report of SMART DUST

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SMART DUST 2011

Chapter 1:

INTRODUCTION

1.1 What is Smart Dust?

Smart dust is a tiny dust size device with extra-ordinary capabilities. These

devices are also called as “motes”. Smart dust combines sensing, computing, wireless

communication capabilities and autonomous power supply within volume of only few

millimeters and that too at low cost. These devices are proposed to be so small and light

in weight that they can remain suspended in the environment like an ordinary dust

particle. These properties of Smart Dust will render it useful in monitoring real world

phenomenon without disturbing the original process to an observable extends. Presently

the achievable size of Smart Dust is about 5mm cube, but we hope that it will eventually

be as small as a speck of dust. Individual sensors of smart dust are often referred to as

motes because of their small size. These devices are also known as MEMS, which stands

for micro electro-mechanical sensors.

Fig.1: Snapshot of Smart Dust (“motes”).

These are ultra miniature devices with the properties of sensors, with the own

processor and with the capability to transmit and receive data either in the UHF band or

with the help of the laser beam. These devices were called “smart dust” (SMART – Self-

Monitoring, Analysis, Reporting Technology, dust – due to extremely small volume,

some cubic millimeters.). These units may serve as the nodes of the cellular spread net

system, which may cover rather large areas and gather data of different types: ecological,

temperature, humidity, intrusion, audio and video. The special operation system was

Dept. of CS&E, BGSIT 1



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developed for these devices (TinyOS) with the possibility to work on less than 8

kilobytes memory. Chemical or solar cells provide the power consumption. In some cases

power, radiated from the external source is used, as in radio frequency identification

devices. The rapid progress in the wireless sensor networks promises new important

applications and demands to the traditional telecommunication problems.

1.2 History

In the early stages of the project, the team gained experience by building

relatively large motes using components available “of theshelf”. One such mote, named

“RF Mote,” has sensors for “temperature, humidity, barometric pressure, light intensity,

tilt and vibration, and magnetic field” and it is capable of communicating distances of

about 60 feet using radio frequency (RF) communication. If the mote operated

continuously, its battery would last up to one week.

The Defense Advanced Research Projects Agency (DARPA) has been funding

Smart Dust research heavily since the late 1990s, seeing virtually limitless applications in

the sphere of modern warfare. So far the research has been promising, with prototype

smart dust sensors as small as 5mm. But further scaling down needs advance

technological changes. Costs have been dropping rapidly with technological innovations,

bringing individual motes down to as little as $50 each, with hopes of dropping below $1

per mote in the near future.

In spite of the design challenges in the size of the mote, power supply,

communication and computation, researchers continue to make progress towards their

main goal of reducing the size of the mote to 1-millimeter cube. Hopefully in the next

couple of years the objectives of the Smart Dust project will be realized, andcommercialization and subsequent use will be widespread throughout society. In the

military for example it could offer an alternative and cheaper way to monitor enemies by

reducing cost, risk to human life and performance. In the future there will be billions of




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motes embedded in everything that will be able to sense, compute and communicate with

each other using ultra low power.

Chapter 2:

COMPONENTS

2.1 Structure

A smart dust particle is often called motes (Fig. 2). One single mote has a Micro

Electro Mechanical System (MEMS), a semiconductor laser diode, MEMS beam steering

mirror for active optical transmission, a MEMS corner cube retro-reflector for passive

optical transmission, an optical receiver, a signal processing and control circuitry, and a

power source based on thick-film batteries and solar cells.

A major challenge is to incorporate all these functions while maintaining very low

power consumption and optimizing the operating life of the mote. The structure of a

single moat is shown in Figure 3. Smart dust motes consist of a passive optical

transmitter with a micro fabricated corner- Cube Retro-reflector (CCR). This CCR

contains three mutually perpendicular mirror fabricated of gold- coated poly-silicon (fig.

4). The CCR reflects any ray of light within a certain range of angles centered about the

cube diagonal back to the source.


