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CONTENTSCONTENTS

IntroductionIntroduction

ArchitectureArchitecture

Communication TechnologiesCommunication TechnologiesChallengesChallenges

Applications of Smart dustApplications of Smart dust

ConclusionConclusion

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IntroductionIntroduction

Smart dust is a tiny dust size electronic deviceSmart dust is a tiny dust size electronic device.. Individual sensors of smart dust are often referred to asIndividual sensors of smart dust are often referred to as

motes.motes.

Often calledOften called micro electro-mechanical sensors(MEMS).micro electro-mechanical sensors(MEMS).

Combines sensing, computing, wireless communicationCombines sensing, computing, wireless communication

capabilities and autonomous power supply.capabilities and autonomous power supply.

So small and light in weight that they can remainSo small and light in weight that they can remainsuspended in the environment.suspended in the environment.

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They can monitor the environment for light, sound,They can monitor the environment for light, sound,temperature, chemical composition and a wide range oftemperature, chemical composition and a wide range of

other information.other information.

Present cost of individual motes $50 each, droppingPresent cost of individual motes $50 each, dropping

below $1 per mote in the near future.below $1 per mote in the near future.

The smart dust concept was introduced by Kristofer S. J.The smart dust concept was introduced by Kristofer S. J.

Pister (University of California)Pister (University of California)in 2001.in 2001.

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Smart Dust MoteSmart Dust Mote

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ArchitectureArchitecture

A single Smart Dust mote has:A single Smart Dust mote has:

A semiconductor laser diode and MEMS beam steeringA semiconductor laser diode and MEMS beam steering

mirror for active optical transmission.mirror for active optical transmission.

A MEMS corner cube retro-reflector (CCR) for passiveA MEMS corner cube retro-reflector (CCR) for passive

optical transmission.optical transmission.

An optical receiver.An optical receiver.

A signal processing and control circuitry.A signal processing and control circuitry. A power source based on thick-film batteries and solarA power source based on thick-film batteries and solar

cells.cells.

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Corner Cube Retro-reflector(CCR)Corner Cube Retro-reflector(CCR)

Comprises of three mutually perpendicular mirrors ofComprises of three mutually perpendicular mirrors of

gold-coated poly-silicon.gold-coated poly-silicon.

Has the property that any incident ray of light is reflectedHas the property that any incident ray of light is reflected

back to the source provided that it is incident within aback to the source provided that it is incident within acertain range of angles centered about the cubes bodycertain range of angles centered about the cubes body

diagonal.diagonal.

The micro-fabricated CCR includes an electrostaticThe micro-fabricated CCR includes an electrostatic

actuator that can deflect one of the mirrors at kilohertzactuator that can deflect one of the mirrors at kilohertz

ratesrates..

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Thus the external light source can be transmitted back inThus the external light source can be transmitted back in

the form of modulated signal at kilobits per second.the form of modulated signal at kilobits per second. CCR-based passive optical links require an uninterruptedCCR-based passive optical links require an uninterrupted

line-of-sight path.line-of-sight path.

CCR can transmit to the BTS only when the CCR bodyCCR can transmit to the BTS only when the CCR body

diagonal happens to point directly toward the BTS,diagonal happens to point directly toward the BTS,

within a few tens of degrees.within a few tens of degrees.

A passive transmitter can be made more omni-directionalA passive transmitter can be made more omni-directional

by employing several CCRs oriented in differentby employing several CCRs oriented in differentdirections, at the expense of increased dust mote size.directions, at the expense of increased dust mote size.

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Communication TechnologiesCommunication Technologies

Radio Frequency TransmissionRadio Frequency Transmission

Optical transmission techniqueOptical transmission technique

a) Passive Laser based Communicationa) Passive Laser based Communication

b) Active Laser based Communicationb) Active Laser based Communication

c) Fiber Optic Communicationc) Fiber Optic Communication

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Radio Frequency TransmissionRadio Frequency Transmission

Based on the generation, propagation and detection ofBased on the generation, propagation and detection of

electromagnetic waves with a frequency range from tenselectromagnetic waves with a frequency range from tens

of kHz to hundreds of GHzof kHz to hundreds of GHz..

Multiplexing techniques: time, frequency or code-Multiplexing techniques: time, frequency or code-division multiplexing.division multiplexing.

Their use leads to modulation, band pass filtering,Their use leads to modulation, band pass filtering,

demodulation circuitry, and additional circuitry, all ofdemodulation circuitry, and additional circuitry, all of

which needs to be considered, based on powerwhich needs to be considered, based on power

consumption.consumption.

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Problems with RF TransmissionProblems with RF Transmission

Large size of antenna.Large size of antenna.

RF communication can only be achieved by using time,RF communication can only be achieved by using time,

frequency or code divisionfrequency or code division..

TDMA, FDMA, and CDMA have their ownTDMA, FDMA, and CDMA have their owncomplications.complications.

