Discrete Fourier transform-based block transmission for multi-carrier faster-than-Nyquist signalling

Multi-carrier faster-than-Nyquist (MC-FTN) signalling, which is a non-orthogonal data transmission scheme, is broadly viewed as one of the potential candidates for the future high spectral-efficient communications. In this study, a discrete time-frequency packing scheme based on the discrete Fourier transform (DFT) block transmission for MC-FTN signalling (DBT-MC-FTN) is proposed. Firstly, by transforming the blockwise MC-FTN signalling into the frequency domain, an efficient implementation transceiver structure incorporating a bank of DFTs, circular expanding operation, and cyclic shift summation operation is obtained. Thus, flexible packing in both time and frequency domains can be achieved efficiently within a DBT-MC-FTN block. Secondly, to deal with the inter-symbol interference (ISI) introduced by time packing and inter-carrier interference (ICI) introduced by frequency packing in the proposed DBT-MC-FTN scheme, a subcarrier-level equalisation combined with a soft interference cancellation scheme operated in the frequency domain is further proposed to detect the DBT-MC-FTN signals at the receiver. Simulation results show that the proposed DBT-MC-FTN scheme performs close to the corresponding orthogonal system with negligible bit error rate performance loss in the case of moderate ISI and ICI. Additionally, the post-processing signal-to-interference-plus-noise ratio of the proposed scheme is also given in detail.