Smart Dust Understandable

8/13/2019 Smart Dust Understandable

1/32

Smart Dust Seminar Report ‘08

WHAT IS A SMART DUST?

Autonomous sensing and communication in a cubic millimeter

Berkeley’s Smart Dust project, led by Professors Pister and Kahn,

discussed carefully on the limits on size and power consumption in

autonomous sensor nodes. Size reduction is more important , to make the

nodes as inepensi!e and easy"to"or#anise as possible. $he research team

is confident that they can include the needed sensin#, communication, and

computin# hardware, alon# with a power supply, in a !olume no more than

a few cubic millimeters, while still achie!in# impressi!e performance in

terms of sensor functionality and communications capability. $hese

millimeter"scale nodes are called %Smart &ust.' (t is certainly within the

impossible of possibility that future prototypes of Smart &ust could be

small enou#h to remain suspended in air, to keep floatin# by air currents,

sensin# and communicatin# for hours or days on end.

)Smart dust) * sensor"laden networked computer nodes that are

just cubic millimetres in !olume. $he smart dust project en!isions a

complete sensor network node, includin# power supply, processor, sensor

and communications mechanisms, in a sin#le cubic millimetre. .Smart dust

motes could run for years , #i!en that a cubic millimetre battery can store

+ and could be backed up with a solar cell or !ibrational ener#y source

$he #oal of the Smart &ust project is to build a millimeter"scale

sensin# and communication platform for a massi!ely distributed sensornetwork. $his de!ice will be around the size of a #rain of sand and will

contain sensors, computational ability, bi"directional wireless

communications, and a power supply. Smart dust consists of series of

circuit and micro"electro"mechanical systems -/S0 desi#ns to cast

those functions into custom silicon. icroelectromechanical systems

-/S0 consist of etremely tiny mechanical elements, often inte#rated

to#ether with electronic circuitry.

Dept. of ECE Entecollege.com+


2/32


THE MEMS TECHNOO!" IN SMART DUST

Smart dust re1uires mainly re!olutionary ad!ances inminiaturization, inte#ration 2 ener#y mana#ement. 3ence desi#ners ha!e

used /S technolo#y to build small sensors, optical communication

components, and power supplies. icroelectro mechanical systems

consists of etremely tiny mechanical elements, often inte#rated to#ether

with electronic circuitory. $hey are measured in micrometers, that is

millions of a meter. $hey are made in a similar fashion as computer chips.

$he ad!anta#e of this manufacturin# process is not simply that small

structures can be achie!ed but also that thousands or e!en millions of

system elements can be fabricated simultaneously. $his allows systems to

be both hi#hly comple and etremely low"cost.

icro"/lectro"echanical Systems -/S0 is the inte#ration of

mechanical elements, sensors, actuators, and electronics on a common

silicon substrate throu#h microfabrication technolo#y. 4hile the

electronics are fabricated usin# inte#rated circuit -(50 process se1uences

-e.#., 56S, Bipolar processes0, the micromechanical components are

fabricated usin# compatible 7micromachinin#7 processes that selecti!ely

etch away parts of the silicon wafer or add new structural layers to form the

mechanical and electromechanical de!ices. /S realizes a complete

System 6n chip technolo#y.

icroelectronic inte#rated circuits can be thou#ht of as the

7brains7 of a system and allow microsystems to sense and control the

en!ironment. Sensors #ather information from the en!ironment throu#h

measurin# mechanical, thermal, biolo#ical, chemical, optical, and ma#netic

phenomena. $he electronics then process the information deri!ed from the

sensors and throu#h some decision makin# capability direct the actuators to

respond by mo!in#, positionin#, re#ulatin#, and filterin#, thereby

Dept. of ECE Entecollege.com8


3/32


controllin# the en!ironment for some desired purpose. Because /S

de!ices are manufactured usin# batch fabrication techni1ues similar to

those used for inte#rated circuits, unprecedented le!els of functionality,

reliability, and sophistication can be placed on a small silicon chip at a

relati!ely low cost. $he deep insi#ht of /S is as a new manufacturin#

technolo#y, a way of makin# comple electromechanical systems usin#

batch fabrication techni1ues similar to those used for inte#rated circuits,

and unitin# these electromechanical elements to#ether with

electronics.3istorically, sensors and actuators are the most costly and

unreliable part of a sensor"actuator"electronics system. /S technolo#y

allows these comple electromechanical systems to be manufactured usin#

batch fabrication techni1ues, increasin# the reliability of the sensors and

actuators to e1ual that of inte#rated circuits. $he performance of /S

de!ices and systems is epected to be superior to macroscale components

and systems, the price is predicted to be much lower.



