Sensor Networks

Sensor NetworksSensor Networks

UCE BURLA

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Technical TermsTechnical Terms SINA – Software Information Network Architecture.

Beacons.

TinyOS – Tiny Micro-threading Operating System.

SPIN – Sensor Protocols for Information via Navigation.

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ContentsContents

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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IntroductionIntroduction

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…)Introduction (Cont…)

Earlier sensor networks… Now, sensor networks…

Why distributed, wireless sensing???– Closer placement.

Depends upon:– Dense Deployment.– Co-ordination among the nodes.

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FeaturesFeatures

Local Processing.

Wireless Communication.

Complete system on Chip.

Integrated Low-power communication.

Integrated Low-power transducers.

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Focus Is On…Focus Is On…

Energy and computational constraints.

– Energy Efficiency.

– Localization algorithms.

– Routing.

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2. Architecture2. Architecture Characteristics:

– Small physical size and low power consumption.– Concurrency intensive operation.– Limited physical parallelism and controller hierarchy.– Diversity in design and usage.– Robust Operation.

Sensor Information Networking Architecture – A middle ware.– Issue queries and command tasks into.– Collects replies and results from.– Monitor changes.

Hierarchical Clustering. Attribute-based naming. Location Awareness.

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2. Architecture (Cont…)2. Architecture (Cont…)

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 GatheringInformation Gathering

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…)2. Architecture (Cont…) Hardware Organization.

– 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?– 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…)2. Architecture (Cont…) TinyOS design.

– Event modeling.– A stack based threaded approach.– Two level scheduling.– Components.

Set of command handlers. Set of event handlers. An encapsulated fixed size frames. Bundle of simple tasks.

04/20/23 Presentation on Sensor Networks 13Figure 1: http://citeseer.ist.psu.edu/382595.html

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3. Energy Efficiency3. Energy EfficiencyComputing Subsystem. – microprocessor.Communication subsystem. – radio.Sensing subsystem – sensors and actuators.Power Supply – consists of a battery.

Solution.– Develop methodologies which are energy aware.– Distribution of traffic.– Residual Energy Scan (eScan) – by Younggang Zaho.

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4. Localization4. Localization Nodes are in general deployed into an unplanned

infrastructure (no priori knowledge).

Problem of estimating the spatial co-ordinates is referred to as Localization (generally done by trilateration).

Initial high-level nodes (beacons) broadcasts their address. (Proximity based Localization).

Multilateration (iterative process).

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Trilateration/multilaterationTrilateration/multilateration

A A B

A B

C

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4. Localization (Cont…)4. Localization (Cont…) Fine – grained.

– Timing.– Signal Strengths.– Signal Pattern Matching.

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 BeaconsSuggested Alg. For Beacons

Random

Max

Grid

Heap (Selective Turning off BEacons)

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5. Routing5. Routing

Implosion Ad-hoc protocols

– Proactive – static: maintains a routing table.– Reactive – dynamic: establishes when required.

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…)5. Routing (Cont…)

Directed diffusion.– 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. Applications6. Applications

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 Simulator7. Sensor Network Simulator

NS –2 ; written in c++ and oTCL.

GloMoSim (Global Mobile Information System Simulator); written in C and parsec.

SensorSim;

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ChallengesChallenges Ad hoc deployment Unattended Operation Untethered (Limited Energy resource) Dynamic Changes

Ultimate Struggle System Lifetime System robustness

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ConclusionConclusion

• Promising applications• Evolving field• Scope for lots of research

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ReferencesReferences 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 YouThank You