1. Avoiding Energy Holes in Wireless Sensor Network with Nonuniform Node Distribution Xiaobing Wu, Guihai Chen and Sajal K. Das Parallel and Distributed Systems 2008

2. Outline Introduction Energy Hole Problem Analysis of the Nonuniform Node Distribution Strategy Impossibility of Balanced Energy Depletion Possibility of Subbalanced Energy Depletion Novel Nonuniform Node Distribution Strategy and q-switch Routing Simulation

3. Energy Hole Problem in Sensor Network Energy hole: Unbalanced energy utilization Some nodes deplete their power more quickly Sink Energy hole Sink Energy hole Sink

4. Related Work Approaches that have been proposed to mitigate the energy hole problem Sink mobility Multiple sinks Hierarchical deployment Clustering Non-uniform initial energy budgets Non-uniform node distribution The objective of this paper

5. Contributions of this paper 1. Prove that balanced energy utilization is impossible for many-to-one traffic pattern. 2. Prove that subbalanced energy utilization is possible 3. Propose a nonuniform node deployment strategy 4. Propose a q-switch routing

6. Assumptions and Network Model Assume that all the nodes are deployed in a circular area with a radius R The width of each corona is 1 unit length Maximum transmission range is 1 unit length Nodes belonging to a corona will forward data generated by both themselves and nodes from coronas

7. Assumptions and Network Model Assume that each sensor node generates and sends L bits of data per unit time Regular reporting The initial energy of each sensor is  Sending 1 bit costs e 1 units of energy Receiving 1 bit costs e 2 units of energy

8. Energy Consumption N i : the number of nodes in C i E i : the energy consumed per time unit by nodes in C i

9. Balanced v.s. Subbalanced

10. Impossibility of Balanced Energy Depletion Proof If balanced energy depletion is achieved, then Average energy consumption per node

11. Impossibility of Balanced Energy Depletion

12. Subbalanced Energy Depletion Proof: If the network achieves the subbalanced energy depletion Average energy consumption per node

13. Subbalanced Energy Depletion

14. the number of nodes in coronas increases in geometric progression with a common ratio of q

15. Nonuniform Node Distribution -- Subbalanced Energy Depletion 816 48 144 q=3

16. Nonuniform Node Distribution -- Subbalanced Energy Depletion Proof

17. Nonuniform Node Distribution -- Subbalanced Energy Depletion

18. Nonuniform Node Distribution Strategy The number of nodes in C i Subbalanced Energy Depletion

19. Nonuniform Node Distribution Strategy

20. q-Switch Routing

21. Simulation

28. Conclusion This paper explored the theoretical aspects of the nonuniform node distribution strategy in WSNs. Although it is impossible to achieve balanced energy depletion, subbalanced energy depletion in the network is possible.