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Broadcasting Protocols in Vehicular Ad-Hoc Networks (VANETs)

Broadcasting Protocols in Vehicular Ad-Hoc Networks (VANETs). By Mostafa M. I. Taha Electrical Engineering Dept., Assiut University August 2008. Broadcasting Protocols in VANETs. Outline: Introduction to VANET Technology Previous Work The Proposed Protocol Conclusion.

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Broadcasting Protocols in Vehicular Ad-Hoc Networks (VANETs)

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  1. Broadcasting Protocols in Vehicular Ad-Hoc Networks (VANETs) By Mostafa M. I. Taha Electrical Engineering Dept., Assiut University August 2008

  2. Broadcasting Protocols in VANETs • Outline: • Introduction to VANET Technology • Previous Work • The Proposed Protocol • Conclusion

  3. Broadcasting Protocols in VANETs • Outline: • Introduction to VANET Technology • Previous Work • The Proposed Protocol • Conclusion

  4. What is VANET? VANET: Vehicular Ad-Hoc Network (VANET) Internet RSU OBU

  5. Why VANET? • Increase traveler safety • 6.2 million vehicle crashes[1] • 2.8 million injuries[1] • 42,000 fatalities[1] • The first cause of death (age group 1 - 44 years)[2] • Costs more than $150 billion per year • Enhance traveler mobility • Boost on-board luxury [1] in 2004 within the USA only [2] in 2006 in the USA

  6. What is Ad-Hoc? • Ad-Hoc Network: is a wireless technology where all nodes are one level topology and can communicate directly with each other without the use of centralized nodes

  7. Why Ad-Hoc? • The elephantine size of paved roads (6.4 million kilometers of highway) [1] • The high mobility of nodes • For a faster rate of deployment • To offer the service at no charge [1] in 2004 within the USA only

  8. Why the use of broadcasting? • The distribution of nodes changes rapidly and unexpectedly • The wireless links initialize and break down frequently and unpredictably. • The OBUs are forced to organize the network distributively “Nodes know nothing about their neighbors”

  9. Problems associated with broadcasting? • Requirements: • Reliability • Minimum latency • Minimum collisions • High dissemination speed • Problems: • No feedback • No prior control messaging • Hidden node problem • Different traffic volumes • Different environments (Urban or rural)

  10. VANET Applications

  11. VANET Characteristics • The main characteristics of VANETs • High mobility of nodes • No prior information about location of nodes • Predictable topology (to some extent) • Critical latency requirements • No problem with power • Slow migration rate • High possibility to be fragmented • Crucial effect of security and privacy

  12. Current Standards • DSRC: Dedicated Short Range Communications • In the USA (IEEE): WAVE, “Wireless Access in Vehicular Environments” • In Europe (CEN): “General Specifications for Medium-Range Pre-Information Via Dedicated Short-Range Communication” • In Japan (ARIB): “Dedicated Short-Range Communication System”

  13. WAVE System Architecture • 802.11p “Wireless Access in Vehicular Environments (WAVE)” ‎ • 1609.1 “Resource Manager” ‎ • 1609.2 “Security Services for Applications and Management Messages” ‎ • 1609.3 "Networking Services” ‎ • 1609.4 “Multi-Channel Operation” ‎

  14. 1609.1, et al. Applications Management Plane Data Plane UDP / TCP WME 1609.3 WSMP IPv6 LLC 1609.4 Multi-ChannelOperation WAVE MAC MLME 802.11p 802.11p PLME WAVE PHY Airlink WAVE System Architecture

  15. Broadcasting Protocols in VANETs • Outline: • Introduction to VANET Technology • Previous Work • The Proposed Protocol • Conclusion

  16. Why not IEEE 802.11 No MAC-level recovery on broadcast frames No ACK (not reliable) No RTS/CTS (hidden node problem) Static contention window size (CW)

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

  18. Categories of Broadcasting Protocols • The source node retransmits the same message more than once • Xu: A static rebroadcasting • Yang(VCWC): Rebroadcasting with a degreasing rate • Alshaer: Adaptive rebroadcasting

  19. Categories of Broadcasting Protocols • The source node requires ACK from small set of the neighbors • Tang(BMW): Unicasting each message • Hugang(BMMM): Unicasting the RTS/CTS and ACK only • Xie(RRAR): Requiring ACK from a single node (round-robin)

  20. Categories of Broadcasting Protocols • Changing transmission parameters of a regular broadcasting based on an estimate of the current state of the network • Balon: Changing the contention window size based on the count of lost messages

  21. Categories of Broadcasting Protocols • A coordination between nodes to have a broadcast that covers all nodes in the network • Problems: Multi-hop without control messaging • Metrics: Success rate, Redundancy and Dissemination speed

