An overview of broadcast channels - Information theory of satellite down link

This paper describes an overview of the theory of broadcast channels which are communication channels having one transmitter and many receivers. The broadcast channels correspond to satellite down-links and are interesting from point of view of the efficient use of spectrum. The basic problem of this theory is to find the set of simultaneously achievable transmission rates. The transmission rates achieved by superposition coding can dominate the rate achieved by time sharing or by frequency multiplexing. This paper reviews the meaning, coding theory, feedback and an example of code of the broadcast channels.