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A

SEMINAR REPORT ON

SENSOR NODES

SUBMITTED IN PARTIAL FULFILLMENT OF

REQUIREMENTS FOR THE AWARD OF THE DEGREE

OF

BACHELOR OF TECHNOLOGY

IN

ELECTRONICS & COMMUNICATION ENGINEERING

SUBMITTED BY

NAVEEN REDDY PADALA 07A91A456

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

ADITYA ENGINEERING COLLEGE(Affiliated to Jawaharlal Nehru Technological University Kakinada)

2007-2011


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CONTENTS

1. Introduction032. History of Sensor Node..05

3. Architecture ..07

4. Components of a Sensor Node.......08

5. Working.................12

6. Early Applications........................................15

7. Applications for Business.....18

8. Cost and Availability ...22

9.Issues..25

10.Conclusion...........32

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ABSTRACTMotes are the smart dust sensors or tiny wireless microelectromechanical sensors

(MEMS) that can detect everything from light to vibrations. With recent breakthroughs in

silicon and fabrication techniques, these "motes" could eventually be the size of a grain of

sand, though each would contain sensors, computing circuits, bidirectional wireless

communications technology and a power supply. With Wireless sensor networks

receiveing considerable interest, the energy constraint inherent in the small battery

powered sensors presents a considerable problem, and much effort being put into

reducing the power consumption and the effective solution MOTES.

This paper enlights the emerging the building blocks of wireless sensor networks

-Motes. It is easy to imagine all sorts of sensors, including sensors for temperature,

light, sound, position, acceleration, vibration, stress, weight, pressure, humidity, etc

Motes would gather scads of data, run computations and communicate that information

using two-way band radio between motes at distances approaching 1,000 feet.

In the future, people imagine shrinking motes to fit into something just a

few millimeters on a side. It is more common for motes today, including batteries and

antenna, to be the size of a pack of cigarettes or even smaller. The flexibility and

reliability offered by motes will place it as fore most sensor technology in the near future.

With recent breakthroughs in silicon and fabrication

techniques, these "motes" could eventually be the size of a grain of sand, though eachwould contain sensors, computing circuits, bidirectional wireless communications

technology and a power supply.

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INTRODU CTION

Motes are tiny, self-contained, battery-powered computers with radio

links, which enable them to communicate and exchange data with one another, and to

self-organize into adhoc networks. The core of a mote is a small, low-cost; low-power

computer.The computer monitors one or more sensors. Motes package together into a

circuit board with networking and application software; interfaces to sensors that can

detect changes in temperature, pressure, moisture, light, sound, or magnetism; and a

wireless radio that can report on their findings--all powered by a pair of AA batteries.

Enabled by the fusion of small, low-cost chips, low-powered radios, and the spread of

wireless networking, motes are a giant leap ahead of traditional sensors that for decades

have measured everything from temperature in buildings to factory machines' vibrations.

Wireless sensor networks enable the monitoring of a variety of

possibly inhospitable environments that include home security, machine-failure

diagnostic, chemical/biological detection, medical and wide habitat monitoring. These

applications require reliable, accurate, fault tolerant and possibly real-time monitoring.

Meanwhile, the low energy and processing capabilities of the nodes require efficient and

energy aware operations.

A Smart Dust mote is an electronic package composed of: an

integrated-circuit radio transmitter and receiver (the combination is called a

transceiver); a microcontroller that controls the operation of the mote; a random-access

memory (RAM) like the one(s) in your computer; a flash memory like the one that

stores pictures in a digital camera; some standard sensors a resistive temperature sensor

and a semiconductor illumination (light) sensor that produces a current when it is

illuminated; an analog-to-digital converter (ADC) that converts the analog temperature

and illumination sensor outputs to digital form for transmission elsewhere; a powersource for the mote (typically a battery); and an antenna used both for transmitting and

receiving signals.

