Spread Spectrum and Time Division Multiple Access Satellite Communications

Although time division multiple access (TDMA) satellite communication provides the highest traffic capacity per satellite and offers efficient transmission of a wide variety of services, it suffers from network timing and ranging requirements and message security. On the other hand, spread spectrum multiple access (SSMA) satellite communication is suited for reliable random access and tactical transmission systems. Orthogonal functions such as Rademacher, Haar, and Walsh, or pseudonoise sequence coding of amplitude and phase of the analog message or code division of baseband signals, frequency and time hopping are among the several methods employed for spread spectrum communications. A combination of TDMA and SSMA can be used for asynchronous and reliable transmission of digital or analog signals.