Fig.2: Showing size of Smart Dust



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The power system consists of a thick-film battery or a solar cell, or both with a

charge-integrating capacitor (power capacitor). The thick film battery of sol or gel V2O3

provides as a backup in darkness, while solar cells generate energy from sunlight.

Depending on its objective, the design integrates various sensors, including light,

temperature, vibration, magnetic field, acoustic, and wind shear, onto the mote. Active

transmitters make possible peer-to-peer communication between dust motes, provided

there exists a line-of-sight path between them.

2.2 Corner Cube Retro-Reflector (CCR)

CCR comprises three mutually perpendicular mirrors of gold-coated poly-silicon.

The CCR has the property that any incident ray of light is reflected back to the source

(provided that it is incident within a certain range of angles centered about the cube’s

body diagonal). If one of the mirrors is misaligned, this retro-reflection property is

spoiled. The micro-fabricated CCR includes an electrostatic actuator that can deflect one

of the mirrors at kilohertz rates. It has been demonstrated that a CCR illuminated by an

external light source can transmit back a modulated signal at kilobits per second. Since

the dust mote itself does not emit light, the passive transmitter consumes little power.


Fig.3: Structural Components of a Smart Dust Mote



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Using a micro-fabricated CCR, we can achieve data transmission at a bit rate up to 1

kilobit per second, and over a range up to 150 meters, using a 5milliwatt illuminating

laser.

Fig.4: Snapshot of CCR One should note that CCR-based passive optical links require an uninterrupted

line-of-sight path. Moreover, a CCR-based passive transmitter is inherently directional; a

CCR can transmit to the BTS only when the CCR body diagonal happens to point

directly toward the BTS, within a few tens of degrees.

A passive transmitter can be made more omni-directional by employing several

CCRs oriented in different directions, at the expense of increased dust mote size. If a dust

mote employs only one or a few CCRs, the lack of omni-directional transmission has

important consequence on feasible network routing strategies.

Fig.5: Free Spaces Optical Network




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Figure 5 illustrates a free-space optical network utilizing the CCR-based passive

uplink. The BTS contains a laser whose beam illuminates an area containing dust motes.

This beam can be modulated with downlink data, including commands to wake up and

query the dust motes. When the illuminating beam is not modulated, the dust motes can

use their CCRs to transmit uplink data back to the base station. A high frame-rate CCD

video camera at the BTS sees these CCR signals as lights blinking on and off. It decodes

these blinking images to yield the uplink data. This uplink scheme achieves several

kilobits per second over hundreds of meters in full sunlight. At night, in clear, still air, the

range should extend to several kilometers.

Because the camera uses an imaging process to separate the simultaneoustransmissions from dust motes at different locations, we say that it uses space-division

multiplexing. The ability for a video camera to resolve these transmissions is a

consequence of the short wavelength of visible or near-infrared light. This does not

require any coordination among the dust motes, and thus, it does not complicate their

design.

2.3 Challenges

The hardware design has to face many challenges due to the small size of the

Smart Dust. First of all, it is hardly possible to fit current radio communication

technology into Smart Dust both size wise and energy wise. The present radio

communication has large antennas and thus requires larger space. The energy

requirements are also high. So, a more size and power efficient passive laser based

communication schemes have to be adopted. But it also has its share of disadvantages.

Another factor of concern is the energy consumption by the Smart Dust. With

devices so small, batteries present a massive addition of weight. It is therefore important

to use absolutely minimal amounts of energy in communicating the data they collect to

the central hubs, where humans can access it.




