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Wednesday, April 11

White LED: The Future Lamp : Seminar Report|PPT|PDF|DOC|Presentation|Free Download

LED stands for Light Emitting Diode. An LED is a semiconductor chip that converts electrical energy into light. The conversion of energy into light happens on the quantum level within the molecular makeup of the semiconductor chip. The process begins with the chip acting as a diode with two terminals, a P (Positive hole carrier) and N (Negative electron) region in its basic structure, which allow the chip to conduct in one direction for operation. In addition, there are added chemical layers called epitaxy layers that enhance the ability of the device to emit light (Photons). As electrical energy passes through the P and N regions of the LED, electrons move to higher energy levels called band gap potentials. To meet the conservation of energy law, the electron's excess energy, gained while moving energy levels, will then produce a photon that our eye will perceive as light. At this point, the band gap potentials equal the energy of the photon created when the electron that was moving energy levels comes back to the ground state.

The colour of the light emitted directly relates to the size of the band gap potentials or the amount of energy the photons produce. Since different colours occur at different band gap potentials, or energy levels, this explains why different colour LEDs exhibit different forward voltages to operate. Recent advances in LED technology have led to brighter LEDs due to higher quantum efficiencies and higher chip extraction efficiencies. Another recent development of a blue color LED has led to RGB (Red Green Blue) white lighting as well as Phosphor on Blue to form white LEDs. The technique of Phosphor coating on Blue has shown that in the near future, white lighting from solid-state sources is a possibility, which has led to a lot of excitement.

Bright LEDs For Outdoor Applications
The first LEDs bright enough for use in outdoor applications were made of aluminium-gallium arsenide (AlGaAs). These red LEDs appeared as high mount-stop lights on automobiles and in a limited number of traffic lights. The recent advent of efficient green, blue and white LEDs may lead to more applications. Aluminium-gallium-indium phosphide (AlGaInP) and indium-gallium-nitride (InGaN) LEDs have succeeded AlGaAs as the brightest available LEDs. AlGaInP LEDs range in color from red to amber and produce about 3 lumens with efficacies greater than 20 lumens per electrical watt, although green and yellow AlGaInP LEDs have much lower efficacies. Hewlett-Packard plans to release AlGaInP LEDs with a light output of more than 10 lumens per LED.

Guided Missiles

Presently there are many types of guided missiles. They can be broadly classified on the basis of their features such as type of target, method of launching, range, launch platform, propulsion or guidance and tye of trajectory.On the basis of target they are classified as Antitank/ Antiarmour, Antipersonnel, Antiaircraft, Antiship/ Antisubmarine, Antisatallites or Antimissiles.Another classification of missiles which depends upon the method of launching. They are surface- to- surface Missiles [ SSM], Surface-to-Air Missiles [SAM], Air -to-Air Missiles [AAM] and Air- to- Surface Missiles.

Surface- to - Surface Missiles are common Ground-to-Ground ones. Although these may be launched from a ship to another ship. Under water weapons, which are launched from a submarine, also come under this classification.Surface-to-Air Missiles ar3 essential complaint of modern air defence systems along with Antiaircraft guns which are used against hostile aircrafts. Air-to-air Missiles are for air born battle among fighter or bomber aircraft. These are usually mounted under the wings of the aircraft and are fired against the target. The computer and radar networks control these missiles.
On the basis of range, missiles can be broadly classified as short range missiles, medium range missiles, intermediate range missiles and long range missiles. These classifications is mainly used in the care of SSM missiles which travel a distance of about a distance of about 50 to 100 km. Are designated as short range missiles. Those with a range of 100 to 1500 km. Are called medium range missiles and missiles having a range up to 5000 km. Are said to be intermediate- range missiles. Missiles, which travel a distance of 12000 km, are called long-range missiles.On the basis of launch platform missiles can be termed as shoulder fired, Land/ Mobile fired, Aircraft/ Helicopter borne, Ship/ submarine- launched.

Based on guidance, missiles are broadly classified as command guider missiles, Homing guidance, Beam rider guidance, inertial navigation guidance and stellar guidance.One more classification is based on the type of trajectory and a missile is called as a ballistic missile or a cruise missile. By definition ballistic missile is the one, which covered a major part of its range outside the atmosphere where the only external force active on the missile is the gravitational force of earth, while the cruise is the one, which travels its entire range within the atmosphere at aim nearly constant height and speed.Another classification based on the propulsion system provided in the missile. So they are classified solid propulsion systems, liquid propulsion systems and hybrid propulsion systems.

