Advanced interference reduction in NC-OFDM based Cognitive Radio with Cancellation Carriers

Reduction of the out-of-band (OOB) emission is essential for Cognitive Radio (CR) systems to enable coexistence with licensed (primary) systems operating in the adjacent frequency bands. This paper proposes an algorithm for the Non Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM)-based CR, to reduce the interference caused by both OOB radiation and by non-ideal frequency selectivity of a primary user (PU) receiver. It is based on a concept to use a set of subcarriers called Cancellation Carriers (CCs). By being aware of the PU´s carrier frequency, the observed interference power can by decreased by about 10 dB in comparison with the standard OOB-power minimizing algorithms.