27-04-2011, 11:10 AM
PRESENTED BY:
Sunitha
N Srilaxmi M
[attachment=12913]
Smart Dust
ABSTRACT- Smart dust is tiny electronic devices designed to capture mountains of information about their surroundings while literally floating on air. Nowadays, sensors, computers and communicators are shrinking down to ridiculously small sizes. If all of these are packed into a single tiny device, it can open up new dimensions in the field of communications. The idea behind 'smart dust' is to pack sophisticated sensors, tiny computers nd wireless communicators in to a cubic-millimeter mote to form the basis of integrated, massively distributed sensor networks. They will be light enough to remain suspended in air for hours. As the motes drift on wind, they can monitor the environment for light, sound, temperature, chemical composition and a wide range of other information, and beam that data back to the base station, miles away.
1. INTRODUCTION
The research community searches for the processing platform beyond the personal computer, networks of wireless sensors have quite interesting as a new environment in which to seek research challenges. Many researchers have recently shown that it is possible to integrate sensing, communication and power supply into an inch scale device using off the shelf technology. These have been enabled by the rapid convergence of three technologies: digital circuitary, wireless communication and Micro electro mechanical systems. In each area advances in hardware technology and engineering design have led to the reduction in size, power consumption and cost. This has led to the discovery of smart dust. Smart dust is an emerging technology made up of tiny wireless sensors, can detect everything from light to vibration.
The Smart Dust concept was introduced by Kris Pister and Randy H. katz. Kris Pister, of the University of California at Berkeley, is leading a team whose goal is to create devices no bigger than one-millimeter cubes. The Smart Dust project was begun with the goal of investigating the limits of miniaturization and system integration by demonstrating that a useful and complex system can be built within a cubic millimeter It contains sensors, computing circuits, power supply and communication system enabling it to talk to other motes. Individual sensors of smart dust are often referred to as motes because of their small size. Smart dust can consist of hundreds to thousands of dust motes. Depending on the power source, the dust mote can vary in size from 1 mm3 to as large as a sugar cube. Motes gather data, run computations, communicate using two-way with other motes at distances approaching 1,000 feet.
At present each mote is about 5mm long, but the hope is to eventually have as small as speck of dust. Eventually, these devices will be smart enough to talk with other sensors yet small enough to fit on the head of the pin. Commercially available motes do not yet fit on the head of a pin, some are about the size of a deck of cards and others are as small as a stack of a few quarters. At present each mote is about 5mm long.
Fig 1.1: Dust mote
Motes relies on the convergence of three technologies: digital circuitry, laser-driven wireless communications, and MEMS (Micro Electro Mechanical Systems) to pack enough equipment into a space no more than one or two cubic millimeters in size.
Fig 1.2: Present size of the Smart Dust & Expected size of future Smart Dust
Smart dust motes are typically outfitted with environmental sensors which can monitors things like temperature, humidity, lighting, position, and acceleration.
Dust mote battery life ranges from a few hours to 10 years, depending on the size and capabilities of the device. Future motes will be smaller and have longer battery lives. Already, researchers at the University of California, Berkeley have developed a mote roughly the size of aspirin tablet. For power, future motes could be supplemented by solar cells. The unit becomes a mote once a small sensor board, coin battery, and antenna are added to the product. Many of the sensors available for smart dust motes are micro-electromechanical systems (MEMS). MEMS contain microscopic devices, usually with a moving part, integrated together with some electronic circuitry.
Size reduction is paramount, to make the nodes as inexpensive and easy to deploy as possible. The research team is working to incorporate the requisite sensing, communication and computing hardware along with the power supply, in a volume not more than a cubic millimeter, while still achieving impressive performance in terms of sensor functionality and communication capability.
2. COMPONENTS OF SMART DUST
Smart Dust would have four basic components:
2.1 Energy storage and scavenging
2.2 Computation
2.3 Sensors
2.4 Communication Unit
Fig 2.1 Conceptual diagram of a Smart Dust
The above figure shows a conceptual diagram of a Smart Dust. The volume is expected to be dominated by the energy source, which will be an energy storage element such as a battery or capacitor, an energy harvester, or a combination thereof.
All the components in conceptual diagram are discussed in detail in following pages.
Fig 2.2: Magnified view of the Smart Dust mote. The mote connects to a short antenna for transmitting and receiving radio waves.
2.1 ENERGY STORAGE AND SCAVENGING
In order to monitor an environment for any length of time, the dust particle must have enough energy to survive anywhere from a few hours to months at a time. This requires energy source which will be an energy storage element viz a battery or capacitor. The power system consists of a thick-film battery or a solar cell with a charge-integrating capacitor to allow for charge retention for periods of darkness, or both.
