Fluorescent Multi-layer Disc

Requirements for removable media storage devices (RMSDs) used with personal computers have changed significantly since the introduction of the floppy disk in 1971. At one time, desktop computers depended on floppy disks for all of their storage requirements. Even with the advent of multigigabyte hard drives, floppy disks and other RMSDs are still an integral part of most computer systems, providing.

Transport between computers for data files and software

Backup to preserve data from the hard dive

A way to load the operating system software in the event of a hard failure.

            Data storage devices currently come in a variety of different capacities, access time, data transfer rate and cost per Gigabyte. The best overall performance figures are currently achieved using hard disk drives (HDD), which can be integrated into RAID systems (reliable arrays of inexpensive drives) at costs of $10 per GByte (1999). Optical disc drives (ODD) and tapes can be configured in the form of jukeboxes and tape libraries, with cost of a few dollars per GByte for the removable media. However, the complex mechanical library mechanism serves to limit data access time to several seconds and affects the reliability adversely.

            Most information is still stored in non-electronic form, with very slow access and excessive costs (e.g., text on paper, at a cost of $10 000 per GByte).

            Some RMSD options available today are approaching the performance, capacity, and cost of hard-disk drives. Considerations for selecting an RMSD include capacity, speed, convenience, durability, data availability, and backward-compatibility. Technology options used to read and write data include.

Magnetic formats that use magnetic particles and magnetic fields.

Optical formats that use laser light and optical sensors.

            Magneto-optical and magneto-optical hybrids that use a combination of magnetic and optical properties to increase storage capacity.

            The introduction of the Fluorescent Multi-layer Disc (FMD) smashes the barriers of existing data storage formats. Depending on the application and the market requirements, the first generation of 120mm (CD Sized) FMD ROM discs will hold 20 - 100 GigaBytes of pre -recorded data on 12 — 30 data layers with a total thickness of under 2mm.In comparison, a standard DVD disc holds just 4.7 gigabytes. With C3D’s (Constellation 3D) proprietary parallel reading and writing technology, data transfer speeds can exceed 1 gigabit per second, again depending on the application and market need.

FRAM

A ferroelectric memory cell consists of a ferroelectric capacitor and a MOS transistor. Its construction is similar to the storage cell of a DRAM. The difference is in the dielectric properties of the material between the capacitor's electrodes. This material has a high dielectric constant and can be polarized by an electric field. The polarisation remains until it gets reversed by an opposite electrical field. This makes the memory non-volatile. Note that ferroelectric material, despite its name, does not necessarily contain iron. The most well-known ferroelectric substance is BaTiO3.

A Ferroelectric memory cell consists of a ferroelectric capacitor and a MOS transistor. Its construction is similar to the storage cell of a DRAM. The difference is in the dielectric properties of the material between the capacitor's electrodes. This material has a high dielectric constant and can be polarized by an electric field. The polarisation remains until it gets reversed by an opposite electrical field. This makes the memory non-volatile.

Data is read by applying an electric field to the capacitor. If this switches the cell into the opposite state (flipping over the electrical dipoles in the ferroelectric material) then more charge is moved than if the cell was not flipped. This can be detected and amplified by sense amplifiers. Reading destroys the contents of a cell which must therefore be written back after a read. This is similar to the precharge operation in DRAM, though it only needs to be done after a read rather than periodically as with DRAM refresh.

FRAM is found mainly in consumer devices and because of its low power requirements, could also be used in devices that only need to activate for brief periods. FRAM allows systems to retain information even when power is lost, without resorting to batteries, EEPROM, or flash. Access times are the same as for standard SRAM, so there's no delay-at-write access as there is for EEPROM or flash. In addition, the number of write cycles supported by the FRAM components is nearly unlimited—up to 10 billion read/writes. FRAM combines the advantages of SRAM - writing is roughly as fast as reading, and EPROM - non-volatility and in-circuit programmability

Extreme Programming

Extreme Programming (XP) is actually a deliberate and disciplined approach to software development. About six years old, it has already been proven at many companies of all different sizes and industries worldwide. XP is successful because it stresses customer satisfaction. The methodology is designed to deliver the software your customer needs when it is needed. XP empowers software developers to confidently respond to changing customer requirements, even late in the life cycle. This methodology also emphasizes teamwork. Managers, customers, and developers are all part of a team dedicated to delivering quality software. XP implements a simple, yet effective way to enable groupware style development.