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Chapter 3:

TINYOS

3.1 What is TinyOS?

TinyOS is an open-source operating system designed for wireless embedded

sensor networks. The operating system known as TinyOS was originally designed

specifically for smart dust. The TinyOS or Tiny Micro threading Operating System is

similar to Windows in that it is run by each and every mote and only requires 8 kilobytes

of memory to run. TinyOS manages the sensors, power, and communication with other

motes. To save power, the software is designed to allow the motes to “sleep” for over 98

percent of the time. They wake up once a second, collect data for 50 microseconds and

transmit for another 1000 microseconds, and then they return to sleep mode for the next

998,950 microseconds

It features a component-based architecture which enables rapid innovation and

implementation while minimizing code size as required by the severe memory constraints

inherent in sensor networks. TinyOS's component library includes network protocols,

distributed services, sensor drivers, and data acquisition tools – all of which can be used

as-is or be further refined for a custom application. TinyOS's event-driven execution

model enables fine-grained power management yet allows the scheduling flexibility made

necessary by the unpredictable nature of wireless communication and physical world

interfaces.

3.2 Requirements

Four broad requirements motivate the design of TinyOS:




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3.2.1 Limited resources

Motes have very limited physical resources, due to the goals of small size, low

cost, and low power consumption. Current motes consist of about a 1-MIPS processor

and tens of kilobytes of storage.

3.2.2 Reactive concurrency

In a typical sensor network application, a node is responsible for sampling aspects

of its environment through sensors, perhaps manipulating it through actuators,

performing local data processing, transmitting data, routing data for others, and

participating in various distributed processing tasks, such as statistical aggregation or

feature recognition. Many of these events, such as radio management, require real-time

responses. This requires an approach to concurrency management that reduces potential

bugs while respecting resource and timing constraints.

3.2.3 Flexibility

The variation in hardware and applications and the rate of innovation require a

flexible OS that is both application-specific to reduce space and power, and independent

of the boundary between hardware and software. In addition, the OS should support fine-

grain modularity and inter-positioning to simplify reuse and innovation.

3.2.4 Low power

Demands of size and cost, as well as untethered operation make low power

operation a key goal of mote design. Battery density doubles roughly every 50 years,

which makes power an ongoing challenge. Although energy harvesting offers many

promising solutions, at the very small scale of motes people can harvest only Microwatts

of power. This is insufficient for continuous operation of even the most energy-efficient

designs. Given the broad range of applications for sensor networks, TinyOS must not

only address extremely low-power operation, but also provide a great deal of flexibility in

power-management and duty-cycle strategies.




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Chapter 4:

COMMUNICATION

4.1 Communication Technologies

Primarily, two technologies can be used for Communication between the smart

dusts and the BASE station Transceiver (BST), they are as follows:

i. Radio Frequency Transmission

ii. Optical transmission technique

Passive Laser based Communication

Active Laser based Communication

Fiber Optic Communication

All of them have their relative advantages and disadvantages.

4.2 Radio Frequency Transmission

It is based on the generation, propagation and detection of electromagnetic waves

with a frequency range from tens of kHz to hundreds of GHz. It could be used to function

as both the uplink and the downlink. Since RF transceiver typically consists of relatively

complex circuitry, it is impossible to achieve the required low power operation using

such an approach in a smart dust system. When large numbers of motes are involved in

smart dust, RF links may employ alternative multiplexing techniques: time, frequency or

code-division multiplexing. Their use leads to modulation, bandpass filtering,

demodulation circuitry, and additional circuitry, all of which needs to be considered




SMART DUST 2011

based on power consumption. RF communication can be used for smart dust

communication but it poses following problems:

Size of the antenna: Since the size of the antenna should be ¼ of the carrier

wavelength, if we reduce the size of the antenna (which is very difficult to

achieve) the wavelength of the carrier wave will decrease, thus requiring high

frequency transmission. This system will no longer comply with low power

consumption requirement of the small dust.

RF communication can only be achieved by using time, frequency or code

division.

Multiplexing (TDMA, FDMA, or CDMA) each having their own

complications. For TDMA mote should transfer at high bit rate (as high as

aggregate uplink capacity) in absence of other transmission. Beside this, mote

should coordinate their transmission with other mote. In FDMA, the accurate

control of oscillator frequency is required. Since CDMA operates for a

relatively extended time interval, it requires high-speed digital circuitry and it

consumes excessive power. Both FDMA and CDMA should avoid

coordination between dust motes and they require dust motes to be

preprogrammed with unique frequencies or codes in order to prevent such

coordination.