From the system’s perspective, a good micro battery would have the following features:
1. High energy density
2. Large active volume to packaging volume ratio (i.e. a thin film on top of a 500μm silicon wafer would not be desirable)
3. Small cell potential (0.5 - 1.0 V) so digital circuits can take advantage of the quadratic reduction in power consumption with supply voltage
4. Efficiently configured into series batteries to provide a variety of cell potentials for the various components of the system without requiring the overhead of voltage converters
5. Rechargeable in case the system has an energy harvester
Scavenging energy from the environment will allow the wireless sensor nodes to operate nearly indefinitely, without their battery drying. Commonly used energy sources are solar radiation, capacitor etc.
Solar radiation is the most abundant energy source and yields around 1 mW/mm2 (1 J/day/mm2) in full sunlight or 1 μW/mm2 under bright indoor illumination. Solar cells have conversion efficiencies up to 30% and are a well established technology, making them attractive for early use in sensor nodes.
Capacitors may be used in these systems to effectively lower the impedance of a battery or energy harvester to allow larger peak currents or to integrate charge from an energy harvester to compensate for lulls, such as nighttime for a solar cell. Current capacitors store upto 10mJ/mm3.
The optical receiver of smart dust consumes approximately 0.1nJ/bit and the
Transmitter uses 1nJ/bit. The analog-to-digital converter will require 1nJ/sample, and
Computations are anticipated to consume under 1pJ/instruction. Energy consumption must therefore be minimized in every part of the system.
2.2 COMPUTATION
Since the dust particle is expected to communicate securely and process senses data, dust particle must have computational requirements. Microprocessor serves for processing of information obtained by sensors of the mote as well as by communication device. Microprocessor analyses them and define, what to do with them: delete, archive or send a notice. Memory SRAM saves the program for microprocessor and transferred or detected data.
Periodically the microprocessor gets a reading from one of the sensors, which measure one of a number of physical or chemical stimuli such as temperature, ambient light, vibration, acceleration, or air pressure, processes the data, and stores it in memory.
2.3 SENSORS
The next component of the Smart Dust mote is the sensor array. Micromachining has allowed researchers to shrink many types of sensors into small volumes. The interface between the environment and the dust particle is the sensor. The dust particles should have basic environmental sensors which may include temperature, pressure, humidity, light, sound, acceleration, magnetic field.
2.4 COMMUNICATION
Dust particle must have the ability to communicate with one another at ranges from few meters to kilometers. The most important aspect here is secured communication. There are two different types of communication.
Sunitha
N Srilaxmi M
[attachment=12913]
Smart Dust
ABSTRACT- Smart dust is tiny electronic devices designed to capture mountains of information about their surroundings while literally floating on air. Nowadays, sensors, computers and communicators are shrinking down to ridiculously small sizes. If all of these are packed into a single tiny device, it can open up new dimensions in the field of communications. The idea behind 'smart dust' is to pack sophisticated sensors, tiny computers nd wireless communicators in to a cubic-millimeter mote to form the basis of integrated, massively distributed sensor networks. They will be light enough to remain suspended in air for hours. As the motes drift on wind, they can monitor the environment for light, sound, temperature, chemical composition and a wide range of other information, and beam that data back to the base station, miles away.
1. INTRODUCTION
The research community searches for the processing platform beyond the personal computer, networks of wireless sensors have quite interesting as a new environment in which to seek research challenges. Many researchers have recently shown that it is possible to integrate sensing, communication and power supply into an inch scale device using off the shelf technology. These have been enabled by the rapid convergence of three technologies: digital circuitary, wireless communication and Micro electro mechanical systems. In each area advances in hardware technology and engineering design have led to the reduction in size, power consumption and cost. This has led to the discovery of smart dust. Smart dust is an emerging technology made up of tiny wireless sensors, can detect everything from light to vibration.
The Smart Dust concept was introduced by Kris Pister and Randy H. katz. Kris Pister, of the University of California at Berkeley, is leading a team whose goal is to create devices no bigger than one-millimeter cubes. The Smart Dust project was begun with the goal of investigating the limits of miniaturization and system integration by demonstrating that a useful and complex system can be built within a cubic millimeter It contains sensors, computing circuits, power supply and communication system enabling it to talk to other motes. Individual sensors of smart dust are often referred to as motes because of their small size. Smart dust can consist of hundreds to thousands of dust motes. Depending on the power source, the dust mote can vary in size from 1 mm3 to as large as a sugar cube. Motes gather data, run computations, communicate using two-way with other motes at distances approaching 1,000 feet.
At present each mote is about 5mm long, but the hope is to eventually have as small as speck of dust. Eventually, these devices will be smart enough to talk with other sensors yet small enough to fit on the head of the pin. Commercially available motes do not yet fit on the head of a pin, some are about the size of a deck of cards and others are as small as a stack of a few quarters. At present each mote is about 5mm long.
