Sidelobe suppression using extended active interference cancellation with self-interference constraint for cognitive OFDM system

To improve the spectrum utilization, more and more attention was paid to OFDM based opportunistic spectrum access (OSA) systems in recent years. In this paper, to enable coexistence between a secondary user and a primary user, a novel method called EAIC was proposed for spectral sculpting of OFDM signal effectively. In EAIC, however, the cancellation signals cause self-interferences to OFDM data tones so that the symbol-error-rate (SER) performance was degraded especially in high order modulation such as 64 QAM. In this paper, a new method called EAIC with self-interference constraint (EAIC-IC) is proposed, in which we analyze the interferences caused by cancellation signals, and then formulate an optimization problem to minimize both the total sidelobe power and the self-interferences. Simulation results show that the EAIC-IC method can provide a perfect tradeoff between spectrum notch depth and SER performance via adjusting the value of the constraint parameter.