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IRIDIUM

    The cell phones being used all over the world have made life very easy for the person on the move. But he main drawbacks of this system is that their high capital cost has prevented coverage beyond heavily populated areas. Deep mountain valleys, remote islands and sparsely populated regions still remain cellular s dead angle zones, unfortunately for frequent travelers, mountain climbers and others constantly on the move. Also cell-phones can be used only within a particular service area. Consequently many businessmen have lost important deals due to cellular loopholes. be used only within a particular service area. Consequently many businessmen have lost important deals due to cellular loopholes. Such mishaps stemming from the land-based service will become a thing of past by November this year when the satellite-based mobile telephone service called the Iridium system comes up. The Iridium system is a satellite based, wireless, personal communication network whose idea was first unveiled by experts at Motorola in June 1990. Their initial architectural approach called for seven slender rings of satellite with eleven satellites in each ring, i.e. a total of 77 satellites. It was due to this reason that Motorola engineers named their mobile communication systems as IRIDIUM in direct analogy with the 77 electrons circling around the iridium’s nucleus. However it was later decided to increase the transmitter power of each satellite and consequently the number of satellites was decided to be reduced to 66. The element with 66 electrons is dysprosium, which does not have the same significant pronouncibility as IRIDIUM hence the system was not renamed. significant pronouncibility as IRIDIUM hence the system was not renamed. The satellites in the IRIDIUM system are configured in six planes of eleven satellites each. The planes are in or near polar orbit (86.4degree inclination) adjacent planes are spaced 31.587 degree apart around the equator thereby providing global coverage. The satellites altitude is 780 km. And the satellite weighs around 1600 lb. Each satellite in the IRIDIUM constellation will send out 48 pencil-thin spot beams each of which can handle 230 simultaneous duplex conversations. The transmission links between the hand-held communicators, the paging units and the remote area telephones are handled using L- Band signals in the 1.5 to 1.6 Ghz. Range. These inter-satellite links or cross links are operated in the Ka portion of the frequency band at 20 GHz.(signals in the 1.5 to 1.6 Ghz. Range. These inter-satellite links or cross links are operated in the Ka portion of the frequency band at 20 GHz.( Each satellite is connected to four other satellites by radio transmissions. The primary reason for the use of cross links in the IRIDIUM system is to minimize the number of gateway stations required to support the communications network. The inclusion of cross links in the IRIDIUM system also permits full global coverage including oceans and remote land areas with very low telephone traffic densities. The satellites provide the path to and from the users, while the gateway stations provide the connections between the satellite and the PSTN. When an IRIDIUM telephone is activated the nearest satellite in conjunction with the IRIDIUM network will determine account validity and the location of the user. The subscriber will select among cellular or satellite transmission alternatives depending on compatibility and the location of the user. The subscriber will select among cellular or satellite transmission alternatives depending on compatibility and availability to dispatch a call. If the subscribers local cellular system is unavailable the telephone will communicate directly with the satellite overhead. The call will the be transferred from satellite to satellite through the network to its destination - either an IRIDIUM telephone or an IRIDIUM ground station. The IRIDIUM system has achieved a milestone in the design and the implementation of the cross link network. It will offer the user the highest level of quality at the lowest possible price. —Shubhankar [TE Elecs]

Information Technology

A Real World Look At The Information Superhighway

Accelerating access to critical information Just as construction of the interstate highway system in the 1950s facilitated the expansion of America, the construction of information highways in the 1990s will generate economic and social changes well into the next century. A network made of thousands of overlapping, seamlessly interconnected networks is beginning to connect people, institutions, and services around the globe. This information superhighway is providing rich, far-reaching connections that are transforming the way we live and work, and raising the stakes for competitiveness in the world today. First used to describe the Clinton Administration's plans to develop a National Information Infrastructure (NII) in the U.S., the term "information superhighway" now refers to any large-scale, high-capacity telecommunications network that delivers interactive business, educational, and consumer services on a national or global level. Europe defines the movement of information across geographical boundaries as the "information society."

Mapping Objectives To succeed, a national or global information infrastructure (GII) must be built on a clearly articulated policy. It must meet real user needs to gain broad acceptance and support. In a recent survey conducted to gauge some of these needs, the American Electronics Association's NII/GII Task Force found that the most compelling factor for building the NII is increased business efficiency. International competitiveness was the second most frequently cited reason. The majority of survey participants believed widespread social benefits would accrue as a matter of course. This is proving true with the European Union TIDE program that gives advanced communication powers to the elderly and disabled.

A Smart Planet : Here are just a few of the countries that are preparing for a global information society today. The village of Jalapa de Diaz, Mexico, installed computers in its two-room schoolhouse and built a 60-foot high microwave tower. Schoolchildren can now work on projects with students in southern France and farmers can stay current with world crop prices. In China, a great project is underway to install a "Golden Bridge" that will interconnect new and existing information networks within the country. Applications planned for this information infrastructure include a national credit card system, a national commerce system, and a system to facilitate global trade. India is connecting its 70 biggest cities with a nationwide network that will ease the dissemination of government information and eventually provide an infrastructure for commercial applications. French citizens share information through a nationwide information service called MiniTel. Japan plans to wire all businesses, institutions, schools, and homes, with fiber-optic cable by the year 2015. In an era of global markets and competition, a solid information infrastructure is a critical national resource. Very soon geopolitical areas will be defined as much by their electronic boundaries as their geographic ones. The speed with which countries and regions can connect their information resources will dramatically affect the balance of economic power in the 21st century. The information superhighway is real and gaining momentum on a global scale today-- bringing profound changes in our lives.

