Time-domain Turbo Equalization for DVB-RCS2 Satellite Return Link in NTN-TDL Channel

This article models the satellite broadband channel of the second generation return channel satellite for digital video broadcasting (DVB-RCS2) using the Non Terrestrial Network Tapped Delay Line (NTN-TDL) model of the 3rd Generation Partnership Project (3GPP) and modifies the DVB-RCS2 satellite return link. A suitable time-domain turbo equalization structure is presented, and two equalization methods based on minimum mean-square error (MMSE) and maximum-likelihood sequence estimation (MLSE) principles are deduced. Then, to realize the soft output of the MLSE-based turbo equalization, a non-binary soft output Viterbi algorithm (SOVA) suitable for high-order modulation schemes of DVB-RCS2 is given. The simulation results show that for DVB-RCS2 satellite return link in NTN-TDL channel, the MLSE-based turbo equalization has a lower burst error rate, and its performance approximates to the performance in the additional white gaussian noise (AWGN) channel when the code rate is low. When the reference waveforms with higher code rate and shorter burst length, and the performance gap between the MLSE-based turbo equalization and the MMSE-based method is larger.