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Fig.6: Full mesh Architecture

4.3 Optical Transmission Technique

4.3.1 Passive Laser based communication

The Smart Dust can employ a passive laser based communication scheme to

establish a bi-directional communication link between dust nodes and a base station

transceiver (BST). For downlink communication (BST to dust), the base station points a

modulated laser beam at a node. The latter uses a simple optical receiver to decode the

incoming message. For uplink communication (dust to BST), the base station points an

un-modulated laser beam at a node, which in turn modulates and reflects back the beam

to the BST. For this, the dust nodes are equipped with a Corner Cube Retro Reflector (CCR). The CCR has the property that any incident ray of light is reflected back to the

source under certain conditions. If one of the mirrors is misaligned, this retro reflection

property is spoiled. The Smart Dust CCR has an electrostatic actuator that can deflect one




SMART DUST 2011

of the mirrors at kilohertz rates. Using this actuator, the incident laser beam is “on-off”

modulated and reflected back to the BST.

This type of design implies a single-hop network topology, where dust nodes

cannot directly communicate with each other, but only with a base station. The base

station can be placed quite far away from the nodes, since the employed laser

communication works over a range of hundreds of meters, provided a free line-of-sight

between the BST and the nodes. Communication may suffer from significant and highly

variable delays if the laser beam is not already pointing at a node that is subject to

communication with the BST. Smart Dust nodes can be highly mobile, since nodes are

small enough to be moved by winds or even to remain suspended in air, buoyed by air

currents.

Advantage of optical links:

Optical transceivers require only simple baseband analog and digital circuitry; no

modulators, active bandpass filters or demodulators are needed.

The short wavelength of visible or near-infrared light (of the order of 1 micron)

makes it possible for a millimeter-scale device to emit a narrow beam (i.e., high

antenna gain can be achieved). A base-station transceiver (BTS) equipped with a compact imaging receiver can

decode the simultaneous transmissions from a large number of dust motes at

different locations within the receiver field of view, which is a form of space-

division multiplexing.

The CCR makes make it possible for dust motes to use passive optical

transmission techniques, i.e., to transmit modulated optical signals without

supplying any optical power.

Requirements for Passive Laser-based Transmission:




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Successful decoding of these simultaneous transmissions requires that dust motes

not block one another’s line of sight to the BTS. Such blockage is unlikely, in

view of the dust motes’ small size.

A second requirement for decoding of simultaneous transmission is that the

images of different dust motes be formed on different pixels in the BTS imaging

receiver. For example, suppose that the BTS views a 17-meter by 17-meter area

containing Smart Dust, and that it uses a high-speed video camera with a 256 by

256 pixel-imaging array. Each pixel views an area about 6.6 centimeters square.

Hence, simultaneous transmissions can be decoded as long as this distance

separates the dust motes.

4.3.2 Active Laser based Communication

Active optical communication typically uses an active-steered laser-diode based

transmitter to send a collimated laser beam to a base station. This system contains a

semiconductor laser, a collimating lens and a beam-steering micro-mirror as shown in

Figure 3. Active optical communication is suitable for peer-to-peer communication,

provided there exist a line of sight path between them. Using MEMS technology, the

components of the active communication network can be made to be small enough to fit

into the smart dust motes.One of the disadvantages of the active transmitter is its relatively high power

consumption. This leads to the use of active optical communication for short duration

burst-mode communication only. In order to minimize the power consumption, the active

transmitter should have some protocol to aim the beams toward the receiver, for example,

using directional beam and an active beam-steering mechanism. These components

would make the design of the dust mote more complicated.

Active communication has the advantage of high power density. This provides

capable for optical wireless communication over enormous distances. Using active

optical communication one can form multi-hop networks. Burst-mode communication

provides the most energy-efficient way to schedule the multi-hop network. The active




SMART DUST 2011

laser-diode transmitter operates at up to several tens of megabits per second for a few

milliseconds.

