Digital processing for transponding FDMA/TDMA satellites.

摘要

The traditional communication satellite was an analog ('bent pipe') transponder with relatively few uplink and downlink beams and was usually based on a frequency division multiple access (FDMA) format. These analog transponders were insensitive to the modulation used within the FDMA subbands, but were hardwired to a specific FDMA format. Several present and next generation satellite systems have been extended to include FDMA/TDMA (FDMA combined with time division multiple access) signal format, resulting in an increased multiple access capability.; A transponding satellite processor for FDMA signals has been proposed [9] in which the input waveforms are digitized and digitally processed to isolate each FDMA carriers, the samples of which are routed onboard the satellite. The broader class of such digital processors that do not detect or demodulate the FDMA carriers and are therefore insensitive to the modulations used, is studied.; This research identifies and investigates candidate architectures for transponding satellite digital processors for FDMA/TDMA signal formats that provide improved routing, bandwidth reconfigurability, and the extension to new remote processing formats being considered. Bandwidth reconfurabiltiy is the ability of the satellite to, upon command from the satellite controller, reconfigure to support varying numbers and bandwidths of FDMA carriers. Candidate architectures of satellite processors that support bandwidth reconfigurability are proposed and their signal-to distortion (SDR) ratio and complexity (number of computations per second) are studied. The improvement to signal routing performance of such architectures is quantified. Finally, a satellite architecture that reduces some of the computational load of the satellite by performing some of the onboard digital signal processing remotely at the receiver is studied. This architecture results in digital data links on the downlink and crosslink beams. The required data rates and the potential of source coding techniques for this new satellite architecture is studied.