Smart Dust Communicating with a Cubic- Millimeter Computer

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Smart DustCommunicatingwith a
Cubic-Millimeter Computer
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• Table of Contents
• Introduction
• Background
• Basic Idea
• Technologies used
• Current Scenario
• Future Prospects
• Conclusion

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Introduction

• What is Smart Dust?
• Smart dust devices are tiny wireless micro
  electro mechanical sensors (MEMS) that can detect
  everything from light to vibrations.
• Also called Motes
• These motes could eventually be the size of a
  grain of sand, though each would contain sensors,
  computing circuits, bi-directional wireless
  communications technology and a power supply.
• 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.
• Sensors may include one or more temperature,
  pressure, vibration, acceleration, light,
  magnetic, or acoustic devices. Some of the more
  sophisticated sensors also include the ability to
  perform chemical analysis to identify airborne or
  liquid substances.

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Continued

• Smart dust has wide range of applications in
  almost all fields. For example, the military can
  use them to gather information on battlefields,
  and engineers can mix them into concrete and use
  them to internally monitor the health of
  buildings and bridges.

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Background

• Conceived by Dr. Kris Pister of University of
  California Berkeley
• The Defence Advanced Research Projects Agency
  (DARPA) was among the original patrons of the
  mote idea. One of the initial mote ideas
  implemented for DARPA allows motes to sense
  battlefield conditions.

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THE BASIC IDEA

• The mote concept creates a new way of thinking
  about computers, but the basic idea is pretty
  simple
• The core of a mote is a small, low-cost,
  low-power computer.
• The computer monitors one or more sensors ,
  including sensors for temperature, light, sound,
  position, acceleration, vibration, etc. Not all
  mote applications require sensors, but sensing
  applications are very common.
• The computer connects to the outside world with a
  radio link that allows a mote to transmit at a
  distance of about 10 to 200 feet. Power
  consumption, size and cost are the barriers to
  longer distances. Since a fundamental concept
  with motes is tiny size, small and low-power
  radios are normal.

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Continued

• Motes can either run on batteries, or they can
  tap into the power grid in certain applications.
  As motes shrink in size and power consumption
  solar power or even vibration power can be used
  to keep them running.
• All of these parts are packaged together in a
  container of the size of a stack of five or six
  quarters, or the size of a pack of cigarettes. In
  the future, people imagine shrinking motes to fit
  into something just a few millimetres on a side.
  The battery is usually the biggest part of the
  package right now.

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TECNOLOGIES USED

• Smart Dust combines the following three
  technologies 
• Digital Circuitry
• MEMS (Micro-Electro-Mechanical Systems)
• RF (Radio Frequency) Wireless Communication
  Technology

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• Digital Circuitry
• Micro electronic integrated circuits can be
  thought of as the brains of a system and MEMS
  augments this decision-making capability with
  eyes and arms, to allow micro-systems to
  sense and control the environment. Because MEMS
  devices are manufactured using batch fabrication
  techniques similar to those used for integrated
  circuits, unprecedented levels of functionality,
  reliability, and sophistication can be placed on
  a small silicon chip at a relatively low cost.

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• MEMS SENSORS
• Smart Dust devices use MEMS technology sensors.
  Micro-Electro-Mechanical Systems (MEMS) is the
  integration of mechanical elements, sensors,
  actuators, and electronics on a common silicon
  substrate through micro fabrication technology.
  The micro mechanical components are fabricated
  using compatible micromachining processes.
• Sensors gather information from the environment
  through measuring mechanical, thermal,
  biological, chemical, optical or magnetic
  phenomena , electronics then processes the
  information derived from the sensors and through
  some decision making capability direct the
  actuator to respond by moving, positioning,
  regulating, pumping and filtering for some
  desired outcome or purpose.

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Continued

• The material used in these sensors is an
  amorphous ribbon of alloy that is manufactured
  softly magnetic by quick cooling. Example, an
  alloy of iron, molybdenum, boron and silicon.
  Magnetically soft materials have no strong fixed
  magnetic field even though they contain iron . To
  use these strips as temperature and stress
  sensors, an activator must be passed near the
  sensor strips.
• A simple loop that generates a magnetic field
  activates the sensors from a distance. This
  magnetic field is not blocked by any material on
  the road surface or concrete and is not altered
  by the presence of iron material. These simple
  sensor strips provide a consistent temperature
  reading. These sensors can also be immersed in
  water or other liquids and can provide not only
  temperature but also viscosity, liquid density
  and surface tension measurements.

