Precoding for PAPR Reduction and Sidelobe Suppression for NC-OFDM Based Cognitive Radio Systems

The non-contiguous orthogonal frequency division multiplexing (NC-OFDM) based cognitive radio (CR) system has the drawbacks of high sidelobe power and peak-to-average power ratio (PAPR) values. We proposes a precoding scheme to jointly reduce PAPR values in the secondary users (SUs) spectrum band and suppress sidelobes of signals in the primary user (PU) band. First, a precoding matrix according to the chosen pulse shape is established for reducing PAPR values. A systematic procedure is developed, which includes the singular value decomposition (SVD) and reconstruction process to generate the PAPR reduction matrix at the minimum error rate. To maintain the PAPR performance and avoid interferences in PU spectrum band, an algorithm searching the optimum precoding matrix is determined. Finally, with the Matrix for reducing the PAPR value and the sidelob suppression matrix, we reconstruct the precoding matrix such that the PAPR reduction in the SU band and sidelobes suppression performance in the PU band are accomplished concurrently. Simulation results show that our scheme has excellent performance.