  The low-interference N-continuous orthogonal frequency division multiplexing
(NC-OFDM) system [25], [26] is investigated in terms of power spectrum density
(PSD) and bit error rate (BER), to prove and quantify its advantages over
traditional NC-OFDM. The PSD and BER performances of the low-interference
scheme are analyzed and compared under the parameters of the highest derivative
order (HDO) and the length of the smooth signal. In the context of PSD,
different from one discontinuous point per NC-OFDM symbol in [25], the sidelobe
suppression performance is evaluated upon considering two discontinuous points
due to the finite continuity of the smooth signal and its higher-order
derivatives. It was shown that with an increased HDO and an increased length of
the smooth signal, a more rapid sidelobe decaying is achieved, for the
significant continuity improvement of the OFDM signal and its higher-order
derivatives. However, our PSD analysis also shows that if the length of the
smooth signal is set inappropriately, the performance may be degraded, even if
the HDO is large. Furthermore, it was shown in the error performance analysis
that under the assumptions of perfect and imperfect synchronization, the
low-interference scheme incurs small BER performance degradation for a short
length of the smooth signal or a small HDO as opposed to conventional NC-OFDM.
Based on analysis and simulation results, the trade-offs between sidelobe
suppression and BER are studied with the above two parameters.
