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Challenges and Opportunities for Multi-hop in VANET. Daniel Jiang. What is a hop?. Danger?. Multi-hop through whom?. By default, a car’s DSRC radio stays in the control channel to exchange safety messages with neighbors. X.
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Challenges and Opportunities for Multi-hop in VANET Daniel Jiang
Danger? Multi-hop through whom? • By default, a car’s DSRC radio stays in the control channel to exchange safety messages with neighbors 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
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?
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
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