Comparison of signal processing techniques for satellite telephony

In satellite telephony, signals can be processed in many different ways to reduce terrestrial equipment complexity and to conserve required satellite transmitter power and RF bandwidth. This can be accomplished by selecting the proper subsystem design in terms of multiplexing, coding, modulation, error control, and multiple-access techniques. In the present Intelsat operational system, most of the multichannel telephone traffic is handled by FDM/FM/FDMA. This situation will probably change with time since future satellite communications systems must match changing traffic demands, terrestrial interfaces, types of services offered, and frequency spectrum and orbital slots available. In the present paper, some preliminary results of an advanced modulation study performed for Intelsat are discussed. A system model is discussed, along with some potential systems based on this model. The bandwidth and power requirements of these systems are determined and the results tabulated. Several attractive options which could potentially improve the present operational satellite capacity are examined.