SyncML

The popularity of mobile computing and communications devices can be traced to their ability to deliver information to users when needed. Users want ubiquitous access to information and applications from the device at hand, plus they want to access and update this information on the fly. The ability to use applications and information on one mobile device, then to synchronize any updates with the applications and information back at the office, or on the network, is key to the utility and popularity of this pervasive, disconnected way of computing.

Unfortunately, we cannot achieve these dual visions: Networked data that support synchronization with any mobile device Mobile devices that support synchronization with any networked data Rather, there is a proliferation of different, proprietary data synchronization protocols for mobile devices. Each of these protocols is only available for selected transports, implemented on a selected subset of devices, and able to access a small set of net-worked data.

The absence of a single synchronization standard poses many problems for end users, device manufacturers, application developers, and service providers. SyncML is a new industry initiative to develop and promote a single, common data synchronization protocol that can be used industry-wide. Driving the initiative are Ericsson, IBM, Lotus, Motorola, Nokia, Palm Inc., Psion, Starfish Software. Additional companies are being recruited to join and participate. Founded in February 2000, the SyncML initiative recognized the worldwide need for one common data synchronization protocol.
With the industry-wide proliferation of mobile devices and the evolution toward mobile devices as the major means of information exchange, remote synchronization of data will be of integral importance. The SyncML initiative, officially supported by well over 200 device manufacturers, service providers and application developers, is currently developing and promoting an open global specification for mobile data synchronization.

The popularity of mobile computing and communication devices can be traced to their ability to deliver information to users when needed. Users want ubiquitous access to information and applications from the device at hand, plus they want to access and update this information on the fly.A long-standing obstacle to the advancement of ubiquitous computing has been the lack of a generalized synchronization protocol. Until recently, the available synchronization protocols were proprietary, vendor-specific, and supported synchronization only on selected transports, implemented on a selected subset of devices, and able to access a small set of net-worked data. This has slowed development in the area of mobile computing and been a common source of frustration for users, device manufacturers, service providers, and application developers.

SyncML is a new industry initiative to develop and promote a single, common data synchronization protocol that can be used industry-wide. Driving the initiative are Ericsson, IBM, Lotus, Motorola, Nokia, among others. SyncML is intended as a common language that enables smooth, efficient synchronization of personal and business information over fixed or mobile networks. Its aim is to facilitate the synchronization of networked information with various devices running SyncML-compatible applications.

EDGE

About :- : -

Mobile users continue to demand higher data rates. With the continued growth in cellular services, laptop computer use and the Internet, wireless network providers are beginning to pay an increasing amount of attention to packet data networks. Enhanced Global Packet Radio Service (EGPRS) offers a substantial improvement in performance and capacity over existing GPRS services, in return for a relatively minimal additional investment. EGPRS, commonly called EDGE, achieves these enhancements to the GPRS system primarily by implementing changes to the Physical layer and to the Medium Access Control/Radio Link Control (MAC/RLC) layer. The significant improvements are a new modulation technique, additional modulation coding schemes, a combined Link Adaptation and Incremental Redundancy technique, re-segmentation of erroneously received packets, and a larger transmission window size.

Technical Differences Between GPRS And EGPRS

Introduction

Regarded as a subsystem within the GSM standard, GPRS has introduced packet-switched data into GSM networks. Many new protocols and new nodes have been introduced to make this possible.

EDGE is a method to increase the data rates on the radio link for GSM. Basically, EDGE only introduces a new modulation technique and new channel coding that can be used to transmit both packet-switched and circuit-switched voice and data services. EDGE is therefore an add-on to GPRS and cannot work alone. GPRS has a greater impact on the GSM system than EDGE has. By adding the new modulation and coding to GPRS and by making adjustments to the radio link protocols, EGPRS offers significantly higher throughput and capacity.

Measurement Accuracy

As in the GSM environment, GPRS measures the radio environment by analyzing the channel for carrier strength, bit error rate, etc. Performing these measurements takes time for a mobile station, which is of no concern in the speech world as the same coding is used all the time. In a packet-switched environment, it is essential to analyze the radio link quickly in order to adapt the coding toward the new environment. The channel analysis procedure that is used for GPRS makes the selection of the right coding scheme difficult since measurements for interference are performed only during idle bursts. As a result, measurements can only be performed twice during a 240-millisecond period.

