Sidelobe Suppression in NC-OFDM Systems using Phase Shift

High sidelobe power could cause strong interference to primary users in the orthogonal frequency division multiplexing (OFDM) based cognitive radio systems, i. e. non-contiguous (NC) OFDM systems. In this paper, a phase shift method for sidelobe suppression for NC-OFDM systems is proposed and investigated. Instead of multiplying the phase shift sequences with all the active subcarriers, we consider applying these sequences to the subcarriers on the border of cognitive user´s band since they affect the primary users most. Simulation results show that significant gain is achieved in sidelobe suppression and little change is introduced to the peak-to-average power ratio (PAPR) in the proposed algorithm.