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VANET-DSRC Protocol for Reliable Broadcasting of Life Safety Messages

VANET-DSRC Protocol for Reliable Broadcasting of Life Safety Messages. Mostafa M. I. Taha Electrical Engineering Dept., Assiut University, Arab Republic of Egypt. IEEE ISSPIT 2007. Reliable Broadcasting of Life Safety Messages. Outline : Introduction to VANET technology

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VANET-DSRC Protocol for Reliable Broadcasting of Life Safety Messages

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  1. VANET-DSRC Protocol for Reliable Broadcasting of Life Safety Messages Mostafa M. I. TahaElectrical Engineering Dept., Assiut University, Arab Republic of Egypt IEEE ISSPIT 2007

  2. Reliable Broadcasting of Life Safety Messages • Outline: • Introduction to VANET technology • Categories of broadcasting protocols • Proposed protocol • Conclusion

  3. Internet RSU OBU What is a VANET? VANET: Vehicular Ad-Hoc Network (VANET) DSRC: Dedicated Short Range Communications

  4. Why VANET? • Increase traveler safety • Decrease traveling time and fuel consumption • Increase on board luxury

  5. VANET Applications • Public Safety • Co-operative Collision warning [V-V] • Intersection Collision Warning • Approaching Emergency Vehicle • Work Zone Warning [R-V] The main categorized applications of VANETs are • Non-Public Safety • Electronic Toll Collection • Data Transfer • Parking Lot Payment • Traffic Information

  6. VANET characteristics • High mobility nodes • Predictable topology (using digital map) • Critical latency requirements • Slow migration rate • No problem with power • Security and privacy The main characteristics of VANETs

  7. VANET challenging problems • Broadcasting: • should be reliable with very low latency. • Routing: • High mobile Ad-Hoc network • Security: • Anonymity to prevent car tracking. • Authenticity to prevent false alarms • Integrity to prevent hacking • Accountability to ensure punishment for bad actions

  8. Broadcasting in VANETs • Requirements: • Reliability • Minimum collisions • Minimum latency • High dissemination speed • Problems: • No prior control messaging • High mobility • Hidden terminal problem • Different traffic volumes • Different environments (Urban or rural)

  9. Categories of Broadcasting Protocols • Dissemination protocols, a coordination between nodes to have a broadcast that covers all nodes in the message propagation direction Problems: Multi-hop without any control messaging Metrics: Receipt rate, Dissemination speed and Redundancy

  10. Categories of Broadcasting Protocols • Minimum Connected Dominating Set: is the minimum set of connected nodes that, every other node in the network is one–hop connected with a node in this set. MCDS gives theoretical optimal performance

  11. Categories of Broadcasting Protocols • Flooding: it is each node responsibility to determine if it will rebroadcast the message. • Single relay: it is the source node responsibility to determine the next hop

  12. Categories of Broadcasting Protocols • Reliable protocols, a single source trials to cover a single communication range with highest possible reliability Problems: No feedback Metrics: Receipt rate, Latency, and Collision rate

  13. Categories of Broadcasting Protocols • Rebroadcast: where the source node retransmits the same message for many times • Selective ACK: where the source node requires ACK from small set of the neighbors

  14. Why not IEEE 802.11 • Not reliable • CSAM/CA • Hidden terminal problem • Static contention window size (CW)

  15. The Proposed Protocol • Main Ideas • Application adaptive • Time-based segmentation • Non-equal segments • Headway Model • Methodology • A RTB/CTB with node using adaptive segmentation algorithm

  16. Headway Model Headway Time Headway Semi-Poisson Headway Model

  17. P3 P1 P2 Time-based segmentation • Divide range into N adjacent and non-overlapping segment of non-equal lengths • Lengths are in Headway second • Monotonically increasing (Traffic concept)

  18. P3 P1 P2 S3 S1 S2 P3 P1 P2 S1 S3 S2 P1 P3 P2 S3 S1 S2 Modes of Operation

  19. Proposed Algorithm • Algorithm Steps • Actions of Source Node • Actions of Other Nodes

  20. Proposed Algorithm • Actions of Source Node start Send RTB yes no Received CTB within SIFS+(N+1)Ts? Again? yes no Continue session end

  21. Set DIFS= SIFS+(N+2)TS Check mode no Is a following Vehicle yes Find segment number Si Received CRB within SIFS+(i-1)Ts? yes no Send CTB Continue session start end Proposed Algorithm • Actions of Other Nodes

  22. DIFS RTB Source DATA SIFS SIFS SIFS Destination CTB ACK Simulation methodology 1- Contention starting time = DIFS + RTB 2- Success broadcast time = SIFS + CTB + SIFS + DATA + SIFS + ACK 3- Collision time = DIFS + RTB + SIFS + CTB 4- Waiting time = a single time slot Delay sources

  23. Simulation Results • Points of segmentation for minimum collision probability in different number of segments for Mode I

  24. 3-seg 4-seg 5-seg 6-seg 7-seg UMB SB Simulation Results Latency (usec) Distance (sec)

  25. Discussion • Broadcasting beyond single transmission range. • Hidden terminal problem at far range nodes. • Superior of the time-based segmentation. • The use of RTB/CTB instead of the message directly

  26. Conclusion • A new broadcasting protocol with these novel features: • Application adaptive with special care for public safety and emergency applications • Time-based segmentation • Include effects of human behaviors (headway model) • non-equal segmentation for best performance

  27. Q&A Thank you Questions?

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