4/32


Dept. of ECE Entecollege.com:


5/32


SMART DUST TECHNOO!"

Integrated into a single #ac$age are %&

+. /S sensors

8. /S beam steerin# mirror for acti!e optical transmission

9. /S corner cube retroreflector for passi!e optical transmission

:. ;n optical recei!er

"passi!e

transmission usin# corner cube retroreflector to transmit to base stations

and acti!e transmission usin# a laser diode 2 steerable mirrors for mote to

mote communication.

• $he photo diode allows optical data reception

• Si#nal processin# 2 control circuitory consists of analo# (?6 ,&SPs to

control 2process the incomin# data

• $he power system consists of a thick film battery,a solar cell with a char#e

inte#ratin# capacitor for a period of darkness.

O'ERATION O( THE MOTE

Dept. of ECE Entecollege.com


6/32


$he Smart &ust mote is run by a microcontroller that not only

determines the tasks performed by the mote, but controls power to the

!arious components of the system to conser!e ener#y. Periodically the

microcontroller #ets a readin# from one of the sensors, which measure one

of a number of physical or chemical stimuli such as temperature, ambient

li#ht, !ibration, acceleration, or air pressure, processes the data, and stores

it in memory. (t also occasionally turns on the optical recei!er to see if

anyone is tryin# to communicate with it. $his communication may include

new pro#rams or messa#es from other motes. (n response to a messa#e or

upon its own initiati!e the microcontroller will use the corner cube

retroreflector or laser to transmit sensor data or a messa#e to a base station

or another mote.

$he primary constraint in the desi#n of the Smart &ust motes is !olume,

which in turn puts a se!ere constraint on ener#y since we do not ha!e much

room for batteries or lar#e solar cells. $hus, the motes must operate

efficiently and conser!e ener#y whene!er possible. ost of the time, the

majority of the mote is powered off with only a clock and a few timers

runnin#. 4hen a timer epires, it powers up a part of the mote to carry out

a job, then powers off. ; few of the timers control the sensors that measure

one of a number of physical or chemical stimuli such as temperature,

ambient li#ht, !ibration, acceleration, or air pressure. 4hen one of these

timers epires, it powers up the correspondin# sensor, takes a sample, and

con!erts it to a di#ital word. (f the data is interestin#, it may either be

stored directly in the S@; or the microcontroller is powered up to

perform more comple operations with it. 4hen this task is complete,

e!erythin# is a#ain powered down and the timer be#ins countin# a#ain.

;nother timer controls the recei!er. 4hen that timer epires, the

Dept. of ECE Entecollege.com=


7/32


8/32


COMMUNICATIN! WITH A SMART DUST

COMMUNICATIN! (ROM A !RAIN O( SAND

Smart &ust’s full potential can only be attained when the sensor

nodes communicate with one another or with a central base station.

4ireless communication facilitates simultaneous data collection from

thousands of sensors. $here are se!eral options for communicatin# to and

from a cubic"millimeter computer.

@adio"fre1uency and optical communications each ha!e their

stren#ths and weaknesses. @adio"fre1uency communication is well under"

stood, but currently re1uires minimum power le!els in the multiple

milliwatt ran#e due to analo# miers, filters, and oscillators. (f whisker"

thin antennas of centimeter len#th can be accepted as a part of a dust mote,

then reasonably efficient antennas can be made for radio"fre1uency

communication. 4hile the smallest complete radios are still on the order of

a few hundred cubic millimeters, there is acti!e work in the industry to

produce cubic"millmeter radios.

oreo!er @ techni1ues cannot be used because of the followin#

disad!anta#es >"

8. urthermore radio transcei!ers are relati!ely comple circuits makin#

it difficult to reduce their power consumption to re1uired microwatt

le!els.

