Non-regenerating processing in next generation satellite communication networks

Onboard Baseband Processing (OBP) in satellite communications can bring great benefits, but it also has two severe drawbacks resulted from signal regeneration, i.e. too high complexity and the channels to be lack of flexibility. Non-regenerative OBP can play similar role as regenerative OBP without the two drawbacks, so that it is popularly used in Wideband Global SATCOM (WGS) systems. The researchers in China also intend to use non-regenerating OBP in the next generation satellite communication network, but how to design the downlink is a vital issue. The downlink in the earlier WGS (wideband gapfiller satellite) system is based on frequency division multiplexing (FDM), which has low power efficiency so as to waste satellite power and weight. The un-demodulated signals essentially belong to continuous waves, so that continuous wave time division multiplexing (CWTDM) should be the best mode for the downlink transmission, but CWTDM technique has not been yet believed to be mature. This paper indicates that there are two CWTDM techniques invented by us, which have been mature for engineering applications and should be a cogent support for non-regenerative OBP. We have succeeded in developing a related system prototype and an FPGA based module, which can prove that the CWTDM technique should be applicable. The paper analyzes the next generation of non-regenerative satellite communication network, and indicates that the CWTDM could play vital role for its development, since it can remarkably raise power efficiency of the downlink without frequency band efficiency lost and increase utility ratio of payload weight.