1. 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

2. 2 What is a hop?

3. 3 Multi-hop through whom? By default, a cars 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

4. 4 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 wifes car? And if the destination is my wifes 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?

5. 5 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

6. 6 For Further Information Daniel Jiang DaimlerChrysler Research, Engineering and Design North America, Inc. Group Research and Advanced Engineering Infotainment and Telematics (GR/ETP) 1510 Page Mill Road Palo Alto, CA 94304 USA Phone:+1-650-845-2548 Fax:+1-650-845-2555 E-Mail:daniel.jiang@DaimlerChrysler.com