Multigigabit Satellite On-Board Signal Processing

Abstract

Satellite communications in the late 1980s and 1990s must provide reliable high-rate communications between very small inexpensive terminals with routing flexibilities approaching today's telephone system. The capabilities needed for successful competition with established and evolving terrestrial communications systems can be provided most efficiently using Satellite On-board Signal Processing. The rapid improvement of high-speed digital technology makes it possible and costeffective to demodulate, process, and remodulate individual data streams with rates approaching a gigabit. System processing capacity of several gigabits (ten in the example described) through a single satellite can be provided. The satellite communications system described provides communications for very small and very large (trunking) users. Independent combinations of FDMA and TDMA are used in the uplink and downlink designs to minimize terminal costs. Signal routing for small users is accomplished by a digital store-and-forward technique which greatly simplified the terminal receiver, compared to satellite-switched TDMA. Different processing techniques are used for very high data rate users, but complete interconnectivity between all users is maintained. This avoids double-hop routing with excessive transmission delays. On-board processing allows use of innovative responses to rain attentuation without requiring expensive, large signal-power margins. Terminal synchronization and timing is greatly simplified without a significant increase in satellite complexity, by integrating the synchronization loops with the downlink communication TDMA burst structure.