Performance analysis of N-continuous OFDM systems with low-interference signal

N-continuous orthogonal frequency division multiplexing (NC-OFDM) is a promising multi-carrier transmission waveform conceived for improving sidelobe suppression performance. To reduce the severe inband interference in traditional NC-OFDM, we have proposed low-interference signal modeling for NC-OFDM. However, spectral leakage and error may be undesirably increased owing to the limited continuous differentiability of the smooth signal. In this paper, the low-interference scheme is investigated in terms of power spectrum density (PSD) and error performance, under the parameters of the highest derivative order (HDO) and the length of the smooth signal, to prove and quantify its advantages over traditional NC-OFDM. In the context of PSD, sidelobe decay is evaluated upon considering two discontinuous points due to the finite continuity of the smooth signal and its higher-order derivatives. Furthermore, it was shown that the low-interference scheme incurs small signal-to-noise ratio (SNR) loss and bit error rate (BER) for a short length of the smooth signal or a small HDO compared to traditional NC-OFDM. Meanwhile, due to the cyclostationarity loss imposed by the smooth signal, an effective solution is suggested for the time synchronization in a practical system. Based on analyses and simulation results, the tradeoffs between sidelobe suppression and BER are studied.