Multiuser Satellite Communications

Point-to-point communications occur between a single transmitter and a single receiver. In this chapter, we focus on multiuser communications, that occur between a network of fixed and/or mobile users and a common network center probably having access to a wireline network infrastructure. Multiuser communications in a satellite scenario usually refer to a star topology consisting of one or more gateways and a large number of small user terminals. Gateways communicate with the user terminals through the forward link and terminals may communicate with the Gateways through the return link, both links having a multiuser uplink channel and a multiuser downlink channel. Broadly speaking multiuser communications may refer either to a one-way communication as radio or TV broadcasting or to a two-way multiuser communication where each user is interested in a message specific to herself. In general, multiuser communications usually refer to the latter case.