Motes will be applied in industrial settings to reduce plant downtime and enhance

safety.Consider the scenario of a chemical plant that utilizes pipes to transport acidic or

abrasive liquids. The chemical contents of the pipes can gradually weaken them so, to

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prevent accidental chemical releases, plant operators must periodically inspect piping and

other components that may be susceptible to wall thinning caused by erosion/corrosion

(Jona1996). Today, this inspection process is labor intensive for pipes covered with

insulation and for pipes located in confined areas. In the future, smart dust could be

employed to facilitate

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History of Sensor Node

History of development of sensor nodes dates back to 1998 in the Smartdust project . One

of the objectives of this project is to create autonomous sensing and communication in a

cubic millimeter. Though this project ended early on, it has given birth to many more

research projects. They include major research centres in Berkeley NEST and CENS.

The researchers involved in these projects coined the term 'mote' to refer to a sensor

node. Sensor nodes have not increased in power as one would expect from Moore's Law.

They typically have very small computer and storage capabilities compared to desktop

computers. This can be attributed to the low volume of the current market for them and

their use of very low powermicrocontrollers.

Smart dust was conceived in 1998 by Dr. Kris Pister of the UC Berkeley (Hsu, Kahn, and

Pister 1998; Eisenberg 1999). He set out to build a device with a sensor, communication

device, and small computer integrated into a single package. The Defense Advanced

Research Projects Agency (DARPA) 1 funded the project, setting as a goal the

demonstration that a complete sensor/communication system can be integrated into a

cubic millimeter package (Pister 2001). (By comparison, a grain of rice has a volume of

about 5 cubic millimeters.) In the early stages of the project, the team gained experience

by building relatively large motes using components available off the shelf (Pister

2001). 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)

communication2 (Pister 2000). If the mote operated continuously, its battery would last

up to one week (ibid).

During the course of the Smart Dust project, Professor David Culler and

a team of researchers at UC Berkeley created the TinyOS operating system (Yang 2003).

Once installed on a mote, this software is responsible for operating the device, managing

its power consumption, and facilitating communication with other motes (ibid). The

Smart Dust project resulted in laboratory and field demonstrations of a few generations of

motes with names like Clever Dust, Deputy Dust, Daft Dust, and Flashy Dust (Pister

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2001).More importantly, it spurred the interest of numerous other academic and corporate

researchers. Two examples of their work are provided in the following section.

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ARCHITECTURE

sensor node, also known as a 'mote' (chiefly in North America), is a node in a wireless

sensor network that is capable of performing some processing, gathering sensory

information and communicating with other connected nodes in the network. The typical

architecture of the sensor node is shown in the figure .

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COMPONENTS OF A SENSOR NODE

The main components of a sensor node as seen from the figure are microcontroller,

transceiver, external memory,power source and one or more sensors.

Microcontroller

Microcontroller performs tasks, processes data and controls the functionality of other

components in the sensor node. Other alternatives that can be used as a controller are:

General purpose desktopmicroprocessor, Digital signal processors, Field Programmable

Gate Array and Application-specific integrated circuit. Microcontrollers are the most

suitable choice for a sensor node. Each of the four choices has their own advantages and

disadvantages. Microcontrollers are the best choices for embedded systems. Because of

their flexibility to connect to other devices, programmable, power consumption is less, as

these devices can go into a sleep state and part of controller can be active. In a general

purpose microprocessor the power consumption is more than the microcontroller,

therefore it is not a suitable choice for sensor node. Digital Signal Processors are

appropriate for broadband wireless communication. But in Wireless Sensor Networks, the

wireless communication should be modest i.e., simpler, easier to processmodulationand

signal processing tasks of actual sensing of data is less complicated. Therefore the

advantages of DSP's is not that much of importance to wireless sensor node. Field

Programmable Gate Arrays can be reprogrammed and reconfigured according to

requirements, but it takes time and energy. Therefore FPGA's is not advisable.

Application Specific Integrated Circuits are specialized processors designed for a given

application. ASIC's provide the functionality in the form of hardware, but

microcontrollers provide it through software.

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TRANSCEIVER

Sensor nodes make use ofISM band which gives free radio, huge spectrum allocation

and global availability. The various choices of wireless transmission media are Radio

frequency, Optical communication (Laser) and Infrared. Laser requires less energy, but

needs line-of-sight for communication and also sensitive to atmospheric conditions.

