Performance Analysis of Low-Interference N-Continuous OFDM.

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.