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  1. 1. Performance Comparison of Three Location Service Algorithms for Vehicular Ad Hoc Networks Wan Chih Chang
  2. 2. Outline <ul><li>Intersection Location Service (ILS) </li></ul><ul><li>Grid Location Service (GLS) </li></ul><ul><li>Hierarchy Location Service (HLS) </li></ul>
  3. 3. DREAM Homezone <ul><li>The Distance Routing Effect Algorithm for Mobility </li></ul><ul><li>Uses flooding to spread position information </li></ul><ul><li>The capacity of the network is substantially decreased as a result of message flooding, especially in situations where the nodes make frequent position changes </li></ul><ul><li>Homezone does not require flooding </li></ul><ul><li>The homezone becomes empty, and some cars may get into situations where their default location servers are temporarily unavailable. </li></ul>
  4. 4. Grid Location Service (GLS) <ul><li>Divides the area of the entire ad hoc network into a hierarchy of squares forming a quad-tree. </li></ul><ul><li>Each node selects one node in each element of every levels of the quad-tree as a location server. </li></ul><ul><li>The density of location servers for a particular node is high in areas close to the node and become exponentially sparse as the distance to the node increases. </li></ul>
  5. 5. Hierarchy Location Service (HLS) <ul><li>Partitions the area of the ad hoc network into cells. </li></ul><ul><li>The cells are grouped into regions level by level. </li></ul><ul><li>A node uses a hierarchy of location servers to store its location information. </li></ul><ul><li>The problem of empty cells where location updates or requests may run into is solved by temporary servers through a handover mechanism to bridge the gap. </li></ul>
  6. 6. Intersection Location Service (ILS) <ul><li>Consistent Hashing </li></ul><ul><li>Query for Location </li></ul><ul><li>Dynamic Operation and Failure Recovery </li></ul><ul><li>Location Update </li></ul>
  7. 7. Consistent Hashing
  8. 8. Query for Location
  9. 10. Dynamic Operation and Failure Recovery <ul><li>Leaving the network </li></ul><ul><li>Joining the network </li></ul>
  10. 11. Location Update
  11. 12. First Simulation <ul><li>Table 1 : Parameters for the study of car speeds. </li></ul><ul><ul><li>Number of cars 80 </li></ul></ul><ul><ul><li>Area size (m2) 900x900 </li></ul></ul><ul><ul><li>Mean velocity (m/s) 10, 20, 30,40 </li></ul></ul><ul><ul><li>Velocity deviation (m/s) 5 </li></ul></ul><ul><ul><li>Pause time (s) 5 </li></ul></ul>
  12. 13. Query success ratio (QSR)
  13. 14. Second Simulation <ul><li>Table 2 : Parameters for the study of car speeds </li></ul><ul><ul><li>Number of nodes (cars) 20~80 </li></ul></ul><ul><ul><li>Area size (m2) 900x900 </li></ul></ul><ul><ul><li>Mean velocity (m/s) 40 </li></ul></ul><ul><ul><li>Velocity deviation (m/s) 5 </li></ul></ul><ul><ul><li>Pause time (s) 5 </li></ul></ul>
  14. 16. Third Simulation <ul><ul><li>The pause time at intersections to be uniformly distributed in the interval [0,5] s instead of a constant of 5 s. </li></ul></ul><ul><ul><li>The initial position of each car is set in a way such that its distance to the nearest intersection is uniformly distributed from [0,100] m instead of a constant of 0 m. </li></ul></ul><ul><li>All the simulation parameters are the same as those in Table 2 </li></ul>
  15. 18. Number of cars 80 Mean velocity (m/s) 10, 20, 30,40
  16. 19. Large Scale Simulations <ul><li>Table 3 : Parameters for the large scale simulations. </li></ul><ul><ul><li>Number of nodes 80, 180, 320 </li></ul></ul><ul><ul><li>Area size (m2) 900x900, 1350x1350, 1800x1800 </li></ul></ul><ul><ul><li>Mean velocity (m/s) 40 </li></ul></ul><ul><ul><li>Velocity deviation (m/s) 5 </li></ul></ul><ul><ul><li>Pause time (s) [0,5] </li></ul></ul><ul><ul><li>The number of intersections increases from 25 to 64 and 100 as the size of areas increases. </li></ul></ul><ul><ul><li>Both the size of cells in HLS and the size of order-one squares in GLS increase from 112.5x112.5 m 2 to 168.75x168.75 m 2 and 225x225 m 2 . </li></ul></ul>
  17. 20. The area size varying from 900x900 m 2 to 1350x1350 m 2 and 1800x1800 m 2
  18. 21. The area size of 1800*1800 m 2
  19. 22. Conclusion <ul><li>ILS, a location service algorithm that is designed to work in the city environments with streets and intersections. </li></ul><ul><li>increased success ratios under different network topologies. </li></ul><ul><li>ILS algorithm not only remains robust at high car speeds but also demonstrates higher scalability than the other two with respect to network size. </li></ul>
  20. 23. ~Thank you~