Geographic Routing without Location

Information

Geographic Routing without Location

InformationAnanth 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 nodes8 units

Perimeter Nodes Know Location

• Relaxation procedure– All non-perimeter nodes can determine

their coordinates– X_coordinates

Y_coordinates

X1………………………..Xn

x3 x5x4

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.)

Performance (cont.)

hops

Performance (cont.)

Conclusion• This paper present an algorithm

for assigning coordinates to nodes– virtual coordinates

• used to perform geographic routing