1. TrafficGather: An Efficient and Scalable Data Collection Protocol for Vehicular Ad Hoc Networks Wang-Rong Chang Department of Electrical Engineering, National Cheng Kung University, Taiwan Hui-Tang Lin, Bo-Xuan Chen Institute of Computer and Communication Engineering, National Cheng- Kung University, Taiwan IEEE Consumer Communications & Networking Conference ( CCNC ) 2008

2. Outline Introduction Overview TrafficGather Data Collection Protocol Simulation Conclusions

3. Introduction Nowadays, vehicles have become an indispensable part of modern life. Inter-Vehicle Communication (IVC) has attracted considerable attention from both academia and industry. IVC is a powerful tool for promoting road safety and commercial applications in vehicular ad hoc networks (VANets). One of the primary applications of IVC is the provision of road traffic information. Traffic jams to emergency vehicles such as ambulances, fire engines, police vehicles, paramedics.

4. Introduction Recently, many researchers have proposed IVC Medium Access Control (MAC) protocols for vehicular ad hoc networks (VANets). Self-organizing scheme vehicles can subdivides the road on demand each cluster-head collect data in cluster each cluster-head can negotiate the traffic information each other the direction of vehicles i cluster 1cluster 2

5. Introduction In the scheme, the data collection will suffer from many message collision. i the direction of vehicles i

6. Introduction the paper proposed a efficient data collection protocol for VANET. To avoid the message collisions To reduce the message collection time i

7. Network Assumptions Each vehicle equips a GPS and digital map. Minimum vehicle length is L s meters. Each vehicle communication range is R. The number of lanes is M.

8. Overview A RM When Vehicle A want to acquire traffic information, the Vehicle A will broadcast the Request Message (RM). B C D EF G H I J the direction of vehicles

9. Overview RM The RM will be forwarded by vehicle which is downstream direction and the farthest from the source A B C D EF G H I J the direction of vehicles

10. Overview RM A B C D EF G H I J the direction of vehicles The RM will be forwarded by vehicle which is downstream direction and the farthest from the source

11. Overview To find the appropriate cluster-head candidates among the vehicles and then to subdivide the network into a series of contiguous cluster. A B C D EF G H I J the direction of vehicles Cluster 0Cluster 1 CV 0RV 0CV 1 CV: Cluster-head Vehicle RV: Relay Vehicle

12. Overview A B C D I J the direction of vehicles Cluster 0 CV 0 A Road Section Lane(j) Segment(i) 0 123456 0 1 2 To avoid the message collisions

13. Overview A B C D I J the direction of vehicles Cluster 0 CV 0 A Road Section Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021

14. TrafficGather Data Collection Protocol Phase I: Network Configuration Phase Clustered organization scheme Organization termination scheme Phase II: Data Collection Phase Intra-Cluster Space Division TDMA access control algorithm Cluster synchronization scheme Phase III: Data Retrieval Phase

15. Phase I: Network Configuration Phase Clustered organization scheme Request Message MT (1-bit)CV-IDMD (2-bit)GP Indicate the RM broadcasted by a CV or a RV MT = 0: from CV MT = 1: from RV Contain the ID of vehicle which is current CV Indicate the transmission direction of the RM RM = 01 downstream direction RM = 10 upstream direction RM = 11 both direction GPS position of the CV which issued the RM

16. Phase I: Network Configuration Phase A RM B C D EF G H I J the direction of vehicles CV 0 0 01GPS_A When Vehicle A want to acquire traffic information, the Vehicle A will broadcast the Request Message (RM).

17. Phase I: Network Configuration Phase A B C D EF G H I J the direction of vehicles B,C,D 可經由 RM 與自己的 GPS 得知自己在 A 的 downstream direction ，並 把自己設為 Cluster 0

18. Phase I: Network Configuration Phase A B C D EF G H I J the direction of vehicles Waiting time threshold = 1/ distance between the position of itself and the position of CV 0 WM

19. Phase I: Network Configuration Phase A B C D EF G H I J the direction of vehicles WM B, C will concede defeat and take no action.

20. TrafficGather Data Collection Protocol A B C D EF G H I J the direction of vehicles Because vehicle D win the race and MT = 0, the vehicle D become a RV RV 0

21. TrafficGather Data Collection Protocol A B C D EF G H I J the direction of vehicles RV 0 RM 1RV 001GPS_D RV 0 reset the RM and forward the RM

22. Phase I: Network Configuration Phase RM A B C D EF G H I J the direction of vehicles CV 1 CV 1 reset the RM and forward the RM 0CV 101GPS_F

23. Phase I: Network Configuration Phase RM A B C D EF G H I J the direction of vehicles RV 1 Organization termination scheme When G located outside of this data collection range to RM, it will ignore the RM

24. Phase I: Network Configuration Phase A B C D EF G H I J the direction of vehicles Cluster 0Cluster 1 CV 0RV 0 CV: Cluster-head Vehicle RV: Relay Vehicle CV 1 Phase I completion

25. Phase II: Data Collection Phase A B C D I J the direction of vehicles Cluster 0 CV 0 A Road Section Segment(i) (0 <= i <= N-1) 0 123456 Intra-Cluster Space Division N = 2R / L s ( R = 17.5m, L s = 5m)

26. Phase II: Data Collection Phase A B C D I J the direction of vehicles Cluster 0 CV 0 A Road Section Lane(j) 0123456 0 1 2 Intra-Cluster Space Division Segment(i) (0 <= i <= N-1)N = 2R / L s ( R = 17.5m, L s = 5m)

27. Phase II: Data Collection Phase A B C D I J the direction of vehicles Cluster 0 CV 0 A Road Section Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021 δ = i + j * N + 1 Intra-Cluster Space Division

28. Phase II: Data Collection Phase A B C D I J the direction of vehicles CV 0 Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021 TDMA access control algorithm (TACA) x y GPS ICV 0

29. Phase II: Data Collection Phase A B C D I J the direction of vehicles Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021 The RV 0 will occur collision RV 0 1 8 15 CV 0 CV 1 7

30. Phase II: Data Collection Phase Cluster synchronization scheme T is the time index when Phase I terminated （ according to the distance ） Δis the collection time for a cluster = M * N * t

31. Phase II: Data Collection Phase A B C D I J the direction of vehicles CV 0 Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021 The CV 0 will sends a “HELLO” message to all cluster member to collect their traffic informations. HELLO

32. Phase II: Data Collection Phase A B C D I J the direction of vehicles CV 0 Lane(j) Segment(i) 0 123456 0 1 2 1234567 891011121314 15161718192021 The CV 0 will sends a “HELLO” message to all cluster member to collect their traffic informations.

33. Phase III: Data Retrieval Phase The current study adopts a flooding strategy to retrieval the traffic information.

34. Simulation L s = 5 m （ for all vehicles ） Velocity for each vehicle is randomly generated with a uniform distribution within the interval U[36, 37] Goodput = the number of information messages received by all of the CVs / the total number of vehicles on the road.

35. Simulation

37. Conclusions This paper has presented a data gathering mechanism for VANets based on a self-organizing cluster networking approach. The proposed protocol, designated as TrafficGather, achieves collision-free transmissions and therefore improves the efficiency and accuracy of gathering the traffic information on the road.

38. Thank you