9. $hey re1uire modulation, band pass filterin# and demodulation

circuitory.

So an attracti!e alternati!e is to employ free space optical

transmission. Studies ha!e shown that when a line of si#ht path is a!ailable

, well defined free space optical links re1uire si#nificantly lower ener#y per

Dept. of ECE Entecollege.comC


9/32


bit than their @ counterpaths.

$here are se!eral reasons for power ad!anta#e of optical links.

+. 6ptical transcei!ers re1uire only simple baseband

9. $he short wa!elen#th of !isible or near infra red li#ht -of the order of

+ micron0 makes it possible for a millimeter scale de!ice to emit a

narrow beam -ie, hi#h antenna #ain can be achie!ed0.

Semiconductor lasers and diode recei!ers are intrinsically small,

and the correspondin# transmission and detection circuitry for on?off keyed

optical communication is more amenable to low"power operation than

most radio schema. Perhaps most important, optical power can be

collimated in ti#ht beams e!en from small apertures. &iffraction enforces a

fundamental

limit on the di!er#ence of a beam, whether it comes from an antenna or a

lens. Daser pointers are cheap eamples of milliradian collimation from a

millimeter aperture. $o #et similar collimation for a +"E3z radio"

fre1uency si#nal would re1uire an antenna +FF meters across, due to the

difference in wa!elen#th of the two transmissions. ;s a result, optical

transmitters of millimeter size can #et antenna #ains of one million or

more, while similarly sized radio"fre1uency antennas are doomed by

physics to be mostly isotropic.

5ollimated optical communication has two major drawbacks.

Dine of si#ht is re1uired for all but the shortest distances, and narrow

beams imply the need for accurate pointin#. 6f these, the pointin#

accuracy can be sol!ed by /S technolo#y and cle!er al#orithms, but an

optical transmitter under a leaf or in a shirt pocket is of little use to anyone.

Dept. of ECE Entecollege.comG


10/32


4e ha!e chosen to eplore optical communication in some depth due to

the potential for etreme low"power communication.

O'TICA COMMUNICATIONS

We )a*e e+#lored t,o a##roac)es to o#tical communications% passi!e

reflecti!e systems and acti!e"steered laser systems. (n a passi!e

communication system, the dust mote does not re1uire an onboard li#ht

source. (nstead, a special confi#uration of mirrors can either reflect or not

reflect li#ht to a remote source.

'assi*e re-lecti*e s.stems

Dept. of ECE Entecollege.com+F


11/32


$he passi!e reflecti!e communication is obtained by a special

de!ice called 55@ -5orner cube retro reflector0 consists of three mutually

ortho#onal mirrors. Di#ht enters the 55@, bounces off each of the three

mirrors, and is reflected back parallel to the direction it entered. (n the

/S !ersion, the de!ice has one mirror mounted on a sprin# at an an#le

sli#htly askew from perpendicularity to the other mirrors.

(n this position, because the li#ht enterin# the 55@ does not return

alon# the same entry path, little li#ht returns to the source*a di#ital F.

;pplyin# !olta#e between this mirror and an electrode beneath it causes

the mirror to shift to a position perpendicular to other mirrors, thus causin#

the li#ht enterin# the 55@ to return to its source*a di#ital +. $he mirror’s

low mass allows the 55@ to switch between these two states up to a

thousand times per second, usin# less than a nanojoule per F→+ transition.

; +HF transition, on the other hand, is practically free because dumpin#

the char#e stored on the electrode to the #round re1uires almost no ener#y.

6ur latest Smart &ust de!ice is a =9"mm9 autonomous bidirectional

communication mote that recei!es an optical si#nal, #enerates a

pseudorandom se1uence based on this si#nal to emulate sensor data, and

then optically transmits the result. $he system contains a micromachined

corner"cube reflector, a F.FAC"mm9 56S chip that draws +A microwatts,

and a hearin# aid battery. (n addition to a battery based operation, we ha!ealso powered the de!ice usin# a 8"mm8 solar cell. $his mote demonstrates

Smart &ust’s essential concepts, such as optical data transmission, data

processin#, ener#y mana#ement, miniaturization, and system inte#ration.

