1. Connectivity-Aware Routing (CAR) in Vehicular Ad Hoc Networks Valery Naumov & Thomas R. Gross ETH Zurich, Switzerland IEEE INFOCOM 2007

2. Outline Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion

3. Introduction Vehicular ad hoc networks (VANETs) using 802.11-based WLAN technology have recently received considerable attention in many projects Several geographic routing (GR) protocols use an idealized mechanism such that for every originated data packet the true position of the destination is known – e.g. based on the simulators global view

4. Introduction Another problem is that, all of the GR protocols do not take into account if a path between source and destination is populated. This paper presents a novel position-based routing scheme called Connectivity-Aware Routing (CAR) to adress these kind of problems

5. Outline Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion

6. Related Works GPSR (Greedy Perimeter Stateless Routing) – A geographic routing protocol – Packets are marked with their destinationslocations. – Relay nodes make a local greedy routing. – Greedy mode & Perimeter mode

7. Related Works

9. Outline Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion

10. Connection-Aware Routing (CAR) Adaptive beaconing mechanism: – Beacon interval is changed according to the number of nearby neighbors. Beacons can be appended in the data packets.

11. Connection-Aware Routing (CAR) The CAR protocol consists of four main parts: – (1) destination location and path discovery – (2) data packet forwarding along the found path – (3) path maintenance with the help of guards – (4) error recovery

12. Connection-Aware Routing (CAR) Destination location discovery A source broadcast a path discovery (PD) Each node forwarding the PD updates some entries of PD If two velocity vectorsangle > 18°, anchor is set.

13. Connection-Aware Routing (CAR) If two velocity vectorsangle > 18°, anchor is set. – Anchor contains coordinates and velocity vector of current node and previous node.

14. Connection-Aware Routing (CAR) A route reply will send to the source with unicast Advantages – Finds the path that exist in reality – Takes connectivity into account – No try-and-error route test – Only source-destination pairs keep anchor path to each other

15. Connection-Aware Routing (CAR) Greedy forwarding over the anchored path – A neighbor that is closer to the next anchor point is chosen, instead of destination.

16. Connection-Aware Routing (CAR)

17. Path maintenance If an end node (source or destination) changes position or direction, standing guard will be activated to maintain the path.

18. Connection-Aware Routing (CAR)

20. Path maintenance If end node changes direction against the direction of communication, traveling guard will be activated. – A traveling guard runs as end nodes old direction and speed, and reroute the packets to the destination. – End node will send a notification to source

21. Connection-Aware Routing (CAR)

22. Routing error recovery The reason for routing error – A temporary gap between vehicles – Long-term disconnection a suddenly closed road or big gap in traffic. – The destination could not activate a guard due to lack of neighbors. Timeout algorithm with active waiting cycle Walk-around error recovery

23. Connection-Aware Routing (CAR) Timeout algorithm When a node detects a gap – It tells other nodes and starts buffering packets. – It tries to detest a next hop node, sends requests. A node receives the request will reply with a HELLO beacon.

24. Connection-Aware Routing (CAR) Walk-around error recovery When fail to find the destination at its estimate position When Timeout algorithm fail – Start a location discovery

25. Connection-Aware Routing (CAR) If location discovery is unsuccessful – Source starts a new path discovery. If successful, the new path will send to source – Source analyzes the new path and current position, Start a new path discovery if the source is closer then the node to the destination.

26. Outline Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion

27. Simulation Scenarios – City – Highway Traffic density – Low – less than 15 vehicles/km – Medium – 30-40 vehicles/km – High – more then 50 vehicles/km

28. Simulation- Packet Delivery Ratio

29. Simulation- Average data packet delay

30. Simulation- Routing overhead

31. Outline Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion

32. Adaptive beaconing PGB, AGF, and velocity vectors Anchor points Path maintenance with guards Error recovery Higher performance and lower routing overhead than GPSR