1. An Information Model for Geographic Greedy Forwarding in Wireless Ad-Hoc Sensor Networks Zhen Jiang Computer Science Department West Chester University Junchao Ma, Wei Lou Department of Computing The Hong Kong Polytechnic University Jie Wu Department of Computer Sci. & Eng. Florida Atlantic University Infocom 2008

2. Outline Introductions Related works Safety Model For LGF Routing Safety -Information-Based LGF Routing (SLFG) Experimental Results Conclusions

3. Introductions Geographic greedy forwarding routing is the most promising routing scheme in Wireless Ad-hoc Sensor Networks. An important challenge often faced in geographic greedy forwarding in WASNs is the “local minimum phenomenon (Dead end)”.

4. Introductions To mitigate the local minimum issue, GFG,GPSR and GOAFR are currently the most popular methods. However, without enough shape information of the holes, such a routing may use a long detour path in the perimeter routing.

5. Introductions – goal In this paper, the authors propose a simple and efficient method to achieve a shorter path.

6. Related works - Geographic greedy forwarding (GF) B. Karp and H. Kung, “GPSR: Greedy perimeter stateless routing for wireless sensor networks,” Proc. of the 6th Annual ACM/IEEE International Conference on Mobile Computing and Networking (ACM/IEEE MOBICOM’00), August 2000, pp. 243-254. Source Destination

7. Related works - Limited geographic greedy forwarding (LGF) Source Destination Quadrant I (Northeast) Quadrant IV (Southeast) Quadrant II (Northwest) Quadrant III (Southwest)

8. Related works - BOUNDHOLE Q. Fang, J. Gao, and L. Guibas, “Locating and bypassing routing holes in sensor networks,” Proc. of the 23rd Annual Joint Conference of the IEEE Computer and Communications Societies (IEEE INFOCOM’04), 2004, pp. 2458-2468. Source Destination Boundary

9. Safety Model For LGF Routing - assumption Each node has its location information. Sources are aware of the location of the destination. All sensor has the same communication range Each node has four forwarding zone. The system is rounded based

10. Safety -Information-Based LGF Routing (SLGF) Unsafe Node Safe Node Source Destination Unsafe Area

11. Safety Model For LGF Routing – compare with BOUNDHOLE BOUNDHOLE needs boundaries to encircled the hole and there are many unnecessary nodes in a boundary. A boundary may be concave,but the shape of the unsafe are has been optimized to a rectangle in a local view of each unsafe node. Each unsafe node only stores the location of the opposite corner of rectangle Safety model don’t need to calculate to identify the boundary.

12. Safety Model For LGF Routing Quadrant I (NorthEast) Quadrant IV (SouthEast) Quadrant II (NorthWest) Quadrant III (SouthWest) u 1 (NE,NW,SW,SE) u1u1

13. Safety Model For LGF Routing u1(s,s,s,s)u1(s,s,s,s) u1u1 At the beginning, all forwarding regions are labeled as safe. u2(s,s,s,s)u2(s,s,s,s) u3(s,s,s,s)u3(s,s,s,s) u2u2 u3u3 u4u4 u4(s,s,s,s)u4(s,s,s,s)

14. Safety Model For LGF Routing u1(s,s,s,s)u1(s,s,s,s) u1u1 Each node starts labeling process u2(s,s,s,s)u2(s,s,s,s) u3(s,s,s,s)u3(s,s,s,s) u2u2 u3u3 u4u4 u4(s,s,s,s)u4(s,s,s,s)u4(u,s,s,s)u4(u,s,s,s) u3(u,s,s,s)u3(u,s,s,s) u2(u,s,s,s)u2(u,s,s,s) u1(u,s,s,s)u1(u,s,s,s) u5(s,s,s,s)u5(s,s,s,s)

15. Safety Model For LGF Routing Each unsafe node would estimated its unsafe area. Unsafe Area u1u1 u2u2

16. Safety Model For LGF Routing Source Destination Unsafe Node Proof in contrapositive form If a greedy forwarding path exists, we can find an unsafe node u j that its successor u j +1 is safe. ujuj u j+1

17. Safety -Information-Based LGF Routing (SLGF) Unsafe Node Safe Node Source Destination

18. Safety -Information-Based LGF Routing (SLGF) - Source or destination inside unsafe area The SLGF scheme will ignore unsafe node to avoid local minimum. Source Destination Source ? ?

19. Safety -Information-Based LGF Routing – destination inside unsafe area Destination Source Check if D is inside its unsafe area D is inside the area. Forward the packet and discard safety information.

20. Safety -Information-Based LGF Routing - source inside unsafe area The quickest way to leave such an unsafe area is to route in the opposite direction to d Source Destination

21. Experimental Results Simulator: built in c++ Field : 200m x 200m Uniform deployment (IA) (Hole is very small) Random deployment (FA) (Hole is larger than Uniform) The transmission radius of a node is 20m Number of nodes 400 to 800 in incensement of 50

22. Experimental Results - construction process under different information models Boundary of BOUNDHOLE Boundary of Safety Model for type I Both BOUNDHOLE & Safety Model

23. Experimental Results

30. Conclusions This paper is the first attempt to find the balance of the tradeoff between routing adaptivity and information model cost while pursuing better routing performance in WASNs. The authors proposed a easy and quick construction model

31. End