Distributed Clustering in Ad-hoc Sensor Networks: A Hybrid, Energy-Efficient Approach

1. Distributed Clustering in Ad-hoc Sensor Networks:A Hybrid, Energy-Efficient Approach Mulmedia and Mobile communications Laboratory 2004 / 4 / 20 박건우

2. Reference • Ossama Younis and Sonia Fahmy, “Distributed Clustering in Ad-hoc Sensor Networks:A Hybrid, Energy-Efficient Approach,” INFOCOMM 2004

3. Contents • Introduction • Problem Statement • The HEED Protocol • Performance Evaluation • Conclusion

4. Introduction(1/3) • Useful energy consumption • Transmitting/receiving data • Processing query requests • Forwarding queries/data • Wasteful energy consumption • Idle listening • Retransmitting • Overhearing • Generating/handling control packets

5. Introduction(2/3) • Hierarchical clustering - reduce useful energy consumption • Scalability • Efficient data aggregation • Routing protocols • The essential operation in clustering • Selecting a set of cluster heads

6. Introduction(3/3) • HEED (Hybrid Energy-Efficient Distributed clustering) • Distributing energy consumption • Terminating the clustering process within a constant number of iterations/steps • Reducing control overhead O(n) • Producing well-distributed cluster heads and compact clusters

7. Problem Statement(1/2) • Network Model • Quasi-stationary. • Energy consumption is not uniform for all nodes. • Nodes are location-unaware, i.e. no GPS service. • All nodes are equal. • Nodes are left unattended after deployment. • Fixed number of transmission power levels.

8. Problem Statement(2/2) • The Clustering Problem • Clustering is completely distributed. • Clustering terminates within a fixed number of iterations. • At the end of each Tcp, each node is either a cluster head, or a non-head node that belongs to exactly one cluster. • Clustering should be efficient. • Cluster heads are well-distributed over the sensor field.

9. The HEED Protocol • A. Clustering Parameters • Cluster header selection • Residual energy • Select an initial set of cluster heads • Intra-cluster “communication cost” - Break ties • Cost : function of density and power • Fixed power (optimal power) • Node degree - Load distribution • 1/(node degree) - Dense clusters • Variable power • Average minimum reachability power (AMRP)

10. The HEED Protocol • B. Protocol Operation • Clustering is triggered every Tcp+Tno seconds • (Tcp : clustering process time, Tno : network operation time) • Initialize • Repeat • Finalize

11. The HEED Protocol • B. Protocol Operation ->

12. The HEED Protocol • B. Protocol Operation // 1. cluster set이 존재할 경우 // 3. 자신이 cost가 가장 작은 node일 경우 // 9. Sch 없음. 자신이 CH가 됨 // 12. 첫 iteration에서 CHprob를 이용 // Sch로 속할 것인지 판단

13. The HEED Protocol • B. Protocol Operation // 주변에 CH존재 // 직접 CH가 됨 Phase II 에서 CHprevious = 1 인데도 is_final_CH = false 라는 말은 해당 node가 cluster head가 아니라는 것을 의미한다.

14. The HEED Protocol • C. Correctness and Complexity • Lemma 1: HEED terminates in Niter = O(1) iterations • Lemma 2: At the end of phase III of the HEED protocol, a node is either a cluster head or a regular node that belongs to a cluster • Lemma 3: HEED has a worst case processing time complexity of O(N) per node • Lemma 4: HEED has a worst case message exchange complexity of O(1) per node, i.e., O(N) in the network • Lemma 5: The probability that two nodes within each other’s cluster range are both cluster heads is small, i.e., cluster heads are well-distributed

15. The HEED Protocol • D. Inter-Cluster Communication • Lemma 6: Assume that N nodes are uniformly and independently dispersed at random in an area and the area is divided into square cells, then each cell contains at least one node (asymptotically almost surely) a.a.s. (i.e., the expected number of empty cells is zero) • Lemma 7: There exists at least one cluster head in any square cell area a.a.s. • Lemma 8: For any two cluster heads v1 and v2 in two neighboring areas A and B, v1 and v2 can communicate. • HEED produces a connected multi-hop cluster head graph (structure) a.a.s.

16. Performance Evaluation Max AMRP Min LEACH

17. Performance Evaluation AMRP Min Max LEACH

18. Performance Evaluation LEACH HEED

19. Conclusion • Energy-efficient distributed clustering approach for ad-hoc sensor networks • HEED (Hybrid, Energy-Efficient Approach) • Cluster heads are randomly selected based on their residual energy • Terminates in a constant number of iterations • Independent of the network diameter • HEED • energy efficiency, scalability, prolonged network lifetime, and load balancing