TOUCH SCREEN

First computers became more visual, then they took a step further to understand vocal commands and now they have gone a step further and became ‘TOUCHY’, that is skin to screen.

A touchscreen is an easy to use input device that allows users to control PC software and DVD video by touching the display screen. A touch system consists of a touch Sensor that receives the touch input, a Controller, and a Driver. The most commonly used touch technologies are the Capacitive & Resistive systems. The other technologies used in this field are Infrared technology, Near Field Imaging & SAW (surface acoustic wave technology). These technologies are latest in this field but are very much expensive.

The uses of touch systems as Graphical User Interface (GUI) devices for computers continues to grow popularity. Touch systems are used for many applications such as ATM’s, point-of–sale systems, industrial controls, casinos & public kiosks etc. Touch system is basically an alternative for a mouse or keyboard.

The market for touch system is going to be around $2.5 billion by 2004. Various companies involved in development of touch systems mainly are Philips, Samsung etc. Even touch screen mobile phones have been developed by Philips.

INTRODUCTION

A touchscreen is an easy to use input device that  allows users to control PC software and DVD video by touching the display screen. We manufacture and distribute a variety of touch screen related products.

A touch system consists of a touch

Sensor that receives the touch input, a Controller, and a Driver. The touch screen sensor is a clear panel that is designed to fit over a PC. When a screen is touched, the sensor detects the voltage change and passes the signal to the touch screen controller. The controller that reads & translates the sensor input into a conventional bus protocol (Serial, USB) and a software driver which converts the bus information to cursor action as well as providing systems utilities.

As the touch sensor resides between the user and the display while receiving frequent physical input from the user vacuum deposited transparent conductors serve as primary sensing element. Vacuum coated layers can account for a significant fraction of touch system cost. Cost & application parameters are chief criteria for determining the appropriate type determining the system selection. Primarily, the touch system integrator must determine with what implement the user will touch the sensor with & what price the application will support.

Applications requiring activation by a

gloved finger or arbitrary stylus such as a plastic pen will specify either a low cost resistive based sensor or a higher cost infra-red (IR) or surface acoustic wave (SAW) system. Applications anticipating bare finger input or amenable to a tethered pen comprises of the durable & fast capacitive touch systems. A higher price tag generally leads to increased durability better optical performance & larger price.

The most commonly used systems are

generally the capacitive & resistive systems. The other technologies used in this field are Infrared technology & SAW (surface acoustic wave technology) these technologies are latest in this field but are very much expensive.

1. Introduction

To avoid shoot-though in voltage source inverters (VSI), dead-time, a small interval during which both the upper and lower switches in a phase-leg are off, is introduced into the standard pulse width modulation (PWM) control of VSIs. How­ever, such a blanking time can cause problems such as output waveform distortion and fundamental voltage loss in VSIs, es­pecially when the output voltage is low.

To overcome dead-time effects, most solutions focus on dead-time compensation  by introducing complicated PWM compensators and expensive current detection hardware. In practice, the dead-time varies with the gate drive path propa­gation delay, device characteristics and output current, as well as temperature, which makes the compensation less effective, especially at low output current, low frequency, and zero current crossing. Several switching strategies for PWM power converters have been proposed to minimize the dead-time effect. A dead-time minimization algorithm was also discussed earlier to improve the inverter output performance. A phase-leg configu­ration topology proposed prevented shoot through. However, an additional diode in series in the phase-leg increases complexity and causes more loss in the inverter. Also, this phase-leg configuration is not suitable for high-power inverters because the upper device gate turn-off voltage is reversely clamped by a diode turn on voltage. Such a low voltage, usually less than 2 V, is not enough to ensure that a device is in its off-state during the activation of its complement device.

High-power inverters usually need longer dead-time than those low-power counterparts. Also due to complicated struc­tures and severe parasitic parameter variations, in practice, the dead-time for high-power inverters requires specific adjustment and/or compensation, and usually this process is time-con­suming. For general applications, automatically eliminating dead-time by gate drive technology is a desired and complete solution. Gate drives with intelligent functions are in high demand due to the emerging technology of power electronics building blocks (PEBB) and intelligent power modules (IPM) because smart functions can improve power devices’ modu­larity, flexibility and reliability.

