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Bounded-Latency Alerts in Vehicular Networks

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Bounded-Latency Alerts in Vehicular Networks

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    1. Bounded-Latency Alerts in Vehicular Networks Rahul Mangharam, Raj Rajkumar & Mark Hamilton Dept. of Electrical & Computer Engineering Carnegie Mellon University Priyantha Mudalige & Fan Bai General Motors Research & Development , U.S.A

    2. 2 Outline Requirements for VANET Safety Applications Broadcast Storm Problem and Probabilistic Solutions Location Division Multiple Access Protocol Vehicle Network Simulation and On-road testing Conclusion

    3. 3 Protocol Requirements for VANET

    4. 4 Driver Reaction Time Driver reaction time 1.5-2.5 seconds Slower reaction with higher cognitive load Driver Perception accounts for ~50% of reaction distance Drivers respond faster to audio signals End-to-end Delay budget 1.5 sec for 1km 2.5 sec for 2km

    5. 5 Probabilistic Solutions to the Broadcast Storm Problem Back-off Probability Location-based suppression Position-based suppression Neighbor-based suppression

    6. 6 Overview of LDMA Operation

    7. 7 Active Region Programming Out-of-band LDMA Control Channel

    8. 8 Location Division Multiple Access

    9. 9 Simple LDMA Schedule

    10. 10 1-D LDMA Pipelines LDMA Spatial Definition 300m transmission range 100m LDMA cells LDMA Temporal Schedule {A, C, B} 200m/10ms ? 20,000m/s {A, B, C} 100m/10ms ? half-speed

    11. 11 Multiple LDMA Active Regions

    12. 12 Scalable LDMA Spatial and Temporal Representation Tree-based Cell activation and Schedule Assignment

    13. 13 LDMA 2D Scheduling County-wide slot assignment based on 2-D grid for dense urban regions Use 1D slot assignment for sparse rural roads and highways

    14. 14 Current State of Vehicular Network Design

    15. 15 GrooveNet Hybrid Simulator Design

    16. 16 GrooveNet Demo

    17. 17 Modular Architecture

    18. 18 Time Synchronization Implementation Using GPS/PPS signal on a gumstix embedded computer Sub-200s local synchronization accuracy with Linux 2.6 2ms pair-wise synchronization accuracy

    19. 19 LDMA Performance Comparison Trade-off between End-to-End Delay and Link Utilization 1D Chain of vehicles at 25 vehicles/km Adaptive Broadcast Schemes Neighbor-based: best trade-off LDMA Smallest delay with controllable message receive rate

    20. 20 Conclusion LDMA Location Division Multiple Access Safety Alerts: Bounded end-to-end delay Conflict-free communication: Multi-hop problem ? single hop one Flexible scheduling Dynamic reconfigurable schedules via FM/RDS control channel Implemented in GrooveNet VANET Virtualization Platform Tightly-coupled Time Synchronization GPS/1PPS with <200s local accuracy 2ms pair-wise sync accuracy Promising direction for time-critical VANET protocols

    21. 21 GPS Dead Reckoning

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