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 (GPSR)
Connection-Aware Routing (CAR)
Simulation
Conclusion

3. Introduction
Vehicular ad hoc networks (VANETs) using 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

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 address these kind of problems

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

6. Greedy Perimeter Stateless Routing

7. Greedy Perimeter Stateless Routing
Perimeter Mode

8. Greedy Perimeter Stateless Routing

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

10. 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

11. Destination location discovery
A source broadcast a path discovery (PD)
Each node forwarding the PD updates some entries of PD packets
If two velocity vectors’angle > 18°, anchor is set.

12. Greedy forwarding over the anchored path
A neighbor that is closer to the next anchor point is chosen (greedy) , instead of destination.

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

14. Path maintenance
If end node changes direction against the direction of communication, traveling guard will be activated.
A traveling guard runs as end node’s old direction and speed, and reroute the packets to the destination.

15. Path maintenance

16. Routing error recovery
The reason for routing error
A temporary gap between vehicles
(1) Timeout algorithm
When a node detects a gap – buffer the packets
(2) Walk-around error recovery
When Timeout algorithm fail , do location discovery
Whether the location discovery is successful, the result will be reported to the source node.

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

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

19. Simulation- Packet Delivery Ratio

20. Simulation- Average data packet delay

21. Simulation- Routing overhead

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

23. Conclusion Address the populated problem about paths.
Path discovery & Anchor points
Path maintenance with guards
Error recovery
Higher performance and lower routing overhead than GPSR