Mobile Satellite Communications Handbook, 2nd Edition

Chapter 2Overview of the Technology

2.1 Introduction

This chapter offers an overview of mobile communications satellite technology and an introduction to the general technology of communications satellites. It is divided into five sections: Introduction; Radio frequencies; Orbits; Satellites and earth stations; and Channels, link analysis, and networks. It is important to recognize that this chapter is intended to serve as an introduction to the technology and, therefore, will be of primary value to the nontechnical professional who seeks a basic understanding of mobile satellite communications technologies.

Regardless of the orbit in which they rotate around the earth, communications satellites are fundamentally independent radio receivers and transmitters that are placed, at great cost, in a very remote and hostile location. Such satellites must be linked to at least one station on earth that transmits up to the satellite (i.e., the satellite hosts the receiver) and a second to which the satellite transmits back down (i.e., the satellite hosts the transmitter). We exclude inter-satellite communications for this discussion (to be discussed later), although satellites may operate purely to link with other satellites. At the most basic level, two systems are used in satellite communications: (i) the space segment or the satellite and (ii) the earth segment, or the stations on earth's surface, usually called the earth stations or satellite terminals, the most visible part of ...