Vehicle-to-Vehicle Wireless Communication Protocols for Enhancing Highway Traffic Safety - A Comparative Study of Data Dissemination Models for VANETs

Vehicle-to-Vehicle WirelessCommunication Protocols for

Enhancing Highway Traffic Safety-

A Comparative Study of Data Dissemination Models for VANETs

Presentation: Nick Frangiadakis

Subir Biswas, Raymond Tatchikou, Francois Dion

-Tamer Nadeem,

Pravin Shankar, Liviu Iftode

• Cheap, embedded processors

• Cheap, embedded, small sensors

• Interconnected

• Mobile

• Ubiquitous Computing

• New services / applications

Towards the future…

Wireless

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

• An application: • Thesis:

– 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

VANETSVehicle-to-Vehicle Wireless

Communication Protocols forEnhancing Highway Traffic Safety

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

• 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)



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…





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

• Flooding is not good either

• Model ?

• Metrics ?

• Limits ?

• Applications!

• Hybrid Models?

Thank you

• Comments ?

• Questions ?

Documents

Vehicle-to-Vehicle Wireless Communication Protocols for Enhancing Highway Traffic Safety - A Comparative Study of Data Dissemination Models for VANETs