Reduction of out-of-band radiation in OFDM based overlay systems

In orthogonal frequency-division multiplexing (OFDM) based overlay systems the reduction of the out-of-band radiation is one of the most essential topics. In this paper, two approaches are considered: the conventional windowing of the OFDM signal in time domain and the recently presented concept of cancellation carriers (CCs) where CCs are inserted at the borders of the used OFDM spectrum to suppress the sidelobes of the transmit signal. From an exemplary overlay scenario in the very high frequency (VHF) band, requirements on sidelobe suppression are derived. Simulation results show that by combining windowing with the CC concept the out-of-band radiation can be reduced significantly, and thus, enabling a successful coexistence of two systems in the VHF band