; passi!e communication system suffers se!eral limitations.

Inable to communicate with each other, motes rely on a central station

e1uipped with a li#ht source to send and recei!e data from other motes. (f a

Dept. of ECE Entecollege.com++


12/32


#i!en mote does ha!e a clear line of si#ht to the central station, that mote

will be isolated from the network. ;lso, because the 55@ reflects only a

small fraction of the li#ht emitted from the base station, this system’s ran#e

cannot easily etend beyond + kilometer. $o circum!ent these limitations,

dust motes must be acti!e and ha!e their own onboard li#ht source.

Acti*e&steered laser s.stems

or mote"to"mote communication, an acti!e"steered laser

communication system uses an onboard li#ht source to send a ti#htly

collimated li#ht beam toward an intended recei!er. Steered laser

communication has the ad!anta#e of hi#h power densityJ for eample, a +"

milliwatt laser radiatin# into + milliradian -9.: arcseconds0 has a density of

approimately 9+C kilowatts per steradian -there are : π steradians in a

sphere0, as opposed to a +FF"watt li#htbulb that radiates C watts per

steradian isotropically. ; Smart &ust mote’s emitted beam would ha!e a

di!er#ence of approimately + milliradian, permittin# communication o!er

enormous distances usin# milliwatts of power. /ach mote must carefully

wei#h the needs to sense, compute, communicate, and e!aluate its ener#y

reser!e status before allocatin# precious nanojoules of ener#y to turn on its

transmitter or recei!er. Because these motes spend most of their time

sleepin#, with their recei!ers turned off, schedulin# a common awake time

across the network is difficult. (f motes don’t wake up in a synchronized

manner, a hi#hly dynamic network topolo#y and lar#e packet latency

result. Isin# burstmode communication, in which the laser operates at up

to se!eral tens of me#abits per second for a few milliseconds, pro!ides the

most ener#y"efficient way to schedule this network. $his procedure

minimizes the mote’s duty cycle and better utilizes its ener#y reser!es. $he

steered a#ile laser transmitter consists of a semiconductor diode laser

Dept. of ECE Entecollege.com+8


13/32


coupled with a collimatin# lens and /S beam"steerin# optics based on

a two de#ree"of"freedom silicon micromirror. $his system inte#rates all

optical components into an acti!e C"mm9 !olume as the fi#ure shows

CORNER CU/E RETRORE(ECTOR

$hese /S structure makes it possible for dust motes to use

passi!e optical transmission techni1ues ie, to transmit modulated optical

si#nals without supplyin# any optical power. (t comprises of three

mutually perpendicular mirrors of #old"coated polysilicon. $he 55@ has

the property that any incident ray of li#ht is reflected back to the source

-pro!ided that it is incident within a certain ran#e of an#les centered about

the cube’s body dia#onal0.(f one of the mirrors is misali#ned , this

retroreflection property is spoiled. $he microfabricated 55@ contains an

electrostatic actuator that can deflect one of the mirrors at kilohertz rate. (t

has been demonstrated that a 55@ illuminated by an eternal li#ht source

can transmit back a modulated si#nal at kilobits per second. Since the dust

mote itself does not emit li#ht , passi!e transmitter consumes little power.

Isin# a microfabricated 55@, data transmission at a bit rate upto + kilobit

per second and upto a ran#e of +


14/32


(t should be emphasized that 55@ based passi!e optical links

re1uire an uninterrupted line of si#ht. $he 55@ based transmitter is hi#hly

directional. ; 55@ can transmit to the B$S only when the 55@ body

dia#onal happens to point directly towards the B$S, within a few tens of

de#rees. ; passi!e transmitter can be made more omnidirectional by

employin# se!eral 55@s ,oriented in different directions , at the epense of

increased dust mote size.