For EGPRS, the standard does not rely on the same "slow" measurement mechanism. Measurements are taken on each and every burst within the equalizer of the terminal, resulting in an estimate of the bit error probability (BEP). Estimated for every burst, the BEP is a reflection of the current C/I, the time dispersion of the signal and the velocity of the terminal. The variation of the BEP value over several bursts will also provide additional information regarding velocity and frequency hopping. A very accurate estimation of the BEP is then possible to achieve.

Coding Schemes

For GPRS, four different coding schemes, designated CS1 through CS4, are defined. Each has different amounts of error-correcting coding that is optimized for different radio environments. For EGPRS, nine modulation coding schemes, designated MCS1 through MCS9, are introduced. These fulfill the same task as the GPRS coding schemes. The lower four EGPRS coding schemes (MSC1 to MSC4) use GMSK, whereas the upper five MSC5 to MSC9) use 8PSK modulation. Figure shows both GPRS and EGPRS coding schemes, along with their maximum throughputs.

EDGE Standard And References

The EDGE base station system work item provides a platform to employ new modulation techniques, whereas the EDGE network support subsystem work item defines the network changes to facilitate the physical layer. According to the work item descriptions, EDGE will provide two phases: Phase 1: Single- and multislot packet-switched services and single and multislot circuit switched services Phase 2: Real-time services employing the new modulation techniques that are not included in Phase 1.

Phase 1 has been completed with 3GPP Release 99. Phase 2 is ongoing in the 3GPP standardization, and its scope has been extended to cover the alignment with WCDMA and the provisioning of Internet protocol (IP) multimedia. This concept, currently standardized in 3GPP, is known as GERAN.

Conclusion

This paper has presented an overview of EDGE with particular focus on the physical layer and the data link layer. The goal of EDGE is to provide a packet data network that provides operating rates that are of adequate speed for most applications. EDGE achieves this increase in throughput rate mainly through enhancements to the physical layer and the RLC/MAC layer of the GPRS system.

D-Blast

The explosive growth of both the wireless industry and the Internet is creating a huge market opportunity for wireless data access. Limited Internet access, at very low speeds, is already available as an enhancement to some existing cellular systems. However those systems were designed with purpose of providing voice services and at most short messaging, but not fast data transfer. Traditional wireless technologies are not very well suited to meet the demanding requirements of providing very high data rates with the ubiquity, mobility and portability characteristics of cellular systems. Increased use of antenna arrays appears to be the only means of enabling the type of data rates and capacities needed for wireless Internet and multimedia services.

While the deployment of base station arrays is becoming universal it is really the simultaneous deployment of base station and terminal arrays that can unleash unprecedented levels of performance by opening up multiple spatial signaling dimensions. Theoretically, user data rates as high as 2 Mb/sec will be supported in certain environments, although recent studies have shown that approaching those might only be feasible under extremely favorable conditions-in the vicinity of the base station and with no other users competing for band width. Some fundamental barriers related to the nature of radio channel as well as to the limited bandwidth availability at the frequencies of interest stand in the way of high data rates and low cost associated with wide access.

In wireless systems, radio waves do not propagate simply from transmit antenna to receive antenna, but bounce and scatter randomly off objects in environment. This scattering is known as multipath as it result in multiple copies of the transmitted signals arriving at the receiver via different scattered paths. Multipath has always been regarded as impairment, because the images arrive at the receiver at slightly different times and thus can interfere destructively, canceling each other out.

However recent advances in information theory have shown that, with simulations use of antenna arrays at both base station and terminal, multipath interference can be not only mitigated, but actually exploited to establish multiple parallel channels that operate simultaneously and in the same frequency band. Based on this fundamental idea, a class of layered space-time architecture was proposed and labeled BLAST. Using BLAST the scattering characteristics of the propagation environment is used to enhance the transmission accuracy by treating the multiplicity of the propagation environment is used to enhance the transmission accuracy by treating the multiplicity of scattering paths as separate parallel sub channels.

AC Performance Of Nanoelectronics

Abstract

The phenomenological predictions for the cutoff frequency of carbon nanotube transistors and the predictions of the effects of parasitic capacitances on AC nanotube transistor performance are presented. The influence of quantum capacitance, kinetic inductance, and ballistic transport on the high-frequency properties of nanotube transistors is analyzed. The challenges of impedance matching for ac nano-electronics in general, and how integrated nanosystems can solve this challenge, are presented.

