BER Performance Improvement for M-ary FTN Signals due to Reduction of Analysis Interval of Decision Feedback Detection Algorithm

When dealing with intersymbol interference (ISI) and its effect on the detection of signals transmitted at the rate above the Nyquist limit, in practice we are faced with a complex implementation of receiving devices. In this paper, we are going consider the decision feedback algorithm with reduced analysis interval, which allows to increase the performance of the detector almost without increasing computational complexity. This algorithm has already been used for detection of Faster than Nyquist (FTN) signals with BPSK modulation, but now it is proposed to apply it to QAM modulation. It is shown that this algorithm provides larger energy gains in conditions of more severe ISI. The energy losses relative to the theoretical BER performance are estimated for FTN signals with QAM-4 and QAM-16 transmitted at symbol rate increased by 11% and 25%.