$he fi#ure illustrates free space optical network utilizin# the 55@

based passi!e uplink. $he B$S contains a laser whose beam illuminates an

area containin# dust motes. $his beam can be modulated with downlink

data includin# commands to wake up and 1uery the dust motes. 4hen the

illuminatin# beam is not modulated , the dust motes can use their 55@s to

transmit uplink data back to the base station. ; hi#h frame rate 55& !ideo

camera at the B$S sees the 55@ si#nals as li#hts blinkin# on and off. (t

decodes these blinkin# ima#es to yield the uplink data. ;nalysis show that

this uplink scheme achie!es se!eral kilobits per second o!er hundreds of

metres in full sunli#ht. ;t ni#ht ,in clear ,still air ,the ran#e should etend

to se!eral kilometres. Because the camera uses an ima#in# process to

separate the simultaneous transmissions from dust motes at different

locations, we say it uses ‘space di!ision multiplein#’. $he ability for a

Dept. of ECE Entecollege.com+:


15/32


!ideo camera to resol!e these transmissions is the conse1uence of the short

wa!elen#th of !isible or near infra red li#ht. $his does not re1uire any

coordination amon# the dust motes.

ACTI0E O'TICA TRANSMITTERS

4hen the application re1uires dust motes to use acti!e optical

transmitters , /S technolo#y can be used to assemble a semiconductor

laser, a collimatin# lens, and a beam steerin# micro mirror. ;cti!e

transmitters make possible peer to peer communication between dust

motes, pro!ided there eists a line of path of si#ht between them. Power

consumption imposes a trade off between bandwidth and ran#e. $he dust

motes can communicate o!er lon# distances at low data rates or hi#her bit

rates o!er shorter distances. $he relati!ely hi#her power consumption of

semiconductor lasers dictates that these acti!e transmitters be used for

short duration burst mode communication only. Sensor network usin#

acti!e dust mote transmitters will re1uire some protocol for dust motes to

aim their beams towards the recei!in# parties.

ISTENIN! TO A DUST (IED

any Smart &ust applications rely on direct optical

communication from an entire field of dust motes to one or more base

stations. $hese base stations must therefore be able to recei!e a !olume of

simultaneous optical transmissions. urther, communication must be

possible outdoors in bri#ht sunli#ht which has an intensity of

approimately + kilowatt per s1uare meter, althou#h the dust motes each

Dept. of ECE Entecollege.com+


16/32


transmit information with a few milliwatts of power. Isin# a narrow"band

optical filter to eliminate all sunli#ht ecept the portion near the li#ht

fre1uency used for communication can partially sol!e this second problem,

but the ambient optical power often remains much stron#er than the

recei!ed si#nal power.

Ad*antages o- imaging recei*ers

;s with the transmitter, the short wa!elen#th of optical

transmissions compared with radio fre1uency o!ercomes both challen#es.

Di#ht from a lar#e field of !iew field can be focused into an ima#e, as in

our eyes or in a camera. (ma#in# recei!ers utilize this to analyze different

portions of the ima#e separately to process simultaneous transmissions

from different an#les. $his method of distin#uishin# transmissions based

on their ori#inatin# location is referred to as space di!ision multiple access

-S&;0. (n contrast, most radio"fre1uency antennas recei!e all incident

radio power in a sin#le si#nal, which re1uires usin# additional tactics, such

as fre1uency tunin# or code di!ision multiple access -5&;0, to separate

simultaneous transmissions.

(ma#in# recei!ers also offer the ad!anta#e of dramaticallydecreasin# the ratio of ambient optical power to recei!ed si#nal

power.(deally, the ima#in# recei!er will focus all of the recei!ed power

from a sin#le transmission onto a sin#le photodetector. (f the recei!er has

an n Hn array of piels, then the ambient li#ht that each piel recei!es is

reduced by a factor n8 compared with a nonima#in# recei!er.

Dept. of ECE Entecollege.com+=


17/32


0ideo camera1

; !ideo camera is a strai#htforward implementation of an

ima#in# recei!er. (f each member in a colony of Smart &ust motes flashes

its own si#nal at a rate of a few bits per second, then each transmitter will

appear in the !ideo stream at a different location in the ima#e. Isin# a

hi#h"speed camera and a dedicated di#ital si#nal processor to process the

!ideo si#nal achie!es hi#her data rates. 4ith modern cameras and &SPs,

processin# !ideo at about +,FFF frames per second should be feasible. $his

would allow communication at a few hundred bits per second, which is

Dept. of ECE Entecollege.com+A


18/32


acceptable for many applications. ;n alternati!e recei!er architecture

pro!ides a more ele#ant solution at much hi#her data rates, a!oidin# the

need for computationally intensi!e !ideo processin# and !ery hi#h speed

cameras. (nte#ratin# an ima#in# recei!er onto a sin#le microchip imposes

se!ere constraints in silicon area and power consumption per piel. 6nly

recently ha!e continuin# reductions in transistor size allowed for sufficient

reductions in circuit area and power consumption to achie!e this le!el of

inte#ration.

