NTT has developed a technique called Direct Spectrum Division Transmission (DSDT) that divides the spectrum of the satellite communications signals into multiple sub-spectra, then makes communications after allocating them to the unused frequency slots of the operating band of the transponder in space, and finally recombines the divided sub-spectra into a single carrier signal.
NTT said it has verified this technique in satellite experiments.
The idea is to attach a “DSDT adapter” to an existing satellite modem. This divides and recombines the spectrum of the signal so that unused frequency resources scattered throughout the operating band of the transponder can be used without affecting existing signals of other users that share the same transponder. In addition, this technique enhances communication security by dividing the signal into multiple sub-spectra in the transmitter and combining the multiple sub-spectra back into the original signal in the receiver.
https://www.ntt.co.jp/news2019/1912e/191211a.html
