Reduction of OFDM Out-of-Band Emissions with a Multi-step Active Interference Cancelation Technique

Adjacent channel interference (ACI) between OFDM signals severely impacts system performance and spectrum efficiency. To eliminate ACI, Active Interference Cancelation (AIC) techniques using additional modulated OFDM sub-carriers can be adopted. This paper describes an AIC technique based on multi-step calculation of clipped canceling symbols. The algorithm has simple implementation and allows to easily control the extra power required for canceling symbols. To avoid bandwidth expansion, non-orthogonal canceling sub-carriers (E-AIC) can be easily incorporated in the procedure. The achievable reduction of the OFDM spectrum tail power has been evaluated analytically and by simulation.