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WIRELESS COMMUNICATION

• A wireless communication system is required for
  sending and receiving data from distributed
  sensor network or smart dust systems.
• Available wireless communication architecture
  for smart dust satisfies a number of
  requirements.
• It supports bi-directional communication between
  a central transceiver and up to 1000 dust motes.
  The downlink (central trans-receiver to dust
  motes) broadcasts to all of the dust motes at a
  bit rate of several kbps. The uplink (dust motes
  to central trans-receiver) permits dust motes to
  convey at about 1 kbps, an aggregate throughput
  of 1 Mbps.

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Continued

• The central transceiver is able to resolve the
  position of each dust mote in an angular
  resolution of the order of one by hundredth of
  the field of view.
• The link operates over a range of at least
  several 100 meters.
• The dust mote transmitter occupies a volume of
  the order of one cubic millimetre and consumes an
  average power not exceeding one microwatt.
• If possible uplink and downlink should afford a
  low probability of interception.

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Operation of Motes

• The mote includes sensing, computing, power, and
  communications sections . Volume puts a severe
  constraint on energy since we do not have much
  room for batteries or large solar cells. Thus,
  the motes must operate efficiently and conserve
  energy whenever possible.
• Most of the time, the majority of the mote is
  powered off with only a clock and a few timers
  running . When a timer expires, it powers up a
  part of the mote to carry out a job, then powers
  off
• A few of the timers control the sensors. When one
  of these timers expires, it powers up the
  corresponding sensor, takes a sample, and
  converts it to a digital word. If the data is
  interesting, it may either be stored directly in
  the SRAM or the micro controller is powered up to
  perform more complex operations with it. When
  this task is complete, everything is again
  powered down and the timer begins counting again.

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• Another timer controls the receiver. When that
  timer expires, the receiver powers up and looks
  for an incoming packet. If it doesnt see one
  after a certain length of time, it is powered
  down again .
• In response to a message or to another timer
  expiring, the micro controller will assemble a
  packet containing sensor data or a message and
  transmit it using either the corner cube retro
  reflector or the laser diode, depending on which
  it has.

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• The communication can be in 3 ways-
• Radio-Frequency Communications
• Optical Communication active dust mode
  transmitters
• Optical Communication passive dust mode
  transmitters

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Radio-Frequency Communications

• Radio frequency communication is one of the
  well-developed communication systems.
• 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.

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Radio-Frequency Communications

• Pros
• Long range
• Line-of-sight path not required
• Not severely affected by rain, fog or atmospheric
  turbulence
• Cons
• Antenna may be too large for dust motes
• Requires modulator, demodulator, filtering (power
  consumption)
• Requires complex multiplexing scheme (TDMA, FDMA,
  CDMA)

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Optical Communication Active Dust Mote
Transmitter

• It uses an active steered onboard laser diode
  based transmitter to send a collimated laser beam
  to a station
• It consist of a laser diode, collimating lens and
  beam steering mirrors for the communication
• With the laser diode and the set of beam scanning
  mirrors, we can transmit data in any direction
  desired, allowing the mote to communicate with
  other Smart Dust motes.

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• Pros
• Longer range than passive links (up to about 10
  km)
• Higher bit rates than passive links (up to about
  1 Mbps)
• With multi-hop, avoids need for every dust mote
  to have line-of-sight path to base station
• Utilizes space-division multiplexing
• Only baseband electronics are required
• Cons
• Requires protocol to steer directional
  transmitters
• Requires higher power than passive transmitter
• Affected by rain, fog, atmospheric turbulence

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Optical Communication Passive Dust Mode
Transmitters
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Corner Cube Reflector (CCR)

• The base of the retro reflector is a MEMS flap
  that modulates the reflected beam
•  One of the three mirrors mounted on a spring at
  an angle slightly a skew from perpendicularity to
  the other mirrors.
• In this position, because the light entering the
  CCR does not return along the same entry path,
  little light returns to the source-a digital 0
• Applying voltage between this mirror and an
  electrode beneath it causes the light entering
  the CCR to return to its source-a digital 1.

