A Novel Nyquist Window for OFDM-based Cognitive Radio Systems

Cognitive radio (CR) is one of the important paradigms proposed by FCC for improving the spectrum utilization. To make agile spectrum resources allocation between the primary users (PUs) and the secondary users (SUs), Orthogonal Frequency Division Multiplexing (OFDM) has been taken as one of the potential modulation candidates in the physical layer in CR. This paper presents a mathematical model for measuring the interference in the windowed OFDM systems. Additionally, we introduce a novel optimized Nyquist window approach to decrease the out-of-band radiation, such that the interference to the adjacent non-orthogonal users can be avoided. Both theoretical analysis and numerical results show the performance enhancement of the proposed scheme.