Dept. of ECE Entecollege.com+C


19/32


CORE (UNCTIONAIT" S'ECI(ICATION

5hoose the case of military base monitorin# wherein on the order

of a thousand Smart &ust motes are deployed outside a base by a micro air

!ehicle to monitor !ehicle mo!ement. $he motes can be used to determine

when !ehicles were mo!in#, what type of !ehicle it was, and possibly how

fast it was tra!ellin#. $he motes may contain sensors for !ibration, sound,

li#ht, (@, temperature, and ma#netization. 55@s will be used for

transmission, so communication will only be between a base station and

the motes, not between motes. ; typical operation for this scenario would

be to ac1uire data, store it for a day or two, then upload the data after bein#

interro#ated with a laser. 3owe!er, to really see what functionality the

architecture needed to pro!ide and how much reconfi#urability would be

necessary, an ehausti!e list of the potential acti!ities in this scenario was

made. $he operations that the mote must perform can be broken down into

two cate#ories> those that pro!oke an immediate action and those that

reconfi#ure the mote to affect future beha!ior.

'ro#osed Arc)itecture

Dookin# throu#h the functional specifications for the core, we

realized that each operation is re#ulated by a timed e!entJ hence a bank of

timers forms the basis of the architecture. or minimum ener#y, a direct

mappin# of a particular function into hardware is #enerally best, but from

the list of specifications it was clear that a certain amount of

reconfi#urability would be necessary. $hus, the timers enable setup

memories that confi#ure functional blocks into data paths that pro!ide only

the capabilities necessary for that e!ent. $hese paths are data"dri!en so that

Dept. of ECE Entecollege.com+G


20/32


functional blocks are only powered up when their inputs are ready,

minimizin# standby power and #litchin#. ; block dia#ram of this new

architecture is shown in the fi#ure

$he net fi#ure details a section of the timer bank and setup

memory. $he timer is loaded from the timer !alue memory, settin# its

period. 4hen the timer epires, it enables setupmemory 1, which

confi#ures the data path to perform the desired function. 4hen the data

path has finished its operation, setup memory 1 will release its

confi#uration and . either the timer !alue can be loaded into the timer and

thecountdown restarted or setup memory 2 can be enabled.

Setup memory 2 will then confi#ure the data path for another

operation, thus facilitatin# multiple operations per timer e!ent. ;dditional

setup memory can be added for more in!ol!ed se1uences. emory holds

certain timer"independent confi#uration bits, such as timer enables. $he

sensor re#isters are used to store pre!ious sensor readin#s to use in

computin# data chan#es. Larious computation blocks can be included in

the data path, such as an adder, comparator, and $ unit.

Dept. of ECE Entecollege.com8F


21/32


ultiple timer periods are desirable for se!eral situations. or

eample, one mi#ht want to sample a sensor at a slow rate until an

interestin# si#nal is detected. ;t that point, the samplin# rate should

increase. (n addition, the motes mi#ht be deployed without anyone comin#

back to talk to them for a day, so it would be desirable to be able to set the

recei!er wake"up timer to not wake"up for 8: hours, but then it should

decrease the period dramatically to +F’s of seconds in case one doesn’t

make it back to talk to the mote at eactly the ri#ht time. $he proposed

architecture facilitates this by pro!idin# multiple timer !alues that can be

loaded into the timer dependin# on the results of the data path computation.

