A Cross Layered MAC and Clustering Scheme for Efficient Broadcast in VANETs

1. A Cross Layered MAC and Clustering Scheme for Efficient Broadcast inVANETs Luciano Bononi, Marco Di Felice Department of Computer Science, University of Bologna IEEE MASS 2007

2. Outline • Introduction • System Model and Assumptions • Cross-layered Protocol Scheme • Backbone Creation and Maintenance • MAC Layer Support • Performance evaluation • Conclusion

3. Introduction

4. Introduction • RVC (Road-vehicle Communication)

5. Introduction • IVC (Inter-vehicle Communication)

6. C B Introduction • Road-network coverage by wireless communication infrastructures is costly. • Road-safety applications based on IVC strictly rely on the assumption of • Cooperation among vehicles • Distributed coordination among vehicles A

7. Introduction - Goal • Design an algorithm for efficient broadcast of alert messages in VANETs. • Overhead reduction • Reliability

8. System Model and Assumptions • In a multi-lane highway scenario • Vehicles travelling in both directions • Vehicles to be equipped with • Sensing capability • Wireless communication • Computation capability • Storage capability • GPS

9. Backbone Backbone Member (BM) State Normal Vehicle (NV) State

10. Backbone

11. Backbone • Each chain member has at most two neighbors A B C Message Message prev_hop next_hop Direction

12. Backbone Creation Process A B Direction D C BEACON message： <ID, (x,y), R, speed, dir, horizon>

13. B A Residual Time (RT) • Assume Vehicle A is following Vehicle B • R：the transmission range of the sender vehicle • Δv = vB - vAis the relative speed between nodes B and A • dist(A,B)：the current estimated distance , if Δv > 0 , otherwise

14. B A Residual Time (RT) = 1 R Direction dist(A, B)

15. B A Residual Time (RT) = -1 Direction dist(A, B)

16. Backbone Creation Process Vehicle ID：B Backbone State：NV Time Residual：2 sec A B Direction D C Vehicle ID：C Backbone State：NV Time Residual：5 sec Vehicle ID：D Backbone State：NV Time Residual：4 sec

17. B A Fit Factor (FF) Backbone Refresh Interval Direction dist(A, B)

18. Backbone Creation Process A B Direction D C Vehicle ID：D Backbone State：NV Time Residual：4 sec Fit：0.4 Vehicle ID：C Backbone State：NV Time Residual：5 sec Fit：0.9 Vehicle C sends a CANDIDATURE message to Vehicle A Vehicle A sends an ACK_WINNER message to Vehicle C

19. A Backbone Creation Process Direction B VehicleA replies immediatelywith aCANDIDATURE message to VehicleB Vehicle B sends an ACK_WINNER message to Vehicle A Vehicle A receives a BEACON message from Vehicle B

20. Fast Multi-Hop Forwarding (FMF) ACK ACK Direction

21. Basic MAC Scheme A ACK B Direction

22. Performance evaluation Simulation Parameters

23. Average Number of Retransmissions

24. Average Percentage of Collisions

25. MAC End-to-end Delay, 600 Vehicles

26. MAC Delay Percentiles, 200 Vehicles

27. MAC Delay Percentiles, 600 Vehicles

28. Conclusion • The performance of the DBA-MAC has been compared with other schemes, by showing general advantages in • Performance • Reliability • overhead reduction.