Infrared like laser, needs no antenna but is limited in its broadcasting capacity. Radio

Frequency (RF) based communication is the most relevant that fits to most of the WSN

applications. WSNs use the communication frequencies between about 433 MHz and 2.4

GHz. The functionality of both transmitterandreceiverare combined into a single device

know as transceivers are used in sensor nodes. Transceivers lack unique identifier. The

operational states are Transmit, Receive, Idle and Sleep.

Current generation radios have a built-in state machines that perform this operation

automatically. Radios used in transceivers operate in four different modes: Transmit,

Receive, Idle, and Sleep. Radios operating in Idle mode results in power consumption,

almost equal to power consumed in Receive mode. Thus it is better to completely

shutdown the radios rather than in the Idle mode when it is not Transmitting or

Receiving. And also significant amount of power is consumed when switching from

Sleep mode to Transmit mode to transmit a packet.

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EXTERNAL MEMORY

From an energy perspective, the most relevant kinds of memory are on-chip memory of a

microcontroller andFlash memory - off-chip RAM is rarely if ever used. Flash memories

are used due to its cost and storage capacity. Memory requirements are very much

application dependent. Two categories of memory based on the purpose of storage a)

User memory used for storing application related or personal data. b) Program memory

used for programming the device. This memory also contains identification data of the

device if any.

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POWER SOURCE

Power consumption in the sensor node is for the Sensing, Communication and Data

Processing. More energy is required for data communication in sensor node. Energy

expenditure is less for sensing and data processing. The energy cost of transmitting 1 Kb

a distance of 100 m is approximately the same as that for the executing 3 million

instructions by 100 million instructions per second/W processor. Power is stored either in

Batteries or Capacitors. Batteries are the main source of power supply for sensor nodes.

Namely two types of batteries used are chargeable and non-rechargeable. They are also

classified according to electrochemical material used for electrode such asNiCd(nickel-

cadmium), NiZn (nickel-zinc), Nimh (nickel metal hydride), and Lithium-Ion. Current

sensors are developed which are able to renew their energy from solar, temperature, or

vibration. Two major power saving policies used are Dynamic Power Management

(DPM) and Dynamic Voltage Scaling (DVS)[5]. DPM takes care of shutting down parts

of sensor node which are not currently used or active. DVS scheme varies the power

levels depending on the non-deterministic workload. By varying the voltage along with

the frequency, it is possible to obtain quadratic reduction in power consumption.

\

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SENSORS

Sensors are hardware devices that produce measurable response to a change in a physical

condition like temperature and pressure. Sensors sense or measure physical data of the

area to be monitored. The continual analog signalsensed by the sensors is digitized by an

Analog-to-digital converterand sent to controllers for further processing. Characteristics

and requirements of Sensor node should be small size, consume extremely low energy,

operate in high volumetric densities, be autonomous and operate unattended, and be

adaptive to the environment. As wireless sensor nodes are micro-electronic sensor device,

can only be equipped with a limited power source of less than 0.5 Ah and 1.2 V. Sensors

are classified into three categories.

Passive, Omni Directional Sensors: Passive sensors sense the data without

actually manipulating the environment by active probing. They are self powered

i.e energy is needed only to amplify their analog signal. There is no notion of

direction involved in these measurements.

Passive, narrow-beam sensors: These sensors are passive but they have well-

defined notion of direction of measurement. Typical example is camera.

Active Sensors: These group of sensors actively probe the environment, for

example, a sonar or radar sensor or some type of seismic sensor, which generate

shock waves by small explosions.

The overall theoretical work on WSNs considers Passive, Omni directional sensors.

Each sensor node has a certain area of coverage for which it can reliably and accurately

report the particular quantity that it is observing. Several sources of power consumption

in sensors are a) Signal sampling and conversion of physical signals to electrical ones, b)

signal conditioning, and c) analog-to-digital conversion. Spatial density of sensor nodes

in the field may be as high as 20 nodes/ m3 .

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WORKING

The mote relays the collected data to its neighboring motes and then to a specified

destination where it is processed. This sensory input, when gathered from all the motes

and analyzed by more traditional computers, paints a comprehensive, highresolution.

