1. Mobile Filtering for Error-Bounded Data Collection in Sensor Networks Dan Wang Hong Kong Polytechnic Univ. Jianliang Xu ∗ Hong Kong Baptist Univ. Jiangchuan Liu, Feng Wang † Simon Fraser University Int'l Conference on Distributed Computing Systems (ICDCS 2008)

2. Outline Previews Introduction Mobile Filtering Problem System Model Mobile Filtering Algorithms Chain Topology Cross Chain Topology (Multi-Chain Trees) General Trees Simulations Conclusion

3. Previews Precision Allocation Problem X. Tang and J. Xu, “ Extending Network Lifetime for Precision-Constrained Data Aggregation in Wireless Sensor Networks ” (INFOCOM ’ 06). Optimizing Lifetime for Continuous Data Aggregation With Precision Guarantees in Wireless Sensor Networks. (IEEE Trans. on Networking) [PowerPoint]PowerPoint [EZLMS]EZLMS

4. Data Collection with Precision- Guarantee 20->20.222 18->19 20->19.8 20221920 1822 AVERAGE 2020.3 20221820 221820 1822 Time t 20 Time t+1 Total Error bound: 3 o C Error bound of each sensor : 0.5 o C 20 Approximate: 20.15 Real: 20.16

5. Precision Allocation -- Stationary The problem is: How to allocate user-specified precision among sensor nodes such that the network lifetime is maximized? Given the error bound: E e1e1 e2e2 e3e3 e4e4 e5e5 e6e6 Objective: Maximize network lifetime Subject to:

6. Mobile Filtering Problem

7. System Model 1. No data Aggregation -- target at collecting raw data. 2. Error measurement

8. System Model s1 s0 s3 s2 3 1.5 3 3 2 2, 3

9. Network Model (a) chain topology(b) multi-chain topology (c) cross multi-chain topology

10. Operations of a Sensor Node Processing state Listening state ……… Sleeping state

12. Optimal Solution for Chain Topology --- Dynamic Programming Assume all data changes are known a priori. Offline version

14. Greedy Online Heuristic Thresholds T R : decide if the filter is sent or not. T S : decide if a data change is sent or not.

15. Multi-chain Topology e 12 e8e8 e4e4 123n Given the error bound: E e1e1 e2e2 e n-1 enen Objective: Maximize network lifetime Subject to: …

16. Cross Multi-chain Topology -- General Tree

17. Simulations Setup Two data sets Synthetic data trace Real data trace (dew-point), LEM Three topologies Chain topology Cross multi-chain topology Grid topology

18. Chain Topology

19. Cross Multi-chain Topology

20. Filter Re-allocation Period

21. Precision -- Grid Topology

22. Conclusion This paper proposed a novel mobile filtering scheme for error-bounded non- aggregate data collection in sensor networks. By exploring the migration of filters, a mobile filter extracts and relays unused filters in the network to suppress as many data update reports as possible.