XP improves a software project in four essential ways; communication, simplicity feedback, and courage. XP programmers communicate with their customers and fellow programmers. They keep their design simple and clean. They get feedback by testing their software starting on day one. They deliver the system to the customers as early as possible and implement changes as suggested. With this foundation XP programmers are able to courageously respond to changing requirements and technology. XP is different. It is a lot like a jig saw puzzle. There are many small pieces. Individually the pieces make no sense, but when combined together a complete picture can be seen. This is a significant departure from traditional software development methods and ushers in a change in the way we program.

If one or two developers have become bottlenecks because they own the core classes in the system and must make all the changes, then try collective code ownership. You will also need unit tests. Let everyone make changes to the core classes whenever they need to. You could continue this way until no problems are left. Then just add the remaining practices as you can. The first practice you add will seem easy. You are solving a large problem with a little extra effort. The second might seem easy too. But at some point between having a few XP rules and all of the XP rules it will take some persistence to make it work. Your problems will have been solved and your project is under control. It might seem good to abandon the new methodology and go back to what is familiar and comfortable, but continuing does pay off in the end. Your development team will become much more efficient than you thought possible. At some point you will find that the XP rules no longer seem like rules at all. There is a synergy between the rules that is hard to understand until you have been fully immersed. This up hill climb is especially true with pair programming, but the pay off of this technique is very large. Also, unit tests will take time to collect, but unit tests are the foundation for many of the other XP practices so the pay off is very great.

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Embedded System in Automobiles

We read in newspapers that a doctor had successfully transplanted a  cardiac pacemaker in his patient’s chest by sitting around 200kilometres away. Also we know about driverless cars that could take us to the destiny  by using its inbuilt navigation systems. Embedded microprocessors or  micro controllers are the brain behind these.

An embedded system is any device controlled by instructions stored  on a chip. These devices are usually controlled by a micro processor that executes the instructions stored on a  read only memory(ROM) chip.

The software for the embedded system is called firmware. The firmware will be written in assembly language for time or resource critical operations or using higher level languages like C or embedded C. The software will be simulated using micro code simulators for the target processor. Since  they are supposed to perform only specific tasks, these programs are stored in read only memories(ROMs).Moreover they may need no or minimal inputs from the user, hence  the user interface like monitor, mouse and large keyboard etc,may be  absent.

Embedded systems are computer systems that monitor, respond to, or control an external environment. This environment is connected to the computer system through sensors, actuators, and other input-output interfaces. It may consist of physical or biological objects of any form and structure. Often humans are part of the connected external    world, but a wide range of other natural and artificial objects, as well as animals are also possible.

Embedded systems are also known as real time systems since they respond to an input or event and produce the result within a guaranteed   time period. This time period can be few microseconds to days or months. The computer system must meet various timing and other constraints that are imposed on it by the real-time behavior of the external world to which it is interfaced. Hence comes the name real time. Another  Name for many of these systems is reactive systems, because their primary purpose is to respond to or react to signals from their environment. A real time computer system may be a component of a larger system in which it is embedded; reasonably such a computer component is called an embedded system.

Embedded systems control engine management systems in automobiles, monitor home heating systems and regulate the quiet operation and the even distribution of laundry in washing machines. They are the heart of toys like Furby and Tamagotchi, of golf balls that cannot get lost and of gas pumps at gasoline stations that advertise nearby restaurants on video. Above all, state-of-the art communications equipment like WAP mobile telephones, MP3 players, set-top boxes and Net devices would not be possible without these powerful miniature brains.

Applications and examples of real time systems are ubiquitous and proliferating, appearing as part of our commercial, government, military, medical, educational, and cultural infrastructures. Included are:

• Vehicle systems for automobiles, subways, aircraft, railways and ships.

• Traffic control for highways, airspace, railway tracks and shipping lanes.

• Process control for power plants, chemical plants and consumer products such as soft drinks and beer.

• Medical systems for radiation therapy, patient monitoring and defibrillation

• Military uses such as firing weapons, tracking and command and control.

• Manufacturing systems with robots.

• Telephone, radio and satellite communications.

• Computer games.

• Multi media systems that provide text, graphic, audio and video interfaces.

• House holds systems for monitoring and controlling appliances.

• Building managers that controls such entities as heat, light, Doors and elevators.

