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Wireless Sensor Networks Self-Healing

Wireless Sensor Networks Self-Healing. Professor Jack Stankovic University of Virginia 2005. WSN Property. Unattended long-term operation System Initialization Set system parameters Adapt to Wireless communication changes Adapt to environmental changes Impact on sensor thresholds, etc.

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Wireless Sensor Networks Self-Healing

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  1. Wireless Sensor NetworksSelf-Healing Professor Jack Stankovic University of Virginia 2005

  2. WSN Property • Unattended long-term operation • System Initialization • Set system parameters • Adapt to Wireless communication changes • Adapt to environmental changes • Impact on sensor thresholds, etc. • Adapt to failures • Adapt to workload changes • Adapt to power reductions

  3. Self-Healing • One aspect of self-* system • Needs self-monitoring • Self-organizing • Self-managing • Self-calibration (turn-key system?) • Self-power management • … • Called Autonomic Computing

  4. Self-Healing • Relates to Fault Tolerance • Mask (correct) an error • ECC • Are you healed with respect to that error? • Yes for that error, but maybe not the cause! • Detect an error • Lost message • Re-send message • Ignore error (design for it) • Robustness - Act in presence of error (are you healed)? • Example: WSN still works if 20% of nodes are dead

  5. Self-Healing • Detect and heal • Example: Detect neighbor is “dead”, try restarting it and if successful -> healed • From a system perspective • Wide spectrum of capabilities • Not binary

  6. Self-Healing • In Localization • Heal: If node fails to obtain location during walking GPS, it gets info from neighbors and uses tri-lateration • Heal: A node detects that it lost its localization information, then re-determines it from its neighbors

  7. Recall APIT Algorithm Green- Anchors • Assumption: An area covered with heterogeneous nodes. • Anchor nodes equipped with high-powered transmitter. • Location information obtained from GPS. • Location estimation by Area-based Approach. • Narrow down the location of one node by deciding its presence inside or outside the triangles formed by the anchors. A Estimated Location Example: 14 anchors, but There are 100s of nodes like A

  8. Self-Healing • In Routing • Multiple parents in backbone tree • If detect one parent is dead, use the other • Local decision on choosing alternative parent is fast • Heal: Re-create n-parent tree on system rotation • In MAC • Retransmit lost packet • Heal: Enough lost packets -> change power level or other thresholds

  9. Self-Healing • In System Initialization • Each phase is coordinated and sequential • If a node is not in-step it becomes silent • Heal: Silent node (possibly) becomes active at next system rotation

  10. Time-Driven System Operation

  11. Self-Healing • In Wakeup • Decentralized and if some nodes fail to wake-up it is not a problem because many others will be awake • Heal: If it keeps happening then perhaps increase wakeup preamble and if this works then the wakeup has been healed

  12. Duty Cycle Preamble W W

  13. Self-Healing • In Sensing • Fail-stop – use of many sensors in WSN and since targets move, problems are masked (robust) • Heal: Byzantine failure – detect that a node is continuously reporting and shut it down • In Tracking • If group leader fails • Heal: Info is still with the group members and is passed to next leader

  14. Group Management (Tracking) Base Station

  15. Underlying Self-Healing in WSN • Limited Effect • Clock sync, neighbor discovery, etc. are highly decentralized and local. Single node failures (hopefully) only affect that node and do not propagate to the rest of the network.

  16. Self-Healing Mechanism • System Rotation • Can correct many issues • Can be executed based on time • Could be extended to re-run when many failures are detected, BUT this means extra detection messages which affects lifetime and stealthiness!

  17. Security in WSN • Solutions from the start • System must operate in presence of faults AND attacks • Framework for security updates as attacks evolve over time • Solution: Adaptable Self-Healing as Security Support in Wireless Sensor Networks

  18. Confluence of Techniques • Self-Healing • Aspects • Decentralized control with diversity • Wireless downloads

  19. Adaptive Self-Healing/ Aspects Self-Healing Component-Based WSN Partition M O N I T O R Routing Advice Point Cuts Download New Entities

  20. Decentralized Control • Redundancy • Mask faults • Uniformity a problem • Diversity

  21. Wireless Download • New executables (or WSN individual components) • Includes monitoring • New Join Points and Point Cuts • New Advice

  22. Summary • Unattended operation over long lifetime • Require self-* • Good software design and implementation • Good FT techniques • Security attack models and healing • Denial of Service • Mis-information (may be of more use in some situations)

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