Acessing the Internet The Net connections can be based on wire-line and wireless access technolgies. Wire-line access Wire-less access copper wires Satellites coaxial cables mobile terrestrial antennas electric power lines fixed terrestrial antennas fiber-optic cables Usually several kinds of network connections are employed at once. Generally speaking, when an E-mail message is sent it travels from the user's computer via copper wires or coaxial cables ISDN lines, etc., to an Internet Service Provider, from there, via fibre-optic cables, to the nearest Internet exchange, and on into a backbone network, tunneling across the continent und diving through submarine fibre-optic cables across the Atlantic to another Internet exchange, from there, via another backbone network and across another regional network to the Internet Service Provider of the supposed message recipient, from there via cables and wires of different bandwidth arriving at its destination, a workstation permanently connected to the Internet. Finally a sound or flashing icon informs your virtual neighbor that a new message has arrived. Satellite communication Although facing competition from fiber-optic cables as cost-effective solutions for broadband data transmission services, the space industry is gaining increasing importance in global communications. As computing, telephony, and audiovisual technologies converge, new wireless technologies are rapidly deployed occupying an increasing market share and accelerating the construction of high-speed networks. Privatization of satellite communication Until recently transnational satellite communication was provided exclusively by intergovernmental organizations as Intelsat, Intersputnik and Inmarsat. Scheduled privatization of intergovernmental satellite consortia: Satellite consortia Year of foundation Members Scheduled date for privatization Intelsat 1964 200 nations under the leadership of the USA 2001 Intersputnik 1971 23 nations under the leadership of Russia ? Inmarsat 1979 158 nations (all members of the International Maritime Organization) privatized since 1999 Eutelsat 1985 Nearly 50 European nations 2001 When Intelsat began to accumulate losses because of management failures and the increasing market share of fiber-optic cables, this organizational scheme came under attack. Lead by the USA, the Western industrialized countries successfully pressed for the privatization of all satellite consortia they are members of and for competition by private carriers. As of February 2000, there are 2680 satellites in service. Within the next four years a few hundred will be added by the new private satellite systems. Most of these systems will be so-called Low Earth Orbit satellite systems, which are capable of providing global mobile data services on a high-speed level at low cost. Because of such technological improvements and increasing competition, experts expect satellite-based broadband communication to be as common, cheap, and ubiquitous as satellite TV today within the next five or ten years. Major satellite communication projects Project name Main investors Expected cost Number of satellites Date of service start-up Astrolink Lockheed Martin, TRW, Telespazio, Liberty Media Group US$ 3.6 billion 9 2003 Globalstar 13 investors including Loral Space & Communications, Qualcomm, Hyundai, Alcatel, France Telecom, China Telecom, Daimler Benz and Vodafone/Airtouch US$ 3.26 billion 48 1998 ICO 57 investors including British Telecom, Deutsche Telecom, Inmarsat, TRW and Telefonica US$ 4.5 billion 10 2001 Skybridge 9 investors including Alcatel Space, Loral Space & Communications, Toshiba, Mitsubishi and Sharp US$ 6.7 billion 80 2002 Teledesic Bill Gates, Craig McCaw, Prince Alwaleed Bin Talal Bin Abdul Aziz Alsaud, Abu Dhabi Investment Company US$ 9 billion 288 2004 Source: Analysys Satellite Communications Database

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Bandwidth The bandwidth of a transmitted communications signal is a measure of the range of frequencies the signal occupies. The term is also used in reference to the frequency-response characteristics of a communications receiving system. All transmitted signals, whether analog or digital, have a certain bandwidth. The same is true of receiving systems. Generally speaking, bandwidth is directly proportional to the amount of data transmitted or received per unit time. In a qualitative sense, bandwidth is proportional to the complexity of the data for a given level of system performance. For example, it takes more bandwidth to download a photograph in one second than it takes to download a page of text in one second. Large sound files, computer programs, and animated videos require still more bandwidth for acceptable system performance. Virtual reality (VR) and full-length three-dimensional audio/visual presentations require the most bandwidth of all. In digital systems, bandwidth is data speed in bits per second (bps). Source: Whatis.com

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