The motes well use called Mica2dot motes (dont ask) also have three light-

emitting diodes (LEDs) on them. The red LED indicates when the mote is turned on; the

yellow and green LEDs flash when mote-to-mote communication is occurring. The

Experiment Guide describes this more fully.

computer

software

operating system TinyOS was developed in Berkeleys Computer Science Division to

control Mote operation. When wireless motes are first dispersed in an area a room, a

hallway, a building, or in a meadow they autonomously attempt to set up a network

along which they can send information from one mote to another. Somewhere, one mote

is plugged into a special printed circuit board (PCB) that is connected to the serial port of

a computer, such as a laptop. This board is known as a base station; its function is to

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collect the data provided to it by the assembly of motes.

Figure shows a magnified view of one of the Smart Dust wireless sensor

motes. Several of its components are identified; beneath the printed circuit board that

you see is an integrated circuit like those used in portable telephones to drive an antenna

connected to the mote for transmitting the mote identification and measured sensor data

to the base station.

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Figure shows magnified view of the Smart Dust mote.

The wireless telephone chip is beneath this printed circuit board. The mote connects to a

short antenna for transmitting and receiving radio waves printed circuit board.

Each mote in the network has a unique identifier that it uses to

preface each of its transmissions. Every mote transmits any sensor data that it has taken,

along with information from other motes sent to it for passing along to the base station.

If the proper software has been installed in the base stations computer, the network

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topology can be displayed on the base stations monitor. One should thus be able to

observe when motes are added to the network, or when they leave it. The sensor data

taken by each mote could also be displayed, processed and stored by that computer.

EARLY APPLICATIONS

In a demonstration, smart dust was used to detect vehicles traveling through an isolated

desert area in Palm Springs, California. The experiment, conducted with the U.S.

Marine Corps, began when an unmanned airborne vehicle (UAV) flew over the area,

dropped 8 motes (which were wrapped in protective foam) and then departed (Hill 2003).

After deployment, the motes organized themselves into a network and then began to

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lookout for moving vehicles5; when a vehicle was detected, the mote recorded tracking

information about the event. Eventually, the UAV plane flew over the scene and

retrieved each nodes tracking data and then, finally, returned to its home based to

deliver the data it collected. The experimenters successfully downloaded the vehicle

tracking information from the plane for display on a personal computer. In doing so, they

showed how smart dust can be used by military and law enforcement personnel to

unobtrusively monitor movement within a region. Scientists at the University of

California at San Diego approach smart dust from a biotechnology perspective to

produce motes from chemical compounds rather than electrical circuitry (Sailor, Bhatia,

Cunin 2002). While not yet commercially available, their motes have proved useful in

laboratory environments (Link and Sailor 2003). One experiment demonstrated the use

of smart dust to detect the presence of hydrocarbon vapors from approximately 65 feet

away (Schmedake, T. A. et al. 2002). In this standoff detection, the researchers placed

porous silicon smart dust particles in a gas dosing chamber and monitored the

experiment from a distance (ibid, p. 1270). Using a laser to illuminate the smart dust and

a telescope outfitted with measurement equipment, the team detected the hydrocarbon

vapors based on the changes in the light reflected from the smart dust after it had

chemically reacted with the hydrocarbon vapors. While the experiment was limited to

hydrocarbon vapors, the researchers predict that with appropriate chemical

modification, the smart dust sensors used can specifically detect biomolecules,

explosives, (and) chemical warfare agents such as Sarin (ibid, p. 1270). As such, the

standoff detection capability of smart dust will be of value to military and international

weapons monitoring agencies

SMART DUST TODAYTiny, ubiquitous, low-cost, smart dust motes have not yet been realized, however, some

reasonably small motes are commercially available. One of these, the MICA2DOT6, is

available from Crossbow Technology, Inc. The unit becomes a mote once a small sensor

board, coin battery, and antenna are added to the product (Crossbow 2004b). In addition,

Crossbow sells larger motes (about the size of a deck of cards), which are compatible

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with more types of sensors. Other commercially available motes are sold by Dust

Networks. This company offers motes which are about the size of a matchbook,

operate on two AA batteries and have a 5-year battery life (Metz 2004). Many of the

sensors available for smart dust motes are micro-electromechanical systems (MEMS)

(Hoffman 2003). MEMS contain microscopic devices, usually with a moving part,

integrated together with at least some electronic circuitry (Clarke 2002). MEMS are in

use today in modern automotive airbags. These are dot-sized motion sensors (that)

measure deceleration and provide its data to a small computer which decides when to

deploy an airbag (Eisenberg 1999). In late 2003, UC Berkeley announced a

revolutionary mote called Spec. The device is complete with sensors and a

communication system yet, without its battery and a few additional mote components,

Spec is about the size of an aspirin tablet.7 Because the device fits on a single chip, it

costs less to produce and thus, according to Professor David Culler, opens the path to

very low cost deployments of a large number of motes (qtd. in Yang 2003).

