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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 NetworksSelf-Healing

Professor Jack Stankovic

University of Virginia


Wsn property
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

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

Self healing1

  • 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

Self healing2

  • 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

Self healing3

  • 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

Recall apit algorithm
Recall APIT Algorithm



  • 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.


Estimated Location

Example: 14 anchors, but

There are 100s of nodes like A

Self healing4

  • 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

Self healing5

  • 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

Self healing6

  • 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

Duty cycle
Duty Cycle




Self healing7

  • 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

Underlying self healing in wsn
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.

Self healing mechanism
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!

Security in wsn
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

Confluence of techniques
Confluence of Techniques

  • Self-Healing

  • Aspects

  • Decentralized control with diversity

  • Wireless downloads

Adaptive self healing aspects
Adaptive Self-Healing/ Aspects


Component-Based WSN











Point Cuts

Download New Entities

Decentralized control
Decentralized Control

  • Redundancy

  • Mask faults

  • Uniformity a problem

    • Diversity

Wireless download
Wireless Download

  • New executables (or WSN individual components)

    • Includes monitoring

  • New Join Points and Point Cuts

  • New Advice


  • 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)