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E-Intelligence

Organizations have, over the years, successfully employed business intelligence tools like OLAP and data warehousing to improve the supply of business information to end users for cross industry applications like finance and customer relationship management, and in vertical markets such as retail, manufacturing, healthcare, banking, financial services, telecommunications, and utilities. In the recent years, the Internet has opened up an entirely new channel for marketing and selling products. Companies are taking to e-business in a big way. The issue facing end users as organizations deploy e-business systems is that they do have not had the same business intelligence capabilities available to them in e-business systems as they do in the traditional corporate operating environment. This prevents businesses from exploiting the full power of the Internet as a sales and marketing channels.

As a solution, vendors are now developing business intelligence applications to capture and analyze the information flowing through e-business systems, and are developing Web-based information portals that provide an integrated and personalized view of enterprise-wide business information, applications, and services. This advanced business intelligence systems are called E-intelligence systems

Digital water marking

In recent years, the distribution of works of art, including pictures, music, video and textual documents, has become easier. With the widespread and increasing use of the Internet, digital forms of these media (still images, audio, video, text) are easily accessible. This is clearly advantageous, in that it is easier to market and sell one's works of art. However, this same property threatens copyright protection. Digital documents are easy to copy and distribute, allowing for pirating. There are a number of methods for protecting ownership. One of these is known as digital watermarking.

Digital watermarking is the process of inserting a digital signal or pattern (indicative of the owner of the content) into digital content. The signal, known as a watermark, can be used later to identify the owner of the work, to authenticate the content, and to trace illegal copies of the work.

Watermarks of varying degrees of obtrusiveness are added to presentation media as a guarantee of authenticity, quality, ownership, and source.

To be effective in its purpose, a watermark should adhere to a few requirements. In particular, it should be robust, and transparent. Robustness requires that it be able to survive any alterations or distortions that the watermarked content may undergo, including intentional attacks to remove the watermark, and common signal processing alterations used to make the data more efficient to store and transmit. This is so that afterwards, the owner can still be identified. Transparency requires a watermark to be imperceptible so that it does not affect the quality of the content, and makes detection, and therefore removal, by pirates less possible.

The media of focus in this paper is the still image. There are a variety of image watermarking techniques, falling into 2 main categories, depending on in which domain the watermark is constructed: the spatial domain (producing spatial watermarks) and the frequency domain (producing spectral watermarks). The effectiveness of a watermark is improved when the technique exploits known properties of the human visual system. These are known as perceptually based watermarking techniques. Within this category, the class of image-adaptive watermarks proves most effective.

In conclusion, image watermarking techniques that take advantage of properties of the human visual system, and the characteristics of the image create the most robust and transparent watermarks.

DNA computer

Computer chip manufacturers are furiously racing to make the next microprocessor that will topple speed records. Sooner or later, though, this competition is bound to hit a wall. Microprocessors made of silicon will eventually reach their limits of speed and miniaturization. Chip makers need a new material to produce faster computing speeds.

 Millions of natural supercomputers exist inside living organisms, including your body. DNA (deoxyribonucleic acid) molecules, the material our genes are made of, have the potential to perform calculations many times faster than the world's most powerful human-built computers. DNA might one day be integrated into a computer chip to create a so-called biochip that will push computers even faster. DNA molecules have already been harnessed to perform complex mathematical problems.

While still in their infancy, DNA computers will be capable of storing billions of times more data than your personal computer. DNA can be used to calculate complex mathematical problems. However, this early DNA computer is far from challenging silicon-based computers in terms of speed. The Rochester team's DNA logic gates are the first step toward creating a computer that has a structure similar to that of an electronic PC. Instead of using electrical signals to perform logical operations, these DNA logic gates rely on DNA code. They detect fragments of genetic material as input, splice together these fragments and form a single output

corDECT Wireless in Local Loop System

corDECT is an advanced, field proven, Wireless Access System developed by Midas Communication Technologies and the Indian Institute of Technology, Madras, in association with Analog Devices Inc., USA.

corDECT provides a complete wireless access solution for new and expanding telecommunication networks with seamless integration of both voice and Internet services. It is the only cost-effective Wireless Local Loop (WLL) system in the world today that provides simultaneous toll-quality voice and 35 or 70 kbps Internet access to wireless subscribers.

corDECT is based on the DECT standard specification from the European Telecommunication Standards Institute (ETSI). In addition, it incorporates new concepts and innovative designs brought about by the collaboration of a leading R & D company, a renowned university, and a global semiconductor manufacturer. This alliance has resulted in many breakthrough concepts including that of an Access Network that segregates voice and Internet traffic and delivers each, in the most efficient manner, to the telephone network and the Internet respectively, without the one choking the other.

