What Is Biometrics?

Biometrics can be defined as the technique of studying the physical characteristics of a personsuch as fingerprints, hand geometry, eye structureetc. to establish his or her identity. Thisscience is primarily implemented to identify individuals.

Why Biometrics?

The use of biometrics is no longer restricted todefense establishments or sensitive areas. Anincreased need for security has prompted eveneveryday office goers to install fingerprint recognitiondevices to boot up their laptops, thumbdrives and other daily use gadgets.

How Biometric Processes Work

The concept of Biometric verification is simple. The system has some pre-stored data. When youapproach the system (say a fingerprint scanner),your finger is scanned and matched with arecord of fingerprints already in its database. Only when it finds a match, access is granted. The concept might be simple, but the process isquite ingenious.

GPS(Global Positioning System)

The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR), is a satellite navigation system used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit. It uses an intermediate circular orbit (ICO) satellite constellation of at least 24 satellites.

The GPS system was designed by and is controlled by the United States Department of Defense and can be used by anyone, free of charge. The GPS system is divided into three segments: space, control, and user. The space segment comprises the GPS satellite constellation. The control segment comprises ground stations around the world that are responsible for monitoring the flight paths of the GPS satellites, synchronizing the satellites' onboard atomic clocks, and uploading almanac data for transmission by the satellites. The user segment comsists of GPS receivers used for both military and civilian applications. A GPS receiver (GPSR) decodes time signal transmissions from multiple satellites and calculates its position by trilateration.

EDGE (Enhanced Data Rates For Gsm Evolution )

EDGE is an enhancement to the GSM mobile cellular phone system. It is a step towardsthe evolution of 3G networks. The name EDGE stands for Enhanced Data rates for GSM.Evolution. When applied to GSM/GPRS networks, EDGE dramatically increases datathroughputs, as well as network capacity. EDGE provides three times the data capacity ofGPRS. Using EDGE, operators can handle three times more subscribers than GPRS,triple their data rate per subscriber, or add extra capacity to their voice communications. EDGE uses the same TDMA (Time Division Multiple Access) frame structure, logicchannel and 200 kHz carrier bandwidth as today's GSM networks, which allows existingcell plans to remain intact. But it uses a new modulation scheme, 8-PSK. 

Evolution of EDGE

As the mobile communication market develops, interest is building for data applicationsand higher data rate operation. The GSM system is meeting this challenge through asequence of evolutionary steps. From the initial voice only network, the system firstadded the short messaging services (SMS) followed by high speed circuit data (HSCSD)and then adding GPRS. All of these services use the same modulation format of theoriginal GSM voice network (GMSK) and change the allocation of the bits and or packetsto improve the basic GSM data rate. After GPRS, the next step in improving the GSM system data rate is to change the signalto a type that has greater bandwidth efficiency, i.e. more bits per second can be supportedper unit bandwidth. This is most economically implemented throughout the existing GSMinfrastructure when the new signal type has identical bandwidth occupancycharacteristics as the original GMSK signal. This is the motivation behind this next GSMenhancement, called EDGE. The primary objective for the EDGE signal is to triple theon-air data rate while meeting essentially the same bandwidth occupancy of the originalGMSK signal.

Over view of EDGE

EDGE is an enhancement to the GSM mobile cellular phone system. The name EDGEstands for Enhanced Data rates for GSM Evolution. EDGE represents a significantinnovation in radio technology. When applied to GSM/GPRS networks, EDGEdramatically increases data throughputs, as well as network capacity. It does so through acombination of techniques that is described in detail below.