In this work, an effective dead-time elimination method is proposed. This method is based on decomposing of a generic phase-leg into two basic switching cells, which are configured with a controllable switch in series with an uncontrollable diode. Therefore, dead-time is not needed. In this paper, the effect of dead-time in VSIs will be first introduced. The prin­ciple of the proposed method to eliminate dead-time effect is explained in detail. Simulation and experimental results are provided to demonstrate the validity and features of the proposed novel method. Flexible implementation methods are also discussed.

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DSTATCOM-Distribution SATATic COMpensator

INTRODUCTION

Shunt Connected Controllers at distribution and transmission levels usually fall under two catogories – Static Synchronous Generators (SSG) and Static VAr Compensators (SVC).

A Static Synchronous Generator (SSG) is defined by IEEE as a self-commutated switching power converter supplied from from an appropriate electric energy source and operated to produce a set of adjustable multiphase voltages , which may be coupled to an ac power system for the purpose of exchanging independently controllable real and reactive power. When the active energy source (usually battery bank, Superconducting Magnetic Energy Storage etc) is dispensed with and replaced by a DC Capacitor which can not absorb or deliver real power except for short durations the SVG becomes a Static Synchronous Compensator (STATCOM) . STATCOM has no long term energy support in the DC Side and can not exchange real power with the ac system ; however it can exchange reactive power. Also , in principle, it can exchange harmonic power too. But when a STATCOM is designed to handle reactive power and harmonic currents together it gets a new name – Shunt Active Power Filter. So a STATCOM handles only fundamental reactive power exchange with the ac system.

STATCOMs are employed at distribution and transmission levels – though for different purposes. When a STATCOM is employed at the distribution level or at the load end for power factor improvement and voltage regulation alone it is called DSTATCOM. When it is used to do harmonic filtering in addition or exclusively it is called Active Power Filter. In the transmission system STATCOMs handle only fundamental reactive power and provide voltage support to buses. In addition STATCOMs in transmission system are also used to modulate bus voltages duting transient and dynamic disturbances in order to improve transient stability margins and to damp dynamic oscillations.

IEEE defines the second kind of Shunt Connected Controller called Static VAr Compensator (SVC) as a shunt connected static var generator or absorber whose output is adjusted to exchange capacitive or inductive current so as to maintain or control specific parameters of the electrical power system (typically bus voltage).Thyristor-switched or thyristor-controlled capacitors/inductors and combinations of such equipment with fixed capacitors and inductors come under this.This has been covered in an earlier lecture and this lecture focusses on STACOMs at distribution and transmission levels.

PWM Voltage Source Inverter based Static VAr Compensators (referred to as SVC here onwards) began to be considered a viable alternative to the existing passive shunt compensators and Thyristor Controlled Reactor (TCR ) based compensators from mid-eighties onwards. The disadvantages of capacitor/inductor compensation are well known. TCRs could overcome many of the disadvantages of passive compensators. However they suffered from two major disadvantages ;namely slow response to a VAr command and injection of considerable amount of harmonic currents into the power system which had to be cancelled by special transformers and filtered by heavy passive filters.

It became clear in the early eighties that apart from the mundane job of pumping lagging/leading VArs into the power system at chosen points ,VAr generators can assist in enhancing stability of the power system during large signal and small signal disturbances if only they were faster in the time domain. Also ,they can provide reactive support against a fluctuating load to maintain the bus voltage regulation and to reduce flicker problems,provide reactive support to control bus voltages against sag and swell conditions and provide reactive support to correct the voltage unbalance in the source – if only they were fast enough. PWM STATCOMs covered in this lecture are capable of delivering lagging/leading VArs to a load or to a bus in the power system in a rapidly controlled manner.

High Power STATCOMs of this type essentially consist of a three phase PWM Inverter using GTOs,Thyristors or IGBTs, a D.C. side capacitor which provides the D.C. voltage required by the inverter,filter components to filter out the high frequency components of inverter output voltage,a link inductor which links the inverter output to the a.c supply side,interface magnetics (if required) and the related control blocks. The Inverter generates a three-phase voltage, which is synchronized with the a.c supply ,from the D.C. side capacitor and the link inductance links up this voltage to the a.c source. The current drawn by the Inverter from the a.c supply is controlled to be mainly reactive(leading or lagging as per requirement) with a small active component needed to supply the losses in the Inverter and Link Inductor (and in the magnetics,if any).The D.C. side capacitor voltage is maintained constant( or allowed to vary with a definite relationship maintained between its value and the reactive power to be delivered by the Inverter) by controlling this small active current component. The currents are controlled indirectly by controlling the phase angle of Inverter output Voltage with respect to the a.c side source voltage in the “Synchronous Link Based Control Scheme” whereas they are controlled directly by current feedback in the case of “Current Controlled Scheme”.In the latter case the Inverter will be a Current Regulated one ,i.e. its switches are controlled in such a way that the Inverter delivers a commanded current at its output rather than a commanded voltage (the voltage required to see that the commanded current flows out of Inverter will automatically be synthesized by the Inverter).Current Control Scheme results in a very fast STATCOM which can adjust its reactive output within tens of microseconds of a sudden change in the reactive demand.

