Spectrally-efficient differential turbo-coded modulation for multi-gigabit satellite links

Efficient exploitation of the wide bandwidth available in the EHF (extremely high frequency) domain will be a main pillar for the development of future-generation terabit satellite networks. State-of-the-art systems use spectrally-efficient coded modulations, which are based on coherent demodulation that requires the use of complex and expensive analog PLL circuitry, which are vulnerable to high Doppler shifts and phase noise, the latter, being a significant impairment in the W-band. The latest trends in digital communications are to use fully digital receivers. Therefore, we consider a novel modulation method based on differential turbo-coded modulation and A-Posteriori-Probability (APP) channel estimation for application in multi-gigabit W-band satellite links. The proposed scheme utilizes the combination of an outer 2/3 binary parity channel code and differential 8-PSK modulation, similar to a binary repeat-accumulate serial turbo coding. The turbo-demodulator uses a double-spread interleaver and Log-MAP decoding performed on the 8-PSK trellis. Counteracting channel impairments and frequency drifts is primarily accomplished by APP channel estimation which is integrated into the differential demodulator, and consists of a simple smoothing filter. Preliminary results have shown a robust behavior of the system, achieving high link availability.