Filter Design for Suppressing Sidelobe Interference in NC-OFDM System

摘要

OFDM technology plays an important role in multicarrier modulation. Combining with cognitive radio technology, the traditional OFDM transform into NC-OFDM. The two main drawback of the NC-OFDM system are the secondary users' sidelobe interference to primary users and the high PAPR (peak to average power ratio). One way to suppress sidelobe interference of primary users is to design the filter in the time domain and the PTS method can effectively reduce the PAPR of the NC-OFDM system. According to the distribution of subcarriers in NC-OFDM system, this paper proposes a model of secondary user's interference to primary users. The average interference power density is defined for this model, which is used to measure the interference level of different filters applied in NC-OFDM system. After filtering in time domain, it will cause PAPR to pick up. In this paper, we still use the PTS method to suppress PAPR, and can obtain better system performance.