1. Virtual Domain and Coordinate Routing in Wireless Sensor Networks
Chien-Chun Hung
CMLab, CSIE, NTU, Taiwan

2. Outline Introduction and Related Work VDCR Assignment Protocol
VDCR Routing Protocol
Performance Evaluation
Future Work and Conclusion

3. Introduction and Related Work
The effectiveness of the routing scheme directly affect resource usage.
Data centric storage,
Database-like query,
Data transfer

4. Introduction and Related Work
The design goals for sensor networks:
Small hop stretch
The ratio of the hop distance of the selected route to the hop distance of the shortest path.
Light overhead
Preprocess overhead
Path lookup overhead
Delivery-guarantee

5. Introduction and Related Work
Existing studies for end-to-end routing:
On-demand routing
No preprocess overhead
Delivery-guaranteed
The smallest hop stretch
Significant path lookup overhead
Ex: AODV, DSR

6. Introduction and Related Work
2. Geographic location-based routing
Use physical location as network address
Relay packet to the neighbor which is closer to the destination
Might fail at dead end
Might have larger hop stretch in sparse network
Difficult to get location information
Ex: GPSR, GFG

7. Introduction and Related Work
3. Location-free routing
Operate without location information while improving the hop stretch with reasonable overhead.
None of the previous works achieve all of the design goals simultaneously.
Ex: Vcap, ABVCap, GEM

8. Introduction and Related Work
The goal of our work:
A location-free point-to-point routing scheme
Achieve smaller hop stretch
Exploit low overhead
Delivery-guaranteed

9. Outline Introduction and Related Work VDCR Assignment Protocol
VDCR Routing Protocol
Performance Evaluation
Future Work and Conclusion

10. Why designing domain? Anchor nodes Domain neighbors
Anchor trees: shortest path
Domain neighbors
All the ancestor and descendent nodes in all anchor tress
Exploit domains to locate any node belonging to the destination’s domain neighbors

11. VDCR Assignment Protocol
Virtual coordinate
Assist the relay node greedily select the neighbor closer to the destination.
Virtual domain
Verify whether there exists an established shortest path to the destination.

12. VDCR Assignment Protocol
Select k nodes as anchor nodes
Each node has a k - tuple domain and a k – tuple coordinate.
The assignment procedure can be divided into 3 phases:
CoorAssign phase
SizeCollect Phase
DomainAssign phase

13. VDCR Assignment Protocol
CoorAssign phase
Anchor i assigns the coordinates by flooding an i_COOR message to all nodes in the tree.
SizeCelloct phase
Collect the size of leaf node of each sub-tree
DomainAssign phase
Assign the domain to each of its child a subset of its domain

14. Outline Introduction and Related Work VDCR Assignment Protocol
VDCR Routing Protocol
Performance Evaluation
Future Work and Conclusion

15. VDCR Routing Protocol We assume that:
Each sensor node is aware of virtual domains and virtual coordinates of its one hop neighbors
The source node can get the address of the destination by location service
The source issues a path-discovery packet to discover routing path to the destination.
Domain mode
Coordinate mode
Angle-based landmark mode

16. VDCR Routing Protocol Domain mode
If the relay node’s domain is within the destination’s domain, the next hop is its parent.
Otherwise, the next hop is its child whose domain contains the destination’s domain.

17. VDCR Routing Protocol Coordinate mode:
Greedily select the neighbor that is closest to the destination.
The distance function is defined as:

18. VDCR Routing Protocol Angle-based landmark mode:
Proposed to solve the dead-end problem.
Pick an anchor as the landmark
Angle-based instead of distance-based
The Cosine Formula:

19. VDCR Routing Protocol

20. Outline Introduction and Related Work VDCR Assignment Protocol
VDCR Routing Protocol
Performance Evaluation
Future Work and Conclusion

21. Performance Evaluation
20 connected network topologies are randomly generated.
1000 source-destination pairs are selected for each topology.
The obstacles are circles of radius 40m.

22. Performance Evaluation
Comparison schemes:
ABVCap
GEM
GPSR
VDCR (k=3)
VDCR (k=4)

23. Impact of Number of Anchor Nodes

24. Impact of Network Density
The improvement of VDCR to ABVCap and GEM are 50% ~ 62% and 81% ~ 87%

25. Scalability of Large Topologies
The average path length grows as the network gets larger.

26. Impact of Obstacles
For GPSR, physical position cannot reflect the situation of obstacles.
The higher probability it suffers from dead-end.
The longer path is required to bypass the obstacles.

27. Outline Introduction and Related Work VDCR Assignment Protocol
VDCR Routing Protocol
Performance Evaluation
Future Work and Conclusion

28. Conclusion A location-free point-to-point routing protocol: VDCR
Assignment protocol in preprocess stage
Routing protocol in routing stage
Delivery-guaranteed
Minimize hop stretch
With low preprocess overhead
Compared with ABVCap and GEM, the improvement by VDCR is obtained by 75% ~ 84%, and 62% ~ 70%, respectively.

29. Future Work How to balance loads among sensor nodes?
How to prolong a network lifetime?
How to support disconnected or mobile networks due to switch-of or mobility?

31. VDCR Assignment Protocol
The first anchor node is the sink node
Select the next anchor node which is likely to be at the boarder of the sensor network.
Increase the number of each node’s domain neighbor
Increase the probability of meeting destination’s domain neighbors