Low Complexity Active Interference Cancellation for OFDM Cognitive Radios

In this paper, the avoidance problem in detect and avoid (DAA) technology of an orthogonal frequency division multiplexing (OFDM) based cognitive radio (CR) is addressed. The focus is on reducing the computational complexity of the active interference cancellation (AIC) technique. Three methods are proposed. These methods mainly rely on the properties that: (i) many matrices occurred in AIC depend only on the number of tones to be avoided and are irrelevant to where these tones reside, and (ii) there exists a statistical relation between the tones to be avoided and the auxiliary tones employed to aid nulling the transmitted sidelobes.