Geographic Routing without Location Information Ananth Rao, Sylvia Ratnasamy, Christos Papadimitriou, Scott Shenker and Ion Stoica MobiCom 2003

Outline Introduction Coordinate Construction –Perimeter Nodes Know Location –Perimeter Nodes are Known –No Location Information Routing Algorithm Performance Conclusion

INTRODUCTION Geographic Routing protocol –Refer to nodes by their location Not address –To route greedily Towards the destination However –Location information is not available at the nodes Geographic methods cannot be used

Introduction (cont.) In this paper –Define a scalable coordinate-based routing algorithm Does not rely on location information Can be used in a wide variety of ad hoc and sensornet environments virtual coordinates –x_coordinates –y_coordinates

COORDINATE CONSTRUCTION A method for constructing virtual coordinates without location information Perimeter nodes –Perimeter nodes know their location –Perimeter nodes know that they are perimeter nodes, but don ’ t know their location –Nodes know neither their location, nor whether they are on perimeter

COORDINATE CONSTRUCTION (cont.) 64 perimeter nodes 8 units

Perimeter Nodes Know Location Relaxation procedure –All non-perimeter nodes can determine their coordinates – X_coordinates Y_coordinates X1 ………………………..Xn x3x5 x4

Perimeter Nodes Know Location (cont.) Initial coordinates (100,100) 3200 nodes

Perimeter Nodes Know Location (cont.) 10 iterations

Perimeter Nodes Know Location (cont.) 100 iterations

Perimeter Nodes Know Location (cont.) 1000 iterations

Perimeter Nodes are Known Perimeter nodes know that they are perimeter nodes, but don ’ t know their location –perimeter nodes flood the network HELLO message To discover the distances (in hops) between all perimeter nodes Triangulation algorithm

Perimeter Nodes are Known (cont.) Step 1 –Each perimeter node broadcasts a HELLO message –perimeter vector Step 2 –Each perimeter node broadcasts its perimeter vector –Every perimeter node knows the distances between every pair of perimeter nodes Step 3 –Every perimeter node uses a triangulation algorithm to compute the coordinates

Perimeter Nodes are Known (cont.)

No Location Information Nodes know neither their location, nor whether they are on perimeter Perimeter node criterion –if a node is the farthest away, among all its two-hop neighbors, then the node decides that it is on the perimeter

No Location Information (cont.)

Routing Algorithm Packets are routed according to three rules –Greedy –Stop –Dead-end

Performance 200 × 200 square units Radio range is 8 units

Performance (cont.)

hops

Performance (cont.)

Conclusion This paper present an algorithm for assigning coordinates to nodes –virtual coordinates used to perform geographic routing