Sidelobe suppression in OFDM-based spectrum sharing systems using adaptive symbol transition

In this letter, we introduce a new method for orthogonal frequency division multiplexing (OFDM) sidelobe suppression. An extension is added to OFDM symbols that is calculated using optimization methods to minimize adjacent channel interference (ACI) while keeping the extension power at an acceptable level. Using this technique, interference to adjacent signals is reduced significantly at the cost of a small decrease in the useful symbol energy. The proposed method can be used by cognitive radio (CR) systems to shape the spectrum of OFDM signals and to minimize interference to licensed users (LU), or to reduce the size of guard bands used in conventional OFDM systems.