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ABSTRACT

Real-time systems play a considerable role in our society, and they cover a spectrum from the very simple to the very complex. Examples of current real-time systems include the control of domestic appliances like washing machines and televisions, the control of automobile engines, telecommunication switching systems, military command and control systems, industrial process control, flight control systems, and space shuttle and aircraft avionics.

All of these involve gathering data from the environment, processing of gathered data, and providing timely response. A concept of time is the distinguishing issue between real-time and non-real-time systems. When a usual design goal for non-real-time systems is to maximize system’s throughput, the goal for real-time system design is to guarantee, that all tasks are processed within a given time. The taxonomy of time introduces special aspects for real-time system research. Real-time operating systems are an integral part of real-time systems. Future systems will be much larger, more widely distributed, and will be expected to perform a constantly changing set of duties in dynamic environments. This also sets more requirements for future real-time operating systems. This seminar has the humble aim to convey the main ideas on Real Time System and Real Time Operating System design and implementation.

INTRODUCTION

Timeliness is the single most important aspect of a real -time system. These systems respond to a series of external inputs, which arrive in an unpredictable fashion. The real-time systems process these inputs, take appropriate decisions and also generate output necessary to control the peripherals connected to them. As defined by Donald Gillies “A real-time system is one in which the correctness of the computations not only depends upon the logical correctness of the computation but also upon the time in which the result is produced. If the timing constraints are not met, system failure is said to have occurred.”

It is essential that the timing constraints of the system are guaranteed to be met. Guaranteeing timing behavior requires that the system be predictable. The design of a real -time system must specify the timing requirements of the system and ensure that the system performance is both correct and timely. There are three types of time constraints:

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ABSTRACT

Sensitive skin is a large-area, flexible array of sensors with data processing capabilities, which can be used to cover the entire surface of a machine or even a part of a human body. Depending on the skin electronics, it endows its carrier with an ability to sense its surroundings via the skin’s proximity, touch, pressure, temperature, chemical/biological, or other sensors. Sensitive skin devices will make possible the use of unsupervised machines operating in unstructured, unpredictable surroundings among people, among many obstacles, outdoors on a crowded street, undersea, or on faraway planets. Sensitive skin will make machines “cautious” and thus friendly to their environment. This will allow us to build machine helpers for the disabled and elderly, bring sensing to human prosthetics, and widen the scale of machines’ use in service industry. With their ability to produce and process massive data flow, sensitive skin devices will make yet another advance in the information revolution. This paper surveys the state of the art and research issues that need to be resolved in order to make sensitive skin a reality.

INTRODUCTION

This seminar focuses on the principles, methodology, and prototypes of sensitive skin-like devices, and the related system intelligence and software that are necessary to make those devices work. Sensitive skin represents a new paradigm in sensing and control. These devices will open doors to a whole class of novel enabling technologies, with a potentially very wide impact. Far-reaching applications not feasible today will be realized, ranging from medicine and biology to the machine industry and defense. They will allow us to fulfill our dream for machines sensitive to their surroundings and operating in unstructured environment.

Some applications that sensitive skin devices will make possible are yet hard to foresee. Flexible semiconductor films and flexible metal interconnects that will result from this work will allow us to develop new inexpensive consumer electronics products, new types of displays, printers, new ways to store and share information (like electronic paper and “upgradeable” books and maps). New device concepts suitable for large area flexible semiconductor films will lead to new sensors that will find applications in space exploration and defense, specifically in mine detection and active camouflage..

An ability of parallel processing of massive amounts of data from millions of sensors will find applications in environmental control and power industry. These areas will be further developed because of the highly interdisciplinary nature of the work on sensitive skin, which lies at the intersection of information technology, mechanical engineering, material science, biotechnology, and micro- and nano electronics. Availability of sensitive skin hardware is likely to spur theoretical and experimental work in many other disciplines that are far removed from robotics.

