What is a smart dust?
'Smart dust' — sensor-laden networked computer nodes that are just cubic millimetres in volume. The smart dust project envisions a complete sensor network node, including power supply, processor, sensor and communications mechanisms, in a single cubic millimetre. .Smart dust motes could run for years , given that a cubic millimetre battery can store 1J and could be backed up with a solar cell or vibrational energy source.
The goal of the Smart Dust project is to build a millimeter-scale sensing and communication platform for a massively distributed sensor network. This device will be around the size of a grain of sand and will contain sensors, computational ability, bi-directional wireless communications, and a power supply. Smart dust consists of series of circuit and micro-electro-mechanical systems (MEMS) designs to cast those functions into custom silicon. Microelectromechanical systems (MEMS) consist of extremely tiny mechanical elements, often integrated together with electronic circuitry.
Core Functionality Specification
Choose the case of military base monitoring wherein on the order of a thousand Smart Dust motes are deployed outside a base by a micro air vehicle to monitor vehicle movement. The motes can be used to determine when vehicles were moving, what type of vehicle it was, and possibly how fast it was travelling. The motes may contain sensors for vibration, sound, light, IR, temperature, and magnetization. CCRs will be used for transmission, so communication will only be between a base station and the motes, not between motes. A typical operation for this scenario would be to acquire data, store it for a day or two, then upload the data after being interrogated with a laser. However, to really see what functionality the architecture needed to provide and how much reconfigurability would be necessary, an exhaustive list of the potential activities in this scenario was made.
Listening To A Dust Field
Many Smart Dust applications rely on direct optical communication from an entire field of dust motes to one or more base stations. These base stations must therefore be able to receive a volume of simultaneous optical transmissions. Further, communication must be possible outdoors in bright sunlight which has an intensity of approximately 1 kilowatt per square meter, although the dust motes each transmit information with a few milliwatts of power.
Abstract
Advances in hardware technology have enabled very compact, autonomous and mobile nodes each having one or more sensors, computation and communication capabilities, and a power supply. The Smart Dust project is exploring whether an autonomous sensing, computing, and communication system can be packed into a cubic-millimeter mote to form the basis of integrated, massively distributed sensor networks. It focuses on reduction of power consumption, size and cost.
Passive Reflective Systems
The passive reflective communication is obtained by a special device called CCR (Corner cube retro reflector) consists of three mutually orthogonal mirrors. Light enters the CCR, bounces off each of the three mirrors, and is reflected back parallel to the direction it entered. In the MEMS version, the device has one mirror mounted on a spring at an angle slightly askew from perpendicularity to the other mirrors.
Communicating From A Grain Of Sand
Smart Dust’s full potential can only be attained when the sensor nodes communicate with one another or with a central base station. Wireless communication facilitates simultaneous data collection from thousands of sensors. There are several options for communicating to and from a cubic-millimeter computer. Radio-frequency and optical communications each have their strengths and weaknesses. Radio-frequency communication is well under-stood, but currently requires minimum power levels in the multiple milliwatt range due to analog mixers, filters, and oscillators. If whisker-thin antennas of centimeter length can be accepted as a part of a dust mote, then reasonably efficient antennas can be made for radio-frequency communication. While the smallest complete radios are still on the order of a few hundred cubic millimeters, there is active work in the industry to produce cubic-millimeter radios.
Summary
Smart dust is made up of thousands of sand-grain-sized sensors that can measure ambient light and temperature. The sensors -- each one is called a "mote" -- have wireless communications devices attached to them, and if you put a bunch of them near each other, they'll network themselves automatically. These sensors, which would cost pennies each if mass-produced, could be plastered all over office buildings and homes. Each room in an office building might have a hundred or even a thousand light- and temperature-sensing motes, all of which would tie into a central computer that regulates energy usage in the building.
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