Vehicle-to-Vehicle Wireless
Communication Protocols for
Enhancing Highway Traffic Safety
A Comparative Study of Data Dissemination
Models for VANETs
Subir Biswas, Raymond Tatchikou,
Francois Dion
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Tamer Nadeem,
Pravin Shankar, Liviu Iftode
Presentation: Nick Frangiadakis
Towards the future…
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Cheap, embedded processors
Cheap, embedded, small sensors
Interconnected
Wireless
Mobile
Ubiquitous Computing
New services / applications
Towards the future…
• A number of diverse (or not) technologies:
– 802.11a/b/g/e/…, GSM, UMTS, DSRC
• A number of different problems / applications / services
– …..
• An even greater number of solutions
– Exercise for the reader…
• Each of the discussed technologies address best a
different set of proposed applications
• Survival of the best: Not always the case!
– Survival of the fittest: Already deployed or cheaper or even
supported from the largest company
But this is a systems problem!
• Not so, or better not only:
• Vast number of sensors A lot of Data
– Distributed
– Possibly Mobile
– Queries about the data
– Most applications in fact are data-centric
• Internet could also be seen as a systems
problem, but there is also e.g. Google’s
perspective
VANETS
• An application:
• Thesis:
Vehicle-to-Vehicle Wireless
Communication Protocols for
Enhancing Highway Traffic Safety
– Traffic safety is an application that we WILL
see in the near future.
– The technology used IS the one that will be
discussed.
• This means that the technology discussed
will be in place in the near future and will
probably be used for more applications
CCA: Cooperative Collision
Avoidance
• United States:
– six million traffic accidents / year
– 2003 :
• $230 billion,
• 2,889,000 injuries,
• 42,643 deaths
• 5.850 to 5.925 GHz band allocated by US
FCC
CAC: Application Examples
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Highway accidents
Automatically adjusting cruise control
Beacon for stopped cars / police
Accidents from Red light / Stop violations
In general Avoid human errors (90% of all
traffic accidents)
CCA: Cooperative Collision
Avoidance
CCA: Cooperative Collision
Avoidance
The general picture: proposed
national infrastructure
The general picture: proposed
national infrastructure
DSRC: Dedicated Short Range
Communication
• MAC:
– De facto standard: 802.11
– Stability problems (e.g. TDMA is very difficult)
• Packet Forwarding
– Time to establish connection is time lost
– MANET style not applicable (e.g. AODV does
not work)
– Broadcast oriented, data-driven, packet
forwarding based on geographic context
Context –aware packet forwarding
• Direction Aware Broadcast Forwarding
– Design targets (min Bandwidth, limit
collisions, prioritize data, …)
– What are the limits?
• Naïve Broadcast
• Intelligent Broadcast With Implicit
Acknowledgment (?)
• Others (…)
Context –aware packet forwarding:
Some numbers…
Context –aware packet forwarding:
Some numbers…
Context –aware packet forwarding:
Some numbers…
Context –aware packet forwarding:
Some numbers…
Context –aware packet forwarding:
Some numbers…
Some more Points:
• “With 80/kb/s/vehicle background traffic the
protocol can still work…”
• Broadcast, intelligent with priorities
• Problem similar to Sensor Network problems for
which there are models and bounds (e.g. The
Capacity of Wireless Networks Piyush Gupta,
P.R. Kumar, 1999 )
• Mobility – Data Driven – Priority…
(tx speed?)
A Comparative Study of Data Dissemination
Models for VANETs
Tamer Nadeem,
Pravin Shankar, Liviu Iftode
• “VANETs enable a new class of applications that require time-critical
responses (less than 50 ms) or very high data transfer rates (6-54
Mbps).”
• “The dissemination mechanism can either broadcast information to
vehicles in all directions, or perform a directed broadcast restricting
information about a vehicle to vehicles behind it.”
• TrafficView:
Traffic View
• GPS, OBD, Stored maps etc (OBD: On Board Diagnosis)
• Data aggregation, Periodically broadcast
all stored data….
• Prototype / evaluation of simulation in ns2
• Without loss of generality, we assume
vehicles move on bidirectional straight
roads with multiple lanes in each direction
Dissemination models:
Analysis
• Latency time (L) is defined as the time needed to
propagate generated data between two vehicles
positioned D meters from each other.
• Broadcast utilization (U) is defined as the
percentage of the newly covered area by the
current broadcast, which is not covered by any
previous broadcast of the same data, to the total
area covered by a broadcast.
Analysis
• Latency time (L) is defined as the time needed to
propagate generated data between two vehicles
positioned D meters from each other.
• Broadcast utilization (U) is defined as the
percentage of the newly covered area by the
current broadcast, which is not covered by any
previous broadcast of the same data, to the total
area covered by a broadcast.
Simulation
• Latency Time
• Utilization rate
• Knowledge Percentage: For each region, the
percentage of the known vehicles in a region by the
current vehicle
• Accuracy: The average error in estimating the
position of vehicles in a region
Simulation
Other points
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Flooding is not good either
Model ?
Metrics ?
Limits ?
Applications!
Hybrid Models?
Thank you
• Comments ?
• Questions ?