"As we interconnect ourselves, many of the values of a nation-state will give way to those of both larger and smaller electronic communities. We will socialize in digital neighborhoods in which physical space will be irrelevant and time will play a different role." Nicholas Negroponte, MIT Media Lab. Paving the way for economic growth, national reach, and job expansion, The information superhighway also offers a viable solution for the pressing social challenges of our times, particularly those affecting education and healthcare delivery. The information superhighway lets individuals work together, accessing and generating information, without regard to geographical boundaries. This new world without limitations in space or time brings extraordinary advantages.

The Virtual Workplace : Telecommuting demonstrates what the information superhighway is all about: moving information to people, rather than people to information. Linked electronically, employees are living where they want, working more productively, and greatly reducing traffic congestion and environmental problems by commuting electronically. Smart Valley, a consortium in California's Silicon Valley, has successfully completed a teleworking pilot project with eight different organizations. This multi-organization project shows telecommuters experience a 20 percent productivity increase. 3Com is an active participant in this venture, connecting its own and other remotely located employees to head office resources via AccessBuilder, the company's remote access solution.

Business Not-as-Usual : Electronic mail, telecommuting, and video conferencing, innovations that are revolutionizing the way we work and where we work, bring greater efficiency and reduced operating costs.

 Expertise Online : Transmitting clinical images over great distances in a matter of minutes, Telemedicine lets healthcare specialists pay "electronic house calls" and share information with doctors and clinics in the most remote areas. One of the first healthcare systems to go online in the U.S., the Oklahoma Telemedicine Network lets doctors in small rural hospitals send X-rays to radiologists in major medical centers for joint consultation. The result is fast, expert diagnoses via a 3Com network and reduced travel time for patients.

High-Speed Research : SuperJANET, the U.K.'s high-speed national network, links its country's leading universities and research laboratories in a rich knowledge database. Developed by the academic community in collaboration with British Telecom, 3Com, and others, SuperJANET supports a wide range of applications that require the rapid transfer of large amounts of information. When completed, SuperJANET will be able to send the complete works of Shakespeare from one point to another in just half a second. Today, Cambridge University and Imperial College in London are working jointly via SuperJANET on new pharmaceutical and molecular modeling research and development. When the information superhighway works to enhance individual lives, it will work for business and for society at large.

Long-Distance Learning : The information superhighway is bringing the best schools, teachers, and courses to students, regardless of location. These students are collaborating with classmates around the globe, accessing the wealth of online libraries, and making electronic field trips virtually anywhere in the world.

21st Century Classroom : Believing that students are playing a significant role in the global transformation into an information society, 3Com today supplies a complete range of networking solutions for elementary, secondary, and university education environments worldwide. As part of this effort to integrate technology into education, 3Com has helped install a network for the 21st Century classroom at the Edenvale Elementary School in San Jose, California. The network connects Edenvale students with a whole world of information resources, ending classroom isolation. Recently, these students worked on a National Geographic project to measure acid rain, sharing real-world data with students from around the world. "It is an Administration goal that, by the year 2000, all of the classrooms, libraries, hospitals, and clinics in the United States will be connected to the NII." Al Gore, Vice President of the United States . The pathways on which information travels and the tools used to send and receive it are as vital as the information itself. Rapid advances in transmission technologies and networking devices are opening ever faster routes to critical information resources. The imperative, the technologies, and the people to make the information superhighway a worldwide reality exist today. With compelling benefits awaiting early adopters, there really is no reason to wait.

Harbinger of the Future : Successfully making the transition from a university research tool to a fully commercialized medium, the Internet gives us a fascinating preview of what tomorrow's information superhighway will be like. Currently consisting of 45,000 networks worldwide connecting an estimated 30 million people, the Internet is growing at an astounding rate. One industry source predicts the Internet user population will exceed 100 million by 1998. Developed in Europe, the World Wide Web (WWW) offers a vibrant window onto Internet content, with useful information and daily updates. In 1992, the volume of data moving over the Web was 500 megabytes. Just two years later, data volume was twenty times that in a single day. Tomorrow's explosive growth will come from next-generation applications, creating truly global communication capability and entrepreneurial business opportunity. Increasingly faster lanes on the information superhighway will create ever more dynamic destinations down the road.

Careful Construction The convergence of telecommunications, computing, and real-time multimedia technologies into a single digital transmission industry makes today's advanced, interactive information networks possible. With computer speeds expected to rise 100 fold and transmission bandwidth increasing 1,000 fold in the near future, there are even more massive changes to come. As information networks grow in power and scope, it is imperative that they remain open and easy for all to use. Global standards committees and organizations such as the cross-functional industry working team (XIWT) and the Internet Engineering Task Force (IETF) are working to ensure access, security, and reliability for the World.

-- Saumitra [courtesy 3Com]

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