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Sensor Networks Storage

Sensor Networks Storage. Sanket Totala Sudarshan Jagannathan. Outline. Introduction Storage Mechanisms Multi-Resolution Storage Two-Tier Storage Conclusion. Introduction. Sensor Nodes Low Memory Low Power Low processing capability Inapproachability Sensor Networks

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Sensor Networks Storage

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  1. Sensor Networks Storage Sanket Totala Sudarshan Jagannathan

  2. Outline • Introduction • Storage Mechanisms • Multi-Resolution Storage • Two-Tier Storage • Conclusion

  3. Introduction • Sensor Nodes • Low Memory • Low Power • Low processing capability • Inapproachability • Sensor Networks • Efficiency requirements • Highly dense

  4. Introduction • Sensor Storage • Large number of events • Query handling capability required • Streaming data • Aging mechanism • Data organization

  5. Sensor Network Storage - Mechanism • Centralized Storage • Central server • Ample power • Sufficient storage • Single point of failure • Fast Query processing • High communication • Sparse Networks • Infrequent events • Low Data Transfer • Scalability problems

  6. Sensor Network Storage - Mechanism • Distributed Storage • Storage at each node • Local computation • Scalable • Dense Networks • Frequent events • High Data Transfer • Slower Query processing • Flooding • Distributed Indexing • Drill-down querying

  7. Multi-Resolution Storage • Multi-Resolution summarization • Construct data summaries • Hierarchy construction • Drill-down query evaluation • Narrowing search space • Spatio-temporal compression • Data aging • Efficient storage utilization • Data Degradation

  8. Multi-Resolution summarization • Temporal Summarization • Exploits Temporal redundancy • Computation overhead • No communication overhead • Spatial Summarization • Exploits Spatial redundancy • Data Summarization every level • Hierarchy construction

  9. Drill-down query evaluation • Spatial compression • Finer data view with every level. • Reduced search cost • Query routing • Sub region selection • More accurate result

  10. Data Aging • Long deployment • Limited storage • Efficient resource utilization • Fast query processing • Accuracy • Higher level, Higher time periods

  11. Data Aging – Algorithms • Omniscient Algorithm • Data sets available • Full global knowledge required • Query specific • Training Algorithm • Data sets available • Data set partitioned • Training data (available during sensor deployment) • Test data • Greedy Algorithm • Data set unavailable • Assigns weights to data summaries

  12. Outline – Two Tier Sensor Storage • Design Considerations and Principles • System Design • Architecture • Data structures • Data Storage • Sensor Network Data Summarization • Conclusion

  13. Design Consideration and Principles • The Three-Tier Model • Bottom tier - Untethered sensor nodes • Middle tier - Tethered sensor proxies • Upper tier - Applications and user terminals

  14. Design Consideration and Principles • Principles • Store locally, access globally • Distinguish data from metadata • Provide data-centric query support

  15. Data Structures Used • Skip Graph • Ordered index • In-place indexing • Log n height • Probabilistic balance • Redundancy and resiliency

  16. Data Structures Used • Interval Skip Graph • Extends skip graphs to store intervals • Allows efficient searches • Complexity of search is O(log n) • Insertion cost of O(n) • Sparse Interval Skip Graph

  17. Data Storage • Local Storage at Sensors • Archival Stores: Collection of records • Interval skip graphs used • Efficient routing and query handling • Operations: Create, Read & Delete

  18. Sensor Data Summarization • Data summaries – bind the storage at the remote sensor and the index at the proxy • Each update from a sensor to the proxy includes • The summary • Time period corresponding to the summary • The start and end offsets for the flash archive

  19. Sensor Summarization • Adaptive Summarization • Balances the cost of sending updates against the cost of false positives • Summarization Parameters • The interval over which summaries of the data are constructed and transmitted to the proxy • The size of the application specific summary.

  20. Conclusion • Multi-tier nature of sensor networks • Large amounts of events and data • Lossy Approach • Two-Tiered Approach • Low overheads • Decentralized and Hierarchical storage • Possible Solution • Combine lossy nature of Multi-resolution with routing techniques of Two-tiered approach.

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