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Adaptive Broadcast for Travel and Traffic Information Distribution Based on Inter-Vehicle Communication. Lars Wischhof et al. Technical University of Hamburg-Harburg, Hamburg, Germany. Presented by Long Vu CS598JH – Fall 07. Traffic and Travel Information System (TTI).

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slide1

Adaptive Broadcast for Travel and Traffic Information Distribution Based on Inter-Vehicle Communication

Lars Wischhof et al.

Technical University of Hamburg-Harburg, Hamburg, Germany

Presented by Long Vu

CS598JH – Fall 07

traffic and travel information system tti
Traffic and Travel Information System (TTI)

Self Organizing Traffic Information System (SOTIS)

How to broadcast information among cars efficiently?

slide3
Challenges
    • Mobile nodes
    • Node density is not uniform
      • Highway vs. traffic jam
  • Possible solutions
    • Periodically broadcast with fixed broadcast interval
    • Adaptively tune broadcast interval

How to broadcast information among cars efficiently?

slide4
Next…
  • Self-Organizing Traffic Information System
  • Provoked Broadcast
    • Provoked Broadcast
    • Provocation vs.Mollification
    • Influence of Distance on Provoked Broadcast
  • Simulation
    • Settings
    • Cumulated number of dropped packets
    • Required Bandwidth
  • Conclusion
self organizing traffic information system
Self-Organizing Traffic Information System
  • All nodes in a segment broadcast their velocities to all other nodes in the same segment  all nodes can compute average velocity and put into TTI record of this segment
  • Transmission range: 1000m
  • Fixed broadcast interval: 5 seconds

No Segment

Leader

Intra-road segment communication

self organizing traffic information system1
Self-Organizing Traffic Information System

Inter-road segments communication (SOTIS packet)

N = 100 km/500m = 200

Each record is the average velocity of cars in the corresponding segment

slide7
Next…
  • Self-Organizing Traffic Information System
  • Provoked Broadcast
    • Provoked Broadcast
    • Provocation vs.Mollification
    • Influence of Distance on Provoked Broadcast
  • Simulation
    • Settings
    • Cumulated number of dropped packets
    • Required Bandwidth
  • Conclusion
provoked broadcast 1
Provoked Broadcast (1)
  • Step 1: Each car broadcast its velocity to its neighbors in the same road segment  avg. velocity is computed
  • Step 2: Cars update TTI for this road segment. Put it into SOTIS packet
    • A TTI record has averagevelocity and time stamp
  • Step 3: Car broadcasts the SOTIS packet to neighboring road segments
provoked broadcast 2
Provoked Broadcast (2)
  • Step 4: Upon receiving SOTIS packet, car updates TTI records in its memory (knowledge base)
  • Step 5: Depending on the difference between received SOTIS packet and its knowledge base, car performs provocation or mollification on broadcast interval
slide10
Compare received SOTIS packet to car’s knowledge base:
    • Provocation
    • Mollification

vi- vi’

ti- ti’

Car’s Knowledge base

Received SOTIS packet

s distinct overlapped road segments
S Distinct Overlapped Road Segments
  • qinfo and qdate are constants
provocation vs mollification
Provocation vs. Mollification
  • If wm,n < wmol T = T + tmol
  • If wm,n > wprov T = T - tprov

Too many constants and parameters !

how it actually works
How it Actually Works ?

Increase Tupd

Decrease Tupd

interdependence of provocation and mollification
Interdependence of Provocation and Mollification
  • M close nodes (in trans. range)
  • Have a similar view of network
  • N broadcasts new information
  • All nodes provoke
  • Nodes are unsynchronized
  • A broadcasts, other nodes perform mollification
slide15
Next…
  • Self-Organizing Traffic Information System
  • Provoked Broadcast
    • Provoked Broadcast
    • Provocation vs.Mollification
    • Influence of Distance on Provoked Broadcast
  • Simulation
    • Settings
    • Cumulated number of dropped packets
    • Required Bandwidth
  • Conclusion
influence of distance on provoked broadcast
Influence of Distance on Provoked Broadcast
  • The farthest node in the broadcast range should broadcast next to utilize bandwidth

dtx,max: the max trans. range

If wm,n > wprov T = T – qdist(dtx)

slide17
Next…
  • Self-Organizing Traffic Information System
  • Provoked Broadcast
    • Provoked Broadcast
    • Provocation vs.Mollification
    • Influence of Distance on Provoked Broadcast
  • Simulation
    • Settings
    • Cumulated number of dropped packets
    • Required Bandwidth
  • Conclusion
simulation settings
Simulation Settings

No justification about

values of parameters

NS2 simulation

conclusion
Conclusion
  • Pros
    • A threshold-based adaptive broadcast protocol
    • Tune broadcast interval according to changes of SOTIS packet
  • Cons
    • Too many control parameters