Abstract

chapter19

 The telecommunications industry experienced some spectacular failures around the end of the twentieth century and the start of the twenty-first, but few could compare to satellite companies Iridium and Teledesic.

Its original plans called for a network of 840 satellites. This dropped to 288 satellites, then in February 2002 Teledesic announced that it was planning 20 medium Earth orbit (MEO) satellites.

Satellite communications had its beginning in 1962 with AT&T’s launch of its Telstar 1. Orbiting the Earth in about 2 h, Telstar was visible from the Earth station for less than half an hour, as the antennas followed its track across the sky.

 From 1970, it is started satellite station in Mongolia.

 Another application, direct broadcast television, was a long time in coming, but now high-quality TV can be received, even in remote locations. Very small aperture terminal (VSAT) enables users to mount small antennas on rooftops to run a multitude of applications such as point-of-sale, which need low bandwidth facilities distributed over a wide range.

 MEO and LEO satellites have the advantage of low delay, but at the expense of needing more satellites and tracking antennas to provide the same coverage. Satellites fall into three general categories—domestic, regional, and international.

The 4- and 6-GHzC-band frequencies are the most desirable from a transmission standpoint because they are the least susceptible to rain absorption.

The Ku-band of frequencies has come into more general use as the C-band becomes congested.

Ka-band satellites are becoming more attractive as the lower frequencies become congested.

  Satellites communications development of intense, more than giving the probabilities in people life.