Fig 1.1: Dust mote
Motes relies on the convergence of three technologies: digital circuitry, laser-driven wireless communications, and MEMS (Micro Electro Mechanical Systems) to pack enough equipment into a space no more than one or two cubic millimeters in size.
Fig 1.2: Present size of the Smart Dust & Expected size of future Smart Dust
Smart dust motes are typically outfitted with environmental sensors which can monitors things like temperature, humidity, lighting, position, and acceleration.
Dust mote battery life ranges from a few hours to 10 years, depending on the size and capabilities of the device. Future motes will be smaller and have longer battery lives. Already, researchers at the University of California, Berkeley have developed a mote roughly the size of aspirin tablet. For power, future motes could be supplemented by solar cells. The unit becomes a mote once a small sensor board, coin battery, and antenna are added to the product. Many of the sensors available for smart dust motes are micro-electromechanical systems (MEMS). MEMS contain microscopic devices, usually with a moving part, integrated together with some electronic circuitry.
Size reduction is paramount, to make the nodes as inexpensive and easy to deploy as possible. The research team is working to incorporate the requisite sensing, communication and computing hardware along with the power supply, in a volume not more than a cubic millimeter, while still achieving impressive performance in terms of sensor functionality and communication capability.
2. COMPONENTS OF SMART DUST
Smart Dust would have four basic components:
2.1 Energy storage and scavenging
2.2 Computation
2.3 Sensors
2.4 Communication Unit
Fig 2.1 Conceptual diagram of a Smart Dust
The above figure shows a conceptual diagram of a Smart Dust. The volume is expected to be dominated by the energy source, which will be an energy storage element such as a battery or capacitor, an energy harvester, or a combination thereof.
All the components in conceptual diagram are discussed in detail in following pages.
Fig 2.2: Magnified view of the Smart Dust mote. The mote connects to a short antenna for transmitting and receiving radio waves.
2.1 ENERGY STORAGE AND SCAVENGING
In order to monitor an environment for any length of time, the dust particle must have enough energy to survive anywhere from a few hours to months at a time. This requires energy source which will be an energy storage element viz a battery or capacitor. The power system consists of a thick-film battery or a solar cell with a charge-integrating capacitor to allow for charge retention for periods of darkness, or both.
From the system’s perspective, a good micro battery would have the following features:
1. High energy density
2. Large active volume to packaging volume ratio (i.e. a thin film on top of a 500μm silicon wafer would not be desirable)
3. Small cell potential (0.5 - 1.0 V) so digital circuits can take advantage of the quadratic reduction in power consumption with supply voltage
4. Efficiently configured into series batteries to provide a variety of cell potentials for the various components of the system without requiring the overhead of voltage converters
5. Rechargeable in case the system has an energy harvester
Scavenging energy from the environment will allow the wireless sensor nodes to operate nearly indefinitely, without their battery drying. Commonly used energy sources are solar radiation, capacitor etc.
Solar radiation is the most abundant energy source and yields around 1 mW/mm2 (1 J/day/mm2) in full sunlight or 1 μW/mm2 under bright indoor illumination. Solar cells have conversion efficiencies up to 30% and are a well established technology, making them attractive for early use in sensor nodes.
Capacitors may be used in these systems to effectively lower the impedance of a battery or energy harvester to allow larger peak currents or to integrate charge from an energy harvester to compensate for lulls, such as nighttime for a solar cell. Current capacitors store upto 10mJ/mm3.
The optical receiver of smart dust consumes approximately 0.1nJ/bit and the
Transmitter uses 1nJ/bit. The analog-to-digital converter will require 1nJ/sample, and
Computations are anticipated to consume under 1pJ/instruction. Energy consumption must therefore be minimized in every part of the system.
2.2 COMPUTATION
Since the dust particle is expected to communicate securely and process senses data, dust particle must have computational requirements. Microprocessor serves for processing of information obtained by sensors of the mote as well as by communication device. Microprocessor analyses them and define, what to do with them: delete, archive or send a notice. Memory SRAM saves the program for microprocessor and transferred or detected data.
Periodically the microprocessor gets a reading from one of the sensors, which measure one of a number of physical or chemical stimuli such as temperature, ambient light, vibration, acceleration, or air pressure, processes the data, and stores it in memory.
2.3 SENSORS
The next component of the Smart Dust mote is the sensor array. Micromachining has allowed researchers to shrink many types of sensors into small volumes. The interface between the environment and the dust particle is the sensor. The dust particles should have basic environmental sensors which may include temperature, pressure, humidity, light, sound, acceleration, magnetic field.
2.4 COMMUNICATION
Dust particle must have the ability to communicate with one another at ranges from few meters to kilometers. The most important aspect here is secured communication. There are two different types of communication.