Additionally, the mote operates with low power consumption its transmitter requires

1,000 times less power than a cell phone (ibid). This is possible because the device is

configured only to talk to nearby motes rather than across a room to a base station

APPLICATIONS

Off the shelf mote systems can be configured with sensors for numerous properties

including temperature, humidity, barometric pressure, light intensity, acceleration

(vibration), magnetism, and acoustic levels (Crossbow 2004a). And some mote sensors

can determine their locations using the national Global Positioning System (ibid). The

combination of some of these capabilities in a well-designed sensor network yields

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numerous potential applications. To illustrate, this section will review some recent

commercial and experimental applications.

Demonstrated ApplicationsEnergy company BP is experimenting with motes on the Loch Rannoch, an 885-foot oil

tanker, to determine if they are useful in predicting failures of onboard machinery.

(Economist 2004). The firm placed 160 motes near some of the ships equipment to

measure things like vibrations in the ships pumps, compressors, and engines as an

indicator of potential failure (Takahashi 2004). The configuration is set up to initiate an

alert if it detects unusual vibration or motion. Technicians responding to the alert could

fix the problem before it results in a more serious condition. Since ships carry limited

amounts of onboard tools and spare parts, catching a problem before it becomes serious

could Recently, Accenture Technology Labs installed a wireless sensor network at

Pickberry Vineyards in order to demonstrate the benefits of its Remote Sensor Network

(Accenture 2004). The experiment required placement of motes across a 30 acre area to

continuously sense humidity, wind, water, and soil and air temperature (ibid). The

system designers made the mote data available on the World Wide Web to authorized

users by configuring the system to upload the sensor data from the mote base station to

the Internet via a cellular telephone link.The sensors provide information that will allow

Pickberry personnel to, based on soil moisture and air humidity, optimize watering

schedules for a specific area (ibid). Also, the setup provides prompt notice of events

such as frost, disease, and pests (ibid). Armed with this information, Pickberry

management may be able to improve the yield of its crop and lower its costs. In 2002,

motes were applied by John Anderson, a field biologist, to solve an environmental

monitoring problem (Schmidt 2004). Dr. Anderson wished to determine the needs of a

species of seabirds (Leachs Storm-Petrels) that nest on Great Duck Island, Maine. This

is a challenge because the birds only return to their burrows at night, after a feeding at sea

during the day (eNature 2002). In order to learn more about the birds, Dr. Anderson has

had to get down on his stomach and stick an arm into the burrows, which scares the

petrels and threatens the survival of their young (Schmidt 2004). Now, he can simply

hop on the Internet. He and his team installed a smart dust network with sensors that

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detect the presence of the birds and also monitor the temperature, humidity, and

barometric pressure in a region (Schmidt 2004).The sensors transmit their readings to a

nearby base station which is connected to the Internet. Because of smart dust, researchers

may now gather real time habitat data from the Internet9 without intruding on the nesting

birds. Dan Bertocchini, an energy manager for supermarket chain Supervalu, Inc., is

experimenting with 19 motes (from Dust Networks) in one of the chains Minneapolis

stores (Dragoon 2005).Over two-thirds of the chains stores do not have submeters to

pinpoint the energy usage of specific pieces of equipment such as refrigeration racks and

condensers (ibid). By placing wireless sensors on individual devices in the store, Mr.

Bertocchini can pinpoint the energy use of specific pieces of equipment and use the

information to root out energy waste by targeting specific machines for repair or

adjustment. His approach is unique because he does not necessarily plan to put sensors in

every store; instead, he will simply move a set of sensors from store to store to perform

energy consumption studies. Given that refrigeration is a significant expense for grocery

stores, the experiment is well positioned to improve the profits of Supervalu (ibid).

