N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 9 - Wireless Systems and Technologies                                                                                 Slide 69 of 80                                                                                                    ________________

    Various Satellite Systems

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Many satellite systems orbit the earth.

Teledesic System - A LEO system with 288 satellites. The Teledesic company is backed by Craig McCaw, Bill Gates, AT&T and Boeing. The system is anticipated to provide two-way data services with speed in the M bps range. This system is aimed at providing the wireless Internet services by 2004.
Downlinks operate between 18.8 G Hz and 19.3 G Hz
Uplinks operate between 28.6 and 29.1 G Hz

Iridium System - This system is headed by Motorola. It has 72 satellites (66 active and 6 spare) in low orbit at 780 Km height. It was the first low orbit system to offer telephone services anywhere in the world. It uses FDMA and TDMA for signal multiplexing. The system is dormant at present.
Intersatellite links    23.18 - 23.38 G Hz
Down Link    19.4 - 19.6 G Hz
Up Link        29.1 - 29.3 G Hz

Globalstar - A LEO system with 48 satellites. This system supports voice, low-rate data, messaging and fax.

Spaceway - A MEO system with 20 satellites. It is designed to support two-way high-speed Internet and telephone calls.