Data transmission over FDM/FM troposcatter systems

There are more than one hundred troposcatter systems of various sizes in existence all over the world.1 As the transmission of computer data becomes more and more in common and popular demand, such systems are certain to be involved in these services. Two methods are generally used for transmitting data over troposcatter channels: direct transmission and FDM/FM technique. In the latter, the individual data channels are combined into an FDM baseband to frequency or phase modulate a common radio carrier—the same technique used conventionally for the carrier transmission of multiplex telephone channels. In this study, only FDM/FM techniques are investigated as it is of immediate and primary interest. It was found that both theoretically and experimentally, troposcatter systems can support data transmission of various rates from 2.4 to 40.8 kbps for path lengths of nominally from 100 to 400 statute miles in smooth earth geometry with diversity reception, if proper path and equipment parameters were chosen.