1. On Achieving Maximum Network Lifetime Through Optimal Placement of Cluster-heads in Wireless Sensor Networks
High-Speed Networking Lab.
Dept. of CSIE, Fu-Jen Catholic University
Adviser: Jonathan C. Lu, Ph.D.
Speaker: Yen-Fong Wang

2. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

3. I. Abstract
In wireless sensor network, the network lifetime is an important issue when the size of the network is large
The cluster-heads near the sink get overloaded and drained out sooner
Formulate an optimization problem and find the optimum number of cluster-heads to be deployed and their optimum transmission ranges

4. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

5. II. Introduction There are two basic network architectures in WSN
Multi-hop
Cluster-heads
Multi-hop: The sensor nodes are homogeneous and they transmit data packets via intermediate sensor nodes in a multi-hop fashion to the sink
Cluster heads: The whole area is divided into a number of cluster regions
Cluster-heads reduce the number of transmissions by aggregating the sensed information thereby minimizing the energy dissipation in the network

6. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

7. III. Related work
The lifetime of the sensor nodes is balanced by varying the radio’s transmission range
Sensor nodes reach the cluster-head station using
Single-hop mode
Multi-hop mode
Hybrid communication mode
The cluster-heads
Gather the sensed information from sensor nodes
Perform the required computation
Have long transmission range than that of the sensor nodes

8. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

9. IV. OPC Algorithm
Places additional cluster-heads near the sink to handle the high load
Provides the optimum density and radio transmission range for the cluster-heads in order to achieve the maximum network lifetime with the minimum network cost
Network model
The network is divided into number of clusters
Cluster-heads transmit packets to the data sink in a multi-hop path via other cluster-heads
Sensor nodes communicate with their cluster-heads either in a single or multi-hop path

10. IV. Cluster architecture in wireless sensor network

11. IV. OPC Algorithm
Relationship between node density and transmission range
Optimum number of cluster-heads problem is non linear integer programming problem (NLP)

12. IV. OPC Algorithm Varying dense placement algorithm
The cluster-heads near the sink will run out of power sooner and reduce the network lifetime
Minimum number of cluster-heads required
: the minimum number of cluster-heads required
r : the transmission range for cluster-heads

13. IV. Varying dense placement of cluster-heads1 2 3 4 5 6

14. IV. OPC Algorithm
Cluster-heads can reduce the transmission range, in order to save energy

15. IV. OPC Algorithm
The hop distance between the sink and the border cluster- heads is N, where
The objective is to minimize the network cost is
K: the number of packets transmitted by a cluster-heads after collecting the data from sensor nodes

16. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

17. V. Simulation results Use GloMoSim simulator to simulate the results
Compared uniform dense placement (UDP), varying dense placement (VDP) and OPC algorithms in the network lifetime, collisions and latency
Simulation parameters
Network size (Terrain radius): 1000 – 2000 meters
Bandwidth: 48 kbps
Packet size 512 bytes
Transmission range (UDP/VDP): 200 meters
Transmission range (OPC): meters
MAC protocol: IEEE DCF

18. V. Network lifetime for different network sizes

19. V. Effect of varying traffic on collisions

20. V. Effect of varying traffic on latency

21. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

22. VI. Conclusion
The optimum number if cluster-heads required and their respective transmission ranges
This paper’s algorithm achieves the maximum network lifetime with the minimum network cost and less number of collisions

23. Outline Abstract Introduction Related work
Optimal placement of cluster-heads (OPC) algorithm
Simulation results
Conclusion
Reference

24. VII. Reference
On Achieving Maximum Network Lifetime Through Optimal Placement of Cluster-heads in Wireless Sensor Networks Dhanaraj, M.; Siva Ram Murthy, C.; IEEE International Conference on Communications, ICC `07.
24-28 June 2007