4.3.3 Fiber-optic communication

Fiber-optical communication employs semiconductor laser, fiber cable and diode

receiver to generate, transfer and detects the optical signal. Its most of the characteristics

matches with that of passive optical communication. The relatively small size of the

optical transceiver is employed with low-power operation. Each dust mote does not need

to have an on board light source to transmit the data. By the using MEMS technology,

Corner cube retro-reflector is employed on each dust mote to modulate uplink data to

base station.

For downlink, a single laser transmitter in base station generates an on-off-keyed

signal containing downlink data and commands. The beam splitter divides the

interrogating signals into the fibers that are connected to each dust mote. After passing

through optical isolator, the signals go into directional coupler. Directional coupler

divided them into two fibers. One of them will be passed while the index-matching

material blocks the other. Finally, after passing GRIN-rod lens, the signals reach to the

receivers of each dust mote. On the uplink, each dust mote is equipped with a CCR. CCR modulates interrogating beams from the base station and reflects these signals back to

fiber cable. The directional coupler divides the signals into two fibers. The signals in the

fiber that is connected to the optical isolator will be blocked, and the signals in the other

fiber will reach to the receiver in the base station.




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Fig.7: Fiber-optic Communication Setup

Fiber-optic communication has advantages and disadvantages over a passive free-

space optical communication. Since optical fiber communication employs fiber cables to

transfer and receive optical signals, it does not require the unbroken line-of-sight, the link

directionality, and human eye safety from laser is maintained. Each dust mote does not

need to employ more than one CCR, and the communication between dust motes and a

base station can be guaranteed. In addition, it has a longer range of communication link

than that of a free space passive optical communication.

However, fiber-optic communication has a limitation on the application. The

optical fiber cables restrict the mobility of dust mote. Since a base station should employ

several optical components for fiber connection to each dust mote, it may complicate

base station design.

Chapter 5:

APPLICATIONS




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Not only does the Smart Dust remain suspended in the air for hours, the air

currents can also move them in the direction of flow. It is very hard to detect the presence

of the Smart Dust and it is even harder to get rid of them once deployed. Moreover it

does not cost much so can be densely deployed. Due to the above-mentioned features,

Smart Dust can be used in varied application fields. These are as follows:

Environmental protection (identification and monitoring of pollution).

Habitat monitoring (observing the behavior of the animals in there natural

habitat).

Military application (monitoring activities in inaccessible areas, accompany

soldiers and alert them to any poisons or dangerous biological substances in the

air).

Indoor/Outdoor Environmental Monitoring

Security and Tracking

Health and Wellness Monitoring (enter human bodies and check for physiological

problems)

Power Monitoring

Inventory Location Awareness

Factory and Process Automation

Structural Monitoring

Monitor traffic and redirecting it

Imagine a suburban neighborhood or an apartment complex with motes that

monitor the water and power meters. Since all of the meters (and motes) in a typical

neighborhood are within 100 feet (30 meters) of each other, the attached motes

could form an ad hoc network amongst themselves. At one end of the neighborhood

is a super-mote with a network connection or a cell-phone link. In this imagined

neighborhood, someone doesn't have to drive a truck through the neighborhood

each month to read the individual water or power meters- the motes pass the data




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along from one to another, and the super-mote transmits it. Measurement can occur

hourly or daily if desired.

A farmer, vineyard owner, or ecologist could equip motes with sensors that detect

temperature, humidity, etc., making each mote a mini weather station. Scattered

throughout a field, vineyard or forest, these motes would allow the tracking of

micro-climates.

A building manager could attach motes to every electrical wire throughout an office

building. These motes would have induction sensors to detect power consumption

on that individual wire and let the building manager see power consumption down

to the individual outlet. If power consumption in the building seems high, the

building manager can track it to an individual tenant. Although this would be

possible to do with wires, with motes it would be far less expensive.