Nanotube Interconnects Quantum Impedances

The first step towards understanding the high frequency electronic properties of carbon nanotubes is to understand the passive ac impedance of a Id quantum system. In the presence of a ground plane below the nanotube or top gate above the nanotube, there is electrostatic capacitance between the nano tube and the metal. Due to quantum properties of Id systems there are two additional components to the ac impedance: the quantum capacitance and the kinetic inductance.

Transconductance

The transconductance is the most critical parameter the underlying mechanism is the least understood. Transconductances upto 20µS have been measured using aqueous gate geometry. A transconductance of 60 µS was recently predicted by simulation.

AC Performance Of Nanoelectronics Seminar Doc

Effects Of Ballistic Transport In Mosfet's

If carrier transport in a device can be assumed to be completely ballistic, analysis of MOSFET current voltage characteristics reduces to carrier transmission over the channel potential barrier. As shown in figure , the potential energy distribution in the channel of the transistor has a maximum, Emax, near the source end of the device. Carriers with a higher energy than Emax can be transmitted over the barrier through the process of thermionic emission. Carriers with lower energies can travel from source to drain only by tunneling quantum mechanically through the channel potential barrier. Such transport phenomena is markedly different from that generally associated with mobility-limited diffusive transport. As a result, the current-voltage characteristics of MOSFET's operating in the ballistic regime will be different.

Parasitic Capacitance

The parasitic capacitance is due to fringing electric fields between the electrodes for the source, drain and gate. While these parasitic capacitance are generally small, they may comparable to the intrinsic device capacitances and hence must be considered. In order to estimate the order of magnitude of the parasitic capacitance, we can use known calculations for the capacitance between two thin metal films, spaced by a distance w, as drawn in Fig. For this geometry, if w is l^im, the capacitance is ~ 10A-16 F/lm of electrode length . For a length of l µm, this gives rise to ~10A-16 F. Thus, typical parasitic capacitances are of the same order of magnitude as typical intrinsic capacitances.

Beyond Microelectronics

Nanoelectronics is not simply a smaller version of microelectronics; things change at the nanoscale. At the device level, silicon transistors may give way to new materials such as organi molecules or inorganic nanowires. At the interconnect level, microelectronics uses long, fat wires, but nanoelectronics seeks to use short nanowires. Finally, fundamentally new architectures will be needed to make use of simple, locally connected structures that are imperfect and are comprised of devices whose performance varies widely. I have argued in this paper that 21st century silicon technology is rapidly evolving into a true nanotechnology. Critical dimensions are already below 100 nm. The materials used in these silicon devices have properties that differ from the bulk. Nanoscale silicon transistors have higher leakage, lower-drive current, and exhibit more variability from device to device. New circuits and architectures will need to be developed to accommodate such devices. It matters little whether the material is silicon or something else, the same issues face any nanoelectronics technology. It's likely that many of the advances and breakthroughs at the circuits and systems levels that will be needed to make nanoelectronics successful will come from the silicon design community. One reason, of course, is that 20 years is not a long time to develop fundamentally new technologies, so that we need to start now, but there are other reasons. The most compelling practical reason is that the fabrication and assembly processes and the materials, device, circuit, and system understanding that we develop by examining radically new technologies are almost certain to be useful in silicon nanotechnology.

Conclusion

The phenomenological predictions for the ac performance of nanotube Transistors were presented. It was predicted that carbon nanotube transistors may be faster than conventional semiconductor technologies. There are many Challenges that must be overcome to meet this goal, which can be best be achieved by the integration of Nanosystems.

Optical Burst Switching

Optical burst switching is a promising solution for all optical WDM networks It combines the benefits of optical packet switching and wavelength routing while taking into account the limitations of current all optical technology In OBS the user data is collected at the edge of the network, sorted based on destination address,and grouped into variable sized bursts Prior to transmitting a burst, a control packet is created and immediately send toward the destination in order to setup a buffer less optical path for its corresponding burst After an offset delay time, the data burst itself is transmitted without waiting for positive acknowledgement from the destination node the OBS framework has been widely studied in the past few years because it achieves high traffic throughput and high resource utilization .

