IEEE COMMUNICATIONS MAGAZINE A Structured Overview of Digital

Part I of a two-part overview of digital communications. A N IMPRESSIVE assortment of communications signal processing techniques has arisen during the past two decades. This two-part paper presents an overview of some of these techniques, particularly as they relate to digital satellite communications. The material is developed in the context of a structure used to trace the processing steps from the information source to the informa-tion sink. Transformations are organized according to functional classes: formatting and source coding, modulation, channel coding, multiplexing and multiple access, frequency spreading, encryption, and synchronization. The paper begins by treating formatting, source coding, modulation, and potential trade-offs for power-limited systems ' and bandwidth-limited systems. Communications via satellites have two unique charac-teristics: the ability to cover the globe with a flexibility tha