;nother feature of this architecture is ener#y"dri!en operation

modes. ;n ener#y"monitorin# unit selects between multiple banks of setupmemory and timer !alues dependin# on the current le!el of the ener#y

stores. /ach bank can ha!e different timer periods and al#orithms to

control ener#y ependiture. $wo types of packets can be sent to the mote,

correspondin# to the two types of operations. (mmediate mode operations

use the packet body to confi#ure the data path ri#ht away. @econfi#uration

Dept. of ECE Entecollege.com8+


22/32


operations load the packet body into the setup memory for future

confi#uration.

$he followin# fi#ure shows the functional blocks included in the

reconfi#urable data path.

or the communications back end, there is a data reco!ery block,

timin# reco!ery block, (@ filter, packet encoder that does bits stuffin# and

adds the fla# byte, packet decoder that does bit unstuffin#, 5@5 block, and

a (6. (ncomin# packets are stored in the (6 until the 5@5 can be

!erified, at which point the packet body will be used as described abo!e.

$he #lobal memory holds certain timer"independent confi#uration bits,

such as timer enables. $he sensor re#isters are used to store pre!ious

sensor readin#s to use in computin# data chan#es. Larious computation

blocks can be included in the data path, such as an adder, comparator, and

$ unit.



23/32


24/32


'ER(ORMIN! A TAS2

i#ure < delineates the operation of the architecture by showin#

the confi#uration for one of the most common tasks, ac1uirin# sensor data,

checkin# if it has chan#ed more than a threshold !alue, then storin# the

result to memory. 6ne potential hazard of this architecture is that the done

si#nals can #litch as the blocks are powered up, which would pro!ide a

false tri##er to the net sta#e. ; second issue is that despite the fact that the

blocks are powered down, the internal nodes do not dischar#e immediately.

;n ad!anta#e of this is that less char#e will be needed when the block is

powered up a#ain. 3owe!er, this stored char#e will also allow the block to

continue to dri!e its outputs despite bein# powered down, so the outputs

will #enerally need tri"state buffers. $hese hazards will re1uire some etra

work at the circuit le!el to make this architecture work.

3spice simulations were used simulations were used to determine

the power and ener#y consumptions of some of the blocks to study the

feasibility of the proposed architecture. $he preliminary results of 3spice

simulations show that it is possible to achie!e atleast two orders of

ma#nitude lower ener#y consumption, with this proposed architecture.

Dept. of ECE Entecollege.com8:


25/32


MA3OR CHAEN!ES

+. $o incorporate all these functions while maintainin# a low power

consumption

8. aimisin# operatin# life #i!en the limited !olume of ener#y stora#e

9. $he functionality can be achie!ed only if the total power consumption

is limited to microwatt le!els.

:. ;n unbroken line of si#ht of path should be a!ailable for free space

optical links.



26/32


A''ICATIONS

+. 5i!il and military applications where chemical 2 biolo#ical a#ents in

a battle field are detected.

8. Lirtual keyboard Elue a dust mote on each of your fin#ernails.

;ccelerometers will sense the orientation and motion of each of your

fin#ertips, and talk to the computer in your watch. 5ombined with a

/S au#mented"reality heads"up display, your entire computer (?6

would be in!isible to the people around you.

9. (n!entory 5ontrol Smart office spaces $he 5enter for the Built

/n!ironment has fabulous plans for the office of the future in which

en!ironmental conditions are tailored to the desires of e!ery

indi!idual. aybe soon we)ll all be wearin# temperature, humidity,

and en!ironmental comfort sensors sewn into our clothes,

continuously talkin# to our workspaces which will deli!er conditionstailored to our needs.

:. (ndi!idual dust motes can be attached to the objects one wishes to

monitor or a lar#e no> of dust motes may be dispersed in the

en!ironment randomly.

" (nstrumentation of semiconductor

processin# chambers,wind tennels, rotatin# machinery etc.

=. ay be used in biolo#ical research e#>" to monitor mo!ements 2

internal processes of insects.

Dept. of ECE Entecollege.com8=


27/32


HOW (AR THE" HA0E /EEN IM'EMENTED

+. $he optical recei!er for the smart dust project is bein# de!eloped. $he

recei!er senses incomin# laser transmissions at up to +bit?s, for a

power consumption of +8M4. ;lthou#h this is too hi#h for continuous

use in smart dust, it is a reasonable fi#ure for the download of small

amounts of data such as a +Kbit pro#ram.