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Optical transmission techniqueOptical transmission technique

Passive Laser based communicationPassive Laser based communication Downlink communication (BST to dust)- the base stationDownlink communication (BST to dust)- the base station

points a modulated laser beam at a node.Dust uses apoints a modulated laser beam at a node.Dust uses a

simple optical receiver to decode the incoming message.simple optical receiver to decode the incoming message. Uplink communication (dust to BST)- the base stationUplink communication (dust to BST)- the base station

points an un-modulated laser beam at a node, which inpoints an un-modulated laser beam at a node, which inturn modulates and reflects back the beam to the BST.turn modulates and reflects back the beam to the BST.

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AdvantagesAdvantages Optical transceivers require only simple base bandOptical transceivers require only simple base band

analog and digital circuitry; no modulators, active bandanalog and digital circuitry; no modulators, active bandpass filters or demodulators are needed.pass filters or demodulators are needed.

The short wavelength of visible or near-infrared light (ofThe short wavelength of visible or near-infrared light (of

the order of 1 micron) makes it possible for a millimeter-the order of 1 micron) makes it possible for a millimeter-

scale device to emit a narrow beam.scale device to emit a narrow beam.

The CCR makes make it possible for dust motes to useThe CCR makes make it possible for dust motes to use

passive optical transmission techniques.passive optical transmission techniques.

A base-station transceiver (BTS) equipped with aA base-station transceiver (BTS) equipped with acompact imaging receiver can decode the simultaneouscompact imaging receiver can decode the simultaneous

transmissions.transmissions.

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LimitationsLimitations

Is a single-hop network topology.Is a single-hop network topology.

Communication may suffer from variable delays if theCommunication may suffer from variable delays if the

laser beam is not already pointing at a node that islaser beam is not already pointing at a node that is

subject to communication with the BST.subject to communication with the BST.

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Active Laser Based communicationActive Laser Based communication

Has a semiconductor laser, a collimating lens and aHas a semiconductor laser, a collimating lens and a

beam-steering micro-mirrorbeam-steering micro-mirror..

Uses an active-steered laser-diode based transmitter toUses an active-steered laser-diode based transmitter to

send a collimated laser beam to a base stationsend a collimated laser beam to a base station .. Suitable for peer-to-peer communication, provided thereSuitable for peer-to-peer communication, provided there

exist a line of sight path between the motes.exist a line of sight path between the motes.

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DisadvantagesDisadvantages

Relatively high power consumptionRelatively high power consumption ..

Thus can be used only for aThus can be used only for a short duration burst-modeshort duration burst-mode

communication.communication.

Components like active beam-steering mechanism makesComponents like active beam-steering mechanism makesthe design of the dust mote more complicated.the design of the dust mote more complicated.

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Fiber Optic communicationFiber Optic communication

Employs semiconductor laser, fiber cable and diodeEmploys semiconductor laser, fiber cable and diode

receiver to generate, transfer and detect the opticalreceiver to generate, transfer and detect the optical

signal.signal.

Similar to passive optical comm..Similar to passive optical comm.. Relatively small size of the optical transceiver isRelatively small size of the optical transceiver is

employed with low-power operation.employed with low-power operation.

CCR employed on each Dust mote toCCR employed on each Dust mote to modulate uplinkmodulate uplinkdata to base station.data to base station.

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AdvantagesAdvantages

Does not require unbroken line-of-sight and the linkDoes not require unbroken line-of-sight and the link

directionalitydirectionality..

Each dust mote does not need to employ more than oneEach dust mote does not need to employ more than one

CCRCCR.. Comm.. between dust motes and a base station can beComm.. between dust motes and a base station can be

guaranteedguaranteed..

It has a longer range of communication link than that ofIt has a longer range of communication link than that ofa free space passive optical communication.a free space passive optical communication.

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LimitationsLimitations

Optical fiber cables restrict the mobility of dust moteOptical fiber cables restrict the mobility of dust mote..

Since a base station should employ several opticalSince a base station should employ several optical

components for fiber connection to each dust mote, itcomponents for fiber connection to each dust mote, it

may complicate base station design.may complicate base station design.

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ChallengesChallenges

The hardware design has to face many challenges due toThe hardware design has to face many challenges due to

the small size of the Smart Dust.the small size of the Smart Dust.

The energy requirements are also high.The energy requirements are also high.

Communication between dust motes requiresCommunication between dust motes requirescomplicated technology.complicated technology.

Cost now about $50 - $100 per sensorCost now about $50 - $100 per sensor

Memory is only of hundreds KB.Memory is only of hundreds KB.

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ApplicationsApplications

To monitor temperature or humidity.To monitor temperature or humidity.

A forest service could use smart dust to monitor for firesA forest service could use smart dust to monitor for fires

in a forest.in a forest.

To track enemy movements, detect poisonous gas.To track enemy movements, detect poisonous gas.(Military applications).(Military applications).

To detect traffic flow.To detect traffic flow.

Can monitor the condition of machinery.Can monitor the condition of machinery. Health Monitoring.Health Monitoring.

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ConclusionConclusion

There are many ongoing researches on Smart Dust, theThere are many ongoing researches on Smart Dust, themain purpose of these researches is to make Smart Dustmain purpose of these researches is to make Smart Dust

mote as small as possible and to make it available at asmote as small as possible and to make it available at as

low price as possible. Soon we will see Smart Dust beinglow price as possible. Soon we will see Smart Dust beingused in varied application.used in varied application.

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Thank You!Thank You!