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ABSTRACT

Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By ‘shining’ sound to one location, specific listeners can be targeted with sound without others nearby hearing it. It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any conventional loud speaker. This acoustic device comprises a speaker that fires inaudible ultrasound pulses with very small wavelength which act in a manner very similar to that of a narrow column. The ultra sound beam acts as an airborne speaker and as the beam moves through the air gradual distortion takes place in a predictable way due to the property of non-linearity of air. This gives rise to audible components that can be accurately predicted and precisely controlled. Joseph Pompei’s Holosonic Research Labs invented the Audio Spotlight that is made of a sound processor, an amplifier and the transducer. The American Technology Corporation developed the Hyper Sonic Sound-based Directed Audio Sound System. Both use ultrasound based solutions to beam sound into a focused beam. Audio spotlight can be either directed at a particular listener or to a point where it is reflected.

The targeted or directed audio technology is going to a huge commercial market in entertainment and consumer electronics and technology developers are scrambling to tap in to the market. Being the most recent and dramatic change in the way we perceive sound since the invention of coil loud speaker, audio spot light technology can do many miracles in various fields like Private messaging system, Home theatre audio system, Navy and military applications, museum displays, ventriloquist systems etc. Thus audio spotlighting helps us to control where sound comes from and where it goes!

INTRODUCTION

JUST WHAT IS AUDIO SPOTLIGHTING?

Audio spot lighting is a very recent technology that creates focused beams of sound similar to light beams coming out of a flashlight. By ‘shining’ sound to one location, specific listeners can be targeted with sound without others nearby hearing it, ie to focus sound into a coherent and highly directional beam. It uses a combination of non-linear acoustics and some fancy mathematics. But it is real and is fine to knock the socks of any conventional loud speaker.

The Audio Spotlight & Hyper Sonic Sound Technology (developed by American Technology Corporation), uses ultrasonic energy to create extremely narrow beams of sound that behave like beams of light. Audio spotlighting exploits the property of non-linearity of air. When inaudible ultrasound pulses are fired into the air, it spontaneously converts the inaudible ultrasound into audible sound tones, hence proved that as with water, sound propagation in air is just as non-linear, and can be calculated mathematically. A device known as a parametric array employs the non-linearity of the air to create audible by-products from inaudible ultrasound, resulting in an extremely directive, beamlike wide-band acoustical source. This source can be projected about an area much like a spotlight, and creates an actual specialized sound distant from the transducer. The ultrasound column acts as an airborne speaker, and as the beam moves through the air, gradual distortion takes place in a predictable way. This gives rise to audible components that can be accurately predicted and precisely controlled.

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ABSTRACT

A brain-machine interface is a communication system that does not depend on the brains normal output pathways of peripheral nerves and muscles. It is a new communication link between a functioning human brain and the outside world.These are electronic interfaces with the brain, which has the ability to send and receive signals from the brain. BMI uses brain activity to command, control, actuate and communicate with the world directly through brain integration with peripheral devices and systems. The signals from the brain are taken to the computer via the implants for data entry without any direct brain intervention. BMI transforms mental decisions and/or reactions into control signals by analyzing the bioelectrical brain activity.

While linking the brain directly with machines was once considered science fiction, advances over the past few years have made it increasingly viable. It is an area of intense research with almost limitless possibilities. The human brain is the most complex physical system we know of, and we would have to understand its operation in great detail to build such a device. An immediate goal of brain-machine interface study is to provide a way for people with damaged sensory/motor functions to use their brain to control artificial devices and restore lost capabilities. By combining the latest developments in computer technology and hi-tech engineering, paralyzed persons will be able to control a motorized wheel chair, computer painter, or robotic arm by thought alone. In this era where drastic diseases are getting common it is a boon if we can develop it to its full potential. Recent technical and theoretical advances, have demonstrated the ultimate feasibility of this concept for a wide range of space-based applications. Besides the clinical purposes such an interface would find immediate applications in various technology products also.

INTRODUCTION

Picture a time when humans see in the UV and IR portions of the electromagnetic spectrum, or hear speech on the noisy flight deck of an aircraft carrier; or when soldiers communicate by thought alone. Imagine a time when the human brain has its own wireless modem so that instead of acting on thoughts, war fighters have thoughts that act. Imagine that one day we will be able to download vast amounts of knowledge directly to our brain! So as to cut the lengthy processes of learning everything from scratch. Instead of paying to go to university we could pay to get a “knowledge implant” and perhaps be able to obtain many lifetimes worth of knowledge and expertise in various fields at a young age..

