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STDCS
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STDCS

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  1. STDCS: A Spatio-Temporal Data-Centric Storage Scheme For Real-Time Sensornet Applications Mohamed Aly (University of Pittsburgh & Yahoo, Inc.) In collaboration with Anandha Gopalan (University of Pittsburgh, Imperial College) and Jerry Zhao, Adel Youssef (Google, Inc.)
  2. Motivation: Real-Time Geo-Centric Sensor Network Applications <ul><li>Globally deployed sensor around the globe. </li></ul><ul><li>Clusters of sensors forming networks. </li></ul><ul><li>Mobile users roaming across the networks. </li></ul><ul><li>Real-time geo-centric ad-hoc queries issued from within or nearby the queried area. </li></ul><ul><li>The sensor network is responsible of answering these queries directly from the sensors rather than from base stations. </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Bronx Zoo cluster. </li></ul></ul><ul><ul><li>Disaster management cluster. </li></ul></ul>
  3. Motivation: Real-Time Geo-Centric Sensor Network Applications
  4. Data Storage Options in Sensor Networks <ul><li>Base Station Storage: </li></ul><ul><ul><li>Events are sent to base stations where queries are issued and evaluated. </li></ul></ul><ul><ul><li>Best suited for continuous queries. </li></ul></ul><ul><li>In-Network Storage (INS): </li></ul><ul><ul><li>Events are stored in the sensor nodes. </li></ul></ul><ul><ul><li>Best suited for ad-hoc queries. </li></ul></ul><ul><ul><li>All previous INS schemes were Data-Centric Storage (DCS) schemes. </li></ul></ul>
  5. In-Network Data-Centric Storage (DCS) <ul><li>Mainly to answer range queries. </li></ul><ul><li>Quality of Data (QoD) of ad-hoc queries. </li></ul><ul><li>Assign a value-range of readings for each sensor. </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Distributed Hash Tables (DHT) [Shenker et. al., HotNets’02] </li></ul></ul><ul><ul><li>Geographic Hash Tables (GHT) [Ratnasamy et. al., WSNA’02] </li></ul></ul><ul><ul><li>Distributed Index for Multi-dimensional data (DIM) [Li et. al., SenSys’03, Aly et. al., DMSN’05, MOBIQUITOUS’06] </li></ul></ul><ul><ul><li>K-D Tree based Data-Centric Storage (KDDCS) [Aly et. al., CIKM’06] </li></ul></ul>
  6. STDCS Overview <ul><li>Motivation: </li></ul><ul><ul><li>No previous INS schemes adopting geo-centric storage. </li></ul></ul><ul><ul><li>Expected techniques may be: </li></ul></ul><ul><ul><ul><li>Local storage. </li></ul></ul></ul><ul><ul><ul><li>Spatial storage </li></ul></ul></ul><ul><li>Design Goal: </li></ul><ul><ul><li>Load-Balancing of storage load among sensors </li></ul></ul><ul><li>Differences from previous schemes: </li></ul><ul><ul><li>Temporally evolving spatial indexing scheme to balance query load among sensors. </li></ul></ul><ul><ul><li>Dynamic query hotspot detection and decomposition. </li></ul></ul>
  7. Roadmap <ul><li>Motivation: Real-Time Geo-Centric applications. </li></ul><ul><li>Background: Data-Centric Storage (DCS). </li></ul><ul><li>Problem Statement: Real-Time Geo-Centric Storage. </li></ul><ul><li>Scheme Overview: STDCS. </li></ul><ul><li>STDCS Components </li></ul><ul><ul><li>Local Virtual address assignment </li></ul></ul><ul><ul><li>Spatio-Temporal data indexing. </li></ul></ul><ul><ul><li>Point-to-point data delivery. </li></ul></ul><ul><ul><li>Query processing. </li></ul></ul><ul><ul><li>Adaptive hotspot decomposition. </li></ul></ul><ul><li>Experimental Results </li></ul><ul><li>Conclusions </li></ul>
  8. STDCS Components: Local Virtual Address Assignment
  9. STDCS Components: Spatio-Temporal Data Indexing
  10. STDCS Components: Reading Delivery and Querying
  11. STDCS Components: Adaptive Hotspot Decomposition <ul><li>Motivation: </li></ul><ul><ul><li>Dynamic query hotspots as time progresses. </li></ul></ul><ul><li>Observation: </li></ul><ul><ul><li>Recurrent querying scenarios across the day, the week, etc. </li></ul></ul><ul><li>Technique: </li></ul><ul><ul><li>Continuously keeping track of hotspots using the Average Querying Frequency (AQF) metric. </li></ul></ul><ul><ul><li>Dynamically chaning the switching time to decompose hotspots. </li></ul></ul>
  12. Roadmap <ul><li>Motivation: Real-Time Geo-Centric applications. </li></ul><ul><li>Background: Data-Centric Storage (DCS). </li></ul><ul><li>Problem Statement: Real-Time Geo-Centric Storage. </li></ul><ul><li>Scheme Overview: STDCS. </li></ul><ul><li>STDCS Components </li></ul><ul><ul><li>Local Virtual address assignment </li></ul></ul><ul><ul><li>Spatio-Temporal data indexing. </li></ul></ul><ul><ul><li>Point-to-point data delivery. </li></ul></ul><ul><ul><li>Query processing. </li></ul></ul><ul><ul><li>Adaptive hotspot decomposition. </li></ul></ul><ul><li>Experimental Results </li></ul><ul><li>Conclusions </li></ul>
  13. Simulation Description <ul><li>Compare: STDCS, local storage, spatial indexing. </li></ul><ul><li>A cluster of stationary sensors (with random locations). </li></ul><ul><li>Each sensor senses a reading each 10 min. </li></ul><ul><li>Sensor reading = 1 packet. </li></ul><ul><li>Sensor capacity = 20 readings (packets) </li></ul><ul><li>Multiple mobile users. </li></ul><ul><li>A query: random sensor, radius, and type. </li></ul><ul><li>Two phases: initialization (3 hours of readings) & running (1 day of readings and queries). </li></ul><ul><li>Metrics: throughput, energy level, node deaths. </li></ul>
  14. Experimental Results: STDCS vs. Query Hotspots
  15. Experimental Results: STDCS vs. Query Hotspots
  16. Experimental Results: Switching Time Effect
  17. Experimental Results: Switching Time vs. Node Deaths
  18. Experimental Results: Adaptive Hotspot Decomposition
  19. Conclusions <ul><li>STDCS: A real-time geo-centric data storage scheme. </li></ul><ul><li>A new concept of spatio-temporal data indexing. </li></ul><ul><li>Ability to dynamically cope with dynamic loads and query hotspots. </li></ul>
  20. Acknowledgment <ul><li>This work has been partly supported by: </li></ul><ul><ul><li>Google, Inc. </li></ul></ul><ul><ul><li>The “Secure CITI: A Secure Critical Information Technology Infrastructure for Disaster Management (S-CITI)” project funded through the ITR Medium Award ANI-0325353 from the National Science Foundation (NSF). For more information, please visit: </li></ul></ul><ul><ul><ul><li>http://www.cs.pitt.edu/s-citi/ </li></ul></ul></ul>
  21. Thank You Questions ?

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