Potential Applications

Steve Glaser, an associate professor at UC Berkeley is investigating the usefulness of

smart dust in evaluating the structural soundness of buildings and other structures

(Pescovitz 2001).The approach employs motes equipped with seismic accelerometers to

detect slight movements in building support beams and columns. Data from these motes

would be of value after a building is suspected of sustaining earthquake damage because

the data could be used to certify the structural soundness of the building. An alternative

means of identifying beam buckling and structural bruises are tearing down downs of

sheetrock (ibid). Clearly, a relativelysmall investment in smart dust motes could pay off

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if a building could be deemed safe for reentry in a matter of hours rather than closing the

building for months to undergo a detailed inspection (ibid) Science Applications

International Corp., a government contractor, is using smart dust to develop an advanced

perimeter security system for the U.S. military (Eng 2004). The system will provide

an inexpensive means of persistent surveillance that is easy for soldiers to install and

maintain (ibid). This project illustrates how smart dust can be used to implement a

security system. Similar technologies could be used to build low cost home and office

security systems which can be installed easily and quickly (Bigelow 2004). Smart dust

lends itself to energy saving initiatives. An office building could be outfitted with

hundreds of motes that sense light and temperature levels as well as determine when

people are present in a room or region (Manjoo 2001). The smart dust network would

then provide information to a controller that could turn off the lights when a room was

empty and adjust the air conditioning or heating to save costs in a region that is vacant.

And since the system would be automatic instead of relying on a human to remember to

flip a switch, savings are maximized. Mike Horton, CEO of Crossbow, summed up the

benefits in an interview with a newspaper columnist: We think on air conditioning

costs, motes could save 20 percent on electrical bills, and theyre 50 percent to 80 percent

cheaper to install than wired sensors In another application, motes will soon be used for

remote environmental monitoring in an effort to preserve the painted walls and ceilings

of Buddhist temples located in caves near the Chinese town of Dunhuang (Pescovitz

2003, cf. Weintruab 2004). Conservationists presently monitor the caves environments

to identify the conditions causing deterioration of the paintings. The issue is that to get

information from the existing weather station, technicians have to enter the caves to

gather the data, and their very presence adds to the degradation (Weintruab 2004).

Steven Glaser, Assistant Professor of Civil and Environmental Engineering at UC

Berkeley, and his team will install motes that monitor temperature, barometric pressure,

humidity, and vibration (Pescovitz 2003 p. 1). The benefit of the dust motes is that now,

a technician can take readings without unlocking and entering the caves (ibid, p. 2).

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COST AND AVAILABILITY

Smart dust products are available to early adopters in the form of wireless sensors that

become part of a communication network. As discussed these motes are not dust-sized

they range in size from that of a stack of three U.S. quarters to the size of a deck of

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playing cards. Several manufacturers offer prepackaged solutions for building controls,

industrial monitoring, and security; these include, but are not limited to: Dust Networks,

Millennial Net, and Sensicast. Each has similar offerings of hardware and the associated

software required to operate it, but the later two target their product lines to original

equipment manufacturers and system integrators (such as management and technology

consulting firms). Another vendor, Ember, sells computer chips and embedded software

to meet the needs of mote manufacturers(Ember 2005).Experimenters and researchers

with interest in smart dust may purchase products from Crossbow Technology and

MicroStrain. Crossbows motes can be outfitted with sensors that detect phenomena such

as acceleration, barometric pressure, position, light intensity, sound, magnetic field,

humidity, and temperature (Crossbow 2004a). MicroStrains motes can be used for

industrial monitoring; that firm offers wireless sensors which perform the functions of an

accelerometer, strain gauge, or thermocouple (MicroStrain 2005).SkyeTek, Inc. offers an

RFID reader, the SkyeRead M1-Mini, that connects with the Crossbow MICA2DOT

wireless sensor platform to form an RFID reader mote (Goode 2004). Acolumnist

describing configuration noted that [t]he sensor and the reader are each about the size of

three stacked quarters and that [t]he MICA2DOT can run up to seven years on a coin

cell battery (ibid). The resulting RFID reader mote is compatible with multiple brands

of RFID tags and it would be useful in applications where the reader is close to the tag --

the product data sheet indicates that when operating, the reader must be within

approximately 3 of the tag (SkyeTek 2005). This range doubles if an external antenna is

added to the reader, but this would make the mote configuration larger. However, the

mote platform itself interacts with its communication base station in a

normal fashion; the base station can be up to about 160 feet away from its motes (ibid).

