1. FACULTY OF ENGINEERING & INFORMATION TECHNOLOGIES Interference-Aware Message Forwarding for Vehicular Networks Centre for Distributed and High Performance Computing Quincy Tse | PhD Student

2. Outline ›Introduction ›Vehicular networks ›Message forwarding ›Results ›Conclusion 2

3. Everyday, someone dies from car accidents… ›In Australia: -1,627 killed in 2005 [1] -32,777 seriously injured in 2007 [2] ›Per capita stats similar in other developed countries 3 [1] Connelly L. and Supangan R., “The economic costs of road traffic crashes: Australia, states and territories”, Accident Analysis & Prevention, vol. 38, no. 6, pp. 1087–1903, 2006. [2] Hanley G. and Harrison J., “Serious injury due to land transport accidents, Australia, 2006–07”, Australian Institute of Health and Welfare, 2009 Road vehicle traffic—trends in age-standardised rates of serious injury sex and road user group, Australia 2000–01 to 2006–07 [2]

4. Vehicular Network – Getting Cars to Communicate ›Advance warning ›Status sharing ›Packet collision ›Shadowing ›Limited capacity 4 Benefits I should stop now!!We should stop now!! I’ve just crashed at (location) Problems I am at (location), going East at 50 km/h Will it crash into me?

5. Message Re-broadcasting for Reliability 5 ADAD AIAI AGAG Source Relay

6. Results 6

7. Conclusion ›Transmission reliability is important -Shadowing can cause non-reception of messages for safety systems ›Cooperative forwarding may work, but introduces interference ›Proposed an algorithm and a metric to decide whether to retransmit -Takes into account benefit vs interference -Almost as good -Much less interference 7

8. Backup Slides 8

9. How accidents happens ›Perception–Reaction Time -Approx 1.5s for unexpected events [3] ›Fatigue, alcohol, drug use can increase perception–reaction time 9 60km/h Hazard seen Starts to React Stops 25m30m [3] Green, M., “‘How Long Does It Take to Stop?’ Methodological Analysis of Driver Perception-Brake Times”, Transportation Human factors, vol. 2, no. 3, pp. 195–216, 2000.

10. Retransmission Algorithm 10 Message Received Deliver to Application Benefit vs interference Delay Retransmit Someone ReTx Yes Actual BenefitArea Gain Significance of Nodes Max interference per unit gain Node Density ›Calculated at each node for each transmission ›A D and A G are estimated based on received signal strength

11. Simulation 11 ›NS-3 simulation ›802.11a model at 5.8GHz ›Simulates path loss, shadowing and fast fading ›Shadowing caused by heavy vehicles only (Not to scale)

12. Reception Rate vs Distance 12

13. CBT vs Distance 13