8. or data transmission, the team is usin# corner cube retro"reflectors

-55@s0 built usin# /S techni1ues. 55@s are produced by placin#

three mirrors at ri#ht an#les to each other to form the corner of a bo

that has been sil!ered inside.

$he key property of a 55@ is that li#ht enterin# it is reflected back

alon# the path it entered on. or the smart dust system, the 55@ is

bein# built on a /S process with the two !ertical sides bein#

assembled by hand. 4hen a li#ht is shone into the 55@, it reflects back to the sendin# position. By modulatin# the position of one of the

mirrors, the reflected beam can be modulated, producin# a low"ener#y

passi!e transmission.

9. $he analo#"di#ital con!ertor -;&50 the Cbit ;&5, has so far

demonstrated with an input ran#e of +L, e1ual to the power supply,

and a AFk3z samplin# rate. $he con!erter draws +.CM4 when

samplin# at that rate, or 8Ap for an Cbit sample.

:. $he latest smart dust mote, with a !olume of just +=cu mm, has been

tested. (t takes samples from a photo"detector, transmits their !alues

with the 55@ and runs off solar cells. So smart dust is on the way.

Dept. of ECE Entecollege.com8A


28/32


29/32


RE(ERENCES

+. P.B.5hu , KS Pister N %optical communication usin# micro corner

cube reflectors' +Fth (/// (nt’l 4orkshop on icro /lectro

echanical Systems

8. . Kahn , @.3.Katz, KS Pister N %obile Oetworkin# for Smart

&ust'

9. www.eecs.berkerly.edu

:. www.entecolle#e.com

Dept. of ECE Entecollege.com8G


30/32


AC2NOWED!EMENT

( etend my sincere thanks to 'ro- 4 3ead of the &epartment for

pro!idin# me with the #uidance and facilities for the Seminar.

( epress my sincere #ratitude to Seminar coordinator

Mr , Staff in char#e, for their cooperation and #uidance for preparin#

and presentin# this seminar.

( also etend my sincere thanks to all other faculty members of

/lectronics and 5ommunication &epartment and my friends for their

support and encoura#ement.

Entecollege1com

Dept. of ECE Entecollege.com9F


31/32


A/STRACT

;d!ances in hardware technolo#y has enabled !ery compact,

autonomous and mobile nodes each ha!in# one or more sensors,

computation and communication capabilities ,and a power supply. $he

Smart &ust project is eplorin# whether an autonomous sensin#,

computin#, and communication system can be packed into a cubic"

millimeter mote to form the basis of inte#rated, massi!ely distributed

sensor networks. (t focuses on reduction of power consumption, size and

cost. $o build these small sensors, processors, communication de!ices, and

power supply , desi#ners ha!e used the /S -icro electro mechanical

Systems0 technolo#y.

Smart &ust nodes otherwise known as %motes' are usually of the

size of a #rain of sand and each mote consists of >

+. sensors

8. transmitter 2 recei!er enablin# bidirectional wireless communication.

9. processors and control circuitory

:. power supply unit

Isin# smart dust nodes, the ener#y to ac1uire and process a

sample and then transmit some data about it could be as small as a few

nanooules.

$hese dust motes enable a lot of applications, because at these

small dimensions ,these motes can be scattered from aircraft for battle field

monitorin# or can be stirred into house paint to create the ultimate home

sensor network.

Dept. of ECE Entecollege.com9+


32/32


CONTENTS

• WHAT IS A SMART DUST?

• THE MEMS TECHNOO!" IN SMART DUST

• SMART DUST TECHNOO!"

• O'ERATION O( THE MOTE

• COMMUNICATIN! WITH A SMART DUST

• O'TICA COMMUNICATIONS

• ISTENIN! TO A DUST (IED

• CORE (UNCTIONAIT" S'ECI(ICATION 'ER(ORMIN! A

TAS2

• MA3OR CHAEN!ES

• A''ICATIONS

• HOW (AR THE" HA0E /EEN IM'EMENTED

• SUMMAR"

• RE(ERENCES

Smart Dust Understandable

Documents

Transcript of Smart Dust Understandable