Transcript Sensor Networks

Sensor Networks
by
K. Subrahmanya Sreshti
(05IT6004)
Under the Guidance of
Prof. Shamik Sural
School of Information Technology
Indian Institute of Technology, Kharagpur.
Technical Terms
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SINA – Software Information Network Architecture.
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Beacons.
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TinyOS – Tiny Micro-threading Operating System.
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SPIN – Sensor Protocols for Information via Navigation.
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Contents
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Introduction
 Overview of Architecture and Operating System
 Energy Efficient methods
 Localization
 Routing
 Applications (Some systems which make use of sensor
networks)
 Sensor Network simulators
 Conclusion
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Introduction
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Definition:
– Sensor networks are dense wireless networks of small,
low-cost sensors, which collect and disseminate
environmental data.
– Used for monitoring and controlling of physical environments
from remote locations with better accuracy.
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Introduction (Cont…)
Earlier sensor networks…
 Now, sensor networks…
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Why distributed, wireless sensing???
– Closer placement.
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Depends upon:
– Dense Deployment.
– Co-ordination among the nodes.
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Features
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Local Processing.
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Wireless Communication.
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Complete system on Chip.
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Integrated Low-power communication.
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Integrated Low-power transducers.
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Focus Is On…
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Energy and computational constraints.
– Energy Efficiency.
– Localization algorithms.
– Routing.
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2. Architecture
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Characteristics:
– Small physical size and low power consumption.
– Concurrency intensive operation.
– Limited physical parallelism and controller hierarchy.
– Diversity in design and usage.
– Robust Operation.
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Sensor Information Networking Architecture – A middle ware.
– Issue queries and command tasks into.
– Collects replies and results from.
– Monitor changes.
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Hierarchical Clustering.
Attribute-based naming.
Location Awareness.
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2. Architecture (Cont…)
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Data sheets.
Sensor Query and Tasking Language (SQTL).
– Interface between sensor application and SINA middleware.
– getTemperature, turnON, isNeighbor, getPosition, tell,
execute, etc.
– Event handling: Receive, every, expire.
– Software Execution Engine ( ALL, NEIGHBORS, etc )
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Information Gathering
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Sampling Operation (Adaptive Probability Response).
 Self-Orchestrated Operation.
 Diffused Computation Operation.
 Internetworking between a Mobile User and Stationary
Network.
– Tracking the mobile User.
– Progressive footprint chaining.
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2. Architecture (Cont…)
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Hardware Organization.
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Processor and co-processor.
Provide interfaces to sensing devices (light, temperature, etc).
Designed to work in three different modes (idle, power down, power save).
Three leads available.
Power Characteristics.
Why an OS?
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Requirement of an OS which can perform the tasks.
Effective usage of hardware.
Support concurrent-intensive operation.
Unused CPU cycles are spent in sleep mode.
Achieve robustness.
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2. Architecture (Cont…)
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TinyOS design.
– Event modeling.
– A stack based threaded approach.
– Two level scheduling.
– Components.
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Set of command handlers.
Set of event handlers.
An encapsulated fixed size frames.
Bundle of simple tasks.
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Figure 1: http://citeseer.ist.psu.edu/382595.html
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3. Energy Efficiency
Computing Subsystem. – microprocessor.
 Communication subsystem. – radio.
 Sensing subsystem – sensors and actuators.
 Power Supply – consists of a battery.
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Solution.
– Develop methodologies which are energy aware.
– Distribution of traffic.
– Residual Energy Scan (eScan) – by Younggang Zaho.
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4. Localization
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Nodes are in general deployed into an unplanned
infrastructure (no priori knowledge).
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Problem of estimating the spatial co-ordinates is referred
to as Localization (generally done by trilateration).
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Initial high-level nodes (beacons) broadcasts their
address. (Proximity based Localization).
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Multilateration (iterative process).
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Trilateration/multilateration
A
A
A
B
B
C
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4. Localization (Cont…)
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Fine – grained.
– Timing.
– Signal Strengths.
– Signal Pattern Matching.
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Pre-scanning takes place. A central system assigns a unique signature
to each square in the location grid.
Coarse – grained.
– Proximity based Localization. Nodes should adopt themselves to avoid to
available reference points.
– Connectivity metric=(tot. no. of signals received)/(tot. no. of signals sent).
– Node’s position is calculated by centroid of all reference points.
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Suggested Alg. For Beacons
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Random
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Max
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Grid
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Heap (Selective Turning off BEacons)
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5. Routing
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Implosion
Ad-hoc protocols
– Proactive – static: maintains a routing table.
– Reactive – dynamic: establishes when required.
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Negotiation based protocols
SPIN (meta-data) : uses ADV, REQ and DATA.
– SPIN – PP (point-to-point)
– SPIN – EC (energy conservative)
– SPIN – BC (broadcast)
– SPIN – RL
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5. Routing (Cont…)
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Directed diffusion.
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Attribute-value pairs are maintained.
Sink.
Interest cache.
Fields.
 Timestamp.
 Gradient – data rate.
 Duration – lifetime.
Energy Aware Routing.
– Destination initiative reactive protocol.
– Multiple good optimal paths are maintained.
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6. Applications
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Active Badge Location System.
Pin-point 3D-iD local positioning system.
Intelligence department.
Environmental monitoring.
Military purposes.
Gathering sensing information in inhospitable
locations.
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7. Sensor Network Simulator
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NS –2 ; written in c++ and oTCL.
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GloMoSim (Global Mobile Information System
Simulator); written in C and parsec.
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SensorSim;
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Challenges
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Ad hoc deployment
 Unattended Operation
 Untethered (Limited Energy resource)
 Dynamic Changes
Ultimate Struggle
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System Lifetime
 System robustness
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Conclusion
• Promising applications
• Evolving field
• Scope for lots of research
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References
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http://wwwcsif.cs.ucdavis.edu/~bharathi/sensor/survey.pdf
 http://ieeexplore.ieee.org/iel5/45/26953/01197877.pdf
 http://ieeexplore.ieee.org/iel5/98/20430/00944004.pdf
 http://citeseer.ist.psu.edu/382595.html
 http://www.research.rutgers.edu/~mini/sensornetworks.html
 http://www2.parc.com/spl/members/zhao/stanford-cs428/
 http://www.eng.auburn.edu/users/lim/sensit.html
 http://geometry.stanford.edu/member/guibas/
 http://pdos.csail.mit.edu/span/
 http://www.tinyos.net/
 http://bit.csc.lsu.edu/news/faculty-candidate.html
 http://www.janet.ucla.edu/WINS/
 http://www.cs.duke.edu/~alvy/courses/sensors/Papers.html
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Thank You
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