Application of multi-rate sampling techniques in a satellite communications link simulator

British Aerospace (Space Systems) has developed a satellite communications system software simulator which makes extensive use of multi-rate digital signal processing techniques to improve computational efficiency. The simulator model includes the network of ground terminals, the satellite antennas and satellite transponder channel, together with signal generators which explicitly model each user link (called accesses) as transmitted from the ground terminals. Uplink and downlink noise and interference sources are also modelled. The simulator is used to evaluate the performance of digital satellite communications links and applications include FDMA (frequency division multiple access) planning, analysis of spread spectrum systems, power spectrum analysis and performance measurement of individual accesses. The paper describes two of the more important multi-rate structures in the software, namely the signal generator modules and the uplink multiplexer