EDGE systems will enable consumers to use cellular phones, PDAs and other wireless Internet devices to place phone calls, surf the Web, or download and play video, audio,and multimedia content. EDGE is designed to deliver data at rates up to 473.6 kbps, triplethe bandwidth of most wireless services. Built on the existing GSM (Global System for Mobile) standard and core network infrastructure, EDGE is expected to deploy widelythroughout the Americas, Asia Pacific and Europe. EDGE can actually be applied to both circuit-switched data service, where the service istechnically referred to as Enhanced Circuit-Switched Data (ECSD), or to packet-switcheddata service, where the service is technically referred to as Enhanced GPRS (EGPRS). However, most GSM operators deploying EDGE, including AT&T Wireless, areconcentrating on packet service. With EDGE, the radio interface keeps the same time-slotstructure as GPRS and GSM, and is still considered a Time-Division Multiple Access(TDMA) system. Many signaling (control) protocols, and all user level (IP, UDP, TCP,etc.) protocols, are the same for both GPRS and EDGE. This is possible because EDGEoperates only at the physical layer (radio modulation and forward error correction) andlink layers (access control and retransmissions). Higher layer protocols are unaffected. Consequently, any application developed for GPRS will immediately work with EDGE. From an application perspective, EDGE behaves identically to GPRS, just faster and withvery high reliability. From an operator deployment point of view, EDGE can be added toan existing GSM/GPRS network with minimal new hardware, especially if it is a newernetwork that was designed to be EDGE capable, such as operated by AT&T Wireless. EDGE radio technology uses the following techniques to boost throughput speedsand to increase capacity: new modulation, flexible channel coding, link adaptation, andincremental redundancy, an effective method of retransmitting packets, a largeraddressing window, and tight interleaving. Fully compatible with legacy GSM/GPRS, EDGE is an evolutionary step towards highspeed data and multimedia services. It out performs the GSM throughput capacity byup to 300%.It is a technology that gives GSM the capacity to handle services for the thirdgeneration of mobile telephony. Using EDGE, operators can handle three times moresubscribers than GPRS, triple their data rate per subscriber, or add extra capacity to theirvoice communications. A cost-efficient way to optimize high-quality data servicesavailability, EDGE’s performance satisfies both subscribers and operators. It will allow GSM operators to use existing GSM radio bands to offer wireless multimedia IP-basedservices and applications at theoretical maximum speeds of 384 kbps with a bit-rate of 48kbps per timeslot and up to 69.2 kbps per timeslot in good radio conditions.  The method chosen by EDGE is a combination of Time and Frequency Division Multiple Access (TDMA/FDMA) and 200 kHz carrier bandwidth as today's GSMnetworks, which allows existing cell plans to remain intact. Since the radio spectrum is alimited resource shared by all users, a method must be devised to divide up the bandwidthamong as many users as possible. The FDMA part involves the division by frequency ofthe (maximum) 25MHz bandwidth in to 124 carrier frequencies spaced 200 KHz apart. One or more carrier frequencies are assigned to each base station. Each of these carrierfrequencies is then divided in time, using a TDMA scheme. The fundamental unit of timein the TDMA scheme is called a burst period and it lasts for 15/26 ms. Eight burst periodsare grouped into a TDMA frame(120/26 ms) which forms the basic unit for the definitionof logic channels. One physical channel is one burst periods per TDMA frame.To increase the gross data rate, a new modulation scheme is introduced which provideshigher data rates, high spectral efficiency. Basically, EDGE technology introduces a newmodulation technique, that can be used to transmit both packet switched and circuitswitched voice and data services. It also introduces a new technology not found in GPRS, Incremental Redundancy, which, instead of retransmitting disturbed packets, sends moreredundancy information to be combined in the receiver. This increases the probability ofcorrect decoding. EDGE is therefore an add-on to GPRS and cannot work alone. GPRS and EDGE usesdifferent protocols and different behavior on the base station system side. Howeer in theore network side, GPRS and EDGE share the same packet handling protocols andtherefore behave in the same way. Reuse of the existing GPRS core infrastructureemphasizes the fact that EDGE is only an add-on to GPRS. For the end user, EDGE provides improved quality of service, increased data capacityand higher data throughput. It also decreases response times for all data services, thuskeeping end users satisfied and connected. Potentially lower price per bit, Lower cost ofdata capacity for high-speed data applications gives the operator flexibility in pricing. EDGE will provide the solution or operators wanting to offer personal multimediaservices early and who need to increase the data capacity in their GSM network prior toUMTS deployment. EDGE is especially valuable for operators that do not deploy UMTS. EDGE will not replace existing investments or services but will upgrade them to a highly

competitive level through gradual investment.

? When we watch a TV show that has a shot of a computer monitor, the monitor
                    

appears to flicker.
                    

         If you have ever tried to point your video camera at your TV set or your computer monitor to record the image you see, you know that it does not work -- instead of the stable image that your eyes see, there is either incredible flicker or a black rolling bar. This short video file shows you what happens when you try it. The video shows two different frequencies for the monitor: 70 Hz and then 60 Hz.

The flicker is caused by two things:

·         A difference in the scanning frequency between the TV and the camera

·         A difference in the way the phosphor dots are perceived between the human eye and the camera's image sensor

If you have read the HowStuffWorks article How Television Works, then you know how a standard CRT display works. A single electron beam scans horizontal lines of pixels across the screen, lighting up each pixel when the beam hits it. The pixels are made of individual phosphor dots that glow when the beam hits them. To our eyes, the dots glow for about 1/30th of a second, so we see a steady image. For a video camera, however, the dots do not appear to glow nearly as long -- the camera is much less sensitive to persistence than our eyes.

When you watch the video, the second shot has a monitor refreshing every 60th of a second and a camera taking a frame every 60th of a second. The wide black bar that you see shows you a collection of pixels that have faded by the time the camera tries to image them. The bar rolls because the camera and monitor are not exactly synchronized. TV stations use special monitors and cameras that are able to sync with one another, so the camera's scan follows the monitor's scan.

Some camcorders use 30 frames per second (fps) and do not have the problem if you can get the monitor to refresh at a rate of 60 fps progressive. They may also work on TVs (see How HDTV Works for a description of progressive vs. interlaced scanning). Some camcorders use a 1/100th of a second shutter speed (causing rolling black bars) unless you turn the "steady shot" mode off to get it back to 1/60th or 1/30th of a second shutter speed.

To record a computer monitor image, you need to experiment with different refresh rates in the monitor settings or in the host computer software. There are display cards for personal computers whose video drivers allow you to pick the refresh rate. This rate setting may take some experimentation to get it to match your camera setting. If your camera uses 24 fps, use a multiple of 24 -- use a refresh rate of 48 Hz or 72 Hz to get rid of the annoying scrolling bars. Use 640 x 480 mode on the monitor to help lessen the problem. Television sets with the usual cathode ray picture tube do not have an adjustable screen refresh rate. They will either work with your camera or they won't.

For a person trying to take a screen shot using a video camera, the easiest solution is to shoot off an LCD panel on a portable computer. Flat-screen LCDs do not have this problem.