Connectivity Aware Routing for Vehicular Ad Hoc Networks - PowerPoint PPT Presentation

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Connectivity Aware Routing for Vehicular Ad Hoc Networks

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  1. Connectivity Aware Routing for Vehicular Ad Hoc Networks Qing Yang, Alvin Lim, Prathima Agrawal Auburn University IEEE Wireless Communications & Networking Conference March 31 – April 3, 2008, Las Vegas

  2. Outline • Goals • Basic concepts • Related works • Assumptions • Model of the connectivity • Validation with VanetMobiSim • Routing strategy • Simulations and result analysis • Conclusions IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  3. Goals • Achieves routing between two ends IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  4. Basic concepts • Model the probability of connectivity of each road segment • Find the route with the highest probability of connectivity • Carry-and-forward the packet while facing network partitions IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  5. Related Works • VADD (’06Infocom) • Vehicle-Assisted Data Delivery • MURU (’06MobiQuitous) • Multi-Hop Routing for Urban Vanet • GSR (’05MC2R) • Geographic source routing • GPSR (’00MobiCom) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  6. Assumption • GPS on each vehicle • Standard component • Digital maps [1,2] • Vehicle density • Vehicle speed • Traffic light period 1. http://www.mapmechanics/ 2. http://www.yahoo.com/ IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  7. …. n cars n0 cells m cells Model of connectivity • One lane road segment • road segment (length is L) is equally divided into m cells • each cell can contain only one node • communication range is size of n0 cells IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  8. …. …. Multiple lanes case • One lane road segment • Number of empty cells is m-n • Multiple lanes road segment • Number of lanes is n’ • Number of empty cells ranges [m-n, m-n/n’] IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  9. …. Problem formulation • Problem formulation • What is the probability that network is connected • The probability that no gap in networks is larger than the communication range • Random Allocation (RA) theory 1 0 0 1 1 0 1 2 0 1 1 1 1 IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  10. Probability of connectivity • P1 (exists exactly k empty cells) • P2 (exists more than n0continuous empty cells) • Pcon (Probability of connectivity) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  11. VanetMobiSim • Feature • multi-lane roads • separate directional flows • traffic signs at intersections • Intersection management • Lane changing • VanetMobiSim[3] mobility patterns have been validated against TSIS-CORSIM • a well known and validated traffic generator 3. http://vanet.eurecom.fr IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  12. Validation of connectivity model • Length of road • 1000m, 1800m • Traffic light period • 60sec., 120sec. • Average velocity • 7.5m/s, 10m/s IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  13. Result of validation • 1000m, 7.5m/s and 60sec IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  14. Result of validation (cont’) • 1800m, 10m/s and 120sec IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  15. Probability of connectivity of route p3 p8 • Pi: probability of connectivity of road segment i • Pcon: probability of connectivity of selected route (path) • Defined as ∏Pi p1 p11 p6 p4 p9 p1*p4*p7*p12=Max? p2 p7 p12 p5 p10 IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  16. Computation of Pr • Define of Pr: • sequence of road segments from source to destination • Modified Dijkstra Algorithm • Final goal: maximize the probability of whole path • Each step: add one more edge, the probability of new path decrease • Can be computed • Centralized • Distributed IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  17. Computation of Pr (cont’) • Centralized • Path Pr was computed only by source node • Size of packet header is proportionate to hop number • Distributed • Every node who received packet computes Pr • More processing on vehicles IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  18. Routing strategy • Compute Pr • Find hops on road segment along Pr • Every node beacons its current position • Predict neighbor’s position while choosing next hop • Carry and forward • Buffered packet if no available next hop • Send buffered packet when new next hop is in range IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  19. Carry and forward strategy • Buffer packets which cannot be forwarded • Send out buffered packet if new next hop is available • Good for VANET • Lots of “holes” in VANET • On path Pr, higher probability of obtaining a new next hop • Big buffer is feasible in cars Wisitpongphan, N.; Bai, F.; Mudalige, P.; Tonguz, O. K., "On the Routing Problem in Disconnected Vehicular Ad-hoc Networks," INFOCOM 2007. 26th IEEE International Conference on Computer Communications. IEEE , vol., no., pp.2291-2295, May 2007 IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  20. Simulation • Nodes movement • VanetMobiSim • Map • TIGER/LINE • Real map from Tennessee • Network simulation • Ns2 setup • Result analysis IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  21. Map information • TIGER[4] • Topologically Integrated Geographic Encoding and Referencing • A format used by the United States Census Bureau to describe land attributes • Roads, buildings, rivers, and lakes • Can be read by Tivec[5] 4. http://www.census.gov/geo/www/tiger/ 5. http://www.triusinc.com/latest.htm IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  22. Map in simulation • Centered at • Long: -84877562 • Lat: 35162102 • Size • Width: 2000m • Length: 2000m IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  23. Ns2 setup • Simulation Area: 2000m*2000m • Number of nodes: 100, 200 • Communication range: 250m • Packet size: 512 Byte • CBR rate: 0.1 ~ 1packet/sec. • Random selected source and fixed destination • Buffer size: 64kBytes • Beacon interval: 1.0 sec. • Velocity: 15 ~ 35 MPH IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  24. Data delivery ratio (100nodes) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  25. Data delivery ratio (200nodes) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  26. Networking delay (100nodes) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  27. Networking delay (200nodes) IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  28. Throughput IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  29. Conclusions • Connectivity issue is very important in VANET • CAR performs well and is independent on the network density • Perimeter mode of GPSR suffers in frequently disconnected networks IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008

  30. Questions and comments Thanks! IEEE Wireless Communications & Networking Conference (WCNC), Las Vegas, 2008