Electronics Spectra - SMS Lucknow

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SMS Institute of Technology, L ucknow Smart dust INTRODUCTION WHAT IS SMART DUST? Smart dust is a tiny dust size device with extra-ordinary capabilities. Smart dust is a hypothetical wireless ne t- work of tiny microelectromechanical sensors (MEMS), robots, or dev ices, that can detect (for example) light, temperature, or vibration which was introduced by Kristopher S.J. Pister. Smart dust combines sensing, c omputing, wireless communication capabilities and autonomous power supply within volume of only few millimeters and that too at a very low cost. These devices are proposed to be so small and light in weight that they can remain suspended in the environm ent 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 sens ors of smart dust are often referred to as motes because of their small size. BACKGROUND The Defense Advanced Research Projects Agency (DARPA) has been funding Smart Dust research heavily since the late 1990s, seeing virtually limitless applicatio ns in the sphere of modern warfare. So far the research has been promising, w ith prototype smart dust sensors as small as 5mm.But further scaling dow n needs advance technological changes. We are well aware that costs h ave been dropping rapidly with technological innovations, bringing indi vidual motes down to as little as $50 each, with hopes of dropping below $1 per mote in the near future. STRUCTURE A smart dust particle is often called motes. Now 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 optic al receiver, a signal processing and control circuitry, and a power source based on thick-film batteries and solar cells. The major challenge is to be faced when all the functions are to be incorporated maintaining very lo w power consumption and optimizi ng the operating life of the mote. Smart dust motes consist of a passive optical transmitter with a micro fabricated Corner- Cube Retro-Reflector (CCR). Now this CCR contains three mutually perpendicular mirror fabricated of gold- coated poly-silicon. The CCR reflects any ray of light within a certain range of angles center ed about the cube diagonally back to the source. 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 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, wind shear, on to the m ote. Active transmitters make possi ble peer-to-peer communication between dust motes, provided the re exists a line-of-sight path be tween them. CORNER CUBE RETRO- REFLECTOR (CCR) Department of Electronics & Co mmunication CCR comprises of three mutually perpendicular mirrors of gold-coated polysilicon. It has the proper ty that any incident ray of light is r eflected back to the source (provided t hat it is incident within a certain r ange of angles centered about the cube ’s body diagonal). If any one of the mirrors is misaligned, this retro-reflection property is spoiled. So the micro-fabricated CCR includes an electr ostatic actuator that can deflect one of the mirrors at kilohertz rates. Si nce the dust mote itself cannot emit light, the passive transmitter consumes l ittle power. Using a micro-fabricated CCR, we can achieve data transmission at a bit rate up to 1 kilobit per s econd, and over a range of up to 150 meters, using a 5 milliwatt illuminating laser. It should note that CCR-based pas- Kislaya Srivastava EC - III year sive 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 b ody diagonal happens to point directly toward the BTS, within a few ten s of degrees. A passive transmitter can be made more Omni-directional by employing several CCRs oriented in different directions, at the expe nse 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. COMMUNICATION TECHNOLOGIES: I. Radio Frequency Transmission II. Optical transmission technique a) Active Laser based Communication b) Fiber Optic Communication I. RADIO FREQUENCY TRANSMISSION It is based on the generation, propagation and detection of electromagnetic waves with a frequenc y range from tens of kHz to hund reds of GHz. It could be used to fu nction 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 techniq ues: time, frequency or code-division multiplexing. Their use leads to modulation, band pass filtering, demodulation circuitry, and additional circuitry, all of which needs to be considered based on power consumption,etc. II. Optical Transmission Technique The Smart Dust can employ a passive laser based communication scheme to establish a bi-direc tional communication link between dus t nodes and a base station transceiver (BST). For downlink communicat ion (BST to dust), the base station points a modulated laser beam at a no de. 24 Electronics Spectra, 2010
SMS Institute of Technology, L ucknow Department of Electronics & Co mmunication The latter uses a simple optic al receiver to decode the incoming message. For uplink communication (dust to BST), the base station poin ts 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 wi th a Corner Cube Retro Reflector (C CR). The CCR has the property that any incident ray of light is reflected back to the source under certain co nditions. If one of the mirrors i s misaligned, this retro reflection property is spoiled. The Smart Dust CCR has an electrostatic actuator that can deflect one of the mirrors at kilohertz rates. Using this actuator, the incident laser beam is “on-off” modulated and reflected back to the BST. A) 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 semicon ductor laser, a collimating lens and a beamsteering micro-mirror as shown in Figure 2. Active optical communic ation 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 netwo rk can be made to be small enough to fit into the smart dust motes. GPS maptor Maptor, the navigational gadge t is the combination of Map and Projector. It is used to project map on any desired surface. Its really portable due to its small size. The mos t discussed advantage of Maptor is that, we don't need any one's help on the way, even if we are lost. GPS Maptor is GPS included with Maptor. We know that GPS is Global Positioning System; it is a US space based Global Navigation Satellite System. It provides reliable positioning, navigation and timing services to worldwide users. Maptor gives the combined effect of two technologies. As a result of the above said combination we can locate our cur rent position on the map with the help of a red arrow that points the location. Another advantage is the map pro- One of the disadvantages of th e active transmitter is its relatively high power consumption. This leads to the use of active optical communic ation for short duration burst-mode communication only. In order to minimize the power consumption, the act ive transmitter should have some protocol to aim the beams toward the receiver, for example, using directional beam and an active beam-steeri ng mechanism. These components would make the design of the d ust mote more complicated. B) Fiber-optic communication Fiber-optical communication em - ploys semiconductor laser, fiber cable and a diode receiver to gener ate, transfer and detect the optical signal. Its most of the characteristics matches with that of passive optical communication. The relatively small size of the optical transceiver is employe d with low-power operation. Each dust mote does not need to have an on bo ard light source to transmit the data. By the using MEMS technology, Cor ner cube retro-reflector is employ ed on each dust mote to modulate upl ink data to base station. APPLICATION OF SMART DUST 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 c ost jection is easily viewable even in day light. This concept is designed by Jin- much so can be densely deploye d. Due to the above-mentioned fea - tures, Smart Dust can be used in varied application fields. These are as follows: 1) Environmental protection (identification and monitoring of pollution). 2) Habitat monitoring (observing the behavior of the animals in the re natural habitat). 3) Military application (monitoring activities in inaccessible areas , accompany soldiers and alert them to any poisons or dangerous biological substances in the air). 4) Indoor/Outdoor Environmental Monitoring 5) Security and Tracking 6) Health and Wellness Monitoring (enter human bodies and check for physiological problems) 7) Power Monitoring 8) Inventory Location Awareness 9) Factory and Process Automation 10) Seismic and Structural Monitoring 11) Monitor traffic and redirecting it. There are many ongoing researches on Smart Dust, the ma in 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. Priyanka Shukla EC - III year Sun Park and Seon-Keun Park to make a new wave in the gadget industry. The GPS Maptor combines GPS facility for maps, locations and directions capsulated in a mini projector. This gadget is really a handy one with its awesome shape. Moreover different projectors are available like Nokia Cellphone projector and Explay Handheld Projector, but still this new design may seem to be good for those who don't require the combination of cellphone and GPS navigation. Actually this device is really a boon to the tourists and for those who love travelling. 25 Electronics Spectra, 2010
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