Adaptive Broadcast for Travel and Traffic Information Distribution Based on Inter-Vehicle Communicat...
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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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Lars Wischhof et al. Technical University of Hamburg-Harburg, Hamburg, Germany

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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)

Self Organizing Traffic Information System (SOTIS)

How to broadcast information among cars efficiently?


  • 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?


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

  • 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 System

Inter-road segments communication (SOTIS packet)

N = 100 km/500m = 200

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


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)

  • 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)

  • 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


  • 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

  • qinfo and qdate are constants


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 ?

Increase Tupd

Decrease Tupd


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


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

  • 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)


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

No justification about

values of parameters

NS2 simulation


Cumulated Number of Dropped Packets


Required Bandwidth


Conclusion

  • Pros

    • A threshold-based adaptive broadcast protocol

    • Tune broadcast interval according to changes of SOTIS packet

  • Cons

    • Too many control parameters


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