Comparison of Prefilter for DDFSE Equalized Fast-Than-Nyquist Signaling

Fast-than-Nyquist (FTN) signaling improves spectrum efficiency (SE) by compressing the symbol interval and is a promising communication scheme. However, high compression rate means serious inter-symbol interference (ISI), so researchers have been exploring various low-complexity and efficient equalization methods. Delayed feedback sequence estimation (DDFSE) achieves a good tradeoff between complexity and equalization effect, and can achieve better equalization effect with a prefilter, but no one has compared which prefilter has the best BER performance for FTN signaling. We proposed a new prefilter based on unbiased maximum signal-to-interference-to-noise ratio (U-SINR) prefilter and mean square whitened matched filter (MS-WMF), and compared it with three other prefilters to find the best prefilter for medium and low time-squeezing factors. The simulation results show that in the vast majority of cases, we recommend MS-WMF, but new prefilter can be used to obtain better equalization effects when the signal-to-noise ratio is high and the time-squeezing factors is low.