a satellite communications system , which is inherently power limited , employing spread spectrum techniques in order to trade - off bandwidth for small ground station antennas . in a one - way system embodiment a central station transmits data to a satellite for relay to a large number of small antenna receiving stations , the transmissions being spread spectrum encoded with spreading code lengths selected to provide adequate data recovery at the least sensitive station to which the transmissions are directed . spreading codes may also function to address particular stations . in a two - way system embodiment , the central station additionally functions as a terrestrial relay station . a plurality of small antenna transmitting stations , at least one of which may be at the same site as a receiving station , transmit code division multiplexed data via the satellite to the central relay station using sufficiently long and distinct spreading codes as to permit adequate data error rates and to distinguish the transmissions of the various stations . the central relay station reformats the received data for retransmission to the satellite for relay to the receiving stations .