On the Energy Hole Problem of Nonuniform Node Distribution in Wireless Sensor Networks

1. On the Energy Hole Problem of Nonuniform Node Distribution in Wireless Sensor Networks Xiaobing Wu, Guihai Chen State Key Laboratory for Novel Software Technology Nanjing University Sajal K. Das Department of Computer Science and Engineering The University of Texas at Arlington MASS 2006

2. Outline • Introduction • Theoretical Analysis of Nonuniform Node Distribution Strategy • Routing with A Nonuniform Node Distribution Strategy • Simulation Results • Conclusions

3. Sink Sensor Introduction • Nodes nearer the sink have to take heavier traffic load A B

4. Sink Sensor Introduction • Sensor nodes that are closer to sink consume their energy rapidly (Energy Hole Problem) • Network partition A B

5. Motivation and Goal • Motivation • Explore the theoretical aspectsof power balance problem in wireless sensor networkswith nonuniform node distribution • Goal • Propose a nodedistribution strategy to achieve a suboptimal balancedenergy depletion

6. Assumptions and Network Model • A circular area with a radius of R • Transmission range of all the nodes is fixed • Data can be transmitted to the next inner corona with one hop

7. Theoretical Analysis of Nonuniform Node Distribution Strategy • Ei : Energy consumed per unit time by the nodes in corona Ci • Ni : The number of nodes in the corona Ci • A node • Send one bit : e1 units of energy • Receive one bit : e2 units of energy • Generate and send L bits of data per unit time

8. The Impossibility of Balanced Energy Depletion of The Network Initial energy • A perfect and maximum energy efficiency is not achievable • Nodes in the corona CRonly need to transmit their own data

9. The Suboptimal Balanced Energy Depletion of The Network • Find that a balanced energy depletion among the coronas except the outmost one is possible

10. The Suboptimal Balanced Energy Depletion of The Network • The number of nodes in coronas varies with a geometric proportion from outer coronas to inner ones in the whole network

11. Routing with A Nonuniform Node Distribution Strategy • Assume the number of nodes in the coronas increases with geometric proportion • Each node in Ci+1 can communicate directly with q different nodes in Ci 32 16 8 4 64 q=2

12. Routing with A Nonuniform Node Distribution Strategy • In network initialization, nodes find their upstream node and their q relay candidates • The source node selects one relay node with maximum energy resource

13. Simulation Results

14. Simulation Results C6(4) C5(8) C4(16) C3(32) C2(64) C1 (128) Most nodes have little energy wasted

15. Simulation Results Small variances in the fragments

16. Simulation Results Simulated value q=2 Theoretical value q=2 Simulated value q=3 Theoretical value q=3 Residual energy ratios of different values of network radius and q

17. Conclusions • With the number of nodes in the coronas increasing from outer areas to inner ones with geometric proportion • The network achieves a high energy efficiency