Sidelobe suppression using extended active interference cancellation with self-interference constraint for cognitive OFDM system
Daiming Qu, Zhiqiang Wang, Tao Jiang, Mahmoud Daneshmand · 2009
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.