Wireless Sensor Networks Self-Healing
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Wireless Sensor Networks Self-Healing Professor Jack Stankovic University of Virginia 2005
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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. - PowerPoint PPT Presentation
Transcript of Wireless Sensor Networks Self-Healing
Wireless Sensor Networks
Self-Healing
Professor Jack Stankovic
University of Virginia2005
WSN PropertyWSN 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-HealingSelf-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-HealingSelf-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
Self-Healing 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
Self-HealingSelf-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
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
A
Green-Anchors
Example: 14 anchors, butThere are 100s of nodes like A
Self-HealingSelf-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
Self-HealingSelf-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
Time-Driven System OperationTime-Driven System Operation
RESET
Phase I
System Initialization
Phase III
Localization
Phase VNetwork Partition & Diffusion
Tree Constrcution
Phase VI
Sentry Selection
Phase VII
Health Report
StartPhase VIII
Power Mgmt
Event Tracking
Phase II
Time SyncPhase IV
Asymmetri Detection
Phase VIII
Event Tracking
Power Mgmt
Dormant Section
Tripwire Section
Wakeup Service
Self-HealingSelf-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
Duty CycleDuty Cycle
W
W
Preamble
Self-HealingSelf-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
Group Management (Tracking)
Group Management (Tracking)
Base Station
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 MechanismSelf-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 WSNSecurity 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
Partition
Routing
AdvicePoint Cuts
Download New Entities
Component-Based WSN
Self-Healing
MONITOR
Decentralized ControlDecentralized Control
• Redundancy• Mask faults• Uniformity a problem
– Diversity
Wireless DownloadWireless Download
• New executables (or WSN individual components)– Includes monitoring
• New Join Points and Point Cuts• New Advice
SummarySummary
• 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)
