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On-demand Time Synchronization  for Wireless Sensor Networks [Plan B project] Advised by: Prof. Tian He Presented by: Abhi...
Introduction <ul><li>Time synchronization </li></ul><ul><ul><li>middleware service </li></ul></ul><ul><ul><li>provides tim...
Introduction: applications <ul><li>Example Applications  </li></ul><ul><ul><li>Sniper detection </li></ul></ul><ul><ul><li...
Introduction: services <ul><li>Provide  time-reference  for some sensor node functions </li></ul><ul><ul><li>TDMA scheduli...
Time Synchronization: approaches <ul><li>Proactive techniques </li></ul><ul><ul><li>periodically synchronize the nodes </l...
Existing Techniques <ul><li>Several techniques </li></ul><ul><ul><li>application in post and pre-event scenarios </li></ul...
Existing Techniques [continued] <ul><li>RBS </li></ul><ul><ul><li>Receiver- receiver </li></ul></ul><ul><ul><li>Broadcast ...
Existing Techniques [continued] <ul><li>FTSP </li></ul><ul><ul><li>Broadcast-based </li></ul></ul><ul><ul><li>MAC time-sta...
Existing Techniques <ul><li>ETA </li></ul><ul><ul><li>State-of-art </li></ul></ul><ul><ul><li>Elapsed Time-of-Arrival prim...
Problem Statement <ul><li>How to minimize the cost of time-synchronization? </li></ul><ul><ul><li>Optimizing communication...
Motivation <ul><li>Reducing communication cost </li></ul><ul><ul><li>post-facto technique </li></ul></ul><ul><ul><li>cachi...
Assumptions <ul><li>Spatiotemporal events </li></ul><ul><ul><li>Adjacent nodes will detect the event </li></ul></ul><ul><u...
Sources of Error <ul><li>Time-reference communication </li></ul><ul><ul><li>Sources of delay in timestamp delivery </li></...
Proposed Approach  <ul><li>On-demand Time Synchronization Protocol </li></ul><ul><ul><li>Post-facto approach </li></ul></u...
Approach Details <ul><li>Seeker Determination </li></ul><ul><ul><li>Data > threshold value </li></ul></ul><ul><ul><li>Prev...
Approach Details <ul><li>Provider determination </li></ul>
Approach Details: time reference exchange <ul><li>Time-Synchronization Messaging </li></ul><ul><ul><li>3-way handshake </l...
Approach Details [continued] <ul><li>Skew Calculation </li></ul>
Approach Details [continued] <ul><li>Offset Calculation </li></ul>
Implementation: platform <ul><li>Platform </li></ul><ul><li>Simulator </li></ul>
Implementation: system design <ul><li>Modules: </li></ul><ul><ul><ul><li>TimeLibService </li></ul></ul></ul><ul><ul><ul><l...
Implementation: system design [continued] <ul><li>Diagram </li></ul>
Analysis: applications <ul><li>Accuracy requirement </li></ul><ul><ul><li>Habitat monitoring  : order of seconds </li></ul...
Results <ul><li>Data Analysis for Real Time Experiment </li></ul><ul><ul><li>Seismic activity detection </li></ul></ul><ul...
Results: Data Analysis for Real Time Experiment <ul><li>Analysis of Data from Seismic Activity Detection </li></ul><ul><ul...
Results: real-time data analysis <ul><li>Communication complexity for various skew errors-rates over the experiment-span <...
Results: tossim simulation <ul><li>Average error per hop </li></ul><ul><ul><li>Error per hop (for first hop): 4.52  millis...
Results: performance with frequency
Results: performance with event density
Results: miscellaneous observations <ul><li>Congestion </li></ul><ul><li>Delivery probability </li></ul>
Drawbacks
Discussion
Further Work
?
 
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On Demand Time Sychronizaton for Wireless Sensor Networks-november2009

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Masters Project on New technique for time synchronization in an on-demand fashion to optimize the energy requirement.

