density VS High node density
  • 150 nodes210 nodesDelay
  • Low node density VS High node density
  • 150 nodes210 nodesNetwork Traffic
  • Comparison between different protocols
  • Conclusion
  • Existing routing protocols are not suitable for DTN applications in VANET.
  • VADD adopts the idea of “carry and forward”, and also explores the predictable vehicle mobility.
  • VADD use a linear equation model combining with probabilistic method to compute the optimal forwarding direction.
  • Four VADD protocols to forward the packet towards the optimal direction/path at the intersection.
  • Simulation results shows that the VADD protocols are better suitable for the multi-hop data delivery in VANET.
  • Thank YouJing Zhaojizhao@cse.psu.edu
    Related Search
    We Need Your Support
    Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

    Thanks to everyone for your continued support.

    No, Thanks