1. TRUST, Spring Conference, April 2-3, 2008 Taking Advantage of Data Correlation to Control the Topology of Wireless Sensor Networks Sergio Bermudez and Prof. Stephen Wicker School of ECE, Cornell University To be presented at the 15th International Conference on Telecommunications

2. TRUST, Spring Conference, April 2-3, 2008 Agenda Introduction – Motivation – Background Model and Results – Assumptions – Analysis Conclusions "Topology Control," Sergio Bermudez2

3. TRUST, Spring Conference, April 2-3, 2008 Introduction Application of wireless sensor network (WSN) – Power Grid – Water supply pipes Keep nodes in place for long periods Necessity to extend their lifetime Reducing their energy consumption "Topology Control," Sergio Bermudez3

4. TRUST, Spring Conference, April 2-3, 2008 Motivation Sleeping Schemes – reduce energy consumption Data aggregation – routing scheme with compression of correlated data "Topology Control," Sergio Bermudez4

5. TRUST, Spring Conference, April 2-3, 2008 Motivation Random Clustering – Data aggregation at cluster heads "Topology Control," Sergio Bermudez5

6. TRUST, Spring Conference, April 2-3, 2008 Conceptual idea Combination of approaches to extend the network lifetime Exploit data correlation to control the topology of a wireless network Application to monitor physical infrastructure – Modal vibration in structures, e.g. a girder "Topology Control," Sergio Bermudez6

7. TRUST, Spring Conference, April 2-3, 2008 Conceptual Idea – autonomous creation of clusters – scheduling algorithm within these clusters "Topology Control," Sergio Bermudez7

8. TRUST, Spring Conference, April 2-3, 2008 Proposed Scheme Active nodes and backup nodes – Active nodes form the active network Network Functional lifetime – network can carry-out useful operations Focus on network connectivity "Topology Control," Sergio Bermudez8

9. TRUST, Spring Conference, April 2-3, 2008 Proposed Scheme Two-step procedure: – Initial setup: clusters information obtained by the correlation of the sensed data – Organization: Sleeping Scheduling energy-efficient scheduling mechanism controls the underlying topology of the network Random value at deployment – Cluster formation Random scheduling – Energy saving "Topology Control," Sergio Bermudez9

10. TRUST, Spring Conference, April 2-3, 2008 Proposed Scheme Advantages – Localized protocol – Allows for continuous sensing Disadvantages – Applicable in environments with strong data correlation – Non-uniform energy depletion—secondary concern "Topology Control," Sergio Bermudez10

11. TRUST, Spring Conference, April 2-3, 2008 Assumptions Measurements are perfectly correlated within distance t c – spatial correlation Nodes are able to determine data correlation information Nodes distributed according to a Poisson spatial process with intensity  High density of node platforms Boolean communication model, radius r c Uniform energy depletion when a node is active "Topology Control," Sergio Bermudez11

12. TRUST, Spring Conference, April 2-3, 2008 Assumptions Cluster Formation – Based on the spatial correlation – Define Active and Backup nodes, with probability p a, p b Sleeping Scheduling – Random energy-efficient scheduling mechanism backup nodes belonging to a cluster go to sleep randomly and independently from each other – For network robustness the backup nodes wake up periodically, with low-duty cycle "Topology Control," Sergio Bermudez12

13. TRUST, Spring Conference, April 2-3, 2008 Analysis: network connectivity We get a Marked Poisson process – Active and Backup nodes, with probability pa, pb – Choose appropriate µ such that there is connectivity with high probability "Topology Control," Sergio Bermudez13

14. TRUST, Spring Conference, April 2-3, 2008 Results: network connectivity "Topology Control," Sergio Bermudez14 Connectivity as function of active nodes Connectivity as function of node density

15. TRUST, Spring Conference, April 2-3, 2008 Analysis: number of neighbors Distribution of nearest-neighbor distance Probability that exists a backup node as a neighbor for a j "Topology Control," Sergio Bermudez15

16. TRUST, Spring Conference, April 2-3, 2008 Results: number of neighbors "Topology Control," Sergio Bermudez16

17. TRUST, Spring Conference, April 2-3, 2008 Results: increase in lifetime "Topology Control," Sergio Bermudez17

18. TRUST, Spring Conference, April 2-3, 2008 Conclusions Approach to control the topology of wireless sensor networks by data correlation Increase of functional lifetime, relevant for the monitoring of physical infrastructure Future work: – Analysis with respect to other deployment distribution – Couple this scheme with mobile sensor networks "Topology Control," Sergio Bermudez18

19. TRUST, Spring Conference, April 2-3, 2008 Further Reading “Networking Wireless Sensors” B. Krishnamachari “A survey of Energy-Efficient scheduling mechanisms in sensor networks” L. Wang and Y. Xiao “The impact of spatial correlation on routing with compression in wireless sensor networks” S. Pattem, B. Krishnamachari, and R. Govindan "Topology Control," Sergio Bermudez19