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Transcript of "On Demand Time Sychronizaton for Wireless Sensor Networks-november2009"

  1. 1. On-demand Time Synchronization for Wireless Sensor Networks [Plan B project] Advised by: Prof. Tian He Presented by: Abhishek Rawat
  2. 2. Introduction <ul><li>Time synchronization </li></ul><ul><ul><li>middleware service </li></ul></ul><ul><ul><li>provides time-reference for nodes </li></ul></ul><ul><li>Time reference </li></ul><ul><ul><li>Global </li></ul></ul><ul><ul><li>Peer-node </li></ul></ul>
  3. 3. Introduction: applications <ul><li>Example Applications </li></ul><ul><ul><li>Sniper detection </li></ul></ul><ul><ul><li>Seismic activity detection </li></ul></ul><ul><ul><li>Structural monitoring </li></ul></ul><ul><ul><li>Object tracking </li></ul></ul><ul><ul><li>Habitat Monitoring </li></ul></ul>
  4. 4. Introduction: services <ul><li>Provide time-reference for some sensor node functions </li></ul><ul><ul><li>TDMA scheduling </li></ul></ul><ul><ul><li>LPL communication </li></ul></ul><ul><ul><li>Distributed processing </li></ul></ul><ul><ul><li>Aggregation techniques </li></ul></ul>
  5. 5. Time Synchronization: approaches <ul><li>Proactive techniques </li></ul><ul><ul><li>periodically synchronize the nodes </li></ul></ul><ul><ul><li>periodicity based on precision requirement </li></ul></ul><ul><ul><li>Reactive techniques </li></ul></ul><ul><ul><li>Actuated by the event </li></ul></ul><ul><ul><li>Periodicity based on event frequency </li></ul></ul>
  6. 6. Existing Techniques <ul><li>Several techniques </li></ul><ul><ul><li>application in post and pre-event scenarios </li></ul></ul><ul><ul><li>Varying accuracy and communication cost </li></ul></ul><ul><li>Notable techniques </li></ul><ul><ul><li>RB </li></ul></ul><ul><ul><li>TPSN </li></ul></ul><ul><ul><li>FTSP </li></ul></ul><ul><ul><li>ETA </li></ul></ul>
  7. 7. Existing Techniques [continued] <ul><li>RBS </li></ul><ul><ul><li>Receiver- receiver </li></ul></ul><ul><ul><li>Broadcast based </li></ul></ul><ul><li>TPSN </li></ul><ul><ul><li>Sender-sender </li></ul></ul><ul><ul><li>MAC time-stamping </li></ul></ul>
  8. 8. Existing Techniques [continued] <ul><li>FTSP </li></ul><ul><ul><li>Broadcast-based </li></ul></ul><ul><ul><li>MAC time-stamping and skew calculation </li></ul></ul><ul><ul><li>High accuracy </li></ul></ul><ul><ul><li>Reactive technique </li></ul></ul><ul><ul><li>Hardware calibration </li></ul></ul>
  9. 9. Existing Techniques <ul><li>ETA </li></ul><ul><ul><li>State-of-art </li></ul></ul><ul><ul><li>Elapsed Time-of-Arrival primitive </li></ul></ul><ul><ul><li>Reduced communication cost </li></ul></ul><ul><ul><li>Elapsed time in data-item-no separate time-synchronization messaging </li></ul></ul><ul><ul><li>Skew calculation is a problem </li></ul></ul>
  10. 10. Problem Statement <ul><li>How to minimize the cost of time-synchronization? </li></ul><ul><ul><li>Optimizing communication requirement with desired accuracy </li></ul></ul>
  11. 11. Motivation <ul><li>Reducing communication cost </li></ul><ul><ul><li>post-facto technique </li></ul></ul><ul><ul><li>caching: time-reference present in network </li></ul></ul>
  12. 12. Assumptions <ul><li>Spatiotemporal events </li></ul><ul><ul><li>Adjacent nodes will detect the event </li></ul></ul><ul><ul><li>Time reference would be available in mearby nodes </li></ul></ul><ul><ul><li>Unicast messaging will reduce communication cost </li></ul></ul>
