Spread spectrum multiple access communication experiments via the Japan's Communication Satellite (CS)

Spread spectrum multiple access (SSMA) communication experiments have been conducted for four years using Japan's Communications Satellite (CS) and a spread spectrum random access (SSRA) system. The SSRA system performance was studied by measuring BER characteristics and the initial acquisition time. The degradation of BER characteristics in a satellite link was less than 2 dB as compared with the theoretical value. The time required for initial acquisition was about 30 seconds, and it is concluded that new techniques are needed to reduce this time. Experiments using Forward Error Correcting techniques showed that about 200 users can utilize a transponder simultaneously, confirming that the SSMA system can be applied to small traffic satellite communications systems with many potential users. Cochannel transmission experiments with wideband FM or SCPC signals were successfully performed in the CS link.