Interference control in time-windowed OFDM systems with realistic power amplifiers for cognitive radio applications

In this paper, we investigate the problem of controlling the interference in holes generated inside an orthogonal frequency division multiplexing (OFDM) spectrum, for applications related to cognitive radio (coexistence of narrow-band high-priority signals with broadband OFDM low-priorityx cognitive signals). Due to its simplicity, the time-windowing technique is selected in order to obtain interference reduction in the out-band region and inside the spectral hole. As an added value over the existing literature, we discuss how to choose system parameters (number of guard subcarriers, window type, and extended guard interval duration) in the presence of a nonlinear power amplifier, whose generated interference is of paramount importance in assessing the real gain provided by the OFDM technique.