Prices for smart dust implementations vary depending of the desired mote capabilities,

installation requirements, and the volume of the purchase. For example, a recent

Sensicast installation which monitors industrial motors in a California nuclear power

plant cost about 500 per mote plus an additional $500 each for installation to cover the

paperwork and analysis that must precede any change in a nuclear power plant

(Dragoon 2005). After smart dust is sprinkled in a remote or desolate area to accomplish

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a monitoring function, it is not easily or inexpensively retrieved. If a mote fails and is

consequently abandoned by its owner, there is an environmental impact.

But a simple Sensicast building control application would only cost about $250 to $350

per mote (ibid). The price for motes from Crossbow is about $150 each, but for volume

purchases, the price per unit plummets to as low as $40 (Bigelow 2004). The CEO of

Crossbow expects prices to drop to about $10 or less per unit in the near future (qtd. in

Bigelow 2004). Also, for about $2000, experimenters may purchase a kit from Crossbow

which includes 8 mote platforms, sensors, and a base station board (Crossbow 2005).

The base station board is in the form of a computer card which can be installed in a

typical personal or laptop computer. One factor to consider when estimating the costs of

smart dust networks is ease of installation. Battery operated motes do not require the

installation of additional electrical wiring and their installation simply requires a

screwdriver (Dragoon 2005). In comparison to traditional wired sensors, a smart dust

mote requires no wiring and this results in both lower labor and materials costs. Clearly,

early adopters have several commercial smart dust products available to them in the price

range of a few hundred dollars. Late adopters can expect lower prices as the price per

mote falls. This is supported by an Intel report excerpt: Researchers at Intel expect that,

with re-engineering, Moore's Law and volume production, motes could drop in price to

less than $5 each over the next several years (Intel 2005). The Intel report utilizes

Moores Law, which postulates that the number

ISSUES

The development and use of smart dust raises some issues and concerns for

stakeholders.These include privacy issues, potential system security weaknesses, the need

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for standards, and the environmental impacts of smart dust. Each of these issues is

discussed below

PrivacyIts easy to imagine that tiny smart dust sensors could be used for mischievous, illegal, or

unethical purposes. Corporations, governments, and individuals could use motes to

monitor people without their knowledge. And smart dust could become the tool of

choice for corporate espionage. Privacy issues such as these have been raised before. In

one case, during an interview with smart dust inventor Kris Pister, a reporter asked about

the dark side of the technology. Dr. Pister replied, I believe that the benefits will far,

far outweigh the drawbacks, but Im hardly unbiased (qtd. in Edwards 2001). These

issues are not easily resolved, but as smart dust becomes smaller, cheaper, and more

prevalent, privacy concerns are likely to increase.

Security

Smart dust motes, as networked computing devices, are susceptible to security concerns

similar to that of computers on the Internet. One of these susceptibilities is due to the fact

that motes in a network are reprogrammable. This feature allows an administrator to

update the software on a single mote and then command it to pass the update along to all

the other motes in the network (Culler and Mulder 2004). Although the mote identity

verification algorithms in the TinyOS operating system would make it difficult, this mote

software feature could be exploited by hackers and eavesdroppers (ibid). In applications

that gather sensitive data, system designers should be aware that there is a risk that the

data could be compromised.

Standards

As interest in smart dust increases and more manufacturers produce motes, end users will

have more choices when building a system. However, not all smart dust devices would

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work effectively together without standards. Fortunately, a set of standards is

forthcoming an alliance of industry leaders has proposed the ZigBee10 standards

(Economist 2004). Once agreed upon by industry and released by the Institute of

Electrical and Electronics Engineers (IEEE), the standards will apply to residential,

industrial, and building controls (ibid). And the alliance is well positioned to draft

additional standards should the need arise due to the discovery of new applications for the

technology.

