In non-contiguous orthogonal frequency-division multiplexing (NC-OFDM) based cognitive radio systems

conventional active interference cancellation (AIC) and extended AIC (EAIC) schemes use the same rectangular waveform of the same length for all canceling carriers (CCs)

leading to the limitation of performance improvement of side-lobe suppression or inter-carrier interference (ICI) reduction.In this paper

a novel variable cancellation basis was proposed for side-lobe suppression in NC-OFDM cognitive radio systems based on the observation that CCs in different frequency

have non-uniform attribution for sidelobe suppression.So

CCs are grouped by frequency locations and shaped with different waveforms of different lengths to satisfy good side-lobe suppression performance while reducing ICI at the same time.Numerical results show that

with the proposed CC scheme

NC-OFDM signal's side-lobe can be suppressed to -60 dB with negligible signal-to-noise ratio loss at a symbol error rate of 10

-5

with 64 quadratic-amplitude modulation symbol.