Trajectory Based Forwarding and its Applications

1. Trajectory Based Forwarding and its Applications Presented by Yu-En Tsai Slides partially from Pascal A. Vicaire (UVa) and Dragos Niculescu (Mobicom presentation)

2. Outline • Trajectory based forwarding • Why is it useful? Applications • Trajectory expression and forwarding methods • Adverse conditions • Conclusion

3. Motivation • Problems in ad hoc (sensor) networks: • Discovery • Multipath routing • Multicast • Mobility • Scalability

4. Trajectory Based Forwarding • Improving routing in both mobile and fixed networks when position is available. Forbidden Zone Intermediate Destination Straightforward Path Destination Source Subtle Path Assumption: Each Node Knows Its Position

5. Advantages • No routing tables • Fixed packet overhead • scalable to large/dense networks • Cheap path diversity • Decoupling of path name from the path • Common framework • unicast, multicast, broadcast, discovery, multipath

6. Outline • Trajectory based forwarding • Why is it useful? Applications • Trajectory expression and forwarding methods • Adverse conditions • Conclusion

7. Applications (1): Unicast Routing • Routing  Forwarding • Routing = Determining Trajectory + Forwarding • How to determine the trajectory? Destination Feedback Better Trajectory ? Obstacle Detection Source Initial Estimation

8. Applications (2):Multipath Routing • TBF provides cheap path diversity • Advantages: • Load balancing Source Destination

9. Applications (2):Multipath Routing • TBF provides cheap path diversity. • Advantages: • Load balancing. • Resilience. Source Destination

10. Applications (3):Mobility • Path name decoupled from the path itself. Source Destination

11. Applications (3):Mobility • Path name decoupled from the path itself. Source Destination

12. Applications (3):Mobility • Path name decoupled from the path itself. Source Destination

13. Applications (3):Mobility • Path name decoupled from the path itself. Source Destination

14. Applications (4):Discovery Node: High Temperature? Correction Can we Guarantee the Intersection? Orders Sensor: High Temperature!

15. Applications (4):Discovery Why Sending in Four Directions?

16. Applications (5):Broadcasting Communication for Flooding Communication for TBF Is that Fantastic? Number of Radial Directions

17. Applications (5):Broadcasting Coverage for Flooding Coverage for TBF Low coverage when size increases! Number of Radial Directions

18. Applications (5):Broadcasting Classical Methods Cover All or Most of the Network TBF Squares Cover a Portion of the Network Only! Size of the Squares? Which Percentage of the Network does it Cover?

19. Applications (6):Multicast • Advantages: • No complex routing tables. • No group setup or tree maintenance.

20. Outline • Trajectory based forwarding • Why is it useful? Applications • Trajectory expression and forwarding methods • Adverse conditions • Conclusion

21. Y Y Y X X X Trajectory Expression/Encoding Parametric: X = X (t) Y = Y (t) ? Functional: Y = f (X) Discrete: Point 1 Point 2 Point 2 Point 3 Requires Explicit Solution Equational: X2 + Y2 = R2

22. Trajectory Expression/Encoding • A line with slope αpassing through the source with coordinates • Represented by a tuple • Fixed dictionary of trajectories or specified as a number of simple components (Fourier components) • Recursive representation

23. Forwarding Methods • Minimum deviation from the initial trajectory. Node Closest to the Curve, With Minimum Residual S N

24. Forwarding Methods • Most Forwarding. Node with Maximum Residual N Is Minimum Number of hops Guaranteed? S

25. Forwarding Methods • Node with Most Battery Left. Load Balancing Along a Given Trajectory Might Require More Hops and Diminish the Overall Energy of the System Faster. S

26. Forwarding Methods • Node Advancing Along the Trajectory. N S

27. Forwarding Methods • Centroid of the Feasible Set. • Center of Mass? • Median residual? • Median distance to the curve? S N

28. Forwarding Methods • Random Between Best Three. S

29. Outline • Trajectory based forwarding • Why is it useful? Applications • Trajectory expression and forwarding methods • Adverse conditions • Conclusion

30. Sparse Networks (Obstacles) • Physical obstacles. • Low connectivity zones. • Dead nodes. • Sleeping nodes. • Low energy nodes. • Zones to be avoided.

31. Sparse Networks (Obstacles)Solution: Greedy-FACE-Greedy algorithm Right hand rule S How do we know the exit?

32. Sparse Networks (Obstacles) Solution: sender of the trajectory has a rough estimation of the obstacle size Resume Regular Forwarding Starting Right Hand Algorithm Δ

33. Sparse Networks (Obstacles) Δ Δ Δ Δ Underestimation

34. Sparse Networks (Obstacles) Δ Overhead in Computation Time Overestimation

35. No Positioning • Assume other capabilities • AoA, ranging, compass, accelerometer • Use localized schemes • Some landmarks: APS, AhLOS, SPA • No landmark: Local Positioning System • Produce imprecise positions

36. Imprecise Locations

37. Imprecise Locations • Paths 15-25 hops; 200 random pairs of nodes; degree 8-20 Results Acceptable for Huge Networks Zero Median

38. Conclusion • A hybrid between source based routing and Cartesian forwarding • Transition from a discrete view of the paths to a continuous view • Advantages • cheap path diversity • decouples path naming from the path • Common framework • routing, broadcasting, discovery • Need positioning