1

Vehicular Networks

Slides are integrated from researchers at EPFL

2

Outline

Why vehicular networks Technical challenges Conclusion

3

Outline

Why vehicular networks Technicals Applicaitions Wireless Urban Grid

Technical challenges Conclusion

4

Vehicular communications: why?

Combat the awful side-effects of road traffic Fatal losses yearly on the roads; and injured (huge

numbers) Traffic jams generate a tremendous waste of time and of fuel

Most of these problems can be solved by providing appropriate information to the driver or to the vehicle

5

A modern vehicle is a computer on wheels

F o r w a r d r a d a r

C o m p u t in g p l a t f o r m

E v e n t d a t a r e c o r d e r ( E D R )P o s i t i o n i n g s y s t e m

R e a r r a d a r

C o m m u n ic a t i o n f a c i l i t y

D i s p la y

• Processing power: comparable with a Personal Computer + a few dozens of specialized processors• Communication: typically over a dedicated channel: Dedicated Short Range Communications (DSRC)

• In the US, 75 MHz at 5.9 GHz; • In Europe, 20 MHz requested but not yet allocated)

• Protocol: IEEE 802.11p• Penetration will be progressive (over 2 decades or so)

(GPS)

- Human-Machine Interface- Navigation system

6

Example of service: electronic brake warning

Similar services: • Road condition warning• Emergency vehicle approaching

7

Other example of service: traffic information

8

Liability-related messages

• The information carried by these messages is susceptible to be stored in the Event Data Recorder of each vehicle

9

Another application : SmartPark

Turn right!50m to go…

Park!

Turn left!30m to go…

10

Other examples of services based on vehicular networks (these ones usually involve road side infrastructure)

Vehicle to road Electronic toll collection

Vehicles as probes to collect traffic data

Ramp metering to reduce congestion

Road to vehicle Signal violation warning

Intersection collision warning

Data downloads

11

Message categories and properties

Property

Category

Legitimacy

Privacy protection

Against other individuals

Against the police

Traffic information

Anonymoussafety-related

messages

Liability-related messages

Guaranteed to R, D S, R, D S, R, D

S: Source R: Relay D: Destination

Real-timecons-traints

12

Outline

Why vehicular networks Technicals Applicaitions Wireless Urban Grid (another file)

Technical challenges Conclusion

13

Outline

Why vehicular networks Technical challenges

Service penetration and connectivity Research opportunities in the vehicular networks Conclusion

14

Vehicular communications:a compelling (and tough) research challenge

High speed of the nodes (relative speed up to 500 km/h)

Real time constraints (milliseconds) Sporadic connectivity (a few seconds or less) Crucial role of the geographic position of the nodes Very gradual penetration Last but not least, a very specific security research

question

15

Penetration and connectivity

First level approximation:

16

Number of hops Vs penetration (1/2)

17

Hopping on vehicles in the reverse direction

18

Number of hops Vs penetration (2/2)

19

compute connectivity in this case

20

Performance evaluation Two scenarios drawn from DSRC ns-2 simulations; single-hop transmission Effect of message size (including the security overhead) on

delay and number of received packets

(Not to scale)

5 m

Congestion

(safety messages aresent every 100 ms)

30 m

Moving traffic

(safety messages aresent every 300 ms)

average speed is100 km/h

(Not to scale)

Rough estimate of incoming traffic:120 veh * 3.33 msg/(veh*s) * 800 Bytes/msg= approx. 3 Mb/s

Rough estimate of incoming traffic:36 veh * 10 msg/(veh*s) * 800 Bytes/msg= approx. 3 Mb/s

21

Delay Vs message size

NT

RU

No

secu

rity

EC

DSA

RSA

22

Received packets Vs message size

NT

RU

No

secu

rity

EC

DSA

RSA

23

Factors in performance evaluation of vehicular networks

Performanceevaluation

• Nature of data traffic (e.g., single hop, geocast)• Available spectrum (e.g., 75 MHz or 20MHz around 5.9 GHz)• Radio propagation model in vehicular environment• Kind of antenna (directional or not)• Number of radios• Penetration rate (e.g., parameter from 5% to 100%)• Considered crypto algorithm

• Vehicle mobility models• Road topology• Amount of roadside infrastructure (e.g., none)

• Connectivity •Goodput• Delay• Delay jitter• Fairness

Examples of design questions:-Is CSMA/CA really the best solution?- To what extent can geographic position be taken into account for routing?

Powercontrol

24

Conclusion

The performance of vehicular communications is a difficult and highly relevant problem

Car manufacturers seem to be poised to massively invest in this area

Slow penetration makes connectivity more difficult Security leads to a substantial overhead and must be

taken into account from the beginning of the design process

The field offers plenty of novel research challenges

M. Raya and J.-P. Hubaux, “The Security of Vehicular Ad Hoc Networks”, Workshop on Secure Ad Hoc and Sensor Networks (SASN) 2005

25

Events and resources

Conferences and journals VANET, colocated with Mobicom V2V-Com, co-located with Mobiquitous WIT: Workshop on Intelligent Transportation VTC: Vehicular Technology Conference IV: Conference on Intelligent Vehicles IEEE Transactions on Intelligent Transportation Systems IEEE Transactions on Vehicular Technology