A biologist could equip an endangered animal with a collar containing a mote that

senses position, temperature, etc. As the animal moves around, the mote collects

and stores data from the sensors. In the animal's environment, the biologists could

place zones or strips with data collection motes. When the animal wanders intoone of these zones, the mote in the collar would dump its data to the ad hoc

network in the zone, which would then transmit it to the biologist.

Motes placed every 100 feet on a highway and equipped with sensors to detect

traffic flow could help police recognize where an accident has stopped traffic.

Because no wires are needed, the cost of installation would be relatively low.

The possibilities in implementing Smart Dust are endless. The following are some

of the ideas floating around that show a few of the ways that smart does can affect

our lives in the future:




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The monitoring of weather and seismology – Better prediction of earthquakes and

tornados.

The monitoring of environments on Mars and other planets.

Internal spacecraft monitoring – this can be useful in preventing the shuttle from

crashing due to technical problems by finding them before they occur.

Land to space communication networks – faster communication from earth to

space with real time data.

Chemical and biological sensors - could be used to monitor the purity of drinking

or sea water, to detect hazardous chemical or biological agents in the air or to

locate and destroy tumor cells in the body

Defense related sensor networks – this will be a great help for military action such

as surveillance.

Weapons stockpile monitoring – monitor weapons of mass destruction

Inventory Control – Know where your products are and what shape they're in

anytime, anywhere. Sort of like FedEx tracking on steroids for all products in

your production stream from raw materials to delivered goods.

Product quality monitoring – smart dust can have many positive effects on quality

control: Temperature, humidity monitoring of meat, produce, dairy products, etc.

Smart offices and smart homes –environmental conditions in the office or home

are tailored to the desires of every individual.

Sports – smart dust could bring a whole new aspect to sporting events. Sailboat

racers can monitor the changes in the wind and current to gain an advantage.

Also, think about the possibilities of putting motes on the balls during games to

monitor things such as ball spin and speed.




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Chapter 6:

CONCLUSION AND FUTURE ENHANCEMENT

6.1 Conclusion

The new Smart Dust technology has more future applications that will benefit

society in general in spite of privacy and environmental concerns. There is growing

feeling among researchers of its huge impact on society. The motes could be powered by

solar light, barometric pressure and vibrations in the wall. In the future all belongings will

respond to their owner. Houses and offices would be aware of owner’s presence and

orientation in a given room. Lighting, heating, and cooling will adjust according to theowner’s settings automatically. Cars will know highway conditions on one’s favorite

route home, instantaneous information on speed, history of cars between source and

destination. Every valuable property will have its own sensors that will give instant

information to its owner.

In spite of the design challenges in the size of the mote, power supply,

communication and computation, researchers continue to make progress towards their

main goal of reducing the size of the mote to 1-millimeter cube. Hopefully in the next

couple of years the objectives of the Smart Dust project will be realized, and

commercialization and subsequent use will be widespread throughout society. In the

military for example it could offer an alternative and cheaper way to monitor enemies by

reducing cost, risk to human life and performance. In the future there will be billions of

motes embedded in everything that will be able to sense, compute and communicate with

each other using ultra low power.

6.2 Future Enhancement

There are many ongoing researches on Smart Dust, the main purpose of these

researches is to make Smart Dust mote as small as possible and to make it available at as




SMART DUST 2011

low price as possible. Soon we will see Smart Dust being used in varied application from

all spans of life.

Chapter 7

BIBLIOGRAPHY

Yunbin Song: ”Optical Communication Systems for Smart Dust”

J. M. Kahn, R. H. Katz, K. S. J. Pister: Next Century Challenges:

Mobile Networking for “Smart Dust”

An Introduction to Microelectromechancal System Engineering:

Nadim Maluf, Kirt William

B.A. Warneke, M.D. Scott, B.S. Leibowitz: Distributed Wireless

Sensor Network

http://www.coe.berkeley.edu/labnotes

TinyOS- http://www.tinyos.net

Smart dust. Website:

http://robotics.eecs.berkeley.edu/~pister/SmartDust




http://www.tinyos.net/


http://www.tinyos.net/

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report of SMART DUST