Single Channel per Carrier Satellite Communication Systems

Until recently commercial satellite communication systems were restricted to the INTELSAT global system operating in a communication mode which assembled baseband signals in frequency-division-multiplex (f.d.m.) and modulated them onto an r.f. carrier via frequency modulation (f.m.). Many such carriers separated in frequency and transmitted simultaneously via the same satellite give rise to the frequency division multiple access (f.d.m.a.) system. In the past few years the increase in traffic demand (mainly for telephony circuits) has had an important impact on satellite communication systems. It has spurred the search for more efficient modulation/multiple access schemes to enable satellites operating in restricted frequency bands to achieve greater capacity. The second major advance has been an end to the global system dominance of satellite systems with a new era of domestic,and regional satellite systems. Already systems are in operation in the U.S.A., Canada and Indonesia viLa dedicated satellites and in Algeria and Brazil via leased INTELSAT transponders. Many other nations iLncluding Europe, Japan, Iran, Afr-ica and the Arab states have advanced plans for domestic and regional services in the next few years.