Faster-than-Nyquist Signaling Assigning Increased Resources to Parity Bits for Turbo-Coded OFDM

This paper proposes faster-than-Nyquist (FTN) signaling that assigns an increased amount of resources to parity bits in order to decrease the required received signal-to-noise ratio (SNR) that satisfies the target block error rate (BLER) for turbo-coded orthogonal frequency division multiplexing (OFDM). By lowering the turbo coding rate while maintaining the same number of information bits in a channel-code block, the suppression levels of the inter-symbol-interference and inter-subcarrier-interference due to FTN signaling are increased for the minimum mean square error based turbo soft interference canceler. Computer simulation results show that the required received SNR at the BLER of 10−2 for FTN signaling is decreased by approximately 1.4 dB and 1.0 dB compared to that for cyclic prefix (CP) based OFDM for QPSK and 8PSK, respectively. We also show that the effect of the FTN signaling on the decrease in the required received SNR that satisfies the target BLER from the CP based OFDM is not obtained for 16QAM, although the effect is evident for 16PSK.