PAPR and out-of-band power reduction in OFDM-based cognitive radios

One of the interesting features of cognitive radio (CR) systems is their ability to provide dynamic spectrum access even in the licensed spectral bands; wherein they should be strictly causing no interference to the licensed users or among themselves. Orthogonal frequency-division multiplexing (OFDM) is considered for CR user transmission because of its flexible operation in frequency band switching; but suffers from high peak-to-average power ratio (PAPR). Hence, a transmission method where it can cause minimum interference with lower PAPR is obtained. In this paper, a better method to reduce out-of-band (OOB) power as well as PAPR is modeled by combining spectral precoding which aims at OOB radiation suppression; and PAPR reduction techniques such as selected mapping (SLM) technique and iterative clipping and filtering (ICF). The performance of these methods are discussed in terms of power spectral densities (PSD) and complementary cumulative distribution function (CCDF) of PAPR.