TABLE OF CONTENTS Any communications satellite performs the function of a microwave relay in a telecommunications network. The most basic type of relay is the bent-pipe style of satellite, which does not alter the nature of the transmissions between Earth stations. The Earth stations in this case must organize their transmissions to efficiently use the satellite's repeater resources and to allow the various points on the ground to transfer or exchange the required information. That then determines the basic network structure for the particular application. In more advanced repeaters with onboard processing, the satellite performs other network functions such as switching the connections between stations or even modifying the format of transmission to further improve the efficiency of transmission. All that is carried out whether there is a single GEO satellite or a constellation of non-GEO satellites serving the network. From the users' perspective, the specific nature of the space segment may be irrelevant. However, the design, operation, and, more important, the required investment, all depend heavily on the way the architecture is put together.
The first part of this chapter reviews the features and generic arrangements of networks independent of specific uses. This provides a cross-reference with regard to the applications that are reviewed at the end of the chapter. More detail on these applications can be found in our other work [1].
The purpose of this chapter is to introduce readers to satellite communications, so we have taken a nontechnical approach in reviewing the range of network architectures and services.