Optical communication has been used for a long time and it very much popular with the invention of wavelength-division multiplexing(WDM) Current WDM works over point-to-point links,where optical-to-electrical-to-optical(OEO) conversion is required over each step The elimination of OEO conversion in all optical networks(AON) allows for unprecedented transmission rates AON's can further be categorized as wavelength-routed networks(WRNs).,optical burst switched networks(OBSNs),or optical packet switched networks(OPSNs).Now we discuss here about optical burst switching(OBS)

In optical burst switching(OBS) data is transported in variable sized units called bursts Due to the great variability in the duration of bursts the OBS network can be viewed as lying between OPSNs and WRNS That is, when all burst durations are very short,equal to the duration of an optical packet,OBSN can be seen as resembling an OPSN On the other hand,when all the burst durations are extremely long the OBSN may seem resembling a WRN In OBS there is strong separation between the data and control planes,which allows for greater network manageability and flexibility In addition its dynamic nature leads to high network adaptability and scalability,which makes it quite suitable for transmission of bursty traffic .

3G Vs WiFi

The two most important phenomena impacting telecommunications over the past decade have been explosive parallel growth of both the internet and mobile telephone services. The internet brought the benefits of data communications to the masses with email, the web, and ecommerce; while mobile service has enabled "follow-me anywhere/always on" telephony. The internet helped accelerate the trend from voice-centric to data-centric networking. Data already exceeds voice traffic and the data share continues to grow. Now these two worlds are converging. This convergence offers the benefits of new interactive multimedia services coupled to the flexibility and mobility of wireless. To realize the full potential of this convergence, however, we need broadband access connections.

Here we compare and contrast two technologies that are likely to play important roles: Third Generation mobile ("3G") and Wireless Local Area Networks ("WLAN") . The former represents a natural evolution and extension of the business models of existing mobile providers. In contrast, the WiFi approach would leverage the large installed base of WLAN infrastructure already in place. We use 3G and WiFi as shorthand for the broad classes of related technologies that have two quiet distinct industry origins and histories.

Speaking broadly, 3G offers a vertically -integrated , top -down , service - provider approach to delivering wireless internet access , while WiFi offers an end -user -centric , decentralized approach to service provisioning. We use these two technologies to focus our speculations on the potential tensions between these two alternative world views. The wireless future will include a mix of heterogenous wireless access technologies. Moreover, we expect that the two world views will converge such that vertically-integrated service providers will integrate WiFi or other WLAN technologies into their 3G or wire line infrastructure when this make sense. The multiplicity of potential wireless access technologies and /or business models provided some hope that we may be able to realize robust facilities - based competition for broadband local access services. If this occurs, it would help solve the "last mile" competition problem that has been deviled telecommunication policy.

Stereoscopic Imaging

A stereoscopic motion or still picture in which the right component of a composite image usually red in color is superposed on the left component in a contrasting color to produce a three-dimensional effect when viewed through correspondingly colored filters in the form of spectacles. The modes of 3D presentation you are most familiar with are the paper glasses with red and blue lenses. The technology behind 3D, or stereoscopic, movies is actually pretty simple. They simply recreate the way humans see normally.

Since your eyes are about two inches apart, they see the same picture from slightly different angles. Your brain then correlates these two images in order to gauge distance. This is called binocular vision - ViewMasters™ and binoculars mimic this process by presenting each eye with a slightly different image. Now you're learning! Need to know more about how do 3D glasses work? Read on. The binocular vision system relies on the fact that our two eyes are spaced about 2 inches (5 centimeters) apart. Therefore, each eye sees the world from a slightly different perspective, and the binocular vision system in your brain uses the difference to calculate distance. Your brain has the ability to correlate the images it sees in its two eyes even though they are slightly different. If you've ever used a ViewMaster™ or a stereoscopic viewer, you have seen yourbinocular vision system in action. In a View-Master, each eye is presented with an image. Two cameras photograph the same image from slightly different positions to create these images. Your eyes can correlate these images automatically because each eye sees only one of the images.

A 3D film viewed without glasses is a very strange sight and may appear to be out of focus, fuzzy or out of register. The same scene is projected simultaneously from two different angles in two different colors, red and cyan (or blue or green). Here's where those cool glasses come in -- the colored filters separate the two different images so each image only enters one eye. Your brain puts the two pictures back together and now you're dodging a flying meteor!
3D glasses make the movie or television show you're watching look like a 3-D scene that's happening right in front of you. With objects flying off the screen and careening in your direction, and creepy characters reaching out to grab you, wearing 3-D glasses makes you feel like you're a part of the action - not just someone sitting there watching a movie. Considering they have such high entertainment value, you'll be surprised at how amazingly simple 3-D glasses are.