Outperforming Conventional OFDM and SEFDM Signals by Means of Using Optimal Spectral Pulses and the M-BCJR Algorithm

Abstract

In the paper, we compared spectral efficiency between OFDM signals, reputed SEFDM signals, and recently proposed RRC-SEFDM and PR-SEFDM signals. The last three are different types of signals with non-orthogonal frequency division multiplexing, i.e. signals with intersymbol interference (ISI). All signals were modulated with QPSK and 16-QAM. For signals with ISI demodulation was performed by the suboptimal M-BCJR algorithm with $M=8$ paths survived at each step. For construction PR-SEFDM signals we used optimal spectral pulses with length $L = 12$ taps. The simulation results were shown that, at first, the maximum gain in spectral efficiency is achieved only with simultaneous introducing ISI and increasing the size of signal constellation. At second, PR-SEFDM signals with optimal spectral pulses provide a significant gain in spectral efficiency with respect to SEFDM signals and RRC-SEFDM signals at fixed energy consumptions and fixed complexity of the demodulation algorithm. Also, for QPSK and 16-QAM, with respect to OFDM signals our proposed PR-SEFDM signals provide up to 27% gain in spectral efficiency by additional expenses up to 0.6 and 1.3 dB respectively.