1. Low Overhead With Speed Aware Routing (LOWSAR) in VANETs By Kannikar Siriwong Na Ayutaya

2. Outline Problem Routing Mechanism Related Works Objective Contention-based Routing (CBR) Algorithm Motivation LOWSAR Algorithm Results Conclusion and Future works

3. Why need routing for VANETs? Reasons: High mobility and frequent network disconnection and merging Result: Topology-based routings in MANETs are NOT suitable for VANETs Solutions: Position-based routing and Contention-based routing

4. VANETs Routing Mechanism Beaconing: periodically exchange location message between vehicles Location service: process of searching for unknown destination location Forwarding: transmitting packets to destination (unicast, broadcast, anycast, scan)

5. Related Works Position-based Routing (PBR) –Neighbor positions obtained by beaconing –Routing decision is done locally by one node at a time Contention-based Routing (CBR) –Routing decision is done in distributed manner without beaconing

6. Related Works Position-based Routing (PBR) Contention-based Routing (CBR) 1 2 4 3 1 2 4 3

7. Related Works (Pros & Cons) PBR –Outdated neighbor positions –High routing decision computational complexity –Increase message exchanging overhead –Enhance packet collision –Eliminate packet redundancy CBR –Eliminate beaconing overhead during routing decision –Create possibility of packet redundancy

8. Objective Extend contention-based routing (CBR) to account for speed of vehicles Propose LOWSAR algorithm to speed up data delivery delay

9. Basic CBR Algorithm (Terminology) T = constant bias clock delay r = transmission range D mn = distance from node m to node n d = bias clock delay W = ratio of difference of distance and r

10. 1 3 5 D 15 D 35 r D 15 – D 35 Basic CBR Algorithm W = (D 15 – D 35 )/r 1 d = T(1 – W)

11. D 15 Basic CBR Algorithm d = T 1 3 4 5 6 2 d < Td > T 7 W = (D 17 – D i7 )r, i = 2,…,6d = T(1 – W)

12. 1 2 4 3 5 D 15 D 35 r D 15 – D 35 D 25 D 15 – D 25 D 45 D 15 – D 45 < 0 d = T(1-(D 15 – D 35 )/r) d = T(1-(D 15 – D 15 )/r) = T d = T(1-(D 15 – D 25 )/r) d = T(1-(D 15 – D 45 )/r) > T Basic CBR Algorithm

13. B VAtVAt VBtVBt VCtVCt Problem: Location Dominated Forwarding C A

14. A B C V A > 0 V C = 0 Problem: Speed Dominated Forwarding

15. LOWSAR Algorithm V = vicinity of a vehicle D = distance from a node to destination d = min{ T(1 – W), T(1 – W)/V, T( D/r - 1)}

16. Preliminary Results

17. Conclusion and Future Works Under different speed limits, LOWSAR outperforms CBR in terms of delivery delay Explore effects of other parameters on delivery delay –Number of source nodes –Data rate –Number of vehicles (traffic density)

18. Conclusion and Future Works Investigate on other performance metrics –Average number of hops to a destination –Packet delivery ratio Compare these performance with other compatible routing algorithms