A Low Pass Filtered-Raised-Cosine Window for UTW-DFTs-OFDM

New waveforms are capable of reducing out-of-band emission (OOBE) and improving spectrum efficiency. Currently, the universal time-domain windowed-DFT-spread OFDM (UTW-DFTs-OFDM) with low PAPR and low complexity has been proposed for an uplink transmission as one of new waveforms. The UTW-DFTs-OFDM can reduce the OOBE drastically by applying time-domain window (e.g., raised-cosine window, RCW) with long transition duration of the window. However, further improvement of the OOBE reduction will be required for the future communication systems such as the beyond 5G. In this paper, we propose a new time-domain window named filtered-RCW (f-RCW). The UTW-DFTs-OFDM using the conventional RCW has a limitation to reduce the OOBE because significant deterioration of communication quality is induced by the long transition duration of the window. In the proposed f-RCW, a low-pass filter (LPF) convolution is executed to the RCW in order to realize high OOBE reduction performance even if the time-domain window with short transition duration is applied. The UTW-DFTs-OFDM using the proposed f-RCW can reduce OOBE by 12 dB compared to the UTW-DFTs-OFDM using the conventional RCW at the channel-edge even in the case of 64QAM.