When we talk about high end computing and intelligent interfaces, we just cannot ignore robotics and artificial intelligence. In the near future, most devices would be remote/logically controlled. Researchers are close to breakthroughs in neural interfaces, meaning we could soon mesh our minds with machines. This technology has the capability to impact our lives in ways that have been previously thought possible in only sci-fi movies.

Brain-Machine Interface (BMI) is a communication system, which enables the user to control special computer applications by using only his or her thoughts. It will allow human brain to accept and control a mechanical device as a part of the body. Data can flow from brain to the outside machinery, or to brain from the outside machinery. Different research groups have examined and used different methods to achieve this. Almost all of them are based on electroencephalography (EEG) recorded from the scalp. Our major goal of such research is to create a system that allow patients who have damaged their sensory/motor nerves severely to activate outside mechanisms by using brain signals.

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ABSTRACT

The seminar is about polymers that can emit light when a voltage is applied to it. The structure comprises of a thin film of semiconducting polymer sandwiched between two electrodes (cathode and anode).When electrons and holes are injected from the electrodes, the recombination of these charge carriers takes place, which leads to emission of light .The band gap, ie. The energy difference between valence band and conduction band determines the wavelength (colour) of the emitted light.
They are usually made by ink jet printing process. In this method red green and blue polymer solutions are jetted into well defined areas on the substrate. This is because, PLEDs are soluble in common organic solvents like toluene and xylene .The film thickness uniformity is obtained by multi-passing (slow) is by heads with drive per nozzle technology .The pixels are controlled by using active or passive matrix. The advantages include low cost, small size, no viewing angle restrictions, low power requirement, biodegradability etc. They are poised to replace LCDs used in laptops and CRTs used in desktop computers today. Their future applications include flexible displays which can be folded, wearable displays with interactive features, camouflage etc.

INTRODUCTION

Imagine these scenarios
- After watching the breakfast news on TV, you roll up the set like a large handkerchief, and stuff it into your briefcase. On the bus or train journey to your office, you can pull it out and catch up with the latest stock market quotes on CNBC.
- Somewhere in the Kargil sector, a platoon commander of the Indian Army readies for the regular satellite updates that will give him the latest terrain pictures of the border in his sector. He unrolls a plastic-like map and hooks it to the unit’s satellite telephone. In seconds, the map is refreshed with the latest high resolution camera images grabbed by an Indian satellite which passed over the region just minutes ago.
Don’t imagine these scenarios at least not for too long.The current 40 billion-dollar display market, dominated by LCDs (standard in laptops) and cathode ray tubes (CRTs, standard in televisions), is seeing the introduction of full-color LEP-driven displays that are more efficient, brighter, and easier to manufacture. It is possible that organic light-emitting materials will replace older display technologies much like compact discs have relegated cassette tapes to storage bins. .

The origins of polymer OLED technology go back to the discovery of conducting polymers in 1977,which earned the co-discoverers- Alan J. Heeger , Alan G. MacDiarmid and Hideki Shirakawa – the 2000 Nobel prize in chemistry. Following this discovery , researchers at Cambridge University UK discovered in 1990 that conducting polymers also exhibit electroluminescence and the light emitting polymer(LEP) was born!.

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ABSTRACT

Nowadays the number of people who are using Internet is dramatically increasing. With no hesitation, it can be said that the Internet is indeed the most popular media of communication prevailing in the present world scenario. But many of the users are nowadays facing the problem of failure in maintaining the connection with the cyber world.

The prime reason for the problem is that in the existing technology of connection with the Internet, a client is connected to a server through a number of nodes which depends on each other to facilitate the flow of information. The problem with the existing technology is that, even if a single intermediate node malfunctions, the whole system collapses. The solution to the problem is RAIN-Reliable Array Of Independent Nodes developed by the California Institute of Technology (Caltech), in collaboration with NASA’s Jet Propulsion Laboratory and the Defense Advanced Research Projects Agency (DARPA).
RAIN technology was able to offer the solution by minimizing the number of nodes in the chain connecting the client and server and also by making the existing nodes more robust and independent of each other. Also RAIN technology provides the novel feature of replacing a faulty node by a healthy one there by avoiding the break in information flow. In effect with the aid of RAIN connection between a client and server can be maintained despite all the existing problems.