Environmental Impacts

After smart dust is sprinkled in a remote or desolate area to accomplish a monitoring

function, it is not easily or inexpensively retrieved. If a mote fails and is consequently

abandoned by its owner, there is an environmental impact. A motes environmentally

unfriendly components include integrated circuits, a battery, and a printed circuit board.

Clearly, motes have environmental impacts that should be considered by users. It is

somewhat ironic that negative environmental consequences could arise from the use of

smart dust for an environmentally sound purpose such as protecting a forest from fires.

Some environmental concerns might be raised about motes that draw on radioactive

power sources. At these time, commercially available motes do not use radioactive

power sources, but a limited amount of research in the area has been completed (Webb2004). The appeal of these special power sources is the amount of energy that a very tiny

battery can produce. This has been demonstrated by Cornell University scientists who

developed an isotope-based cubic millimeter-sized battery that could supply power to a

mote for decades (ibid, p. 30). An atomic scientist, Stephen Schwartz, said in an article

that motes with these types are batteries arent likely to be very dangerous unless you

ate them, or threw them in the fire and inhaled the smoke (qtd. in Eisenberg 2002).

However, employees and consumers may object to living and working in proximity to

radiation sources. And there are no guarantees that used motes with radioactive power

sources would be retrieved and disposed of properly..

ADVANTAGES

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Bi-directional communications

Compatibility with technologies like RFID

Effective decrease in the cost of motes has been dropping steadily. Prices range

from $50 to $100 each today, and there is an anticipation that they will fall to $1

within five years.

Self contained battery and there by decrease in power consumption.

Provide security by protecting the private information.

APPLICATIONS

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Home automation:The network used off-the-shelf motion sensors to detect

movements, pressure sensors in chairs to tell whether a person was sitting in

them, contact and magnetic switches to sense the opening of drawers and cabinets

in the kitchen, radio frequency identification tags in her shoes, and antennas to

sense the tags when she entered the kitchen.

Biomedical/ Medical Health Monitors: Glucose, Heart rate, Cancer

detection, Chronic Diseases, Artificial retina, Cochlear implant, Hospital Sensors,

Monitor vital signs, Record anomalies and also in Networked Heart.

Defense: In Defense it is mainly used check the battlefield conditions and to

trace out the enemy and their movements.

Agriculture:A farmer, vineyard owner, or ecologist could equip motes withsensors thatdetect temperature, humidity, etc., making each mote a mini weather

station.

Measurement of power: 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.

Traffic management and monitoring: 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.Future cars could use wireless

sensors to1.Handle Accidents 2. Handle Thefts. Sensors embedded in the roads to

monitor traffic flows and provide real-time route updates. It is also finds its

application in construction of buildings and maintaining machineries.As interest

in smart dust increases and more manufacturers produce

motes, end users will have more choices when building a system. However,

not all smart dust devices would work effectively together without standards.

THE FUTURE

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The figure shows a sensor size compared compared to that of a nib of a ball pen .The chip

contains all of the components found in a mote: a CPU, memory, an A/D converter for

reading sensor data and a radio transmitter. To complete the package you attach the

sensor(s), a battery and an antenna. The cost of the chip will be less than a dollar when it

is mass

production is

done. So the

future for

motes in senors

is facilitated by

by its vast

advantages.

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CONCLUSION

Wireless sensor networks using motes have been gaining momentum with many applications

have being proposed. They have the potential to revolutionize human-computer interactions.

Availability of sensors will lead to new and exciting applications. It is estimated that by 2008,

there could be 100 million wireless sensors in use, up from about 200,000 today. The worldwide

market for wireless sensors, it says, will grow from $100 million this year to more than $1 billion

by 2009. Thus we can conclude that the motes can create a proactive computing world in which

a multitude of unseen, connected computing nodes automatically acquire and act on real-time

data about a physical environment, helping to improve lives, promoting a better understanding of

the world and enabling people to become more productive.

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REFERENCES

http://www.intel.com

http://www.rense.com

http://www-inst.eecs.berkeley

http://www.nwfusion.com
http://www.nwfusion.com/http://www.nwfusion.com/

sensor node

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