  22. Categories of Broadcasting Protocols • It is each node responsibility to determine whether it will rebroadcast the message or not. • Ni: Probabilistic, Counter, Distance, Location, and Cluster-Based schemes • Heissenbüttel (DDB): Location-Based scheme with a differential delay

  23. Categories of Broadcasting Protocols • It is the source node responsibility to determine the next hop • Zanella (MCDS): Minimum Connected Dominating Set • Korkmaz (UMB) : Choosing the furthest node(longest black-burst) • Fasolo (SB): Choosing the furthest node (shortest delay)

  24. Distance (meter) Methodology of Fasolo (SB) 4 3 2 1

  25. Broadcasting Protocols in VANETs • Outline: • Introduction to VANET Technology • Previous Work • The Proposed Protocol • Conclusion

  26. The Design Objective In cases of emergencies, the protocol is used to open an instant communication channel with the vehicle in the most dangerous situation. • Unicast information packed in a broadcast protocol • Belongs to: Reliable Protocols for a Specific Purpose

  27. Main new ideas • 1- Safety-Related Applications • 2- Headway-Based Segmentation • 3- Non-Uniform Segmentation • 4- Application Adaptive

  28. Distance (meter) Distance (meter) 1- Safety-Related Applications 4 3 2 1 1 2 3 4

  29. 2- Headway-Based Segmentation • The headway is the time interval between two vehicles passing a point as measured from the front bumper to the front bumper Headway (sec) Headway (sec)

  30. 2- Headway-Based Segmentation 30 Km/h 120 Km/h Distance (meter) Headway (sec)

  31. 3- Non-Uniform Segmentation • Three Reasons …. Headway (sec)

  32. 3- Non-Uniform Segmentation 1- Location of any vehicle depends largely on the other leading vehicles • The ‘Headway Model’ is a mathematical equation that describes the average naturalistic headway that drivers tend to leave apart.

  33. 3- Non-Uniform Segmentation • 2- Vehicles in nearer segments are more threatened to danger than those in further ones • 3- If there were no vehicles in the first segment, we can expect that the traffic is moderate or low, and let later segments be of wider width. Find the minimum

  34. 3- Non-Uniform Segmentation Study area Headway (sec)

  35. 3- Non-Uniform Segmentation (Results)

  36. 3- Non-Uniform Segmentation (Results)

  37. 4- Application Adaptive 4 3 2 1 Distance (meter) 1 2 3 4 1 2 3 4 Headway (sec) Headway (sec)

  38. start send RTB yes received CTB within ’SIFS+N+1’ Ts? no again? yes no continue session end The Proposed Algorithm (Source Node) • Actions of Source Node

  39. Proposed Algorithm (Other Nodes) 2 1 • Actions of Other Nodes start Find segment number ‘Si' Set NAV to ‘SIFS+N+2’ TS Received CTB within ’SIFS+ i-1’ Ts? yes Check mode no Send CTB no Is an affectedVehicle? Continue session yes 1 2 end

  40. Simulation Results

  41. Robustness at different traffic volumes

  42. Protocol Comparison

  43. Broadcasting Protocols in VANETs • Outline: • Introduction to VANET Technology • Previous Work • The Proposed Protocol • Conclusion

  44. Conclusion • A novel use of “Headway-Based Segmentation” • Non-uniform segmentation “Headway Model” • Unique robustness at different speeds • Unique robustness at different traffic volumes • Superior minimum latency for public safety applications. • Application adaptability with special multi-mode operation. • Offering a solution to novel applications, e.g. “Approaching Emergency Vehicle”.

  45. List of Co-authored Publications • [1] “VANET-DSRC Protocol for Reliable Broadcasting of Life Safety Messages”, In Proceedings of the 7th IEEE International Symposium on Signal Processing and Information Technology - ISSPIT07. Cairo, EGYPT, pp. 104-109, Dec. 2007.Available at: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=4458046 • [2] “Integrated intra-vehicle – VANET system for increasing the road safety,” in Proceedings of the Global Knowledge Forum NOOR-2008, Almadina, KSA, June 2008. • [3] “A Novel Headway-Based Vehicle-to-Vehicle Multi-Mode Broadcasting Protocol” accepted for publication in Proceedings of the 68th IEEE Vehicular Technology Conference - VTC2008-Fall. Calgary, Alberta, CANADA, 21–24 September 2008.

  46. Q&A Thank you Questions?

  47. Q1: Calculating the delay • Contention starting time: DIFS + RTB • Success broadcasting time: SIFS + CTB + SIFS + DATA + SIFS + ACK • Collision time: DIFS + RTB + SIFS + CTB + SIFS • 4- Waiting time: a single time slot. DIFS SIFS DATA RTB Source SIFS SIFS Destination CTB ACK

  48. Q2: Simulation Parameters

  49. N2 N4 N3 N1 Q3: Hidden Node Problem

  50. Q4: Equations used

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