Computer Clothing

Wearable  computer  comprises  of  a  computer  built  within  an  ordinary  clothing. This  transformation  allows  it  to  be   worn  constantly,  with  the  goal  of  becoming  a  seamless  extension  of  body  and  mind. Equipped  with  various  sensors  which  measure  heart rate,  respiration,  footstep rate  etc,  the  apparatus  can  function  as  a  personal  safety  device  for  reducing  crime,  as  well  as  personal  health  monitor  for  improving   health care  by  encouraging  individuals  to  take  an  active  role  in  diagnosis  and  body  maintenance.  The  ‘wearable  computer’  apparatus  is  embedded   within  nontransparent   clothing  which  provides  shielding.  Electronic  circuits  are  built  entirely  out  of  textiles  to  distribute  data  and  power  and  perform  touch  sensing.  These  circuits  are  passive  components  sewn  from  conductive  yarns  as  well  as  conventional  components  to  create  interactive  electronic  devices,  such    as  musical  keyboards  and  graphic  input  surfaces.

Blue ray DVD

Tokyo Japan, February 19, 2002: Nine leading companies today announced that they have jointly established the basic specifications for a next generation large capacity optical disc video recording format called "Blu-ray Disc". The Blu-ray Disc enables the recording, rewriting and play back of up to 27 gigabytes (GB) of data on a single sided single layer 12cm CD/DVD size disc using a 405nm blue-violet laser.

By employing a short wavelength blue violet laser, the Blu-ray Disc successfully minimizes its beam spot size by making the numerical aperture (NA) on a field lens that converges the laser 0.85. In addition, by using a disc structure with a 0.1mm optical transmittance protection layer, the Blu-ray Disc diminishes aberration caused by disc tilt. This also allows for disc better readout and an increased recording density. The Blu-ray Disc's tracking pitch is reduced to 0.32um, almost half of that of a regular DVD, achieving up to 27 GB high-density recording on a single sided disc.

Because the Blu-ray Disc utilizes global standard "MPEG-2 Transport Stream" compression technology highly compatible with digital broadcasting for video recording, a wide range of content can be recorded. It is possible for the Blu-ray Disc to record digital high definition broadcasting while maintaining high quality and other data simultaneously with video data if they are received together. In addition, the adoption of a unique ID written on a Blu-ray Disc realizes high quality copyright protection functions.

The Blu-ray Disc is a technology platform that can store sound and video while maintaining high quality and also access the stored content in an easy-to-use way. This will be important in the coming broadband era as content distribution becomes increasingly diversified. The nine companies involved in the announcement will respectively develop products that take full advantage of Blu-ray Disc's large capacity and high-speed data transfer rate. They are also aiming to further enhance the appeal of the new format through developing a larger capacity, such as over 30GB on a single sided single layer disc and over 50GB on a single sided double layer disc. Adoption of the Blu-ray Disc in a variety of applications including PC data storage and high definition video software is being considered.

Cellular Digital Packet Data

Cellular Digital Packet Data (CDPD) systems offer what is currently one of the most advanced means of wireless data transmission technology. Generally used as a tool for business, CDPD holds promises for improving law enforcement communications and operations. As technologies improve, CDPD may represent a major step toward making our nation a wireless information society. While CDPD technology is more complex than most of us care to understand, its potential benefits are obvious even to technological novices.

In this so-called age of information, no one need to be reminded of speed but also accuracy in the storage, retrieval and transmission of data. The CDPD network is a little one year old and already is proving to be a hot digital enhancement to the existing phone network. CDPD transmits digital packet data at 19.2 Kbps, using idle times between cellular voice calls on the cellular telephone network.                             

CDPD technology represent a way for law enforcement agencies to improve how they manage their communications and information systems. For over a decade, agencies around the world have been experimenting with placing Mobile Data Terminals(MDT) in their vehicles to enhance officer safety and efficiency.

Early MDT’s transmits their information using radio modems. In this case data could be lost in transmission during bad weather or when mobile units are not properly located in relation to transmission towers. More recently MDT’s have transmitted data using analog cellular telephone modems. This shift represented an improvement in mobile data communications, but systems still had flaws which limited their utility.

