Introduction

Abstract

Satellite communication networks are now an indispensable part of most major telecommunication systems. Satellites have a unique capability for providing coverage over large geographical areas. The resulting interconnectivity between communication sources provides major advantages in applications such as interconnecting large traffic nodes (e.g. telephone exchanges), provision of end-to-end connections directly to users, mobile communications, television and sound broadcasts directly to the public. The advantages offered have enabled this technology to mature within just three decades. To date, most benefits within the telecommunications area have been achieved for point-to-point communication within the international and domestic systems, direct television broadcasts and mobile communications. In recent years, satellite communication systems have begun to face competition from optical fibre systems for point-to-point communication between large concentrated traffic sources. To retain a competitive edge, it has been necessary to develop various new techniques. Thus the phenomenal growth of satellite technology continues, the major growth now being in those areas where satellites can provide unique advantages. Such applications include service provision directly to customers using small, low-cost earth stations; mobile communication to ships, aircrafts, land vehicles and individuals; and direct-to-public television/sound broadcasts and data distribution/gathering from widely distributed terminals. In many applications, such as video distribution, service-providers are combining the benefits of satellite communications with optical fibre systems to produce the best solution to users’ needs Similarly, systems have emerged which combine the advantages of satellite mobile communication systems with those of terrestrial mobile systems to provide a seamless coverage — terrestrial systems providing service in populated areas and satellite systems in those areas unserved by the terrestrial system. Recent advances in system architecture have permitted the introduction of satellite personal communication services.