Additive Cancellation Signal Method for Sidelobe Suppression in NC-OFDM Based Cognitive Radio Systems

In this paper, we propose a novel additive cancellation signal (ACS) method for sidelobe suppression in non-contiguous orthogonal frequency division multiplexing (NC-OFDM) based CR systems. The key idea of the proposed method is to dynamically add several additive cancellation symbols on both the primary user (PU) subcarriers and the secondary user (SU) subcarriers, to generate the additive cancellation signals for suppressing the sidelobe power of NC-OFDM signals. Moreover, the ACS method formulates the problem of sidelobe suppression as a quadratically constrained quadratic program (QCQP), and the optimal additive cancellation signal can be obtained by the standard interior-point method. Simulation results show that the proposed ACS method can provide significant sidelobe suppression performance.