Since the mid-1990’s, computer manufacturers and the telecommunication industry have been experimenting with the use of digital cellular telecommunications as a wireless means to transmit data. The result of their effort is CDPD systems. These systems allow users to transmit data with a higher degree of accuracy, few service interruptions, and strong security. In addition CDPD technology represent a way for law enforcement agencies to improve how they manage their communications and information systems. This results in the capacity for mobile users to enjoy almost instantaneous access to information.

Animatronics

The first use of Audio-Animatronics was for Walt Disney's Enchanted Tiki Room in Disneyland, which opened in June, 1963. The Tiki birds were operated using digital controls; that is, something that is either on or off. Tones were recorded onto tape, which on playback would cause a metal reed to vibrate. The vibrating reed would close a circuit and thus operate a relay. The relay sent a pulse of energy (electricity) to the figure's mechanism which would cause a pneumatic valve to operate, which resulted in the action, like the opening of a bird's beak. Each action (e.g., opening of the mouth) had a neutral position, otherwise known as the "natural resting position" (e.g., in the case of the Tiki bird it would be for the mouth to be closed). When there was no pulse of energy forthcoming, the action would be in, or return to, the natural resting position.

This digital/tone-reed system used pneumatic valves exclusively--that is, everything was operated by air pressure. Audio-Animatronics' movements that were operated with this system had two limitations. First, the movement had to be simple--on or off. (e.g., The open and shut beak of a Tiki bird or the blink of an eye, as compared to the many different positions of raising and lowering an arm.) Second, the movements couldn't require much force or power. (e.g., The energy needed to open a Tiki Bird's beak could easily be obtained by using air pressure, but in the case of lifting an arm, the pneumatic system didn't provide enough power to accomplish the lift.) Walt and WED knew that this this pneumatic system could not sufficiently handle the more complicated shows of the World's Fair. A new system was devised.

In addition to the digital programming of the Tiki show, the Fair shows required analog programming. This new "analog system" involved the use of voltage regulation. The tone would be on constantly throughout the show, and the voltage would be varied to create the movement of the figure. This "varied voltage" signal was sent to what was referred to as the "black box." The black boxes had the electronic equipment that would receive the signal and then activate the pneumatic and hydraulic valves that moved the performing figures. The use of hydraulics allowed for a substantial increase in power, which was needed for the more unwieldy and demanding movements. (Hydraulics were used exclusively with the analog system, and pneumatics were used only with the tone-reed/digital system.)

There were two basic ways of programming a figure. The first used two different methods of controlling the voltage regulation. One was a joystick-like device called a transducer, and the other device was a potentiometer (an instrument for measuring an unknown voltage or potential difference by comparison to a standard voltage--like the volume control knob on a radio or television receiver). If this method was used, when a figure was ready to be programmed, each individual action--one at a time-- would be refined, rehearsed, and then recorded. For instance, the programmer, through the use of the potentiometer or transducer, would repeatedly rehearse the gesture of lifting the arm, until it was ready for a "take." This would not include finger movement or any other movements, it was simply the lifting of an arm. The take would then be recorded by laying down audible sound impulses (tones) onto a piece of 35 mm magnetic film stock. The action could then instantly be played back to see if it would work, or if it had to be redone. (The machines used for recording and playback were the 35 mm magnetic units used primarily in the dubbing process for motion pictures. Many additional units that were capable of just playback were also required for this process. Because of their limited function these playback units were called "dummies.")

Eventually, there would be a number of actions for each figure, resulting in an equal number of reels of 35 mm magnetic film (e.g., ten actions would equal ten reels). All individual actions were then rerecorded onto a single reel--up to ten actions, each activated by a different tone, could be combined onto a single reel. For each action/reel, one dummy was required to play it back. Thus for ten actions, ten playback machines and one recording machine were required to combine the moves onto a new reel of 35 mm magnetic film.

"Sync marks" (synchronization points) were placed at the front end of each individual action reel and all of the dummies were interlocked. This way, during the rerecording, all of the actions would start at the proper time. As soon as it was finished, the new reel could be played back and the combined actions could be studied. Wathel, and often times Marc Davis (who did a lot of the programming and animation design for the Carousel show) would watch the figure go through the motions of the newly recorded multiple actions. If it was decided that the actions didn't work together, or something needed to be changed, the process was started over; either by rerecording the individual action, or by combining the multiple actions again. If the latter needed to be done, say the "arm lift action" came in too early, it would be accomplished by unlocking the dummy that had the "arm-lift reel" on it. The film would then be hand cranked, forward or back, a certain number of frames, which changed the start time of the arm lift in relation to the other actions. The dummies would be interlocked, and the actions, complete with new timing on the arm lift, would be recorded once again.