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Continued

• A CCD video camera at the BTS sees the CCR
  signals as lights blinking on and off. It decodes
  these blinking images to yield the uplink data.
• This technique is substantially more energy
  efficient than actually generating some
  radiation.

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• Pros
• Dust motes need not radiate power, nor steer beam
• Exploits asymmetry powerful base station,
  low-power dust motes
• Utilizes space-division multiplexing
• Only baseband electronics are required
• Cons
• Requires line-of-sight path to base station
• Short range (up to about 1 km)
• Bit rate limited to about 10 kbps
• Affected by rain, fog, atmospheric turbulence

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Generations of Mote

• Golem Dust is solar powered with bi-directional
• communications and sensing (acceleration and
• ambient light). Shaped like a cubicle, the mote
• is 11.7-cubic millimetres and could fit more
  than
• a dozen on a penny.
• Daft Dust is a little larger. At 63-cmm, it is a
  bi-
• directional communication mote that is shaped
• more like an upside-down bowl.
• Flashy Dust is a 138-cmm unidirectional
• communication and sensing (ambient light) mote.

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Applications

• Environmental monitoring
• A farmer, vineyard owner, or ecologist could
  equip motes with sensors that detect temperature,
  humidity, etc.
• Monitor power consumption of household
  appliances
• The motes would log power and water consumption
  for a customer. When a truck drives by, the motes
  get a signal from the truck and they send their
  data.
• Measuring structural integrity of a building or
  any other structure
• The mote embedded into the concrete could have a
  sensor on it that can detect the salt
  concentration within the concrete or vibration,
  stress, temperature swings, cracking, etc.

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Continued

• Habitat monitoring
• A biologist could equip an endangered animal
  with a collar containing a mote that senses
  position, temperature, etc.
• Military Application To detect truck movement
  in a remote area thousands of motes are
  scattered. When an enemy truck drives through the
  area the commander can track the path that the
  truck is following through the field of motes.

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Continued

• Out of range vibrations in industrial equipment
  to catch manufacturing defects
• Hospital monitoring of patient movements /
  monitoring the elderly while allowing freedom of
  movement
• Cosmetics company monitoring warehouse humidity
• Health and Wellness Monitoring (enter human
  bodies and check for physiological problems).
• Traffic sensors in urban areas

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Continued

• Environmental protection (identification and
  monitoring of pollution).
• Indoor/Outdoor Environmental Monitoring.

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Advantages

• Physical attributes
• Small and lightweight
• Low power consumption
• Ad-hoc networking capabilities
• Networking functions are seamless and automatic
• Multiple networks can be in use simultaneously
• Data transmission capabilities
• On-board data acquisition supports many missions
• Software support for many sensor configurations
• Data can be carried through network to command
  centres
• Ubiquity and redundancy in use
• Multiple motes can be available on every
  device/person
• Motes can be strewn in large numbers

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Ad-hoc network

• All of the motes in the area create a giant,
  amorphous network that can collect data. Data
  funnels through the network and arrives at a
  collection node, which has a powerful radio able
  to transmit a signal many miles.
• Used for monitoring purposes in military ,
  traffic , habitat , environment , power
  consumption.

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Disadvantages

• Low Throughput ( lt 10 Kbps )
• Suited for data monitoring, not real-time audio
• Power Source
• RF communications circuits drain a lot of power
• Need advancement in battery technology
• Size
• Many components -gt difficult to reduce size
• Cost
• Current motes cost between 50 - 100 each
• Intrusive probes
• A number of political, environmental, health and
  privacy related questions

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Current scenario future prospects

• Honeywell International is looking at the motes
  for climate control applications.
• San Jose, Calif.-based Digital Sun is receiving
  orders for wireless sensors that monitor
  irrigation.
• Intel Crossbow has come up with a
  second-generation operating system for the smart
  dust.
• Researches indicate that motes sold in future
  will be smaller , cheaper and are likely to have
  revolutionary power sources.

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Conclusion

• 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 low price as possible.
  Soon we will see Smart Dust being used in varied
  application from all spans of life.

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References

• http//www.careers-india.com
• http//www.wikipedia.com
• http//www.scribd.com
• http//www.berkeley.edu
• http//www.computerworld.com

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• Thank You!