INTRODUCTION

The Internet is changing the way that people manage and access information. In the last five years, the amount of traffic on the Internet has been growing at an exponential rate. The World Wide Web has evolved from a hobbyists’ toy to become one of the dominating media of our society. Ecommerce has grown past adolescence and multimedia content has come of age. Communication, computation and storage are converging to reshape the lives of everyone. Looking forward, this growth will continue for some time. The question is: what can we do to scale the Internet infrastructure to meet this growth?.

There are four trends in the current growth of the Internet:
1. Internet clients are becoming more numerous and varied. In addition to the ever-increasing number of PCs in offices and homes, there are new types of clients, such as mobile data units, (cell phones, PDAs, etc.) and home Internet appliances (set-top boxes, game consoles, etc.) In the next five years, these new types of Internet devices will pervade the Internet landscape.
2. To support these new clients, new types of networks are being designed and implemented. Examples are wireless data networks, broadband networks and voice-over-IP networks. Technologies are being developed to connect these new networks with the existing Internet backbone.
3. The content delivered over the Internet is evolving, partly because of the emergence of the new clients and new networks. There will be a growing presence of multimedia content, such as video, voice, music and gaming streams. The growth in content adds not only to the volume of the traffic, but also to the computation complexity in transporting and processing the traffic, thus accelerating the convergence between communication and computation.
4. New Internet applications emerge, both on the server side and the client side. As the Internet penetrates deeper and deeper into everyone’s life, the demand for security, reliability, convenience and performance sky-rockets. With the popularity of cars comes the invention of traffic lights and stop signs, the gas station and the drive-thru. As Internet makes its way into daily lives, the demand will grow for firewalls and VPNs, intrusion detection and virus scanning, server load balancing and content management, quality of service and billing/reporting applications. The list goes on, and will keep expanding.

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ABSTRACT

Mobile positioning technology has become an important area of research, for emergency as well as for commercial services. Mobile positioning in cellular networks will provide several services such as, locating stolen mobiles, emergency calls, different billing tariffs depending on where the call is originated, and methods to predict the user movement inside a region. The evolution to location-dependent services and applications in wireless systems continues to require the development of more accurate and reliable mobile positioning technologies. The major challenge to accurate location estimation is in creating techniques that yield acceptable performance when the direct path from the transmitter to the receiver is intermittently blocked. This is the Non-Line-Of-Sight (NLOS) problem, and it is known to be a major source of error since it systematically causes mobile to appear farther away from the base station (BS) than it actually is, thereby increasing the positioning error.
In this paper, we present a simple method for mobile telephone tracking and positioning with high accuracy. Through this we will discuss some technology used for mobile positioning and tracking

INTRODUCTION

As shown in Figure 3, the mobile telecommunication network includes a several base stations (BSs) T 1 to T N for providing mobile telecommunication service to a mobile subscriber through a mobile telephone M1, a base station controller (BSC) for controlling the BSs T 1 to T N, and a mobile telephone switching office (MTSO) for connecting the BSC to another BTS or a PSTN (Public Switched Telephone Network).

In a cellular mobile telecommunication network, the whole service area is divided into a several coverage areas having respective base stations (BS). Each BS coverage area is called a “cell.” Each BS is provided with a frequency of a range between 450 to900 MHz. More than one cells can use same frequency. Only condition is that no two adjacent cells must have same frequencies. An MTSO controls these BSs so that a subscriber can continue his call without interruption while moving between different cells. The MTSO can reduce the time required for calling a subscriber by locating the cell of the subscriber. In case of an emergency like a fire, or a patient needing first aid treatment, the mobile subscriber should be accurately located. Tracking the location of a mobile subscriber within the boundary of a cell in a mobile telecommunication network is known as “location based services
Mobile technology includes mainly two functions. They are call fixing and hands-off process. All the BSs are sending a signal of power 25 to 30w to the mobile unit. When a user switches ON his mobile, it will search for the strongest signal and got connected to that BS. Then the mobile unit sends an identification signal to the BS. When he fixes a call, the BS accepts the request and sends the request to the BSC and MTSO. Then the MTSO will searches where the subscriber is and connects the call.

When a user moves to another cell the MTSO will change the frequency allotted to it and allots the frequency of the new BS.For both these processes GEOLOCATION of the mobile unit is essential..

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