With this dummy system, the dialogue and music could also be interlocked and synched-up with the actions. Then the audio could be listened to as the figure went through the actions. This was extremely helpful in getting the gestures and actions to match the dialogue.

The other method used for programming a figure was the control harness. It was hooked up so that it would control the voltage regulation relative to the movements of the harness. Wathel tells horror stories of sitting in the harness for hours upon end, trying to keep every movement in his body to a minimum, except for the several movements they wanted for the figure. This method had the advantage of being able to do several actions at once, but obviously due to the complexities, a great deal of rehearsal was required.

There was also a harness for the mouth movements. Ken O'Brien, who was responsible for programming most of the mouth movements, used a transducer at first for the mouth programming. Later they designed a harness for his head that controlled the movement of the jaw," remembered Gordon Williams, recording engineer on the AA figures for the Fair. "It was easier for him to coordinate the movement, because he could watch the movement at the same time that he was doing it."

ADSL

            Digital Subscriber Line (DSL) is a technology that brings high bandwidth information to homes and small businesses over the existing 2 wire copper telephone lines. Since DSL works on the existing telephone infrastructure, DSL systems are considered a key means of opening the bottleneck in the of the existing telephone network, as telephone companies seek cost-effective ways of providing much higher speed to their customers. DSL is a technology that assumes digital data does not require change into analog form and back. This gives it two main advantages. Digital data is transmitted to your computer directly as digital data, and this allows the phone company to use a much wider bandwidth for transmitting it to you, thereby giving the user a huge boost in bandwidth compared to analog modems. Not only that, but DSL uses the existing phone line and in most cases does not require an additional phone line. The digital signal can be separated or filtered, so that some of the bandwidth can be used to transmit an analog signal so that normal telephone calls can be made while a computer is connected to the internet. This gives "always-on" Internet access and does not tie up the phone line. No more busy signals, no more dropped connections, and no more waiting for someone in the household to get off the phone.

            Because analog transmission only uses a small portion of the available amount of information that could be transmitted over copper wires, the maximum amount of data that you can receive using ordinary modems is about 56 Kbps (thousands of bits per second). With ISDN you can receive up to 128 Kbps. This shows that the ability of your computer to receive information is constrained by the fact that the telephone company filters information that arrives as digital data, puts it into analog form for your telephone line, and requires your modem to change it back into digital. In other words, the analog transmission between your home or business and the phone company is a bandwidth bottleneck. DSL however offers users a choice of speeds ranging from 144 Kbps to 1.5Mbps. This is 2.5 times to 25 times faster than a standard 56 Kbps dial-up modem. This digital service can be used to deliver bandwidth intensive applications like streaming audio/video, online games, application programs, telephone calling, video conferencing and other high-bandwidth services. 

Adding Intelligence to Internet

            Satellites have been used for years to provide communication network links.  Historically, the use of satellites in the Internet can be divided into two generations. In the first generation, satellites were simply used to provide commodity links (e.g., T1) between countries. Internet Protocol (IP) routers were attached to the link endpoints to use the links as single-hop alternatives to multiple terrestrial hops. Two characteristics marked these first-generation systems: they had limited bandwidth, and they had large latencies that were due to the propagation delay to the high orbit position of a geosynchronous satellite.

            In the second generation of systems now appearing, intelligence is added at the satellite link endpoints to overcome these characteristics.  This intelligence is used as the basis for a system for providing Internet access engineered using a collection or fleet of satellites, rather than operating single satellite channels in isolation. Examples of intelligent control of a fleet include monitoring which documents are delivered over the system to make decisions adaptively on how to schedule satellite time; dynamically creating multicast groups based on monitored data to conserve satellite bandwidth; caching documents at all satellite channel endpoints; and anticipating user demands to hide latency.

            This paper examines several key questions arising in the design of a satellite-based system:

Ø  Can international Internet access using a geosynchronous satellite be competitive with today's terrestrial networks?

Ø  What elements constitute an "intelligent control" for a satellite-based Internet link?

Ø  What are the design issues that are critical to the efficient use of satellite channels?

            The paper is organized as follows. The next section, Section 2, examines the above questions in enumerating principles for second-generation satellite delivery systems. Section 3 presents a case study of the Internet Delivery System (IDS), which is currently undergoing worldwide field trials.