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Connectivity-Aware Routing (CAR) in Vehicular Ad Hoc Networks

Connectivity-Aware Routing (CAR) in Vehicular Ad Hoc Networks. Valery Naumov & Thomas R. Gross ETH Zurich, Switzerland IEEE INFOCOM 2007. Outline. Introduction Related Works Connection-Aware Routing (CAR) Simulation Conclusion. Introduction.

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Connectivity-Aware Routing (CAR) in Vehicular Ad Hoc Networks

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  1. Connectivity-Aware Routing (CAR) in Vehicular Ad Hoc Networks Valery Naumov & Thomas R. Gross ETH Zurich, Switzerland IEEEINFOCOM 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 simulator’s 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 destinations’locations. • Relay nodes make a local greedy routing. • Greedy mode & Perimeter mode

  7. Related Works

  8. 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 vectors’angle > 18°, anchor is set.

  13. Connection-Aware Routing (CAR) • If two velocity vectors’angle > 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. Connection-Aware Routing (CAR) • 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)

  19. Connection-Aware Routing (CAR)

  20. Connection-Aware Routing (CAR) • 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. • End node will send a notification to source

  21. Connection-Aware Routing (CAR)

  22. Connection-Aware Routing (CAR) • 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. Conclusion • Adaptive beaconing • PGB, AGF, and velocity vectors • Anchor points • Path maintenance with guards • Error recovery • Higher performance and lower routing overhead than GPSR

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