Communications satellites: orbiting into the 90s

Engineering advances in satellite communications are discussed. These include sophisticated switchboards, narrow beams, source coding for higher capacity, larger networks, and the use of higher and lower frequency bands and lower orbits. One of the most popular new 14/11-14/12 GHz commercial services has been time-division multiplexing of multiple carriers operating at low to medium bit rates. Multiple-carrier, low-burst-rate TDMA (time-division multiple access), in which several TDMA carriers are shared among ground terminals, is widely used with very small-aperture terminals (VSAT) on the customer's premises. NASA's (US National Aeronautic and Space Administration) ACTS and Italy's Italsat both plan to use signal regeneration at 30/20 GHz. Onboard switching and multiplexing will not only minimize noise and boost power, but also trim the cost of the entire satellite network.<
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