Research, Engineering and Design North America Inc.

A Company of the DaimlerChrysler Group

DaimlerChrysler REDNA, Inc.Palo Alto, California

Challenges and Opportunities for Multi-hop in VANET

Daniel Jiang

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What is a hop?

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Disk Model

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Multi-hop through whom?

By default, a car’s DSRC radio stays in the control channel to exchange safety messages with neighbors

Danger? X

And usually is not present in a services channel to forward general purpose data packets for others

In other words, data traffics not related to safety or mobility applications may be challenged to find a “net” to use multi-hop protocols on

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Multi-hop to whom?

Multi-hop to a fixed infrastructure point and back (i.e. extending the coverage of a Road Side Unit) is relatively easy within a very low count (e.g. 1 or 2) of hops It not unreasonable to expect a number of nodes to be already present in the channel and

coverage of the RSU to act as the forwarder Discovery and maintenance of the routes is localized and straightforward

End to end multi-hop between two cars is more problematic, Who will be in the middle to forward? Which application would demand such end to end networking, especially for more than a

few hops in distance? In other words, why would my car want to communicate with another particular car two

miles away, if it is not my wife’s car? And if the destination is my wife’s car, then the relevant address should be her cell

phone number Then why should multi-hop be used if the addressing scheme naturally point to the

other method?

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Multi-hop to whom? Cont.

Multi-hop to geo-location for safety and mobility message delivery should be expected in VANET E.g. accident/hazard warning to up stream vehicle traffic Likely implemented as an upper layer (i.e. above network

layer) protocol or even an application Geo-location in VANET => knowledge and usage of digital

map data Intermediate nodes may need to understand the content to

decide if it is going to forward or not Application understands persistence of messages better

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For Further Information

Daniel Jiang

DaimlerChrysler Research, Engineering and Design North America, Inc.Group Research and Advanced EngineeringInfotainment and Telematics (GR/ETP)

1510 Page Mill RoadPalo Alto, CA 94304USA

Phone: +1-650-845-2548Fax: +1-650-845-2555 E-Mail: daniel.jiang@DaimlerChrysler.com