  13. 13. Sources of Error <ul><li>Time-reference communication </li></ul><ul><ul><li>Sources of delay in timestamp delivery </li></ul></ul><ul><ul><ul><li>Send/Receive Time </li></ul></ul></ul><ul><ul><ul><li>Access Time </li></ul></ul></ul><ul><ul><ul><li>Transmission and Reception Time </li></ul></ul></ul><ul><ul><ul><li>Propagation Time </li></ul></ul></ul><ul><ul><ul><li>Interrupt Handling </li></ul></ul></ul><ul><ul><ul><li>Encoding/Decoding Time </li></ul></ul></ul><ul><ul><ul><li>Byte Alignment </li></ul></ul></ul><ul><ul><ul><li>Hardware Calibration/Clock-Skew </li></ul></ul></ul>
  14. 14. Proposed Approach <ul><li>On-demand Time Synchronization Protocol </li></ul><ul><ul><li>Post-facto approach </li></ul></ul><ul><ul><li>Primitive: seeker provider determination post-event </li></ul></ul><ul><ul><li>Time-reference exchange using 3-way handshake </li></ul></ul><ul><ul><li>Clock offset and Clock skew rate calculation </li></ul></ul>
  15. 15. Approach Details <ul><li>Seeker Determination </li></ul><ul><ul><li>Data > threshold value </li></ul></ul><ul><ul><li>Previous time reference : Expired !!! </li></ul></ul>
  16. 16. Approach Details <ul><li>Provider determination </li></ul>
  17. 17. Approach Details: time reference exchange <ul><li>Time-Synchronization Messaging </li></ul><ul><ul><li>3-way handshake </li></ul></ul>Tx2 Tx1 initMsg t1 provider-node t0 t2 t5 t4 t3 seeker-node Fig2. Messages exchanged during time-synchronization between two nodes
  18. 18. Approach Details [continued] <ul><li>Skew Calculation </li></ul>
  19. 19. Approach Details [continued] <ul><li>Offset Calculation </li></ul>
  20. 20. Implementation: platform <ul><li>Platform </li></ul><ul><li>Simulator </li></ul>
  21. 21. Implementation: system design <ul><li>Modules: </li></ul><ul><ul><ul><li>TimeLibService </li></ul></ul></ul><ul><ul><ul><li>TimeSyncModule </li></ul></ul></ul><ul><ul><ul><li>TimeSyncCtrl </li></ul></ul></ul><ul><ul><ul><li>TimeSyncCommModule </li></ul></ul></ul><ul><ul><ul><li>Routing Module </li></ul></ul></ul><ul><ul><ul><li>SenseDB </li></ul></ul></ul>
  22. 22. Implementation: system design [continued] <ul><li>Diagram </li></ul>
  23. 23. Analysis: applications <ul><li>Accuracy requirement </li></ul><ul><ul><li>Habitat monitoring : order of seconds </li></ul></ul><ul><ul><li>Seismic activity detection : order of 10 milliseconds </li></ul></ul><ul><ul><li>Sniper detection : order of 1 millisecond </li></ul></ul><ul><ul><li>Structural monitoring : order of 10 milliseconds </li></ul></ul>
  24. 24. Results <ul><li>Data Analysis for Real Time Experiment </li></ul><ul><ul><li>Seismic activity detection </li></ul></ul><ul><li>Data Analysis from TOSSIM based simulations </li></ul><ul><ul><li>Error- analysis </li></ul></ul><ul><ul><li>Communication cost with event frequency </li></ul></ul><ul><ul><li>Communication cost with event density </li></ul></ul><ul><ul><li>Delivery success rate </li></ul></ul>
  25. 25. Results: Data Analysis for Real Time Experiment <ul><li>Analysis of Data from Seismic Activity Detection </li></ul><ul><ul><li>21 days – 230 events </li></ul></ul><ul><ul><li>60 seconds per activity </li></ul></ul><ul><ul><li>Sampling frequency of 100 Hz. </li></ul></ul>
  26. 26. Results: real-time data analysis <ul><li>Communication complexity for various skew errors-rates over the experiment-span </li></ul>
  27. 27. Results: tossim simulation <ul><li>Average error per hop </li></ul><ul><ul><li>Error per hop (for first hop): 4.52 milliseconds </li></ul></ul><ul><ul><li>Error per subsequent hop : 1.24 milliseconds </li></ul></ul>
  28. 28. Results: performance with frequency
  29. 29. Results: performance with event density
  30. 30. Results: miscellaneous observations <ul><li>Congestion </li></ul><ul><li>Delivery probability </li></ul>
  31. 31. Drawbacks
  32. 32. Discussion
  33. 33. Further Work
  34. 34. ?
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